A decoupled combustion mechanical grate furnace and combustion method thereof

Abstract

The present invention provides a decoupled combustion mechanical grate furnace and a combustion method thereof, wherein the mechanical grate furnace comprises a pre-combustion device and a main furnace body, wherein the main furnace body comprises a main grate, a top arch, a rear wall and a furnace, wherein a rear arch is arranged on the rear wall; a first and a second lower partition wall are arranged in sequence above the main grate along the direction of movement; an adjusting air duct is independently arranged on the lower partition wall; a first and a second upper partition wall are arranged in sequence on the top arch along the direction of gas flow, and the area above the lower partition wall is correspondingly divided into a gasification combustion zone, a transition combustion zone and a burnout zone. The present invention divides the main furnace body into different combustion zones and sets different partition walls and adjusting air, thereby improving the mixing effect of coal gas, flue gas and adjusting air in the furnace, making the reducing combustion zone formed in the furnace more stable, and making the components easier to control, and accurately controlling the transition from reducing atmosphere to oxidizing atmosphere, thereby reducing NO in the burnout zone. x Concentration rebound, improve partition combustion effect, achieve low NO x emissions and higher combustion efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of combustion equipment and relates to a decoupled combustion mechanical grate furnace and a combustion method thereof. Background Art

[0002] Traditional coal-fired industrial boilers mainly adopt layer combustion and are mostly chain furnaces. They generally have problems such as low combustion efficiency and high pollutant emissions. Therefore, it is necessary to develop relevant emission reduction technologies to reduce NO x There are many ways to reduce emissions, such as low-oxygen combustion technology, flue gas recirculation combustion technology, air separation and combustion technology, etc. However, the implementation of the above technologies will be limited by the structure and operation mode of the coal-fired boiler itself. Therefore, while improving the combustion technology, it is also necessary to improve the combustion equipment to give full play to the advantages of the new combustion technology.

[0003] The traditional mechanical grate furnace is a commonly used coal-fired boiler. It adopts the ignition method of heating the upper part of the fuel layer by furnace radiation. The high-temperature and high-oxygen furnace outlet area must be close to the fuel ignition area. In the main combustion area of ​​the furnace, the fuel delivery direction on the grate is opposite to the flue gas flow in the furnace. Therefore, it is impossible to effectively realize the zoning or staged combustion of the reduction zone in the early stage of combustion and the oxidation zone in the late stage of combustion, and it is impossible to deeply reduce NO x The mechanical grate furnace recirculates flue gas and mixes it with air and passes it into the lower part of the grate to reduce NO by reducing the oxygen content in the air. x However, this method will significantly reduce the ignition and burnout speed of the fuel, thus requiring a significant increase in grate length and furnace volume.

[0004] CN 101650025A discloses a decoupled combustion furnace and a decoupled combustion method, comprising a pyrolysis gasification chamber and a semi-coke combustion zone, a coke combustion zone and a burnout zone arranged in sequence below the pyrolysis gasification chamber. The decoupled combustion furnace also comprises a secondary combustion zone, at least one grate, a first air port and a second air port. The grate pushes the fuel to move through the pyrolysis gasification chamber, the semi-coke combustion zone, the coke combustion zone and the burnout zone in sequence. The lower part of the secondary combustion zone is fluidly connected with the upper part of the pyrolysis gasification chamber, the coke zone and the burnout zone to form a gas channel. The first air port is arranged in the gas channel, and the second air port is arranged in the secondary combustion zone, both of which are used to supplement air. Although the device can solve the problem of slow pyrolysis speed to a large extent, it shares a set of grates and has a slow pre-combustion speed. When the load increases, it is easy to cause the combustion interruption in the pre-combustion zone, and it is difficult to be applied to large combustion equipment.

[0005] CN 102563614A discloses a pre-combustion type mechanical grate decoupling combustion furnace and a combustion method thereof, comprising a furnace body, a main grate and a pre-combustion grate, wherein a combustion chamber partition wall is arranged inside the furnace body, and the internal space of the furnace body is roughly divided into an upstream pre-combustion chamber and a downstream main combustion chamber, the main grate is located at the lower part of the furnace body, the pre-combustion chamber is located above the front section of the main grate, and the main combustion chamber is located above the rear section of the main grate, the pre-combustion chamber and the main combustion chamber are connected through a flue gas channel above the partition wall and a coal seam channel below the partition wall, the pre-combustion grate is located in the pre-combustion chamber and is arranged above the main grate at a certain inclination angle, so that the coal seam runs along the preheating grate to the main grate; the device mainly improves the combustion efficiency of coal by arranging the pre-combustion chamber and the pre-combustion grate, but does not clearly divide the reduction zone and the oxidation zone of the combustion, and there is still a problem of poor combustion effect.

