KR101029906B1 - A boiler producing steam from flue gases with high electrical efficiency and improved slag quality - Google Patents

Abstract

The present invention relates to a boiler (1) for drying waste, igniting and burning to produce steam (2, 2a) by heat exchange with combustion exhaust gas (3). The boiler 1 comprises a reactor 16 which burns with secondary fuel 18 to produce a less corrosive gas stream 6 and a final superheater 8 located in the less corrosive gas stream 6. do. The heater 16 may be a sintering reactor, a rotary kiln, a fluidized bed or a fractionated bed. This extends the life of the final superheater and allows the boiler to provide high power and efficient electrical power.

Garbage, waste, incineration, combustion, flue gas, heat exchange, steam, boilers, power generation

Description

A boiler producing steam from flue gases with high electrical efficiency and improved slag quality}

The present invention relates to a boiler for drying, igniting and burning waste to generate steam by heat exchange with combustion flue gases. The steam is then used to produce electricity.

Garbage to be burned can be a mixture of household waste, bark, industrial waste and hospital waste, and any mixture of other types of waste.

US Pat. No. 6,269,754 discloses a steam generator for superheated steam in an incineration plant having corrosive combustion flue gases. It basically comprises a radiating part and a convection part, the convex part having at least one superheater and a plate arranged inside the one side wall of the radiating part, with a space between these plates and the radiating part wall. At least part of the superheater is arranged as a wall superheater in the space of the radiator. This space has a less corrosive gas powder crisis at pressures higher than the gas pressure in the combustion chamber. As a result, high superheater temperatures can be reached without corrosion to the final superheater, making the superheater a cheap material.

However, US Pat. No. 6,269,754 does not allow direct contact between the flue gas and the aforementioned superheater, so that energy transfer from the flue gas to steam is less effective.

Applicant's European Patent No. 0536268 B1 discloses a method and apparatus for incineration of various types of solids and, in some cases, liquid waste material. Solids and, in some cases, liquid waste material, a) partially combusts solid waste material on the stepped grate where liquid slag is delivered to the rotary kiln at high temperatures formed at the inlet of the rotary kiln, and b) optionally Add the liquid waste material to the solid waste material incinerated on the stepped grate, and c) recover the ash products, such as grate screening, boiler ash, fly ash, and residual products from scrubbing of flue gas from the combustion process; These products are then incinerated by returning these products to the rotary kiln input stage and introducing these products into the liquid slag at the input stage. In this way, slag, fly ash and other harmful residue products from the combustion process can be melted into glassy masses where salts and heavy metals cannot be leached.

 However, EP 0536268 B1 does not provide optimum efficient electrical output from incineration of solid and liquid waste materials.

In a world where natural energy sources, such as oil, are gradually decreasing, the demand for energy from other energy sources is increasing. When burning waste in a boiler, energy can be extracted from the incineration process. It is therefore important that the incineration process is optimized to provide uncondensed steam and that the temperature is high enough to provide high efficiency and high electrical output when supplied to the steam turbine driving the generator.

Therefore, there is a need for boilers and final superheaters with high temperatures in the walls that are optimized to provide high electrical power from superheated steam.

In general, superheated steam comes from the so-called end superheater. However, some of the gases in the boiler, for example combustion flue gases and ash particles, are corrosive and will corrode the final superheater because of the corrosiveness, which results in a shortened lifetime of the final superheater.

Therefore, there is also a need for a boiler with a final superheater provided with some means for extending the life of the final superheater.

These requirements are placed in the reactor and the less corrosive air stream where the boiler is located downstream of the moving bed furnace and in some cases simultaneously burned with the combustion of the secondary fuel to produce a less corrosive air stream. This is achieved in the case of a final superheater located.

Accordingly, the present invention has the advantage that the boiler provides a high and efficient electrical output due to the extended life of the final superheater of the boiler and the high steam temperature in the final superheater.

The final superheater can also be applied at high temperatures when it encounters scrubbing gases, ie less corrosive gases and ash particles.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 shows one embodiment of a boiler using a reactor with a burner adapted to generate a noncorrosive gas.

2 shows an embodiment of a boiler using a reactor with a burner having a separating element and adapted to generate a noncorrosive gas.

Throughout the drawings, the same reference numerals indicate similar or corresponding features or functions.

In general, the term "superheater" or "end superheater" refers to a device that heats steam generated by a boiler to further increase thermal energy in the steam and reduce the likelihood of the steam condensing. Superheated steam is logically known as superheated steam, and conversely, unsuperheated steam is called saturated steam or wet steam. It is important to avoid the latter non-heated steam and to use mainly superheated steam. Thus, when this latter steam is supplied into the steam turbine driving the generator, it will output electricity with high efficiency, especially if the temperature and pressure of the steam are high enough.

