RU2427417C2 - Granular material thermal treatment plant - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention may be used at thermal electric power stations. Proposed plant comprises material receiver, first heat source, first heat exchanger coupled with material receiver, second heat source to generate heat of another type, and second heat exchanger. Material is kept in receiver subjected to heat of first and second heat sources. Heat source means gas or fluid medium with increased heat content resulted from heat recovery at separate process plant.

EFFECT: ruling out pipeline clogging, efficient processing.

20 cl, 4 ex, 4 tbl, 37 dwg

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is a partial continuation of US application No. 11 / 107.152, filed April 15, 2005 with the claim of convention priority for provisional application No. 60 / 618,379, filed October 12, 2004, and is a partial continuation of US application No. 11 / 199,838 "Installation and A Method for Separating and Concentrating Organic and Inorganic Materials ", filed August 8, 2005, which is a partial continuation of US application No. 11 / 107,153, filed April 15, 2005, with the claim of convention priority for US provisional application No. 60 / 618,379, filed 12.10. 2004, and all of these applications p Fully entered by reference in this application.

FIELD OF TECHNOLOGY

The present invention relates to cost-effective installations for heat treatment of granular materials. More specifically, the invention proposes to use a continuous kiln dryer, for example a fluidized bed dryer, to dry such materials at low temperature with atmospheric air to increase their heat content or to be suitable for processing and reducing industrial emissions before the granular material is processed or burned during industrial production. Although such a plant can be used with high technical and economic efficiency in many industries, it is best suited for use in thermal power plants in order to reduce the moisture content in coal before it is burned.

BACKGROUND OF THE INVENTION

As you know, electrical energy is essential for the life of people. It can do everything: from driving machines and mechanisms in factories to pumping water on farms and ensuring the operation of computers in offices, lighting, heating and cooling in many homes.

This electrical energy is generated by large power plants that use the energy of steam or flowing water to rotate the shafts of turbines, which in turn rotate the shafts of electric generators. While some power plants run on flowing water or nuclear energy, about 63% of the world's electricity and about 70% of the electricity in the United States comes from the burning of fossil fuels, such as coal, oil or natural gas. Such fuel is burned in a combustion chamber at a power plant to produce heat used to convert water to steam in a steam generator. Then superheated steam is obtained and fed into giant steam turbines, in which steam pushes the turbine blades to rotate the shaft. The rotating shaft, in turn, rotates the rotor of an electric generator to produce electrical energy.

After the steam passes through the turbine, it enters the condensing unit, where it heats the water circulating through the pipes of the heat exchanger. As the steam cools, it condenses into water, which can then be returned to the steam generator to repeat the process of converting water to steam. At many power plants, the water circulating through the condenser pipes and absorbing the heat of steam is supplied for cooling to the cooling pool with spray or to the cooling tower. Then the chilled water again enters the condenser cooling circuit or is discharged into lakes, rivers or other bodies of water.

Eighty-nine percent of US coal is used as a heat source for power plants. Unlike oil and natural gas, coal reserves in explored deposits are quite large, and its production is profitable.

There are four types of natural coal: anthracite, coal (bituminous) coal, semi-bituminous coal and brown coal (lignite). Although in principle all four types of coals contain carbon, hydrogen, nitrogen, oxygen and sulfur, as well as moisture, the specific content of these elements and moisture in them varies widely. For example, the highest quality anthracite coals may contain about 98 wt.% Carbon, while the worst grades of brown coals (lignite) may contain only 30 wt.% Carbon. At the same time, the moisture content can be lower than 1% in anthracite and bituminous coals and about 25-30 wt.% In semi-bituminous coals, such as the coals of the Powder River basin, and 35-40 wt.% In lignites of North America . For Australia and Russia, moisture levels in lignites can reach 50% and 60%, respectively. Such semi-bituminous and brown coals with a high moisture content have a lower calorific value compared to bituminous and anthracite coals, since less heat is generated during their combustion. In addition, the high moisture content of the fuel affects all aspects of the power plant, including efficiency and the emission of polluting products. A high moisture content leads to a significant decrease in the efficiency of the steam generator and an increase in the specific heat consumption in comparison with higher-quality coals. A high moisture content can also lead to problems in areas such as transportation and handling, fuel crushing, fan performance, and high flue gas exhaust rates.

Therefore, bituminous coals are a type of coal that is most widely used in the production of electric energy due to their wide distribution and relatively high calorific value. However, they also have a fairly high sulfur content. As a result of stricter environmental regulations (e.g., the Clean Air Act of the United States), expensive gas scrubbers have to be installed in chimneys to prevent air pollution with sulfur dioxide (SO ₂ ), nitrogen oxides ( NO _x ), mercury compounds and fly ash resulting from the burning of these coals.

Lesser quality coals, such as semi-bituminous and brown coals, began to attract increased attention as heat sources for thermal power plants due to their low sulfur content. Burning them as fuel can make it easier for power plants to comply with state and federal standards regarding pollution control issues. Also of great importance is the fact that semi-bituminous and brown coals make up most of the proven coal reserves in the western part of the USA. However, the high moisture content in these low-grade coals reduces their calorific value when used as a source of thermal energy. In addition, such a high level of moisture increases the cost of their transportation (unit costs per unit of calorific value). These coals also create problems when they are used, since they crumble and turn into dust when moisture is lost, resulting in difficulties with their transportation and loading and unloading operations.

Although due to problems with air pollution, natural gas and diesel fuel have almost completely replaced coal as a fuel for domestic purposes, however, rising oil and natural gas prices are causing some industries and building services to return to coal as a heat source. Due to the higher calorific value of coal and anthracite, they are generally more preferred for heat production.

Coal is also the main component for the production of coke, which is used in the production of iron and steel. Coal is heated to approximately 2000 ° F in hermetically sealed furnaces in which a lack of oxygen prevents spontaneous combustion of coal. At such a high temperature, part of the solids turns into gases, and the remaining heavy foamy mass of almost pure carbon is coke. Many coke plants are part of steel mills in which coke is burned together with iron ore and limestone to turn ore into blast iron, which is then processed into steel.

Some of the gases generated during the production of coke, when cooled, turn into liquid ammonia and coal tar. With further processing, these residual gases can be converted into light fractions. The resulting ammonia, coal tar and light fractions can be used for the production of medicines, paints and fertilizers. Coal tar in itself can be used for the manufacture of roofing of buildings and for paving roads.

Part of the gas obtained during the coking process does not become liquid. Such coal gas burns as natural gas and can provide heat in the processes for producing coke and steel. The alternative fuel industry has also developed processes for direct gasification of coal without coking. Such gasification processes make it possible to obtain gaseous and liquid substitutes for gasoline and diesel fuel with high calorific value. Thus, there are various beneficial uses of coal in addition to using its inherent ability to produce heat during combustion.

It has long been known in industry that heating coal reduces its moisture content, and therefore drying coal increases its value and calorific value. Drying coal before burning it in steam generators can increase their efficiency.

For drying coal, numerous developed drying devices can be used. For example, US Pat. No. 5,103,743 to Berg discloses a rotary kiln in which wet coal is dried in a space formed by a shell of a rotary kiln and a casing surrounding the shell. The flue gases produced in a rotary kiln are passed together with wet coal through the drying space, so that the heat emitted by the shell surface and the heat of the hot flue gases used together dry the coal. On the other hand, U.S. Patent No. 4,470,878 to Petrovic et al. Discloses a cascade fluidized bed dryer for preheating coal loaded into a coking unit, the coal being heated by indirect heat transfer during the swirling movement of a mixture of coal and steam. The cooling gases used to cool the hot coke produced in a coke oven are fed to successive stages of a cascade fluidized bed dryer for preheating coal.

The elongated slot drying device disclosed in US Pat. No. 4,617,744 to Siddoway et al. Is used to dry a wet atomized material, such as coal. Coal is charged through the top of the slit-like part of the slit dryer and is discharged through the bottom hole, interacting in countercurrent with a drying fluid, which is passed downward in the crevice channel, and then directed upward to interact in countercurrent with descending wet particles. A conveyor located along the bottom of the slit dryer conveys dried coal particles.

A bunker dryer is described in US Pat. No. 5,033,208 to Ohno et al. This device contains two cylinders with an annular space between them. Coal particles are introduced into this annular space, and hot gas is passed through the holes in the inner cylinder, which acts on the coal particles and is discharged through the holes in the outer cylinder.

US Patent No. 4,606,793 issued to Petrorvic et al. Discloses a moving bed dryer for preheating coal fed to a coking oven. Hot gas or off-steam from the coke dry cooling process is fed to a tubular heat exchanger located inside a moving bed dryer.

US Pat. No. 4,444,129 to Ladt discloses a vibrating fluidized bed dryer used to dry coal particles passing through a size 28 sieve. Hot gases from a coal-fired burner enter the dryer. A recuperative separator located between the burner and the vibrating fluidized bed dryer removes ash from the stream of coal particles. Exiting hot gases are also cleaned of small particles of coal, which are then fed for combustion in the burner.

Although all of these drying devices can be used to remove moisture from a granular material, such as coal, they have a relatively complex structure, they have a low heat transfer efficiency, and are generally better suited for the cyclic processing of portions of material than for continuous operation. Therefore, drying machines or fluidized bed reactors are widely used in industry for drying coal. In such dryers, a fluidizing medium is introduced through openings in the lower part of the fluidized bed to separate and lift the coal particles to improve the characteristics of the drying process. The fluidizing medium can be simultaneously a direct heating medium, or a separate secondary heat source can be placed inside the fluidized bed reactor. Coal particles are introduced on one side of the reactor and moved along the length of the bed in a fluidized state. Thus, fluidized bed reactors are a good technical solution for implementing a continuous drying process, and they provide an increased contact surface between each suspended particle and the drying medium. See, for example, US patents: No. 5,537,941, issued by Goldich; No. 5,546,875 issued by Selle et al .; No. 5,832,848 issued by Reynoldson et al .; 5,830,246, 5,830,247 and 5,858,035 issued by Dunlop; No. 5,637,336 issued by KLannenberg et al .; No. 5,471,955 issued by Dietz; No. 4,300,291 issued by Heard et al .; and No. 3,687,431 issued to Parks.

However, many of these traditional drying processes use very high temperatures and pressures. For example, the U.S. Bureau of Mining process is performed at a pressure of 1,500 psig, while the drying process described in US Pat. No. 4,052,168 to Koppelman requires a pressure of 1000-3000 psi. Similarly, US Pat. No. 2,671,968 to Criner describes the use of purge air having a temperature of 538 ° C. Similarly, US Pat. No. 5,145,489 to Dunlop discloses a process for simultaneously improving the performance of coal and oil, with the temperature being maintained at 454-566 ° C. in the reactor used. See also US patents: No. 3,434,932, issued by Mansfield (760 ° C - 872 ° C) and No. 4,571,174, issued by Shelton (≤538 ° C).

The use of such high temperatures for drying or other processing of coal requires large energy expenditures, large capital investments and high operating costs, which can make it economically disadvantageous to use low-grade coal. In addition, the drying process at elevated temperatures creates an additional stream of pollutants that must be processed. Another circumstance complicating the economic situation in this matter is that known coal drying processes were often based on the burning of fossil fuels such as coal, oil or natural gas to provide a heat source used to improve the calorific value of the coal to be dried. See, for example, US Patents: No. 4,533,438 issued by Michael et al .; No. 4,145,489 issued by Dunlop; No. 4,324,544 issued by Blake; No. 4,192,650 issued by Seitzer; No. 4,444,129 issued by Ladt; and No. 5,103,743 issued by Berg. In some cases, this combustible heat source may be coal fines separated and disposed of during the drying of coal. See, for example, US Patents: No. 5,322,530 issued to Merriam et al .; No. 4,280,418 issued by Erhard; and No. 4,240,877 issued by Stahlherm et al.

Therefore, attempts were made to develop coal drying processes that would be carried out at low temperatures. For example, US Patent No. 3,985,516, issued to Johnson, discloses a process for drying low-grade coal, in which a heated inert gas in a fluidized bed with a temperature in the range of 204-260 ° C. is used as a drying means. US Patent No. 4,810,258 issued to Greene discloses the use of an overheated gaseous drying medium for heating coal to a temperature of 300-450 ° F., although a preferred temperature is 455 ° C. and a pressure of 0.541 psi. See also US patents: Nos. 4,436,589 and 4,431,585 issued by Petrovic et al. (200 ° C); No. 4,338,160 issued by Dellessard et al. (250-650 ° C); No. 4,495,710 issued by Ottoson (204-483 ° C); No. 5,527,365 issued by Coleman et al. (150-300 ° C); No. 5,547,549, framed by Fracas (259-316 ° C); No. 5,858,035 issued by Dunlop; and No. 5,904,741 and No. 6,162,265 issued by Dunlop et al. (248-316 ° C.).

Several well-known coal drying processes use even lower temperatures, although the degree of drying of coal in them is provided to a limited extent. For example, US Pat. No. 5,830,247 to Dunlop discloses a process for preparing irreversibly dried coal using a first fluidized bed reactor with a fluidized bed density of 20-40 lb / ft ³ , with coal having a moisture content of 15-30 weight %, oxygen 10-20% and with a particle size of 0-2 inches is exposed to a temperature of 66-149 ° C for 1-5 minutes for simultaneous grinding and drying of coal. Then the coal is fed into a second fluidized bed reactor, in which it is coated with mineral oil and exposed to a temperature of 248-316 ° C for 1-5 minutes for further grinding and drying of the product. Thus, it is clear that this process is not only applied to coals having a relatively low moisture content (namely 15-30%), but also coal particles are only partially dehydrated in the first fluidized bed reactor operating at a temperature of 66-149 ° C. and actual drying takes place in a second fluidized bed reactor that operates at elevated temperatures of 248-316 ° C. of the bed.

Similarly, US Patent No. 6,447,559 issued to Hunt discloses a process for treating coal in an inert gas atmosphere to improve the quality of coal by first heating it to a temperature of 93-122 ° C to remove surface moisture, and then heating it with a gradual increase in temperature in steps of 204-399 ° C, 482-594 ° C, 704-844 ° C and 1093-1316 ° C to remove moisture contained in the pores of coal particles, to obtain coal with a moisture content and volatile components of not more than 2 wt.% And 15 wt.% , respectively. As in the previous case, it is clear that at the initial stage of heating to a temperature of 93-122 ° C, only limited drying of the coal particles is provided.

One of the problems associated with the use of fluidized bed reactors for drying coal is the occurrence of large quantities of small particles entrained in a fluidizing medium. In particular, at high operating temperatures, spontaneous combustion of these particles can occur, resulting in an explosion. Therefore, in many known coal drying processes, inert fluidizing gases that replace air are used to prevent tanning. Nitrogen, carbon dioxide and steam may be used as such an inert gas. See, for example, US patents: No. 3,090,131, issued by Waterman, ml .; No. 4,431,485 issued by Petrovic et al .; No. 4,300,291 and No. 4,236,318 issued by Heard et al .; No. 4,292,742 issued by Ekberg; No. 4,176,011 issued by Knappstein; No. 5,087,269 issued by Cha et al .; No. 4,468,288 issued by Galow et al .; No. 5,327,717 issued by Hauk; No. 6,447,559 issued by Hunt; and No. 5,904,741 issued by Dunlop et al. US Pat. No. 5,527,365 issued to Coleman et al. proposes a method for drying low-grade carbon-containing fuels, such as coal, in a “mild reducing medium,” which is achieved by using inert gaseous lower alkanes such as propane or methane. In some other known processes, several heated fluidizing fluid streams are used, the temperatures of which gradually decrease as the coal passes along the length of the fluidized bed of the reactor to provide the necessary cooling of the coal to prevent explosion. See, for example, US Pat. Nos. 4,571,174 to Shelton; and No. 4,493,157 issued by Wicker.