[0006] In summary, for the decoupled combustion of the mechanical grate furnace, the device needs to be improved to clarify the division and component control of the reduction zone, oxidation zone, etc., so as to improve the effect of staged combustion and reduce NO x emissions. Summary of the invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a decoupled combustion mechanical grate furnace and a combustion method thereof. The mechanical grate furnace can effectively improve the diffusion and mixing effect of flue gas, coal gas and regulating air during fuel combustion through the arrangement of the combustion device and the main furnace body, especially the arrangement of different combustion zones and partition walls in the main furnace body, control the stability of different combustion areas in the furnace and the transition of the combustion atmosphere, and realize the deep graded combustion of the mechanical grate combustion furnace.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] On the one hand, the present invention provides a decoupled combustion mechanical grate furnace, the mechanical grate furnace comprises a pre-combustion device and a main furnace body, the outlet of the pre-combustion device is connected to the inlet of the main furnace body; the main furnace body comprises a main grate, a top arch, a rear wall and a furnace surrounded by the main grate, the top arch and the rear wall, the pre-combustion device is located above the front of the main grate, the top arch is located above the main grate, the rear wall is located above the rear of the main grate, a slag discharge port is provided between the lower part of the rear wall and the rear part of the main grate, and a smoke outlet is provided between the upper part of the rear wall and the rear part of the top arch;

[0010] The rear wall is provided with a rear arch extending into the furnace, the rear arch divides the rear part of the furnace into two parts, the upper and lower parts, and separates the slag discharge port and the smoke outlet; the first lower partition wall and the second lower partition wall are arranged in sequence above the main grate along the movement direction of the main grate, the area between the lower partition wall and the main grate is a fuel channel, and the area between the lower partition wall and the top arch is a gas channel; the first lower partition wall and the second lower partition wall are independently provided with regulating air ducts;

[0011] A first upper partition wall and a second upper partition wall extending toward the furnace are sequentially arranged on the top arch along the gas flow direction, dividing the area above the lower partition wall into a gasification combustion zone, a transition combustion zone and a burnout zone respectively. The first upper partition wall is laterally positioned between the first lower partition wall and the second lower partition wall, and the second upper partition wall is laterally positioned behind the second lower partition wall.

[0012] In the present invention, the structural design of the mechanical grate furnace is to first perform preliminary pyrolysis and gasification of the fuel with a pre-combustion device, so that the fuel can start to burn at the front end of the grate, and then divide the gas area in the main furnace body into a gasification combustion area, a transition combustion area and a burnout area. Then, through the design of different partition walls and regulating air ducts, the atmosphere composition of different combustion areas is controlled, the diffusion and mixing effect of coal gas, flue gas and regulating air is improved, and the large-scale reducing combustion area formed in the furnace during the main conversion stage of fuel nitrogen is made more stable, and the transition from reducing atmosphere to oxidizing atmosphere is accurately controlled to reduce NO in the burnout area. x The rebound of concentration makes the zoned combustion effect more prominent.

[0013] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] As a preferred technical solution of the present invention, the front section of the top arch is connected to the upper part of the pre-combustion device.

[0015] Preferably, the first lower partition wall is arranged above the front end of the main grate, and an adjusting gate is provided on the first lower partition wall.

[0016] Preferably, the distance from the bottom of the first lower partition wall to the main grate is greater than the distance from the second lower partition wall to the main grate.

[0017] In the present invention, the setting of the regulating gate on the first lower partition wall can effectively adjust the thickness of the semi-coke fuel layer on the main grate, ensuring that when the fuel layer reacts with the air introduced from the lower part, gasification and combustion are carried out under suitable conditions, so that it can burn in the lower part of the fuel layer to produce CO2, and gasify in the upper part of the fuel layer to produce CO.

[0018] The distance control between the second lower partition wall and the main grate can adjust the thickness of the semi-coke layer entering the rear grate, ensuring that the semi-coke can be burned out and excess air can pass through the semi-coke layer.

[0019] Preferably, the distance between the first lower partition wall and the second lower partition wall is 50-75% of the length of the main grate, such as 50%, 55%, 60%, 62%, 65%, 68%, 70%, 72% or 75%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] As a preferred technical solution of the present invention, a first regulating air duct is provided at the upper part of the first lower partition wall, and the first regulating air duct is connected to at least one first regulating air nozzle, such as one, two, three or four.

[0021] Preferably, a second regulating air duct is provided at the upper portion of the second lower partition wall, and the second regulating air duct is connected to at least one second regulating air nozzle, such as one, two, three or four nozzles.

[0022] In the present invention, a first regulating air duct is arranged on the first lower partition wall, and the regulating air can be sprayed into the gasification and combustion zone through the first regulating air nozzle, and the reducing property of the components is adjusted by adjusting the gas components and combustion in the reduction zone; the angle of the first regulating air nozzle can be changed, thereby changing the mixing position and component distribution of the regulating air and the gasification and combustion zone gas.

[0023] Similarly, the regulated air is injected into the transition combustion zone through the second regulated air nozzle, and the transition from reducing atmosphere to oxidizing atmosphere is adjusted by adjusting the oxygen supply and combustion, thereby reducing NO x concentration rebound; the angle of the second regulating air nozzle can be changed, thereby changing the mixing position and component distribution of the regulating air and the gasification gas flowing from the gasification combustion zone into the transition combustion zone.

