Method for co-producing direct reduced iron based on dry powder coal pressurized gasification furnace

Abstract

The invention relates to a method for co-producing direct reduced iron based on a dry powder coal pressurized gasification furnace, which comprises the following steps: producing high-temperature raw gas with the pressure of 0.6-1.2 MPa and the temperature of 1450-1600 DEG C by adopting the dry powder coal pressurized gasification furnace, adding hydrogen with the temperature of 300-400 DEG C to obtain reducing gas with the temperature of 850-950 DEG C, and feeding the reducing gas into a DRI reduction shaft furnace to produce the direct reduced iron, and the produced furnace top gas with the pressure of 0.6-1.2 MPa and the temperature of 350-500 DEG C is subjected to heat exchange with normal-temperature hydrogen, the temperature is adjusted to 190-210 DEG C, CO conversion is carried out to obtain normal-temperature conversion hydrogen, the normal-temperature conversion hydrogen exchanges heat with the furnace top gas and then is added into the high-temperature raw gas to obtain reducing gas, and the process is cycled. According to the method, the direct reduced iron is co-produced through capacity expansion and pressure reduction of the dry powder coal pressurized gasification furnace, so that low energy consumption of the coal gas direct reduced iron is realized, and zero carbon emission is realized on the basis of capturing and recycling CO2.

Description

Technical Field

[0001] The invention belongs to the technical field of direct reduced iron production, and relates to a method for smelting direct reduced iron by utilizing high-temperature raw coal gas from coal gasification, and in particular to a method for smelting direct reduced iron by utilizing high-temperature raw coal gas from a dry pulverized coal pressurized gasifier. Background Art

[0004] Conventional coal-to-gas direct iron reduction is to cool the 1100-1800℃ high-temperature raw coal gas from coal pyrolysis, remove dust, desulfurize, decarbonize, reform, and then heat it to 850-950℃ and feed it into the direct iron reduction vertical furnace for the production of direct reduced iron. In this way, about 17% of the sensible heat of the raw coal gas from coal pyrolysis cannot be used for iron reduction, and the reheating of the purified coal gas accounts for about 25-35% of the input energy. The cooling, purification, and reheating of the coal gas alone consume 32-52% of the input energy. This is the main reason for the high energy consumption, heavy pollution, and high carbon emissions of coal-to-gas direct iron reduction.

[0005] The known dry pulverized coal pressurized gasification furnaces mainly include Huaneng furnace (two-stage dry pulverized coal pressurized gasification furnace), Wuhuan furnace, Shell furnace, etc. This type of coal gasification furnace uses pure oxygen to pressurize coal gasification, mainly by increasing the coal gasification pressure and temperature to enhance the decomposition and gasification of coal. Generally, the gasification pressure reaches more than 3MPa. This pressure is very necessary for coal chemical industry, because the subsequent processes of coal gas purification, CO conversion, desulfurization, chemical synthesis, etc. all require high pressure. The high-pressure operation of the whole system can reduce the equipment manufacturing cost and operating cost, and significantly save energy and reduce consumption.

[0006] However, the existing gas-based direct reduced iron vertical furnace gas pressure is only ≤0.8MPa. Although HYL-Ⅲ promises to use 1.2MPa pressure gas to produce direct reduced iron, there is no engineering example. Therefore, the current consensus in the industry is that dry pulverized coal pressurized gasifier is not suitable for co-production of direct reduced iron.

[0007] In the production practice of Huaneng furnace, it is found that when the gas pressure drops to 0.6MPa, although the production can still run continuously, the coal processing capacity drops by 2 / 3, that is, the gas output drops by 2 / 3. If direct reduced iron is co-produced, the output will also be reduced by 2 / 3. For the production of coal chemical products and IGCC coal gasification gas steam combined power generation projects, it is obviously unacceptable that the equipment production capacity can only be utilized at 1 / 3.

