CN117403019A - Method for producing hydrogen directly reduced iron by using molten iron bath coal gasification - Google Patents
Method for producing hydrogen directly reduced iron by using molten iron bath coal gasification Download PDFInfo
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- CN117403019A CN117403019A CN202210791215.4A CN202210791215A CN117403019A CN 117403019 A CN117403019 A CN 117403019A CN 202210791215 A CN202210791215 A CN 202210791215A CN 117403019 A CN117403019 A CN 117403019A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
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- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/0073—Selection or treatment of the reducing gases
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/02—Making spongy iron or liquid steel, by direct processes in shaft furnaces
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Abstract
The invention relates to a method for producing hydrogen by using molten iron bath coal gasification, which is to produce 1-5 kg of molten iron bath coal gas with the oxidation degree less than 30% at 1450-1800 ℃ by using a molten iron bath coal gasifier; spraying coal, coke or semicoke powder for pretreatment to obtain pretreated coal gas with the oxidation degree less than 18% and at 1000-1600 ℃; adding hydrogen gas which is heated to 300-400 ℃ and is converted at normal temperature and removed dust to obtain the DRI reduction shaft furnace reducing gas with the hydrogen-carbon ratio of more than or equal to 1.7 and the oxidation degree of less than 8 percent and 800-900 ℃; the method is used for producing direct reduced iron by reducing iron oxide pellets in a DRI reduction shaft furnace, producing DRI reduction shaft furnace top gas with the temperature of 350-500 ℃ and obtaining H by adopting a conventional CO conversion and gas separation technology 2 The content is more than or equal to 98 percent, and the normal temperature conversion hydrogen with the oxidation degree less than or equal to 3 percent is used for being added into the pretreated coal gas.
Description
Technical Field
The invention belongs to the technical field of direct reduced iron production, relates to a process technology for co-production of molten reduced iron and direct reduced iron, and in particular relates to a method for preparing reducing gas for direct reduced iron production by utilizing high-temperature coal gas of molten reduced iron and top gas conversion hydrogen of direct reduced iron.
Background
Currently, the molten reduced iron and the direct reduced iron are separately manufactured according to separate manufacturing processes.
The COREX-DRI combined flow of south Africa SALDANHA is to cool the COREX gas and purify and remove CO 2 After that, the method is used for producing the direct reduced iron, and the CO conversion H is not implemented on the coal gas 2 The content of CO is higher, and the situation of material adhesion in the direct reduced iron shaft furnace occurs.
CN 104212930a discloses a BAOSHEREX iron-making process for smelting molten iron by a two-step method, the production capacity of the molten reduced molten iron of the iron-making process is fixed, only gas can be regulated, and meanwhile, the dependence on coke and long flow of steel production is not eliminated because coke oven gas is utilized to regulate gas components and coke is used.
CN 111218535a relates to a method for producing direct reduced iron by heating and circulating reducing gas in coal-making of molten iron bath, which utilizes the technologies of CO conversion technology, gas-hydrogen heat exchange technology, cold-hot gas blending technology, different reducing gas component blending technology, different gas component separation technology and the like in the coal chemical technology to furthest utilize the molten iron bath to produce crude gas waste heat, residual gas and residual pressure for smelting direct reduced iron. However, this technique can ensure the (CO) in the gas only when the molten iron is not produced 2 +H 2 O) < 6%, if molten reduced iron is simultaneously produced, the gas (CO) 2 +H 2 O) content is high, up to 31.7%, and cannot be used for the production of direct reduced iron.
CN 1417289a discloses a two-stage dry coal dust gasifier, which has an upper and a lower stage hearth, wherein about 80% of dry coal dust in the lower hearth stage is gasified with oxygen and steam, about 20% of dry coal dust and steam are sprayed into the upper hearth stage, and after pyrolysis and gasification reaction are carried out on the dry coal dust and steam and high-temperature gas generated in the lower hearth stage, the combustible component of the gas can be increased, the heat value is improved, the high-temperature gas is cooled, and the molten ash in the gas is solidified and separated from the gas. The method comprises the steps of spraying coal dust and steam on the upper section of the gasifier, carrying out pyrolysis and partial gasification by utilizing sensible heat in high-temperature gas of the lower section of the gasifier, improving the total cold gas efficiency and increasing the total cold gas efficiencyH in gas 2 The content of the gas is reduced, and the temperature of the gas and the content of the oxidizing gas are reduced. But the lower-stage gas temperature is 1200 ℃, and only the dry distillation pyrolysis of the bituminous coal is involved. Meanwhile, the gas pressure of the gas is 30kg, the gas cannot be directly connected with the existing DRI shaft furnace gas, and the productivity is reduced if the pressure is reduced.
Disclosure of Invention
The invention aims to provide a method for producing hydrogen by using molten iron bath coal gasification to directly reduce iron, which utilizes a molten iron bath coal gasifier to produce molten iron and produces molten iron bath coal gas with pressure for producing the direct reduced iron at the same time, and provides heat and reducing agent for producing the direct reduced iron by a DRI reduction shaft furnace.
In order to achieve the above object, the present invention provides a method for producing hydrogen directly reduced iron by gasification of molten iron bath coal, comprising the following steps.
1) Producing pressurized molten iron bath coal gas by using a molten iron bath coal gasifier:
pulverized coal and oxygen are used as energy sources, iron ore powder is used as iron-making raw materials, and a spray gun is used for conveying gas N according to the iron-carbon ratio of less than or equal to 0.8 2 And/or CO 2 Iron ore powder, coal powder, necessary amount of lime powder and dolomite powder are sprayed into an iron-melting bath coal gasifier, oxygen is sprayed by an oxygen gun, and molten iron bath coal gas with the oxidation degree less than 30 percent and the temperature of 1450-1800 ℃ and the pressure of 1-5 kg is produced while molten iron is produced as a byproduct.
