Method and system for producing iron ore concentrate and co-producing sulfuric acid through limonite flue gas desulfurization

Abstract

The invention discloses a method and a system for producing iron ore concentrate and co-producing sulfuric acid by using ferrous sulfate. The method comprises the following steps: reacting a raw material limonite solution to generate ferrous sulfate and ferric sulfate, and filtering silicon slag and a ferric sulfate solution; a ferric sulfate solution enters a concentration crystallizer, the ferric sulfate solution in the concentration crystallizer is subjected to concentration crystallization to obtain a ferric sulfate solid-liquid mixed solution, solid obtained through separation is ferric sulfate crystals, the ferric sulfate crystals enter a rotary kiln, and ferric sulfate is heated and decomposed in the rotary kiln to generate ferric oxide (iron ore concentrate) and sulfur trioxide flue gas; and the sulfur trioxide flue gas enters a sulfuric acid absorption tower to absorb the sulfur trioxide gas to generate sulfuric acid. The method effectively realizes production of iron ore concentrate and co-production of sulfuric acid through limonite flue gas desulfurization, combines flue gas desulfurization and iron ore beneficiation, and solves the problems of high operation cost, repeated investment, large investment, land occupation, secondary pollution, environmental influence and the like in the two industries.

Description

Technical Field

[0001] The invention relates to the technical field of flue gas treatment, iron concentrate and sulfuric acid production, and in particular to a method and a system for producing iron concentrate and sulfuric acid by desulfurizing limonite flue gas. Background Art

[0002] As an ore rich in iron, limonite will inevitably produce a large amount of sulfur trioxide flue gas during its mining and smelting process due to the high sulfur characteristics of the ore itself. If these flue gases are directly discharged into the atmosphere without proper treatment, they will cause a series of serious environmental problems such as acid rain and deterioration of air quality, posing a huge threat to human health, ecological balance and economic development.

[0003] However, most traditional flue gas treatment methods have the problem of resource waste. On the one hand, some chemicals or materials used in the treatment process may not be completely recycled and reused, resulting in increased resource consumption; on the other hand, if the by-products or waste generated by the treatment are not properly disposed of, they may also cause secondary pollution to the environment.

[0004] The above two industries face problems such as high operating costs, repeated and large investments, land occupation, secondary pollution, and environmental impacts.

[0005] Through certain innovative designs, several processes are combined to achieve the desulfurization of limonite flue gas to produce iron ore and sulfuric acid. Summary of the invention

[0006] The invention provides a method and system for producing iron concentrate and sulfuric acid by desulfurizing limonite flue gas, which solves the existing problems.

[0007] In order to achieve the above object, the present invention adopts the following technical scheme: a method for producing iron concentrate and sulfuric acid by desulfurization of limonite flue gas, comprising the following steps:

[0008] A. The raw material limonite solution and flue gas enter the desulfurization tower (1), in which sulfur dioxide reacts with iron oxide in the limonite to form ferrous sulfite, which is further oxidized to form ferric sulfate;

[0009] B. The ferric sulfate solution enters the silicon slag filter (3) through the desulfurization liquid circulation pump (2) for filtration, the filter cake obtained by filtration is silicon slag, and the filtrate obtained by filtration is the ferric sulfate solution;

[0010] C. the ferric sulfate solution enters the concentrating crystallizer (4), where the ferric sulfate solution is concentrated and crystallized to obtain a ferric sulfate solid-liquid mixed solution;

[0011] D. The ferric sulfate solid-liquid mixture enters the centrifuge (5) for separation, the separated solid is ferric sulfate crystals, and the separated liquid is the mother liquor which is returned to the concentrating crystallizer;

[0012] E. Ferrous sulfate crystals enter the rotary kiln (6), the pulverized coal is burned by the burner to provide heat for the rotary kiln, and the cold air is exchanged with the iron concentrate discharged from the rotary kiln in the cooler to recover heat before entering the burner to assist combustion. Ferrous sulfate is decomposed by heat in the rotary kiln to produce ferric oxide (iron concentrate) and sulfur trioxide flue gas;

[0013] F. Sulfur trioxide flue gas enters the sulfuric acid absorption tower (7), and sulfuric acid enters the sulfuric acid absorption tower (7) through the sulfuric acid absorption circulation pump (8). In the sulfuric acid absorption tower (7), sulfuric acid absorbs sulfur trioxide gas to generate sulfuric acid, and the product sulfuric acid is transported out of the system through the sulfuric acid absorption circulation pump (8).

[0014] The raw material of step A, limonite, contains 20-40% Fe and 20-40% SiO 2 40-50%, limonite solution concentration 20-40%, raw materials can be limonite, sulfuric acid slag, medium and low grade iron ore, steel slag and other iron-containing materials. Boiler flue gas temperature 130℃~150℃, liquid-gas ratio 1:1000; the operating conditions of the rotary kiln in step E: decomposition temperature 900~950℃, reaction time 1 hour, decomposition reaction atmosphere is oxidizing atmosphere, and the oxygen content of the kiln gas is ≥2~4%. The control process conditions of the sulfuric acid absorption tower: temperature 60℃~80℃, liquid-gas ratio 1:500.