[0008] The oxidation degree of the raw gas from the dry pulverized coal pressurized gasifier is low, generally ≤5%, and does not contain harmful substances such as tar, benzene, phenol, etc. Although the CO content is as high as 63% or more, it is still very suitable for direct reduction of iron after being tempered by adding hydrogen to increase the hydrogen-carbon ratio. On the contrary, the raw gas from water-coal slurry gasification contains high H2O and high oxidation degree, and its high-temperature raw gas sensible heat is not suitable for the production of direct reduction iron. Summary of the invention

[0009] The purpose of the present invention is to provide a method for co-producing direct reduced iron based on a dry pulverized coal pressurized gasifier, so as to overcome the prejudice of the prior art and realize the production of direct reduced iron with the high-temperature raw coal gas produced by the dry pulverized coal pressurized gasifier.

[0010] To achieve the above-mentioned purpose of the invention, the method for co-producing direct reduced iron based on dry pulverized coal pressurized gasification furnace provided by the present invention specifically includes the following process:

[0011] 1) Carry out decompression operation on the existing dry pulverized coal pressurized gasifier, reducing the pressure from 3MPa to 0.6MPa~1.2MPa, and reducing the output to obtain 1 / 3 of the original output volume of 0.6MPa~1.2MPa high-temperature raw coal gas at 1450℃~1600℃;

[0012] 2) Remove the high-temperature gas waste heat boiler connected to the dry pulverized coal pressurized gasifier for heat exchange with the high-temperature gas to produce water vapor and normal-temperature gas, and connect a DRI reduction shaft furnace that matches the output of the high-temperature raw gas of the dry pulverized coal pressurized gasifier;

[0013] 3) Adding 300℃~400℃ hydrogen to the high-temperature raw coal gas of 1450℃~1600℃ with a pressure of 0.6MPa~1.2MPa produced by the dry pulverized coal pressurized gasifier to cool and temper it to 850℃~950℃, and keeping the pressure at 0.6MPa~1.2MPa. After dust removal by the dust collector, the DRI reduction shaft furnace reduction gas is obtained, which is directly sent to the DRI reduction shaft furnace for the production of direct reduced iron;

[0014] 4) The DRI reduction vertical furnace top produces 350℃~500℃ top gas with a pressure of 0.6MPa~1.2MPa. After dust removal by the dust collector, it enters the top gas heat exchanger, exchanges heat with normal temperature hydrogen, and then goes through water washing and electrostatic precipitator. The temperature is adjusted to 190℃~210℃ and enters the top gas conversion hydrogen process. Conventional CO conversion, desulfurization and gas separation technology are used to obtain normal temperature conversion hydrogen with H2 content ≥98%, oxidation degree ≤3%, temperature <40℃ and pressure maintained at 0.6MPa~1.2MPa.

[0015] 5) Normal temperature conversion hydrogen is heat exchanged with 350℃~500℃ furnace top gas with a pressure of 0.6MPa~1.2MPa in the furnace top gas heat exchanger, preheated to 300℃~400℃, and added to the high temperature raw gas with a temperature of 1450℃~1600℃. The high temperature raw gas is adjusted to have a hydrogen-carbon ratio of ≥1.7, an oxidation degree of <5%, a sulfur content of <0.1%, a temperature of 850℃~950℃, and a pressure of 0.6MPa~1.2MPa. After dust removal by a dust collector, the DRI reduction shaft furnace reduction gas is obtained;

[0016] 6) The reducing gas from the DRI reduction shaft furnace is directly fed into the DRI reduction shaft furnace to provide heat and reducing agent for the iron oxide pellets to produce direct reduced iron, and the top gas with a temperature of 350℃~500℃ and a pressure of 0.6MPa~1.2MPa is produced from the top of the DRI reduction shaft furnace.

