BIOMASS MICRON FUEL HIGH-TEMPERATURE CLEANING AND COMBUSTION METHOD BASED ON ADIABATIC COMBUSTION CONDITIONS

Abstract

 Provided is a biomass micron fuel high-temperature cleaning and combustion method based on adiabatic combustion conditions, comprising: (a) in entirely sealed form, a biomass micron fuel is filled, handled, and transported, and delivered via a pipe to an industrial furnace; (b) the biomass micron fuel is premixed with air to form a dust cloud in fluid form; (c) the premixed fluid dust cloud is sprayed, via a fuel nozzle, into the adiabatic combustion chamber (1) arranged in the furnace; the energy of the biomass fuel having a relatively low energy density is accumulated in the closed heat storage space opposite the combustion chamber, and the closed storage space performs ultra-high-temperature combustion; (d) during the process of combustion, steam is added to the adiabatic combustion chamber (1).

Description

[0001] The invention belongs to the field of renewable clean energy resource, more particularly, it refers to a method for clean-burning and using micron-size biomass fuel under the adiabatic condition.

[0002] Nowadays, the depletion and exhaustion of fossil energy and deterioration of environment have made it urgent to develop renewable and clean energy resource and reuse waste. The biomass fuel refers to the agricultural and forestry residues including straw, saw dust, bagasse, and rice husk, etc. The agricultural and forestry residues are grinded, mixed, squeezed, and dried to form a novel clean fuel which can be directly burnt. The development of biomass fuel can not only wisely use the agricultural and forestry residues to prevent waste of resources, the emissions of carbon dioxide, sulfur dioxide, and nitrogen oxides can also be reduced and haze can be avoided. Therefore, the clean fuel would be applied widely at home and abroad.

[0003] The inventor of the application has put forward the patent application CN101935568A about micron-size biomass fuel combustion at 2010. The patent disclosed a biomass fuel formed by combining micron-size plant fiber powers with additives, and in a plurality of tests it is suggested that the combustion temperature of the micron-size biomass fuel is about 1300°C at average (the peak temperature is 1370°C), and the combustion efficiency of the biomass fuel is above 96%, in addition, the harmful components content in the waste gas of combustion can be effectively reduced.

[0004] However, follow-up studies revealed that the patent has the following shortcomings and defects: first of all, for most of the industrial applications, such as an efficient boiler steam power-generation system, the combustion temperature of fuel needs to be higher than 1500°C, which is decided by the Carnot cycle principle, only after the boiler fuel reach to a sufficient high combustion temperature, high-temperature and high-pressure steam can be generated, and further utilize the mechanical energy converted for power generation which have the economic value. Meanwhile, some of the high-temperature industrial stoves characterized by the high consumption and high emission also require the combustion temperature to reach above 1500°C, such as refractory materials, cement and glass, etc. However, the combustion temperature using existing micron-size biomass materials burning in a normal way failed to reach that high temperature. In addition, high temperature is one of the most sensitive and important conditions during industrial production. Industrial data shows that every 50°C elevation of combustion temperature can cover more industrial production needs. Moreover, the radiant heat transfer efficiency is proportional to the fourth power of the temperature. For example, when the combustion temperature of fuel increased from 1400°C to 1450°C, the thermal energy obtained by the heating body from the radiant heating is improved by 12%, meanwhile, the rise of combustion temperature further increases the combustion speed and combustion efficiency of the fuel. Under this circumstance, how to further improve and stabilize the combustion temperature and combustion efficiency of the micron-size biomass fuel, so as to broaden the application thereof in industrial environment becomes an urgent technical problem to be solved. Lastly, according to the analysis of the chemical composition, we know that the micron-size biomass fuel is a complex and solid high-molecular hydrocarbon material, and is hard to burn at a rapid rate, since the biomass fuel contains more carbon than hydrogen, the small molecules containing hydrogen burn first and inevitably, tar, residual carbon and ash content in solid state which are difficult to react with oxygen are produced. Meanwhile, the tar, residual carbon, and ash content remain in the combustion chamber of boiler for a while, and once the tar, residual carbon, and ash content do not fully react with the oxygen in time, the tar, residual carbon, and ash content are discharged as waste resources, and further form aerosol and pollutant source of haze to pollute the environment.

