Chain grate machine-rotary kiln pelletizing process biomass-hydrogen-based fuel gas composite heat supply method

Abstract

The invention discloses a grate-rotary kiln pellet process biomass-hydrogen-based fuel gas composite heat supply method, which comprises the following operation steps A, B and C in a grate-rotary kiln pellet production process: A: mixing biomass charcoal and a pellet material for pelletizing; b, the biomass solid fuel and the hydrogen-based fuel gas are injected into the rotary kiln at the same time; and C, fuel gas and / or air are / is injected to the joint of the chain grate machine and the rotary kiln head so as to regulate and control the oxygen content and temperature of the flue gas of the second preheating section. According to the method, under the condition that normal production of the pellets is not affected, due to the fact that a renewable, clean and low-carbon fuel structure is fully adopted, the number of CO2 and gas pollutants generated by combustion of fossil fuel is remarkably reduced.

Description

Technical Field

[0001] The invention relates to a pellet production heating method, in particular to a biomass-hydrogen-based fuel gas composite heating method for a grate-rotary kiln pelletizing process, belonging to the field of iron ore pelletizing process in steel metallurgy. Background Art

[0002] The steel industry is one of the major sources of global carbon emissions. Reducing carbon emissions from steel production is of great significance to the low-carbon production of global steel. The reason is that the huge carbon emissions from steel production are related to the large consumption of fossil fuels. Therefore, in addition to optimizing the smelting process with lower carbon content, it has also become a top priority to develop and utilize clean energy to replace fossil energy with high pollution and high carbon emissions.

[0003] Pellets are high-quality, low-carbon raw materials for long and short processes of iron and steel metallurgy. The energy consumption of the pelletizing process is only 1 / 2 of that of the sintering process, and the emissions of pollutants such as dust, SO2, and NOx are 1 / 7, 1 / 3, and 1 / 5 of those of the sintering process, respectively. Therefore, it has more advantages in terms of energy consumption and environmental protection. At present, China's blast furnace charge is still mainly sintered ore, and the proportion of pellets entering the furnace is low. However, countries such as Sweden, the United States, Canada, and Mexico use almost 100% pellet ore for smelting. It can be seen that Chinese steel companies have a large space to develop a high proportion of pellets to achieve low-carbon production. The pelletizing rotary kiln is the mainstream equipment for pellet production, and its output accounts for more than 60% of the total output of pellets. Compared with the belt roaster and shaft furnace process, the pelletizing rotary kiln process has the characteristics of good pellet quality and strong fuel adaptability, and can spray heavy oil, coal gas, and coal powder alone or simultaneously. Due to the current shortage of natural gas and oil resources in China, pelletizing rotary kilns mostly spray coal-based fuels such as pulverized coal and coal gas produced from coke ovens and blast furnaces. Fossil fuels will produce a large amount of CO2. Therefore, it is necessary to conduct research on the pelletizing rotary kiln process to spray cleaner fuels to alleviate its dependence on fossil fuels.

[0004] Biomass energy is the fourth largest energy source after coal, oil and natural gas. Biomass energy is a renewable resource that comes directly or indirectly from photosynthesis of plants and is a form of solar energy storage. For lignocellulosic biomass fuel, the CO2 released during combustion comes from the absorption of CO2 from the atmosphere during its growth, that is, it has the characteristic of near-zero CO2 emissions. Therefore, the use of biomass fuel will not increase the amount of CO2 in the atmosphere like fossil fuels. Using biomass fuel for pellet production can effectively reduce the dependence of steel production on fossil energy and carbon emissions.

[0005] In the pelletizing rotary kiln process, there are two ways to add fuel: (1) spraying fuels in different forms such as gas, solid, and liquid through the spray gun at the rear of the rotary kiln; (2) adding solid fuels with high carbon content to the pellets, such as coke powder and anthracite. In China, in addition to spraying pulverized coal alone, the combined injection of gas and pulverized coal is a common heating mode for pelletizing rotary kiln production. Using biomass fuel to replace pulverized coal and spraying it together with hydrogen-rich and low-carbon gases such as natural gas or coke oven gas in the pelletizing rotary kiln, and adding biomass charcoal with a high carbon content to the pelletizing fuel to completely or partially replace the use of pulverized coal and coke powder can reduce the consumption of fossil fuels such as pulverized coal in the pelletizing rotary kiln process and promote low-carbon production. In addition, hydrogen energy is regarded as a clean energy. The fuel supply mode of biomass and hydrogen in the pelletizing rotary kiln can also significantly reduce its carbon emissions. However, the high cost of hydrogen production and the difficulty of hydrogen storage and transportation limit the application of hydrogen energy.

