JP5053279B2 - Boiler generating steam from flue gas with high electrical efficiency and improved slag quality - Google Patents

Description

  The present invention relates to a boiler for drying, igniting and burning waste and generating steam by heat exchange with combustion exhaust gas. Steam will continue to be used for power generation.

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

  US Pat. No. 6,269,754 discloses a steam generator for superheated steam for combustion plants with corrosive flue gas. It essentially has a radiation compartment and a convection compartment, has a plate with at least one superheater and is arranged inside the radiation compartment wall, and there is a space between this plate and the radiation compartment wall. Is provided. At least a portion of the superheater is disposed in this space within the radiation compartment as a wall superheater. This space contains a less corrosive gas atmosphere at a pressure higher than the gas pressure in the combustion chamber. This makes it possible to reach a high superheat temperature without corrosion on the final superheater, so that the superheater can be made of an inexpensive material.

  However, US Pat. No. 6,269,754 does not make direct contact between the flue gas and the superheater, and therefore has poor energy transfer efficiency from the flue gas to the steam.

  European Patent No. 0536268 from the applicant discloses a method and apparatus for burning different types of solid and possibly liquid waste materials. Solid and possibly liquid waste material a) Stepped solid waste material is supplied to the rotary kiln at such a high temperature that liquid slug is formed at the rotary kiln inlet. B) partial burning on the grid, b) optionally adding liquid trash material to the solid trash material burning on the stepped grate, c) grate sieving material, boiler ash, fly Ashes and ash products, such as residual products from flue gas dedusting, are collected from the combustion process and returned to the input of the rotary kiln where they are placed in the liquid slag. It is burned by the process introduced. In this way, slag, fly ash and other harmful residual products from the combustion process are melted into the glassy mass from which salt or heavy metals cannot leach.

  However, EP 0536268 does not provide an optimized and efficient electrical output from the combustion of solid and liquid waste materials.

  In a world where natural energy resources are increasingly scarce, such as oil, there is an increasing demand for energy supplied from other sources. When waste is burned in a boiler, energy can be extracted from the combustion process. Thus, when supplied to the steam turbine driving the generator, the combustion process to supply steam that is not condensed and has a sufficiently high temperature to ensure that the steam is highly efficient and provides a high power output. It is important to optimize. Such steam can be, for example, superheated steam.

  Accordingly, there is a need for a boiler that is optimized to allow high power output from superheated steam, and a final superheater with higher temperatures on the walls.

  Usually superheated steam comes from the so-called final superheater. However, in a boiler, some gases, such as combustion exhaust gas and ash particulates, are corrosive and erode the final superheater due to their corrosivity, resulting in a shortened life of the final superheater.

  Accordingly, there is a need for a boiler having a final superheater that is provided with some means for extending the life of the final superheater.

  These requirements include a reactor disposed downstream of a moving bed furnace and co-combusted by optionally burning secondary fuel to generate a less corrosive gas stream, and said corrosive It is filled when the boiler is equipped with a final superheater that is placed in a low gas flow. This boiler dries waste, ignites and burns it, and generates steam by heat exchange with combustion exhaust gas.

  As a result, the present invention has the advantage that the life of the boiler's final superheater is increased and the boiler also provides a high and efficient power output due to the increased steam temperature in the final superheater.

  In addition, this final superheater can apply higher temperatures when exposed to cleaner gases, ie less corrosive gases and ash particulates.

  The invention will be described more fully below in connection with a preferred embodiment and with reference to the drawings.

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

  In general, the term “superheater” or “final superheater” refers to a device that further heats the steam generated by the boiler, thereby increasing the thermal energy in the steam and reducing the likelihood of the steam condensing. Superheated steam is logically known as superheated steam, and conversely, non-superheated steam is called saturated steam or wet steam. It is important to avoid the latter steam and therefore mainly use superheated steam. Thus, when this latter steam is supplied to the steam turbine driving the generator, it provides a high and efficient power output, especially when the temperature and pressure of the steam are sufficiently high.

  Generally, bottom ash is called slag. Bottom ash or slag is defined as ash that is removed from the bottom portion of the boiler combustion zone. Ash is defined as the residual product from the combustion process.

FIG. 1 shows one embodiment of a boiler that uses a reactor combined with a burner applied to generate less corrosive gases. Generally, this boiler (1) dries, ignites and burns the waste. When burning the waste, gaseous atmosphere, that is, flue gas (3) is first dropped Mono燃 ware of the resultant structure to the first.

The reactor (16) can be a sintering reactor, a rotary kiln, a fluidized bed or a spouted bed. The reactor, heavy metal leaching is reduced, and sintering the bottom ash as availability of the bottom ash is improved.

  This sintering reactor is a reactor that heats the ash / slag so that the leaching characteristics are improved. This means that heavy metal leaching from the ash / slag is reduced.