[0005] In view of the above-described problems, it is one objective of the invention to provide a method for clean-burning micron-size biomass fuel under the adiabatic condition. According to the characteristics of the micron-size biomass fuel and the construction features of the industrial stove, the specific design and researches have been done on the operating procedure, key process parameters, and combustion mechanism of the biomass fuel combustion, the method obtains the combustion temperature as high as 1500°C to satisfy the heating requirements for more industrial high-temperature boilers. Meanwhile, compared with the prior art, the method barely produces tar, residual carbon, or ash content, thus the method is applicable to the clean and high-temperature burning environment in the industrial production.

[0006] To achieve the above objective, in accordance with the invention, there provided a method for clean-burning micron-size biomass fuel under the adiabatic condition, comprising:

1) grinding raw biomass material composed of plant fiber to solid powders, which can be served as micron-size biomass fuel. The solid powders have an average particle size smaller than 400 µm; encapsulating the micron-size biomass fuel; loading and transporting the micron-size biomass fuel to industrial stoves for burning via pipelines;

2) premixing the micron-size biomass fuel with air to form flowing dust cloud prior to entering the industrial stoves, and set the excess air coefficient between 0.98 and 1.25 during the operation.

3) ejecting the flowing dust cloud premixed in 2) to an adiabatic combustion chamber in the industrial stoves via a fuel nozzle along a tangential direction, and the adiabatic combustion chamber being a relatively sealed heat storage space comprising a side wall made from an insulating material layer; the volumetric combustion intensity of the adiabatic combustion chamber is set between 150 and 400 kg/m³; surrounding the side wall using a heating body of the industrial stoves, and controlling heat flowing through the side wall to be less than 10% of combustion energy of the micron-size biomass fuel; the fuel nozzle being at least one in number, and the velocity of ejection being between 1 and 10 m/s; gasifying and burning the flowing dust cloud at a distance between 0.5 and 2.5 time(s) the diameter of the fuel nozzle to obtain a combustion temperature between 1500 and 1600°C, the high-temperature flame ejected from the adiabatic combustion chamber to heat the heating body;

4) adding moderate steam to the adiabatic combustion chamber during combustion, and a mass ratio of the micron-size biomass fuel to the steam being 1:30-150 to accelerate gasification and decomposition of intermediates comprising tar and carbon particles produced during the combustion prior to departing from the flame; discharging melted ash content in a form of liquid glass at the bottom part of the adiabatic combustion chamber after the residual ash content melted and separated from the high temperature flame when the combustion is completed.

[0007] In a class of this embodiment, in 1), the micron-size biomass fuel comprises more than 35 wt.% of powders having a particle size smaller than 50 µm. The micron-size biomass fuel comprises more than 75 wt.% of powders having a particle size smaller than 100 µm. The micron-size biomass fuel comprises more than 90 wt.% of powders having a particle size smaller than 250 µm.

[0008] In a class of this embodiment, in 1), the micron-size biomass fuel is rigidly or flexibly sealed in a container to be loaded and transported, and the volume of the container is between 1.5 and 90 m³.

[0009] In a class of this embodiment, in 2), preferably, the excess air coefficient is set between 1.0 and 1.15.

[0010] In a class of this embodiment, in 3), preferably, the volumetric combustion intensity of the adiabatic combustion chamber is set between 200 and 300 kg/cm³, and the heat flowing through the side wall is no more than 3%-6% of the combustion energy of the micron-size biomass fuel.

