Combustion system and method for a biomass bulk boiler coupled with chamber combustion and layer combustion

Abstract

This invention provides a combustion system and method for a biomass bulk boiler with coupled chamber combustion and stoker combustion. The system includes a boiler with a furnace at the top and a reciprocating grate at the bottom. A distributor is installed at the feed inlet at the front of the furnace. A tail flue is connected to the flue gas outlet at the top of the furnace. An economizer and an air preheater are connected in series on the tail flue. The air preheater has a primary cold air inlet and a secondary cold air inlet. A primary air fan is connected to the primary air inlet and connects to the distributor after heat absorption by the air preheater. A secondary air fan is connected to the secondary air inlet and connects to the reciprocating grate after heat absorption by the air preheater. This invention simplifies the biomass processing by coupling fine-particle chamber combustion with coarse-particle chamber combustion and stoker combustion, improving boiler combustion efficiency, reducing furnace combustion temperature, and reducing nitrogen oxide emissions. High-temperature supplementary combustion air is provided to the distributor and reciprocating grate through secondary heat exchange utilization of the high-temperature flue gas.

Description

Technical Field

[0001] This invention belongs to the field of combustion equipment technology, and relates to a hybrid combustion boiler, particularly a biomass bulk boiler combustion system and method that couples chamber combustion and stoker combustion. Background Technology

[0002] Traditional chain grate boilers employ a single "layer combustion" method. Biomass is drawn into the furnace from the hopper at the front of the grate through a material gate, forming a layer of material of a certain thickness on the grate surface. As the grate moves, it completes the preheating, ignition, combustion, and burnout processes, finally falling into the ash chamber from the rear of the grate. Modern circulating fluidized bed boilers, on the other hand, employ a single "chamber combustion" fluidized bed combustion method. Biomass is crushed into a certain particle size by a crusher, then granulated into particles of a specific size. These particles are fed into the dense phase zone of the furnace through a feed pipe, where they undergo fluidized bed combustion, completing the entire combustion process from drying, ignition, combustion, and burnout. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a combined combustion system and method for biomass bulk boilers that utilizes chamber combustion as the primary method and stoker combustion as a secondary method, thereby optimizing combustion performance and promoting environmental protection.

[0004] The objective of this invention can be achieved through the following technical solution: a biomass bulk boiler combustion system with coupled chamber combustion and stoker combustion, comprising a combustion boiler, wherein the upper part of the combustion boiler is a furnace and the lower part is a reciprocating grate, a material distributor is provided on the feed inlet at the front of the furnace, the flue gas outlet at the top of the furnace is connected to the tail flue, the tail flue is sequentially connected to an economizer and an air preheater, the air preheater has a primary air inlet and a secondary air inlet, a primary air fan is connected to the primary air inlet, the primary air fan is connected to the material distributor after absorbing heat from the air preheater, a secondary air fan is connected to the secondary air inlet, the secondary air fan is connected to the reciprocating grate after absorbing heat from the air preheater.

[0005] In the above-mentioned combustion system of a biomass bulk boiler with coupled chamber combustion and stoker combustion, the distributor is connected to the feed pipe, the outer end of the feed pipe is connected to the blower, the middle of the feed pipe is connected to the discharge hopper, and the top of the discharge hopper is connected to the feed hopper.

[0006] In the aforementioned biomass bulk boiler combustion system that combines chamber combustion and stoker combustion, the reciprocating grate is composed of several stages of grate bars connected together. These grate bars are arranged in a descending manner from back to front, and the grate rotates from the rear wall of the furnace to the front wall. Adjacent grate bars are connected by transmission rods, which are connected by a drive mechanism.

[0007] In the above-mentioned biomass bulk boiler combustion system with coupled chamber combustion and stoker combustion, the reciprocating grate is divided into several combustion zones by several grate bars, and the secondary heat absorption air supply pipe is connected to several branch pipes at its end. The several branch pipes are connected to the several combustion zones one by one.