[0017] As is known, the coal gas produced by the existing dry pulverized coal pressurized gasification furnace cannot be directly used to produce direct reduced iron. For example, when the coal gas pressure is ≥3MPa and the coal gas temperature is ≥1100°C, it cannot be directly connected to the gas-based direct reduced iron vertical furnace. However, the coal gas pressure of 0.6MPa to 1.2MPa is suitable for connecting to the gas-based direct reduced iron vertical furnace for the production of direct reduced iron. Therefore, the present invention reduces the coal gas pressure of the dry pulverized coal pressurized gasification furnace to 0.6MPa to 1.2MPa for the production of direct reduced iron. However, the decompression operation is bound to cause a reduction in the production capacity of the dry pulverized coal pressurized gasification furnace. For this reason, the present invention adopts the method of "capacity expansion and decompression", where decompression is the purpose and capacity expansion is the condition. Capacity expansion can increase the gas output of the dry pulverized coal pressurized gasification furnace, thereby compensating for the capacity loss caused by the decompression operation.

[0018] The capacity expansion of the existing dry pulverized coal pressurized gasification furnace can be achieved by increasing the furnace body height or furnace body diameter. For example, for a two-stage dry pulverized coal pressurized gasification furnace such as Huaneng furnace, the upper furnace can be removed and changed to a one-stage furnace, and the lower furnace occupies the furnace height of the two-stage furnace, and the height is increased to achieve capacity expansion. The original upper furnace spraying coal powder and water vapor is an endothermic reaction, which uses the high temperature generated by the oxidation reaction of the coal in the lower furnace to provide heat for the pyrolysis reaction of the coal in the upper furnace, but this also directly leads to a decrease in the gas temperature, which is beneficial to coal chemical industry, because coal chemical industry itself does not need this part of sensible heat, and it can only be used as waste heat. After removing the upper furnace, the present invention no longer sprays coal powder and water vapor into the upper furnace, and uses this part of heat to reduce iron, which is the essential difference between coal chemical industry and ironmaking. At the same time, by increasing the cross-sectional area of ​​the furnace body, the coal powder processing capacity and coal gas output can be increased under the condition that the furnace height remains unchanged, so as to expand the furnace capacity to compensate for the decrease in coal powder processing capacity caused by the pressure reduction operation and the loss of production capacity caused by the reduction in coal gas production.

[0019] As for the coal gas temperature, for example, the coal gas cooling method adopted by Huaneng furnace is to spray coal powder and water vapor into the high-temperature coal gas of ≥1450℃ in the upper furnace, thereby increasing the coal gas production while lowering the coal gas temperature. Generally, the coal gas temperature can be reduced to ≥1000℃, and then the waste heat is recovered by the waste heat boiler to produce water vapor. The coal gas is washed with water, electrostatic precipitator and desulfurized to obtain purified coal gas; water vapor drives the steam turbine, the steam turbine drives the generator to generate electricity; the purified coal gas drives the gas turbine, and the gas turbine drives the generator to generate electricity; gas-steam combined cycle power generation (IGCC) is realized.

[0020] The present invention is different from the above in that the high-temperature coal gas produced by the dry pulverized coal pressurized gasification furnace is all used for the production of direct reduced iron. The coal gas temperature required for direct reduction of iron by the gas-based method is 850°C to 950°C. The coal gas cooling method adopted by the present invention is to convert the top coal gas of the DRI reduction shaft furnace into hydrogen, preheat it to 300°C to 400°C through the top coal gas heat exchanger, and then add it to the high-temperature raw coal gas of 1450°C to 1600°C, and reduce the temperature of the mixed coal gas to 850°C to 950°C, and use it for the production of direct reduced iron after dust removal.

[0021] Based on the above two technical transformations, the method of expanding and reducing pressure of dry pulverized coal pressurized gasification furnace for co-production of direct reduced iron proposed in the present invention realizes low energy consumption of direct reduced iron from coal gasification, and achieves the goal of zero carbon emissions based on the capture and recycling of CO2.

[0022] The dry pulverized coal pressurized gasification furnace described in the present invention uses coal powder and oxygen as energy sources. Coal powder and a necessary amount of desulfurizer are sprayed into the dry pulverized coal pressurized gasification furnace through a spray gun through the conveying gas N2 and / or CO2, and oxygen is sprayed into the dry pulverized coal pressurized gasification furnace at the same time. The output gas is a high-temperature raw coal gas with a gas temperature of 1450°C to 1600°C, a pressure of 0.6MPa to 1.2MPa, and an oxidation degree of ≤8%.

