UA100498C2 - Process and device for thermal treatment of ground hard particles from metal oxide - Google Patents

Abstract

This invention relates to a process for producing e.g. anhydrous metal oxide from metal hydroxide, wherein the metal hydroxide is at least partly dehydrated and preheated, before the metal hydroxide is introduced into a fluidized-bed reactor (19), in which the metal hydroxide is heated to a temperature of about 650 to about by combustion of fuel, and metal oxide is generated, wherein primary air and/or secondary air enriched with oxygen is supplied to the fluidized-bed reactor (19). To achieve a rather low dust emission and a small amount of grain disintegration, the oxygen or the gas enriched with oxygen is introduced into the fluidized-bed reactor (19) with a low gas velocity.

Description

MO 2008/077462 1 PCT/ER2007/010680

The field of technology to which the invention belongs

The present invention relates to a method and installation for thermal treatment of crushed solid particles, for example, for the production of calcined gypsum or dehydration of other salts, incineration of waste contaminated with organic substances (for example, sewage sludge), burning of refractory ore (for example, gold-bearing ore), burning CaCO3 and other carbonates, Sabo decomposition, other sulfates or other salts, for example, nitrates, but especially for the production of mainly anhydrous metal oxide from metal hydroxide. At the same time, the metal hydroxide is at least partially subjected to dehydration and heating before introducing the metal hydroxide into a fluidized bed reactor, in which the indicated metal hydroxide is heated to a temperature in the range of about 650 "C to about 1250 "C due to fuel combustion, and an oxide is formed of metal, and the fluidized bed reactor is supplied with primary air enriched with oxygen to an oxygen content in the range of approximately 22 to approximately 99.9 95 (in the context of this application, the specified oxygen content is always given in volume percentages) and/or secondary air, which oxygenated to an oxygen content in the range of about 30 to about 99.99.

Prior art

Production of metal oxide from metal hydroxide in a circulating fluidized bed is known, for example, from patent document ОЕ198 05 897 С1. In the patent document OE 197 22 382 A!1, it is proposed to enrich the gas supplied to a fluidized bed reactor with a stationary fluidized bed with oxygen. Oxygen must be introduced into the reactor above the distribution plate at supersonic speed through Laval nozzles. In the case of a stationary fluidized bed, this is necessary because at low gas velocities, the oxygen supply nozzles will be scaled due to the high temperature in the fluidized bed and the intense heat exchange between the fluidized bed and the nozzles, and therefore the service life of the nozzles will be quite short. On the other hand, the very high velocity of the oxygen-enriched gas in the fluidized bed results in a significant stress on the granular solids, similar to that applied in a jet mill, as a result of which the solids can be destroyed from a significant to a very significant degree, depending on their strength limit. . In most cases, such destruction of grains is undesirable.

According to the method known from the document OE198 05 897 C1, the volume of processing of solid particles can be increased in the event that a greater amount of heat is supplied due to fuel combustion. Until then, as long as only non-oxygenated air is used, gas velocities can be increased in the known installation, which can lead to increased dust emission and, in addition, to increased destruction of the grains of fine-grained solid particles. Likewise, increased gas velocities can be realized if a known plant is converted from a high calorific fuel to a low calorific fuel with the same solids treatment volume, provided air is supplied for fuel combustion.

An increase in dust emission with increasing gas velocities, as well as more grain destruction and, as a result, deterioration of product quality are considered unsatisfactory factors.

Disclosure of the essence of the invention

In this regard, the task of this invention is to provide the above-mentioned method using a circulating fluidized bed, which allows improving the characteristics of known installations or improving existing installations for the use of fuels with a low calorific value in them without increasing the emission of dust and reducing the quality of products .

According to the invention, this task is solved, mainly, in such a way that secondary air, enriched with oxygen, is supplied to the reactor with a circulating fluidized bed at a speed in the range from 5 to 300 m/s, in particular, at a speed less than 250 m/s , better, less than 200 m/sec, best - less than 150 m/sec. This supply of oxygen or oxygen-enriched gas with a very low consumption provides a particularly mild mode for the production of a product, for example, a metal oxide, due to the reduction of gas velocities in the apparatus of the installation, which allows to significantly reduce the destruction of grains. As a result, the quality of the product improves significantly.