[0006] In terms of the use of biomass fuel and hydrogen-based fuel gas for iron ore pellet production, a Chinese patent (publication number: CN116287689A) discloses a method for using low-alkali biomass fuel for pelletizing rotary kiln injection, which is to apply a mixed fuel containing low-alkali biomass fuel to the pelletizing rotary kiln for injection; the low-alkali biomass fuel is low-alkali biomass obtained by water immersion of biomass raw materials and / or low-alkali biomass charcoal obtained by water immersion and pyrolysis of biomass raw materials. Biomass fuel has low alkali metal content, low explosiveness, and good combustibility. This type of biomass fuel can safely replace conventional coal powder for pelletizing rotary kiln injection, which can significantly reduce the production cost of oxidized pellets and CO2, SO x and NO x The emission volume increases the applicability of biomass fuel in the field of oxidation pellet production and reduces the steel industry's dependence on coal resources. The preparation process of such biomass fuel does not require external heating equipment and has no pollutant emissions. A Chinese patent (publication number: CN110699141A) discloses a chain grate-rotary kiln sprayed biomass fuel and its preparation method and application. After the biomass powder and the iron-containing mineral powder are fully mixed, they are heated and carbonized in a mixed atmosphere of protective gas and water vapor to obtain a volatile matter content of 10-20%, a combustion calorific value of 20-27MJ / kg, a porosity of 40-60%, and a specific surface area of ​​40-70m 2 / g of biomass fuel, which can replace part of the conventional pulverized coal fuel for rotary kiln tail injection fuel, can reduce fuel costs and is conducive to efficient reduction of SOx and NOx emissions from the source. Chinese patent (publication number: CN118703776A) discloses a method for preparing carbon-containing pellets using biomass, carbon-containing pellets and metallized pellets, wherein the biomass is hydrothermally carbonized to obtain biochar; the biochar, iron ore powder, binder and solvent are mixed according to a set mass ratio to obtain a premix; and the premix is ​​pelletized and dried to obtain carbon-containing pellets. By optimizing the ratio of biochar, iron ore powder, binder and solvent, the close contact between the iron ore powder and the reducing agent inside the carbon-containing pellets is ensured, thereby promoting the coupling effect of the gasification reaction and the reduction reaction of the carbon-containing pellets, and having excellent self-reduction performance; at the same time, it avoids the carbon particles from hindering the convergence of the iron phase, and improves the strength of the carbon-containing pellets. Thereby solving the technical problem that the carbon-containing pellets in the prior art cannot simultaneously meet high strength and high self-reduction properties. A Chinese patent (publication number: CN116904742A) discloses a method for preparing pellets using natural gas. This method reduces production costs while obtaining high-quality pellets. It has the characteristics of easy process control, energy saving and consumption reduction, and high product quality. A Chinese patent (application number: CN110129501A) discloses a technical improvement method for optimizing and reducing nitrates using vanadium-titanium pellet fuel gas. The combustion characteristics of blast furnace gas and coke oven gas are matched: when adding and mixing into blast furnace gas, the pressure difference with coke oven gas should be minimized as much as possible, so that blast furnace gas and coke oven gas can be effectively mixed. Before mixing into blast furnace gas, pure coke oven gas should be used for normal ignition, and then an appropriate proportion of blast furnace gas is gradually added. The ratio of blast furnace gas to coke oven gas is determined to be 2:1. The amount of blast furnace gas is gradually added in an appropriate amount, and the process is carried out while observing. This technical improvement method for optimizing and reducing nitrates using vanadium-titanium pellet fuel gas reduces the thermal NO in the flue gas after combustion. x At the same time, the partition wall of the ring cooler was modified to increase the temperature of the reheated air, ensuring the stable increase of the temperature in the rotary kiln, avoiding the phenomenon of incomplete combustion caused by too low reheating, thereby ensuring the roasting effect of the briquette and greatly reducing NO x The amount of production.