[0011] In a class of this embodiment, in 3), preferably, the adiabatic combustion chamber is a relatively sealed heat storage space comprising the side wall made from an insulating material layer of alumina fiber, and the thickness of the side wall is between 80 and 320 mm. A height of the adiabatic combustion chamber is between 0.8 and 4 time(s) the diameter of the adiabatic combustion chamber.

[0012] In a class of this embodiment, in 4), preferably, the mass ratio of the steam to the micron-size biomass fuel is 1:60-120.

[0013] In a class of this embodiment, preferably, the industrial stoves are boilers that served as boiler steam power-generation system, or stoves made from cement, glass, ceramics, etc.

[0014] Advantages of the method for clean-burning micron-size biomass fuel under the adiabatic condition according to embodiments of the invention are summarized as follows:

1. The adiabatic combustion chamber is provided, and the key parameters including volumetric combustion intensity and contact temperature are set up according to the combustion of the micron-size biomass fuel to form a relatively sealed heat storage space so that combustion energy of the biomass fuel with a relatively low energy density is accumulated and high-temperature combustion condition is formed in the adiabatic combustion chamber. Meanwhile, the gasification and combustion of the powders are simultaneously and instantly completed in the same space to produce ultra-high temperature combustion, and the high combustion temperature further improves the combustion speed and combustion efficiency of the micron-size biomass fuel, thus the average combustion temperature is obviously increased compared to the combustion temperature in the prior art, and the combustion efficiency is above 98%. The ultra-high temperature combustion of the micron-size biomass fuel not only completely decomposes the intermediates including tar and carbon particles, but also melts the incombustible inorganic components. The melted inorganic component is then discharged from the bottom of the stoves as liquid slag. Therefore, the production of clean-burning of the solid biomass fuel includes no tar, residual carbon, or ash content.

2. The solid biomass fuel is hermetically encapsulated, loaded, and transported, and the transportation of the bulky and flammable micron-size biomass fuel with a relatively low energy density is low-cost, efficient, and safe, thus the method satisfies the requirements of industrial-scale energy supplement and application.

3. The micron-scale biomass fuel is premixed with the air using certain excess air coefficient before the fuel enters the industrial stoves. Tests show that the premixing can effectively increase the possibility of oxygen expanding to the surface of bio-particles in the flowing dust cloud, and ensure the complete combustion of bio-particles. In addition, the premixing, in combination with the adiabatic conditions, improve the temperature peak of the combustion.

4. Specifications and ejection velocity of the adiabatic combustion chamber are specifically designed to ensure that the micron-size biomass fuel have enough residence time and that the components involved in the combustion always float during the combustion process, instead of depositing at the bottom of the combustion chamber, so as to facilitate the sufficient combustion of the fuel and improve the combustion temperature.

5. Steam is added at a certain percentage during the combustion process. Steam served as a gasification agent which can react with the intermediates, and decompose the intermediates to hydrogen and carbon monoxide. Hydrogen accelerates the flame spread rate in the limited combustion space and ensures that the expected temperature peak and combustion efficiency are achieved in a short time.

6. By using the method in the embodiments of the invention, the combustion temperature of the micron-size biomass fuel is further improved to be higher than 1500°C, thus correspondingly satisfying the heating requirements of most of the industrial productions. Especially, the method is applicable to the clean and efficient burning in all kinds of industrial stoves.

[0015] FIG. 1 is a flowchart of a method for clean-burning micron-size biomass fuel in accordance with one embodiment of the invention.

[0016] FIG. 2 is a diagram showing an application environment of combustion technology comprising an adiabatic combustion chamber in accordance with one embodiment of the invention.

[0017] For further illustrating the invention, experiments detailed a method for clean-burning micron-size biomass fuel under the adiabatic condition are described below. It should be noted that the following examples are intended to describe and not to limit the invention. In addition, the technical features mentioned in each example can be combined as long as the features do not conflict with each other.