In general, the ash on the floor is called slag. Floor ash or slag is defined as ash removed from the bottom of the combustion zone of the boiler. Ash is defined as the residual product from the combustion process.

1 shows one embodiment of a boiler using a reactor with a burner applied to generate less corrosive gas. In general, the boiler 1 dries, ignites and burns waste. When the waste is incinerated, first, the result of incineration of the waste 9 is a gas atmosphere, that is, combustion exhaust gas 3.

The reactor 16 may be a sintering reactor, a rotary kiln, a fluidized bed or a spouted bed. This reactor sinters the bottom ash to reduce leaching of heavy metals and improve the availability of the bottom ash.

This sintering reactor is a reactor for heating ash / slag so that the leaching property is improved. This means that the leaching of heavy metals from ash / slag is reduced.

In fluidized beds and fast fluidised beds, smooth and stable recycling of solids through solids capture devices is critical for good operation. In the fractionation layer, a relatively rough, uniformly sized solid exhibits a somewhat related contact mode in contact with the gas. In this operation, a high velocity gas jet penetrates the solid layer and transports the particles to the top of the layer. The remainder of the solids slowly moves downwards around the off-gas and through the slowly rising infiltration gas. Behaviors such as bubbling and spouting can also be seen, which can be referred to as jetted fluidized bed behavior.

The reactor 16 generally burns waste and turns it into slag and / or ash. Garbage to be burned can be household waste, bark, industrial waste and any mixture of hospital waste and other kinds of waste. Garbage is generally supplied to the reactor from the left side to the right side of the figure by means of a grate block, for example a reciprocating grate 21. The grate can be combined with one or more conveyors to transport the waste.

The reactor is located behind the grate device 21 in the flow direction of the waste.

The waste incineration process takes place from the left side to the right side of the drawing, starting with reference numeral 3 together with the combustion flue gas, proceeding to the reference numeral 7, and ending with the reference numeral 6. Corrosive gas streams at 7 are the result of pretreatment, and conversely, gaseous gases that are less corrosive at 6 are the result of post-treatment. The less corrosive gas stream is the output of the reactor 16 and, in some cases, is combusted with a fuel 18, generally a secondary fuel 18. Secondary fuel is selected to develop combustion gases that are less corrosive than combustion gases from the waste or waste.

In this embodiment, the reactor is combusted from the left with secondary fuel 18. This combustion takes place in the conveying direction of the waste in the reactor, and as a result, a stream of less corrosive gas flows as indicated by arrow 6 as the output from the reaction.

Alternatively, or in addition, combustion of the reactor may take place by a burner 19 which may be combusted with the secondary fuel 18, ie the burner may be oil, gas, coal, biomass, air and selected waste. Any combination of waste can be combusted. This also applies when the secondary fuel is fed directly to the reactor in addition or as an alternative. The combustion may take place by burners 19 and / or occur in the reactor.

The burner may be a suspension burner or an oil burner supplied with coal or gas in some cases.

The injection of fuel and air into the reactor inlet takes place via a separate housing / chute separated from the corrosive flue gas 7.

Since the reactor is combusted, the reactor will reach a higher temperature compared to the reactor that is not combusted. This heat is needed to burn volatiles and sinter waste slag and trace heavy metal species. This can be thought of as a post-treatment process, ie a boiler or waste incinerator is combined with a reactor. As a result, the final ash and / or slag from the reactor are less likely to contain leachable trace heavy metal species such as one or more of leachable Pb, As, Cd, Cu, Zn, Ni and Zn. Very suitable for reuse and / or disposal. Thus, environmental damage from ash and slag is minimized.

The ash and / or slag is provided from the reactor by a bottom ash or slag removal device, for example a water-filled piston pusher or belt conveyor.

Therefore, the flooring treatment can be integrated and the electrical efficiency can be improved by the concept shown in the drawings. Thus, for example, combining high efficiency grate combustion, such as urban solid waste, with post-treatment (by reactor) of flooring in a single plant, the resulting environment and / or slag produced by the final flooring and / or slag It is advantageous to meet the technical constraints, and at the same time integrating the aftertreatment produces a less corrosive combustion flue gas (6), which raises the steam temperature of the final superheater (8) to improve the electrical efficiency of the plant's waste combustion boiler. Let's do it. The entire process is integrated and energy efficient in a single plant without the need for transporting, storing and subsequent handling / handling of the flooring and / or slag from the grate of another plant.