At the same time, due to the enrichment of the secondary air with oxygen, the gas velocity in the filter for catching dust, which is used according to the method, is reduced, due to which dust emissions can also be reduced. It should be noted that the supply of oxygen-enriched secondary air to the fluidized bed reactor leads, in addition, to a pronounced improvement in the quality of material processing during the firing process. This provides either increased production of metal oxide from metal hydroxide under the same basic conditions or the possibility of using fuels with a low calorific value without reducing the productivity of the plant, or allows achieving both of the indicated results. In particular, when using fuels with a low calorific value, which have a high content of inert components, in a metal oxide production plant, large volumetric flows can be obtained without enriching the secondary air with oxygen, which can lead to higher gas velocities. At the same time, the need for combustion air decreases, for example, in the case of gaseous fuel obtained during air gasification of bituminous coal, while the cooling of the produced metal oxide becomes less effective, and the temperature of solid particles increases. . As a result, the requirements for the specific heat of combustion are also increasing. According to the invention, these disadvantages are compensated by the fact that the gas, which is fed at a low speed to the fluidized bed reactor as primary air and/or secondary air, is enriched with oxygen, since in this way not only the optimal volume flow can be reduced, but as well as gas velocities.

If, for example, the holes for the secondary air supply are lined with refractory brick, refractory concrete or similar material, then scale formation will not occur even at high oxygen concentrations and low gas velocities. In the known methods, when using the nozzles of the distribution board, refractory lining is not possible.

According to a specific preferred embodiment of the invention, oxygen-enriched gas is supplied to the circulating fluidized bed of the fluidized bed reactor with a gas velocity of less than 100 m/s, in particular, in the range from 10 to 100 m/s.

For the production of metal oxide, for example, for the production of aluminum oxide, as it turned out, it is desirable that the firing in a fluidized bed reactor be carried out at temperatures in the range from 850 to 1050 "С.

According to the invention, the decrease in the destruction of grains, which can, for example, be more than 15 95, exceeds the smallest decrease in the gas velocity in one of the devices of the installation. In different devices, the reduction of the gas velocity can vary and is, for example, in the range from about 15 95 to about 30 95.

A particularly pronounced reduction in grain destruction and dust emissions can be achieved if the primary air supplied to the low flow fluidized bed reactor is oxygenated to an oxygen content in the range of 22 95 to 49 95 and/or if the secondary air is enriched oxygen to an oxygen content in the range of about 90 95 to about 99.55 95.

Preferably, the gases that are supplied to the fluidized bed reactor are indirectly and/or directly heated using the heat released in the production process to a temperature in the range from 100 to 800 "C, in particular, from about 150 to about 750 C. Due to the previous heating of the primary gas, the secondary gas and/or, for example, a gaseous fuel, is fed to the fluidized bed reactor together with the heat generated during the process, thereby reducing the overall energy requirement for the process. As an alternative to heating the feed gases to a fluidized bed reactor, it is also possible due to heat supplied from the outside.

The temperature of the product, that is, the metal oxide produced according to the method of the invention, should not normally exceed about 80 "C. For this, the metal oxide discharged from the fluidized bed reactor can be cooled indirectly, at least during one, first stage cooling due to direct contact with air and/or oxygen or a mixture of the two specified gases, and at least during one of the other stages located downstream of the specified at least one stage of direct cooling, which is a cooler with fluidized bed. It is particularly desirable that the secondary air supplied to the fluidized bed reactor is heated, at least during one of the cooling stages, in the first and/or second. Thus, oxygen for enrichment of the secondary air can already be added before the stages cooling of the metal oxide, so that oxygen also contributes to the cooling of the metal oxide in the same way and time is preheated before it is fed to the fluidized bed reactor.