[0018] The combustion temperature of biomass fuel burned using the conventional method at between 700 and 1000°C, thus the biomass fuel can only be applied to household heating and cooking. However, since the industrial revolution, the working temperature is required to be even higher, and the combustion quality is even strictly requested. For example, the reaction temperature of the ceramics is mostly about 1300°C, and the heating temperature from the fuel is required to be above 1500°C; the chemical transition temperature of cement burning is above 1400°C, and the heating temperature from the fuel is required to be above 1500°C to ensure the production efficiency. In an efficient boiler steam power-generation system, the combustion temperature from the fuel is required to be above 1500°C, therefore, the combustion temperature of the biomass fuel directly influence whether the biomass fuel can be applied to modern industry production. On the other hand, when the biomass hydrocarbon fuel burned at a low temperature, incomplete combustion produces tar and residual carbon which further form aerosol and haze. The utilization rate of energy is low, meanwhile, the unburnt hydrocarbon becomes environmental pollutant source, both of which influence the application of biomass fuel in industrial-scale production.

[0019] Conventionally, the biomass fuel is burnt using the layer combustion technology, and the fuel failed to fully react with the air in a short period of time in the combustion chamber. The combustion temperature is low, and tar is produced, forming haze. Meanwhile, ash content produced by the layer combustion buries the fuel and hinders the contact and reaction with the oxygen. Certain amount of residual carbon is unburnt and discharged from the combustion chamber as slag, causing waste of resources. Under this circumstance, although burning the micron-size biomass fuel disclosed in the prior patent application can obtain relatively high combustion temperature and effectively reduce pollutant discharge, the combustion temperature of the biomass fuel is limited to be about 1350°C, and actually, tar, carbon particles, and especially ash content residues are not completely avoided, as revealed by follow-up studies. Therefore, a profound study on the combustion process, combustion temperature, combustion efficiency, and the combustion mechanism of the micron-size biomass fuel should be conducted to obtain a higher combustion temperature and to satisfy the heating requirements of industrial high-temperature boilers. Meanwhile, no tar, residual carbon, or ash content is ensured so that the low-cost biomass fuel is applicable to the clean-burning in industrial production.

[0020] Specifically, the method for clean-burning micron-size biomass fuel comprises the following steps. The steps are illustrated as follows, and the illustration is mainly focused on the design and principles of the key combustion conditions.

[0021] First of all, raw biomass material composed of plant fiber is grinded to solid powders of micron-size biomass fuel, and an average particle size of the solid powders is smaller than 400 µm. The micron-size biomass fuel is hermetically encapsulated, loaded and transported to industrial stoves via pipelines. For example, the biomass fuel is composed of plant fiber and additive. The additive is pulverized coal, pulverized lime, red mud, or a mixture thereof. The plant fiber comprises more than 35 wt.% of powders having a particle size smaller than 50 µm. The plant fiber comprises more than 75 wt.% of powders having a particle size smaller than 100 µm. The plant fiber comprises more than 90 wt.% of powders having a particle size smaller than 250 µm. Similar to the coal, the micron-size biomass fuel is characterized by high consumption and light weight, when the biomass fuel is packaged in bags like the flour, the labor cost is high, and dust flying tends to occur when the bags are opened to discharge the powders, resulting in horrible working environment, waste of resources, and risks of fire outbreak. Meanwhile, the powders in bags are easy to get damp, then the mobility thereof is adversely affected. Once the powders get damp, the cost of drying the powders is higher than the cost of fuel itself. Therefore, in the first step, the micron-size biomass fuel is hermetically encapsulated, loaded and transported to industrial stoves in the form of solid powders, and the transportation of bulky and flammable micron-size biomass fuel with a relatively low energy density is low-cost, efficient, and safe, thus the method satisfies the requirements of industrial-scale energy supply and application.