2) Pretreatment of molten iron bath coal gas:
spraying coal, coke or semicoke powder into the molten iron bath coal gas at 1450-1800 ℃ for pretreatment, so that the oxidation degree of the molten iron bath coal gas is reduced to less than 18%, the temperature is reduced to 1000-1600 ℃, and the pretreated coal gas with the pressure of 1-5 kg is obtained.
3) Obtaining a DRI reduction shaft furnace reducing gas:
the normal temperature conversion hydrogen obtained by converting the top gas of the DRI reduction shaft furnace is preheated to 300-400 ℃ by a heat exchanger of the top gas of the DRI reduction shaft furnace and is added into the pretreated coal gas at 1000-1600 ℃ to ensure that the hydrogen-carbon ratio of the pretreated coal gas after mixing is more than or equal to 1.7, the oxidation degree is reduced to less than 8 percent, the temperature is reduced to 800-900 ℃, the pressure is kept at 1-5 kg, and the DRI reduction shaft furnace reducing gas is obtained after dust removal by a dust remover.
4) Direct reduced iron is produced using a DRI reduction shaft furnace:
the DRI reduction shaft furnace reducing gas is sent into the DRI reduction shaft furnace to provide heat and reducing agent for iron oxide pellets in the shaft furnace to produce direct reduced iron, and the DRI reduction shaft furnace top gas with the temperature of 350-500 ℃ and the pressure of 1-5 kg is produced by the top of the reduction shaft furnace.
5) Obtaining normal temperature shift hydrogen through shift of top gas of DRI reduction shaft furnace:
the DRI reduction shaft furnace top gas produced by the DRI reduction shaft furnace top is dedusted and then enters a DRI reduction shaft furnace top gas heat exchanger, is cooled to 170-200 ℃ after heat exchange with normal-temperature conversion hydrogen, is pressurized to a pressure of more than 6kg and a temperature of 190-210 ℃, enters a furnace top gas conversion hydrogen flow, and adopts conventional CO conversion and gas separation technology to obtain H 2 The content is more than or equal to 98 percent, the pressure is 1-5 kg, the oxidation degree is less than or equal to 3 percent, and the normal temperature hydrogen is changed, the temperature is less than 40 ℃, and the hydrogen is used for being added into the pretreated coal gas at 1000-1600 ℃.
Furthermore, in the method for producing the direct reduced iron by the coal gasification of the molten iron bath, less than 3% of O can be sprayed into the reducing gas of the DRI reduction shaft furnace 2 Or by injection of combustible gas CH 4 Or (H) 2 +CO) is combusted, so that the temperature of the reducing gas of the DRI reduction shaft furnace is increased to 850-950 ℃ on the premise that the oxidation degree is less than 8% and the hydrogen-carbon ratio is more than 1.7.
Further, the O can be injected at any position of a pipeline between the outlet of the dust collector and the air inlet of the DRI reduction shaft furnace 2 Or a high temperature gas.
More specifically, the granularity of coal, coke or semicoke powder sprayed into the molten iron bath coal gas in the invention is more than 80% in the part smaller than 0.076 mm.
Still further, the present invention provides another method for producing hydrogen directly reduced iron by gasification of molten iron bath coal, which comprises the following steps.
1) Producing pressurized molten iron bath coal gas by using a molten iron bath coal gasifier:
pulverized coal and oxygen are used as energyIron ore powder is used as iron-making raw material, and the gas N is delivered by a spray gun according to the iron-carbon ratio less than or equal to 0.2 2 And/or CO 2 Iron ore powder, coal powder, necessary amount of lime powder and dolomite powder are sprayed into an iron-melting bath coal gasifier, oxygen is sprayed by an oxygen gun, and molten iron bath coal gas with the oxidation degree less than 20 percent and the temperature of 1450-1800 ℃ and the pressure of 1-5 kg is produced while molten iron is produced as a byproduct.
2) Obtaining a DRI reduction shaft furnace reducing gas:
the normal temperature shift hydrogen obtained by the shift of the top gas of the DRI reduction shaft furnace is preheated to 300-400 ℃ by a heat exchanger of the top gas of the DRI reduction shaft furnace and is added into the molten iron bath coal gas at 1450-1800 ℃ to ensure that the hydrogen-carbon ratio of the mixed molten iron bath coal gas is more than or equal to 1.7, the oxidation degree is reduced to less than 8 percent, the temperature is reduced to 800-900 ℃, the pressure is kept at 1-5 kg, and the DRI reduction shaft furnace reducing gas is obtained after dust removal by a dust remover.
3) Direct reduced iron is produced using a DRI reduction shaft furnace:
the DRI reduction shaft furnace reducing gas is sent into the DRI reduction shaft furnace to provide heat and reducing agent for iron oxide pellets in the shaft furnace to produce direct reduced iron, and the DRI reduction shaft furnace top gas with the temperature of 350-500 ℃ and the pressure of 1-5 kg is produced by the top of the reduction shaft furnace.
4) Obtaining normal temperature shift hydrogen through shift of top gas of DRI reduction shaft furnace:
the DRI reduction shaft furnace top gas produced by the DRI reduction shaft furnace top is dedusted and then enters a DRI reduction shaft furnace top gas heat exchanger, is cooled to 170-200 ℃ after heat exchange with normal-temperature conversion hydrogen, is pressurized to a pressure of more than 6kg and a temperature of 190-210 ℃, enters a furnace top gas conversion hydrogen flow, and adopts conventional CO conversion and gas separation technology to obtain H 2 The content is more than or equal to 98 percent, the pressure is 1-5 kg, the oxidation degree is less than or equal to 3 percent, and the normal temperature hydrogen is changed, and the temperature is less than 40 ℃ and is used for being added into the molten iron bath coal gas at 1450-1800 ℃.