[0007] Although the above patented technology discloses the application of biomass fuel and hydrogen-rich gas in the production of iron ore pellets, the fuel types used are relatively single, so they are greatly affected by the stability of fuel supply, making it difficult to use them in industrial production, and it is also difficult to completely get rid of the dependence of the pellet production process on fossil fuels. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a method for biomass-hydrogen-based gas composite heating in a chain grate-rotary kiln pelletizing process, which reduces the use of fossil fuels by optimizing the fuel structure and heating mode of the pelletizing production process, thereby achieving the purpose of significantly reducing CO2 and gaseous pollutant emissions.

[0009] In order to achieve the above technical purpose, the present invention provides a method for biomass-hydrogen-based gas composite heating in a chain grate-rotary kiln pelletizing process, which comprises performing operation steps A, B and C in the chain grate-rotary kiln pelletizing production process:

[0010] A: Biomass charcoal is mixed with pellets to make pellets;

[0011] B: Spraying biomass solid fuel and hydrogen-based fuel gas simultaneously in the rotary kiln;

[0012] C: Gas and / or air is sprayed at the connection between the chain grate and the kiln head of the rotary kiln to regulate the oxygen content and temperature of the flue gas in the second preheating stage.

[0013] The technical solution of the present invention, in the process of producing pellets in a chain grate-rotary kiln, on the one hand, adds biochar to the pellets, and partially or completely replaces coal powder with biochar to effectively reduce the emission of pollutants such as CO2, NOx and SO2. At the same time, biochar can be used to increase the internal porosity of the pellets, so that the pellets have better reducibility, thereby obtaining ironmaking furnace materials with lower carbon characteristics. On the other hand, a composite fuel composed of biomass solid fuel and hydrogen-based gas is used for pelletizing rotary kiln injection. By optimizing the fuel structure, more biomass fuel is used in the pelletizing production process, which can well reduce the emission of CO2 and pollutants, while improving the roasting efficiency of the pellets. In particular, the composite of biomass solid fuel and hydrogen-based gas for pelletizing rotary kiln injection can effectively solve the problem of unstable fuel supply and difficulty in realizing industrial production when using a single biomass fuel or clean fuel such as hydrogen-based gas. Thirdly, when spraying biomass solid fuel and hydrogen-based gas composite fuel, the flue gas temperature and composition will change, thus affecting the normal production of pellets. The present invention sprays gas and / or air at the connection between the chain grate and the kiln head of the rotary kiln to adjust the oxygen content and temperature of the flue gas in the second preheating stage within a suitable range to solve the technical problems caused by the composite spraying of biomass solid fuel and hydrogen-based gas. In summary, the present invention can greatly improve the application of biomass fuel in the pellet production process without affecting the normal pellet production of the chain grate-rotary kiln, so as to achieve the purpose of reducing the emission of CO2 and pollutants.

[0014] As a preferred solution, the biochar is added to the pellet material at a ratio of 0.1 to 2 wt.%. Theoretically, the higher the ratio of biochar replacing fossil fuels in the pellet material, the more conducive to the reduction of CO2 and pollutants. However, if the biochar ratio is too high, the compressive strength of the pellets will be deteriorated. Therefore, the biochar ratio should not exceed 2 wt.%. Other fuels in the pellet material can also be part of coal powder and coke powder with biochar.

[0015] As a preferred solution, the volume proportion of the biochar particle size less than 74 microns is not less than 80%. The particle size of the biochar is preferably controlled within a preferred range. If the particle size is too large, it will affect the bonding strength of the pellets.

[0016] As a preferred solution, the biochar has a fixed carbon content greater than 65%, an ash content less than 5%, a volatile calorific value greater than 28 MJ / kg, a combustion start temperature greater than 400°C, a gasification start temperature greater than 600°C, a potassium content less than 1%, and a chlorine content less than 0.1%. It is further preferred that the biochar is pyrolytic charcoal and / or hydrothermal charcoal.