Another problem that the industry encountered in carrying out coal drying processes is the natural tendency of coal to reabsorb moisture under normal storage conditions after the drying process. Therefore, attempts have been made to coat the surface of the dried coal particles with mineral oil or some other hydrocarbon product to form a barrier that protects against the penetration of moisture into the pores of the coal particles. See, for example, US patents: No. 5,830,246 and No. 5,858,035 issued by Dunlop; No. 3,985,516 issued by Johnson .; and No. 4,705,533 and No. 4,800,015 issued by Simmons.

In order to increase the efficiency of low-grade coal drying processes, waste heat flows are used as an addition to the primary heat source, combusted fuel. See, U.S. Patent No. 5,322,530 to Merriam et al. This is especially true for coking coal production, where hot coke-cooled cooling gas can be reused to heat the drying gas in a heat exchanger. See, for example, US Patents: No. 4,053,364, issued by Poersch; No. 4,308,102 issued by Wagener et al .; No. 4,338,160 issued by Dellessard et al .; No. 4,354,903 issued by Weber et al .; No. 3,800,427 issued by Kemmetmueller; No. 4,533,438 issued by Michael et al .; and No. 4,606,793 and No. 4,431,485 issued by Petrovic et al. Similarly, the flue gases of fluidized bed furnaces were used as an additional heat source for a heat exchanger placed inside a fluidized bed reactor for coal drying. See, for example, US patents: No. 5,537,941, issued by Goldich; and No. 5,327,717 issued by Hauk. US Pat. No. 5,103,743 to Berg discloses a method for drying solid materials, such as wet coal, in a rotary kiln in which the material to be dried is gasified to produce hot gases, which are then used as a heat source for radiation heaters used to dry the material inside the oven. In U.S. Patent No. 4,284,476 to Wagener et al., Flue gases from a metal production plant are passed through hot coke during coke production to cool it, whereby the flue gases are heated and then used to preheat the wet coal feed before converting it to coke.

However, it seems that in none of the known processes the waste heat stream is used as the only heat source for drying coal. Such a stream is used only as an addition to the primary heat source, which remains the burning of fossil fuels, such as coal, oil or natural gas. This is partly due to the relatively high temperatures used to dry the materials in these known drying plants and in the corresponding processes. Thus, the economic efficiency of the drying of coal products continues to be limited by the need to burn fossil fuels to dry fossil fuels (namely coal) in order to increase its calorific value in order to use an industrial installation (for example, a thermal power plant) in a steam generator.

In addition, clogging (clogging) can occur in many known fluidized bed dryers, since larger and denser coal particles settle at the bottom of the unit and make it difficult to create a fluidized bed of the remaining particles. Condensation at the top of the dryer can also cause particles to agglomerate and fall to the bottom, which aggravates the clogging problem. For this reason, many of the known fluidized bed dryers have a vertical design or are in the form of several stages with fluidization fluid inlet streams aimed at creating improved fluidization schemes for coal particles introduced into the drying plant.

It would be desirable to carry out the process in an oven, such as a fluidized bed dryer, at lower temperatures below 300 ° F, which would eliminate the need to suppress spontaneous combustion of coal particles inside the plant. In addition, introducing mechanical means into the fluidized bed dryer to physically separate and remove larger and denser particles of coal from the fluidized bed zone and to eliminate condensation around the particles would eliminate clogging problems that could reduce the efficiency of the dryer. Drying the coal before introducing it into the steam generator furnace should increase the economic efficiency of using low-grade coal, such as semi-bituminous and brown coal. Such low-grade coals could become competitive fuels for thermal power plants in comparison with the traditionally used anthracite and bituminous coals. The economical use of semi-bituminous and brown coals having a low sulfur content, as well as the removal of harmful components from coal that cause environmental pollution, would be highly beneficial from the point of view of environmental protection.

SUMMARY OF THE INVENTION

The invention provides an apparatus for heat treatment or other improvement of the characteristics of granular materials, which is used as one of the main components of the production process of an industrial enterprise and in which clogging is prevented. Such granular materials may include fuels burned in the production processes of industrial enterprises, or raw materials used to produce finished products in the production process. Although this is not so significant, such a heat treatment plant is preferably heated by one or more sources of waste heat available within a working industrial plant. Such waste heat sources may include, but are not limited to, hot condenser cooling water, hot flue or flue gases, waste production steam from a turbine circuit, and other heat-producing production streams. Thus, the installation proposed in the invention provides a more economical heat treatment of the granular material, as a result of which it becomes possible to use low-grade (for example, with high humidity) materials, which otherwise could not compete with traditional materials used in industrial enterprises.

Although the invention can be used in many industries, however, for illustrative purposes, it is described in the application for a traditional coal-fired thermal power plant, where moisture removal from coal in a drying plant is necessary to increase the calorific value of coal and, accordingly, increase the efficiency of the steam generator power plants. Drying coal using the proposed installation can facilitate the use of low-grade coal, for example brown and semi-bituminous. Reducing the moisture content of coal, regardless of whether it is high-grade or low-grade, can also improve performance.

It is worth noting that there is no need to completely dry the coal used as fuel in order to be economically profitable to use it in steam generators of thermal power plants. Instead, using existing sources of waste heat to dry the coal to a sufficient degree, it is possible to significantly increase the efficiency of the steam generator, while maintaining production costs at a level that ensures the profitability of the process. Thus, a real economic gain is ensured for the operator of the power plant. Reducing the moisture level in brown coals is possible from typical 39-60% to 10% and even lower, although the level of 27-32% is preferred. This preferred level is determined by the heat transfer ability of the steam generator.

Although the heat treatment plant proposed in the invention is aimed at using available sources of waste heat, such as exhaust steam from the steam turbine circuit, flue gases emitted by the enterprise, or condenser cooling hot water to reduce the humidity level or for another technological stage, it must be understood that together with the sources of waste heat, a primary source of heat obtained by burning fuel can be used to achieve the desired result most e economical way. In most cases, the heat received from the primary source will be used much less than the waste heat.

The present invention can use fluidized bed and fixed bed dryers, both single-stage and multi-stage, for pre-drying and subsequent cleaning of the material before it is used in the industrial process, although other known types of drying systems can be used. In addition, such a drying process is carried out at a low temperature in an open circuit (without sealing), which allows to reduce production costs for an industrial enterprise. The temperature of the drying process is preferably kept below 300 ° F and more preferably in the range of 200-300 ° F. In accordance with the present invention, a portion of the hot cooling water of the condenser cooling exiting the condenser could be selected and used to preheat the air supplied to the air preheater to obtain a “thermal amplifier” effect.

The heat treatment unit according to the invention also comprises a conveying means, for example a screw auger, placed inside the dryer to move to its side or to remove larger and denser particles (“heavy particles”) of granular material that could otherwise make it difficult maintaining a continuous flow of granular material through a fluidized bed dryer or clogging (clogging) it. Removing such heavy particles can increase the efficiency of the drying unit and can easily be done in the first stage of a multi-stage unit.

The present invention also provides a system for removing fly ash, sulfur, mercury-containing materials and other harmful pollutants from coal using fluidized bed separation and sorting capabilities, as opposed to systems in which pollutants are subsequently removed how coal is burned. Removing such pollutants before burning coal eliminates the possibility of harm to the environment that may be caused by pollutants in the production processes of the enterprise, and the expected benefits include: low emissions of harmful substances, reduction in the amount of coal supplied, reduction in energy consumption by auxiliary equipment of the enterprise, reduction the amount of water used, reducing maintenance costs associated with metal erosion and other factors, lower capital costs associated with the installation of equipment needed to extract these contaminants from the flue gases.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings show the following.

Figure 1 is a simplified diagram illustrating the operation of a thermal power plant in which coal is used as an energy source.

Figure 2 is a diagram of a modernized coal-fired thermal power plant in which flue gases and waste heat flows from a steam turbine are used to increase the efficiency of the steam generator.

Figure 3 is a view of a fluidized bed drying apparatus of the present invention and related equipment for transporting coal and supplying hot air used to create a fluidized bed.

Figure 4 is a diagram of a single-stage fluidized bed dryer in accordance with the present invention.

5 is a plan view of a distribution plate for a fluidized bed dryer in accordance with the present invention.

6 is a plan view of another embodiment of a distribution plate for a fluidized bed dryer in accordance with the present invention.

Figure 7 is a sectional view of the distribution plate along the line 7-7 of figure 6.

Figure 8 is a plan view of the distribution plate shown in Figure 6 containing a screw auger.

Figure 9 is a diagram of a single-stage fluidized bed dryer in accordance with the present invention, which uses a primary heat source for indirect heating of air used to create a fluidized bed and drying coal.

Figure 10 is a diagram of a single-stage fluidized bed dryer in accordance with the present invention, which uses the waste heat of the production process to indirectly heat the air used to create the fluidized bed and to dry the coal.

Figure 11 is a diagram of a single-stage fluidized bed dryer in accordance with the present invention, which uses a combination of waste heat from a production process to heat the air used to create a fluidized bed of coal (indirect heating) and hot condenser cooling water passed through a heat exchanger placed inside a fluid bed dryer for coal drying (direct heating).

Figure 12 is a diagram of a single-stage fluidized-bed dryer in accordance with the present invention, which uses a combination of waste heat from a production process to heat the air used to create a fluidized bed of coal (indirect heating) and hot steam taken from a steam turbine circuit and passed through a heat exchanger located inside a fluidized-bed dryer for coal drying (direct heating).

Figure 13 is a diagram of a single-stage fluidized-bed dryer in accordance with the present invention, which uses the waste heat of the production process both to heat the air used to create the fluidized bed of coal (indirect heating) and to heat the liquid coolant circulating in the heat exchanger, placed inside a fluidized-bed dryer for coal drying (indirect heating).

Figure 14 is a diagram of a single-stage fluidized bed dryer in accordance with the present invention, which uses hot flue gases taken from the chimney of an enterprise furnace both for heating air used to create a fluidized bed of coal (indirect heating) and for heating liquid coolant circulating in a heat exchanger placed inside a fluidized-bed dryer for coal drying (indirect heating).

Figure 15 is a diagram of a two-stage fluidized bed dryer in accordance with the present invention.

Figure 16 is a diagram of a two-stage fluidized bed dryer in accordance with the present invention, which uses the waste heat of production processes of the enterprise to heat the air used to create a fluidized bed of coal in both chambers of the dryer (indirect heating), and hot condenser cooling water, passed through heat exchangers located inside both chambers of a fluidized bed dryer for coal drying (direct heating).

Figure 17 is a side view of a heating coil used inside a fluidized bed of a dryer.

Figure 18 is a sectional view of a heating coil along the line 18-18 of figure 17.

Figure 19 is a side view of an adjustable partition of a first stage of a fluidized bed dryer in accordance with the present invention.

Figure 20 is a side view of an adjustable partition of a second stage of a fluidized bed dryer in accordance with the present invention.

Figure 21 is a side view of a scattering pipe used inside a fluidized bed dryer in accordance with the present invention.

Figure 22 is an end view of a fluidized bed dryer in accordance with the present invention.

Figure 23 is a diagram of one embodiment of a fixed bed dryer.

24 is a diagram of a two-stage fluidized bed dryer in accordance with the present invention, which is integrated in a thermal power plant and in which condenser hot water is used to heat coal in the first stage of the dryer and to heat the air used to create a fluidized bed of coal in both stages drying unit. The condenser cooling water in combination with hot flue gases dries the coal in the second stage of the drying unit.

Figures 25a and 25b are perspective views of a cut-out scrubber used to remove heavy particles from a fluidized bed dryer.

Figure 26 is a perspective view with a cut-out of a scrubber containing a distribution plate for creating a fluidized bed of granular material inside the scrubber.

Figure 27 is a perspective view of another embodiment of a scrubber in accordance with the present invention.

Figure 28 is a plan view of the scrubber shown in Figure 27.

Figure 29 is an enlarged perspective view of part of the scrubber shown in figure 27.

Figure 30 is a graph illustrating the increase in specific heat consumption of the energy block for various values of reducing coal moisture.

Figure 31 is a graph of the magnitude of the higher calorific value of lignite and coal from the Powder River basin for various moisture contents.

Figure 32 is a diagram of an experimental two-stage fluidized bed dryer in accordance with the present invention.

Figures 33-37 are graphs of various operating characteristics of a fluidized bed dryer shown in Figure 32.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention provides an apparatus for heat treatment of granular materials at relatively low temperatures with the prevention of clogging. The installation proposed in the invention provides a more economical drying of the material, as a result of which it becomes possible to use low-grade (for example, with high humidity) materials, which otherwise could not compete with traditional materials used in industrial plants. Using a heat treatment plant can also reduce the levels of pollutants and other harmful components contained in the material before it can be used in the process of an industrial plant.

Although the invention can be used in many industries, however, for illustrative purposes, it is described in the application for a traditional coal-fired thermal power plant, where moisture removal from coal in a drying plant is necessary to increase the calorific value of coal and, accordingly, increase the efficiency of the steam generator power plants. Coal drying using the proposed installation can facilitate the use of low-grade coals, such as brown and semi-bituminous. Reducing the moisture content of coal, regardless of whether it is high-grade or low-grade, can also improve other characteristics. For example, dried coal will reduce the load on the loading and unloading system, on conveyors and on coal grinding devices used in a thermal power plant. Since dried coal is easier to transport, maintenance costs are reduced and the utilization rate of the transportation system is increased. Dried coal is easier to grind because less energy is needed to produce the same particle size of the coal. If the fuel contains less moisture, the amount of moisture removed from the mill is reduced. As a result, the efficiency of coal crushing is improved. In addition, less primary air is required to supply, create a fluidized bed and heat the coal. A decrease in the volume of primary air leads to a decrease in the air flow rate, and as a result, the erosion of coal mills, coal transportation pipelines, coal burners and other related equipment is significantly reduced. As a result, the maintenance costs of coal transportation pipelines and coal grinding mills are reduced, which are very high for brown coal power plants. Also, a reduction in flue gas flows can be obtained, thereby improving the efficiency of the outlet cleaning devices.

It is worth noting that there is no need to completely dry the coal used as fuel in order to be economically profitable to use it in steam generators of thermal power plants. Instead, using the available sources of waste heat to dry the coal to a sufficient degree, it is possible to significantly increase the efficiency of the steam generator while maintaining production costs at a level that ensures the profitability of the process. Thus, a real economic gain is ensured for the operator of the power plant. It is possible to reduce the moisture level in brown coals from a typical 39-60% to 10% or even lower, although 27-32% is preferred. This preferred level is determined by the heat transfer ability of the steam generator.

In the present invention, various sources of waste heat available in the industrial plant are preferably used in various combinations to dry the material without adversely affecting the performance of the plant. A typical thermal power plant has waste heat from various processes that can be used. One possible source is a steam turbine. To dry the coal, steam can be taken from the steam turbine circuit. For many existing turbines, this could lead to a decrease in power output and adversely affect the operation of the turbine stages below the steam extraction point, that is, the feasibility of heat extraction from this source is very problematic. As for the new thermal power plants, the steam turbines in them are designed in such a way that the selection of steam does not degrade the performance of the stage, that is, the turbine circuit of the new power plants is one of the sources of waste heat that can be used to dry coal.

Another possible source of waste heat that can be used to dry coal is flue gases that are emitted by a power plant. Using the residual heat contained in the flue gas to remove moisture from the coal can lower the temperature in the chimney, resulting in reduced draft and increased possibility of condensation of water vapor and sulfuric acid on the pipe walls. This circumstance limits the amount of heat that can be extracted from the flue gases for drying coal, especially for enterprises equipped with water scrubbers, and therefore hot flue gases cannot be used as the sole source of waste heat for the end use in accordance with the present invention.