According to the best embodiment of the invention, at least one of the stages of direct cooling contains a feed pipe, which pneumatically transports the metal oxide in the upward direction, and a separating cyclone. Therefore, solid particles are simultaneously cooled and transported to a higher level, which, when possible, provides further transport under the influence of gravity.

When using fuel with a relatively low calorific value, less than 7500 kJ/kg, for the production of aluminum oxide from aluminum hydroxide in accordance with the method proposed by the present invention, the fluidized bed reactor can be placed from about 1.5 to 3

Nm3/h, preferably from about 2 to 3 Nm3/h, and most preferably from about 2.3 to about 2.5

Nm/h of oxygen (95 95) together with secondary air, based on 1 ton of aluminum oxide produced per day. When applying the method proposed by the present invention, the installation, which works, for example, using petroleum fuel (fuel oil), can as a result be transferred to a gaseous fuel with a low calorific value, which is, for example, approximately from 4000 to 5500 kJ/kg, without decrease in productivity or deterioration of product quality.

According to another embodiment, about 23 to about 25 Nmz/hr is fed to the fluidized bed reactor per 1 ton per day of alumina produced. of additional air mixed with about 2 to about 4 Nm3/hr., preferably about 2.5 to about 3.5, or best, about 2.9 to 3.1 Nm3/hr. oxygen (95 95). Due to this, the amount of additional air supplied to the fluidized bed reactor is significantly reduced, compared to known

MO 2008/077462 3 PCT/ЕР2007/010680 ways, so that the optimal consumption decreases and, therefore, the speed also decreases to the same extent. This leads to an unexpectedly high reduction in the destruction of grains and, thus, to an improvement in the quality of the product.

The task of this invention, in addition, is solved by means of an installation for heat treatment of solid particles of material, which includes at least one stage of preheating, at least one fluidized bed reactor, means for supplying gaseous fuel to the fluidized bed reactor, and at least , one cooling stage, which consists of at least three (separate) coolers, at least one of which is placed and connected to the means for supplying gaseous fuel in such a way that the gaseous fuel before entering the fluidized bed reactor passes through at least one cooler for preheating gaseous fuel.

Preferably two of the (separate) coolers are fluidized bed coolers. Each of these coolers can include a number of chambers. According to the best embodiment, an additional (separate) cooler that provides heating of gaseous fuel can be a cooling cyclone.

According to the invention, a pneumatic conveyor can be placed upstream from the fluidized bed reactor for supplying solid particles to the fluidized bed reactor, and the pneumatic conveyor is preferably connected by means of a pipeline to the supply pipeline for hot solid particles that are removed from the fluidized bed reactor. At the same time, for example, a cyclone located upstream from the reactor is connected to a cyclone located downstream from the reactor, so that the gas from the cyclone located upstream from the reactor can mix with solid particles that are removed from the cyclone , which is located downstream from the reactor.

The invention will be disclosed in more detail below by way of embodiments and with reference to the drawings.

Fig. 1 is a schematic diagram of the production process according to the first embodiment of the invention.

Fig. 2 is a schematic diagram of the production process according to the second embodiment of the invention.

Fig. 3 is a schematic diagram of the production process according to the third embodiment of the invention.

In the method illustrated in Fig. 1 - Fig. 3, the metal hydroxide to be dehydrogenated (dehydrated) is fed by means of the screw 1 of the screw conveyor or a similar means and introduced into the stage of preheating, which can be carried out by the heater 2 , which functions with the removal (removal) of layer particles. A hot mixture of gases with temperatures in the range from about 200 to about 500 °C is supplied to the specified heater 2 with the removal of layer particles through the pipeline C. The mixture of gas and solid particles is sent through the pipeline 4 to the filter 5, which can be, for example, a bag filter, a cyclone or an electrostatic filter.

