Combustion method of low calorific value organic matter

Abstract

The present invention relates to the field of low calorific value organic matter, and specifically to a method for burning low calorific value organic matter, the method comprising: (1) drying and optionally grinding the low calorific value organic matter to obtain a first material, and dividing the first material into a portion A and a portion B; (2) contacting the portion A with a gasifying agent to undergo a gasification reaction to obtain a combustible gas and a second solid material; (3) contacting the portion B and the second solid material with the combustible gas to undergo combustion; wherein the portion A accounts for more than 30% by weight of the first material. The methods of the present invention can work together to achieve stable, continuous, and efficient combustion, not only solving the problem of effective utilization of low calorific value organic matter, but also solving the problem of low calorific value organic matter being difficult to directly and stably burn in a pulverized coal boiler. At the same time, there is no need to use additional auxiliary fuel (such as diesel) in a traditional boiler combustion-supporting system, which can effectively reduce operating costs.

Description

Technical Field

[0001] The invention relates to the field of low calorific value organic matter, and in particular to a combustion method of low calorific value organic matter. Background Art

[0002] With the rapid development of industrial technology, the consumption of high-calorific-value fuels has increased year by year, while reserves have gradually decreased. At the same time, the efficient utilization of low-calorific-value organic matter (such as low-calorific-value fuels and low-calorific-value biomass) has not been completely resolved. As people's attention to resources and the environment gradually increases, how to process and fully utilize low-calorific-value organic matter has received increasing attention and has become a focus of researchers at home and abroad.

[0003] Currently, the most common way to utilize low-calorific-value organic matter is to directly burn it in a boiler. However, due to its inherent characteristics, such as low calorific value and high moisture content, direct combustion in a boiler can cause the system to stall or require additional auxiliary fuel. Therefore, finding a way to efficiently and stably burn low-calorific-value organic matter using existing boiler equipment is a major technical challenge.

[0004] CN105001915A discloses a method for converting waste organic matter into clean fuel gas. This method sorts, crushes, and homogenizes domestic garbage and waste organic matter, and then sprays them into a decomposition furnace through a multifunctional nozzle with coal powder (or water-coal slurry), oxygen, and water to complete fuel, heat release, and gasification. The generated combustible gas is transported to the fuel gas purification system for purification. The purified gas is then sent to the fuel gas storage system for downstream civil and industrial use, and can also provide raw gas for methanol production. This patent application only provides a method for producing fuel gas from waste organic matter, but does not address how to deal with its solid products.

[0005] CN106244239A discloses a process for producing synthetic natural gas from waste gasification. This method involves feeding the raw waste into a gasifier through a feed system for high-temperature gasification, producing crude syngas and high-temperature slag. After dust removal and scrubbing, the crude syngas enters a gasification purification system for purification. After CO conversion and acid gas removal, refined syngas is produced. The refined syngas is then processed through a methanogenic process and a natural gas purification process to produce qualified natural gas. This patent application only describes a method for producing refined syngas from waste gasification. It does not provide any technical description of how to treat the gasified slag, nor does it address technologies related to coupling waste gasification with combustion.

[0006] "Feasibility Study on Plasma Gasification for Boiler Ignition and Stable Combustion" (Environmental Engineering, 2019, Volume 37 Supplement) discloses a plasma gasification ignition and stable combustion system. The plasma gasifier is the core equipment of the entire system, including the plasma gasifier body, plasma ignition torch, gasifier nozzle and other equipment. Plasma gasification ignition efficiently gasifies fossil fuels such as coal in a plasma environment, and then passes them into a coal-fired boiler for combustion, thereby replacing fuel oil to achieve boiler ignition and stable combustion. This technology proposes a new type of ignition and stable combustion system, but there are the following problems: the plasma ignition system equipment is complex, the investment cost is high, the adaptability is poor, and it is prone to failure. When the operating conditions change, the pulverized coal gas flow is not easy to ignite, and the system operation is unreliable. In addition, the plasma in the plasma ignition system has high temperature and high energy, and the coal powder is prone to coking at the plasma ignition torch. After coking, the ignition effect is weakened, resulting in system instability. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defects in the prior art that low calorific value organic matter, due to its own characteristics such as low calorific value and high moisture content, directly transporting it to a combustion boiler will cause the system to stall or require additional auxiliary fuel for combustion. A combustion method for low calorific value organic matter is provided. The combustion method can increase the calorific value density of the low calorific value organic matter, ensure smooth combustion of the fuel, and achieve efficient and stable combustion without the need for additional auxiliary fuel.