In the Rankine’s energy cycle, heat is removed from the steam condenser circuit and / or from the cooling tower (cooling tower). The amount of heat discharged from the steam condenser, which is usually used for public heating, is quite large, and its secondary use has minimal impact on the operation of the power plant. Therefore, part of this condenser cooling water leaving the condenser could be diverted and used to dry coal. An engineering analysis shows that when the station is fully loaded, only 2% of the heat leaving the condenser is necessary to reduce the moisture content in coal by 4%. The use of this heat source as the sole source or in combination with other sources of waste heat available at the power plant ensures optimal use of the sources of waste heat without negatively affecting the performance of the station.

Although this invention focuses on the use of available sources of waste heat to remove moisture from coal or for another technological stage, it must be understood that together with sources of waste heat, a primary source of heat obtained by burning fuel can be used to achieve the desired result in the most economical way. In most cases, the amount of heat received from the primary source will be much less than the waste heat used.

The present invention can use fluidized bed and fixed bed dryers, both single-stage and multi-stage, for pre-drying and subsequent cleaning of the material before it is used in an industrial plant, although other known types of drying systems can be used. In addition, such a drying process is carried out at a low temperature in an open circuit (without sealing), which allows to reduce production costs for an industrial enterprise. The temperature of the drying process is preferably kept below 300 ° F and more preferably in the range of 200-300 ° F.

The heat treatment unit proposed in the present invention also provides for the removal of fly ash, sulfur, materials containing mercury, and other harmful pollutants from coal using the capabilities of the fluidized beds for the selection and sorting of materials, in contrast to the systems used in which the pollutants are removed after of how coal is burned. Removal of such pollutants before burning coal eliminates the possibility of causing environmental damage that may be caused by pollutants in the production processes of the enterprise, and the expected benefits include: low emissions of harmful substances, reduction in the amount of coal supplied, reduction of energy consumption by auxiliary equipment of the enterprise, reduction the amount of water used, reducing maintenance costs associated with metal erosion and other factors, lower capital costs associated with the installation of equipment needed to extract these contaminants from the flue gases.

For the purposes of the present invention, the term “granular material” means any incoming granular or powder material, substance, element or ingredient that is a necessary part of the work of an industrial enterprise, in particular combustible fuel (eg coal, biomass, bark, peat, wood waste), bauxite and other ores; and substrates that must be modified or transformed in the technological processes of an industrial enterprise, for example, grain and cereal materials, malt, cocoa.

In the context of the present invention, the term "industrial process" means any burning, consumption, conversion, modification or improvement of a substance to obtain a useful result or end product. Such technological processes can be carried out, for example, in thermal power plants, in factories for the production of coke, cast iron, steel or aluminum, cement, glass, ethyl alcohol, when drying grain or other agricultural materials, in the production of food products and in the production of heat for industrial needs enterprises and for heating buildings. Technological processes of an industrial enterprise also cover other processes for the thermal processing of a product or system, in particular greenhouses, communal heat supply, regeneration processes of amines or other extracting substances used in the destruction of carbon dioxide or organic acids.

In the context of the present invention, the term "coal" means anthracite, bituminous coal, semi-bituminous coal and lignite (brown coal) and peat. The coal of the Powder River basin is separately indicated.

For the purposes of the present invention, the term "quality characteristic" means a distinctive property of a granular material that affects its combustion, consumption, conversion, change or improvement in the technological process of an industrial enterprise, in particular the moisture content, carbon, sulfur, mercury, fly ash, and the formation of SO ₂ and ash, carbon dioxide and mercury oxide during the combustion of the material.

In this application, the term "heat treatment unit" means any device that can be used to expose a product to heat, in particular ovens, dryers, stoves, ovens, incubators, artificial chambers and heaters.

In the context of the present invention, the term “drying unit” means any device that can be used to reduce the moisture content of a granular material by applying heat directly or indirectly, in particular a fluidized bed dryer, a vibrating fluidized bed dryer, a fixed-bed dryer bed, moving bed dryer, multi-stage fluidized bed dryer, elongated slotted dryer, hopper Black oven or dryer. Such dryers may also contain one or more tanks, one or more stages and internal or external heat exchangers.

For the purposes of this application, the term “primary heat source” means the amount of heat generated directly for the primary purpose of performing work on equipment, in particular in a steam generator, turbine, furnace, drying plant, heat exchanger, reactor or distillation column. Examples of such a primary heat source may include, in particular, the heat of the combusting fuel and the production steam exiting directly from the steam generator.

In this application, the term "source of waste heat" means the residual flow of a by-product gaseous or liquid product having an increased heat content resulting from work already carried out by the main heat source in the equipment part in the technological process of an industrial enterprise, and this waste heat is not released but used additionally to perform work in terms of equipment. Examples of such waste heat sources may include, but are not limited to, cooling water flows, condenser cooling water, hot flue or flue gases, waste production steam, for example, from a turbine circuit, heat emitted from operating equipment, such as a compressor, reactor or distillation column .

For the purposes of this application, coal burned in the furnace of a steam generator of a thermal power plant is used as a typical granular material used in the technological process of an industrial enterprise, however it is important to note that any other material whose supply is necessary or useful for the technological process of an industrial enterprise is also covered by this application.

The figure 1 presents a simplified diagram of a thermal power plant 10, in which coal is used to generate electricity. The raw coal stock 12 is contained in the coal hopper 14. Then it is fed from the hopper using a feed device 16 to the coal grinding mill 18, in which it is converted into powder and sprayed using a stream of primary air 20.

The atomized coal particles are then fed to a furnace 25, in which they are burned using a stream of secondary air 30 to produce heat. As a result of the combustion reaction, flue gases 27 are released, which are released into the atmosphere.

This heat source turns the water 31 in the steam generator 32 into steam 33, which is supplied to the steam turbine 34. The steam turbine 34 may consist of a high pressure turbine 36 (HP), a medium pressure turbine 38 (IP) and a low pressure turbine 40 (LP), connected in series. Steam 33 does the work by pushing the blades of the impellers of the turbines mounted on the shaft. The steam pushes the turbine blades and drives the turbine impellers and, accordingly, the shaft. The rotating shaft drives an electric generator 43 that generates electricity 45.

Steam 47 exiting the low pressure turbines 40 is supplied to a condenser 50 in which it is cooled to be converted into water by means of cooling water 52. Most steam condensers are water-cooled, both indoor and outdoor cooling circuits can be used. In the closed-loop circuit of FIG. 1, the latent heat contained in steam 47 will raise the temperature of the cold cooling water 52 so that it leaves the steam condenser already as hot cooling water 54, which is then cooled in the cooling tower 56 and returned as cold cooling water 52. In an open circuit design, the heat transferred by the cooling water is discharged into a cooling water reservoir (for example, a river or a lake). In a closed loop circuit, on the contrary, the heat carried by the cooling water is removed to the cooling tower.

The efficiency of thermal power plant 10, the scheme of which is shown in figure 1, can be improved by extracting and using some flows of waste heat and by-products, as shown in figure 2. Steam generators of thermal power plants that run on fossil fuels are in most cases equipped with air heaters designed for heating the flows of primary and secondary air used in the processes of coal grinding and combustion, respectively. Burned coal is used in a steam generator system (furnace, burner and boiler) to turn water into steam, which is then used to drive steam turbines connected to electric generators. In heat exchangers designed to heat air with steam (SAH), steam taken from a steam turbine is used to preheat the primary and secondary air flows before being heated by the devices. The extraction of steam from the turbine leads to a decrease in the output power of the turbine (and the entire power plant) and reduces the fuel efficiency.

A typical AVR heater may be regenerative (Lyngstrem or Rotemule design) or may have a tubular design. SAH heaters are used to maintain increased air temperature at the inlet of the AVR heater and to protect its cold side from corrosion caused by sulfuric acid deposited on the heat transfer surfaces of the heater and from clogging, which leads to increased flow resistance and increased energy consumption by fans. Higher air temperature at the inlet of the AVR heater leads to an increase in the temperature of the air at its outlet and the temperature of the heat transfer surfaces (heat-conducting channels in regenerative heaters or pipes in tubular heaters) of the cold side of the heater. Higher temperatures reduce the acid deposition zone inside the AVR heater and also reduce their deposition rate.

Thus, within the retrofit system 65, the SAH heater 70 uses a waste steam portion 71 taken from the intermediate steam pressure turbine 38 to preheat the primary air stream 20 and the secondary air stream 30 before they are fed to the coal grinding mill 18 and furnace 26 , respectively. The maximum temperature of the primary air stream 20 and the secondary air stream 30, which can be achieved in the heater SAH 70, is limited by its thermal resistance and the temperature of the selected steam 71 exiting the steam turbine 38.

In addition, the flows of primary air 20 and secondary air 30 are supplied using fans RA 72 (primary air) and FD 74 (secondary air), respectively, in a three-section heater APH 76, in which these air flows are additionally heated using a flue gas stream 27 before they are released into the atmosphere. Thus, the streams of primary air 20 and secondary air 30 having an elevated temperature increase the efficiency of the coal mill 18 and the production of heat in the furnace 25. Further, the stream of water 78 discharged from the condenser 50 can be returned to the steam generator for re-conversion into production steam. The flue gases 27 and the production steam 71 exiting the steam turbine 38 and the water 78 exiting the condenser, which otherwise would simply be emitted, are successfully used to increase the overall efficiency of the thermal power station 65.

As mentioned above, the efficiency of a thermal power plant could be improved even more if the moisture content in coal 12 was reduced before it was fed to furnace 25. Such a preliminary drying process could also ensure the use of low-grade coals, such as semi-bituminous and brown coals, with sufficient economic efficiency.

3 is a diagram of a fluidized bed dryer 100 used to reduce the moisture content of coal 12, although it is clear that any other type of dryer can be used for the purposes of the present invention. In addition, the entire coal drying system may consist of several drying plants connected in series or in parallel to remove moisture from the coal. Such a design, containing several identical drying plants, provides flexibility in operation and maintenance, and since it usually requires less space for placement, coal drying plants can be installed and integrated within the existing equipment of a power plant in series, one after another. This minimizes possible disruption to the normal production processes of a power plant.

The fluidized beds will operate in an open circuit at relatively low temperatures. The heat exchanger installed in the bed will be used with the stationary design of the installation with a fluidized or fixed bed to provide additional heat for drying the coal, as a result of which the size of the equipment can be reduced. In the case of a sufficient heat transfer surface in the fluidized bed of the dryer, the air flow used to create the fluidized bed and to dry the coal can be reduced to a level corresponding to the minimum velocity required to create the fluidized bed. This will reduce the erosion destruction of the drying unit and the rate of removal of material particles from the fluidized bed.

Heat for a heat exchanger placed in a fluidized bed can be delivered directly or indirectly (using an intermediate heat transfer medium). Direct heat supply involves the selection of hot water for cooling the condenser, production steam, hot flue gases, part of the hot air stream used to create the fluidized bed, or other sources of waste heat and passing them through a heat exchanger located in the fluidized bed. Indirect heat supply involves the use of water or another heat carrier that is heated by a stream of hot primary air, hot condenser cooling water, steam taken from the steam turbine circuit, hot flue gases or other sources of waste heat in an external heat exchanger before this heat carrier is supplied to the heat exchanger placed in a fluidized bed.

The fluidized bed can be a single (see figure 3) or divided into several parts, "steps" (see figures 15-16). A fluid bed dryer is a good solution for drying wet coal where it needs to be burned. Several steps can be performed in one tank or in several tanks. The multi-stage design allows you to make the most of the capabilities of fluidized-bed drying plants for mixing, separation and drying. The coal dryer may contain a primary or secondary heat source for drying the coal.

The figure 3 presents a diagram of a drying plant for coal in the form of a drying plant 100 with a fluidized bed and related equipment at the site of an industrial enterprise. Wet coal is stored in the hopper 14, from which through the feed gate 15 it enters the vibrating feeder 16, which transports the coal to a coal-grinding mill 18 for grinding coal. The crushed coal is then passed through a sieve 102 to select (sort) particles that do not exceed 1/4 inch in diameter. Then, particle-sized coal particles are transported by conveyor 104 to the upper zone of a fluidized bed dryer 100 in which a fluidized bed is created using hot air 106 and the coal particles are dried. The dried coal particles are then transported by a lower conveyor 108, a bucket elevator 110, and an upper conveyor 112 to the upper parts of the dried coal bins 114, in which the dried coal is stored before being supplied to the furnace 25 of the steam generator.

The moist air and the fine particles removed by it 120 from the fluidized-bed dryer 100 are supplied to the dust collector 122, in which the fine particles removed are separated from the moist air. The dust collector 122 creates a suction force to draw in moist air and particulate matter. After that, the air purified from small particles is passed through a chimney 126 for subsequent cleaning in the scrubber module (not shown) of pollutants such as sulfur, ash and mercury compounds contained in the air stream.

Figure 4 illustrates an embodiment of a design for creating a coal drying layer in accordance with the present invention, which is a single-stage fluidized bed dryer 150 that contains one tank and which uses a primary heat source. Although there are many different possible designs of a fluidized bed dryer 150, they all contain a reservoir 152 in which coal is treated in a fluidized bed and transported. The reservoir 152 may be a closed gutter container or other suitable structure. The reservoir 152 comprises a distribution plate 154, which is a deck over the bottom of the reservoir, which divides it into a fluidized bed zone 156 and an elevated pressure zone 158 (lower zone). As can be seen in FIG. 5, the distribution plate 154 may be perforated or configured to provide air 160 creating a fluidized bed in the pressure zone 158 of the reservoir 152. Air 160 used to create the fluidized bed is distributed in the zone 158 high pressure and is pumped upward through the openings 155 or valves in the distribution plate 154 under pressure to create a fluidized bed of coal 12 located inside the zone 156 of the fluidized bed.

In the upper part of the reservoir 152 above the fluidized bed, an upper zone 162 is formed. Wet sorted coal 12 is supplied to the bed 156 of the fluidized bed of the dryer 150 through the inlet 164, as shown in figure 4. When the wet sorted coal 12 is treated in the fluidized bed with air 160, the moisture contained in the coal and the emitted small particles of coal are transported to the upper part 162 of the tank 152, and usually exit the tank through the outlet openings 166 located at the top of the drying unit 150 with fluidized bed. Meanwhile, dried coal 168 will be discharged from reservoir 152 via discharge chute 170 for transport via conveyor 172 to a storage bin or to a steam generator furnace. As the coal particles move in the fluidized bed in zone 156 above the distribution plate 154 in the direction of arrow A (see FIG. 4), they will accumulate near the bulkhead 174, which is a vertical wall that crosses the drying unit in width. The height of the partition 174 will determine the maximum thickness of the fluidized bed of coal particles inside the drying unit, because, after the height of the accumulated coal particles exceeds the height of the partition, they pass through the top of the partition and fall into the area of the drying unit 150 adjacent to the discharge chute 170. Design and location inlet 164 and outlet 169 openings for coal, outlet openings 166 for emitted fine particles, the distribution plate 154 and the configuration of the tank 152 can be modified if necessary for best results.

The fluidized bed dryer 150 preferably comprises a rotary air lock 176 connected to a wet coal inlet 164 to provide a seal between the coal feed line and the dryer and at the same time provide wet coal to the fluidized bed 156. The rotary air lock 176 should have a cast iron body with a passage, the walls of which are coated with nickel carbide. The end covers of the airlock should be made of cast iron and their surfaces should be coated with nickel carbide. The rotors of the air lock should be made of cast iron with a closed end, smooth edges and a welded satellite gear. In one embodiment of the invention, the dimensions of the air lock 176 should be selected so as to pass about 115 tons per hour of wet coal, and the corresponding rotor speed at a fill factor of 60% should be about 13 rpm. The airlock comes with a 3 hp gear motor. and a kit for purging the gateway. While the air lock 172 is driven directly by the engine, any additional air lock installed on the additional inlet for loading coal into the drying unit can be driven by a chain drive. It should be noted that a suitable coating, for example, of nickel carbide, is used on the surfaces of cast iron air lock parts that can be damaged by the long-term abrasive action of coal particles. On the surface covered with this material, nothing sticks.