[0017] As a preferred embodiment, the biomass solid fuel includes at least one of biomass raw materials, biomass pyrolysis charcoal, biomass hydrothermal charcoal, and / or at least one of biomass raw material upgraded products, biomass pyrolysis charcoal upgraded products or biomass hydrothermal charcoal upgraded products.

[0018] As a preferred solution, the ash content of the biomass pyrolysis charcoal, the biomass pyrolysis charcoal upgraded product, the biomass hydrothermal charcoal and the biomass hydrothermal charcoal upgraded product is less than 10%, the ash melting point exceeds 1300°C, the volatile matter content is less than 40%, the calorific value is greater than 25MJ / kg, the K content is controlled below 2%, the Cl content is controlled below 0.5%, the starting combustion temperature is controlled between 300 and 420°C, and the comprehensive combustion characteristic index is not less than 0.50×10 -12 s -2 .℃ -3 The burning intensity is not less than 4.8×10 -4 s -1 As a preferred solution, the water content of the biomass raw material and the biomass raw material upgraded product is less than 5%, the ash content is less than 3%, the ash melting point is not less than 3000°C, the K content is controlled below 1%, and the Cl content is controlled below 0.1%.

[0019] The biomass solid fuel used for injection in the present invention is preferably a biomass raw material, biomass pyrolysis charcoal, biomass hydrothermal charcoal, a biomass raw material upgraded product, a biomass pyrolysis charcoal upgraded product or a biomass hydrothermal charcoal upgraded product, etc., whose physical and chemical property parameters are within the preferred range. Otherwise, it will aggravate the ring formation of the rotary kiln, deteriorate the quality of the pellets, and affect the normal pellet production.

[0020] As a preferred solution, the biomass solid fuel particle size satisfies that the volume proportion of the particle size less than 150 μm is less than 50%, and the volume proportion of the particle size less than 250 μm is more than 90%. The particle size of the biomass pyrolysis charcoal, biomass pyrolysis charcoal upgraded product, biomass hydrothermal charcoal, biomass hydrothermal charcoal upgraded product, biomass raw material and biomass raw material upgraded product of the present invention will affect its combustion performance. The particle size is controlled within the preferred range, which can ensure high combustion efficiency and fast heat release rate, thereby ensuring stable heat supply during pellet roasting.

[0021] As a preferred solution, when the biomass solid fuel adopts at least one of biomass pyrolysis charcoal, biomass pyrolysis charcoal upgraded product, biomass hydrothermal charcoal and biomass hydrothermal charcoal upgraded product, its heat supply ratio accounts for 1-99% of the total heat supply of the fuel sprayed into the rotary kiln. As a preferred solution, when the biomass solid fuel adopts biomass raw materials and / or biomass raw materials upgraded product, its heat supply ratio accounts for less than 50% of the total heat supply of the fuel sprayed into the rotary kiln. The biomass raw materials and biomass raw materials upgraded product are preferably sprayed with hydrogen-based fuel gas, mainly based on the low energy density of biomass raw materials or biomass raw materials upgraded products that have not been carbonized. It is best to spray with hydrogen-based fuel gas with a high hydrogen content such as hydrogen, coke oven gas, etc. with a fast combustion speed and strong flue gas thermal conductivity, which can improve the combustion effect. And the proportion of biomass raw materials should not be too high. If the proportion of biomass raw materials is too high, it will increase the pressure of powder making and transportation. At the same time, during the combustion process of biomass raw materials, they will first absorb heat for thermal decomposition and release volatiles first. In addition, the hydrogen-based fuel gas injected in combination with it has a slow combustion speed, which will cause the high temperature of the rotary kiln to move forward, destroying the original equilibrium state of pellet roasting and affecting normal pellet production.

[0022] As a preferred solution, the hydrogen-based fuel gas includes at least one of hydrogen, coke oven gas, natural gas and biomass gas. The preferred hydrogen-based fuel gas is hydrogen-rich gas fuel.

