CN107354258B - System and method for producing direct reduced iron by steam reforming of BGL gasification gas - Google Patents
System and method for producing direct reduced iron by steam reforming of BGL gasification gas Download PDFInfo
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 94
- 238000002309 gasification Methods 0.000 title claims abstract description 87
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 40
- 238000000629 steam reforming Methods 0.000 title claims abstract description 28
- 238000006243 chemical reaction Methods 0.000 claims abstract description 129
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 77
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 61
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 61
- 239000003245 coal Substances 0.000 claims abstract description 56
- 239000003034 coal gas Substances 0.000 claims abstract description 40
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 40
- 238000005406 washing Methods 0.000 claims abstract description 40
- 230000023556 desulfurization Effects 0.000 claims abstract description 39
- 238000005262 decarbonization Methods 0.000 claims abstract description 35
- 239000000428 dust Substances 0.000 claims abstract description 30
- 239000008188 pellet Substances 0.000 claims abstract description 15
- 239000000463 material Substances 0.000 claims abstract description 7
- 239000007789 gas Substances 0.000 claims description 356
- 238000006722 reduction reaction Methods 0.000 claims description 66
- 238000000034 method Methods 0.000 claims description 56
- 229910052799 carbon Inorganic materials 0.000 claims description 51
- 229910052717 sulfur Inorganic materials 0.000 claims description 39
- 239000011593 sulfur Substances 0.000 claims description 39
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 38
- 238000002485 combustion reaction Methods 0.000 claims description 25
- 230000001105 regulatory effect Effects 0.000 claims description 25
- 239000003546 flue gas Substances 0.000 claims description 24
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 23
- 239000000446 fuel Substances 0.000 claims description 20
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 15
- 239000003054 catalyst Substances 0.000 claims description 15
- 239000001301 oxygen Substances 0.000 claims description 15
- 229910052760 oxygen Inorganic materials 0.000 claims description 15
- 239000002918 waste heat Substances 0.000 claims description 14
- 238000010438 heat treatment Methods 0.000 claims description 13
- 239000002994 raw material Substances 0.000 claims description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 11
- 230000006835 compression Effects 0.000 claims description 11
- 238000007906 compression Methods 0.000 claims description 11
- 238000012545 processing Methods 0.000 claims description 11
- 238000011084 recovery Methods 0.000 claims description 11
- 229910052739 hydrogen Inorganic materials 0.000 claims description 5
- 238000002347 injection Methods 0.000 claims description 5
- 239000007924 injection Substances 0.000 claims description 5
- 230000003009 desulfurizing effect Effects 0.000 claims 2
- 238000005516 engineering process Methods 0.000 abstract description 36
- 229910052742 iron Inorganic materials 0.000 abstract description 15
- 238000000746 purification Methods 0.000 abstract description 6
- 238000002407 reforming Methods 0.000 abstract description 5
- 230000010354 integration Effects 0.000 abstract description 2
- 239000003077 lignite Substances 0.000 description 22
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 16
- 239000000203 mixture Substances 0.000 description 11
- 239000003345 natural gas Substances 0.000 description 8
- 230000009286 beneficial effect Effects 0.000 description 4
- 238000004939 coking Methods 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- 239000004480 active ingredient Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000007323 disproportionation reaction Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000010079 rubber tapping Methods 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 238000010793 Steam injection (oil industry) Methods 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- PPBAJDRXASKAGH-UHFFFAOYSA-N azane;urea Chemical compound N.NC(N)=O PPBAJDRXASKAGH-UHFFFAOYSA-N 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000005201 scrubbing Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 238000005200 wet scrubbing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/0073—Selection or treatment of the reducing gases
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/10—Reduction of greenhouse gas [GHG] emissions
- Y02P10/143—Reduction of greenhouse gas [GHG] emissions of methane [CH4]
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Industrial Gases (AREA)
Abstract
The invention provides a system and a method for producing direct reduced iron by steam reforming of BGL gasification gas, wherein the system comprises a BGL gasification unit, a dust removal washing unit, a water-gas shift unit, a desulfurization and decarbonization unit, a reforming unit and a gas-based reduction unit which are connected in sequence. In the invention, coal gas generated by a BGL gasification furnace is subjected to water-gas shift, desulfurization and decarbonization and conversion in a conversion furnace to obtain high-temperature and high-reduction-degree synthesis gas, and the synthesis gas is introduced into a gas-based reduction shaft furnace to reduce pellets to obtain reduced metallic iron. The invention can realize the effective integration of coal gasification technology, gas conversion technology, gas purification technology and reduction shaft furnace technology by combining the fixed bed pressurized gasification furnace with the water gas conversion unit, the conversion unit and the gas-based reduction shaft furnace, and provides a system and a method for producing direct reduced iron by using coal gas with higher material and energy utilization rate.
Description
Technical Field
The invention belongs to the technical field of direct reduced iron production, relates to a system and a method for producing direct reduced iron by steam reforming of BGL gasification gas, and particularly relates to a system and a method for producing direct reduced iron by combining coal gas produced by a BGL gasification furnace with a HyL-III gas-based reduction shaft furnace.
Background
Direct Reduced Iron (DRI) refers to a process of reducing iron ore to sponge iron below the melting temperature. Compared with the traditional blast furnace ironmaking method, the method omits procedures such as coking, sintering and the like, and has the advantages of short flow, small pollution, low consumption, no influence of shortage of high-quality coking coal and the like; meanwhile, the direct reduced iron has low content of sulfur, phosphorus, silicon and other harmful impurities, and is beneficial to smelting high-quality pure steel in an electric furnace.
Since the study of gas-based shaft furnace technology began in 1936 Midrex technology, the development of direct reduced iron technology has been over 80 years old. The direct reduced iron processes commercialized abroad are Midrex, hyL, PERED, etc. The foreign direct reduced iron production mainly uses pellets prepared from natural gas and iron concentrate as raw materials, and the direct reduced iron is mainly produced by reducing iron ore in a shaft furnace based on the natural gas direct reduced iron technology.
China is a country with deficient natural gas resources, and from the perspective of predictive analysis of the yield and consumption of the natural gas in the middle and future, the natural gas is used as the main raw material of the gas-based direct reduced iron process gas, so that the method has more difficulties and higher cost, and has almost no feasibility from the economical aspect. In China, the search of an inexpensive air source capable of replacing natural gas for producing direct reduced iron has important significance on the technical difficulty of attacking the gas-based direct reduced iron.