[0024] As a preferred technical solution of the present invention, the distance from the bottom of the first upper partition wall to the main grate is 1 / 3 to 2 / 3 of the distance from the top arch to the main grate, for example, 1 / 3, 2 / 5, 1 / 2, 3 / 5 or 2 / 3, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the distance from the bottom of the second upper partition wall to the main grate is 1 / 2 to 4 / 5 of the distance from the top arch to the main grate, for example 1 / 2, 3 / 5, 2 / 3, 7 / 10, 3 / 4 or 4 / 5, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] In the present invention, the arrangement of the first upper partition wall and the second upper partition wall is beneficial to the division of the gas combustion area and the mixing of the gases, and the distance between the first upper partition wall and the grate is smaller than the distance between the second upper partition wall and the grate, which can adapt to the characteristic that the amount of smoke discharged from the rear of the furnace is small at the front and large at the back, so as to maintain the optimal flow rate and pressure drop of the smoke in the furnace.

[0027] As a preferred technical solution of the present invention, a gasification and combustion zone wind chamber is provided below the main grate in the area between the first lower partition wall and the second lower partition wall.

[0028] Preferably, a burnout zone wind chamber is provided in the area below the main grate corresponding to the rear of the second lower partition wall.

[0029] In the present invention, a wind chamber is arranged below the main grate to provide the semi-coke on the main grate with the air required for gasification combustion or burnout, and the amount of air introduced is adjusted according to the combustion conditions at different stages; the number of the gasification combustion zone wind chamber and the burnout zone wind chamber can be multiple, so as to adjust the amount of air introduced into different areas on the main grate according to the combustion conditions of the semi-coke.

[0030] Preferably, the burnout zone is provided with a burnout air nozzle, and the burnout air nozzle is arranged at the lower part of the top arch, the front end of the rear arch or the side wall of the furnace.

[0031] In the present invention, in order to fully burn the fuel and smoke in the burnout zone, a burnout air nozzle can be additionally provided to maintain excess air in the burnout zone.

[0032] On the other hand, the present invention provides a method for decoupled combustion using the above mechanical grate furnace, the method comprising the following steps:

[0033] (1) Pre-combustion of solid fuel, pyrolysis and gasification to generate semi-coke and pyrolysis gasification gas;

[0034] (2) the semi-coke generated in step (1) enters the main grate and moves with the main grate to undergo a gasification and combustion reaction; the pyrolysis gasified coal gas generated in step (1) enters the gasification and combustion zone and is mixed with the coal gas generated by the gasification and combustion of the semi-coke to undergo a reducing combustion reaction;

[0035] (3) The flue gas generated by the reducing combustion in step (2) enters the transition combustion zone and is mixed and burned with the coal gas generated at the rear of the gasification combustion zone under ventilation conditions; after the semi-coke in step (2) passes through the second lower partition wall, it is fully burned under the action of the gas to obtain solid slag;

[0036] (4) The flue gas generated after the mixed combustion in step (3) is fully burned under the action of excess air and then leaves through the flue gas outlet.

[0037] As a preferred technical solution of the present invention, the solid fuel in step (1) includes coal and / or biomass.

[0038] Preferably, the pre-combustion in step (1) is carried out in a pre-combustion device.

[0039] Preferably, the pre-combustion device burns in a bottom ignition mode.

[0040] In the present invention, the fuel is pre-combusted to achieve preliminary pyrolysis and gasification, so that the fuel can start to burn at the front end of the grate, eliminating the preheating ignition section on the grate and improving the utilization rate of the grate; the temperature of the pre-combustion of the fuel is 500-1000°C, for example, 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] As a preferred technical solution of the present invention, during the semi-coke gasification and combustion process in step (2), air is introduced from the wind chamber of the gasification and combustion zone.

[0042] In the present invention, the upper coke of the grate between the first lower partition wall and the second lower partition wall is gasified and burned. In this stage, the nitrogen content of the fuel is relatively high. The amount of air introduced is controlled to make oxygen-poor combustion occur, and the generated CO content is relatively high. A relatively high reducing atmosphere is maintained to reduce the conversion of fuel nitrogen to NO x conversion; on the rear grate, the nitrogen content of the fuel is less, and excess air needs to be introduced to accelerate the complete combustion of the semi-coke.

[0043] The use of gasification combustion can increase the thickness of the processable fuel layer, increase the space-to-room combustion ratio, and improve the burnout rate of the later fuel, thereby reducing the length of the grate and the volume of the furnace; using a thicker fuel layer and producing more coal gas in the reduction zone can also improve the stability of the reduction zone atmosphere of the mechanical grate furnace partition combustion; moreover, the use of fuel gasification combustion is conducive to improving the adaptability of the fuel, reducing the requirements for the size of the fuel components and irregular fuels, and can improve the performance of burning biomass and garbage; biomass has a high volatile matter content, and the main pollutants in garbage are also in the volatile matter. Using smoke exhaust at the rear of the furnace can significantly increase the residence time of the volatile matter in the high-temperature furnace, which is beneficial to the burnout of volatile substances.

[0044] Preferably, a mixture of air and recycled flue gas is introduced into the gasification combustion zone in step (2).

[0045] Preferably, the mixed gas is introduced through a first regulating air duct.

[0046] In the present invention, what is introduced into the regulating air duct is generally a mixture of combustion-supporting air and circulating flue gas, wherein the ratio of air to circulating flue gas can be adjusted. By changing the air and flue gas ratio of the regulating air, the rigidity of the regulating air can be maintained when the oxygen demand is small or no oxygen supplement is required, thereby realizing the disturbing and mixing effect of the regulating air on the airflow; at the same time, by changing the incident angle of the regulating air, the reducing atmosphere in different areas can be more accurately adjusted; the regulating air mixed with a proper amount of circulating flue gas can also increase the uniformity of the reducing atmosphere and avoid local overoxygenation; the present invention changes the traditional way of using flue gas recycling, which can not only ensure the burnout speed and burnout rate of the fuel, but also reduce the flue gas recycling amount and the increased energy consumption.