[0008] In order to achieve the above object, the present invention provides a method for burning low calorific value organic matter, the method comprising:

[0009] (1) drying and optionally grinding a low calorific value organic matter to obtain a first material, and dividing the first material into a part A and a part B;

[0010] (2) contacting the portion A with a gasifying agent to perform a gasification reaction to obtain a combustible gas and a second solid material;

[0011] (3) contacting the portion B and the second solid material with the combustible gas for combustion;

[0012] Wherein, the portion A accounts for more than 30 weight % of the first material.

[0013] Preferably, the gasification reaction is carried out in a gasifier.

[0014] Preferably, the method further comprises: pyrolyzing the dried material to obtain pyrolysis gas and pyrolysis solid; and subjecting the pyrolysis solid to the optional grinding described in step (1).

[0015] The present invention couples the drying, gasification and combustion processes, especially the above steps (2) and (3), through the above technical scheme, and reasonably distributes part A and part B of the first material for gasification and combustion respectively, wherein the second solid material that has not been completely gasified is mixed with part B and then combined with combustible gas, as well as other technical features, which can cooperate with each other to convert low calorific value organic matter into part B and the second solid material with higher calorific value density, and make full use of the generated combustible gas to assist combustion, ultimately achieving stable, continuous and efficient combustion.

[0016] The present invention not only solves the problem of effective utilization of low calorific value organic matter, but also solves the difficult problem of low calorific value organic matter being difficult to burn directly and stably in a pulverized coal boiler. There is no need to carry out a separate subsequent process for the gasified slag (i.e., the second solid material), and there is no need to use additional auxiliary fuel (such as diesel) in the traditional boiler combustion-supporting system, which can effectively reduce operating costs.

[0017] The combustion method of the present invention rationally distributes part A and part B, ensuring that the combustible gas generated by part A can be fully and stably burned after being mixed with part B and the unreacted second solid material. This method fully utilizes low-calorific-value organic matter without the need for additional auxiliary fuel, achieving efficient and stable combustion and a stable and reliable system.

[0018] In a preferred embodiment of the present invention, the present invention can be applied to a gasifier (which has strict requirements on particle size and water content), thereby achieving efficient and stable combustion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0021] The present invention provides a method for burning low calorific value organic matter, the method comprising:

[0022] (1) drying and optionally grinding a low calorific value organic matter to obtain a first material, and dividing the first material into a part A and a part B;

[0023] (2) contacting the portion A with a gasifying agent to perform a gasification reaction to obtain a combustible gas and a second solid material;

[0024] (3) contacting the portion B and the second solid material with the combustible gas for combustion;

[0025] Wherein, the portion A accounts for more than 30 weight % of the first material.

[0026] Preferably, the portion A accounts for 30-90 wt %, more preferably 30-50 wt %, of the first material.

[0027] In the present invention, the low calorific value organic matter has a conventional meaning in the art, and the calorific value of the low calorific value organic matter is generally below 4500 kJ / kg. The low calorific value organic matter can be a low calorific value fuel or a low calorific value biomass, specifically, at least one of domestic waste, medical waste, and straw-based biomass.

[0028] In the present invention, preferably, in step (1), the drying is performed so that the moisture content of the dried material is less than 5% by weight, preferably 2-5% by weight. It is understood that the dried material can be the first material. Using the preferred embodiment of the present invention, the first material can be better subjected to subsequent gasification reaction and combustion at low energy consumption.

[0029] In the present invention, the drying is performed in a drying unit. Those skilled in the art can process the moisture in the gas phase obtained by the drying according to needs, for example, by condensing it through a subsequent processing unit. This is a prior art and will not be described in detail here.