[0022] Then, before the micron-size biomass fuel enters the industrial stoves, the micron-size biomass fuel is premixed with air to form flowing dust cloud, and an excess air coefficient is set between 0.98 and 1.25; preferably, the excess air coefficient is between 1.0 and 1.15. The biomass fuel is premixed using the excess air coefficient to form the flowing dust cloud because firstly the combustion needs air, and especially oxygen in the air. However, in the air, oxygen only accounts for 21%, and the rest of air is the inert gas nitrogen. The molecular weights of oxygen and nitrogen are similar, thus the separation of nitrogen and oxygen is difficult, meanwhile, the oxygen-enriched air and pure oxygen are costly, in reality, fuel is directly burned in the air. When one cubic meter of oxygen enters the adiabatic combustion chamber, four cubic meters of nitrogen enter the adiabatic combustion chamber together with the oxygen, and the nitrogen absorbs heat and decreases the temperature in the combustion chamber, thus in the first place too much air should be avoided from entering in the combustion chamber, and the excess air coefficient is designed to be lower than 1.3. Comparison tests show that when the biomass fuel is at micron-size, without being compressed, the structure of the biomass like a porous network, and oxygen can penetrate into the micropores, in addition, the biomass fuel is rich in volatile components, thus about 70% of the solid structure can be decomposed at 500°C. Meanwhile, due to the high hydrogen content, the excess air coefficient is required to be controlled above 0.98. Practice shows that the excess air coefficient in the invention can effectively improve the possibility of oxygen expanding to the surface of bio-particles in the flowing dust cloud, ensure the complete combustion of bio-particles, reduce the amount of excess air, and increase the combustion efficiency, which means that the excess air coefficient is an important feature which ensures the high-temperature combustion of biomass fuel.

[0023] The premixed flowing dust cloud is ejected to the adiabatic combustion chamber in the industrial stoves via a fuel nozzle 11 along a tangential direction. One of the key improvements of the invention is that the adiabatic combustion chamber 1 is a relatively sealed heat storage space comprising a side wall 2 made from an insulating material layer, and a volumetric combustion intensity of the adiabatic combustion chamber is between 150 and 350 kg/m³. The side wall is surrounded by the heating body of the industrial stoves, and heat flowing through the side wall is controlled to be less than 10% of combustion energy of the micron-size biomass fuel. The fuel nozzle is at least one in number, and a velocity of ejection being between 1 and 10 m/s, so that the combustion condition and the combustion speed are controlled. The flowing dust cloud is gasified and floats in the combustion chamber the moment the dust cloud departs from the fuel nozzle, instead of settling at the bottom of the combustion chamber, and the flowing dust is burned instantly (at a distance between 0.5 and 2.5 time(s) the diameter of the fuel nozzle) to obtain a combustion temperature between 1500 and 1600°C at average.

[0024] As shown in FIG. 2, the technical results brought by the designs and the principles are specifically explained as follows. Firstly, the adiabatic combustion chamber 1 is provided, and the key parameters including volumetric combustion intensity and contact temperature of the adiabatic combustion chamber are set up according to the combustion of the micron-size biomass fuel to form a relatively sealed heat storage space so that combustion energy of the biomass fuel with a relatively low energy density is accumulated and high-temperature combustion condition in the adiabatic combustion chamber is formed. Meanwhile, the gasification and combustion of the powders are simultaneously and instantly completed in the same space to produce ultra-high temperature combustion, and the high combustion temperature further improves the combustion speed and combustion efficiency of the micron-size biomass fuel, therefore the average combustion temperature is obviously increased compared to that of the prior art, and the combustion efficiency is above 98%. Analyzed from the reaction mechanism, the fuel is not just simply stacked in the combustion chamber, instead, a large amount of fuel molecules collides with oxygen molecules one-to-one, and rapidly release energy in the combustion chamber, which contributes to the accumulation of temperature, and then disappear fast to release space for new fuel coming. In other words, in a unit combustion space and within a unit combustion period, the more heat released from the fuel and accumulated in the space, the higher the combustion temperature is. A great many tests show that the method in accordance with the above design can obtain the combustion temperature as high as between 1500 and 1600°C at average.