Based on the national conditions of rich coal and little gas in China, the coal chemical industry has long history of development in China, and almost all coal gas processes in the world have practical attempts in China, and the coal gas processes are relatively mature. The low-quality non-coking coal is adopted to produce coal gas for directly reducing iron, so that the gas source cost is greatly reduced, and a opportunity is provided for the gas-based shaft furnace technology to be applied in China. Currently, coal gasification technologies are mainly classified into fixed bed, fluidized bed and fluidized bed, wherein the fixed bed is classified into normal pressure gasification (e.g., UGI furnace, which tends to be eliminated due to serious pollution) and pressurized gasification (e.g., lurgi furnace with slag tapping and BGL furnace with slag tapping).
Table 1 shows typical gas compositions for BGL fixed bed pressurized gasification technology (data from the actual production of the BGL gasifier for medium coal map synthetic ammonia urea project). Compared with the fluidized bed or entrained flow technology, the fixed bed pressurizing technology can be suitable for the lump coal with the granularity range of 5mm to 50mm, and does not need complex coal grinding or coal preparation technology.
Table 1: typical gas composition for fixed bed coal gasification process
US 4205830 and US 4225340 both disclose a method and apparatus for producing direct reduced iron from coal gas by reacting coal, oxygen and steam in a coal gasifier, introducing the reducing gas into a shaft furnace, using a portion of the top gas as fuel and a portion of the top gas for cyclic removal of CO 2 And then reheating and mixing with coal gas and entering the shaft furnace. Lime (CaO) is added into the coal gasifier for sulfur removalAnd (3) chemical compounds. The method gives a gas component CH 4 The content of the catalyst is below 0.3%, which is obviously not suitable for treating high CH generated by fixed bed coal gasification 4 Coal gas with content (about 8%); and CaO is added into the coal gasification device, so that an ideal desulfurization effect cannot be achieved, and the current gas emission requirement is difficult to meet.
CN 203034041U discloses a system for producing gas by pulverized coal gasification and directly reducing metallurgy of a gas-based shaft furnace, which gives a basic flow from coal gasification, wet scrubbing, water gas shift, desulfurization and decarbonization to the reduction shaft furnace, but the patent does not give implementation details, and only has theoretical reference value; and the patent does not contemplate recycling of the reduced top gas, for a significant amount of CO/H after the reaction 2 It is obviously unsuitable to treat the top gas directly as flue gas.
CN 1141402C discloses a device for producing sponge iron by utilizing pressurized gasification of coal water slurry. The patent selects a Texaco furnace, and the Texaco furnace is communicated to a shaft furnace after being heated by gas conversion, NHD purification and two parallel heating furnaces. The method can be applied to coal with high sulfur content and recover sulfur, however, compared with a fixed bed coal gasifier, the Texaco furnace has high investment and high gasification pressure; and the method that the gas is heated by the heating furnace and then fed into the shaft furnace is adopted, so that CO gasification carburization reaction is easy to occur, and the furnace tube is damaged to cause bad results.
Therefore, how to fully utilize rich coal resources in China and develop a gas-based direct reduction iron technology, realize innovation and breakthrough of the Chinese gas-based direct reduction iron technology, select proper coal gasification technology, gas conversion technology, gas purification technology and reduction shaft furnace technology, and integrate the technologies are the problems to be solved urgently.
Disclosure of Invention
Aiming at the problems existing in the existing method and system for producing direct reduced iron by using coal gas, the invention provides a system and a method for producing direct reduced iron by using BGL gasification gas through steam conversion. The invention can realize the effective integration of coal gasification technology, gas conversion technology, gas purification technology and reduction shaft furnace technology by combining a fixed bed pressurized gasifier (BGL coal gasifier) with a water gas shift unit, a conversion unit and a gas-based reduction unit, and provides a system and a method for producing direct reduced iron by using coal gas with higher material and energy utilization rate.
To achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a system for producing direct reduced iron by steam reforming of BGL gasification gas, the system comprising a BGL gasification unit, a dust removal scrubbing unit, a water gas shift unit, a desulfurization decarbonization unit, a reforming unit, and a gas-based reduction unit, which are sequentially connected.
In the invention, compared with a pulverized coal gasifier or a coal water slurry gasifier, the fixed bed pressurized gasifier (BGL coal gasifier) has the advantages of lower investment, stable operation, no need of a complex coal preparation system and less pollution; and CH in crude gas produced by the BGL coal gasifier 4 The higher content, generally above 8%, is beneficial to increasing the carbon content of the reduced iron product in the production of direct reduced iron; and through the conversion of the subsequent conversion unit, the H in the synthesis gas can be improved 2 And CO content, thereby improving the yield of reduced iron.
The following technical scheme is a preferred technical scheme of the invention, but is not a limitation of the technical scheme provided by the invention, and the technical purpose and beneficial effects of the invention can be better achieved and realized through the following technical scheme.
As a preferable technical scheme of the invention, the dust removing washing unit is a washing tower; the dust removal washing unit is used for removing dust and cooling the raw gas synthesized by the BGL gasifier, and the temperature of the raw gas is reduced to the treatment temperature of the water-gas shift unit so as to carry out subsequent water-heat shift.
Preferably, the water gas shift unit is a water gas shift unit.
In the invention, the water-gas conversion unit adopts a water-gas conversion technology, and compared with the traditional adiabatic conversion, the device overtemperature caused by reaction heat release is avoided by accurately controlling the temperature, the conversion efficiency is improved, the conversion requirement can be met in one section, and the device of the conversion unit is simplified.
The invention is regulated by a water gas shift unitH in gas 2 The molar ratio of the catalyst to CO meets the production index requirement of the gas-based reduction unit.
Preferably, the water gas shift device employs a one-stage shift heat shift.
Preferably, the shift catalyst adopted in the water-gas shift device is a wide-temperature sulfur-resistant shift catalyst, the application range of the shift catalyst is 190-500 ℃, and the catalyst has no upper limit requirement on sulfur content.
As a preferable technical scheme of the invention, the sulfur-containing material of the desulfurization and decarbonization unit is connected with a sulfur recovery unit, and the sulfur recovery unit adopts methods such as a Claus method to recover sulfur in the coal gas.
Preferably, a pressure regulating unit is arranged between the desulfurization and decarbonization unit and the conversion unit. The pressure regulating unit is used for reducing the pressure of the raw gas to be in a range which meets the production requirement of the gas-based reduction unit and simultaneously recovering energy.
Preferably, the pressure regulating unit employs a turbine, typical but non-limiting examples of which are: steam turbines, but are not limited to steam turbines.