Furthermore, in the method for producing the direct reduced iron by the coal gasification of the molten iron bath, less than 3% of O can be sprayed into the reducing gas of the DRI reduction shaft furnace 2 Or by injection of combustible gas CH 4 Or (H) 2 +CO) post combustionThe high temperature gas of the (2) ensures that the temperature of the reducing gas of the DRI reduction shaft furnace is increased to 850-950 ℃ on the premise that the oxidation degree is less than 8% and the hydrogen-carbon ratio is more than 1.7.
Further, the O can be injected at any position of a pipeline between the outlet of the dust collector and the air inlet of the DRI reduction shaft furnace 2 Or a high temperature gas.
The core technical content of the method for producing the direct reduced iron by using the molten iron bath coal gasification is that the molten iron bath coal gasification furnace is used for producing the pressurized molten iron bath coal gas to smelt the direct reduced iron.
It is known that the gas produced by existing smelting reduction furnaces cannot be used directly for the production of direct reduced iron. For example, the heat value (CO+H) of 1450 ℃ gas produced by the HIsmolt SRV furnace 2 ) 189.1kg of standard coal/t of molten iron, 215kg of standard coal/t of molten iron of gas enthalpy, and up to 404.1kg of standard coal/t of molten iron. But the gas pressure at the upper part of the SRV furnace is 0.8kg, the oxidation degree is as high as 58 percent, and the SRV furnace cannot be in butt joint with a gas-based direct reduced iron shaft furnace.
Therefore, one of the objects of the present invention is to use all of the molten iron bath coal gas produced in the production of molten iron by a molten reduced iron furnace for the production of direct reduced iron, so as to reduce the energy consumption of iron making.
The molten iron bath coal gasifier and the molten reduced iron furnace have the same furnace charge and different proportions, and are realistic conditions for co-producing coal gas and molten iron by using the molten iron bath coal gasifier. However, when the melting reduction furnace is used for producing molten iron at full load, a large amount of CO is inevitably produced 2 The oxidation degree is as high as 58%. The invention reduces the molten iron production load of the molten iron bath coal gasifier, increases the coal injection amount, reduces the gas oxidation degree produced by the molten iron bath coal gasifier to below 30 percent, and further reduces the gas oxidation degree to less than 8 percent by means of further injecting semi-coke powder, adding hydrogen and the like, so that the gas produced by the molten iron bath coal gasifier is completely used for producing direct reduced iron.
The prior iron-making technology is to reduce the energy consumption and improve the iron-carbon ratio, for example, the iron-carbon ratio Fe/C of an iron-making blast furnace is 2.3-2.77, i.e. the more pig iron produced by unit standard coal, the lower the energy consumption. However, the technical scheme of the invention is designed reversely, the iron-carbon ratio of the molten iron-bath coal gasifier is reduced to less than or equal to 0.8, the oxidation degree of the produced molten iron-bath coal gas is controlled to be less than 30%, the temperature is 1450-1800 ℃, and the aim is to produce direct reduced iron by utilizing the molten iron-bath coal gas and reduce the iron-making specific energy consumption.
The iron-carbon ratio is defined as the amount of molten iron produced per unit of standard coal, and is the reciprocal of energy consumption. For example: calculating the iron-carbon ratio according to the energy consumption of the blast furnace pole working procedure: 1000kg Fe.361 kg ce is approximately equal to 2.77tFe/tce, namely, the energy consumption of the blast furnace standard coal is ton to produce 2.77 tons of molten iron.
If the iron-carbon ratio of the gas produced by the molten iron bath coal gasifier is 0.4tFe/tce, the standard coal converted into the input is 1 tce/0.4 tFe/tce =2.5 tce/tFe, namely, 1 ton of molten iron is produced by inputting 2.5 tons of standard coal, and the energy consumption of the blast furnace marker post is 6.9 times of that of 0.361tce/tFe (carbon-iron ratio).
Therefore, the yield of the molten reduced iron is compared with the yield of the direct reduced iron, the yield of the molten reduced iron is not more than 20 percent, and the yield of the direct reduced iron is more than or equal to 80 percent. Obviously, 2.5 tons of coal is mainly produced gas for the subsequent production of direct reduced iron, molten iron produced by the molten iron bath coal gasifier is a byproduct, and direct reduced iron produced by the DRI reduction shaft furnace is the main product.
The oxygen-enriched HIsmelt SRV furnace can be directly utilized to be transformed into an oxygen-melting iron-bath coal gasifier. The pressure of the gas at the upper part of the HIsmolt SRV furnace is only 0.8kg, the tap hole and the slag hole are modified, a blast furnace gun is used for sealing, molten iron is discharged and slag is discharged in a blast furnace mode, the pressure of the gas at the upper part of the furnace body can be increased to 1.5-5 kg, and the gas can be in butt joint with the pressure of 1.5-5 kg of the gas entering the furnace of various reduction shaft furnaces including MIDREX, CSDRI, CTR, WTY-DRI and the like.
The oxygen molten iron bath coal gasifier mainly produces coal gas and simultaneously produces molten iron. The production of molten iron takes the addition of blown iron ore powder as a main measure, and simultaneously increases the amounts of blown coal powder, oxygen, lime powder and dolomite powder.
The molten iron consumption index per ton is as follows: the grade of the iron ore is 60-67%, the ore-iron ratio is 1.5-1.6, the pulverized coal is 0.7-0.78 t, and the oxygen is 600-700 m 3 Dolomite 0.1t, lime 0.11t, slag to iron ratio 400kg. Oxygen consumption of coal gas 580m 3 Tce the method comprises blowing lime powder with coal gasDesulfurizing, and adjusting the amount of lime powder to be sprayed according to the sulfur content of the coal and the iron ore powder.