[0030] According to the present invention, the grinding is performed in step (1). Specifically, those skilled in the art may choose to perform the drying first and then the grinding, or may perform the grinding first and then the drying. Preferably, the dried material is ground.

[0031] Preferably, the grinding process reduces the size of the first material to less than 200 mesh. Using the preferred embodiment of the present invention, the portion A of a specific size facilitates a better gasification reaction, generating more combustible gas to promote subsequent combustion. Furthermore, the portion B of a specific size further promotes contact with the second solid material and the combustible gas, thereby further promoting efficient and stable combustion of portion B and the second solid material.

[0032] According to a preferred embodiment of the present invention, in step (2), the molar ratio of the portion A to the gasifying agent is 1: 1. Under this preferred embodiment, the portion A can be converted into combustible gas as much as possible.

[0033] In the present invention, those skilled in the art can freely select the type of gasifying agent, as long as it can convert as much of Part A as possible into combustible gas while being environmentally friendly. Preferably, the gasifying agent is an oxygen-containing gas. Those skilled in the art can freely select the oxygen concentration in the oxygen-containing gas as needed. Preferably, the oxygen-containing gas is oxygen.

[0034] In the present invention, the conditions of the gasification reaction not only need to convert part A into combustible gas, but also need to consider the full and effective utilization of part A, that is, the efficient conversion of combustible gas; based on this, preferably, the conditions of the gasification reaction include: a temperature of 1200-1500°C, more preferably 1300-1400°C, and a reaction time of less than 10s.

[0035] In the present invention, preferably, the combustible gas is a gas containing at least one of CO, H2, and CH4. In the present invention, there is no limitation on the content of the at least one of CO, H2, and CH4 in the combustible gas, as long as the combustible gas produced by the gasification reaction can be used for subsequent combustion. Preferably, the CO content in the combustible gas is greater than the H2 content, and the H2 content is greater than the CH4 content.

[0036] In the present invention, the combustible gas generated by the gasification reaction is directly used in the subsequent combustion process. On the one hand, the combustion-supporting gas (i.e., at least one of CO, H2 and CH4) in the combustible gas is used to smoothly ignite and stably support the combustion of the part B and the second solid material. On the other hand, other impurities in the combustible gas can be further converted into combustible substances, thereby improving the utilization rate of low calorific value organic matter. In the prior art, the gas is usually purified before being used in other fields.

[0037] According to the present invention, preferably, the gasification reaction is carried out in a gasifier. The method of the present invention can be applied to gasifiers with strict material requirements, thereby achieving efficient and stable combustion.

[0038] More preferably, the gasification reaction is carried out in a flat-flame gasifier. This flat-flame gasifier is conventional technology, and can be, for example, the gasification unit disclosed in CN111349463A or CN111349464A. This is an entrained-flow gasification system that utilizes a flat-flame gasification burner. The flat-flame gasification burner includes multiple burner units, each of which mixes and ignites a gasifying agent and a gasification feedstock (i.e., a first material) through impact. The number of burner units is ≥3. For example, if the number of burner units is 3, three burner units are evenly spaced 120° across the top of the gasifier. This type of burner features a fast gasification reaction rate, a short flame, a short reaction residence time, a small space requirement for the gasification reaction, high process heat, and high coal adaptability. This gasifier not only easily miniaturizes to reduce costs, but also efficiently gasifies low-calorific-value organic matter and produces as much combustible gas as possible, effectively compensating for the insufficient calorific value of fuel in the boiler. Furthermore, by increasing the load in the combustion (e.g., boiler), the entire system achieves dynamic balance, ensuring stable operation. Compared to conventional high-temperature gasification using a plasma gun, this gasifier significantly reduces energy consumption and costs.

[0039] According to a specific embodiment of the present invention, the combustible gas and the second solid material produced by the gasification reaction can be directly used in whole or in part for the combustion in step (3). Preferably, in step (3), the weight ratio of the portion B to the second solid material is 1-15:1, more preferably 5-10:1, and even more preferably 5-7:1. The preferred embodiment of the present invention can ensure smooth ignition and stable combustion while further promoting the efficient combustion of the portion B.