[0023] In the co-production process of the present invention, desulfurization of coal gas is also very important. Among them, the desulfurizer used for desulfurization in the dry pulverized coal pressurized gasifier can be one or more of lime powder, limestone powder, and dolomite powder. For the DRI reduction shaft furnace, while introducing hydrogen-rich gas, part of the sulfur in the iron ore can be removed. The desulfurization of the top gas of the DRI reduction shaft furnace can be carried out using conventional coal chemical desulfurization technology.

[0024] Furthermore, the raw material iron oxide pellets used for producing direct reduced iron in the DRI reduction shaft furnace of the present invention may also be mixed with iron ore lumps of corresponding particle sizes.

[0025] Different from the applicant's previous patent application, the present invention converts the CO in the top gas of the DRI reduction vertical furnace into hydrogen, and then adds it to the high-temperature raw coal gas of 1450℃~1600℃ with a pressure of 0.6MPa~1.2MPa produced by the "expansion and pressure reduction" of the dry pulverized coal pressurized gasification furnace, and adjusts the gas temperature to 850℃~950℃, so as to provide heat and reducing agent for the DRI reduction vertical furnace to produce direct reduced iron.

[0026] The "method for producing direct reduced iron by utilizing the sensible heat of raw coal gas" disclosed in CN 201010124542.1 uses the high-temperature raw coal gas of a two-stage dry pulverized coal pressurized gasification furnace to provide heat for iron ore coal pellets. The two-stage dry pulverized coal pressurized gasification furnace including the upper furnace is fully adopted. The reducing agent used is the coal powder in the iron ore coal pellets to produce direct reduced iron. The disadvantage is that the ash in the coal powder enters the direct reduced iron, and the quality of the direct reduced iron is affected.

[0027] The "method for preheating and converting hydrogen by direct iron reduction furnace top gas" disclosed in CN 202110543283.4 and the "method for direct iron reduction by producing hydrogen through molten iron bath coal gasification" applied for CN 202210791215.4 both connect the direct iron reduction vertical furnace with the molten iron bath coal gasification furnace. The gas pressure of the molten iron bath coal gasification furnace is ≤0.5MPa, and both iron and slag are produced when producing coal gas. The dry pulverized coal pressurized gasification furnace of the present invention only produces slag but not iron when producing coal gas, and the coal gas pressure is increased to 0.6MPa~1.2MPa.

[0028] Another feature of the method of the present invention is that CO2 produced in the process of co-producing direct reduced iron in the dry pulverized coal pressurized gasifier can replace or partially replace water vapor as a coal gasification agent in the dry pulverized coal pressurized gasifier to reduce carbon emissions.

[0029] The function of water vapor in coal gasification reaction (C+H2O=H2+CO, ΔH=122.67kJ / mol) is firstly to regulate temperature. According to tests, the temperature of pure oxygen dry pulverized coal pressurized gasification furnace can reach 2200℃, which cannot be used directly. Using water vapor as coal gasification agent can pyrolyze coal, reduce coal gas temperature and increase H2 content in coal gas.

[0030] Similarly, the function of CO2 in coal gasification reaction (C+CO2=2CO, ΔH=172.5kJ / mol) is to pyrolyze coal, reduce the gas temperature and increase the CO content in the gas. The advantage of using CO2 as a coal gasification agent is that a large amount of self-produced CO2 is produced in the present invention, and this part of CO2 can realize carbon recycling and reduce carbon emissions.

[0031] It should be pointed out that when CO2 is used as a coal gasification agent, the coal gas temperature must be kept between 1450°C and 1600°C. O2 is the main oxidant and coal gasification agent for increasing the coal gas temperature, and the ratio of O2 to CO2 must be strictly controlled, with the volume ratio of CO2 to the coal gasification agent not exceeding 12%.

[0032] Furthermore, the CO2 produced by the present invention can be used as a carbon source, converted into CO by reacting with hydrogen (CO2+H2=CO+H2O), and used as a raw gas to produce chemical products, so as to achieve the purpose of zero carbon emission of the present invention.