[0047] In the present invention, in the mixed gas introduced into the first regulating air duct, the combustion-supporting air accounts for 0-10% of the total air entering the furnace, and the circulating flue gas accounts for 0-10% of the total air entering the furnace.

[0048] Preferably, during the reducing combustion process of step (2), NO x is reduced to N2.

[0049] Preferably, the excess air coefficient of the gasification combustion zone in step (2) is 0.6 to 0.95, for example, 0.6, 0.65, 0.7, 0.75, 0.8, 0.9 or 0.95, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] In the present invention, the combustion temperature of the gasification combustion zone is 700-1100°C, for example, 700°C, 800°C, 900°C, 1000°C or 1100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] As a preferred technical solution of the present invention, a mixed gas consisting of air and recycled flue gas is introduced into the transition combustion zone in step (3).

[0052] Preferably, the mixed gas is introduced through a second regulating air duct.

[0053] In the present invention, the second regulating air duct is set up, through the injection of the mixture of combustion-supporting air and circulating flue gas, in addition to the effects of the above-mentioned factors such as the ratio of the two and the injection angle, here it can also accurately control the transition from reducing atmosphere to oxidizing atmosphere, avoiding the problem that the gasification combustion zone and the burnout zone are not clearly distinguished, affecting the respective combustion effects.

[0054] In the present invention, in the mixed gas introduced into the second regulating air duct, the combustion-supporting air accounts for 0-15% of the total air entering the furnace, and the circulating flue gas accounts for 0-15% of the total air entering the furnace.

[0055] Preferably, the excess air coefficient of the transition combustion zone in step (3) is 0.85 to 1.1, for example 0.85, 0.9, 0.95, 1.0, 1.05 or 1.1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] In the present invention, the combustion temperature of the transition combustion zone is 800-1200°C, for example, 800°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C or 1200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] Preferably, in step (3), the thickness of the semi-coke after passing through the second lower partition wall is smaller than the thickness of the semi-coke before passing through the second lower partition wall.

[0058] In the present invention, the thickness of the material layer will be different according to the different combustion reactions before and after the main grate. According to the needs, the thickness of the material layer between the first lower partition wall and the second lower partition wall needs to be greater than the thickness of the material layer behind the second lower partition wall. In general, as the semi-coke burns, the thickness of the semi-coke gradually decreases along the movement direction of the main grate.

[0059] Preferably, during the semi-coke burnout process in step (3), air is introduced from the burnout zone wind chamber.

[0060] As a preferred technical solution of the present invention, the air in step (4) is introduced through the nozzle of the burnout zone.

[0061] Preferably, the excess air coefficient of the burnout zone in step (4) is 1.05 to 2, for example 1.05, 1.1, 1.2, 1.4, 1.5, 1.6, 1.8 or 2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0062] In the present invention, the combustion temperature of the burnout zone is 1000-1400°C, for example, 1000°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C or 1400°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] (1) The present invention uses a pre-combustion device to perform preliminary pyrolysis and gasification of the fuel, so that the fuel can start to burn at the front end of the grate, and the fuel flow direction in the main combustion zone of the mechanical grate is consistent with the flue gas flow direction;

[0065] (2) The main furnace body of the mechanical grate furnace of the present invention is divided into different combustion zones, and different partition walls and regulating winds are set to improve the diffusion and mixing effect of coal gas, flue gas and regulating wind in the furnace. In the main conversion stage of fuel nitrogen, the large-scale reducing combustion zone formed in the furnace is more stable, the composition is easier to control, and the transition from reducing atmosphere to oxidizing atmosphere is accurately controlled, reducing NO in the burnout zone. x The rebound of concentration realizes the graded and zoned combustion of fuel, and the combustion efficiency can reach more than 90%;

[0066] (3) The design of the mechanical grate furnace of the present invention improves the grate utilization and combustion efficiency, enhances fuel adaptability, and reduces the amount of flue gas recirculation and energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 is a structural schematic diagram of a decoupled combustion mechanical grate furnace provided in Example 1 of the present invention;

[0068] Among them, 1-pre-combustion device, 2-first lower partition wall, 3-first regulating air duct, 4-first regulating air nozzle, 5-main grate, 6-top arch, 7-gasification combustion zone wind chamber, 8-gasification combustion zone, 9-first upper partition wall, 10-second lower partition wall, 11-second regulating air duct, 12-second regulating air nozzle, 13-transition combustion zone, 14-second upper partition wall, 15-burnout zone wind chamber, 16-rear arch, 17-burnout zone, 18-smoke outlet, 19-slag discharge port, 20-rear wall. DETAILED DESCRIPTION

[0069] In order to better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention is further described in detail below. However, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0070] The following are typical but non-limiting embodiments of the present invention:

[0071] Embodiment 1:

[0072] This embodiment provides a decoupled combustion mechanical grate furnace, the structural schematic diagram of the mechanical grate furnace is as follows: Figure 1As shown, it includes a pre-combustion device 1 and a main furnace body, the outlet of the pre-combustion device 1 is connected to the inlet of the main furnace body; the main furnace body includes a main grate 5, a top arch 6, a rear wall 20 and a furnace surrounded by the main grate 5, the top arch 6 and the rear wall 20, the pre-combustion device 1 is located above the front part of the main grate 5, the top arch 6 is located above the main grate 5, the front section of the top arch 6 is connected to the upper part of the pre-combustion device 1, the rear wall 20 is located above the rear part of the main grate 5, a slag discharge port 19 is provided between the lower part of the rear wall 20 and the rear part of the main grate 5, and a smoke outlet 18 is provided between the upper part of the rear wall 20 and the rear part of the top arch 6;

[0073] The rear wall 20 is provided with a rear arch 16 extending into the furnace, and the rear arch 16 divides the rear part of the furnace into two parts, an upper part and an lower part, and separates the slag discharge port 19 and the smoke outlet 18; the first lower partition wall 2 and the second lower partition wall 10 are sequentially provided above the main grate 5 along the movement direction of the main grate 5, the area between the lower partition wall and the main grate 5 is a fuel channel, and the area between the lower partition wall and the top arch 6 is a gas channel; the first lower partition wall 2 and the second lower partition wall 10 are independently provided with regulating air ducts;

[0074] The top arch 6 is provided with a first upper partition wall 9 and a second upper partition wall 14 extending toward the furnace in sequence along the gas flow direction, dividing the area above the lower partition wall into a gasification combustion zone 8, a transition combustion zone 13 and a burnout zone 17 respectively. The first upper partition wall 9 is laterally positioned between the first lower partition wall 2 and the second lower partition wall 10, and the second upper partition wall 14 is laterally positioned behind the second lower partition wall 10.

[0075] The first lower partition wall 2 is arranged above the front end of the main grate 5, and an adjusting gate is provided on the first lower partition wall 2; the distance from the bottom of the first lower partition wall 2 to the main grate 5 is greater than the distance from the second lower partition wall 10 to the main grate 5; the distance between the first lower partition wall 2 and the second lower partition wall 10 is 70% of the length of the main grate 5.

[0076] A first regulating air duct 3 is provided at the upper portion of the first lower partition wall 2, and the first regulating air duct 3 is connected to three first regulating air nozzles 4; a second regulating air duct 11 is provided at the upper portion of the second lower partition wall 10, and the second regulating air duct 11 is connected to three second regulating air nozzles 12.

[0077] The distance from the bottom of the first upper partition wall 9 to the main grate 5 is 1 / 3 of the distance from the top arch 6 to the main grate 5 , and the distance from the bottom of the second upper partition wall 14 to the main grate 5 is 1 / 2 of the distance from the top arch 6 to the main grate 5 .

[0078] A gasification and combustion zone wind chamber 7 is provided below the main grate 5 in an area between the first lower partition wall 2 and the second lower partition wall 10 ; a burnout zone wind chamber 15 is provided below the main grate 5 in an area behind the second lower partition wall 10 .

[0079] The burnout zone 17 is provided with a burnout air nozzle, and the burnout air nozzle is arranged at the front end of the rear arch 16.

[0080] Embodiment 2:

[0081] The present embodiment provides a decoupled combustion mechanical grate furnace, the mechanical grate furnace comprising a pre-combustion device 1 and a main furnace body, the outlet of the pre-combustion device 1 is connected to the inlet of the main furnace body; the main furnace body comprises a main grate 5, a top arch 6, a rear wall 20 and a furnace surrounded by the main grate 5, the top arch 6 and the rear wall 20, the pre-combustion device 1 is located above the front of the main grate 5, the top arch 6 is located above the main grate 5, the front section of the top arch 6 is connected to the upper part of the pre-combustion device 1, the rear wall 20 is located above the rear of the main grate 5, a slag discharge port 19 is provided between the lower part of the rear wall 20 and the rear of the main grate 5, and a smoke outlet 18 is provided between the upper part of the rear wall 20 and the rear of the top arch 6;

[0082] The rear wall 20 is provided with a rear arch 16 extending into the furnace, and the rear arch 16 divides the rear part of the furnace into two parts, an upper part and an lower part, and separates the slag discharge port 19 and the smoke outlet 18; the first lower partition wall 2 and the second lower partition wall 10 are sequentially provided above the main grate 5 along the movement direction of the main grate 5, the area between the lower partition wall and the main grate 5 is a fuel channel, and the area between the lower partition wall and the top arch 6 is a gas channel; the first lower partition wall 2 and the second lower partition wall 10 are independently provided with regulating air ducts;

[0083] The top arch 6 is provided with a first upper partition wall 9 and a second upper partition wall 14 extending toward the furnace in sequence along the gas flow direction, dividing the area above the lower partition wall into a gasification combustion zone 8, a transition combustion zone 13 and a burnout zone 17 respectively. The first upper partition wall 9 is laterally positioned between the first lower partition wall 2 and the second lower partition wall 10, and the second upper partition wall 14 is laterally positioned behind the second lower partition wall 10.