[0040] Preferably, the amount of the combustible gas is such that the heat load of the combustible gas is more than 35% of the total heat load of the combustion. It is understood that the total heat load of the combustion refers to the sum of the heat loads of the various materials required to achieve continuous combustion of the device.

[0041] In the present invention, the second solid material includes carbon residue. In the present invention, the second solid material is used in the combustion of step (3) to improve the utilization rate of low calorific value organic matter.

[0042] In the present invention, there is no limit to the combustion time, as long as the material can be burned, and those skilled in the art can freely choose according to actual needs. The method of the present invention can fully and efficiently burn low calorific value organic matter in a relatively short time.

[0043] According to a preferred embodiment of the present invention, the combustion is performed in a pulverized coal boiler. The inventors have discovered that the combustion of low-calorific value fuels in pulverized coal boilers often results in insufficient calorific value, resulting in an inability to sustain stable combustion. Even when sustained combustion is possible, it consumes a significant amount of diesel and other combustion aids. The method of the present invention, however, can ensure sustained and stable combustion in pulverized coal boilers without the need for combustion aids.

[0044] In the present invention, it is understood that the combustion is ignited by a burner and then continues to burn.

[0045] Preferably, the combustion causes the internal temperature of the boiler to be above 650°C, more preferably above 850°C, and even more preferably between 1000°C and 1100°C. The inventors have further discovered that this preferred embodiment allows for more stable combustion; however, when the internal temperature of the boiler is below 650°C, combustion may result in flameout or significant temperature fluctuations within the furnace, which is not conducive to stable combustion.

[0046] According to a preferred embodiment of the present invention, the method further comprises: pyrolyzing the dried material to obtain pyrolysis gas and pyrolysis solid; and subjecting the pyrolysis solid to the optional grinding described in step (1). This preferred embodiment is more conducive to further converting the dried material into a pyrolysis solid with a higher calorific value density.

[0047] In the present invention, the pyrolysis solid includes semi-coke.

[0048] According to the present invention, preferably, the pyrolysis gas is at least one of CO, H2 and CH4.

[0049] In the present invention, the pyrolysis gas can be subsequently processed using existing technologies or can be recycled. Preferably, the pyrolysis gas is returned to step (3) to be used as at least part of the combustible gas.

[0050] According to the present invention, preferably, the pyrolysis conditions include: a temperature of 400-800°C, more preferably 500-700°C, and a time of 20-50 minutes, more preferably 20-40 minutes. The preferred embodiment of the present invention allows for medium-low temperature pyrolysis and fully regulates the calorific value density of low-calorific value organic matter, thereby facilitating subsequent combustion.

[0051] In a preferred embodiment of the present invention, Figure 1 As shown, the combustion method of the low calorific value organic matter includes:

[0052] (1) drying low calorific value organic matter (in a drying unit), pyrolyzing the dried material to obtain a pyrolysis solid and a pyrolysis gas, optionally grinding the pyrolysis solid to obtain a first material, and dividing the first material into a portion A and a portion B;

[0053] The drying is performed so that the moisture content of the dried material is less than 5% by weight, and the grinding is performed so that the size of the first material is less than 200 mesh;

[0054] wherein the portion A accounts for more than 30% by weight of the first material;

[0055] The pyrolysis conditions include: temperature of 500-700°C and time of 20-50 min;

[0056] (2) contacting the portion A with a gasifying agent to perform a gasification reaction (preferably in a flat flame gasifier) ​​to obtain a combustible gas and a second solid material;

[0057] The molar ratio of the gasifying agent to the portion A calculated in terms of carbon atoms is 1:0.6-1.4, and the gasification reaction conditions include: a temperature of 1300-1400° C. and a reaction time of less than 10 seconds;

[0058] (3) contacting the portion B and the second solid material with the combustible gas for combustion;

[0059] The pyrolysis gas is used in step (3) as part of the combustible gas.