  In fluidized beds or high-speed fluidized beds, smooth and stable recirculation of solids through a dipleg or another solids trap is important for good operation. In the spouted bed, a relatively coarse, uniformly sized solid exhibits a somewhat related contact mode in contact with the gas. In this operation, a high velocity jet of gas pierces the solid bed, thereby transferring the particulates to the top of the bed. The rest of the solid slowly moves downward around the jet, passing through the slowly permeating gas. There is also a behavior between foaming and jet, which can be called jet fluidized bed behavior.

  The reactor (16) generally burns waste and converts it into slag and / or ash. The waste to be burned can be any mixture of household waste, bark, industrial waste and hospital waste and other types of waste. Usually this waste is fed from left to right in the figure into the reactor using a grate block, for example a reciprocating grate (21). This grate can be combined with one or more conveyors to carry the waste.

  This reactor is placed behind this grate array (21) in the direction of waste flow.

  The waste combustion process is then traced from left to right in the figure, starting at reference numeral 3 for the flue gas, proceeding to reference numeral 7 and ending at reference numeral 6. At reference numeral 7, the corrosive gas stream is the result of the previous process, and conversely at reference numeral 6, the less corrosive gas stream is the result of the subsequent process. This less corrosive gas stream is the output from the reactor (16), optionally burned by fuel (18), usually secondary fuel (18). This secondary fuel is selected so as to generate a flue gas that is less corrosive than the flue gas from the waste or garbage.

  In this embodiment, the reactor is burned with secondary fuel (18) from the left hand side. This combustion follows the direction of waste transfer within the reactor, and as a result, this less corrosive gas flow as output from the reactor is cocurrent as indicated by arrow 6.

  Alternatively or additionally, the combustion of the reactor can be carried out using a burner (19) that can be burned with the secondary fuel (18), i.e. the burner is oil, gas, coal, It can be burned with any combination of biomass, air and selected trash or waste classification. This can also be applied when the secondary fuel is additionally or alternatively supplied directly to the reactor. Said combustion can be carried out using a burner (19) and / or in a reactor.

  This burner can be a suspension burner, an oil burner or the like, optionally supplied with coal or gas.

  The injection of fuel and air into the reactor inlet comes through a separate housing / chute separated from the corrosive flue gas (7).

  Since this reactor is burned, it reaches a higher temperature than a reactor without combustion. This heat is needed to burn off the volatiles and sinter dust, slag, trace amounts and heavy metal species. This can be regarded as a post-treatment process, i.e. a boiler or garbage combustor combined with a reactor. As a result, the final ash and / or slag from the reactor is leaching traceable and heavy metals such as one or more leachable Pb, As, Cd, Cu, Zn, Ni and Zn. Due to its low content of seeds, it is well suited for reuse in road construction etc. and / or for disposal. Therefore, environmental damage from ash and slag is minimized.

  This ash and / or slag is fed from the reactor using a bottom ash or slag removal device from the reactor via a piston pusher or a belt conveyor, for example, to a place filled with water.

  Thus, the concept shown in the figure provides an integrated bottom ash process and improved electrical plant efficiency. Therefore, this integrated post-treatment ensures that the final bottom ash and / or slag to be manufactured meets the current environmental and technical constraints required for reuse, and at the same time the final superheater (8) steam temperature. High efficiency fires of waste such as municipal solid waste, for example, to supply less corrosive flue gas (6), which can be applied to increase the electrical efficiency of the plant's garbage combustion boiler It is advantageous to combine lattice combustion with bottom ash aftertreatment (using this reactor) in a single plant. No need for separate ash and / or slag transfer, storage, and handling / processing from grate, all processes are integrated, energy efficient, and contained within a single plant It is.

  The electrical efficiency of the refuse combustion plant is due to the generation of less corrosive flue gas (6) that allows higher steam temperature (about 500 ° C.) at the outlet 8b of the final superheater (8), Remarkably improved. Furthermore, it makes it possible to dispose of a large amount of bottom ash and slag from garbage combustion due to the immobilization of trace amounts and heavy metal classifications that would otherwise be leached.

  The less corrosive gas is essentially free of corrosive components such as Cl, K, Na, Zn, Pb, while the corrosive gas is, for example, one or more of Cl, K, Na, Contains corrosive components such as Zn and Pb. In essence, a less corrosive gas can be understood as a gas that does not cause corrosion by the final superheater.

  FIG. 2 is a diagram of one embodiment of a boiler with a separator element that uses a reactor combined with a burner (19) applied to generate a less corrosive gas.

  In this embodiment, the reactor is burned with secondary fuel (18) from the right hand side. This combustion does not follow the direction of waste transfer in the reactor, and as a result the less corrosive gas flow as output from the reactor is countercurrent as indicated by arrow 6. Note that the reactor is located at the end in the direction of transfer of waste discharged directly from the grate into the reactor.