[0084] The first lower partition wall 2 is arranged above the front end of the main grate 5, and an adjusting gate is provided on the first lower partition wall 2; the distance from the bottom of the first lower partition wall 2 to the main grate 5 is greater than the distance from the second lower partition wall 10 to the main grate 5; the distance between the first lower partition wall 2 and the second lower partition wall 10 is 50% of the length of the main grate 5.

[0085] A first regulating air duct 3 is provided on the upper part of the first lower partition wall 2, and a first regulating air duct 3 is connected to a first regulating air nozzle 4; a second regulating air duct 11 is provided on the upper part of the second lower partition wall 10, and two second regulating air nozzles 12 are connected to the second regulating air duct 11.

[0086] The distance from the bottom of the first upper partition wall 9 to the main grate 5 is 2 / 3 of the distance from the top arch 6 to the main grate 5 , and the distance from the bottom of the second upper partition wall 14 to the main grate 5 is 4 / 5 of the distance from the top arch 6 to the main grate 5 .

[0087] A gasification and combustion zone wind chamber 7 is provided below the main grate 5 in an area between the first lower partition wall 2 and the second lower partition wall 10 ; a burnout zone wind chamber 15 is provided below the main grate 5 in an area behind the second lower partition wall 10 .

[0088] The burnout zone 17 is provided with a burnout air nozzle, and the burnout air nozzle is arranged at the lower part of the top arch 6.

[0089] Embodiment 3:

[0090] This embodiment provides a combustion method of a decoupled combustion mechanical grate furnace, which is performed in the mechanical grate furnace of Embodiment 1 and includes the following steps:

[0091] (1) The biomass fuel enters the pre-combustion device 1 for pre-combustion at a temperature of 600°C, and is pyrolyzed and gasified to generate semi-coke and pyrolysis gasification gas;

[0092] (2) The semi-coke generated in step (1) enters the main grate 5 and moves with the main grate 5 to generate a gasification and combustion reaction. During the semi-coke gasification and combustion process, air is introduced from the gasification and combustion zone wind chamber 7. The pyrolysis gasified coal gas generated in step (1) enters the gasification and combustion zone 8 and is mixed with the coal gas generated by the semi-coke gasification and combustion to perform reductive combustion. The combustion temperature is 900° C. A mixed gas composed of air and recycled flue gas is introduced into the gasification and combustion zone 8, and the excess air coefficient is 0.8. During the reductive combustion process, NO x is reduced to N2;

[0093] (3) The flue gas generated by the reducing combustion in step (2) enters the transition combustion zone 13 and is mixed with the coal gas generated at the rear of the gasification combustion zone 8 under ventilation conditions and is burned at a combustion temperature of 1000° C. A mixture of air and circulating flue gas is introduced into the transition combustion zone 13, and the excess air coefficient is 1.0; after the semi-coke in step (2) passes through the second lower partition wall 10, it is fully burned under the action of air introduced into the wind chamber 15 of the burnout zone to obtain solid slag, which is discharged from the slag discharge port 19;

[0094] (4) The flue gas generated after the mixed combustion in step (3) is fully burned under the action of excess air introduced from the burnout zone nozzle, with a burnout temperature of 1200° C. and an excess air coefficient of 1.5, and then leaves through the flue gas outlet 18.

[0095] In this embodiment, the mechanical grate furnace is used to carry out decoupled combustion of biomass fuel, and the combustion efficiency can reach 92%, and the NO in the flue gas is xThe content meets the emission requirements and no additional treatment is required.

[0096] Embodiment 4:

[0097] This embodiment provides a combustion method of a decoupled combustion mechanical grate furnace, which is performed in the mechanical grate furnace of Embodiment 1 and includes the following steps:

[0098] (1) Pulverized coal fuel enters the pre-combustion device 1 for pre-combustion at a temperature of 800°C, and is pyrolyzed and gasified to generate semi-coke and pyrolysis gasified coal gas;

[0099] (2) The semi-coke generated in step (1) enters the main grate 5 and moves with the main grate 5 to generate a gasification and combustion reaction. During the semi-coke gasification and combustion process, air is introduced from the gasification and combustion zone wind chamber 7. The pyrolysis gasified coal gas generated in step (1) enters the gasification and combustion zone 8 and is mixed with the coal gas generated by the semi-coke gasification and combustion to perform reductive combustion. The combustion temperature is 1100° C. A mixed gas composed of air and recycled flue gas is introduced into the gasification and combustion zone 8, and the excess air coefficient is 0.6. During the reductive combustion process, NO x is reduced to N2;

[0100] (3) The flue gas generated by the reducing combustion in step (2) enters the transition combustion zone 13, and is mixed with the coal gas generated at the rear of the gasification combustion zone 8 under ventilation conditions and burns at a combustion temperature of 1200° C. A mixed gas consisting of air and recycled flue gas is introduced into the transition combustion zone 13, and the excess air coefficient is 0.85; After the semi-coke in step (2) passes through the second lower partition wall 10, it is fully burned under the action of air introduced into the wind chamber 15 of the burnout zone to obtain solid slag, which is discharged from the slag discharge port 19;

[0101] (4) The flue gas generated after the mixed combustion in step (3) is fully burned under the action of excess air introduced from the burnout zone nozzle, with a burnout temperature of 1400° C. and an excess air coefficient of 1.8, and then leaves through the flue gas outlet 18.