[0023] As a preferred solution, gas and / or air are sprayed at the connection between the chain grate and the kiln head of the rotary kiln to adjust the flue gas oxygen volume content of the second preheating stage to 16-19% and the temperature to 850-1050° C. A hot air regulating spray gun is added at the connection between the rotary kiln and the chain grate to flexibly adjust the flue gas temperature and composition by spraying gas and / or air, especially by adjusting the flue gas oxygen volume content of the second preheating stage to be stable at 16-19% and the temperature to be stable at 850-1050° C., so as to solve the problem that the flue gas temperature and composition change when spraying biomass fuel and hydrogen-based gas composite fuel affects the normal production of pellets.

[0024] The biomass raw material of the present invention is at least one of agricultural wastes including corn, rice, wheat, soybean, etc. and forestry wastes including leaves, branches, fruit cores, etc. Biomass carbon, biomass pyrolysis carbon, biomass hydrothermal carbon, etc. are all obtained by processing biomass raw materials using existing common methods.

[0025] The present invention provides a chain grate-rotary kiln pelletizing process biomass-hydrogen-based fuel gas composite heating method, comprising the following steps:

[0026] S1: Add biochar into the pellets, the proportion of biochar is not higher than 5wt.%, mix them evenly with a drum mixer and a strong mixer, then use a disc pelletizer to make pellets, and then screen out qualified pellets with a stick screen and send them to the pelletizing rotary kiln production line for drying, preheating and roasting.

[0027] S2: The solid biomass fuel is sprayed into the rotary kiln through the solid fuel channel of the gas-solid dual-purpose multi-channel spray gun through the pelletizing rotary kiln's pulverizing, storage, transportation and injection system. The hydrogen-based fuel gas is also sent to the gas-solid dual-purpose multi-channel spray gun through the pelletizing rotary kiln's fuel gas pipeline and sprayed into the rotary kiln by the gas fuel.

[0028] S3: A spray gun is added at the connection between the rotary kiln head and the chain grate, and the O2 content of the flue gas in the second stage of the chain grate preheating is controlled at 16-19 vol.%, and the temperature is controlled at 850-1050°C by spraying gas or air through the spray gun.

[0029] The present invention uses abundant biomass resources and hydrogen-based fuel gas with high hydrogen content to perform composite injection of the pelletizing rotary kiln, thereby reducing the dependence of the pelletizing rotary kiln production on high-pollution, high-carbon-emission fossil energy such as coal. The composite injection method of different types of biomass resources and hydrogen-based fuel gas not only solves the unstable fuel supply that may be dealt with when using a single fuel, but also enriches the fuel mode of the pelletizing rotary kiln injection, making it easier to realize the application of biomass resources and hydrogen in pellet preparation. The hot air regulating spray gun is added at the rotary kiln and the chain grate machine, which can flexibly deal with the problem that the pelletizing rotary kiln adopts the biomass fuel-hydrogen-based fuel gas composite heating method to change the flue gas temperature and composition and affect the normal production of pellets. The composite injection of biomass fuel-hydrogen-based fuel gas in the pelletizing rotary kiln can achieve industrial production without changing or simply upgrading the original injection system, with low implementation difficulty, which is conducive to large-scale promotion and application.

[0030] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0031] 1) The present invention incorporates biochar into the pellets to completely or partially replace coke and coal powder to prepare biomass carbon-containing pellets. Since the pellets contain biochar with high activity, the obtained pellets have good reducibility due to their developed void structure, so the ironmaking furnace charge with lower carbon characteristics is obtained. At the same time, a composite fuel structure of biomass fuel and hydrogen-based fuel gas is used for pellet production, which reduces the use of coal resources with high pollution and high emissions, and realizes green production of pellets.

[0032] 2) The present invention adopts the composite injection of biomass fuel and hydrogen-based gas. Although the reserves of biomass fuel are abundant, its production is greatly affected by seasonality. Although the use of biomass fuel for pellet production can reduce carbon emissions, due to the characteristics and output of biomass fuel, its large-scale and long-term use in pellet rotary kiln injection is limited by the fuel supply chain. The composite injection with coke oven gas, hydrogen or composite gas can alleviate the supply pressure of biomass fuel. At present, the production capacity of green hydrogen is relatively low, and the use of solar energy, wind energy and other energy sources for power generation and hydrogen production is also affected by seasons and weather. The rotary kiln only injects hydrogen, which is not only luxurious, but also has the problem of unstable supply. Hydrogen is added to coke oven gas, natural gas, etc., and mixed with biomass fuel for injection, which can realize the large-scale application of biomass energy and hydrogen in the production of pellets, and the roasting temperature of the pellets can be flexibly adjusted by changing the fuel injection structure of gas fuel and solid fuel. Compared with the existing technology of injecting biomass fuel or hydrogen alone, the present invention is more feasible.