Preferably, the gas outlet of the pressure regulating unit is connected with the feed gas inlet of the conversion unit and the fuel inlet of the conversion unit. The pressure-reducing coal gas processed by the pressure regulating unit is divided into two parts, wherein one part is used as raw gas to enter the conversion unit for conversion reaction, and the other part is used as fuel to be connected with a burner of the conversion unit, and is used as fuel to be supplied to the conversion unit when the vehicle is started or the top gas is not available.
As a preferable technical scheme of the invention, the conversion unit is a low water-carbon ratio steam conversion furnace, H thereof 2 O and CH 4 The molar ratio of (a) is 1.1 to 1.5, for example, 1.1, 1.2, 1.3, 1.4, or 1.5, etc., but is not limited to the recited values, and other non-recited values within the range are equally applicable.
In the invention, the conversion unit adopts the steam conversion furnace with low water-carbon ratio to replace a common heating furnace, can reduce the dust damage of the metal furnace tube caused by CO disproportionation carburization, can prolong the service life of the furnace tube, and is more suitable for CH 4 High content coal gasThe method comprises the steps of carrying out a first treatment on the surface of the Meanwhile, the problem of the increase of the oxidation degree of the synthesis gas caused by common steam reforming is avoided.
Preferably, the conversion unit comprises a water vapour injection device.
Preferably, the gas-based reduction unit is a HyL-III shaft furnace provided with a pellet inlet, a synthesis gas injection inlet, a top gas outlet and a reduced iron outlet.
As a preferred technical scheme of the invention, the system further comprises a top gas washing device and a top gas compression device, wherein a top gas outlet of the gas-based reduction unit is connected with a gas inlet of the top gas washing device, a gas outlet of the top gas washing device is respectively connected with a gas inlet of the top gas compression device and a fuel inlet of the conversion unit, and a gas outlet of the top gas compression device is connected with a gas inlet of the water-gas conversion unit.
Namely, the top gas generated by the gas-based reduction unit is divided into two parts after being washed, one part is used as fuel of the conversion unit, and the other part is compressed by the compression device and then mixed with the coal gas to enter the water-gas shift unit to be used as raw gas to participate in the reaction.
The invention recycles the top gas generated by the gas-based reduction unit and can optimally regulate H in the raw gas 2 And the CO content, improves the utilization efficiency of raw material gas.
As a preferable technical scheme of the invention, a combustion flue gas outlet of the conversion unit is connected with a flue gas heat exchange system.
Preferably, the flue gas heat exchange system comprises a waste heat boiler and a combustion air preheater, wherein the combustion air preheater can be arranged behind the waste heat boiler, and the water vapor outlet of the flue gas heat exchange system is respectively connected with the water vapor inlet of the conversion unit, the water vapor inlet of the water vapor conversion unit and the water vapor inlet of the BGL gasifier. The heat in the combustion flue gas of the conversion unit is recovered to heat the boiler to generate hot steam for the BGL gasification furnace, the water gas shift unit and the conversion unit; at the same time, the compressed air is heated, providing hot air to the conversion unit.
In a second aspect, the present invention provides a method for processing the above system, the method comprising the steps of:
(1) Raw material coal is gasified with oxygen and water vapor in a BGL gasification unit to generate raw gas;
(2) The crude gas in the step (1) is subjected to dust removal and washing, and then subjected to water-gas shift reaction to obtain shifted gas;
(3) After desulfurization and decarbonization are carried out on the transformed coal gas in the step (2), a low water-carbon ratio steam conversion reaction is carried out, and synthesis gas is generated;
(4) And (3) enabling the synthesis gas to enter a gas-based reduction unit to be in countercurrent contact with the added pellets, and carrying out reduction reaction to generate reduced iron, wherein the reduced iron is sponge iron.
More specifically, the method comprises the following steps:
(1) Raw material coal is gasified with oxygen and water vapor in a BGL gasifier to generate raw gas;
(2) The crude gas in the step (1) enters a dust removal washing unit to be subjected to dust removal and washing, and then enters a water-gas shift unit to be subjected to water-gas shift reaction, so as to obtain shifted gas;
(3) The transformed coal gas enters a desulfurization and decarbonization unit to be subjected to desulfurization and decarbonization, and then enters a conversion unit to be subjected to steam conversion reaction with low water-carbon ratio to generate synthesis gas;
(4) And (3) enabling the synthesis gas to enter a gas-based reduction unit to be in countercurrent contact with the added pellets, and carrying out reduction reaction to generate reduced iron.
Wherein, the gasification reaction temperature in the step (1) is 1000 ℃ to 1600 ℃, the operation pressure is 1MPaG to 3MPaG, the temperature of the raw gas generated by the gasification reaction is 600 ℃ to 700 ℃, and the temperature of the raw gas is reduced to 200 ℃ to 350 ℃ after dust removal and washing; the reaction temperature of the water gas shift reaction in the step (2) is 200-300 ℃, and the reaction pressure is 1 MPaG-3 MPaG.
As a preferable technical scheme of the invention, the molar content of CO in the raw gas generated by the gasification reaction in the step (1) is 37-65%, H 2 The molar content of (C) is 24-30%, CH 4 The molar content of (2) is 6% -9%, CO 2 The molar content of (2) is 4-17%.
Preferably, H in the shifted gas of step (2) 2 The molar ratio of the catalyst to CO is 7-8. The subsequent steam reforming with low water-to-carbon ratio reduces the synthesis gas H 2 Ratio of/CO, water gas shift adjustment H 2 the/CO ratio is slightly higher than the HyL-III shaft furnace production requirement, so that the synthesis gas H is changed 2 the/CO ratio can meet the production needs of the shaft furnace.
In the invention, the water gas shift reaction is as follows: CO+H 2 O→CO 2 +H 2 +Q；
As a preferable technical scheme of the invention, after the coal gas is desulfurized and decarbonized in the step (3), the total sulfur content is less than 1mg/m 3 ，CO 2 The molar content is less than 1 percent.
Preferably, the transformed coal gas in the step (3) is subjected to desulfurization and decarbonization, pressure regulation and low water-carbon ratio steam conversion reaction.
Preferably, the pressure is regulated to a pressure of 0.5MPaG to 0.8MPaG, the pressure being such as to meet the production requirements of the gas-based reduction unit.
Preferably, the gas after the pressure adjustment is divided into two parts, wherein one part is used as raw material gas to participate in the low water-carbon ratio steam conversion reaction, and the other part is used as fuel for the low water-carbon ratio steam conversion reaction.
Preferably, H in the low water-to-carbon ratio steam reforming reaction of step (3) 2 O and CH 4 The molar ratio of (a) is 1.1 to 1.5, for example, 1.1, 1.2, 1.3, 1.4, or 1.5, etc., but is not limited to the recited values, and other non-recited values within the range are equally applicable.