[0060] By adopting the above preferred embodiment of the present invention, the utilization rate of low calorific value organic matter can be optimized, and while achieving rapid ignition, stable combustion and efficient combustion can be achieved, thereby maximizing the combustion value of the low calorific value organic matter.

[0061] To maximize resource utilization, Figure 1 As shown, those skilled in the art can use the air from the blower as secondary air for the combustion in step (3) (preferably carried out in a combustion furnace) according to actual needs.

[0062] The present invention will be described in detail below through examples.

[0063] Example 1

[0064] (1) Drying low calorific value organic matter (straw) (calorific value below 4500 kJ / kg) such that the moisture content of the dried material is 2 wt %, pyrolyzing the dried material at 600° C. for 0.5 h to obtain pyrolysis solid and pyrolysis gas, grinding the pyrolysis solid to obtain a first material, wherein the grinding ensures that the size of the first material is below 200 mesh; dividing the first material into a portion A and a portion B, wherein the portion A accounts for 30 wt % of the first material;

[0065] (2) The gasifying agent and part A (calculated in terms of carbon atoms) are contacted at a molar ratio of 1:1 in a flat-flame gasifier (the structure of the gasification unit disclosed in CN111349464A is the same, and the flat-flame gasification burner used therein includes three burner units uniformly arranged at 120° on the top of the gasifier) ​​at 1350°C for a gasification reaction for 6 seconds to obtain a combustible gas and a second solid material;

[0066] (3) igniting and burning the portion B, the second solid material, and the combustible gas in a pulverized coal boiler for 10 seconds, and using the pyrolysis gas as part of the combustible gas in step (3); the amount of the combustible gas and the pyrolysis gas is such that the heat load of the combustible gas is 35% of the total heat load of the combustion, and the boiler burns stably.

[0067] Through the detection of the internal temperature of the furnace, it was found that after the above treatment, low calorific value straw can be stably burned in the existing pulverized coal boiler, and the internal temperature of the furnace can be continuously and stably maintained at 1000-1100℃, which shows that the pulverized coal boiler can burn safely and stably.

[0068] Comparative Example 1

[0069] The method of Example 1 is followed, except that in step (3), no combustible gas and pyrolysis gas are added, and instead, the portion B and the second solid material are directly burned.

[0070] This solution ultimately leads to problems such as inability to continuously and stably output syngas components downstream of the gasifier. This results in incomplete combustion within the boiler system, unstable temperatures, and even the risk of flameout, leading to a sudden shutdown of the unit. Furthermore, the lack of stable combustion significantly increases the operating load of the power plant's subsequent ash removal units, seriously impacting the smooth operation of the entire boiler system.

[0071] Example 2

[0072] (1) drying low calorific value organic matter (straw) (calorific value below 4500 kJ / kg), wherein the drying process results in a moisture content of 4 wt % in the dried material; pyrolyzing the dried material at 500° C. for 40 min to obtain a pyrolysis solid and a pyrolysis gas; grinding the pyrolysis solid to obtain a first material; wherein the grinding process results in a size of the first material below 200 mesh; and dividing the first material into a portion A and a portion B, wherein the portion A accounts for 50 wt % of the first material;

[0073] (2) The gasifying agent and part A (calculated in terms of carbon atoms) are contacted at a molar ratio of 1:1 in a flat-flame gasifier (the structure of which is the same as the gasification unit disclosed in CN111349464A, and the flat-flame gasification burner used therein includes three burner units uniformly arranged at 120° on the top of the gasifier) ​​at 1400°C for a gasification reaction for 4 seconds to obtain a combustible gas and a second solid material;

[0074] (3) The portion B, the second solid material and the combustible gas are ignited and burned in a pulverized coal boiler for 8 seconds, and the pyrolysis gas is used as part of the combustible gas in step (3); the amount of the combustible gas and the pyrolysis gas is such that the heat load of the combustible gas is 35% of the total heat load of the combustion, and the boiler burns stably.