A rotary product air lock 178 is located immediately after the outlet 169 for discharging dried coal 168 as it leaves the fluidized bed dryer. In one of the embodiments of the invention, the rotary air lock 178 should have a cast iron body with a passage, the walls of which are coated with nickel carbide. Similarly, the end caps of the air lock should be made of cast iron, and their surfaces should be coated with nickel carbide. The rotor of the air lock should be made of cast iron with a closed end, smooth edges and a welded satellite gear. The speed of rotation of the air lock should be approximately 19 rpm with a fill factor of 60% in order to ensure the required product flow. The airlock should be equipped with a 2 hp geared motor, chain drive and airlock purge kit.

A distribution plate 154 separates the hot air zone 158 supplied under pressure from the drying chambers 156 and 162 of the dryer. The distribution plate should preferably be made of 3/8 inch thick carbon steel sheet with openings made using a jet of water under a pressure of 50,000 psi (see Figure 5). The distribution plate 154 may be flat and may be positioned horizontally with respect to the fluidized bed dryer 150. The openings 155 should have a diameter of about _^1/8 inch and should be formed from the supply side to the discharge side of the distributor plate in increments of about 1 inch and the distance between the rows of holes _^1/2 inch and should be directed perpendicular to the wafer surface. More preferably, the openings 155 can be made at an angle of about 65 ° to the surface of the distribution plate, so that air 160 supplied through the openings 155 pushes out coal particles inside the fluidized bed zone 156 toward the center of the dryer, away from the side walls. The particles of coal move in the fluidized bed in the direction of arrow B (see figure 5).

Another embodiment of the distribution plate 180 is shown in Figures 6 and 7. In contrast to the above-described plate design having a flat shape, the distribution plate 180 consists of two sections 182 and 184 with openings that have flat parts 182a and 184a, rounded parts 182b and 184b and vertical parts 182c and 184c, respectively. In order to form the distribution plate 180, the two vertical parts 182c and 184c are fastened with bolts 186 and nuts 188. The "flat" parts 182a and 184a of the distribution plate 180 are actually inclined 5 ° in the direction of the middle of the dryer so that facilitate the movement of coal particles in the direction of the central part of the distribution plate. The rounded parts 182b and 184b of the distribution plate together form a semicircular part 190 having about 1 foot in diameter for receiving a screw screw 192 therein, as shown in FIG. 8. Holes 183 and 185 drilled in the parts of the distribution plate 182 and 184, respectively, also performed from the feed side to the discharge side with a pitch of 1 inch and a length of _^1/2 inch between the rows, wherein they are drilled at an angle of 65 ° to the horizontal surface of the dryer. While the flat portions 182a and 184a and vertical portions 182c and 184s sections 182 and 184 of the distributor plate should be made of a carbon steel plate thickness of _^3/8 inch holes, made using a water jet at a pressure of 50,000 psi, wherein the rounded portion 182b and 184b are preferably made of a carbon steel plate thickness of _^1/2 inch to obtain a reinforced construction around the groove 190 of the screw auger. The coal particles move in the fluidized bed in the direction of arrow C (see figure 6).

As the coal particles are processed in the fluidized bed zone 156 of the dryer and moved in the direction of the arrow D along the fluidized bed, the larger and denser particles will naturally fall by gravity into the lower part of the fluidized bed. At the same time, lighter particles of coal and small particles carried out will rise to the upper part of the fluidized bed, since their relative density is less. Typically, such denser, larger sized coal particles will cover the surface of the distribution plate 180 and clog the drilled holes 183 and 185, thereby preventing the flow of hot pressurized air 160 into the dryer to create a fluidized bed of coal particles. In addition, coal particles can accumulate unevenly along the length of the drying unit, thereby hampering the necessary movement of the particle stream from the feed side to the discharge side of the drying unit. Therefore, there is a need to periodically stop the operation of the drying unit 150 to clean the particles of the increased size of the zone 156 of the fluidized bed in order to provide unhindered access to hot air 160 to create a fluidized bed of coal particles and to ensure their unhindered movement along the length of the drying unit. The need for such work is in conflict with the need to ensure continuous operation of the drying unit.

Therefore, in the cylindrical-shaped zone 190, a screw auger 194 is placed, as shown in FIG. 8. This screw auger must have a diameter of 12 inches in order to remove about 11.5 tons / hour of coarse coal particles, and have sufficient torque to so that it can begin to rotate under a 4-foot-thick layer of coal particles. A 3 hp gear motor is used as a drive. with a reduction gear ratio of 10. To ensure a long service life, the screw auger 194 must be made of carbon steel.

The cylindrical groove 190 of the distribution plate 180 and the screw auger 194 should be perpendicular to the longitudinal axis of the dryer. This allows the ribs 196 of the screw auger during operation to capture coarse coal particles along the lower part of the fluidized bed and feed them to one side of the dryer, which prevents clogging of the holes in the distribution plate with these coarse particles and obstructs the length of coal particles fluidized bed dryer.

FIG. 9 is a diagram of a fluidized bed dryer 150, shown in FIG. 4, in which, for simplicity of description, the same reference numbers are used to indicate the same parts of the dryer. External air 160 is supplied by a fan 200 through a heater 202 that uses a combustion source 204. Part of the air 206, which is used to create a fluidized bed of moist sorted coal 12 and which is heated by a heater 202, is directed to zone 156. For the heater 202, any combustion source, such as coal, oil, or natural gas, can be used.

While such heated fluidizing air 206 can be used to heat coal particles 12, which are processed in the fluidized bed zone 156, and to evaporate water from the surface of the particles by convection heat transfer, to provide heat transfer to the coal particles to further improve said heating process and for drying, preferably a heat exchanger 208 is used located inside the fluidized bed. In this case, a primary heat source is created by taking part of the hot air 206 (heated by a heater 202) and supplying it to the heat exchanger 208, which passes through the fluidized bed 156 to heat the coal in order to remove moisture from it. Air 206 exiting the internal heat exchanger 208 is returned to the fan 200 for re-supply for heating to the heater 202. There is some loss of fluidizing air 206 when it directly enters the fluidized air zone 156 through the pressure zone 158. These losses are recovered through the collection of additional external air 160 and its inclusion in the air circuit.

The diagram shown in FIG. 10 illustrates another embodiment of a single-tank single-stage dryer 150 shown in FIG. 4, except that instead of a heater 202, an external heat exchanger 210 is used in which waste production heat 212 from a surrounding industrial plant is used for heating. Since industrial enterprises, like thermal power plants, usually contain sources of waste production heat that would otherwise be emitted into the environment, the technical solution of the present invention enables the efficient use of this waste heat to heat and dry wet coal 12 in a fluidized-bed dryer 150 layer in order to increase the economic efficiency of burning this dried coal. Using a primary heat source, such as coal, oil, or natural gas, as shown in FIG. 9, for drying coal particles is a more expensive solution.

Figure 11 illustrates another embodiment of a single-stage single-tank drying plant 150 similar to that shown in Figure 10, except that the waste production heat 212 is not used as a heat source for both the external 210 and the internal 208 heat exchangers. In this case, a portion of the hot condenser cooling water 222 of the power plant selected for supply as the required heat source is supplied to the internal fluidized bed heat exchanger 208. Thus, in embodiment 220 of a fluidized bed dryer, the circuit of which is shown in FIG. 11, two independent sources of waste heat are used to increase the efficiency of the coal drying process (namely, waste production heat and condenser cooling hot water).

12 is a diagram of another embodiment of a single-stage fluidized bed dryer 230, similar to that shown in FIG. 11, except that instead of hot condenser cooling water, hot production steam 232 is used as a heat source for internal heat exchanger 208, selected from the steam turbine circuit of a thermal power plant. Again, as in the previous embodiment, two different sources of waste heat (waste production heat 212 and hot production steam 232) are used in the fluidized bed dryer 230 to increase the efficiency of the coal drying process.

Another embodiment of a single-stage fluidized bed dryer 240 containing one reservoir with a secondary heat source is shown in FIGS. 13-14. The secondary heat source for the internal fluidized bed heat exchanger 208 is water or other liquid heat carrier 242, which is heated in the external heat exchanger 210 by the air 206 used to create the fluidized bed, condenser cooling hot water 222, production steam 232 taken from the steam circuit turbines, or hot flue gases 248 from the chimney and then fed into the internal heat exchanger 208 using a pump 246, as shown in figure 13. Can also be used any a combination of the above (and other) heat sources.

Figures 15-16 show another design of an open circuit low temperature fluidized bed dryer in accordance with the present invention, which is a multi-stage single-tank dryer 250 in which a primary heat source is used in the internal heat exchanger 208 (cooling hot water 252 condenser from the cooling tower of a power plant). The tank 152 is divided into two stages: a first stage 254 and a second stage 256. Although a two-stage drying unit is illustrated in Figures 15-16, additional stages may be used to provide additional processing. Typically, wet sorted coal 12 enters the first stage 254 of a fluidized bed dryer 250 through an upper zone 162 at an inlet point 164. Wet sorted coal 12 is preheated and partially dried (namely, part of the surface moisture is removed) with condenser cooling hot water 252, which enters the coil of the internal heat exchanger 258 located inside the first stage 254 (direct heating), and circulates in it and leaves it. Wet sorted coal 12 is also heated and treated in a fluidized bed with hot fluidizing air 206. Air 206 is supplied by a fan 200 through a distribution plate 154 of a first stage 254 of a fluidized bed dryer 250 after it is heated by waste production heat 212 in an external heat exchanger 210.

In the first stage 254, a stream of hot fluidizing air 206 is passed through moist sorted coal 12 located on the distribution plate 154 to dry it and to separate the coal particles into fluidizable and non-fluidizable ones. Heavier or denser, non-fluidizable particles are separated and accumulate in the lower part of the fluidized bed on the distribution plate 154. Then, these non-fluidizable particles (“heavy” particles) are discharged from the first stage 254 as Stream 1 (260), as described in more detail in the US patent application filed on the same day as this application, indicating the same co-author and owner as in this application, which is a partial continuation of US patent application No. 11 / 107,153, filed April 15, 2005. ; moreover, both applications are entered by reference in this application. Fluidized bed dryers generally provide the ability to process a bed of non-fluidizable material up to four inches thick that accumulates at the bottom of the fluidized bed. Material that cannot be fluidized can make up to 25% of all coal loaded into the drying plant. This stream 260 may be directed for processing in another enrichment process, or may simply be discarded. The movement of the separated material along the distribution plate 154 to the discharge point of the stream 260 is due to the inclination of the distribution plate 154, as shown in figure 16. Thus, in the first stage 254, materials that are fluidizable and not amenable to fluidization are separated, pre-heated and dried wet sorted coal 12, and a uniform flow of wet sorted coal 12 is provided to the second stage 256 of a fluidized bed dryer 250. Fluidized coal 12 flows from the first stage 254 through the first baffle 262 into the second stage 256 of the drying unit 250. In this second stage of the drying unit 250, the fluidized coal 12 is further heated and dried to the desired final moisture content, with the condenser cooling water 252 entering the coil the internal heat exchanger 264, located in the second stage 256, circulates and leaves it, as a result of which heat is radiated. Coal 12 is also heated, dried and fluidized using hot liquefying air 206, which is pumped by a fan through a distribution plate 154 into the second stage 256 of the drying unit 250 after it is heated by the waste production heat 212 in an external heat exchanger 210.

The dried coal stream flows through a second baffle 266 on the discharge side 169 of the fluidized bed dryer 250, and a stream of fine particles and moist air 166 is discharged through the top of the dryer. The second stage 256 can also be used to further separate fly ash and other impurities from coal 12. The detachable material, indicated in Figure 16 as Streams 2 (268) and 3 (270), will be removed from the second stage 256 through a series of discharge points 268 and 270 located at the bottom of the fluidized bed of the drying unit 250 (or at other suitable points). The number of discharge points can be changed depending on the size and other characteristics of the particles of wet sorted coal 12, in particular on the nature of the harmful impurities, the parameters of the fluidization and the configuration of the fluidized bed. The release of material to the discharge points 260, 268 and 270 can be carried out using the inclined distribution plate 154 shown in FIG. 16, or suitable horizontal distribution plates available on the market can be used. Streams 1, 2 and 3 can either be removed from the process for disposal or for further processing in order to separate harmful impurities.

The fluidizing air stream 206 is cooled and moistened as it passes through the fluidized bed of the drying plant 250 of wet sorted coal 12 contained in the first 254 and second 256 stages of the fluidized bed 156. The amount of moisture that can be removed from coal 12 inside the fluidized bed is limited by the drying ability of the fluidizing air stream 206. Thus, the heat introduced into the fluidized bed 156 by the coils of the internal heat exchangers 258 and 264 increases the drying ability of the air flow 206 and reduces the amount of air that is needed to provide the required level of drying of coal. If the heat transfer surface inside the fluidized bed is of sufficient size, then the flow of drying air 206 can be reduced to a level corresponding to the minimum speed necessary to maintain the particles in suspension. This speed is usually of the order of 0.8 m / s, but in practice higher speeds of the order of 1.4 m / s should be used to ensure that the speed does not fall below the minimum value.

To achieve maximum drying capacity, the fluidizing air stream 206 exits the fluidized bed 156 in a saturated state (i.e., its relative humidity is 100%). To prevent moisture condensation in the upper part 162 of the fluidized bed dryer 250 and in other parts of the equipment downstream, the coal drying unit 250 is designed so that the relative humidity of the exhaust air is less than 100%. In addition, part of the hot fluidizing air 206 may be bypassed by the fluidized bed 156 and further mixed in the upper zone 162 with saturated air to reduce its relative humidity, as described in more detail below. Alternatively, additional heating surfaces may be placed inside the upper zone 162, or heating of the tank shell or other technical means may be used to increase the temperature and reduce the relative humidity of the air 206 exiting the dryer 250 to prevent moisture condensation in the equipment located downstream. The amount of moisture recovered in the dryer is directly proportional to the amount of heat contained in the fluidizing air 206 and the amount of heat emitted by the internal heat exchangers. The more heat that is introduced, the higher the temperature of the fluidized bed and the temperature of the exhaust air, that is, the ability of the air to transport moisture improves, resulting in a decrease in the specific amount of air required to provide a certain level of drying of coal. The power requirements for drying depend on the air flow and pressure drop generated by the fan. The ability to provide additional heat to the fluidized bed depends on the temperature difference between the bed and the heating water, the heat transfer coefficient, and the surface area of the heat exchanger. Therefore, in the case of using waste heat at low temperatures, a larger area of the heat transfer surface is required to supply heat to the process. This in most cases means increasing the thickness of the fluidized bed to provide sufficient volume to accommodate the coils of internal heat exchangers. Thus, the fulfillment of the stated objectives may require accurate adherence to the dimensions and configuration of the design proposed in the invention of a fluidized bed dryer.

The coal streams entering and discharging from the dryer include wet sorted coal 12, a treated coal stream, a fine particle stream 166, and heavy particle streams 260, 268, and 270. For unloading coal particles that are not amenable to fluidization, the drying unit 250 is equipped with a screw screw 194 located in the cylindrical zone 190 of the distribution plate 254 of the first stage, as well as a hopper storage and scrubber for accumulating settled coal particles, as described in more detail below. The specified screw auger and scrubber are described in more detail in the US patent application, which was filed on the same day as this application with the same co-author and owner, and which is a partial continuation of US patent application No. 11 / 107,153, filed April 15, 2005. ; moreover, both applications are entered by reference in this application.