In the invention, H in the synthesis gas is regulated through steam conversion reaction with low water-carbon ratio 2 Molar ratio to CO, thus H 2 O and CH 4 Is one of the key factors affecting the reaction result of the present invention.
Preferably, H in the synthesis gas of step (3) 2 The molar content of CO is > 90%, for example 91%, 92%, 93%, 94% or 95%, etc., but is not limited to the recited values, and other non-recited values within the range are equally applicable.
Preferably, the stepsStep (3) H in the synthesis gas 2 The molar ratio to CO is 5.6 to 6.5, for example, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, or 6.5, etc., but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the synthesis gas temperature in step (3) is 850 ℃ to 1000 ℃, for example 850 ℃, 870 ℃, 900 ℃, 930 ℃, 950 ℃, 970 ℃, 1000 ℃, or the like, but is not limited to the recited values, and other non-recited values within the range of values are equally applicable. Preferably, the pressure of the synthesis gas in step (3) is from 0.5MPaG to 0.8MPaG, for example, from 0.5MPa, 0.55MPa, 0.6MPa, 0.65MPa, 0.7MPa, 0.75MPa or 0.8MPa, etc., but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
As a preferable technical scheme of the invention, the combustion flue gas generated by the low water-carbon ratio steam conversion reaction in the step (3) is used as a heat source to exchange heat with a waste heat boiler and a combustion air preheater in a flue gas heat exchange system, the water vapor generated by the waste heat boiler after heating is returned to participate in gasification reaction, water-gas shift reaction and low water-carbon ratio steam conversion reaction, and the preheated air generated by the combustion air preheater after preheating participates in top gas combustion heat supply.
Preferably, the top gas generated in the reduction reaction in the step (4) is divided into two parts after being washed, one part is used as a reaction raw material to be returned to participate in the water-gas shift reaction after being compressed, and the other part is used as fuel for the low water-carbon ratio steam shift reaction to recover heat.
Compared with the prior art, the invention has the following beneficial effects:
(1) Compared with a pulverized coal gasification or coal water slurry gasification furnace, the fixed bed pressurized gasification furnace (BGL coal gasification furnace) is adopted in the invention, so that the investment is lower, the operation is stable, a complex coal preparation system is not needed, and the pollution is lower;
(2) The water-gas conversion technology is adopted in the invention, the over-temperature of the equipment caused by reaction heat release is avoided through the accurate control of the temperature, the conversion efficiency is improved, the conversion requirement can be met in one section, and the equipment of a conversion unit is simplified;
(3) The low water-carbon ratio reformer is used for replacing a common heating furnace, so that dust damage of a metal furnace tube caused by CO disproportionation carburization can be reduced, and the service life of the furnace tube can be prolonged; meanwhile, the problem of rising of the oxidation degree of the synthesis gas caused by common steam reforming is avoided;
(4) The invention adopts the mode of circulating participation reaction after washing the top gas, improves the utilization efficiency of raw gas, sets a waste heat boiler and a combustion air preheater for the reformer, recovers the sensible heat of flue gas, and improves the utilization efficiency of materials and energy sources, wherein byproduct steam can be used by the coal gasifier and the reformer;
(5) In the invention, the BGL coal gasifier is combined with the coal gasification technology, the gas conversion technology, the gas purification technology and the gas-based reduction unit technology, so that the limitation of natural gas in the gas-based direct reduction method can be overcome, the yield of the direct reduced iron can be improved, and the production cost can be reduced.
Drawings
FIG. 1 is a schematic diagram of a system for producing direct reduced iron from coal gas according to example 1 of the present invention;
the device comprises a 1-BGL gasification unit, a 2-dust removal washing unit, a 3-water-gas shift unit, a 4-desulfurization and decarbonization unit, a 5-pressure regulation unit, a 6-conversion unit, a 7-gas-based reduction unit, an 8-top gas washing device, a 9-top gas compression device, a 10-flue gas heat exchange system and an 11-sulfur recovery unit.
Detailed Description
For better illustrating the present invention, the technical scheme of the present invention is convenient to understand, and the present invention is further described in detail below. The following examples are merely illustrative of the present invention and are not intended to represent or limit the scope of the invention as defined in the claims.
The invention provides a system for producing direct reduced iron by steam reforming of BGL gasification gas and a treatment method thereof, wherein the system comprises a BGL gasification unit 1, a dust removal washing unit 2, a water gas shift unit 3, a desulfurization and decarbonization unit 4, a reforming unit 6 and a gas-based reduction unit 7 which are connected in sequence.
The processing method comprises the following steps:
(1) Raw material coal is gasified with oxygen and water vapor in a BGL gasification unit 1 to generate raw gas;
(2) The crude gas in the step (1) is subjected to dust removal and washing, and then subjected to water-gas shift reaction to obtain shifted gas;
(3) After desulfurization and decarbonization are carried out on the transformed coal gas in the step (2), a low water-carbon ratio steam conversion reaction is carried out, and synthesis gas is generated;
(4) And (3) enabling the synthesis gas to enter a gas-based reduction unit 7 to be in countercurrent contact with the added pellets, and carrying out reduction reaction to generate reduced iron.
The following are exemplary but non-limiting examples of the invention:
example 1:
the embodiment provides a system for producing direct reduced iron by steam reforming of BGL gasification gas and a treatment method thereof, as shown in fig. 1, the system comprises a BGL gasification unit 1, a dust removal washing unit 2, a water gas shift unit 3, a desulfurization and decarbonization unit 4, a pressure regulating unit 5, a reforming unit 6 and a gas-based reduction unit 7 which are connected in sequence; it also comprises a top gas washing device 8 and a top gas compression device 9.
Wherein, the BGL gasification unit 1 is provided with a lump coal feeding device, a steam inlet and an oxygen inlet;
the dust removing and washing unit 2 is a washing tower;
the water-gas shift unit 3 is a water-gas shift device, adopts a section of heat transfer shift, adopts a shift catalyst which is a wide-temperature sulfur-resistant shift catalyst, and has the application range of 190-500 ℃;
the sulfur-containing material of the desulfurization and decarbonization unit 4 is connected with a sulfur recovery unit 11;
the pressure regulating unit 5 adopts a turbine, and an air outlet of the pressure regulating unit is connected with a raw material gas inlet of the conversion unit 6 and a fuel inlet of the conversion unit 6;
the conversion unit 6 is a low water-carbon ratio steam reformer, which comprises a steam injection device; the combustion flue gas outlet of the conversion unit 6 is connected with a flue gas heat exchange system 10; the flue gas heat exchange system 10 comprises a waste heat boiler and a combustion air preheater, and the water vapor outlet of the flue gas heat exchange system 10 is respectively connected with the water vapor inlet of the reforming unit 6, the water vapor inlet of the water vapor shift unit 3 and the water vapor inlet of the BGL gasification unit 1.