[0015] Its desulfurization mechanism: iron oxide reacts chemically with sulfur dioxide in flue gas to generate ferrous sulfite, which is further oxidized to obtain ferric sulfate. The main reaction is:

[0016] Fe 2 O 3 +3SO 2 →Fe 2 (SO 3 )3

[0017] Fe 2 (SO 3 ) 3 +1.5O 2 →Fe 2 (SO 4 ) 3

[0018] Its high temperature decomposition mechanism: ferrous sulfate enters the rotary kiln for high temperature calcination, controlling the temperature at 900-950°C, the time for 60 minutes, and the excess air of 5%. The reactions involved are:

[0019] Fe 2 (SO 4 ) 3→Fe 2 O 3 +3SO 3

[0020] Its sulfuric acid absorption mechanism: sulfuric acid is used to absorb sulfur trioxide to produce sulfuric acid, and the absorption temperature and concentration are controlled by heat exchange to produce qualified sulfuric acid products. The main reactions involved are:

[0021] SO 3 +H 2 O→H 2 SO 4

[0022] The desulfurization tower, desulfurization liquid circulation pump, silicon slag filter, rotary kiln, sulfuric acid absorption tower and sulfuric acid absorption circulation pump are connected in sequence through pipelines. The silicon slag filter (3) is used to filter the desulfurization slurry to obtain silicon slag filter cake and iron sulfate filtrate; the concentration crystallizer (4) is used to concentrate the iron sulfate solution and crystallize the iron sulfate; the centrifuge (5) is used to separate the iron sulfate crystals and the iron sulfate mother liquor; the rotary kiln (6) is used to oxidize and decompose the iron sulfate to produce iron concentrate and sulfur trioxide flue gas; the sulfuric acid absorption tower (7) is used to absorb sulfur trioxide in the flue gas with sulfuric acid to produce sulfuric acid; the sulfuric acid absorption circulation pump (8) is used to pressurize and transport sulfuric acid. One side of the sulfuric acid absorption tower is connected to a treatment box, and the inside of the treatment box is connected to a filter plate for treating and reducing dust on the sulfur trioxide gas. A double-layer spray structure is arranged inside the sulfuric acid absorption tower, and a circulating spray structure is connected to the lower end of the sulfuric acid absorption tower.

[0023] Preferably, a long plate is connected to the lower end of the sulfuric acid absorption tower, and springs are connected to the four corners of the lower end of the long plate, a damper is arranged inside the spring, and a vertical cylinder is connected to the lower end of the spring.

[0024] Preferably, a vertical plate is connected below the processing box, and a recovery box is connected to the lower end of the processing box, a first transfer pipe is connected to the upper end of one side of the processing box, and a second transfer pipe is connected to the other side of the first transfer pipe, and one end of the second transfer pipe is connected to the sulfuric acid absorption tower.

[0025] Preferably, a solution placement area is provided at the lower end of the sulfuric acid absorption tower, and two third transfer pipes are connected to one end of the outside of the sulfuric acid absorption tower near the solution placement area, one end of each of the two third transfer pipes is connected to a water pump, and one end of the water pump is connected to a fourth transfer pipe.

[0026] Preferably, one end of the fourth transmission tube is connected to the fifth transmission tube via a flange ring, and the other side of the fifth transmission tube is connected to a plurality of water pipes at equal intervals, and the lower end of the water pipe is connected to a plurality of nozzles.

[0027] Preferably, a buffer plate is spaced apart below the nozzle, and a plurality of through holes are formed on the buffer plate.

[0028] Preferably, a demister plate is connected to the upper end of the interior of the sulfuric acid absorption tower, and an exhaust pipe is connected to the middle of the upper end of the sulfuric acid absorption tower.

[0029] Preferably, a concentrator crystallizer and a centrifuge are provided between the silicon slag filter and the rotary kiln, and the mother liquor separated by the centrifuge is returned to the concentrator crystallizer through a pipeline.

[0030] Preferably, the concentrating crystallizer comprises a round barrel, a rotating rod is connected to the inside of the round barrel, and two stirring rods are respectively arranged on the upper and lower sides of the rotating rod, and a motor is connected to the upper end of the rotating rod.

[0031] Preferably, the outer wall of the barrel is connected to a heat-conducting ring plate, and a plurality of heaters are connected at equal intervals inside the heat-conducting ring plate. A protective cover is provided outside the barrel, and an electric valve is connected to the lower end of the barrel.

[0032] A system for producing iron concentrate and sulfuric acid by desulfurizing limonite flue gas is formed by connecting the structures used in the above method.