[0033] In particular, biomass solid fuel has good gasification performance, and the water vapor with good thermal conductivity in the high-temperature flue gas of hydrogen-based fuel combustion can quickly transfer heat from the high combustion temperature to the biomass solid fuel, gasify the biomass solid fuel into gaseous fuel, and improve the combustion rate of biomass solid fuel. In addition, since the high-humidity flue gas transfers more heat to the pellets, the thermal energy utilization rate of the pellets during roasting is increased, thereby reducing energy consumption and carbon emissions. The high-humidity flue gas formed by the combustion of hydrogen-based fuels can also dissipate the heat released by the fuel combustion in time. In addition, the gasification of biomass gas absorbs heat, which can effectively reduce the peak temperature of the combustion flame and the generation of thermal NOx. Therefore, the rotary kiln adopts the composite injection method of biomass fuel and hydrogen-based fuel gas, which is more advantageous in the clean and efficient preparation of pellets than the single injection of biomass fuel or hydrogen-based fuel.

[0034] 3) When the rotary kiln of the present invention compositely sprays biomass fuel-hydrogen-based fuel, the second stage flue gas composition and temperature of the grate preheating machine will fluctuate, thus affecting the pellet production process. Since the rotary kiln adopts the biomass solid fuel-hydrogen-based fuel composite spraying mode, the original roasting and preheating conditions are changed, and the problem of difficulty in matching the pellet roasting section and the preheating section may occur. Therefore, a spray gun is added at the connection between the rotary kiln head and the grate to heat the flue gas or add cold air, etc., to achieve stable production of pellets. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The invention discloses a process flow of biomass-hydrogen-based fuel gas composite heating in the chain grate-rotary kiln pellet production process.

[0036] Figure 2 Solid fuel particle size distribution and combustion characteristic parameters. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail with reference to the following specific embodiments.

[0038] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0039] Example 1

[0040] In this embodiment, biomass charcoal and coke oven gas were used for the experiment, and pelletizing plant injection coal was also selected for comparison. The industrial analysis, elemental analysis and calorific value of the biomass charcoal used for pelletizing and injection and the pelletizing plant injection coal are shown in Table 1, the ash composition and ash melting characteristic temperature are shown in Table 2 and Table 3, the combustion characteristic parameters are shown in Table 4, and the particle size and combustion characteristics are shown in Table 5. Figure 2 , biomass charcoal with a particle size of less than 74μm was screened for pelletizing. The iron-containing raw materials of the pellets are shown in Table 5. The amount of biomass charcoal added was 1.5wt.%. After mixing and pelletizing, the average drop strength of the raw balls was measured to be 6.2 times / piece. Then, a pelletizing rotary kiln with a rotary kiln diameter of 1.5 meters and a length of 9 meters was used to prepare the finished pellets. The pelletizing rotary kiln production line has an output of 50.3t / h, and the comprehensive energy consumption per ton of pellets is about 23kgce. The hot air temperature blown into the rotary kiln by the ring cooler is 1100-1200℃, and the air volume is about 70,000m 3 / h, the coke oven gas used for injection is composed of 60vol.% hydrogen, 33vol.% methane and a small amount of nitrogen and carbon dioxide, and its calorific value is 18.23MJ / m 3 Biochar and coke oven gas are injected into the rotary kiln by the raw fuel injection system through a gas-solid dual-purpose multi-channel burner. The coke oven gas carrier gas is room temperature air. The scheme and injection amount of coke oven gas and biochar are shown in Table 6. The amount of air injected by the spray gun is about 3100m 3 / h. The flue gas temperatures at the outlet of the rotary kiln head of schemes 1# to 3# were measured to be 956, 964 and 968℃. This is because the higher the proportion of coke oven gas, the better the heat transfer capacity of its combustion flue gas to the pellets. Since the high-temperature flue gas transfers more heat to the rotary kiln, the flue gas temperature at the outlet of the rotary kiln head will be lower. The flue gas components at the outlet of the preheated rotary kiln under each scheme were measured and compared with the cases of single impact blowing of pulverized coal and coke oven gas. The results are shown in Table 7. It can be seen that the composite heating mode using biomass charcoal and coke oven gas does not change the roasting atmosphere formed by using traditional fuels. However, the amount of CO2 in the flue gas is significantly lower than that of coal injection. In addition, biomass charcoal is a carbon-neutral fuel, and the CO2 released by its combustion is not included in the total amount of CO2 produced by industrial production. Therefore, the composite heating mode using biomass-hydrogen-based fuel has a significant carbon emission reduction effect, and as the injection amount of biomass charcoal increases, the carbon reduction effect is more significant. Since N and S in the fuel are the main sources of NOx and SO2 in the flue gas, the low N and S content in biomass fuel and coke oven gas determines that their combustion exhaust is cleaner than coal. In order to control the temperature of the flue gas at the outlet of the rotary kiln above 1000℃, a calorific value of 18.56MJ / m 3 Biomass pyrolysis is used as flue gas heating fuel. When the biomass gas injection volume is 50m 3 / h, all three schemes can raise the flue gas temperature to above 1000℃. The indicators of finished pellets under different heating modes were measured, and the results are shown in Table 8. The indicators of the obtained pellets are very similar to those of the pellets produced under the mode of only blowing coke oven gas and pulverized coal.