The gas-based reduction unit 7 is a HyL-III shaft furnace provided with a pellet inlet, a synthesis gas injection port, a top gas outlet and a reduced iron outlet.
The top gas outlet of the gas-based reduction unit 7 is connected with the gas inlet of the top gas washing device 8, the gas outlet of the top gas washing device 8 is respectively connected with the gas inlet of the top gas compression device 9 and the fuel inlet of the conversion unit 6, and the gas outlet of the top gas compression device 9 is connected with the gas inlet of the water gas shift unit 3.
Taking 100 ten thousand tons/year of direct reduced iron production as an example, the method for processing by adopting the system comprises the following steps:
(1) 50t/h of lignite is fed into the BGL gasification unit 1, and 16t/h of steam and 14510Nm are fed into the BGL gasification unit 1 3 And (2) carrying out gasification reaction on the brown coal, the oxygen and the water vapor in the coal gasification furnace to generate raw gas, wherein the yield of the raw gas is 84680Nm 3 /h；
(2) The crude gas in the step (1) enters a dust removal washing unit 2 for dust removal and washing, is cooled to 250 ℃, then enters a water-gas shift unit 3, and is introduced into 45727Nm under the conditions of 250 ℃ and 2MPaG 3 steam/H water gas shift and H regulation 2 The molar ratio to CO is 7.4, and 130407Nm of shifted gas is obtained 3 /h；
(3) The transformed coal gas in the step (2) enters a desulfurization and decarbonization unit 4 for desulfurization and decarbonization treatment, so that the total sulfur content is reduced to 1mg/m 3 The following, and complete removal of CO 2 The removed sulfur enters a sulfur recovery unit 11 to recover sulfur by a Claus method, and the annual sulfur recovery amount of lignite with the sulfur content of 2% is 0.8 ten thousand tons;
the gas after desulfurization and decarbonization is 81293Nm 3 After regulating the pressure to 0.6MPaG by the pressure regulating unit 5, 11381Nm 3 The/h coal gas is used as fuel to provide heat energy for the conversion unit 6 and heat the synthesis gas from low temperature to 950 ℃, and the rest of the coal gas is 69912Nm 3 H into the conversion unit 6Steam conversion with low water-carbon ratio is carried out to convert CH in synthesis gas 4 Conversion to H 2 And CO, steam and CH 4 Molar ratio of 1.2, resulting in 83000Nm 3 Synthesis gas/H, wherein H 2 Molar ratio to CO of 6.2, H 2 The +CO molar content is 92 percent, which accords with HyL-III production index;
(4) Step (3), the synthesis gas enters from the middle part of the gas-based reduction unit 7, and is in countercurrent contact with 188t/h pellets added from the upper part of the gas-based reduction unit 7 to carry out reduction reaction, so as to generate reduced metallic iron, and the production rate of the direct reduced iron of the gas-based reduction unit 7 is 125t/h;
part of the top gas of the gas-based reduction unit 7 is recycled as a reaction raw material to participate in steam conversion with low water-carbon ratio, so that the waste of materials generated by the fact that the coal gas cannot reach higher conversion rate in one-time reaction in the gas-based reduction unit 7 is avoided; part of the waste heat is used as fuel to supply heat for the reaction, the combustion flue gas is used as a heat source to exchange heat with a waste heat boiler and a combustion air preheater in the flue gas heat exchange system 10, water vapor generated by heating the waste heat boiler is returned to participate in the coal gasification reaction, the water-gas shift reaction and the low water-carbon ratio steam shift reaction, and air preheated by the combustion air preheater participates in the combustion reaction.
In this example, the temperature, pressure and gas composition of the raw gas, the water gas shifted gas, the desulphurized decarbonized purified gas and the low water to carbon ratio steam reforming reaction synthesis gas produced in each reaction stage are shown in table 2.
Table 2: typical gas composition of BGL fixed bed coal gasification process
CO+H in the coal gas component after desulfurization and decarbonization 2 The content of the active ingredient CO+H in the synthesis gas is only 90.1 percent, and after the conversion of the low water-carbon ratio, the active ingredient CO+H in the synthesis gas 2 Can reach 92.3 percent.
Compared with the common heating furnace, the purified gas is converted by steam with low water-carbon ratio, thereby improving CH 4 The utilization rate increases the reduction degree of the synthesis gas; through CH 4 And H is 2 O reacts to generate CO+H 2 The effective gas yield is improved by 21.6 percent, and the yield of the reduced iron can be increased by 27.0t/h.
The BGL gasification furnace for producing 100 ten thousand tons per year of direct reduced iron with the daily lignite feeding amount of 1198 tons and the daily lignite feeding amount of 1500 tons can meet the requirements, and one-on-one-standby can be adopted in actual production.
Example 2:
this example provides a system for producing direct reduced iron by steam reforming of BGL gasification gas and a method for processing the same, and the system has the same structure as in example 1.
Taking 50 ten thousand tons/year of direct reduced iron production as an example, the method for processing by adopting the system comprises the following steps:
(1) 25t/h of lignite is fed into the BGL gasification unit 1, 8t/h of steam and 7255Nm are fed into the BGL gasification unit 1 3 And (2) carrying out gasification reaction on the oxygen, the lignite, the oxygen and the water vapor in a coal gasification furnace to generate raw gas, wherein the yield of the raw gas is 42340Nm 3 /h；
(2) The crude gas in the step (1) enters a dust removal washing unit 2 for dust removal and washing, is cooled to 250 ℃, then enters a water-gas shift unit 3, and is introduced with 22863Nm under the conditions of 250 ℃ and 2MPaG 3 steam/H water gas shift and H regulation 2 The molar ratio with CO is 7.4, and 65204Nm of shifted gas is obtained 3 /h；
(3) The transformed coal gas in the step (2) enters a desulfurization and decarbonization unit 4 for desulfurization and decarbonization treatment, so that the total sulfur content is reduced to 1mg/m 3 The following, and complete removal of CO 2 ；
The gas after desulfurization and decarbonization is 48256Nm 3 And/h, which is regulated to a pressure of 0.6MPaG by a pressure regulating unit 5, 5690Nm thereof 3 The/h coal gas is used as fuel to provide heat energy for the conversion unit 6 and heat the synthesis gas from low temperature to 950 ℃, and the rest of the coal gas is 34956Nm 3 And/h enters a conversion unit 6 to carry out steam conversion reaction with low water-carbon ratio, and CH in the synthesis gas is converted 4 Conversion to H 2 And CO, steam and CH 4 Molar ratio of 1.2, yielding 41500Nm 3 Synthesis gas/H, wherein H 2 Molar ratio to CO of 6.2, H 2 The +CO molar content is 92 percent, which accords with HyL-III production index;
(4) And (3) allowing the synthesis gas to enter from the middle part of the gas-based reduction unit 7, and carrying out countercurrent contact with the 94t/h pellets added from the upper part of the gas-based reduction unit 7 to carry out reduction reaction to generate reduced metallic iron, wherein the production rate of the direct reduced iron of the gas-based reduction unit 7 is 62.5t/h.