[0033] One source of hydrogen in the present invention is the hydrogen obtained by DRI reduction of vertical furnace top gas through CO conversion, which is used to add to high-temperature raw coal gas for cooling and conditioning. The second source is the hydrogen produced when O2 is produced by electrolysis of water and used as an oxidant in a dry pulverized coal pressurized gasifier.

[0034] Furthermore, the process of electrolyzing water to produce hydrogen and oxygen described in the present invention adopts the green electricity to green hydrogen process, which ensures that no CO2 is produced in the hydrogen production process. The CO2 produced in the process of the present invention is treated with green hydrogen (H2+CO2=CO+H2O) to convert CO2 into CO for reuse, thereby achieving zero carbon emissions in the entire process. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a process flow chart of the dry pulverized coal pressurized gasification furnace for co-producing direct reduced iron. Implementation

[0036] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solution of the present invention so that those skilled in the art can well understand and utilize the present invention, rather than limiting the scope of protection of the present invention.

[0037] The production processes, experimental methods or detection methods involved in the embodiments of the present invention, unless otherwise specified, are all conventional methods in the prior art, and their names and / or abbreviations are all conventional names in the field, and are very clear and unambiguous in the relevant application fields. Technical personnel in the field can understand the conventional process steps based on the names and apply the corresponding equipment, and implement them according to conventional conditions or the conditions recommended by the manufacturer.

[0038] The various instruments, equipment, raw materials or reagents used in the embodiments of the present invention are not particularly limited in terms of their sources, and are all conventional products that can be purchased through regular commercial channels, or can be prepared according to conventional methods well known to those skilled in the art. Example

[0039] like Figure 1As shown, the upper furnace of the Huaneng two-stage dry pulverized coal pressurized gasification furnace is removed for spraying pulverized coal and water vapor, the furnace capacity of the upper furnace is retained, and the upper and lower furnaces are combined into a one-stage dry pulverized coal pressurized gasification furnace.

[0040] The oxidant and gasifying agent O2+H2O of the dry pulverized coal pressurized gasifier is changed to O2+CO2, and the coal injection amount and oxygen injection amount are reduced by 2 / 3, the gas pressure is reduced from ≥3MPa to 0.6MPa, the temperature of the raw gas is controlled to reach 1500℃, and normal temperature H2 is added to reduce the gas temperature to 850℃. After dust removal by the dust collector, a gas with a hydrogen-carbon ratio of ≥1.7, an oxidation degree of ≤5%, and a sulfur content of ≤0.1% is obtained and sent to the DRI reduction vertical furnace for the production of direct reduced iron.

[0041] The 400℃ DRI reduction vertical furnace top gas is dedusted by a metal membrane or ceramic dust collector, and then the gas temperature is reduced to ≤200℃ by a heat exchanger. After water washing, compressor pressurization, and electrostatic precipitator, it enters the CO conversion H2 process to produce conversion gas. CO conversion H2 is an exothermic reaction. Water vapor is recovered by the conversion gas heat exchanger. After desulfurization and cooling, the conversion gas enters the PSA pressure swing adsorption gas separation process to separate H2, CO2, and N2 at room temperature. CO2 is captured and recovered, and N2 is used or discharged.

[0042] The purified room temperature H2 is adjusted to 6MPa and enters the DRI reduction vertical furnace top gas heat exchanger, where the H2 is preheated to 350°C and added to the 1500°C raw gas produced by the dry pulverized coal pressurized gasification furnace. The gas temperature is adjusted to 850°C and sent to the DRI reduction vertical furnace.

[0043] The above process utilizes crude coal gas for sensible heat smelting of direct reduced iron. The 1% CH4 contained in the crude coal gas can be pyrolyzed under high temperature conditions in the DRI reduction vertical furnace with reduced iron as a catalyst. Therefore, there is no need to set up a reforming furnace, thus eliminating the need for a reducing gas reforming furnace or a heating furnace.