The electrical efficiency of the waste incineration plant is significantly improved due to the generation of less corrosive combustion flue gas 6, thus increasing the steam temperature at the outlet 8b of the final superheater 8 (about 500 degrees Celsius). In addition, other leachable trace heavy metal parts are fixed, allowing for the disposal of large quantities of flooring and slag from waste incineration.

The less corrosive gas is essentially free of corrosive components such as Cl, K, Na, Zn, Pb, etc., while the corrosive gas comprises at least one of corrosive components such as Cl, K, Na, Zn and Pb. Inherently less corrosive gases can be understood as gases which less corrode the final superheater.

2 shows one embodiment of a boiler using a reactor with a burner 19 which is applied to generate less corrosive gas as a separator element.

In this embodiment the reactor is combusted from the right with secondary fuel 18. This combustion takes place along the conveying direction of the waste in the reactor, so that a less corrosive gas stream as an output from the reactor flows back as indicated by arrow 6. The reactor is located at the end of the conveying direction of the waste discharged directly from the grate into the reactor.

Alternatively or additionally, combustion of the reactor can take place by a burner 19 which can be burned with the secondary fuel 18, ie this burner is oil, gas, coal, biomass, air and selection. Any combination of waste or trash can be combusted. This also applies to the case where the secondary fuel is fed directly to the reactor as an additional or alternative.

Since the reactor is combusted, the reactor reaches a higher temperature compared to the reactor not combusted. This heat is needed to burn volatiles and sinter waste slag and trace heavy metal species. This can be thought of as a post-treatment process, ie a boiler or waste incinerator is combined with a reactor. As a result, the final ash and / or slag from the reactor are less likely to contain leachable trace heavy metal species such as one or more of leachable Pb, As, Cd, Cu, Zn, Ni and Zn. Very suitable for reuse and / or disposal. Thus, environmental damage from ash and slag is minimized.

At this point in the process, it is important that the corrosive gas and the less corrosive gas mix, because these, i.e., 6 and 7, are treated differently.

This is because the less corrosive gas 6 is kept separate from the corrosive gas 7 coming from the grate combustion.

Thus, according to the invention, it is mainly subjected to the non-corrosive gas 6 since it is separated to maintain the gases separately, ie to protect the final superheater 8 from the corrosive gas 7. The separation of the combustion flue gas 3 is maintained by a separating element indicated by reference numeral 4. This element may in one embodiment be provided as a plate 4a or in the form of a wall 4b.

This plate 4a is typically a boiler tube panel filled with water extending from one side wall of the boiler, and also a boiler tube panel filled with water extending to the other side wall of the boiler, and the plate is suspended from the side wall. This plate can protect the surface from corrosion, for example by high alloy Cr-Ni overlay welding or by essentially hard refractory materials.

The wall 4b is typically a reinforced brick or cast fireproof wall extending from one side wall of the boiler to the other side wall. Such reinforcements are hollowed out to allow cooling medium, such as liquid, steam, gas or air, to pass through.

The separating element can also be provided as a channel in another embodiment, ie the plate 4a and the wall 4b can be used in various combinations to form the channel. This channel also has a tubular shape.

Thus, the separating element allows the less corrosive gas stream 6 and the corrosive gas stream 7 to be kept separated at this point, and the less corrosive gas stream 6 from the reactor 16 is the final superheater. 8). In the long run, the optimum position of the separating element allows very efficient high power output from a generator driven by a steam turbine supplied with steam from the boiler.

The separating element is designed to be suspended from the wall of the boiler. In one embodiment, the separating element may be a plate which allows the top to pivot on a bearing suspended from the opposite boiler side wall, for example the floor can be moved and fixed in different positions forward and backward on the boiler side wall. have.

In general, any embodiment applies, i.e., where combustion takes place from the left (FIG. 1) and from the right (FIG. 2), wherein the less corrosive gas 6 and the corrosive gas 7 are contained in the boiler 1 in the boiler. ) Is continued to the mixing stage 10 side.

Also in any embodiment, after leaving the at least one superheater, steam 2 at 300 degrees Celsius to 450 degrees Celsius is supplied to the inlet 8a of the final superheater 8 by means of at least one tube, which steam is passed through the superheater. Heated to increase the temperature from 25 degrees to 200 degrees Celsius.

This warm steam 2a, ie the steam at elevated temperature, is for example supplied to the steam turbine 14 from the outlet 8b of the final superheater 8. Thus, this steam 2a can be used to produce electricity. For example, the steam is supplied from the outlet into the steam turbine 14 by a pipe to drive the generator 15, from which power can be generated. Since the warm steam 2a is output from the boiler, ie from the final superheater, the boiler also provides high power efficiency. Of course, this is higher than the case where steam 2 of 300 to 450 degrees Celsius is output from the boiler. Thus heating the steam in the final superheater provides a high power and high efficiency output.