In this example, the temperature, pressure and gas composition examples of the raw gas, the water gas shift-treated gas, the desulfurization decarbonized purified gas and the low water to carbon ratio steam reforming reaction synthesis gas produced in each reaction stage were the same as those in example 1.
Compared with the common heating furnace, the purified gas is converted by steam with low water-carbon ratio, thereby improving CH 4 The utilization rate increases the reduction degree of the synthesis gas; through CH 4 And H is 2 O reacts to generate CO+H 2 The effective gas yield is improved by 21.6 percent, and the yield of the reduced iron can be increased by 13.5t/h.
The daily lignite amount of 50 ten thousand tons/year of direct reduced iron is about 600 tons, the single daily lignite amount 800 tons of BGL gasification furnace can meet the requirements, and one-on-one-off can be adopted in actual production.
Example 3:
this example provides a system for producing direct reduced iron by steam reforming of BGL gasification gas and a method for processing the same, and the system has the same structure as in example 1.
Taking 150 ten thousand tons/year of direct reduced iron production as an example, the method for processing by adopting the system comprises the following steps:
(1) Lignite is fed into the BGL gasification unit 1 at a rate of 75t/h, and 24t/h steam and 21743Nm are fed into the BGL gasification unit 1 3 And (3) carrying out gasification reaction on the oxygen, the lignite, the oxygen and the water vapor in a BGL coal gasifier to generate raw gas, wherein the yield of the raw gas is 126892Nm 3 /h；
(2) The crude gas in the step (1) enters a dust removal washing unit 2 for dust removal and washing, is cooled to 250 ℃, then enters a water-gas shift unit 3, and is introduced with 70045Nm under the conditions of 250 ℃ and 2MPaG 3 steam/H water gas shift and H regulation 2 The molar ratio of the catalyst to CO is 8.0, and 196937Nm of converted coal gas is obtained 3 /h；
(3) The transformed coal gas in the step (2) enters a desulfurization and decarbonization unit 4 for desulfurization and decarbonization treatment, so that the total sulfur content is reduced to 1mg/m 3 The following, and complete removal of CO 2 The method comprises the steps of carrying out a first treatment on the surface of the The removed sulfur enters a sulfur recovery unit 11 to recover sulfur by a Claus method, and the annual sulfur recovery amount of lignite with the sulfur content of 2 percent is about 1.2 ten thousand tons;
the gas after desulfurization and decarbonization is 121817Nm 3 And/h, which is regulated to a pressure of 0.8MPaG by a pressure regulating unit 5, of which 19491Nm 3 The/h coal gas is used as fuel to provide heat energy for the conversion unit 6 and heat the synthesis gas from low temperature to 1000 ℃, and the rest of the coal gas is 102326Nm 3 And/h enters a conversion unit 6 to carry out steam conversion reaction with low water-carbon ratio, and CH in the synthesis gas is converted 4 Conversion to H 2 And CO, steam and CH 4 Molar ratio of 1.3, resulting in 125000Nm 3 Synthesis gas/H, wherein H 2 Molar ratio to CO of 6.3, H 2 The +CO molar content is 93 percent, which meets the production requirement of HyL-III shaft furnace;
(4) Step (3), the synthesis gas enters from the middle part of the gas-based reduction unit 7, and is in countercurrent contact with 281t/h pellets added from the upper part of the gas-based reduction unit 7 to carry out reduction reaction, so as to generate reduced metallic iron, wherein the production rate of the direct reduced iron of the gas-based reduction unit 7 is 187.5t/h;
in this example, the temperature, pressure and gas composition of the raw gas, the water gas shift-treated gas, the desulfurization decarbonized purified gas and the low water to carbon ratio steam reforming reaction synthesis gas produced in each reaction stage are shown in table 3.
Table 3: typical gas composition for HyL-III shaft furnace for BGL fixed bed coal gasification process
The quantity of the brown coal charged per year for producing 150 ten thousand tons/year of direct reduced iron is about 1794 tons, 1 single BGL gasification furnace with 2000 tons of coal charged per day can meet the requirement, and two-open-one-standby can be adopted in actual production.
Compared with the common heating furnace, the purified gas is converted by steam with low water-carbon ratio, thereby improving CH 4 The utilization rate increases the reduction degree of the synthesis gas, reduces the risk of carbon accumulation in the furnace, and increases the service life of the furnace tube; through CH 4 And H is 2 O reacts to generate CO+H 2 The effective gas yield is improved by 26.1 percent, and the yield of the reduced iron can be increased by 48.9t/h.
Example 4:
this example provides a system for producing direct reduced iron by steam reforming of BGL gasification gas and a method for processing the same, and the system has the same structure as in example 1.