[0041] Table 1 Industrial analysis and elemental analysis of biochar (dry basis)

[0042]

[0043] Table 2 Ash composition of solid fuel

[0044]

[0045] Table 3 Fuel ash melting characteristic temperature

[0046]

[0047] Table 4 Combustion characteristic parameters of the samples

[0048]

[0049]

[0050] Table 5 Iron-containing raw materials

[0051]

[0052] Table 6 Schemes and injection rates of coke oven gas and biochar

[0053]

[0054] Table 7 Smoke composition

[0055]

[0056] Table 8 Finished ball index

[0057]

[0058] Example 2

[0059] Example 2 is based on the same conditions as Example 1, but the hydrogen-based fuel used has a calorific value of 35.6 MJ / m 3The schemes and injection amounts of natural gas, natural gas and biochar are shown in Table 9. The flue gas temperatures at the outlet of the rotary kiln heads of schemes 4# to 6# were measured by thermocouples to be 988, 993 and 1013°C. Since the temperature is close to 1000°C and is within a reasonable range, fuel is not injected at the connection between the rotary kiln and the grate. The flue gas composition at the outlet of the preheating rotary kiln under each scheme was measured and compared with the case of single impact blowing of pulverized coal and coke oven gas. The results are shown in Table 10. It can be seen that the composite heating mode of biomass charcoal and natural gas does not change the roasting atmosphere formed by heating with natural gas and pulverized coal alone, but the CO2 content in the flue gas is significantly reduced compared with the injection of pulverized coal. In addition, biomass charcoal is a carbon-neutral fuel, and the CO2 released by its combustion is not included in the total CO2 produced by industrial production. Therefore, the composite heating mode of biomass-hydrogen-based fuel has a significant carbon emission reduction effect. Since N and S in the fuel are the main sources of NOx and SO2 in the flue gas, the low N and S content in biomass fuel and natural gas determines that its combustion tail gas is cleaner than coal. In addition, the indicators of finished pellets under different heating modes were measured, and the results are shown in Table 11. In addition, the various indicators of the pellets are very similar to the quality of the pellets produced in the mode of only injecting pulverized coal / natural gas.

[0060] Table 9 Schemes and injection rates of natural gas and biochar

[0061]

[0062] Table 10 Smoke composition

[0063]

[0064] Table 11 Finished ball index

[0065]

Claims

1. A biomass-hydrogen-based fuel gas composite heating method using a grate-rotary kiln pelletizing process, characterized in that: In the chain grate-rotary kiln pellet production process, the operation steps including A, B and C are carried out: A: Biomass charcoal is mixed with pellets to make pellets; B: Spraying biomass solid fuel and hydrogen-based fuel gas simultaneously in the rotary kiln; C: Gas and / or air is sprayed at the connection between the chain grate and the kiln head of the rotary kiln to regulate the oxygen content and temperature of the flue gas in the second preheating stage.