  Alternatively or additionally, the combustion of the reactor can be carried out using a burner (19) that can be burned with the secondary fuel (18), i.e. the burner is made of oil, gas, coal It can be burned with any combination of biomass, air and selected trash or waste classification. This also applies when the secondary fuel is additionally or alternatively supplied directly to the reactor.

  Since this reactor is burned, it reaches a higher temperature than a reactor without combustion. This heat is needed to burn off the volatiles and sinter dust, slag, trace amounts and heavy metal species. This can be regarded as a post-treatment process, i.e. a boiler or garbage combustor combined with a reactor. As a result, the final ash and / or slag from the reactor is that of one or more traceable and heavy metal species such as Pb, As, Cd, Cu, Zn, Ni and Zn. Due to its low content, it is well suited for reuse and / or disposal in road construction and the like. Therefore, 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, i.e., reference numbers 6 and 7, are treated differently so that they are not mixed.

  The reason is that this less corrosive gas (6) should remain separated from the corrosive gas (7) resulting from grate combustion.

  As a result, according to the present invention, to maintain gas separation, i.e., the final superheater (8) is protected from the corrosive gas (7), whereby the superheater is mainly exposed to the non-corrosive gas (6). A separator is provided to ensure that this is done. Said separation of the flue gas (3) is maintained using a separator element denoted by reference numeral 4. This element can be provided in the exemplary embodiment as a plate (4a) or in the form of a wall (4b).

  This plate (4a) is a normal water-filled boiler tube panel that extends from one boiler side wall, which is also usually a water-filled boiler tube panel, to another boiler side wall, which plate is on the side wall It is suspended by. This plate can be corrosion protected on the surface by high alloy Cr—Ni overlay welding or by essentially refractory refractory materials.

  This wall (4b) is a normally reinforced brick or cast refractory wall that extends from one boiler side wall to another boiler side wall. This reinforcement can be hollow so as to allow the passage of a cooling medium, for example liquid, vapor, gas or air.

  Furthermore, this separator element is provided as a passage in another exemplary embodiment, i.e. the plate (4a) and the wall (4b) can be used in various combinations to form a passage. This passage can also have a cylindrical shape.

  This separator element therefore remains separated in this respect from the less corrosive gas stream (6) and the corrosive gas stream (7) and mainly from the less corrosive gas from the reactor (16). Ensure that stream (6) arrives at the final superheater (8). Eventually, the optimum position of this separator element can be reflected in a highly efficient and high power output from a generator driven by a steam turbine fed with steam from the boiler.

  The separator element is adapted to be hung on or off the boiler wall. In an exemplary embodiment, the separator element is pivotable at the top of a support point suspended on opposite boiler sidewalls and, for example, forward / backward at the bottom on the boiler sidewall. It can be a plate, wall or passage that can be moved and fixed to different positions.

  Generally applicable to any embodiment, ie when combustion is performed both from the left hand side (FIG. 1) and from the right hand side (FIG. 2), the less corrosive gas (6) and The corrosive gas (7) continues to flow in the boiler toward the mixing zone (10) of the boiler (1).

  Also common for any embodiment is that steam (2) between 300 ° C. and 450 ° C. leaves the one or more superheaters and is finally finished by one or more pipes. It is supplied to the inlet (8a) of the superheater (8) through which this steam (2) is heated, resulting in a temperature rise between 25 ° C and 200 ° C.

  This hotter steam (2a), i.e. steam having an elevated temperature, is supplied to the steam turbine (14), for example, from the outlet (8b) of the final superheater (8). Therefore, this steam (2a) can be used to generate electric power. For example, the steam can be supplied to the steam turbine (14) from the outlet using piping, and the steam turbine can drive a generator (15) and then generate power from the generator. Since the hotter steam (2a) is the output from the boiler, i.e. the output from the final superheater, this boiler therefore also provides high power output efficiency. Of course, this is higher than when steam (2) between 300 ° C. and 450 ° C. is the output from the boiler. Therefore, heating of the steam in the final superheater provides high power and high efficiency output.

  Typically, the final superheater (8) is located in the separator element (4), for example the plate, adjacent to the wall or in the passage, and in all cases the less corrosive gas. In the flow (6). Thus, it is an advantage that this final superheater is less exposed to corrosion.

  Thus, it is an advantage applied to both figures that the final superheater is located in the less corrosive gas flow (6) compared to the corrosive gas flow. When the final superheater is placed in the corrosive gas flow (7), not according to the invention, such placement of the final superheater results in a short life of the final superheater and is aggressive. This arrangement in a harsh environment requires excessive and frequent repair work due to exposure to corrosive gases during its operational life.