[0044] The water vapor that can be recycled in the above process includes the high-pressure water vapor produced as a by-product of the dry pulverized coal pressurized gasification furnace, the water vapor recovered by the top gas heat exchanger of the DRI reduction vertical furnace, the water vapor recovered by the CO conversion H2 heat exchanger, the water vapor recovered by the cooling section of the DRI reduction vertical furnace, etc. The high-pressure water vapor can be used to drive the reduction gas compressor, and the other pressurized water vapor can be used for CO conversion to produce H2.

[0045] Treatment of waste residue, waste gas and wastewater in the above process: The gas from the dry pulverized coal pressurized gasifier does not contain harmful substances such as tar, benzene, phenol, etc. After the gas passes through the DRI reduction shaft furnace, dry dust removal is set before the water-washed gas. Therefore, the water-washed gas wastewater mainly contains fine dust particles. After the wastewater is purified, it can be recycled and does not need to be discharged. The dust recovered by each section of the dust collector is concentrated and returned to the gasifier for treatment or utilization. The carbon content of the gasifier slag is less than 1%, which can be used to prepare cement, make slag bricks, etc. Since the reduction gas reforming furnace or heating furnace is cancelled, there is no combustion waste gas emission, and only N2 after the conversion gas separation is emitted.

[0046] The specific process parameters of the process of the present invention are given below based on the coal powder processing capacity of the dry pulverized coal pressurized gasification furnace being 23.2 t / h.

[0047] 1. Coal gas produced by dry pulverized coal pressurized gasification furnace with a pulverized coal processing capacity of 23.2t / h

[0048] Total gas volume 45870m 3 / h, where the reducing gas is (CO 28898+H211009)m 3 / h.

[0049] The oxidation degree of raw coal gas is 7.4%.

[0050] 1500℃ raw gas sensible heat S :101806718kJ / h.

[0051] Low calorific value of cold gas: S 483778481 kJ / h, average 12123 kJ / m 3 .

[0052] 2. Add normal temperature hydrogen to high temperature raw coal gas

[0053] Reducing gas in raw coal gas (H2+CO) 39907m 3 / h.

[0054] Theoretically, 580m3 of reducing gas is required to reduce iron 3 / t.DRI, generally 600m 3 / t.DRI calculation; the actual production data requires the flow rate of 850℃ reducing gas to be 1600m 3 / t.DRI, so at least 1600m of loop is required 3 ÷600m 3 ≈2.7 times.

[0055] According to the calculation of three cycles, each cycle produces hydrogen converted from the DRI reduction vertical furnace top gas. The amount of the third output cycle reduction gas (converted hydrogen) is calculated as:

[0056] The oxidation degree of the reducing gas after adding the converted hydrogen is about 3.05%.

[0057] To reduce the sulfur content in the raw coal gas, lime powder and limestone powder are mainly sprayed into the coal gasifier. Adding hydrogen to the raw coal gas can further dilute the sulfur in the reducing gas, dilute the oxidizing gas, and reduce the temperature of the raw coal gas.

[0058] 3. Reduction gas after adding conversion hydrogen

[0059] The enthalpy of the reducing gas entering the DRI reduction shaft furnace after adding 350°C hydrogen to the 1500°C raw coal gas is:

[0060] Q (1500℃+350℃) =( S kJ / h) / ( S m 3 / h) = (1500℃ raw gas enthalpy + 350℃ hydrogen enthalpy) ÷ (1500℃ raw gas volume + 350℃ converted hydrogen volume) ≈ 1203kJ / m 3 ;

[0061] Gas volume into DRI reduction shaft furnace: 108125m 3 / h;

[0062] Entering DRI reduction vertical furnace 850℃ enthalpy: 125414984kJ / h;

[0063] Q 850℃ =( S kJ / h) / ( S m 3 / h)≈1160kJ / m 3 ;

[0064] X = Q (1500℃+350℃) / Q 850℃ =1203÷1160≈1.0371;

[0065] Q (1500℃+350℃) = Q 850℃ ×1.0371≈882℃.