Typical components of a drying plant complex include, but are not limited to: coal supply equipment, a coal storage bin, a fluidized bed dryer, an air supply and heating system, internal heat exchangers, purification devices (dust collector), instrumentation and a control and data acquisition system . In one embodiment of the invention, screw augers are used to feed wet coal into the drying unit and discharge the dried product from it. To control the feed rate and provide an air lock in the channels of coal supply and discharge, blade loaders can be used. The coal hopper load sensors provide the necessary feed rate and the total amount of coal supplied to the drying unit. Instrumentation may include, in particular, thermocouples, pressure sensors, air humidity meters, flow meters and strain gauges.

In a fluidized-bed dryer in the first stage, preheating and separation of non-fluidizable material are carried out. It may have the design of a small high-performance chamber used to separate coal. In the second stage, the coal is dried by evaporation of the moisture contained in it due to the difference in partial pressures of air vapor and coal. In a preferred embodiment, most of the moisture is removed in the second stage.

Tubular heating elements 280 of heat exchangers 258 and 264, located inside the fluidized bed of the drying unit 250, are shown in more detail in figures 17-18. Each tubular heating element, representing two tubes connected by a U-shaped connecting element, is made of carbon steel and connected to a water tank 284, a closed lid and having inlet 286 and outlet 288 flanges and lifting eyes 290. These packages of tubular heating elements Designed to operate at 150 psig and 300 ° F with 150 # ANSI flanges for inlet 286 and outlet 288 water holes. Tubular heating elements 280 are located across the width of the first 254 and second 256 steps of the drying unit, and support plates 292 with lifting eyes that provide lateral support are distributed along the length of the packages of tubular heating elements.

One of the heat exchanger embodiment 258 of the first stage comprises 50 of tubular heating elements 280 having a diameter of 1 _^1/2 inches and constructed of carbon steel Sch 40 SA-214, with ribs having a height equal to _^1/2 inch, Step - _^1/2 inches , thickness - 16, wherein the spiral welded carbon steel fins have a passage of 1 inch horizontally and a 1 _^1/2 inches on the diagonal. Moreover, the heat exchanger 264 of the second stage of the drying installation may consist of one package of long tubular elements or several packages of tubular elements connected in series, depending on the length of the second stage. The heat exchanger 264 of the second stage generally consists of a pipe having an outer diameter of 1-1 _^1/2 inches and a wall thickness of 10 BWG and made from SA-214 carbon steel with ribs having a height equal to ^{a _1/4} - _^1/2 inches step - _^1/2 - _^3/4 inch, thickness - 16, wherein the spiral welded carbon steel fins have a passage of 1 inch horizontally and a 1 _^1/2 inches on the diagonal. In one embodiment, the second stage heat exchanger comprises 110-140 pipes. The total surface area of the stack of tubular elements of the heat exchangers 258 and 264 of the first and second stages, respectively, is approximately 8483 ft ² .

The partition 262 of the first stage is shown in more detail in figure 19. It stretches across the entire width of the fluidized bed dryer 250 between the first 254 and second 256 steps. Since the width of the dryer is 14 feet, the adjustable overflow partition consists of two panels 300 and 302. The partition panels 300 and 302 contain lower sections 301 and 303, respectively, welded to the lower part of the dryer and its side walls, and adjustable upper sections 304 and 305, which can be moved vertically inside the rails located on the side walls, and suspended on chains 308, mounted on a support pipe 310 of square cross section 5 × 5 inches, which runs across the entire width of the drying unit. Using these chains, the upper sections 304, 305 of the adjustable overflow partition panels are moved vertically to control the height of the partition. Alignment of the distribution of fluidized coal particles along the width of the partition is provided by holes 314 in the upper sections of the partition, as a result of which the uniformity of the thickness of the layer of coal particles across the width of the drying unit is maintained. Each partition panel has three openings 315, which are diamond-shaped with a side length of 12 inches. However, other shapes, sizes, and number of holes may be used depending on the characteristics of the fluidized bed of the drying unit 250. As the upper sections of the partition panels move relative to the lower sections, the size of these holes may increase or decrease to provide a certain degree of regulation of the height of the partition .

The partition 266 on the discharge side of the second stage 256 of the drying unit is shown in more detail in Figure 20. As with the first adjustable overflow partition 262, the second adjustable overflow partition 266 consists of two panels 320 and 322 with lower sections 321, 323 welded to the bottom and to the side walls of the dryer. The upper adjustable sections 324, 325 can be moved vertically along the guides located on the side walls of the dryer, and are suspended by the upper edges 328 on chains 332, mounted on a support tube 330 square section 5 × 5 inches, which runs along the entire width of the dryer . As in the previous embodiment, to align the distribution of coal particles along the adjustable overflow baffle, diamond-shaped holes 334 are used, the sides of which are preferably 12 inches long.

As the lower sections of the distribution partition panels, butterfly valves 336 and 338 are used. Butterfly valves are connected to an adjustable overflow partition by means of hinges and are actuated by air cylinders 340 and 342 by means of corresponding connecting elements for opening and closing openings 344 measuring 8 inches by 3 feet available in each panel of an adjustable overflow partition. When the butterfly valves are open, fluidized coal particles in the second stage 256 of the drying plant may fall into the discharge bins 346, from which the dried coal is then discharged from the drying plant. Distributing partitions are made of carbon steel sheet of thickness _^1/2 inch.

The diffusion pipe 350, located in the upper zone 162 of the drying unit 250, helps to maintain air humidity in this zone above the dew point. This is important because the moisture evaporated from the coal particles in the fluidized bed rises in the upper zone of the drying unit, and the humidity in this zone rises. Under certain temperature conditions, the moisture contained in the air will condense and water droplets may fall into the fluidized bed, as a result of which the coal particles will stick together and may interfere with the functioning of the fluidized bed and clog the distribution plate.

The design of the scattering pipe is illustrated in figure 21. It consists of a series of interconnected pipe sections 352, 354, 356 with ends 358 and 360. The end 358 goes into the drying unit, as shown in figure 15. The end 360 of the supply pipe 350 is connected to the duct 362 leaving the pipeline through which hot air is supplied to the two stages of the drying unit to create a fluidized bed. Thus, a portion of the hot air 206 can be supplied to the upper zone of the drying unit via a diffusion pipe 350. The diffuser pipe 350 preferably has a diameter of 20 inches, and there are three rows of holes 364 with a diameter of 1 inch for supplying hot air over the entire width of the fluidized bed dryer 250. The diffusion pipe is preferably located in the upper zone of the drying installation near the side of the first stage, since the bulk of the moisture generated in the drying installation can accumulate here. In addition, some openings in the supply pipe can be made at an angle to direct the supplied air in such a way as to reduce the formation of a layer of coal particles on the walls of the drying unit.

The figure 22 presents a view of a drying installation 250 with a fluidized bed from the loading side. Special attention must be paid to fire extinguishing installations 370. Although the probability of spontaneous combustion of particles of dried coal and coal powder in the fluidized bed is reduced due to the fact that the drying unit is heated to a temperature of not more than 300 ° F, and preferably to 200-300 ° F, there is still a danger of explosion. Therefore, the fire extinguishing installations 370 comprise a water supply system that begins to spray water into the drying installation in the event of an emergency during operation. It consists of pipes with flange connections, at the ends of which there are spray heads. The system is controlled by a control unit with one zone, and the battery of the backup power source of the control unit ensures its operation for 24 hours. Dry contacts provide remote alarm transmission upon detection of an early stage of an explosion developing inside the dryer. To suppress the explosion and create insulating barriers, fire extinguishers are used that have a high discharge rate. Fire extinguishers are pressurized at 500 psig, filled with dry nitrogen and contain a charge of sodium bicarbonate to suppress the explosion. When a starting explosion is detected, the sensors send electrical signals through the control unit to the explosive actuator located at the output of the fire extinguisher. In the fire extinguisher, the membrane ruptures, and an instant discharge of the substance that suppresses the explosion occurs. Two pressure sensors containing diaphragms with low inertia made of stainless steel are used as an explosion detector. When installing pressure sensors, a special mount is used to minimize false alarms. Six 30-liter fire extinguishers are used, three on each side of the dryer, and if triggered, the reagent is fed through a telescopic spray head.

Another type of coal drying apparatus in accordance with the present invention is a one-stage fixed bed dryer in which one tank and a primary or secondary heat source are used. A diagram of one embodiment of such a dryer with a primary heat source is shown in FIG. 23, although other configurations are possible. A fixed bed dryer is a good solution for drying coal, which is intended for sale to other thermal power plants or other industrial enterprises. This is due to lower drying rates and an extended drying process time, which distinguishes fixed bed dryers compared to fluidized bed plants. In addition, there are usually practical restrictions on the use of a fluidized bed dryer if it is not used in an industrial complex, for example, at a field development site. In this case, heat sources such as condenser cooling water or compressor heat, which are used to carry out the drying process, may be absent. In addition, it may be difficult to cheaply obtain the required amount of air to create a fluidized bed.

As can be seen in FIG. 23, the fixed bed dryer 400 has two concentric walls, the outer wall 402 having a generally cylindrical shape, and the inner wall 404 also having a generally cylindrical shape, form an annular space 406 between these walls for passage air flow. A conical structure 408, the diameter of the base of which is smaller than the diameter of the inner wall 404, is located in the lower part of the fixed-bed dryer 400 coaxially with the inner wall 404, forming an annular hole 410 in the floor for unloading the dried coal 412.

Coal (usually, but not necessarily, wet sorted coal 12) enters the dryer 400 through an open top 414. Under gravity, the moist sorted coal 12 moves to the bottom of the dryer 400. An air stream 416 is created by a fan 418 to create a fluidized bed driving cold drying air 420 through an air-water heat exchanger 422. The air 420 is heated using waste heat, as shown in figure 23, when the passage of hot water 424 cooling the condenser, Anna from the condenser cooling circuit (not shown). As with all other embodiments described herein, other sources of waste heat are possible.

The heated fluidizing air 420 enters the lower part of the fixed bed dryer 400 both through the conical structure 408 and through the annular space 406 between the inner 404 and outer 402 walls. Openings or other means are provided in the conical structure 408 and in the inner wall 404 that allow air 416 to pass through the moist sorted coal 12 located in the space defined by the fixed wall of the drying unit 400 of the drying unit 400, as shown in FIG. 23. Air 416 exits to the atmosphere through the open top 414 of the drying unit 400.

The dryer 400 includes a heat exchanger 426 located inside the fluidized bed. For operation of the internal heat exchanger 426, waste heat is used, in this case, the condenser cooling hot water 424. In addition, other sources of waste heat or steam taken from the steam turbine circuit, individually or in combination, can also be used separately or together with the condenser cooling hot water 424. While wet sorted coal 12 is heated in suspension in a fixed bed dryer 400, dried charcoal 412 is moved to the bottom of the dryer, using gravity or mechanical devices on the market, where it is discharged through a discharge ring an opening 410 formed at the bottom of the dryer 400.

The design of the drying apparatus in accordance with the present invention is specifically designed to maximize the use of waste heat streams from various production processes of the enterprise, and the temperature of the coal should not exceed 149 ° C and preferably should be in the range 93-149 ° C. Raw materials, fuel temperature gradients and coolant flows can vary depending on the purpose, properties of the fuel or raw materials and other factors related to the purpose. At temperatures exceeding 149 ° C, usually closer to 205 ° C, oxidative processes begin to occur, and volatile components are released from coal, forming a product stream containing harmful components that must be processed, that is, various problems for production can occur.

Drying units are able to work with waste heat sources having a higher temperature by controlling the temperature of the air supplied to the drying unit at a level not exceeding 149 ° C and supplying this heat to the internal heat exchanger. The multi-stage design of the fluidized-bed dryer provides the creation of temperature zones that can be used to achieve more efficient heat transfer through the use of a countercurrent coolant. The temperature of the coal at the outlet of the drying plant proposed in the invention is relatively low (usually not higher than 60 ° C), that is, such a product is relatively easy to store and process. If for some granular material an elevated or lowered temperature is required, a drying unit operating at elevated or lowered temperatures can be developed.

The necessary moisture level in the output product can be achieved by choosing the appropriate design of the drying unit, its temperature regime and the residence time of the coal inside the fluidized bed. For low-grade coals used as fuel for thermal power plants, in particular for lignites of North America, a moisture reduction of from about 35-40 wt.% To about 10-30 wt.%, And more preferably 27-32 wt.%, Can be obtained. In other regions, such as Australia and Russia, in which the initial moisture level of lignites can reach 50-60%, coal consumers can choose to reduce the humidity level by drying below 27%. For semi-bituminous coals, such a reduction in moisture level may be from about 25-30 wt.% To about 10-30 wt.%, And more preferably 20-25 wt.%. Although the dryers proposed in the present invention, suitably designed, are able, using heat sources having a reduced temperature, to reduce the moisture level of granular materials to 0%, however, in the case of coal used for operation of thermal power plants, this may be optional and will only result in to increase production costs. The development of specialized designs makes it possible to obtain fluidized beds for drying coal with a high level of humidity, which are best suited for the production processes of a particular industrial enterprise.

24 is a diagram of a two-stage fluidized bed two-stage drying plant 502 that is integrated into a thermal power station 500 and in which hot condenser cooling water 504 and hot flue gases 506 are used as sole heat sources in an open loop low-temperature drying process. The original coal 12, which is a lignite having a moisture content of about 35-40 wt.%, Is fed to a sieve 510 to select particles suitable for processing in the process used. Selected pieces of coal 12, the dimensions of which do not exceed 2 inches, more preferably 0.25 inches or less, are transported by conventional means into the coal bin 512. Pieces of coal larger than 0.25 inches are first fed to the mill 514 and then transported into the bunker 512.

Then, the wet sorted coal 12 from the coal hopper is transported by a conveyor system to a fluidized bed dryer 502, in which the total amount of moisture on the surface and inside the pores of the coal particles is reduced to a predetermined level to obtain “dry” coal 516 having an average moisture content of about 28-30 wt.%. This dried coal 516 is transported by conveyor 518 to a bucket elevator 520 and then to the dried coal hopper 522, in which it is stored until the steam generator is fed to the furnace.

The dried coal 516 accumulated in the hopper 522, using known technical means, is fed into a coal grinding mill 524, in which it is converted into dry coal powder 526 before being fed into the blow chamber 528 of the furnace 530. For the purposes of this application, for the coal drying process, the scheme of which is presented figure 24, provides process parameters typical of the "winter conditions" of the state of North Dakota, namely the coal consumption in the furnace of the steam generator, equal to 4 million pounds / hour. When coal 526 is burned in a furnace 530, the generated heat in an amount of up to 6 billion BTU / hour is transferred to water 532 located in the boiler unit 534. Then, the generated steam 536, having an average temperature of about 538 ° C and a pressure of 2520 psig, is first fed to a high pressure turbine, then to an intermediate pressure turbine and finally to a low pressure steam turbine (not shown), leading at least one generator (not shown) to generate electricity. Waste steam leaves the high-pressure turbine, usually at a temperature of 316 ° C and a pressure of 650 psi, and leaves the intermediate-pressure turbine at a temperature of about 287-316 ° C and a pressure of 70 psi.

Waste steam 538 exits the low pressure turbine at a temperature of about 51-55 ° C and a pressure of 1.5 psia, after which it is sent to the condenser 540 for conversion into water. In the condenser 540, cold cooling water 542 circulates, having a temperature of the order of 29 ° C, which is used to remove the latent thermal energy of the exhaust steam 538. During the cooling process, the water 542 heats up and leaves the condenser as hot water 544 at a temperature of about 49 ° C. Then, this condenser cooling hot water 544 is supplied to a cooling tower 546, in which its temperature is lowered again to a value of the order of 29 ° C. to produce cold condenser cooling water, which is again supplied to the condenser 540. After that, the condensed steam from the condenser is again fed to the steam generator 534 for steam conversion 536 rotating steam turbines.