[0102] In this embodiment, the mechanical grate furnace is used to carry out decoupled combustion of pulverized coal fuel, and the combustion efficiency can reach 94%, and NO in flue gas is x The content meets the emission requirements and no additional treatment is required.

[0103] Embodiment 5:

[0104] This embodiment provides a combustion method of a decoupled combustion mechanical grate furnace, which is performed in the mechanical grate furnace of Embodiment 2 and includes the following steps:

[0105] (1) The biomass fuel enters the pre-combustion device 1 for pre-combustion at a pre-combustion temperature of 500°C, and is pyrolyzed and gasified to generate semi-coke and pyrolysis gasification gas;

[0106] (2) The semi-coke generated in step (1) enters the main grate 5 and moves with the main grate 5 to generate a gasification and combustion reaction. During the semi-coke gasification and combustion process, air is introduced from the gasification and combustion zone wind chamber 7. The pyrolysis gasified coal gas generated in step (1) enters the gasification and combustion zone 8 and is mixed with the coal gas generated by the semi-coke gasification and combustion to perform reductive combustion. The combustion temperature is 800° C. A mixed gas composed of air and recycled flue gas is introduced into the gasification and combustion zone 8, and the excess air coefficient is 0.9. During the reductive combustion process, NO x is reduced to N2;

[0107] (3) The flue gas generated by the reducing combustion in step (2) enters the transition combustion zone 13, and is mixed with the coal gas generated at the rear of the gasification combustion zone 8 under ventilation conditions and burns at a combustion temperature of 800° C. A mixed gas consisting of air and recycled flue gas is introduced into the transition combustion zone 13, and the excess air coefficient is 1.05; after the semi-coke in step (2) passes through the second lower partition wall 10, it is fully burned under the action of air introduced into the wind chamber 15 of the burnout zone to obtain solid slag, which is discharged from the slag discharge port 19;

[0108] (4) The flue gas generated after the mixed combustion in step (3) is fully burned under the action of excess air introduced from the burnout zone nozzle, with a burnout temperature of 1100° C. and an excess air coefficient of 1.2, and then leaves through the flue gas outlet 18.

[0109] In this embodiment, the mechanical grate furnace is used to carry out decoupled combustion of biomass fuel, and the combustion efficiency can reach 91%, and NO in flue gas is x The content meets the emission requirements and no additional treatment is required.

[0110] Comparative Example 1:

[0111] This comparative example provides a decoupled combustion mechanical grate furnace, the structure of which refers to the structure in Example 1, with the only difference being that: no second lower partition wall 10 and its regulating air duct are arranged above the main grate, no second upper partition wall 14 is arranged on the top arch 6, and the division of the area above the lower partition wall does not include the transition combustion zone 13.

[0112] In this comparative example, since the mechanical grate furnace is not provided with a transition combustion zone, it is difficult to ensure the transition from the reducing atmosphere to the oxidizing atmosphere in the gas phase combustion zone, resulting in poor stability of the reducing atmosphere in the reducing combustion zone. x The reduction efficiency is low, and the NOx concentration is easy to rebound under the oxygen-rich condition in the burnout zone. x The content is relatively high and cannot meet emission standards.

[0113] Based on the above embodiments and comparative examples, it can be seen that the mechanical grate furnace of the present invention uses a pre-combustion device to perform preliminary pyrolysis and gasification of the fuel, so that the fuel can start to burn at the front end of the grate; the main furnace body is divided into different combustion zones, and different partition walls and regulating winds are set to improve the diffusion and mixing effect of the coal gas, flue gas and the regulating wind in the furnace. In the main conversion stage of the fuel nitrogen, the large-scale reducing combustion zone formed in the furnace is more stable, the composition is easier to control, and the transition from the reducing atmosphere to the oxidizing atmosphere is accurately controlled, reducing the NO in the burnout zone. x The rebound of concentration realizes the graded and zoned combustion of fuel, and the combustion efficiency can reach more than 90%; the design of the mechanical grate furnace improves the grate utilization and combustion efficiency, enhances the fuel adaptability, and reduces the flue gas recirculation volume and energy consumption.

[0114] The applicant declares that the present invention uses the above embodiments to illustrate the detailed devices and methods of the present invention, but the present invention is not limited to the above detailed devices and methods, that is, it does not mean that the present invention must rely on the above detailed devices and methods to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the device of the present invention, addition of auxiliary devices, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A decoupled combustion mechanical grate furnace, characterized in that: The mechanical grate furnace comprises a pre-combustion device and a main furnace body, wherein the outlet of the pre-combustion device is connected to the inlet of the main furnace body; the main furnace body comprises a main grate, a top arch, a rear wall and a furnace surrounded by the main grate, the top arch and the rear wall, the pre-combustion device is located above the front of the main grate, the top arch is located above the main grate, the rear wall is located above the rear of the main grate, a slag discharge port is provided between the lower part of the rear wall and the rear of the main grate, and a smoke outlet is provided between the upper part of the rear wall and the rear of the top arch; The rear wall is provided with a rear arch extending into the furnace, the rear arch divides the rear part of the furnace into two parts, the upper and lower parts, and separates the slag discharge port and the smoke outlet; the first lower partition wall and the second lower partition wall are arranged in sequence above the main grate along the movement direction of the main grate, the area between the lower partition wall and the main grate is a fuel channel, and the area between the lower partition wall and the top arch is a gas channel; the first lower partition wall and the second lower partition wall are independently provided with regulating air ducts; The first upper partition wall and the second upper partition wall extending toward the furnace are arranged in sequence on the top arch along the gas flow direction, and the area above the lower partition wall is divided into a gasification combustion zone, a transition combustion zone and a burnout zone respectively. The lateral position of the first upper partition wall is located between the first lower partition wall and the second lower partition wall, and the lateral position of the second upper partition wall is located behind the second lower partition wall; the first lower partition wall is arranged above the front end of the main grate, and an adjusting gate is arranged on the first lower partition wall.