[0025] In addition, according to the theory of thermal radiation, the radiation force refers to the full wavelength energy emitted by a unit surface area of an object to a hemisphere space per a unit time, and the unit is W/m². The relationship between the radiation force and the temperature is shown as Formula (1):

[0026] Therefore, when the combustion temperature increased from 1300°C to 1450°C, the radiation force is correspondingly increased:

[0027] The tar and residual carbon can be quickly decomposed and burnt in the oxygen at 900°C, and as the combustion temperature in the example of the invention is 1500°C, the tar and residual carbon can be completely decomposed in 0.2 seconds at such a high temperature. Take a 4 t/h industrial boiler as an example, a volume of the adiabatic combustion chamber is 1.8 m³, and the time T that the combustion product remains in the combustion chamber is obtained by:

where, B_j is the fuel consumption (kg/s); V_g is the flue gas volume (Nm³/kg); V is the volume of the combustion chamber (m³); and t_av is the average temperature of the flue gas. The time T that the flue gas remains in the adiabatic combustion chamber is obtained T=0.26 s. Therefore, in the invention, tar and residue carbon can be effectively decomposed at such a high temperature within the residence time of the flue gas. The hydrocarbon is burnt out, and the flue gas exhausted from the combustion chamber contains no tar and carbon particles. A more detailed illustration is made in the following examples.

Example 1

[0028] The feed rate of the micron-size biomass fuel is 700 kg/h; the caloric value of the fuel is 4100 Kcal/kg; the diameter of an inner chamber of the adiabatic combustion chamber is 1400 mm, and a height of the inner chamber is 1800 mm. The micron-size biomass fuel is premixed with certain amount of air, and is ejected to the combustion chamber from the bottom along a tangential direction at a rate of 5 m/s. The combustion chamber comprises a lining built by firebrick. A thickness of the lining is 114 mm. The lining is coated by alumina fiber cotton for thermal insulation which is highly pure.

[0029] Table 1 shows the test results of combustion temperatures varying with different thicknesses of the alumina fiber cotton and with different excess air coefficients:

Example 2

[0030] The feed rate of the micron-size biomass fuel is 705 kg/h; the caloric value of the fuel is 4100 Kcal/kg; the diameter of an inner chamber of the adiabatic combustion chamber is 1400 mm. The micron-size biomass fuel is premixed with certain amount of air using the excess air coefficient 1.05, and is ejected to the combustion chamber from the bottom along a tangential direction at a rate of 5 m/s. The combustion chamber comprises a lining built by firebrick. A thickness of the lining is 114 mm. The lining is coated by alumina fiber cotton for thermal insulation which is highly pure, and a thickness of the fiber cotton is 150 mm. Table 2 shows the test results of combustion temperatures varying with different heights of the adiabatic combustion chamber. Table 3 shows the test results of the blackness of flue gas varying with different heights of the combustion chamber and different steam additions.

[0031] Because the combustion temperature in the invention has improved 150°C compared to that of the prior art, correspondingly, the radiation force in the combustion chamber is improved by 43%. In addition, the decomposition rate and gasification rate, as calculated above, have also greatly been increased, thus facilitating the clean burning of biomass fuel which barely generates tar, residual carbon, or ash content.

[0032] Lastly, steam is added in the adiabatic combustion chamber during combustion, and a mass ratio of the steam to the micron-size biomass fuel is 1:30-150 so as to accelerate gasification and decomposition of intermediates comprising tar and carbon particles produced during the combustion prior to departing from the flame. Melted ash content departs from the flame when the combustion is completed, and is settled at the bottom of adiabatic combustion chamber. The melted ash content in a form of liquid glass is discharged by the slag removal mechanism 4 with a slag removal piston at one side of the inspection manhole 61.