The fluidized bed dryer 502 consists of a first stage 550, which comprises a distribution area of 70 ft ² for receiving coal 12 to be dried, and a larger second stage 552, containing a distribution area of 240 ft ² . These stages of a fluidized bed dryer 502 are provided with internal heat exchangers 554 and 556, respectively, which will be discussed in more detail below.

A condenser cooling hot water portion 504 is withdrawn and passed through a heat exchanger 554 as a primary heat source for the first stage 550 of the drying unit. This part 504 of the condenser cooling hot water in most cases has an average temperature of 49 ° C, and when it circulates in the first-stage internal heat exchanger, about 2.5 million BTU / hour of heat is emitted. The spent condenser cooling hot water 558 leaving the heat exchanger at a temperature of about 37 ° C is returned to the cooling tower, in which it is used to further cool the spent steam of 558 turbines and again becomes the condenser cooling hot water 504.

The condenser cooling hot water portion 504a is passed through an external heat exchanger 560, which is used to heat the glycol-based heat transfer fluid 562 used to heat the ventilation chamber pre-heat exchanger 564. This preliminary heat exchanger 564 of the ventilation chamber raises the temperature of the primary air flow 566 and secondary air 568 from the ambient temperature, which varies during the year, to a temperature of about (-3) - (- 1) ° C (winter conditions). Glycol does not freeze at low temperatures, so the temperature of the primary and secondary air flows will not fall below a minimum temperature of -3 ° C.

Then, the primary air flows 566 and secondary 568 leaving the heat exchanger 564 for pre-heating the ventilation chamber are passed through the main heat exchanger 570 of the ventilation chamber, which is an air-water heat exchanger. A condenser cooling part 504b of hot water 504 is passed through the main heat exchanger 570 of the ventilation chamber as a necessary heat source. The primary 566 and secondary 568 air flows from the main heat exchanger of the ventilation chamber at a temperature of approximately 27-38 ° C, after which they are directed by means of fans RA 572 and FD 574 at temperatures of 60 ° C and 45 ° C, respectively, to an external heater 576 air, which is a three-section rotational regenerative heater.

The use of heat exchangers 564 and 570 of the ventilation chamber for preheating the outdoor air entering the air heater 576 and the hot air flows 580 and cold 566a of the primary air, respectively, provides an increase in the temperature of the heat source used in the external heat exchanger 586 and the liquid coolant stream 588 from about 40 ° C to 94 ° C. This has a positive effect on the flow rate of air 552 used to create the fluidized bed and drying the coal, and on the required surface area of the internal heat exchanger 556. Both one and the other value decrease with increasing temperature of the heating and drying flows.

The primary air portion 566a 566 is taken in front of the external air heater 576 and fed to the mixer 578 at a temperature of about 63 ° F. After mixing with the hotter stream (approximately 306 ° C.) of primary air 380a, air 582 is obtained at a temperature of approximately 86 ° C., which is used to create a fluidized bed in the first 550 and second 552 steps of the fluidized bed dryer 502. To obtain the indicated temperature of 86 ° C. of the air used to create the fluidized bed, approximately 54% of the hot primary air 580a and 46% of the cold primary air 566a are supplied to the mixer 578. Air 582, used to create the fluidized bed, is supplied to the first stage at a speed of about 3.5 ft / s to create a layer of coal particles with a thickness of about 40 inches. Approximately 132,000 lb / h of coal 12 passes through the first stage 550, the coal particles being heated by an internal heat exchanger and hot liquefying air to a temperature of about 33 ° C., resulting in a slight decrease in coal moisture. When the end of the first stage 550 is reached, the coal particles “overflow” through the top of the partition into the second stage 552.

The flue gases 506 exit the steam generator furnace 530 at a temperature of about 440 ° C. This waste heat source is passed through an external air heater 576 as a heat transfer medium. The flue gases exit the external heater at a temperature of approximately 172 ° C and are sent to the chimney through an electrostatic dust collector and scrubber. The flue gases heat the primary 566 and secondary 568 air streams to a temperature of about 403 ° C and 393 ° C, respectively, to produce hot primary air 580 and heated secondary air 582. Heated secondary air 582 is supplied to furnace 530 with a 17% excess of the required amount air to ensure the efficiency of the fuel combustion process and increase the efficiency of the steam generator.

Hot primary air 580, having a temperature of about 403 ° C, is supplied to a coal-grinding mill 524, where it creates an increased pressure for expelling the coal particles into the blasting chamber 528 and then to the furnace 530. Again, preheating the coal particles 526 increases the efficiency of the steam generator and makes it possible to use steam generator and related equipment of smaller sizes.

When burning dried coal, the combustion temperature rises due to a decrease in water vapor, and the heat transfer processes in the furnace 530 are improved. A higher combustion temperature increases the heat flux emitted in the direction of the walls of the furnace 530. Since the moisture content in the exhaust flue gases 506 is reduced, the characteristics of heat radiation by the flame change, which also affects the amount of heat flux emitted in the direction of the walls of the furnace 530. As the temperature rises flame temperature increases the particles of coal ash exiting the furnace 530, which can intensify the processes of clogging and slagging of the furnace. The deposition of slag on the walls of the furnace reduces heat transfer, which leads to an increase in the temperature of the flue gases at the outlet of the furnace. Due to the decrease in the rate of coal supply to the furnace due to the fact that the humidity of the fuel is reduced, the amount of ash entering the steam generator is also reduced. In addition, the erosion of the steam generator 534 by solid particles is reduced and its maintenance is reduced (for example, the removal of soot, which is deposited on the internal surfaces of the boiler).

A portion of the hot primary air stream 580 is supplied to a heat exchanger 586, which heats the heat carrier 588 to a temperature of about 94 ° C, used as a heat source in an internal heat exchanger 556, located in the second stage 552 of the fluidized bed dryer 502. This coolant exits the heat exchanger at a temperature of about 74 ° C, after which it is sent back to the heat exchanger 586 for reheating. As already mentioned, the primary air stream 580a leaving the heat exchanger 586 at a temperature of about 139 ° C is connected to the cold primary air 566a in the mixer 578 to produce an air stream 582 directed to the drying unit 502 to create a fluidized bed. The mixer provides the necessary air temperature used to create the fluidized bed.

The particles of coal fluidized bed, which come from the first stage 550 to the second stage 552 at a temperature of about 33 ° C and with slightly reduced humidity, form a layer with a thickness of about 38-42 inches, which is liquefied by a stream of air 582 and additionally heated by an internal heat exchanger 556. These particles coal takes about 12 minutes to pass the entire length of the second stage 552 of the fluidized bed, after which they are discharged as dry coal 516, having a moisture content of 29.5%, at a temperature of 488 ° C. More importantly, the calorific value of coal 12, which when it enters the first stage of the drying unit 502 is 6200 BTU / lb, increases to 7045 BTU / lb.

The industry calculates a “coefficient X” to evaluate the relative heat transfer efficiency in the air heat exchanger 576 from the flue gases 506 to the primary air 566 and the secondary air 568. It is determined in accordance with the equation:

m _{PA +} FDcp _{pa + FD} (T _out -T _in ) _{PA + FD} = m _{fluecp flue} (T _out -T _in ) _flue ,

where m is the mass flow rate, cf is the specific heat, T _in is the inlet temperature, T _out is the outlet temperature for the corresponding combustion air flows (i.e., primary and secondary air) and flue gases, respectively. Since the product (m · sr) for the combustion air stream (expressed in BTU / hour) is usually only 80% of the corresponding value for the flue gas stream, this means that under normal conditions for a power plant, the temperature drop of the flue gases as they pass through the heat exchanger can only 80% of the temperature increase of the combustion air flow is equal. However, a reduction in accordance with the invention of the moisture content in the coal and, accordingly, in the flue gases generated by the combustion of this coal in the furnace will decrease the mass flow and the specific heat for the flue gas stream 506, while preheating the primary air stream 566 and the secondary air stream 568 using heat exchangers 564 and 570 of the ventilation chamber will increase the mass flow of combustion air. This will lead to an increase in the coefficient X to 100%, which means a significant increase in the efficiency of the steam generator of a thermal power plant. In addition, the design of the coal drying system in strict accordance with the principles of the present invention can further increase the coefficient X up to 112%, as a result of which the operation of the steam generator in the production of electricity becomes even more efficient. Moreover, this significant increase in the coefficient X for the air heat exchanger and the efficiency of the steam generator is achieved through the use of waste heat sources available in the thermal power plant, which, in turn, improves the economic efficiency of the power plant. Other embodiments of a low temperature open loop drying process using a dryer in accordance with the present invention are described in US Patent Application No. 11 / 107,152, filed April 15, 2005, which indicates the same co-author and owner as in this application, and which is incorporated by reference into the present application.

The system in accordance with the present invention has many advantages. The system provides the selection of waste heat from various sources, including from the condenser cooling hot water, hot flue gases, production steam selected from the turbine circuit (the list is not exhaustive), the temperatures of which are acceptable for their use in the drying process. The system can also provide the best use of heat from the condenser cooling hot water by increasing the temperature of the ventilation chamber by 50-100 ° F at low costs, resulting in reduced heat loss, and heat is taken from the primary 580 and secondary 582 air flows leaving the air heater ( ARN). This heat can also be extracted directly from the flue gases by using an air heater heat exchanger. As a result, the ratio of the air flow supplied to the drying plant to the coal flow is substantially reduced, and the size of the drying plant itself is also possible.

The dryer can be designed to use existing fans to supply the air needed to create a fluidized bed by adjusting the pressure difference of the fluidized bed and the performance of the dust collector fan. For fluidized beds can be used in various schemes dust collectors, and some of them are described in this application. In the described embodiments of the invention, a reduction in the use of primary air is achieved, since the use of a drying unit in accordance with the invention reduces the amount of coal needed to heat the steam generator, and therefore less coal grinding mills are needed to grind the coal, thereby reducing the amount of air that must be supplied to mills for supplying air to the drying unit.

The integration of the drying unit into the coal processing system before loading the coal into the bins of the steam generator furnace has the advantage that heated coal is fed into the mills, since the coal leaves the drying unit at elevated temperature. It is expected that reducing the volume of flue gases, the residence time of coal in the fluidized bed, the moisture content in the flue gases and accelerating the purification processes will significantly reduce mercury emissions from the industrial complex.

The advantage of preheating the air supplied to the air heater is to increase the temperature of the heat transfer surfaces on the cold side of the air heater. Higher surface temperatures reduce the rate of acid deposition and, accordingly, reduce the rate of plugging (clogging) and corrosion. This has a positive effect on the consumption of the fan, the performance of the energy block and the general characteristics of its operation. Using the waste heat of the condenser to preheat the air supplied to the air heater instead of the heat extracted from the steam of the turbine leads to an increase in the output power of the turbine and the entire unit and to an improvement in the performance of the power plant. An increase in the temperature of the air at the inlet of the air heater (AVR) leads to a decrease in the rate of leakage of air from it. This is due to a decrease in air density. Reducing the rate of air leakage from the air heater positively affects the suction and discharge power of the fan, as a result of which the amount of maintenance is reduced, the output power of the energy block increases and its performance improves. For thermal power plants with cooling towers, the use of waste heat to preheat the air supplied to the air heater will reduce the heat load on the cooling towers, resulting in reduced water consumption.

Coal drying using the described method will reduce water losses in the steam generator system, as a result of which its efficiency increases. Reducing heat loss in the steam generator system increases its efficiency. In addition, a decrease in the volume of flue gas generated leads to a reduction in emissions of carbon dioxide, sulfur oxides, mercury, particulate matter and nitrogen oxides per megawatt of output power. The erosion of coal supply pipelines is also reduced (for example, erosion of pipes by coal particles and air), the amount of work to turn coal into powder is reduced, the power consumed by auxiliary equipment is reduced, as a result of which the power of the energy block increases, the volumes of ash and deposits in scrubbers decrease, and industrial water consumption (this does not affect water taken from the steam turbine circuit), clogging and corrosion of the cold side of the air heater, as well as pipe erosion are reduced for the release of flue gases, and increases the degree of purification of flue gases. Fluidized bed dryers can also be equipped with scrubbers, devices separating denser particles, which allows the removal of contaminants and the processing of coal before burning it. There are an unlimited number of temperature levels and design patterns that can be used with the present invention for processing other raw materials and fuels.

The combination of an air heater with a scheme for using hot condenser cooling water makes it possible to use a smaller fluidized bed with greater efficiency for drying coal. The fluidized beds of known systems that use production steam from a steam turbine circuit are much larger. In the present invention, separation of materials is used. This improves the drying efficiency. The described processing method can be used with drying plants either with a static (fluidized bed) or with a fixed bed. In a two-stage drying unit, the relative speed difference in the first and second stages can be adjusted. At different stages, different temperature gradients and thermal conditions can be selected to obtain maximum process efficiency. The design of a multi-stage fluidized-bed dryer provides the separation of non-fluidizable material, afterburning and regulation of oxygen content. In the first stage, the area of which in one embodiment of the invention is 20% of the distribution surface area of the drying unit, more mercury and sulfur compounds are removed. Since a two-stage fluidized bed dryer can be smaller, a lower power fan is required in this case, which means significant energy savings. The required fan power during coal drying is a significant economic factor. The dryer in accordance with the present invention can be used in conjunction with a cleaning module. The system also provides sorting to control the NO _x content or introducing carbon to control the mercury content.

The system allows to reduce wear and maintenance of conveyors for transporting coal and crushers for coal, reduce ash levels and reduce erosion. The process of converting coal to powder is facilitated, so that a more complete drying in the coal-grinding mill is ensured, clogging of pipelines is reduced, less primary air is required, and lower primary air flow rates can be used. The power plant's demand for electricity for auxiliary equipment can be reduced, the power of the power plant is increased, the operation of scrubbers is improved, and the level of emission of harmful substances is reduced.

Also, the flow rate of the flue gases 506 exiting the furnace 530 is reduced when burning dry powdered coal 526 as compared to the case of burning wet coal powder. The specific heat of the flue gases 506 is also reduced due to the reduced moisture content in the dried coal powder 526. As a result, the thermal energy of the flue gases 506 is reduced and it becomes possible to use smaller treatment equipment. A reduced flue gas flow rate 506 also results in lower convective heat transfer rates. Therefore, when using dried fuel, despite the increase in the temperature of the flue gases at the outlet of the furnace, less heat will be transferred to the working heat carrier (water or steam, not shown) in the steam generator 534. For steam generators with a constant heat transfer configuration, the temperature of the hot reheated steam (circulating production steam ) can be reduced compared to running on wetter fuel. A certain decrease in the temperature of hot reheated steam can be compensated by increasing the surface area of the heater (reheating, not shown) or changing the operating mode of the steam generator, for example, by changing the angle of the burner, as a result of which the angle of heat supply to the walls of the boiler changes, or through the use of increased levels of redundancy of air. It would be possible to develop a new design of a steam generator for reduced flue gas velocities 506 in a convective gas duct (flue gas exit path inside the furnace) to obtain the required steam temperature under normal operating conditions. This will further reduce the size of the structure and its cost.

When burning dried coal, the power required to operate auxiliary equipment will decrease as a result of a decrease in the capacity of the discharge fans (FD), suction (ID) and primary air (RA) and a decrease in the power of the coal-grinding mill. The combination of a reduction in coal supply, a lower required air flow, and a lower exhaust gas flow rate when burning a dried angle improve the efficiency of the steam generator and the specific heat consumption of the energy block, primarily by reducing losses in the chimney and reducing the consumption of coal-grinding mills and fans. This improvement in performance allows you to increase the capacity of an industrial enterprise on existing equipment. The operation of treatment systems (scrubbers, electrostatic dust collectors and mercury extraction devices), which are installed at the outlet and are usually used in coal-fired power plants, is improved by burning dried coal by reducing the rate of expiration of flue gases and increasing the residence time of gases in the treatment devices.