The spent gas from the filter 5 is removed through the pipeline 6. As an alternative, downstream from the filter 5, a means for additional processing of the spent gas can be placed (a scrubber for cleaning the spent gas, a means for condensing water, and the like). The metal hydroxide dried in this way is sent to the lower part of the pneumatic conveyor 8 through the pipeline 7, through which solid particles are sent to the separating cyclone 10 with the help of air supply from the pipeline 9. The exhaust gas from the separating cyclone 10 passes through the pipeline 11 to the next cyclone 12.

The solid particles obtained in the separating cyclone 10 are taken through the pipeline 13 to the next heater 14 with the removal of the particles of the layer, in which at least partially dehydrated solid particles come into direct contact with the hot exhaust gas coming from the pipeline 15, after which they are transported through the pipeline 16 go to the separating cyclone 17, from which the exhaust gas enters the first heater 2 with the removal of layer particles through the pipeline

Z. The solid particles separated in the additional separating cyclone 17 are sent through the pipeline 18 to the fluidized bed reactor 19, in which the process takes place at temperatures in the range from 850 to 1050 "С.

The reactor 19 with a fluidized bed in the lower part contains a relatively dense fluidized bed 20 of metal oxide particles. Liquefaction in this fluidized bed is carried out with the help of primary air, which comes from the pipeline 21 and which is supplied by means of the distributor 22 to the lower part of the fluidized bed 20. At the same time, the primary air is heated in the air heater 23, described in more detail below.

In addition, gaseous and/or liquid fuel is introduced into the fluidized bed 20 from the outside through one or more nozzles 24, while the fuel is heated and ignited by means of hot metal oxide particles located in the fluidized bed 20. Complete combustion is carried out in the reactor 19 by with the help of heated secondary air, which is supplied through pipeline 25. The desired combustion temperature is achieved due to the use of means of this combustion.

The fluidized bed reactor 19 can also be an annular fluidized bed reactor described in patent document OE102 60 739. In this case, the secondary air supply can be carried out through a central pipe placed in the annular fluidized bed reactor.

However, in addition, it is possible to split the secondary air supply and introduce secondary air through

MO 2008/077462 4 PCT/ЕР2007/010680 pipeline located above the distribution board and through the central pipe.

The hot waste gas from the fluidized bed reactor 19, which contains metal oxide, is diverted through the channel 26 to the recirculation cyclone 27. From the recirculation cyclone 27, the waste gas is fed to the second heater 14 with the transfer of layer particles through the pipeline 15.

Part of the hot solid particles separated in the recirculation cyclone 27 is returned to the fluidized bed reactor 19 through the pipeline 28, while the remaining parts of the hot solid particles are sent to the first stage of cooling. This first stage of cooling is configured in such a way that the additional air transported by the pipeline 30, the preheated liquefaction air by another pipeline 31 and the technical oxygen supplied by the third pipeline 33 are mixed with each other and directed to the pneumatic supply pipeline 34 through the next pipeline 33 Hot solids from line 29 are introduced into feed line 34 so that the hot solids mix with the air/oxygen mixture coming from line 33, whereby the solids are cooled while the air/oxygen mixture is heated. To the obtained mixture of gases and solid particles with the help of pipeline 11, waste gas, which is removed from the separating cyclone 10, is mixed, and then it is introduced through the pipeline to the cooling cyclone 12. In the specified cooling cyclone, gas and solid particles are separated from each other, while the gas flow in the form preheated, oxygen-enriched secondary air is supplied to the fluidized bed reactor 19 through pipeline 25.

Through the pipeline 36 solid particles are sent to the cooler 23 with a fluidized bed, which at the same time is an air heater of the primary air. The solid particles are further cooled in the fluidized bed cooler 23, while the primary air is heated in the tube bundles. The primary air heated in this way is then led through the pipeline 21 to the fluidized bed reactor 19.