According to experimental results, when the molten iron bath coal gasifier only produces molten iron bath coal gas and does not produce molten iron, the spray gun is used for using N for iron ore powder, coal powder, lime powder and dolomite powder 2 Or CO 2 The oxygen is independently sprayed into the molten iron bath coal gasifier under the slag layer as a conveying gas, and when the temperature of the produced gas is 1450 ℃, the immersed blowing can realize the oxidation gas (CO) in the gas 2 +H 2 O) content is less than 1.5; if sprayed onto the slag layer, the oxidizing gas content in the gas is < 6%. The oxidation degree of the coal gas can be adjusted by adjusting the iron-carbon ratio, spraying semi-coke powder, adding hydrogen and the like, so that the coal gas can be sprayed upwards or downwards.
When the molten iron bath coal gasifier produces molten iron bath coal gas and simultaneously produces molten iron, the amount of the blown iron ore powder can be controlled, and the CO can be controlled while controlling the yield of the molten iron 2 The content is as follows. Under the condition of a certain amount of coal injection and oxygen injection, the amount of iron ore powder injection is increased, the yield of molten iron is improved, and the CO in the coal gas is increased 2 The content is also increased; conversely, the amount of the blown iron ore powder is reduced, the molten iron yield is reduced, and CO in the coal gas is reduced 2 The content is reduced. The oxidation degree of the coal gas is controlled to be less than 30 percent.
The oxygen-enriched HIsmolt SRV furnace is changed into an oxygen-enriched iron bath coal gasifier, and under the conditions of producing coal gas and co-producing molten iron, the molten iron yield is unchanged, and the oxygen injection amount is unchanged, because the N brought by the oxygen-enriched gas is not available 2 N in original oxygen enrichment 2 The carried sensible heat (enthalpy) is transferred to the coal gas, which can raise the temperature of the coal gas to 1450-1800 ℃.
Furthermore, the present invention can also be used to prepare dry powder from various iron-containing solid wastes including, but not limited to, steel slag, desulphurized steel slag, alumina red mud, sulfuric acid slag, etc., and spray gun N 2 Or CO 2 As a conveying gas, the molten iron is sprayed under a slag layer in the molten iron bath coal gasifier to replace part of iron concentrate powder, lime powder and dolomite powder, and iron-containing minerals are reduced and melted into molten iron in a high-temperature smelting reduction atmosphere.
In the process of producing molten iron bath coal gas by utilizing the molten iron bath coal gasifier, the technical parameters including iron ore powder, coal dust, lime, dolomite and the like can be adjusted, and particularly the oxygen injection amount and the coal injection amount can be adjusted by increasing or decreasing, so that the temperature of the molten iron bath coal gas, the temperature of molten iron and the oxidation gas (CO) in the coal gas can be adjusted 2 +H 2 O) and a reducing gas (H) 2 +co) content, and the like.
When the invention utilizes the molten iron bath coal gasifier to produce molten iron bath coal gas, coal dust can be used as a main energy source, and partial biomass and/or organic polymer industrial waste materials including but not limited to waste plastics, waste tires, urban organic garbage and the like can be added as secondary energy sources.
The second purpose of the invention is to use CO and N 2 Or CO 2 The gas or the mixed gas of the (a) is taken as a conveying gas, coal, coke or semicoke powder is input into a gas chamber or a pipeline of a molten iron bath coal gasifier with the temperature of 1450-1800 ℃ by a spray gun, and an oxidizing gas (CO) is generated by utilizing sensible heat in the high Wen Rongtie bath coal gas by adopting a carbon melting reaction 2 +H 2 O) to a reducing gas (H) 2 +co) to reduce the temperature and oxidation degree of the molten iron bath coal gas.
In the invention, any one of semi-coke powder, coal powder or coke powder with granularity less than 0.076mm and more than 80% is sprayed into a gas chamber or a pipeline of a molten iron bath coal gasifier at 1450-1800 ℃, the specific surface area of the semi-coke powder is thousands times of that of blast furnace coke, and the semi-coke powder is sprayed into the high-temperature molten iron bath coal gas to contain CO 2 、H 2 Under the condition of O and under the condition that the dust of the coal gas contains iron ore dust, carbon fusion reaction (C+CO) can instantaneously occur 2 =2CO ΔH=172.5 kj) and (c+h) 2 O=H 2 +CO ΔH=122.67kj）。
Wherein 1000 gC/12 mol×172.5 kj=14375 kj, i.e. 12gC with 44g CO 2 The reaction takes place by absorbing 172.5kj heat, 1000gC and CO 2 The reaction absorbs 14375kj of heat.
The half coke powder can be blown to reduce the temperature of the coal gas from 1450-1800 ℃ to 1000-1600 ℃ and oxidize the coal gasThe degree is reduced to less than 18 percent, and simultaneously, 90 percent of semi-coke powder and (CO in the gas 2 +H 2 O) is subjected to carbon-melting reaction to obtain (CO) in the gas 2 +H 2 O) conversion to (CO+H) 2 ) The oxidizing gas is reduced and the reducing gas is increased. After the coal gas enters the dust remover, a small amount of residual carbon and dust contained in the coal gas can be removed from the coal gas together.
The third object of the present invention is to obtain reducing gas for a DRI reduction shaft furnace.
After the temperature of the coal gas is reduced to 1000-1600 ℃ and the oxidation degree is reduced to less than 18%, the quality of the coal gas can not meet the quality requirements of the DRI reduction shaft furnace reducing gas such as the temperature, the oxidation degree, the hydrogen-carbon ratio and the like, meanwhile, in order to increase the circulating reduction gas quantity to increase the DRI yield, the top gas of the DRI reduction shaft furnace is converted into hydrogen to be added into the pretreated coal gas at 1000-1600 ℃, and the pretreated coal gas is added into the pretreated coal gas at 850 ℃, the oxidation degree is less than 8%, and the hydrogen-carbon ratio is more than 1.7, so that the quality requirements of the reducing gas for the DRI reduction shaft furnace are met.