Taking 80 ten thousand tons/year of direct reduced iron production as an example, the method for processing by adopting the system comprises the following steps:
(1) Lignite is fed into the BGL gasification unit 1 according to 40t/h, and 13t/h steam and 11695Nm are fed into the BGL gasification unit 1 3 Carrying out gasification reaction on brown coal, oxygen and water vapor in a BGL coal gasifier to generate raw gas, wherein the yield of the raw gas is 68252Nm 3 /h；
(2) The crude gas in the step (1) enters a dust removal washing unit 2 for dust removal and washing, is cooled to 250 ℃, then enters a water-gas shift unit 3, and is introduced with 36310Nm under the conditions of 250 ℃ and 2MPaG 3 steam/H water gas shift and H regulation 2 The molar ratio with CO is 7.0, and 104562Nm of shifted gas is obtained 3 /h；
(3) The transformed coal gas in the step (2) enters a desulfurization and decarbonization unit 4 for desulfurization and decarbonization treatment, so that the total sulfur content is reduced to 1mg/m 3 The following, and complete removal of CO 2 The method comprises the steps of carrying out a first treatment on the surface of the The removed sulfur enters a sulfur recovery unit 11 to recover sulfur by a Claus method, and the annual sulfur recovery amount of lignite with the sulfur content of 2% is 0.6 ten thousand tons;
the gas after desulfurization and decarbonization is 65522Nm 3 And/h, which is regulated to a pressure of 0.5MPaG by a pressure regulating unit 5, 7862Nm 3 The/h coal gas is used as fuel to provide heat energy for the conversion unit 6 and heat the synthesis gas from low temperature to 850 ℃, and the rest of the coal gas is 57659Nm 3 And/h enters a conversion unit 6 to carry out steam conversion reaction with low water-carbon ratio, and CH in the synthesis gas is converted 4 Conversion to H 2 And CO, steam and CH 4 Molar ratio of 1.1, yielding 66700Nm 3 Synthesis gas/H, wherein H 2 Molar ratio to CO of 6.4, H 2 The +CO molar content is 90 percent, which meets the production requirement of HyL-III shaft furnace;
(4) Step (3), the synthesis gas enters from the middle part of the gas-based reduction unit 7, and is in countercurrent contact with 150t/h pellets added from the upper part of the gas-based reduction unit 7 to carry out reduction reaction, so as to generate reduced metal iron, wherein the production rate of the direct reduced iron of the gas-based reduction unit 7 is 100t/h;
in this example, the temperature, pressure and gas composition of the raw gas, the water gas shift-treated gas, the desulfurization decarbonized purified gas and the low water to carbon ratio steam reforming reaction synthesis gas produced in each reaction stage are shown in Table 4.
Table 4: typical gas composition for HyL-III shaft furnace for BGL fixed bed coal gasification process
The BGL gasification furnace for producing 80 ten thousand tons/year direct reduced iron with daily lignite feeding quantity of about 965 tons and 1 single daily lignite feeding quantity of 1100 tons can meet the requirements, and one-on-one-standby can be adopted in actual production.
Compared with the common heating furnace, the purified gas is converted by steam with low water-carbon ratio, thereby improving CH 4 The utilization rate increases the reduction degree of the synthesis gas, reduces the risk of carbon accumulation in the furnace, and increases the service life of the furnace tube; through CH 4 And H is 2 O reacts to generate CO+H 2 The effective gas yield is improved by 15.3 percent, and the yield of the reduced iron can be increased by 15.3t/h.
Example 5:
this example provides a system for producing direct reduced iron by steam reforming of BGL gasification gas and a method for processing the same, and the system has the same structure as in example 1.
Taking 70 ten thousand tons/year of direct reduced iron production as an example, the method for processing by adopting the system comprises the following steps:
(1) Lignite is fed into the BGL gasification unit 1 according to 34t/h, and 11t/h steam and 9820Nm are fed into the BGL gasification unit 1 3 And (3) carrying out gasification reaction on the oxygen, the lignite, the oxygen and the water vapor in a BGL gasifier to generate raw gas, wherein the yield of the raw gas is 57311Nm 3 /h；
(2) The crude gas in the step (1) enters a dust removal washing unit 2 for dust removal and washing, is cooled to 250 ℃, then enters a water-gas shift unit 3, and is introduced with 30490Nm under the conditions of 250 ℃ and 2MPaG 3 steam/H water gas shift and H regulation 2 The molar ratio with CO is 7.0, and 87800Nm of shifted gas is obtained 3 /h；
(3) The transformed coal gas in the step (2) enters a desulfurization and decarbonization unit 4 for desulfurization and decarbonization treatment, so that the total sulfur content is reduced to below 1mg/m < 3 >, and CO is completely removed 2 ；
The gas after desulfurization and decarbonization is 55019Nm 3 And/h, which was regulated to a pressure of 0.6MPaG (gauge pressure) by the pressure regulating unit 5, of which 8803Nm 3 The/h coal gas is used as fuel to provide heat energy for the conversion unit 6 and heat the synthesis gas from low temperature to 1000 ℃, and the rest of the coal gas is 46216Nm 3 And/h enters a conversion unit 6 to carry out steam conversion reaction with low water-carbon ratio, and CH in the synthesis gas is converted 4 Conversion to H 2 And CO, steam and CH 4 The molar ratio was 1.5, yielding 58000Nm 3 Synthesis gas/H, wherein H 2 Molar ratio to CO of 5.6, H 2 The +CO molar content is 93.3 percent, which meets the production requirement of HyL-III shaft furnace;
(4) Step (3), the synthesis gas enters from the middle part of the gas-based reduction unit 7, and is in countercurrent contact with 131t/h pellets added from the upper part of the gas-based reduction unit 7 to carry out reduction reaction, so as to generate reduced metallic iron, wherein the production rate of the direct reduced iron of the gas-based reduction unit 7 is 87.5t/h;
in this example, the temperature, pressure and gas composition of the raw gas, the water gas shift-treated gas, the desulfurization decarbonized purified gas and the low water to carbon ratio steam reforming reaction synthesis gas produced in each reaction stage are shown in table 5.
Table 5: typical gas composition for HyL-III shaft furnace for BGL fixed bed coal gasification process
The BGL gasification furnace for producing 70 ten thousand tons/year direct reduced iron with the daily lignite feeding amount of about 810 tons and 1 single daily lignite feeding amount of 1000 tons can meet the requirements, and one-on-one-standby can be adopted in actual production.
Compared with the common heating furnace, the purified gas is converted by steam with low water-carbon ratio, thereby improving CH 4 The utilization rate increases the reduction degree of the synthesis gas; through CH 4 And H is 2 O reacts to generate CO+H 2 The effective gas yield is improved by 30 percent, and the yield of the reduced iron can be increased by 26.2t/h.
In the invention, the BGL coal gasification combined coal gasification technology, water gas shift technology, gas purification technology, low water-carbon ratio steam conversion technology and gas-based reduction technology are adopted, so that the limitation of natural gas in the gas-based direct reduction method can be overcome, and the production cost is reduced.
The applicant states that the detailed process equipment and process flows of the present invention are described by the above examples, but the present invention is not limited to, i.e., does not mean that the present invention must be practiced in dependence upon, the above detailed process equipment and process flows. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.