[0008] In the above-mentioned biomass bulk boiler combustion system with coupled chamber combustion and stoker combustion, the reciprocating grate is divided into a front section, a middle section, and a rear section from front to back. The middle section and the rear end of the reciprocating grate are connected to the furnace to form a top-to-bottom material drop port.

[0009] A combustion method for a biomass bulk boiler that combines chamber combustion and stoker combustion includes the following steps:

[0010] 1) Pile wood sprayed with diesel fuel on the reciprocating grate, and then directly ignite the wood pile to provide a combustion flame to reach the combustion temperature of the biomass material;

[0011] 2) Pour the bulk biomass into the feed hopper and transfer it to the discharge hopper. Turn on the blower to blow the bulk biomass to the distributor under high pressure through the feed pipe.

[0012] 3) The biomass bulk material is evenly injected into the furnace through the distributor. First, the fine particles in the biomass bulk material are completely burned in the furnace space, while the coarse particles are not completely burned in the furnace space.

[0013] 4) Unburned coarse particles in the biomass bulk material fall into the middle and rear part of the reciprocating grate, and undergo stratified combustion as the reciprocating grate moves from back to front, ensuring that the coarse particles are completely burned.

[0014] 5) The stoker combustion on the reciprocating grate located at the front wall of the furnace increases the combustion temperature at the outlet of the feeder, which helps the fuel to combust in the chamber at the outlet of the feeder.

[0015] 6) The high-temperature flue gas generated after the combustion of biomass bulk materials enters the tail flue through the heating surface of the combustion boiler, and then passes through the economizer and air preheater for heat exchange before entering the tail flue gas treatment equipment.

[0016] 7) The air blown in by the primary blower is heated by the air preheater and then enters the material distributor, serving as high-temperature supplementary combustion air for the particle combustion chamber in the furnace.

[0017] 8) The air blown in by the secondary air fan is heated by the air preheater and then divided into several air compartments to enter each combustion zone of the reciprocating grate evenly, serving as high-temperature supplementary combustion air for coarse particle stratification combustion on the reciprocating grate.

[0018] In the above-mentioned combustion method of biomass bulk boiler with coupled chamber combustion and stoker combustion, the biomass bulk material is specifically bamboo powder, wood shavings, fine wood and / or rice husks.

[0019] In the above-mentioned combustion method of biomass bulk boiler with coupled chamber combustion and stoker combustion, the particle size of the biomass bulk material is less than 15 mm and the thickness is less than 5 mm.

[0020] In the above-mentioned combustion method of biomass bulk boiler with coupled chamber combustion and stoker combustion, the combustion temperature of the furnace is 950-1000℃ and the combustion time is greater than 2 seconds.

[0021] In the above-mentioned combustion method for biomass bulk boilers that combines chamber combustion and stoker combustion, chamber combustion in the furnace is the primary combustion mode, while stoker combustion on the reciprocating grate is the secondary combustion mode.

[0022] Compared with existing technologies, the combustion system and method of this biomass bulk boiler with coupled chamber combustion and stoker combustion have the following advantages:

[0023] 1. By combining chamber combustion and stoker combustion, the processing technology of biomass raw materials is simplified. The crushed biomass raw materials do not need to be granulated again and can be directly put into the boiler for combustion, reducing granulation costs and environmental pollution.

[0024] 2. By coupling the combustion of fine particles in the chamber with the combustion of unburned coarse particles in the strata, the combustion efficiency of the boiler is improved, the combustion temperature in the furnace is reduced, and the emission of nitrogen oxides is reduced.

[0025] 3. By enhancing combustion, the combustion is more complete, the carbon content of the slag is significantly reduced, and the heat loss from incomplete combustion of gases and solids is reduced, thereby improving the boiler's thermal efficiency.

[0026] 4. The combustion mode, which is mainly based on chamber combustion, is achieved by coupling fine particulate combustion with unburned coarse particulate combustion. This is beneficial for the mixing of fuel and air and reduces the excess air coefficient in the flue gas.