2. The method for composite heating of biomass and hydrogen-based fuel gas by grate-rotary kiln pelletizing process according to claim 1, characterized in that: The biochar is added to the pellets in a proportion of 0.1-2 wt.%.

3. A biomass-hydrogen-based fuel gas composite heating method using a grate-rotary kiln pelletizing process according to claim 1 or 2, characterized in that: The volume proportion of the biochar particle size being less than 74 microns is not less than 80%.

4. A method for composite heating of biomass and hydrogen-based fuel gas by a grate-rotary kiln pelletizing process according to claim 1 or 2, characterized in that: The biochar has a fixed carbon mass content greater than 65%, an ash mass content less than 5%, a volatile matter calorific value greater than 28 MJ / kg, a combustion start temperature greater than 400° C., a gasification start temperature greater than 600° C., a potassium mass content less than 1%, and a chlorine mass content less than 0.1%.

5. The method for composite heating of biomass and hydrogen-based fuel gas by grate-rotary kiln pelletizing process according to claim 1, characterized in that: The biomass solid fuel includes at least one of biomass raw materials, biomass pyrolysis charcoal, and biomass hydrothermal charcoal, and / or at least one of biomass raw material upgraded products, biomass pyrolysis charcoal upgraded products, and biomass hydrothermal charcoal upgraded products.

6. The method of chain grate-rotary kiln pelletizing process biomass-hydrogen-based fuel gas composite heating according to claim 5, characterized in that: The ash content of the biomass pyrolysis char, the biomass pyrolysis char upgraded product, the biomass hydrothermal char and the biomass hydrothermal char upgraded product is less than 10%, the ash melting point exceeds 1300°C, the volatile matter content is less than 40%, the calorific value is greater than 25MJ / kg, the K content is controlled below 2%, the Cl content is controlled below 0.5%, the starting combustion temperature is controlled between 300 and 420°C, and the comprehensive combustion characteristic index is not less than 0.50×10 -12 s -2 .℃ -3 The burning intensity is not less than 4.8×10 -4 s -1 ; The water content of the biomass raw material and the biomass raw material upgraded product is lower than 5%, the ash content is lower than 3%, the ash melting point is not lower than 2500°C, the K content is controlled below 1%, and the Cl content is controlled below 0.1%.

7. A biomass-hydrogen-based fuel gas composite heating method using a grate-rotary kiln pelletizing process according to claim 5 or 6, characterized in that: The particle size of the biomass solid fuel meets the following requirements: the volume proportion of particles smaller than 150 μm exceeds 50%, and the volume proportion of particles smaller than 250 μm exceeds 90%.

8. A method for composite heating of biomass and hydrogen-based fuel gas by grate-rotary kiln pelletizing process according to claim 1, 5 or 6, characterized in that: When the biomass solid fuel is at least one of biomass pyrolysis charcoal, biomass pyrolysis charcoal upgraded product, biomass hydrothermal charcoal and biomass hydrothermal charcoal upgraded product, the heat supply ratio thereof accounts for 1 to 99% of the total heat supply of the fuel sprayed into the rotary kiln; When the biomass solid fuel adopts biomass raw materials and / or biomass raw material upgraded products, its heat supply ratio accounts for less than 50% of the total heat supply of the fuel sprayed into the rotary kiln.

9. The method of chain grate-rotary kiln pelletizing process biomass-hydrogen-based fuel gas composite heating according to claim 1, characterized in that: The hydrogen-based fuel gas includes at least one of hydrogen, coke oven gas, natural gas and biomass gas.

10. The method of chain grate-rotary kiln pelletizing process biomass-hydrogen-based fuel gas composite heating according to claim 1, characterized in that: Gas and / or air is sprayed at the connection between the chain grate and the rotary kiln head to adjust the oxygen volume content of the flue gas in the second preheating stage to 16-19% and the temperature to 850-1050°C.

Images