H in reducing gas for DRI reduction shaft furnace 2 First, a small amount of H contained in the coal gas from the molten iron bath 2 Secondly, the top of the DRI reduction shaft furnace can produce DRI reduction shaft furnace top gas with the temperature of 350-500 ℃ and the pressure of 1-5 kg, wherein the top gas contains (CO+H) 2 O) adopts CO conversion H in coal chemical industry 2 Techniques, CO+H 2 O=H 2 +CO 2 Can be transformed and separated to obtain H 2 The normal temperature conversion hydrogen with the content of more than or equal to 98 percent, the oxidation degree of less than or equal to 3 percent and the pressure of 1 to 5kg is used for being added into the pretreated coal gas to obtain the reducing gas of the DRI reduction shaft furnace and is used for being introduced into the direct reduction iron shaft furnace to provide heat and reducing agent to produce the direct reduction iron.
The water vapor required by the shift reaction can be obtained from the cooling heat exchange process of the top gas heat exchanger and the shift gas heat exchanger of the DRI reduction shaft furnace, and can also be obtained from the cooling gas heat exchanger of the cooling section of the DRI reduction shaft furnace, and the water vapor recovered in the process can meet the requirement of the shift reaction.
Further, coal, coke or semicoke powder is not blown into the gas produced by the molten iron bath coal, and the molten iron bath coal gas is addedThe coal powder is sprayed into the melting furnace to increase the gas production amount, or the iron-carbon ratio is reduced from less than or equal to 0.8 to less than or equal to 0.2, the oxidation degree of the molten iron bath coal gas is reduced to less than 20 percent, the temperature is less than 1700 ℃, and then hydrogen is added into the molten iron bath coal gas, so that the quality of the reducing gas of the obtained DRI reduction shaft furnace can also meet the requirement of the DRI reduction shaft furnace on the quality of the reducing gas. The iron-to-carbon ratio is reduced, and the available (CO 2 +H 2 O) is reduced, coal injection, coke injection or semicoke powder injection is also reduced, but the coal injection amount of gas produced by the molten iron bath is increased, the DRI yield is increased, so that the energy consumption of semi-coke powder injection is close to that of non-semi-coke powder injection, the energy consumption of semi-coke powder injection is slightly low, the energy consumption of non-semi-coke powder injection is slightly high, and the molten iron yield is relatively reduced due to the reduction of the iron-carbon ratio of the non-semi-coke powder injection.
The pressure of the reducing gas needed by the direct reduction shaft furnace is 1-5 kg, and the pressure is equal to the pressure of the coal gas of the molten iron bath coal gasifier, so the invention can connect the coal gas of the two furnaces through a pipeline, and the component and the quality of the coal gas generated by the molten iron bath coal gasifier can be continuously and uninterruptedly adjusted through molten iron reduction output, semi-coke powder injection, hydrogen addition and the like, and then the reducing gas for the DRI reduction shaft furnace is prepared and supplied to the DRI reduction shaft furnace.
Furthermore, CO can be collected and recovered by Pressure Swing Adsorption (PSA) separation for the shift gas after the shift gas of the top gas is shifted into hydrogen 2 And then to CO 2 The utilization or sealing (CCUS) is implemented, so that zero carbon emission and even negative carbon emission of smelting DRI can be realized.
After the normal temperature shift hydrogen is added into the pretreated coal gas, the temperature of the obtained DRI reduction shaft furnace reducing gas should be kept between 800 and 900 ℃. When the temperature is not reached, the temperature of the reducing gas fed into the direct reduction shaft furnace can be increased by separating part of hydrogen and reducing the amount of the hydrogen to be added. Conversely, the temperature of the reducing gas fed into the direct reduction shaft furnace can be reduced by increasing the blending amount of hydrogen.
Of course, further, by reducing the quantity of the half coke powder, the coke powder and the coal powder, the molten iron yield and the molten iron bath coal gas yield are changed, and the reducing gas of the DRI reduction shaft furnace can reach the quality required by being fed into the direct reduction shaft furnace on the premise of not separating hydrogen.
Furthermore, when the DRI reduction shaft furnace reducing gas obtained does not reach the temperature, a partial oxidation method can be adopted to lead the O to be less than 3 percent 2 Spraying the gas into any position of a pipeline between the outlet of the dust remover and the gas inlet of the DRI reduction shaft furnace, so that the temperature of the reduction gas of the DRI reduction shaft furnace is increased to 850-950 ℃ on the premise that the oxidation degree is ensured to be less than 8% and the hydrogen-carbon ratio is more than 1.7; meanwhile, other high-temperature fuel gas such as natural gas, coke oven gas, hydrogen, coal gas high-temperature gas or burnt high-temperature gas can be added into the reducing gas, the oxidation degree of the reducing gas is reduced to less than 8%, and the temperature is increased to 850-950 ℃ under the premise that the hydrogen-carbon ratio is greater than 1.7.
The DRI reduction shaft furnace adopts a conventional gas-based method to directly reduce iron shaft furnaces, including but not limited to MIDREX, CTR, HYL-III, CSDRI and other reduction shaft furnaces.
Compared with the prior art, the method for producing the direct reduced iron by using the molten iron bath coal gasification has the advantages that the following aspects are mainly realized.
1. The production process is short. Compared with the blast furnace iron-making process, the two iron-making processes of coking and sintering are completely eliminated, and the iron-making production process is shortened.
2. The energy consumption is low. The energy consumption standard level of the blast furnace ironmaking process is 435kgce/t molten iron, the specific energy consumption standard level of the coking and sintering is 552kgce/t molten iron, while the specific energy consumption of the embodiment 1 of the invention is 467.8kgce/t molten iron, the specific energy consumption standard level of the blast furnace is 84kgce/t lower than that of the blast furnace, and the specific energy consumption standard level of the blast furnace is equal to that of the blast furnace specific energy consumption standard rod.