[0066] After adding 350℃ hydrogen preheated by the gas heat exchanger on the top of the DRI reduction shaft furnace into the 1500℃ coal gas of the dry pulverized coal pressurized gasifier, it is calculated that the reducing gas temperature entering the DRI reduction shaft furnace can reach 882℃.

[0067] The hydrogen-carbon ratio of the reducing gas entering the DRI reduction vertical furnace is H2:CO=2.5, and hydrogen accounts for 67.6% of the reducing gas entering the furnace.

[0068] 4. Comparison of gas indicators entering DRI reduction shaft furnace

[0069] Low-sulfur coal with a sulfur content of ≤0.6% is selected for gasification, and hydrogen is added to the raw gas before being sent to the DRI reduction shaft furnace. The sulfur content of the gas can be diluted to 0.1%, about 1000ppm, which does not meet the MIDREX requirement of 100ppm sulfur content in the furnace gas. However, since the sulfur content of the first stage furnace gas of Huaneng furnace accounts for 90% of H2S and only 10% of COS, even if the gas is not reformed, it will not cause corrosion to the equipment. Therefore, the reduced gas after adding hydrogen can be directly used to produce DRI.

[0070]

[0071] 5. DRI production

[0072] The design of reducing gas to reduce iron does not generate (CO2+H2O) and is not discharged from the process. According to the direct reduction of iron, the reducing gas required is 600m 3 / t.DRI calculation: 67t.DRI / h; annual output 514560t.DRI / a.

[0073] Consumption-based circulating reduction gas volume 1600m 3 / t.DRI calculated DRI output: 68t.DRI / h; annual output 522240t.DRI / a.

[0074] The results of the two calculation methods are very close.

[0075] 6. Energy consumption estimation

[0076] Coal calorific value for Huaneng Tianjin IGCC: median value 5708 kCal, equivalent to 0.8154 tce of standard coal; oxygen consumption 511 m 3 O2 / t. coal.

[0077] The energy input per hour is 20.4585 tce / h, and the annual energy input is 157,121 tce / a.

[0078] Sensible heat of hydrogen recovery at 350℃: 453.3kJ / m 3 ×62353m 3 / h÷29302kJ / kg≈0.9646tce / h; accounting for about 4.83% of the input energy.

[0079] Utilizing the sensible heat of raw coal gas: 101806718 kJ / h÷29302 kJ / kg≈3.4744 tce / h; accounting for about 16.98% of the input energy.

[0080] 7. Energy consumption

[0081] Process energy consumption: 20.4585tce / h÷67t.DRI / h≈305.4kgce / t.DRI.

[0082] Comparable energy consumption: 305.4kgce / t.DRI+28kgce(pelletizing energy consumption)+electricity consumption 11kgce≈344.4kgce / t.DRI.

[0083] The comparable energy consumption is 29.1kgce lower than MIDREX's 373.5kgce.

[0084] 8. Carbon dioxide emissions reduction

[0085] Calculated based on the comparable energy consumption of ironmaking, CO2 output is 176kgCO2 / t of hot metal lower than that of blast furnaces. Carbon emissions within the industry are 487kgCO2 / t of hot metal lower than that of blast furnaces.

[0086] Compared with natural gas MIDREX, the dry pulverized coal pressurized gasification furnace co-produces direct reduced iron. Since the reforming furnace heated by gas is removed, there is no combustion exhaust gas emission. Therefore, the pollutant emission is lower than MIDREX, the CO2 emission from full capture and recovery is lower than MIDREX, and the energy consumption is lower than MIDREX.