Claims (17)
1. A system for producing direct reduced iron by steam reforming of BGL gasification gas is characterized by comprising a BGL gasification unit (1), a dust removal washing unit (2), a water gas shift unit (3), a desulfurization and decarbonization unit (4) and a pressure regulating unit which are connected in sequence(5) The device comprises a conversion unit (6), a gas-based reduction unit (7), a top gas washing device (8) and a top gas compression device (9); the conversion unit (6) is a low water-carbon ratio steam reformer, H thereof 2 O and CH 4 The molar ratio of (2) is 1.1-1.5;
the gas outlet of the pressure regulating unit (5) is connected with the raw gas inlet of the conversion unit (6) and the fuel inlet of the conversion unit (6);
the top gas outlet of the gas-based reduction unit (7) is connected with the gas inlet of the top gas washing device (8), the gas outlet of the top gas washing device (8) is respectively connected with the gas inlet of the top gas compression device (9) and the fuel inlet of the conversion unit (6), and the gas outlet of the top gas compression device (9) is connected with the gas inlet of the water gas conversion unit (3);
the combustion flue gas outlet of the conversion unit (6) is connected with a flue gas heat exchange system (10), the flue gas heat exchange system (10) comprises a waste heat boiler and a combustion air preheater, and the water vapor outlet of the flue gas heat exchange system (10) is respectively connected with the water vapor inlet of the conversion unit (6), the water vapor inlet of the water vapor conversion unit (3) and the water vapor inlet of the BGL gasification unit (1);
the method for producing direct reduced iron using the system comprises the steps of:
(1) Raw material coal is gasified with oxygen and water vapor in a BGL gasification unit (1) to generate raw gas; the molar content of CO in the raw gas generated by the gasification reaction is 37-65%, H 2 The molar content of (C) is 24-30%, CH 4 The molar content of (2) is 6% -9%, CO 2 The molar content of (2) is 4-17%;
(2) The crude gas in the step (1) is subjected to dust removal and washing, and then subjected to water-gas shift reaction to obtain shifted gas; h in the gas after water gas shift 2 The molar ratio of the catalyst to CO is 7-8;
(3) Desulfurizing and decarbonizing the transformed coal gas in the step (2), and then performing a low water-carbon ratio steam conversion reaction, wherein H in the low water-carbon ratio steam conversion reaction 2 O and CH 4 The molar ratio of (1.1-1.5) to generate synthesis gas; h in the synthesis gas 2 Total molar content with CO > 90%, H 2 And CThe mol ratio of O is 5.6-6.5; the combustion flue gas generated by the low water-carbon ratio steam reforming reaction is used as a heat source to exchange heat with a waste heat boiler and a combustion air preheater in a flue gas heat exchange system (10), water vapor generated by heating the waste heat boiler returns to participate in gasification reaction, water-gas shift reaction and low water-carbon ratio steam reforming reaction, and preheated air generated by preheating the combustion air preheater participates in top gas combustion heat supply;
(4) And (3) enabling the synthesis gas to enter a gas-based reduction unit (7) to be in countercurrent contact with the added pellets, and carrying out reduction reaction to generate reduced iron.
2. The system according to claim 1, characterized in that the dust removal washing unit (2) is a washing tower.
3. The system according to claim 1, characterized in that the water gas shift unit (3) is a water gas shift device.
4. The system of claim 3, wherein the water gas shift device employs a one-stage shift heat shift.
5. The system of claim 4, wherein the shift catalyst employed in the water gas shift device is a wide temperature sulfur tolerant shift catalyst used in a range of 190 ℃ to 500 ℃.
6. The system according to claim 1, characterized in that the sulfur-containing material of the desulfurization and decarbonization unit (4) is connected to a sulfur recovery unit (11).
7. The system according to claim 1, characterized in that the pressure regulating unit (5) employs a turbine.
8. The system according to claim 1, characterized in that the conversion unit (6) comprises a water vapor injection device.
9. The system according to claim 1, characterized in that the gas-based reduction unit (7) is a HyL-III shaft furnace provided with a pellet inlet, a synthesis gas injection inlet, a top gas outlet and a reduced iron outlet.
10. A method of processing a system according to any one of claims 1-9, characterized in that the method comprises the steps of:
(1) Raw material coal is gasified with oxygen and water vapor in a BGL gasification unit (1) to generate raw gas; the molar content of CO in the raw gas generated by the gasification reaction is 37-65%, H 2 The molar content of (C) is 24-30%, CH 4 The molar content of (2) is 6% -9%, CO 2 The molar content of (2) is 4-17%;
(2) The crude gas in the step (1) is subjected to dust removal and washing, and then subjected to water-gas shift reaction to obtain shifted gas; h in the gas after water gas shift 2 The molar ratio of the catalyst to CO is 7-8;
(3) Desulfurizing and decarbonizing the transformed coal gas in the step (2), and then performing a low water-carbon ratio steam conversion reaction, wherein H in the low water-carbon ratio steam conversion reaction 2 O and CH 4 The molar ratio of (1.1-1.5) to generate synthesis gas; h in the synthesis gas 2 Total molar content with CO > 90%, H 2 The molar ratio of the catalyst to CO is 5.6 to 6.5; the combustion flue gas generated by the low water-carbon ratio steam reforming reaction is used as a heat source to exchange heat with a waste heat boiler and a combustion air preheater in a flue gas heat exchange system (10), water vapor generated by heating the waste heat boiler returns to participate in gasification reaction, water-gas shift reaction and low water-carbon ratio steam reforming reaction, and preheated air generated by preheating the combustion air preheater participates in top gas combustion heat supply;
(4) And (3) enabling the synthesis gas to enter a gas-based reduction unit (7) to be in countercurrent contact with the added pellets, and carrying out reduction reaction to generate reduced iron.
11. The process according to claim 10, wherein the total sulfur content of the shifted gas obtained in step (3) after desulfurization and decarbonization is less than 1mg/m 3 ，CO 2 The molar content is less than 1 percent.
12. The method according to claim 10, wherein the shifted gas in step (3) is subjected to desulfurization and decarbonization, and then subjected to pressure regulation, and then subjected to a low water-carbon ratio steam reforming reaction.
13. The process of claim 12, wherein the pressure is adjusted to a pressure of between 0.5mpa g and 0.8mpa g.
14. A process according to claim 13, wherein the pressure-regulated gas is split into two parts, one part being the feed gas to participate in the low water carbon steam reforming reaction and the other part being the fuel for the low water carbon steam reforming reaction.
15. The process of claim 10 wherein the temperature of the synthesis gas of step (3) is from 850 ℃ to 1000 ℃.
16. The process of claim 10, wherein the synthesis gas in step (3) has a pressure of from 0.5mpa g to 0.8mpa g.
17. The process of claim 10 wherein the top gas produced by the reduction reaction of step (4) is scrubbed and divided into two parts, one part being compressed and returned as a reaction feed to participate in the water gas shift reaction and the other part being recycled as fuel for the low water to carbon ratio steam shift reaction.
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