3. And (5) recycling the oxidizing gas. The water vapor in the top gas of the DRI reduction shaft furnace is pressurized by a compressor at the temperature of 100-200 ℃ and enters CO conversion H 2 The process comprises the steps of converting hydrogen under the conditions of catalyst and low-temperature conversion, sending the hydrogen into a DRI reduction shaft furnace through a top gas heat exchanger, and forming water vapor in the top gas of the DRI reduction shaft furnace after reducing iron, thereby realizing the recycling of water vapor-hydrogen. Spraying pulverized coal, coke powder and semicoke powder into 1450-1800 ℃ molten iron bath coal gas to generate carbon melting reaction, (CO) 2 +H 2 O) transitionIs (CO+H) 2 ) Also realize part (CO 2 +H 2 O) recycling.
4. And (5) solid waste treatment. A great amount of CaO, mgO, feO, fe contained in the steel slag and alumina red mud dry powder 2 O 3 Is an iron raw material and a desulfurizing agent required by molten iron bath coal gasification, and can not only purify the environment but also obtain additional economic compensation by treating solid waste.
5. Zero carbon row and negative carbon row. Not only has low energy consumption and low emission; the coking and sintering processes with the heaviest pollution are also eliminated; the key point is that CO can be separated and recovered from DRI top gas shift gas 2 In the implementation of CCUS with CO sequestration 2 Can realize zero emission under the condition of (1); under the condition of using biomass, waste plastics and waste rubber as energy sources, the negative carbon emission can be realized.
6. The energy cost is low. The prior blast furnace ironmaking energy cost is high because the price of coking coal and coke is higher than that of bituminous coal and anthracite. The coal gas can be made of bituminous coal, anthracite coal and lignite after drying and dehydration, and the cost is lower than that of a blast furnace; the invention can also utilize industrial waste organic matters and urban organic garbage as energy sources, and can obtain extra economic compensation, thereby further reducing the energy cost.
7. The production equipment has high efficiency. Taking a molten iron bath coal gasifier with the diameter of 6m as an example, the annual yield can reach 273.4 ten thousand tons (DRI+molten iron)/a, which is equivalent to 3300m 3 Annual production of blast furnace.
8. The direct reduced iron produced by the coal gasification of the molten iron bath can replace part of blast furnace ironmaking.
Detailed Description
The following describes the present invention in further detail with reference to examples. The following examples are presented only to more clearly illustrate the technical aspects of the present invention so that those skilled in the art can better understand and utilize the present invention without limiting the scope of the present invention.
The experimental methods, production processes, instruments and equipment related to the embodiments of the present invention have names and abbreviations that are common names in the steel and chemical industries in the field, and are well-known and defined in the related application fields, and those skilled in the art can understand the conventional process steps and apply corresponding equipment according to the names, and implement the methods according to conventional conditions or conditions suggested by manufacturers.
The various materials used in the examples of the present invention are not particularly limited in source, and are all conventional products commercially available or can be prepared according to conventional methods well known to those skilled in the art.
Example 1.
The oxygen-enriched HIsmelt SRV furnace was used and changed to a pure oxygen molten iron bath coal gasifier in the following manner.
Plugging the tapping hole and the slag hole by using a blast furnace gun, tapping and slag discharging in a blast furnace mode, and increasing the pressure of coal gas from 0.8kg to 1.5-4 kg; the HIsmolt SRV furnace is changed into a gas furnace which mainly produces molten iron and produces crude gas as a byproduct into a gas furnace which mainly produces high-temperature gas, and can be used for directly reducing iron to be used as reducing gas and producing a small amount of molten iron as a byproduct.
The molten iron bath coal gasifier can produce 50t/h of molten iron; coal for coal gas is 65t/h, and the production of 1750 ℃ molten iron bath coal gas 197300m 3 And/h, the oxidation degree of the gas produced by the molten iron bath coal is 20.12%, the iron-carbon ratio of the product is 0.5, and the numerical values of specific technical and economic indexes are shown in tables 1-2.
In Table 1450 ℃ enthalpy kj/h, the oxygen-enriched-free HIsmolt SRV furnace changed pure oxygen to pure oxygen without N in the oxygen enrichment 2 Original N 2 The heat "enthalpy" carried is transferred to the enthalpy in the gas. Adding the part N 2 After transferring enthalpy, the temperature of the coal gas is 1750 ℃.
Then, semi-coke powder is sprayed into a high-temperature gas chamber and a high-temperature gas pipeline of the molten iron bath coal gasifier, and the spraying amount of the semi-coke powder is 51g/m 3 (in standard state), 10t/h, and specific technical indexes are shown in Table 3.
After semicoke injection is calculated, the temperature of the coal gas is 1398-1400 ℃.
Dedusting furnace top gas produced by a DRI shaft furnace at 400 ℃ and under the pressure of 3kg, feeding the furnace top gas into a heat exchanger, exchanging heat with normal-temperature converted hydrogen, cooling to 190 ℃, pressurizing to 9kg again, heating to 200 ℃, and entering a furnace top gas hydrogen conversion flow path, wherein conventional CO is adopted to convert H 2 Gas separation technique to obtain H 2 The content is more than or equal to 96 percent, the pressure is 3kg, and the hydrogen is converted at the normal temperature of 25 ℃; the normal temperature converted hydrogen enters a heat exchanger, exchanges heat with furnace top gas and heats to 350 ℃, then is added into the obtained pretreated coal gas with 1400 ℃ and 3kg pressure to obtain DRI furnace circulating reducing gas with the hydrogen-carbon ratio of 2.22 and the temperature of 850 ℃ and the oxidation degree of 4.88%, and is introduced into a DRI shaft furnace to provide heat and reducing agent to produce DRI, and the furnace top gas with the pressure of 3kg and the temperature of 400 ℃ is produced from the furnace top; the above process is cyclically performed.
After the converted hydrogen is added, various technical indexes of the gas fed into the DRI shaft furnace reach the quality indexes of the reducing gas required by the MIDREX shaft furnace.