[0075] Through the detection of the internal temperature of the furnace, it was found that after the above treatment, low calorific value straw can be stably burned in the existing pulverized coal boiler, and the internal temperature of the furnace can be continuously and stably maintained at 1000-1100℃, which shows that the pulverized coal boiler can burn safely, stably and fully.

[0076] Example 3

[0077] The method of Example 1 is followed, except that the pyrolysis is not performed, but the dried material is directly ground. Other aspects are the same as in Example 1.

[0078] Through furnace internal temperature testing, it was found that low-calorific value straw can be stably burned in existing pulverized coal boilers, and the internal temperature of the furnace can be continuously and stably maintained at 700-800°C. Under this solution, the internal temperature of the furnace is relatively low, and the combustion effect is relatively poor.

[0079] Example 4

[0080] The method of Example 1 was followed, except that in step (3), the weight ratio of the portion B to the second solid material was 15:1, and the rest was the same as in Example 1.

[0081] Through furnace internal temperature testing, it was found that low-calorific value straw can be stably burned in existing pulverized coal boilers, and the internal temperature of the furnace can be continuously and stably maintained at 650-750°C. Under this solution, the internal temperature of the furnace is relatively low, and the combustion effect is relatively poor.

[0082] The above examples and comparative examples show that the solution of the present invention can achieve smooth and stable combustion, while the comparative example method and the existing method cannot achieve stable combustion. In the existing method, when burning low calorific value raw materials, diesel is generally introduced to assist combustion in order to ensure smooth combustion. However, since diesel easily cokes, it is not conducive to stable combustion. Among them, by comparing Example 1 with Examples 3-4, it can be seen that the preferred solution of the present invention has good stability, higher internal temperature of the furnace, and more complete combustion.

[0083] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for burning low calorific value organic matter, the method comprising: (1) Drying and pyrolyzing low calorific value organic matter to obtain pyrolysis gas and pyrolysis solid, grinding the pyrolysis solid to obtain a first material, and dividing the first material into a portion A and a portion B; wherein the pyrolysis conditions include: a temperature of 500-700° C. and a time of 20-50 minutes; and the portion A accounts for more than 30% by weight of the first material; (2) contacting the portion A with a gasifying agent to perform a gasification reaction to obtain a combustible gas and a second solid material; (3) contacting the portion B and the second solid material with the combustible gas for combustion, wherein the pyrolysis gas is used as at least part of the combustible gas, and the weight ratio of the portion B to the second solid material is 5-10:

1.

2. The method according to claim 1, wherein The low calorific value organic matter has a calorific value below 4500 kJ / kg.

3. The method according to claim 1, wherein In step (1), the drying is performed so that the moisture content of the dried material is below 5% by weight.

4. The method according to claim 3, wherein: In step (1), the drying is performed so that the moisture content of the dried material is 2-5% by weight.

5. The method according to claim 1, wherein The grinding is performed so that the size of the first material is below 200 mesh.

6. The method according to claim 1, wherein The portion A accounts for 30-90% by weight of the first material.

7. The method according to claim 1, wherein In step (2), the molar ratio of the gasifying agent to the portion A calculated in terms of carbon atoms is 1:0.6-1.4; And / or, the gasifying agent is an oxygen-containing gas.

8. The method according to claim 7, wherein: The gasifying agent is oxygen.

9. The method according to claim 1, wherein: The gasification reaction conditions include: a temperature of 1300-1400° C. and a reaction time of less than 10 seconds.

10. The method according to claim 1, wherein The combustible gas is a gas containing at least one of CO, H2 and CH4.

11. The method according to claim 1, wherein The gasification reaction is carried out in a gasifier.

12. The method according to claim 11, wherein The gasification reaction is carried out in a flat flame gasifier.

13. The method according to claim 1, wherein The amount of the combustible gas used is such that the heat load of the combustible gas is greater than 35% of the total heat load of the combustion.

14. The method according to claim 1, wherein The combustion is carried out in a pulverized coal boiler.

15. The method according to claim 14, wherein The combustion causes the internal temperature of the boiler to be 1000-1100°C.

16. The method according to claim 1, wherein The pyrolysis gas is at least one of CO, H2 and CH4.

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