Burning dried coal also has a positive effect on reducing emissions. The decrease in the required amount of coal supplied can be directly expressed in mass quantities of ash, CO ₂ , SO ₂ and particulate matter. Primary air supply parameters affect the NO _x content. When burning dried coal, the flow of primary air will be less than in the case of burning wet coal. As a result, the NO _x emission rate will be lower since greater flexibility is created at the inlet of the drying plant for the preparation of combustion air.

For power plants equipped with wet scrubbers, mercury emissions resulting from the combustion of drier coal can be reduced due to the lower gas temperature at the outlet of the air heater, which favors the formation of HgO and HgCl ₂ from elemental mercury. These oxidized forms of mercury are soluble in water and therefore can be removed using a scrubber. In addition, the humidity of the flue gases slows down the oxidation of mercury to water-soluble forms. Reducing the moisture content of the fuel leads to a decrease in the moisture content in the flue gases, which will contribute to the oxidation of mercury with the formation of its water-soluble forms. Thus, when burning drier coal, mercury emissions will be lower compared to using wetter coal. The U.S. patent application, which was filed on the same day as this application with the same co-author and owner, and which is a partial continuation of U.S. Patent Application No. 11 / 107,153, filed April 15, 2005, describes in more detail the use of a dryer layer. to remove sulfur, ash, mercury and other harmful components from coal; moreover, the specified application is introduced by reference to this application.

The decrease in moisture content in coal as it moves through this limited part of the system has the following advantages: drier coal is easier to turn into powder, and less energy is required to obtain the same degree of grinding; the outlet temperature rises (the temperature of the coal and the primary air mixture at the mill outlet), and the characteristics of coal transportation through the pipeline (less clogged) through which the coal is fed to the furnace 530 are improved. In addition, less primary air 580 is required to dry and transport the coal. Faster primary air speeds mean less erosion of the 524 coal mill, coal pipelines, burner and auxiliary equipment, which reduces the maintenance costs of pipelines and mills, which are very high for brown coal power plants.

When coal is dried, the temperature in the furnace 530 is higher due to lower water vapor levels, and heat transfer processes are improved. A higher combustion temperature increases the radiation heat flux towards the walls of the furnace 530. Since the moisture content in the exhaust flue gases 506 is reduced, the characteristics of heat radiation by the flame change, which also affects the amount of heat flux radiated towards the walls of the furnace 530. As the temperature of the flame increases the temperature of the coal ash particles exiting the furnace 530 rises, which can intensify the processes of clogging and slagging of the furnace. The deposition of slag on the walls of the furnace reduces heat transfer, which leads to an increase in the temperature of the flue gases at the outlet of the furnace. Due to the decrease in the rate of coal supply to the furnace due to the fact that the humidity of the fuel is reduced, the amount of ash entering the steam generator is also reduced. As a result, erosion of the steam generator 534 by solid particles is reduced and the amount of its maintenance is reduced (for example, the removal of soot, which is deposited on the internal surfaces of the boiler).

Also, when burning dry coal powder 526, the rate of outflow of flue gases 506 leaving the furnace 530 is reduced compared to the case of burning wet coal powder. In the general case, lower flue gas discharge rates create opportunities for using smaller treatment equipment. The specific heat of the flue gases 506 is also reduced due to the reduced moisture content in the dry powder coal 526. As a result, the thermal energy of the flue gases 506 decreases. The reduced flue gas outflow rate 506 also causes a lower convective heat transfer rate. Therefore, when using dried fuel, despite the increase in the temperature of the flue gases at the outlet of the furnace, less heat will be transferred to the working heat carrier (water or steam) in the convective gas duct of the steam generator system.

For economic reasons, complete drying of the coal is not required and is not recommended, since removing only part of the moisture from the fuel is sufficient. The optimal amount of moisture to be removed depends on the operating conditions of the industrial complex, in particular on the type of coal and its characteristics, on the design of the steam generator and economic considerations (for example, selling dried coal to other thermal power plants). The main thing is that there is enough moisture in the coal to provide enough mass flow to transfer heat to the streams of the main and newly heated steam inside the thermal power plant. Otherwise, the steam produced by the steam generator may not be enough to rotate the turbines. Waste heat from production processes is preferably, but not exclusively, used for heating and / or creating a fluidized bed (air 582 for drying, creating a fluidized bed) and for use in an internal heat exchanger. As shown, this heat can be used directly or indirectly in one or more steps.

As discussed above, a screw auger 194 located in a cylindrical trough 190 of the distribution plate 180 of the first stage 254 of a fluidized bed dryer (see figures 7-8 and 15) generally conveys in the horizontal direction denser coal particles that are not amenable to fluidization that fall to the bottom of the layer. Such material can simply be left to accumulate on the fluidized bed side of the drying plant until the plant is stopped to regularly remove such deposits, while still improving the overall process of transporting the flow of fluidized coal particles to the discharge side of the drying plant compared to installations without such a screw auger. However, a preferred embodiment of a fluidized bed dryer comprises a scrubber for automatically removing during the process of operation said accumulated coal particles from the fluidized bed region, in order to reduce the need for such cleaning, which disrupts the operation of the plant. These automatically removed coal particles, not amenable to fluidization, constitute a separate stream of coal, which can be processed depending on the composition and needs of a thermal power plant, in particular, sent to be burned in a steam generator furnace, or processed to separate trapped small particles and remove harmful components such as elemental sulfur, ash or mercury, or sent to landfills.

An embodiment of a scrubber 600 in accordance with the present invention is shown in cutaway in figures 25a and 25b. The scrubber 600 is a box-shaped case with side walls 602, an end wall 604, a base 606 and an upper part 608 (not shown) that is attached to the side wall of the drying unit 250 so as to cover the cut out discharge opening 610 through which the screw screw 194 partially protrudes It should be noted that instead of a screw auger, any suitable device can be used that is capable of transporting coal particles that have descended downward, including a conveyor belt, in a horizontal direction s or drag chain.

The screw auger 194 will move the particles lying in the lower part of the fluidized bed and unload them through the discharge opening 610 into a scrubber 600, where they can accumulate separately from the dryer. In this case, the need to stop the drying unit to remove accumulated heavy particles is eliminated. With sufficient accumulation of particles in the scrubber or in any other case, a door 612 can be opened in the end wall 604 to discharge accumulated particles through an outlet in the end wall, the accumulated particles being pushed out by the pressure generated by the screw screw 194, or by any other known means. Door 613 may be controlled by a timer so that it opens to discharge accumulated particles at regular intervals.

A preferred embodiment of the scrubber 600 is shown in FIG. 26, where a distribution plate 620 is used instead of a solid panel of the base 606 (see FIG. 25). In this case, the branch portion of the air stream 206 creating the fluidized bed passes upward through the openings 622 in the distribution plate 620 for fluidization of particles in the scrubber. Of course, the bulk of the particles will remain in the lower part of the fluidized bed due to their increased specific gravity, however, some of the fine particles removed will rise into the upper part of the layer and be pulled into the drying unit 250 through the inlet 624 (through this hole in figure 26 heat exchanger tubes are visible 280). Thus, the stream of particles discharged into the scrubber shown in FIG. 26 undergoes additional processing to separate the removed small particles and can be sent for further processing, productive use or disposal.

Another embodiment 630 of the scrubber, shown in figures 27-29, contains two sections 632 and 634 for processing more particles that are not amenable to fluidization, discharged from the drying unit 250. In figure 28 it is clearly seen that the screw auger 194 passes through the front chamber 636 Coal particles that have fallen down are fed by a screw screw into this front chamber 636 and then into the storage chambers 638 and 640, closed by shutters 642 and 644, respectively, or other suitable flow control means. As soon as a predetermined volume of heavy particles accumulates in the accumulation chambers 638 and 640 or a predetermined time interval elapses, the gates 642 and 644 open to discharge the accumulated coal into the discharge channels 646 and 648, respectively. The particles of coal under the action of gravity fall through the outlet parts 650 and 652 to the lower parts of the discharge channels 646 and 648 and then to some storage tank or transportation means for further processing or disposal.

As indicated above, distribution plates 654 can be placed inside the accumulation chambers 638 and 640 so that the air stream intended for fluidization passes through the openings and 660 in the distribution plates to separate small particles of coal trapped in the stream of denser particles. Once the gates 642 and 644 open, the discharged fines are lifted to the top of the discharge channels 646 and 648 to be fed by suitable mechanical means back to the fluidized bed dryer 250. Heavier coal particles fall down through the lower portions of discharge channels 646 and 648, as described above.

The shutters 642 and 644 can be rotatably connected to the storage chambers 638 and 640, although they can also be made sliding-opening, rotating upward, turning downward or sideways, or have any other suitable connection design. In addition, several gates can be connected to the storage chambers to increase the rate of discharge of heavy coal particles from the chambers.

The use of heavy particles separated from the dryer 250 using a scrubber 600 will depend on their composition. If they contain acceptable levels of sulfur, ash, mercury and other harmful components, they can be sent to a steam generator furnace for burning, since they have the required calorific value. If the levels of harmful particles in heavy particles are unacceptably high, then these particles can be further processed to remove these harmful components partially or completely, as described in more detail in US patent applications No. 11 / 107.152 and No. 11 / 107.153, filed 15.04. 2005, which indicate the same co-author and co-owner as in this application, and which are incorporated by reference into this application. Only if the levels of harmful constituents contained in heavy particles are so high that it is not economically feasible to further process them to reduce these levels, then this material is sent for disposal. Thus, the scrubber 600 in accordance with the present invention not only provides automatic removal of particles that are not amenable to fluidization from the fluidized bed of the drying plant to increase its efficiency, but also provides the possibility of further processing of these particles and their productive use in a thermal power station or other industrial enterprise.

The following examples are illustrations of a low temperature dryer, which is part of the present invention.

EXAMPLE I - INFLUENCE OF REDUCED HUMIDITY ON INCREASING THE HEAT OF COMBUSTION OF Lignite COAL

Coal burning tests were performed at Power Unit 2 of the Great River Energy Coal Creek Power Station in North Dakota to determine the effect of humidity on the unit's operation. Brown coal was dried for these tests in an open-air coal drying system. The results are shown in figure 30.

As you can see, the average moisture content of coal decreased by 6.1%: from 37.5% to 31.4%. The graph shown in figure 30 shows that the results are fairly close to theoretical calculations. More importantly, a 6% decrease in brown coal moisture level led to an improvement in the specific heat consumption of the energy block by approximately 2.8%, and a 8% decrease in humidity improved this value by approximately 3.6%. These results confirm that coal drying does indeed increase its calorific value.

EXAMPLE II - EFFECT OF REDUCING HUMIDITY ON CARBON COMPOSITION

Samples of brown coal (lignite) and coal from the Powder River Basin were subjected to chemical analysis and their moisture content was determined. The results are shown below in Table 1. As you can see, the samples of brown coal contained on average 34.03 wt.% Carbon, 10.97 wt.% Oxygen, 12.30 wt.% Fly ash, 0.51 wt.% Sulfur and 38.50 wt.% moisture. Samples of semi-bituminous coal PRB contained an average of 49.22 wt.% Carbon, 10.91 wt.% Oxygen, 5.28 wt.% Fly ash, 0.35 wt.% Sulfur and 30.00 wt.% Moisture.

The "final analysis" was carried out using the obtained values for these samples of brown coal and PRB coal by calculating the content of these constituent components for humidity 0% and ash 0%, and for a moisture level of 20%, as also shown in Table 1. As can be seen from Table 1, the chemical composition and moisture levels of coal samples vary significantly. More specifically, for a moisture content of 20%, samples of brown coal and PRB coal show a large increase in carbon content, namely up to 44.27 wt.% And 56.25 wt.%, Respectively, while the increase in oxygen content was less, namely up to 14 , 27 wt.% And 12.47 wt.%, Respectively. The sulfur and fly ash levels also increased slightly (no increase in absolute content). Importantly, the higher calorific value (HHV) for brown coal increased from 6.406 BTU / lb to 8.333 BTU / lb, while the HHV value for PBR coal increased from 8.348 BTU / lb to 9.541 BTU / lb.

Table 1 Units Analysis results Moisture and no ash Fuel Humidity 20% Lignite PRB Lignite PRB Lignite PRB Carbon the weight, % 34.03 49.22 69.17 76.05 44.27 56.25 Hydrogen the weight, % 2.97 3.49 6.04 5.39 3.87 3.99 Sulfur the weight, % 0.51 0.35 1,04 0.54 0.67 0.40 Oxygen the weight, % 10.97 10.91 22.29 16.86 14.27 12.47 Nitrogen the weight, % 0.72 0.75 1.46 1.16 0.92 0.86 Humidity the weight, % 38.50 30.00 0.00 0.00 20.00 20.00 Ash the weight, % 12.30 5.28 0.00 0.00 16.00 6.30 TOTAL the weight, % 100.00 100.00 100.00 100.00 100.00 100.00 Hhv BTU / lb 6,406 8,348 13,021 12,899 8,333 9,541 H BTU / lb -2.879 2,807 -1.664 -2,217

EXAMPLE III - THE INFLUENCE OF THE HUMIDITY LEVEL ON THE COAL HEATSET

Using the compositional values given in Table 1 and assuming a power plant capacity of 570 MW with an exhaust gas temperature of 825 ° F, the calorific value was calculated for these coal samples at various moisture levels: from 5% to 40%. The results are shown in figure 31. As you can see, between the value of HHV and the level of humidity there is a linear relationship, and lower levels of humidity correspond to higher values of calorific value. More specifically, the following HHV values were obtained for PRB coal samples: 11,300 BTU / lb at 5% moisture, 9,541 BTU / lb at 20% moisture and only 8,400 BTU / lb at 30% humidity. As for brown coal samples, the following HHV values were obtained for them: 9,400 BTU / lb at a moisture content of 10%, 8.333 BTU / lb at a humidity of 20% and only 6,200 BTU / lb at a humidity of 40%. This means that the efficiency of the steam generator can be improved by drying the coal before burning it in the furnace of the steam generator. In addition, less coal is required to produce the same amount of heat.

EXAMPLE IV - RESULTS OF CARBON DRYING IN AN EXPERIMENTAL DRYING UNIT

In the fall of 2003 and the summer of 2004, more than 200 tons of brown coal were dried in a Great River Energy pilot bed drying plant in Underwood, North Dakota. The dryer, with a capacity of 2 t / h, was developed to evaluate the profitability of drying North Dakota brown coal using low-temperature waste heat and determine the concentration efficiency of impurities such as mercury, ash and sulfur, using the possibility of a fluidized bed for gravitational separation of components.

The following coal streams were distinguished in the drying installation: the stream of the initial feed coal, the stream of treated coal, the stream of fine particles carried away, and the stream of heavy particles settling in the lower part of the layer. In the process of testing, samples were taken from these flows for analysis on the moisture, sulfur, ash and mercury content and on calorific value. Some of the samples were sorted and the subsequent analysis was carried out for different fractions of particles with the same size.

The experimental drying unit was equipped with instrumentation to determine the drying characteristics for various operating conditions. An information collection system made it possible to register measurement data in a drying unit with an interval of 1 minute. Installed instrumentation provided the ability to calculate the balance of mass and energy in the system.

The main components of the experimental drying plant were: coal supply equipment, coal loading hopper, fluidized bed dryer, air supply and heating system, internal heat exchanger, purification devices (dust collector), instrumentation and control and data acquisition system (see figure 32). Screw augers were used to load raw coal into a drying unit and to unload products from it. To control the feed rate and provide an air lock in the coal supply and discharge system, blade devices were used. The coal hopper dispensers provided the necessary intensity and total amount of coal supplied to the drying unit. Heavy particles and dust were accumulated in collectors, which were weighed before and after the tests. The output stream was unloaded by gravity into a container equipped with weights. Coal charging system provides up to 8000 lb / hr of coal drying installation, the coal particle size of less than _^1/4 inch. The air supply system provided 6000 std. cube feet per minute at a pressure of 40 inches of water. The heat capacity of the air preheater heat exchanger was 438,000 BTU / hour, and the heat capacity of the internal heat exchanger was 250,000 BTU / hour. This heat and the amount of air supplied were sufficient to remove about 655 pounds of water per hour.