Annual yield of this example: 240 ten thousand DRI, 38.4 ten thousand tons of molten iron, slag and N 2 、CO 2 . The energy consumption of the blast furnace is lower than the standard level of 552kgce/t molten iron by being folded into the molten iron with the specific energy consumption of 468.3kgce/t molten iron83.7kgce/t. molten iron, which is substantially level with the level of the standard level 467.8kgce/t molten iron, which is comparable to the energy consumption of the blast furnace.
Example 2.
And co-producing DRI by adopting high-temperature raw gas of a molten iron bath coal gasifier. Example 2 compared with example 1, the step 2 of spraying semicoke powder was omitted, the iron-carbon ratio was 0.18, and the design parameters and the implementation results are shown in tables 7 to 11.
Molten iron production 50t/h, coal production 100t/h, and crude gas production 270100m 3 And/h, the oxidation degree of the crude gas is 18%. The temperature was 1700 ℃.
Note that: pure oxygen free HIsmelt N in total enthalpy 2 Transfer enthalpy. Adding oxygen-enriched pure oxygen N 2 After transferring enthalpy, the temperature of the coal gas is 1700 ℃.
Calculated temperature after hydrogen addition: 877 ℃.
The molten iron bath coal gasification gas is subjected to the molten iron gas co-production in step 1, the step 2 is not implemented, the step 1 raw gas is connected with the step 3 to convert hydrogen, the gas components can meet the technical parameter requirements of DRI on gas quality, temperature, oxidation degree, hydrogen-carbon ratio and the like, and the molten iron bath coal gasification co-production of DRI can be realized.
Maximum annual output of this example: DRI 271.9 ten thousand t, molten iron 15.4 ten thousand ton, water slag and N 2 、CO 2 . The specific energy consumption of the molten iron is 483.76kgce/t molten iron, and the specific energy consumption of the molten iron is 68kgce/t molten iron lower than the reference level of 552kgce/t molten iron of the blast furnace. The 2 nd step is not implemented, so that the gas yield of the gas is increased, and the iron-carbon ratio is reduced.
The calculated gas amounts in the above examples 1 and 2 are all standard state 0 ℃; the gas components (%) are all gases (%).
The above-described embodiments of the present invention are based on the following reasons.
1) Sensible heat and CO of raw coal gas of molten iron bath coal gasification 2 The carbon-melting reaction of the sprayed semicoke powder utilizes a part of the carbon-melting reaction, and the semicoke powder CO is sprayed 2 DRI increased by conversion to CO as a reducing agent, example 1 up to 45.31 ten thousand DRI/a, using once CO 2 The energy consumption is reduced.
2) Another part of sensible heat of the raw coal gas of the molten iron bath coal gasification is utilized by directly reducing iron, wherein coal gas generated by each ton of molten iron is transferred to 404.1kg of standard coal per t of molten iron (calorific value+sensible heat), 38.4 ten thousand tons per ton of molten iron (calorific value+sensible heat) is utilized in the embodiment 1, and 15.517 ten thousand tons per ton of energy is saved.
3) Oxygen energy consumption is used for pressure swing adsorption separation of oxygen in air according to the Hao technology (Yuan southwest chemical industry institute), and the oxygen energy consumption is calculated by electricity consumption, so that the oxygen production energy consumption is reduced.
4) The converted hydrogen is preheated to 350 ℃ by a DRI top gas heat exchanger and is added into high-temperature gas, thereby utilizing the sensible heat of the DRI top gas, particularly reducing the oxidation degree of the gas, improving the hydrogen-carbon ratio, increasing the reducing gas flow entering the DRI shaft furnace and increasing the DRI yield.
5) The hydrogen is reduced to iron ore to produce steam (Fe 2 O 3 +3H 2 =2Fe+3H 2 O); conversion to hydrogen (H) in a gas converter 2 O+CO=CO 2 +H 2 ) Hydrogen, water vapor and hydrogen recycling, and the water vapor deficiency part supplements the water vapor recovered by the DRI top gas heat exchanger and the converter heat exchanger. The waste heat in the flow is utilized to supplement and produce the water vapor, which can basicallyWater vapor to meet the hydrogen shift requirement.
The above embodiments of the invention are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Various changes, modifications, substitutions and alterations may be made by those skilled in the art without departing from the principles and spirit of the invention, and it is intended that the invention encompass all such changes, modifications and alterations as fall within the scope of the invention.
Claims (8)
1. A method for producing hydrogen directly reduced iron by using molten iron bath coal gasification, comprising the following steps:
1) Producing pressurized molten iron bath coal gas by using a molten iron bath coal gasifier:
pulverized coal and oxygen are used as energy sources, iron ore powder is used as iron-making raw materials, and a spray gun is used for conveying gas N according to the iron-carbon ratio of less than or equal to 0.8 2 And/or CO 2 Spraying iron ore powder, coal powder, necessary amount of lime powder and dolomite powder into an iron-melting bath coal gasifier, spraying oxygen by an oxygen lance, and producing iron-melting bath coal gas with the oxidation degree less than 30% and the temperature of 1450-1800 ℃ and the pressure of 1-5 kg while producing molten iron as a byproduct;
2) Pretreatment of molten iron bath coal gas:
spraying coal, coke or semicoke powder into the molten iron bath coal gas at 1450-1800 ℃ for pretreatment, so that the oxidation degree of the molten iron bath coal gas is reduced to less than 18%, the temperature is reduced to 1000-1600 ℃, and the pretreated coal gas with the pressure of 1-5 kg is obtained;
3) Obtaining a DRI reduction shaft furnace reducing gas:
preheating normal-temperature conversion hydrogen obtained by converting top gas of a DRI reduction shaft furnace to 300-400 ℃ through a heat exchanger of the top gas of the DRI reduction shaft furnace, adding the normal-temperature conversion hydrogen into the 1000-1600 ℃ pretreatment coal gas, reducing the oxidation degree to less than 8% and the temperature to 800-900 ℃ and keeping the pressure at 1-5 kg, and dedusting through a deduster to obtain the DRI reduction shaft furnace reduction gas;
4) Direct reduced iron is produced using a DRI reduction shaft furnace:
the DRI reduction shaft furnace reducing gas is sent into the DRI reduction shaft furnace, heat and reducing agent are provided for iron oxide pellets in the shaft furnace to produce direct reduced iron, and the top gas of the DRI reduction shaft furnace with the temperature of 350-500 ℃ and the pressure of 1-5 kg is produced from the top of the reduction shaft furnace;
5) Obtaining normal temperature shift hydrogen through shift of top gas of DRI reduction shaft furnace:
the DRI reduction shaft furnace top gas produced by the DRI reduction shaft furnace top is dedusted and then enters a DRI reduction shaft furnace top gas heat exchanger, is cooled to 170-200 ℃ after heat exchange with normal-temperature conversion hydrogen, is pressurized to a pressure of more than 6kg and a temperature of 190-210 ℃, enters a furnace top gas conversion hydrogen flow, and adopts conventional CO conversion and gas separation technology to obtain H 2 The content is more than or equal to 98 percent, the pressure is 1-5 kg, the oxidation degree is less than or equal to 3 percent, and the normal temperature hydrogen is changed, the temperature is less than 40 ℃, and the hydrogen is used for being added into the pretreated coal gas at 1000-1600 ℃.