Typically the final superheater 8 is located in close proximity to the separating element 4, for example the plate, the wall or in the channel, and in any case in the less corrosive gas stream 6. Thus, the superheater is less corrosive, which is advantageous.

Thus, in both figures, there is an advantage that the final superheater is located in the less corrosive gas stream 6 than the corrosive gas stream 7. If the final superheater is located in the corrosive gas stream 7 but not in accordance with the present invention, this position of the superheater will shorten the life of the final superheater and, if located in an erosive environment, will receive corrosive gas for its operating life. Excessive and frequent repair work will be required.

Therefore, the present invention has the advantage that the life of the final superheater is extended and the boiler provides high power efficiency.

As described above, the less corrosive gas 6 and the corrosive gas 7 are mixed in the mixing bed 10 of the boiler 1. The boiler further includes a blower unit 12. It is adapted to efficiently mix the less corrosive gas 6 with the corrosive gas 7 by means of secondary air, so that the mixture can be effectively combusted before reaching the upper zone of the boiler. In addition, as applied to both figures, the boiler is equipped with an industrial draft fan that draws in a variety of gases, ie combustion flue gases, less corrosive gases and corrosive gases. In addition, combustion air may be blown into the lower side of the grate arrangement 21.

When the less corrosive gas 6 and the corrosive gas 7 together reach the mixing stage 10 of the boiler, these gases are mixed by injection of secondary combustion air for complete combustion, the mixed gases being one Cooled by the evaporation wall in the superheater 11 and the radiation zone above, they produce steam 2 between 300 and 450 degrees Celsius. This (ie cooling by the one or more superheaters) may be applied to the burner from the left or from the right side to the reactor side, regardless of whether the less corrosive gas 6 contacts the plate, wall or channel as it moves in the direction of 6. Occurs regardless of whether it is burned by

Claims (17)

A boiler (1) composed of a moving bed furnace grate arrangement structure (21), which generates steam (2, 2a) by heat exchange with combustion flue gas (3) by drying, igniting and burning waste. Located in the reactor 16 located downstream of the moving bed furnace grate arrangement 21, which is combusted with secondary fuel 18 to generate a less corrosive gas stream 6 and the less corrosive gas stream 6 And a final superheater (8), wherein the reactor (16) is a sintering reactor, rotary kiln, fluidized bed or spreaded bed. 2. The boiler according to claim 1, wherein the combustion by the secondary fuel (18) takes place by means of a burner (19) or in the reactor itself. 2. The boiler according to claim 1, further comprising a separating element (4) for separating and maintaining the combustion flue gas (3) into the less corrosive gas stream (6) and the corrosive gas (7). 4. Boiler according to claim 3, characterized in that the separating element (4) comprises a plate (4a) or a wall (4b). 4. Boiler according to claim 3, characterized in that the plurality of separating elements (4) form a channel. 6. A boiler according to claim 4 or 5, wherein the separating element or channel is adapted to be suspended from the wall of the boiler. 4. The less corrosive gas (6) and the corrosive gas (7) are cooled by one or more superheaters (11) and evaporation walls in the spinning zone to produce steam (2) between 300 and 450 degrees Celsius. Boiler characterized in that. The boiler according to claim 1, wherein the steam (2) is heated in a final superheater (8). 9. The final superheater (8) according to claim 8, wherein the final superheater (8) heats the steam (2) so that the temperature rises to steam (2a), a temperature of 25 to 200 degrees Celsius compared to the temperature of the steam (2). Boiler characterized by the increase. delete 4. The boiler according to claim 3, wherein the corrosive gas (7) comprises at least one of Cl, K, Na, Zn, Pb groups. 2. The boiler according to claim 1, wherein the combustion flue gas (3) is a result of incineration of waste (9). The method of claim 3, wherein the secondary air is blown to effectively mix the less corrosive gas 6 and the corrosive gas 7 so that the mixture can be effectively combusted before reaching the upper end 13 of the boiler. Boiler characterized in that it further comprises a blower (12). 10. Boiler according to claim 1 or 9, characterized in that the steam (2a) is used to produce electricity when the steam is supplied to a steam turbine (14) driving a generator (15). delete 2. The boiler of claim 1, wherein the secondary fuel (18) is any one of oil, gas, coal, biomass, air, waste, waste, or a combination thereof. 2. The boiler of claim 1, wherein the secondary fuel is selected to produce a flue gas that is less corrosive than flue gas from the waste or waste.

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