[0027] 5. By utilizing the secondary heat exchange of high-temperature flue gas, a circulating system is used to provide high-temperature supplementary combustion air to the material distributor and reciprocating grate, thereby reducing heat emissions and saving energy consumption, which is in line with the concept of environmental protection. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the combustion system of a biomass bulk boiler that couples chamber combustion and stoker combustion.

[0029] In the diagram, 1 is the blowing fan; 2 is the feed hopper; 3 is the discharge hopper; 4 is the material distributor; 5 is the furnace; 6 is the reciprocating grate; 7 is the economizer; 8 is the air preheater; 9 is the primary air fan; and 10 is the secondary air fan. Detailed Implementation

[0030] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0031] like Figure 1 As shown, the combustion system of this biomass bulk boiler, which is coupled with chamber combustion and stoker combustion, includes a combustion boiler. The upper part of the combustion boiler is the furnace 5, and the lower part is the reciprocating grate 6. A distributor 4 is installed on the feed inlet at the front of the furnace 5. The flue gas outlet at the top of the furnace 5 is connected to the tail flue. An economizer 7 and an air preheater 8 are connected in series on the tail flue. The air preheater 8 has a primary air inlet and a secondary air inlet. A primary air fan 9 is connected to the primary air inlet. The primary air fan 9 is connected to the distributor 4 through the heat absorption port of the air preheater 8. A secondary air fan 10 is connected to the secondary air inlet. The secondary air fan 10 is connected to the reciprocating grate 6 through the heat absorption port of the air preheater 8.

[0032] In this biomass bulk boiler combustion system that combines chamber combustion and stoker combustion, the air preheater 8 is a horizontal structure with flue gas flowing outside the tubes and air flowing inside the tubes to prevent ash in the biomass flue gas from coking or sticking inside the tubes.

[0033] The distributor 4 is connected to the feed pipe, the outer end of which is connected to the blower 1. The middle of the feed pipe is connected to the discharge hopper 3, and the top of the discharge hopper 3 is connected to the feed hopper 2. The blower 1 is specifically a Roots blower. The distributor 4 serves to evenly disperse the biomass into the furnace.

[0034] The reciprocating grate 6 consists of several levels of grate bars connected together. These grate bars are arranged in descending order from back to front, rotating from the rear wall of the furnace to the front wall. Adjacent grate bars are connected by a transmission rod, which is connected by a drive mechanism. The reciprocating grate 6 is a mature boiler auxiliary machine and belongs to existing technology, so it will not be described in detail here.

[0035] The reciprocating grate 6 is divided into several combustion zones by several grate bars. The secondary heat absorption air supply pipes are connected to several branch pipes at their ends, and these branch pipes are connected to the combustion zones one by one. By setting up branch pipes, air supply operations are performed synchronously to different combustion zones, thereby making the air distribution on the entire reciprocating grate 6 uniform and facilitating the complete combustion of biomass bulk materials.

[0036] The reciprocating grate 6 is divided into a front section, a middle section, and a rear section from front to back. The middle section and the rear end of the reciprocating grate 6 are connected to the furnace 5 to form a top-to-bottom feeding port. Unburned coarse fuel particles in the furnace 5 fall from the feeding port to the middle and rear sections of the reciprocating grate 6 to continue burning.

[0037] A combustion method for a biomass bulk boiler that combines chamber combustion and stoker combustion includes the following steps:

[0038] 1) Pile wood sprayed with diesel fuel on the reciprocating grate 6, and then directly ignite the wood pile to provide a combustion flame, reach the combustion temperature of biomass materials, and increase the furnace temperature.

[0039] 2) Pour the biomass bulk material into the feed hopper 2 and transfer it to the discharge hopper 3. Turn on the blower 1 and blow the biomass bulk material to the distributor 4 under high pressure through the feed pipe.