2. A method for producing hydrogen directly reduced iron by using molten iron bath coal gasification, comprising the following steps:
1) Producing pressurized molten iron bath coal gas by using a molten iron bath coal gasifier:
pulverized coal and oxygen are used as energy sources, iron ore powder is used as iron-making raw materials, and a spray gun is used for conveying gas N according to the iron-carbon ratio of less than or equal to 0.2 2 And/or CO 2 Spraying iron ore powder, coal powder, necessary amount of lime powder and dolomite powder into an iron-melting bath coal gasifier, spraying oxygen by an oxygen lance, and producing iron-melting bath coal gas with the oxidation degree less than 20% and the temperature of 1450-1800 ℃ and the pressure of 1-5 kg while producing molten iron as a byproduct;
2) Obtaining a DRI reduction shaft furnace reducing gas:
preheating normal-temperature conversion hydrogen obtained by converting top gas of a DRI reduction shaft furnace to 300-400 ℃ through a heat exchanger of the top gas of the DRI reduction shaft furnace, adding the preheated normal-temperature conversion hydrogen into the molten iron bath coal gas at 1450-1800 ℃ to ensure that the hydrogen-carbon ratio of the mixed molten iron bath coal gas is more than or equal to 1.7, reducing the oxidation degree to less than 8%, reducing the temperature to 800-900 ℃ and keeping the pressure at 1-5 kg, and dedusting the mixed molten iron bath coal gas through a deduster to obtain the DRI reduction shaft furnace reducing gas;
3) Direct reduced iron is produced using a DRI reduction shaft furnace:
the DRI reduction shaft furnace reducing gas is sent into the DRI reduction shaft furnace, heat and reducing agent are provided for iron oxide pellets in the shaft furnace to produce direct reduced iron, and the top gas of the DRI reduction shaft furnace with the temperature of 350-500 ℃ and the pressure of 1-5 kg is produced from the top of the reduction shaft furnace;
4) Obtaining normal temperature shift hydrogen through shift of top gas of DRI reduction shaft furnace:
the DRI reduction shaft furnace top gas produced by the DRI reduction shaft furnace top is dedusted and then enters a DRI reduction shaft furnace top gas heat exchanger, is cooled to 170-200 ℃ after heat exchange with normal-temperature conversion hydrogen, is pressurized to a pressure of more than 6kg and a temperature of 190-210 ℃, enters a furnace top gas conversion hydrogen flow, and adopts conventional CO conversion and gas separation technology to obtain H 2 The content is more than or equal to 98 percent, the pressure is 1-5 kg, the oxidation degree is less than or equal to 3 percent, and the normal temperature hydrogen is changed, and the temperature is less than 40 ℃ and is used for being added into the molten iron bath coal gas at 1450-1800 ℃.
3. The method for producing hydrogen directly reduced iron by coal gasification in molten iron bath according to claim 1 or 2, characterized in that less than 3% of O can be injected into the reducing gas of the DRI reduction shaft furnace 2 Or by injection of combustible gas CH 4 Or (H) 2 +CO) is combusted, so that the temperature of the reducing gas of the DRI reduction shaft furnace is increased to 850-950 ℃ on the premise that the oxidation degree is less than 8% and the hydrogen-carbon ratio is more than 1.7.
4. The method for producing hydrogen directly reduced iron by coal gasification in molten iron bath according to claim 3, characterized in that said O can be injected at any position of the pipe between the outlet of the dust collector and the air inlet of the DRI reduction shaft furnace 2 Or a high temperature gas.
5. The method for producing direct reduced iron by coal gasification in molten iron bath according to claim 1 or 2, wherein coal dust is used as a main energy source and biomass and/or organic polymer industrial waste is added as a secondary energy source when producing molten iron bath coal gas by using a molten iron bath gasifier.
6. The method for producing hydrogen directly reduced iron by coal gasification in molten iron bath according to claim 1, wherein the particle size of coal, coke or semicoke powder sprayed into the molten iron bath coal gas is more than 80% in the portion smaller than 0.076 mm.
7. The method for producing hydrogen directly reduced iron by using molten iron bath coal gasification according to claim 1 or 2, wherein steel slag powder is sprayed into the molten iron bath coal gasification furnace to replace part of iron ore powder, lime powder and dolomite powder.
8. The method for producing hydrogen directly reduced iron by using molten iron bath coal gasification according to claim 1 or 2, wherein alumina red mud powder is sprayed into the molten iron bath coal gasification furnace to replace part of iron ore powder, lime powder and dolomite powder.
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