[0087] The above embodiments of the present invention do not describe all the details in detail, nor limit the present invention to the above embodiments. Various changes, modifications, substitutions and variations made by ordinary technicians in this field without departing from the principles and purpose of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for co-producing direct reduced iron based on a dry pulverized coal pressurized gasifier, comprising: 1) Carry out decompression operation on the existing dry pulverized coal pressurized gasifier, reducing the pressure from 3MPa to 0.6MPa~1.2MPa, and reducing the output to obtain 1 / 3 of the original output volume of 0.6MPa~1.2MPa high-temperature raw coal gas at 1450℃~1600℃; 2) Remove the high-temperature gas waste heat boiler connected to the dry pulverized coal pressurized gasifier for heat exchange with the high-temperature gas to produce water vapor and normal-temperature gas, and connect a DRI reduction shaft furnace that matches the output of the high-temperature raw gas of the dry pulverized coal pressurized gasifier; 3) Adding 300℃~400℃ hydrogen to the high-temperature raw coal gas of 1450℃~1600℃ with a pressure of 0.6MPa~1.2MPa produced by the dry pulverized coal pressurized gasifier to cool and temper it to 850℃~950℃, and keeping the pressure at 0.6MPa~1.2MPa. After dust removal by the dust collector, the DRI reduction shaft furnace reduction gas is obtained, which is directly sent to the DRI reduction shaft furnace for the production of direct reduced iron; 4) The DRI reduction vertical furnace top produces 350℃~500℃ top gas with a pressure of 0.6MPa~1.2MPa. After dust removal by the dust collector, it enters the top gas heat exchanger, exchanges heat with normal temperature hydrogen, and then goes through water washing and electrostatic precipitator. The temperature is adjusted to 190℃~210℃ and enters the top gas conversion hydrogen process. Conventional CO conversion, desulfurization and gas separation technology are used to obtain normal temperature conversion hydrogen with H2 content ≥98%, oxidation degree ≤3%, temperature <40℃ and pressure maintained at 0.6MPa~1.2MPa. 5) Normal temperature conversion hydrogen is heat exchanged with 350℃~500℃ furnace top gas with a pressure of 0.6MPa~1.2MPa in the furnace top gas heat exchanger, preheated to 300℃~400℃, and added to the high temperature raw gas with a temperature of 1450℃~1600℃. The high temperature raw gas is adjusted to have a hydrogen-carbon ratio of ≥1.7, an oxidation degree of <5%, a sulfur content of <0.1%, a temperature of 850℃~950℃, and a pressure of 0.6MPa~1.2MPa. After dust removal by a dust collector, the DRI reduction shaft furnace reduction gas is obtained; 6) The reducing gas from the DRI reduction shaft furnace is directly fed into the DRI reduction shaft furnace to provide heat and reducing agent for the iron oxide pellets to produce direct reduced iron, and the top gas with a temperature of 350℃~500℃ and a pressure of 0.6MPa~1.2MPa is produced from the top of the DRI reduction shaft furnace.

2. The method for co-producing direct reduced iron based on dry pulverized coal pressurized gasification furnace according to claim 1, characterized in that The dry pulverized coal pressurized gasification furnace uses coal powder and oxygen as energy sources. Coal powder and a necessary amount of desulfurizer are sprayed into the dry pulverized coal pressurized gasification furnace through a spray gun through the conveying gas N2 and / or CO2, and oxygen is sprayed into the dry pulverized coal pressurized gasification furnace at the same time. The output gas is a high-temperature raw coal gas with a gas temperature of 1450°C to 1600°C, a pressure of 0.6MPa to 1.2MPa, and an oxidation degree of ≤8%.

3. The method for co-producing direct reduced iron based on dry pulverized coal pressurized gasification furnace according to claim 2, characterized in that The desulfurizing agent is one or more of lime powder, limestone powder and dolomite powder.

4. The method for co-producing direct reduced iron based on dry pulverized coal pressurized gasification furnace according to claim 1, characterized in that The raw material iron oxide pellets used to produce direct reduced iron in the DRI reduction shaft furnace are mixed with iron ore lumps of corresponding particle size.

5. The method for co-producing direct reduced iron based on dry pulverized coal pressurized gasification furnace according to claim 1, characterized in that CO2 replaces or partially replaces water vapor as the coal gasification agent in the dry pulverized coal pressurized gasification furnace.

6. The method for co-producing direct reduced iron based on dry pulverized coal pressurized gasification furnace according to claim 5, characterized in that The volume ratio of CO2 to the coal gasification agent shall not exceed 12%.

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