Fluidized bed cooler 23 is supplied with liquefying air through pipeline 37, which is connected to the second fluidized bed cooler 38. In said second fluidized bed cooler 38, the solid particles are cooled to the desired final temperature by means of one or more liquid refrigerants 39. The liquefaction air, which is introduced into said two fluidized bed coolers by pipelines 37, is fed by blower 41 through pipeline 40. Primary air , which is heated in the tube bundles of the first fluidized bed cooler, is supplied with the help of another air blower 42. As an alternative or in addition to the supply of oxygen through the supply pipeline 34, to the primary air, which is pumped using the air blower 42, or to the liquefaction air for two coolers 23 and 38 with a fluidized bed, which is supplied by pipeline 43, technical oxygen can also be mixed.

In the embodiment shown in Fig. 2, gaseous fuel is used as fuel. As mentioned above, this gaseous fuel is supplied to the fluidized bed reactor 19 through nozzles 24. The gaseous fuel, before being fed to the fluidized bed reactor 19, may be preheated.

For this purpose, gaseous fuel is fed through the pipeline 44 into the pipe bundle of the additional fluidized bed cooler 45, in which the solid particles that are removed from the cooling cyclone 12 are cooled. The fluidized bed cooler 45 is located upstream of the fluidized bed cooler 23, so , that the solid particles from the cooling cyclone 12 first pass through the fluidized bed cooler 45, then the fluidized bed cooler 23, and finally the fluidized bed cooler 38. These fluidized bed coolers can have a different number of chambers.

In Fig. Another embodiment of the invention is illustrated. Here, gaseous fuel is also used as fuel in fluidized bed reactor 19. For this, the gaseous fuel is introduced through the pipeline 46 to the next cooling cyclone 47, after which the spent gases leaving it are introduced into the fluidized bed reactor 19 through nozzles 24. The solid particles separated in the first fluidized bed cyclone 12 are sent to the pipeline 48 , which, for example, serves as a pneumatic underwater transport pipeline, and with which the gaseous fuel supply pipeline 46 is also connected. The mixture of gas and solid particles, which enters the second cooling cyclone 47, is separated in the specified cooling cyclone 47, while the solid particles are directed to the first fluidized bed cooler 23 through the pipeline 36.

Example 1. Improvement of the installation for the use of gas with a low calorific value.

The current plant for the production of 3,300 tons of aluminum oxide per day operates using petroleum fuel (fuel oil), which has a calorific value of 39,876 kJ/kg. This installation should be converted to the use of gaseous fuel with a calorific value equal to only 4642 kJ/kg. At the same time, the production of aluminum oxide should reach 3300 tons/day.

Approximately 8000 Nm/h. of oxygen (95 95) is mixed with additional air, and the gaseous fuel is preheated. Gaseous fuel is heated either in a cooler 45 with

MO 2008/077462 5 PCT/ER2007/010680 fluidized bed shown in Fig. 2, to 180 "C or, if the properties of the gas allow, directly to a temperature of 450 7C using a cooling cyclone 47 in accordance with the embodiment illustrated in Fig. 3. Oxygen is introduced into the fluidized bed reactor 19 by means of nozzles 24 together with gaseous fuel from at a speed in the range from 20 to 50 m/sec. Aluminum oxide is removed from the fluidized bed cooler 38 at a product temperature of no more than 80 s.

Due to the oxygen supply to the fluidized bed cooler 19 described above, aluminum oxide production at the level of 3300 tons/day can also be maintained using low calorific fuel. At the same time, the improvement of the product quality is achieved by reducing the destruction of the grains. The optimal volumetric flow rate in the installation is less than or at most equal to the optimal volumetric flow rate under the condition of using petroleum fuel.

Example 2. Product quality improvement in terms of grain destruction

In the installation corresponding to the embodiment illustrated in Fig. 1, with the help of which 3300 tons of aluminum oxide are produced per year at an air consumption of 120,000 Nmz/h., to the additional air, which is supplied through pipeline 30, is mixed using pipeline 32, approximately 10,000

NmZ/h of oxygen (9595), while the supply of additional air through pipeline 30 is reduced by approximately 40,000 Nm/h. Thus, in the pipeline 33, the oxygen content is obtained, which is equal to approximately 34.3 95. As a result, the optimal volume flow and, therefore, the gas velocity in the heater 14 with the transfer of layer particles and the separating cyclone 17 is reduced by approximately 18595, in the cooling cyclone 12 - by approximately 2895, and in the reactor 19 with a fluidized bed and recirculation cyclone 27 - by approximately 16 95. As a result of the destruction of aluminum oxide grains, it can be reduced by more than 16 95. p.