In typical tests of the hopper was charged with 18,000 pounds of coal having a particle size not greater than _^1/4 inch. Before the test, the collectors were unloaded, and the container weights were recorded. Samples of coal supplied to the drying unit were taken either when loading the hopper, or during testing simultaneously with samples of dust from the dust collector, unloaded heavy particles and product from the container (usually every 30 minutes after the unit reaches steady state). Then included a dust collector, augers and air locks for all coal flows. The air supply fan was started, and its performance was set at 5000 std. cube feet per minute. Then, at full speed, the coal supply system was turned on to load the drying unit. After the fluidized bed was established in the dryer, the air temperature increased, and the heating corresponded to the temperature of the internal heat exchanger, and the air flow was set at the required level. Then the tests continued for 2-3 hours. One test was conducted for eight hours. At the end of the test, the collectors were weighed and the container weights were recorded. The measurement results were transferred to an Excel format table, and the taken coal samples were transferred for analysis to the laboratory. Then the collectors and container were unloaded to prepare for the next test.

During the fall of 2003, 150 tons of brown coal were processed in a single-stage experimental drying plant with a material distribution surface area of 23.5 ft ² . The feed rate of coal into the fluidized bed ranged from 3,000 lbs / hour to 5,000 lbs / hour. The air flow rate ranged from 4400-5400 std. cube feet per minute (3.1-3.8 feet / second). The degree of coal moisture reduction is a function of the feed rate and the amount of heat supplied to the dryer. The first experimental module removed about 655 pounds of water per hour at a design water temperature of about 200 ° F. With a coal feed rate of 83.3 lb / min, it can be determined that the degree of water removal is 0.13 lb of water / lb of coal.

During the summer of 2004, the dryer was refitted, so that it contained two stages and an internal heat exchanger of greater heat output. As a result of the conversion of the module, its thermal capacity increased to approximately 750,000 BTU / hour, and the water removal rate was 1,100 lb / hour. In the new module, another 50 tons of coal were dried. In the modified module, the collection of a stream of heavy particles from the first stage was also provided. Heavy particles are fluidizable material that has been removed from the bottom of the first stage. It consisted primarily of particles of larger sizes and increased density and separated in the first stage under the influence of gravity. Materials, temperature and heat balances for different input and output streams are shown in Tables 2-4. The total area of the distribution plate was 22.5 ft ² .

Table 2 The experimental setup, test 44

Table 3 Experimental setup, test results 44 Test 44 results ARA 14.22 Point Parameter Hhv 7175 4672,082 BUT #/hour 6524 ARS 0.55 TM 31.48 2053.8 AR, mercury 55.35 ARA 15.21 Temp, ° С 46.22 water fb Hhv 5830 F exit ARS 0.53 Flow / hour 79182 AR, mercury 68.8 Temp, ° С 77.78 Warm in Temp ° F 80 BTU / hour 11085480 AT Water, FB, On G DC inlet pound / hour 363.7 5.6% Pound / hour flow 79182 TM 21.22 77,2 Temp ° F 179.4 ARA 30.26 Warm in 11671143 Hhv 5434 302.9223 BTU / hour ARS 0.5 FROM Air, FB, AR, mercury 117.6 at the entrance Temp, ° С 38.89 Pound / hour flow 20619 Pace, F 152.7 N Air, FB, Warm in 679287 at the exit BTU / hour Pound / hour flow 20619 Hw Temp, ° С 41.06 # H20 / # D-rail, 0.0137 Warm in D UC BTU / hour 427101 # / hour,% 856.6 13.13% Hw # H20 / 0,05606 TM 26.46 226.6 # D-star. Fb ARA 15.4 humidity I exit Hw _output - Hhv 6858 900,406 Hw _output 873.4 13.39% ARS 0.76 balance AR, mercury 117.6 masses 97.21% balance Temp ° F 115,2 coal, hhv 100.8% balance E GT water 108.0% #/hour 4248.2 65.1% TM 24.5 1040.8

As you can see, the humidity decreased from 31.5% at the inlet to 24.5% in the output stream (GT). Thus, an experimental coal drying plant has demonstrated that North Dakota brown coal can be reliably and economically dried using low-temperature waste heat from a thermal power plant.

Table 4 shows the characteristics of coal for the feed stream, the flow of the carried particles, heavy particles and the output product. As you can see, the effluent stream is characterized by a high mercury and ash content, the heavy particle stream contains a lot of mercury and sulfur, and the output flow characteristics with respect to the heat content and the content of mercury, ash and SO ₂ / MBTU have significantly improved.

The flow of particles carried out mainly contained particles passing through a sieve 40, and the flow of heavy particles contained particles not passing a sieve 8.

Table 4 Characteristics of coal in different streams, test 44 Coal Pounds Mercury ppb Ash% HHV to BTU / lb Sulfur,% #SO ₂ / MBTE Innings 14902 91.20 18.05 5830.00 0.53 1.82 Heavy particles 2714 100.61 15.41 6877,00 0.76 2.20 Particles 789 136.58 30.26 5433.75 0.50 1.86 Output product 7695 65.83 14.22 7175.25 0.55 1,54

Thus, the mercury and sulfur content in the output in test 44 decreased by 40% and 15%, respectively.

The changes in time of the temperature of the fluidized bed, measured at six points inside the bed, and the air temperature at the outlet, are presented in the graphs of figure 34. This information was used together with the moisture content in coal (obtained from coal samples) to reduce the mass and energy balance for drying unit and determining the amount of moisture extracted from coal.

The moisture content in the fluidized bed and in the output stream was determined from coal samples and indicated in pounds of water contained in the coal, per pound of dry coal, as shown in figure 35. The results show that the moisture content of the inlet coal ranged from 0.40- 0.60 pounds of N ₂ O / pound of dry coal (28.5-37.5% of the weight of wet coal), while the humidity of the output product varied in the range of 0.20-0.40 pounds of H ₂ O / pound of dry coal (16.5-28.5% of the weight of wet coal). In other words, the drying process of coal using a low-temperature fluidized bed provided a moisture level decrease of about 10% with the residence time of coal particles in the fluidized bed of about 30 minutes. An increase in the temperature of the air creating a fluidized bed or an increase in the heat supply to the internal heat exchanger led to an increase in the rate of moisture removal. The values of calorific value for zero humidity obtained for the feed coal stream and for the output product stream showed that during the drying process there was no noticeable oxidation of carbon and the yield of volatile compounds.

The amount of moisture extracted from coal during the drying process was determined using four methods: the total mass balance for the drying plant, the moisture balance of the air, the coal moisture balance and the total energy balance for the drying plant. The total energy balance method was based on balancing the heat fluxes at the inlet and outlet of the drying plant: the heat supplied by the internal heat exchanger and the changes in the heat of air and coal inside the drying plant, assuming that the difference represents the heat needed to evaporate moisture from the coal. It was assumed that there are no leaks to the external environment. The air moisture balance method was based on measuring the air flow rate and air humidity at the inlet and outlet. The amount of moisture evaporated from coal was calculated by the difference between the moisture content of the air flows at the inlet and outlet and their speed. Similarly, the moisture balance of coal was based on the moisture measured in the feed coal and the product stream and the flow rates. The total mass balance method was based on the difference in the masses of the coal feed stream and the output product, taking into account the mass of material remaining in the dryer, samples taken and one percent loss. The resulting difference was considered the mass of water removed from the coal.

The calculation results shown in figure 36 show that there was achieved a sufficient proximity of the values of the amount of moisture removed from coal, which were obtained by four different methods.

The figure 37 shows data on the composition of the flow of heavy particles for seven tests using a modified experimental drying plant. In Test 41, the best results were obtained with 48% sulfur and mercury and only 23% BTU and 25% by weight. Using the results of the test with the air jigging machine in module 4, we could expect the removal of 37% of 48% for mercury 18%, 27% of 48% for sulfur 13% and 7.1% of 23% for a BTU loss of 1.6%.

The above characteristics and drawings provide a complete description of the structure and operation of the heat treatment unit in accordance with the present invention. However, the invention can be used in other combinations, modifications, variants and working conditions without going beyond its essence and scope. For example, it can be used in any combination of primary and secondary heat sources using fluidized or other layers, and can be used as one or several stages. In addition, the drying principle described in this invention is not limited to improving the quality of coal to be burned in steam generators of power plants or industrial enterprises, but can also be used to dry granular materials for the production of glass, aluminum, pulp and other industries. For example, sand used in the manufacture of glass can be dried and preheated in a fluidized bed dryer using the heat of the flue gases exiting the chimney of the furnace before sand is fed to the glass melting furnace. This will increase the thermal efficiency of the glass production process. In addition, the invention can be used to regenerate amine scrubbers.

Another example is the use of a fluidized bed dryer as a calciner for aluminum production. To obtain aluminum from bauxite ore, it must be crushed and sieved if necessary to remove large inclusions, such as debris. Then crushed bauxite is mixed in a solution of hot caustic soda in autoclaves for leaching. In this case, the alumina present in the ore dissolves. After removing red mud by draining and filtering, the caustic soda solution is pumped into huge settling tanks where crystallization of alumina occurs. Then, the aluminum oxide is filtered and sent to the kilns for drying, and at a very high temperature it turns into a fine white powder, alumina. The apparatus of the invention could be used as a kiln in this and other similar processes.

As another example, for illustration purposes, the use of waste heat sources in greenhouses in which tomatoes and other crops are grown can be indicated. Therefore, the description should not be construed as limiting the invention to the specific form described.

Claims (20)

1. Installation of heat treatment of a product at an industrial enterprise, producing at least two different types of waste heat, containing:
(a) a reservoir for receiving the product;
(b) the first heat source to be applied to the product;
(c) a first heat exchanger operably connected to the reservoir, with said first heat source supplied to said first heat exchanger;
(d) a second heat source with heat of a different type from the first heat source to be applied to the product;
(e) a second heat exchanger operably connected to the reservoir by said second heat source supplied to said second heat exchanger;
(f) in which the product is kept in the tank under the action of a joint first heat source and a second heat source at a sufficient temperature and for a sufficient time to achieve the required degree of processing; and
(g) in which “heat source” means a gaseous or liquid medium with an increased heat content obtained from the influence of a process or unit of equipment separate from the heat treatment plant, and this gas or liquid medium is used for the secondary task of supplying heat content to the heat exchanger instead of dumping it into quality of waste. 2. The heat treatment installation according to claim 1, in which the source of waste heat is selected from the group consisting of flows of cooling water, hot condenser cooling water, hot flue gases, hot flue gases, spent production steam and heat emitted by operating equipment. 3. The heat treatment unit according to claim 1, wherein the fluidized bed dryer is used as a reservoir. 4. The heat treatment installation according to claim 1, in which a fixed-bed dryer is used as a reservoir. 5. The heat treatment installation according to claim 1, in which granular materials are used as the product. 6. The heat treatment installation according to claim 1, in which the industrial enterprise is a power plant. 7. The heat treatment installation according to claim 1, in which the temperature created in the tank by the heat source is about 93-149 ° C. 8. The heat treatment installation according to claim 1, which further comprises at least one additional heat source in the form of a source of used heat supplied to the tank by means of an appropriate heat exchanger, and an additional heat source or source of main heat supplied to the associated heat source, “Primary heat source” means the amount of heat produced for the primary purpose of supplying heat content to a coupled heat exchanger. 9. The heat treatment unit according to claim 1, which further comprises a diffusion pipe operatively connected to the tank for supplying a fluidized gaseous stream to the tank during the heat treatment process to reduce condensation inside the tank. 10. The heat treatment installation according to claim 1, which further comprises a conveying device inside the tank for moving part of the product having a higher specific gravity than the relative specific gravity of the other product contained in the tank during the heat treatment process in the far zone of the tank to improve heat treating the rest of the product with a low specific gravity inside it. 11. The heat treatment unit of claim 10, wherein a screw auger is used as the conveying device. 12. The heat treatment installation of claim 10, which further comprises a scrubber functionally connected to the reservoir, the conveying device during the heat treatment moving part of the product having an increased specific gravity completely outside the reservoir into the scrubber for further processing, use or disposal. 13. The heat treatment installation according to item 12, in which the scrubber further comprises:
(a) a collection container for receiving a portion of a product having a higher specific gravity exiting the heat treatment unit, said collection including means for directing fluidized flow through a product having a higher specific gravity contained in the collection to separate a product having a lower specific gravity captured in it; and
(b) a fluidized flow source operatively coupled to the collection vessel; and
(c) in which a product having a lower specific gravity, which is separated from a product having a higher specific gravity, is returned to the tank for further heat treatment. 14. The heat treatment installation according to item 12, in which the scrubber further comprises:
(a) a collector used to receive a portion of a product having a higher specific gravity and exiting the heat treatment plant, wherein such a product having a higher specific gravity contains a higher concentration of at least one environmentally undesirable element compared to the concentration of this an undesirable element in the product that enters the heat treatment unit; and
(b) means for treating unwanted elements contained in a product having a higher specific gravity to recycle it ecologically. 15. The heat treatment installation according to 14, in which the environmentally undesirable elements are selected from the group consisting of sulfur, ash and mercury. 16. The heat setting according to claim 1, in which the heat treatment of the product includes reducing the moisture content in the product. 17. The heat treatment installation according to claim 5, in which the granular material contains coal. 18. Installation for drying coal used in a power plant having a source of waste heat, containing:
(a) a fluidized bed dryer having an interior for receiving coal, in which the coal located in the dryer is moved from one end of the dryer to the other end during drying;
(b) a fluidizing stream for liquefying the coal particles contained in the dryer;
(c) a first heat exchanger for transferring heat from a source of waste heat to a fluidizing stream to raise its temperature before it flows through the dryer;
(d) a second heat exchanger for transferring heat from the source of waste heat to a third heat exchanger integrated in the dryer to increase the internal temperature of the dryer to a temperature equal to or lower than 93 ° C in order to reduce coal moisture; and
(e) in which "source of waste heat" means a gaseous or liquid stream having an increased heat content resulting from the process or from a piece of equipment separate from the heat treatment unit, for example, a gaseous or liquid stream used for the secondary purpose of increasing the heat content of the heat exchanger instead dumping this thread. 19. The coal drying apparatus according to claim 18, further comprising a second source of waste heat, the type of which is different from the type of the first source of waste heat, in which the heat contained in the two sources of waste heat enters through the corresponding heat exchangers into a first heat exchanger operatively associated with a fluidizing stream, or into a second heat exchanger operatively connected to a third heat exchanger integrated in the dryer. 20. Installation for drying coal, operating in an industrial enterprise having at least two sources of waste heat of various types, this installation contains:
(a) a fluidized bed dryer having an interior for receiving coal in which coal placed in the dryer is moved during the drying process from one end of the dryer to the other end;
(b) an air pre-heater located between the dryer and two different sources of waste heat to transfer heat from each of the sources of waste heat to the air stream passing through the air pre-heater before this stream enters and flows through the dryer, in which the air stream liquefies the coal particles contained in the dryer;
(c) a heat exchanger operatively connected to the dryer, for transferring heat from at least one of the waste heat sources to the dryer in order to increase the internal temperature of the dryer in order to reduce coal moisture; and
(d) in which "source of waste heat" means a gaseous or liquid stream having an increased heat content resulting from the implementation of a process or from a piece of equipment separate from a heat treatment plant, for example, a gaseous or liquid stream used for the secondary purpose of providing heat content to a heat exchanger instead dumping this thread.

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