  The present invention thus has the advantage that the life of the final superheater is increased and the boiler provides high power efficiency.

  As discussed above, the less corrosive gas (6) and the corrosive gas (7) are mixed together in the mixing zone (10) of the boiler (1). The boiler further includes a blowing unit (12). This effectively mixes the less corrosive gas (6) and the corrosive gas (7) by blowing secondary air, so that the mixed gas reaches the top zone (13) of the boiler. It is made to be able to burn it out efficiently before you do it. Furthermore, although this applies to both figures, the boiler is provided with an industrial draft fan that sucks gas, ie combustion exhaust gas, less corrosive gas and corrosive gas, through the boiler. Moreover, the combustion air can be blown under the grate array (21).

  When the less corrosive gas (6) and the corrosive gas (7) together reach the mixing zone (10) of the boiler, they are mixed by blowing in secondary combustion air for burnout. The mixed gas is cooled using evaporating walls in the radiation zone and one or more superheaters (11) that generate steam (2) between 300 ° C and 450 ° C. This (i.e., cooling with the one or more superheaters) is that when less corrosive gas travels in direction (6), less corrosive gas (6) is removed from the plate, wall or Regardless of whether it is in contact with the passageway and / or whether it is the result of combustion by a burner to the reactor from the left hand side or from the right hand side.

1 is a diagram of one embodiment of a boiler that uses a reactor combined with a burner applied to generate non-corrosive gas. FIG. 1 is a diagram of one embodiment of a boiler with a separator element that uses a reactor combined with a burner applied to generate a non-corrosive gas. FIG.

Claims (17)

A boiler (1) for generating steam (2) and hotter steam (2a) by exchanging heat with combustion exhaust gas (3), the boiler comprising:
A reciprocating grate arrangement (21) for drying, igniting and burning the waste;
Located downstream of the grate array (21), receives products from the combustion process in the grate array (21), and burns the products with the secondary fuel (18) to be less corrosive A reactor (16) for generating a gas flow (6);
A final superheater (8) disposed in the less corrosive gas stream (6),
The boiler (1), wherein the reaction furnace (16) is a sintering reaction furnace, a rotary kiln, a fluidized bed or a spouted bed .   Boiler according to claim 1, wherein the combustion with the secondary fuel (18) is performed using a burner (19) and / or within the reactor itself.   A boiler element according to claim 1, wherein the boiler maintains separation of the flue gas (3) into the less corrosive gas stream (6) and corrosive gas stream (7). The boiler further comprising (4).   Boiler according to claim 3, wherein the separator element (4) comprises a plate (4a) or a wall (4b).   A boiler according to any of the preceding claims, wherein a number of the separator elements (4) form a passage.   Boiler according to any one of the preceding claims, wherein the separator element (4) or passage is adapted to be hung on or off the wall of the boiler.   The boiler according to any one of claims 1 to 6, wherein the less corrosive gas (6) and the corrosive gas (7) generate steam (2) between 300 ° C and 450 ° C. A boiler cooled by an evaporating wall and one or more superheaters (11).   Boiler according to any one of the preceding claims, wherein the steam (2) is heated in the final superheater (8).   The boiler according to any of the preceding claims, wherein the final superheater (8) results in a temperature rise between 25 ° C and 200 ° C compared to the temperature of the steam (2), which is higher The boiler which heats the said steam (2) so that it may become the steam (2a) of the set temperature.   Boiler according to any one of claims 1 to 9, wherein the less corrosive gas (6) is substantially free of Cl, K, Na, Zn, Pb.   A boiler according to any of claims 1 to 10, wherein the corrosive gas (7) comprises one or more of Cl, K, Na, Zn and Pb.   The boiler according to any one of claims 1 to 11, wherein the combustion exhaust gas (3) is a result of combustion of waste (9).   A boiler according to any of the preceding claims, wherein the less corrosive gas (6) is efficiently mixed with the corrosive gas (7) by blowing secondary air so that the mixture becomes The boiler further comprising a blowing unit (12) adapted to allow efficient combustion before reaching the top zone of the boiler.   The boiler according to any one of claims 1 to 13, wherein the steam (2a) is used for power generation when supplied into a steam turbine (14) that drives a generator (15).   15. Boiler according to any one of the preceding claims, wherein the reactor (16) is a leachable pole, such as a leachable Pb, As, Cd, Cu, Zn, Ni and Zn with a low content. A boiler that produces final ash and / or slag having a low content of trace and heavy metal species.   A boiler according to any of the preceding claims, wherein the secondary fuel (18) is any combination of oil, gas, coal, biomass, air and selected waste or waste classification.   The boiler according to any one of claims 1 to 16, wherein the secondary fuel is selected to generate a gas that is less corrosive than the combustion exhaust gas from the waste or garbage.

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