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Claims (12)

1. A method of thermal treatment of crushed solid particles, in which the solid particles are subjected to at least partial dehydration and heating before introducing the solid particles into a circulating fluidized bed reactor (19) with a fluidized bed, in which the solid particles are heated to a temperature in the range of about 050 to about 1250 "C due to fuel combustion, and new solid particles are formed, while the fluidized bed reactor is supplied with a primary gas enriched with oxygen to an oxygen content in the range of approximately 22 to 99.9905 and/or a secondary gas enriched with oxygen to oxygen content in the range from about 30 to about 99.9905, the primary or secondary gas is introduced into the fluidized bed reactor (19) at a rate in the range from about 5 to about 300 m/sec., in particular at a rate of less than 200 m/s sec., and the fuel is preheated for input to the fluidized bed reactor (19). 2. The method according to item I, which is characterized by the fact that the primary or secondary gas is introduced into the fluidized bed reactor at a speed in the range from about 10 to about 100 m/sec. 3. The method according to any one of claim 1 or claim 2, which is characterized by the fact that the crushed solid particles are a metal hydroxide, which is converted into a metal oxide. 4. The method according to any one of claims 1-3, which is characterized in that the primary gas, which is supplied to the fluidized bed reactor (19), is enriched with oxygen to an oxygen content in the range from about 22 to about 49 95 and/or secondary gas enriched with oxygen to an oxygen content in the range of about 90 to about 99.5 90. 5. The method according to any one of claims 1-4, which is characterized in that the oxygen-enriched gas streams, which are supplied to the fluidized bed reactor (19), indirectly and/or directly, are heated using the heat that is released in the process process, to a temperature in the range from about 100 to about 800 °C, in particular in the range from about 150 to about 750 °C. b. The method according to any one of claims 1-5, which is characterized in that the gaseous fuel, which is supplied to the fluidized bed reactor, indirectly and/or directly, is heated in advance, using the heat that is released during the technological process, to a temperature in in the range from about 100 to about 300 °C, in particular in the range from about 150 to about 250 °C. 7. The method according to any one of claims 1-b, which is characterized in that the metal oxide discharged from the fluidized bed reactor (19) is cooled at least during one cooling stage due to direct contact with air and/or oxygen or their mixture and at least during one second stage (23, 38, 45) of cooling, which is a fluidized bed cooler located downstream of the first stage of cooling. 8. The method according to claims 5-7, which is characterized by the fact that the gases supplied to the fluidized bed reactor (19) are heated in advance at least during one of the first and/or second stages (23, 38, 45) of cooling. 9. The method according to any one of claim 7 or claim 8, which is characterized in that one of the first stages of cooling includes a feed pipe (34) which pneumatically transports the metal oxide in the upward direction, 1 separating cyclone (12). 10. The method according to any one of claims 1-9, which is characterized in that the fuel has a calorific value of less than 7500 kJ/kg, in particular in the range from about 4000 to about 5500 kJ/kg, while to the reactor (19) with a fluidized bed, additional air is supplied, to which oxygen 95 95 is mixed at a rate of about 1.5 to about 3.5 Nm'"/h., per 1 ton per day of solid particles formed. 11. The method according to any one of claims 1-10, characterized in that the fluidized bed reactor (19) is supplied with about 23 to about 25 Nm"/h of additional air, to which about 2 to about 3 .5 Nm"/h. of oxygen 95 9b, per 1 ton per day of formed solid particles. 12. The method according to item I, which is characterized by the fact that in the reactor (19) with a fluidized bed, the metal hydroxide is heated to a temperature in the range from approximately 850 to 1050 2C due to fuel combustion, while metal oxide is formed.