[0040] 3) Biomass bulk material is evenly injected into the furnace 5 through the distributor 4. First, it undergoes chamber combustion to ensure that the fine particles in the biomass bulk material are completely burned in the furnace 5 space, and the coarse particles are not completely burned in the furnace 5 space.

[0041] 4) Unburned coarse particles in the biomass bulk material fall into the middle and rear part of the reciprocating grate 6, and undergo stratified combustion as the reciprocating grate 6 moves from back to front, ensuring that the coarse particles are completely burned.

[0042] 5) The stratified combustion on the reciprocating grate 6 located at the front wall of the furnace 5 increases the combustion temperature at the outlet of the distributor 4, which helps the combustion of fuel at the outlet of the distributor 4.

[0043] 6) The high-temperature flue gas generated after the combustion of biomass bulk materials enters the tail flue through the heating surface of the combustion boiler, and then passes through the economizer 7 and air preheater 8 for heat exchange before entering the tail flue gas treatment equipment.

[0044] 7) The airflow blown in by the primary blower 9 is heated by the air preheater 8 and then enters the distributor 4, serving as the high-temperature supplementary combustion air for the fuel pellet combustion in the furnace 5.

[0045] 8) The airflow blown in by the secondary air fan 10 is heated by the air preheater 8 and then divided into several air compartments to enter each combustion zone of the reciprocating grate 6 evenly, serving as high-temperature supplementary combustion air for coarse particle stratification combustion on the reciprocating grate 6.

[0046] Bulk biomass materials specifically include bamboo powder, wood shavings, fine wood particles, and / or rice husks, etc. The combustion performance of different bulk biomass materials can be considered consistent.

[0047] The particle size of the biomass bulk material is less than 15mm and the thickness is less than 5mm.

[0048] The combustion temperature in furnace 5 is 950-1000℃, and the combustion time is greater than 2 seconds.

[0049] The combustion chamber combustion in furnace 5 is the main combustion method, while the stoker combustion on the reciprocating grate 6 is the auxiliary combustion method.

[0050] Compared with existing technologies, the combustion system and method of this biomass bulk boiler with coupled chamber combustion and stoker combustion have the following advantages:

[0051] 1. By combining chamber combustion and stoker combustion, the processing technology of biomass raw materials is simplified. The crushed biomass raw materials do not need to be granulated again and can be directly put into the boiler for combustion, reducing granulation costs and environmental pollution.

[0052] 2. By coupling the combustion of fine particles in the chamber with the combustion of unburned coarse particles in the strata, the combustion efficiency of the boiler is improved, the combustion temperature in the furnace is reduced, and the emission of nitrogen oxides is reduced.

[0053] 3. By enhancing combustion, the combustion is more complete, the carbon content of the slag is significantly reduced, and the heat loss from incomplete combustion of gases and solids is reduced, thereby improving the boiler's thermal efficiency.

[0054] 4. The combustion mode, which is mainly based on chamber combustion, is achieved by coupling fine particulate combustion with unburned coarse particulate combustion. This is beneficial for the mixing of fuel and air and reduces the excess air coefficient in the flue gas.

[0055] 5. By utilizing the secondary heat exchange of high-temperature flue gas, a circulating system is used to provide high-temperature supplementary combustion air to the distributor 4 and reciprocating grate 6, thereby reducing heat emissions and saving energy consumption, which is in line with the concept of environmental protection.

[0056] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

[0057] Although this document frequently uses terms such as blowing fan 1, feed hopper 2, discharge hopper 3, material distributor 4, furnace 5, reciprocating grate 6, economizer 7, air preheater 8, primary air fan 9, and secondary air fan 10, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention.