[0033] Steam is added because steam as a gasification agent can react with the intermediates during the combustion, and can decompose the intermediates to hydrogen and carbon monoxide. Hydrogen further accelerates the combustion speed and ensures that the expected temperature peak and combustion efficiency are achieved in a short period of time. For example, tests show that the proportion of steam designed in the invention, in combination with other combustion conditions, enables the dust cloud to be completely gasified and burnt at a distance between 0.5 and 2.5 time(s) the diameter of the fuel nozzle after the dust cloud departs from the fuel nozzle.

[0034] While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

Claims

1. A method for clean-burning micron-size biomass fuel under the adiabatic condition, the method comprising:

1) grinding raw biomass material composed of plant fiber to solid powders of micron-size biomass fuel, an average particle size of the solid powders being smaller than 400 µm; hermetically encapsulating the micron-size biomass fuel; loading and transporting the micron-size biomass fuel to industrial stoves for burning via pipelines;

2) premixing the micron-size biomass fuel with air to form flowing dust cloud prior to entering the industrial stoves, and an excess air coefficient is between 0.98 and 1.25;

3) ejecting the flowing dust cloud premixed in 2) to an adiabatic combustion chamber in the industrial stoves via a fuel nozzle along a tangential direction, and the adiabatic combustion chamber being a relatively sealed heat storage space comprising a side wall made from an insulating material layer; setting a volumetric combustion intensity of the adiabatic combustion chamber to between 150 and 350 kg/m³; surrounding the side wall using a heating body of the industrial stoves, and controlling heat flowing through the side wall to be less than 10% of combustion energy of the micron-size biomass fuel; the fuel nozzle being at least one in number, and a velocity of ejection being between 1 and 10 m/s; gasifying and burning the flowing dust cloud at a distance between 0.5 and 2.5 time(s) the diameter of the fuel nozzle to obtain a combustion temperature between 1500 and 1600°C; allowing extrusive flame to heat the heating body; and

4) adding steam in the adiabatic combustion chamber during combustion, and a weight ratio of the steam to the micron-size biomass fuel being 1:30-150 to accelerate gasification and decomposition of intermediates comprising tar and carbon particles produced during the combustion prior to departing from the flame; discharging melted ash content in a form of liquid glass at a bottom part of the adiabatic combustion chamber after the melted ash content departs from the flame when the combustion is completed.

2. The method of claim 1, characterized in that the micron-size biomass fuel comprises more than 35 wt.% of powders having a particle size smaller than 50 µm; the micron-size biomass fuel comprises more than 75 wt.% of powders having a particle size smaller than 100 µm; and the micron-size biomass fuel comprises more than 90 wt.% of powders having a particle size smaller than 250 µm.

3. The method of claim 1, characterized in that in 1), the micron-size biomass fuel is rigidly or flexibly sealed in a container, and is loaded and transported, and a volume of the container is between 1.5 and 90 m³.

4. The method of claim 1 or 2, characterized in that in 2), the excess air coefficient is between 1.0 and 1.15.

5. The method of claim 1, 2, or 3, characterized in that in 3), the volumetric combustion intensity of the adiabatic combustion chamber is between 200 and 300 kg/cm³, and the heat flowing through the side wall is no more than 3%-6% of the combustion energy of the micron-size biomass fuel.

6. The method of claim 5, characterized in that in 3), the adiabatic combustion chamber is the relatively sealed heat storage space comprising the side wall made from an insulating material layer of inorganic fiber and refractory material, and a thickness of the side wall is between 80 and 320 mm; and a height of the adiabatic combustion chamber is between 0.8 and 4 time(s) the diameter of the adiabatic combustion chamber.

7. The method of claim 5, characterized in that in 4), the weight ratio of the steam to the micron-size biomass fuel is 1:60-120.

8. The method of any one of claims 1-7, characterized in that the industrial stoves are boilers, or stoves made from cement, glass, ceramics, etc.

Drawing