2. The mechanical grate furnace according to claim 1, characterized in that: The front section of the top arch is connected to the upper part of the pre-combustion device.

3. The mechanical grate furnace according to claim 1, characterized in that: The distance from the bottom of the first lower partition wall to the main grate is greater than the distance from the second lower partition wall to the main grate.

4. The mechanical grate furnace according to claim 1, characterized in that: The distance between the first lower partition wall and the second lower partition wall is 50-75% of the length of the main grate.

5. The mechanical grate furnace according to claim 1, characterized in that: A first regulating air duct is provided at the upper portion of the first lower partition wall, and the first regulating air duct is connected to at least one first regulating air nozzle.

6. The mechanical grate furnace according to claim 1, characterized in that: A second regulating air duct is provided at the upper portion of the second lower partition wall, and the second regulating air duct is connected to at least one second regulating air nozzle.

7. The mechanical grate furnace according to claim 1, characterized in that: The distance from the bottom of the first upper partition wall to the main grate is 1 / 3 to 2 / 3 of the distance from the top arch to the main grate.

8. The mechanical grate furnace according to claim 1, characterized in that: The distance from the bottom of the second upper partition wall to the main grate is 1 / 2 to 4 / 5 of the distance from the top arch to the main grate.

9. The mechanical grate furnace according to claim 1, characterized in that: A gasification and combustion zone wind chamber is provided below the main grate in an area corresponding to the first lower partition wall and the second lower partition wall.

10. The mechanical grate furnace according to claim 1, characterized in that: A burnout zone air chamber is provided below the main grate and in the area corresponding to the rear of the second lower partition wall.

11. The mechanical grate furnace according to claim 10, characterized in that: The burnout zone is provided with a burnout air nozzle, and the burnout air nozzle is arranged at the lower part of the top arch, the front end of the rear arch or the side wall of the furnace.

12. A method for decoupled combustion using the mechanical grate furnace according to any one of claims 1 to 11, characterized in that: The method comprises the following steps: (1) Pre-combustion of solid fuel, pyrolysis and gasification to generate semi-coke and pyrolysis gasification gas; (2) the semi-coke generated in step (1) enters the main grate and moves with the main grate to undergo a gasification and combustion reaction; the pyrolysis gasified coal gas generated in step (1) enters the gasification and combustion zone and is mixed with the coal gas generated by the gasification and combustion of the semi-coke to undergo a reducing combustion reaction; (3) The flue gas generated by the reducing combustion in step (2) enters the transition combustion zone and is mixed and burned with the coal gas generated at the rear of the gasification combustion zone under ventilation conditions; after the semi-coke in step (2) passes through the second lower partition wall, it is fully burned under the action of the gas to obtain solid slag; (4) The flue gas generated after the mixed combustion in step (3) is fully burned under the action of excess air and then leaves through the flue gas outlet.

13. The method according to claim 12, characterized in that The solid fuel in step (1) includes coal and / or biomass.

14. The method according to claim 12, characterized in that The pre-combustion in step (1) is carried out in a pre-combustion device.

15. The method according to claim 14, characterized in that The pre-combustion device adopts a bottom ignition mode for combustion.

16. The method according to claim 12, characterized in that During the semi-coke gasification and combustion process in step (2), air is introduced from the wind chamber of the gasification and combustion zone.

17. The method according to claim 12, characterized in that In step (2), a mixed gas consisting of air and circulating flue gas is introduced into the gasification combustion zone.

18. The method according to claim 17, characterized in that The mixed gas is introduced through the first regulating air duct.

19. The method according to claim 12, characterized in that In the reducing combustion process of step (2), NO x is reduced to N2.

20. The method according to claim 12, characterized in that The excess air coefficient of the gasification combustion zone in step (2) is 0.6 to 0.

95.

21. The method according to claim 12, characterized in that In step (3), a mixture of air and recycled flue gas is introduced into the transition combustion zone.

22. The method according to claim 21, characterized in that The mixed gas is introduced through the second regulating air duct.

23. The method according to claim 12, characterized in that The excess air coefficient of the transition combustion zone in step (3) is 0.85 to 1.

1.

24. The method according to claim 12, characterized in that In step (3), the semi-coke thickness after passing through the second lower partition wall is less than the semi-coke thickness before the second lower partition wall.

25. The method according to claim 12, characterized in that During the semi-coke burnout process in step (3), air is introduced from the wind chamber of the burnout zone.

26. The method according to claim 12, characterized in that The air in step (4) is introduced from the nozzle of the burnout zone.

27. The method according to claim 12, characterized in that The excess air coefficient of the burnout zone in step (4) is 1.05 to 2.

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