[0058] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

Claims

1. A combustion method for a biomass bulk boiler with coupled chamber combustion and stoker combustion, the method being applied to a combustion boiler, wherein the upper part of the combustion boiler is a furnace, the lower part is a reciprocating grate, a distributor is installed at the feed inlet at the front of the furnace, the flue gas outlet at the top of the furnace is connected to a tail flue, the tail flue is sequentially connected to an economizer and an air preheater, the air preheater has a primary air inlet and a secondary air inlet, a primary air fan is connected to the primary air inlet, the primary air fan is connected to the distributor after absorbing heat from the air preheater, and a secondary air fan is connected to the secondary air inlet, the secondary air fan is connected to the distributor after absorbing heat from the air preheater. The reciprocating grate is composed of several grate plates connected together. These grate plates are arranged in descending order from back to front, and move from the rear wall of the boiler to the front wall. Adjacent grate plates are connected by a transmission rod, which is connected by a drive mechanism. The several grate plates of the reciprocating grate are divided into several combustion zones. The end of the secondary heat absorption air supply pipe is connected to several branch pipes, and each branch pipe is connected to one of the combustion zones. The reciprocating grate is divided into a front section, a middle section, and a rear section from front to back. The middle section and the rear section of the reciprocating grate are connected to the furnace to form a top-to-bottom material discharge port. Its features are, The method includes the following steps: 1) Pile wood sprayed with diesel fuel on the reciprocating grate, and then directly ignite the wood pile to provide a combustion flame to reach the combustion temperature of the biomass material; 2) Pour the bulk biomass into the feed hopper and transfer it to the discharge hopper. Turn on the blower to blow the bulk biomass to the distributor under high pressure through the feed pipe. 3) The biomass bulk material is evenly injected into the furnace through the distributor. First, the fine particles in the biomass bulk material are completely burned in the furnace space, while the coarse particles are not completely burned in the furnace space. 4) Unburned coarse particles in the biomass bulk material fall into the middle and rear part of the reciprocating grate, and undergo stratified combustion as the reciprocating grate moves from back to front, ensuring that the coarse particles are completely burned. 5) The stoker combustion on the reciprocating grate located on the front wall of the furnace increases the combustion temperature at the outlet of the feeder, which helps the fuel to combust in the chamber at the outlet of the feeder. 6) The high-temperature flue gas generated after the combustion of biomass bulk materials enters the tail flue through the heating surface of the combustion boiler, and then passes through the economizer and air preheater for heat exchange before entering the tail flue gas treatment equipment. 7) The air blown in by the primary blower is heated by the air preheater and then enters the material distributor to serve as high-temperature supplementary combustion air for the particle combustion chamber in the furnace. 8) The airflow blown in by the secondary air fan is heated by the air preheater and then divided into several air compartments to enter each combustion zone of the reciprocating grate evenly, serving as high-temperature supplementary combustion air for coarse particle stratification on the reciprocating grate.

2. The combustion method for a biomass bulk boiler with coupled chamber combustion and stoker combustion as described in claim 1, characterized in that, The material distributor is connected to the feed pipe, the outer end of the feed pipe is connected to the blower, the middle of the feed pipe is connected to the discharge hopper, and the top of the discharge hopper is connected to the feed hopper.

3. The combustion method for a biomass bulk boiler with coupled chamber combustion and stoker combustion as described in claim 1, characterized in that, The biomass bulk materials specifically include bamboo powder, wood shavings, fine wood, and / or rice husks.

4. The combustion method for a biomass bulk boiler with coupled chamber combustion and stoker combustion as described in claim 1, characterized in that, The biomass bulk material has a particle size of less than 15 mm and a thickness of less than 5 mm.

5. The combustion method for a biomass bulk boiler with coupled chamber combustion and stoker combustion as described in claim 1, characterized in that, The combustion temperature in the furnace is 950–1000°C, and the combustion time is greater than 2 seconds.

6. The combustion method for a biomass bulk boiler with coupled chamber combustion and stoker combustion as described in claim 1, characterized in that, The combustion chamber combustion within the furnace is the primary combustion mode, while the stoker combustion on the reciprocating grate is the secondary combustion mode.

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