[0033] The beneficial effects of the present invention are as follows: the present invention realizes the production of iron concentrate and sulfuric acid by desulfurizing limonite flue gas, is suitable for flue gas desulfurization, utilizes iron oxide of limonite to replace traditional limestone flue gas desulfurization, reduces the cost of flue gas desulfurization, improves desulfurization efficiency, and realizes the production of sulfuric acid from sulfur dioxide in flue gas, and the iron oxide in limonite is enriched to produce iron concentrate, and no secondary pollution is generated without desulfurization gypsum, which has good economic and environmental benefits, and does not require the mining of limestone for flue gas desulfurization, which reduces the impact on the environment, combines flue gas desulfurization with iron ore dressing, and solves the problems of high operating cost, repeated and large investment, land occupation, secondary pollution, environmental impact, etc. existing in these two industries.

[0034] The system discharges sulfur trioxide gas into the sulfuric acid absorption tower, starts the water pump to transfer the treatment solution to the water pipe and sprays the flue gas through the nozzle, cooperates with the buffer plate below to buffer the flue gas, so that the flue gas is fully in contact with the sulfuric acid solution, and the SO 2 It reacts chemically with the sprayed sulfuric acid solution to generate sulfuric acid, realizing the comprehensive utilization of resources. The demister plate at the upper end prevents sulfuric acid droplets from being discharged with the flue gas, thereby improving the cleanliness of the exhaust gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a system schematic diagram of the present invention.

[0036] Figure 2 It is a schematic diagram of the sulfuric acid absorption tower of the present invention.

[0037] Figure 3 It is a schematic diagram of a processing box of the present invention.

[0038] Figure 4 It is a schematic diagram of the interior of the sulfuric acid absorption tower of the present invention.

[0039] Figure 5 It is a cross-sectional view of the sulfuric acid absorption tower of the present invention.

[0040] Figure 6 It is a schematic diagram of a concentration crystallizer of the present invention.

[0041] Numbers in the figure: 1, desulfurization tower; 2, desulfurization liquid circulation pump; 3, silicon slag filter; 4, concentration crystallizer; 401, drum; 402, rotating rod; 403, stirring rod; 404, motor; 405, heat conduction ring plate; 406, heater; 407, protective cover; 408, electric valve; 5, centrifuge; 6, rotary kiln; 7, sulfuric acid absorption tower; 701, treatment box; 702, filter plate; 703, vertical plate; 7 04, recovery box; 705, first transfer pipe; 706, second transfer pipe; 707, solution placement area; 708, third transfer pipe; 709, water pump; 710, fourth transfer pipe; 711, fifth transfer pipe; 712, water pipe; 713, nozzle; 714, buffer plate; 715, demisting plate; 716, exhaust pipe; 8, sulfuric acid absorption circulation pump; 9, long board; 901, spring; 902, damper; 903, vertical cylinder. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0043] Reference Figure 1-Figure 6 , a method and system for producing iron concentrate and sulfuric acid by desulfurizing limonite flue gas, the method comprising the following steps:

[0044] A. The raw material limonite solution and flue gas enter the desulfurization tower (1), in which sulfur dioxide reacts with iron oxide in the limonite to form ferrous sulfite, which is further oxidized to form ferric sulfate;

[0045] B. The ferric sulfate solution enters the silicon slag filter (3) through the desulfurization liquid circulation pump (2) for filtration, the filter cake obtained by filtration is silicon slag, and the filtrate obtained by filtration is the ferric sulfate solution;

[0046] C. the ferric sulfate solution enters the concentrating crystallizer (4), where the ferric sulfate solution is concentrated and crystallized to obtain a ferric sulfate solid-liquid mixed solution;

[0047] D. The ferric sulfate solid-liquid mixture enters the centrifuge (5) for separation, the separated solid is ferric sulfate crystals, and the separated liquid is the mother liquor which is returned to the concentrating crystallizer;

[0048] E. Ferrous sulfate crystals enter the rotary kiln (6), the pulverized coal is burned by the burner to provide heat for the rotary kiln, and the cold air is exchanged with the iron concentrate discharged from the rotary kiln in the cooler to recover heat before entering the burner to assist combustion. Ferrous sulfate is decomposed by heat in the rotary kiln to produce ferric oxide (iron concentrate) and sulfur trioxide flue gas;

[0049] F. Sulfur trioxide flue gas enters the sulfuric acid absorption tower (7), and sulfuric acid enters the sulfuric acid absorption tower (7) through the sulfuric acid absorption circulation pump (8). In the sulfuric acid absorption tower (7), sulfuric acid absorbs sulfur trioxide gas to generate sulfuric acid, and the product sulfuric acid is transported out of the system through the sulfuric acid absorption circulation pump (8).

[0050] The raw material of step A, limonite, contains 20-40% Fe and 20-40% SiO 2 40-50%, limonite solution concentration 20-40%, raw materials can be limonite, sulfuric acid slag, medium and low grade iron ore, steel slag and other iron-containing materials. Boiler flue gas temperature 130℃~150℃, liquid-gas ratio 1:1000; the operating conditions of the rotary kiln in step E: decomposition temperature 900~950℃, reaction time 1 hour, decomposition reaction atmosphere is oxidizing atmosphere, and the oxygen content of the kiln gas is ≥2~4%. The control process conditions of the sulfuric acid absorption tower: temperature 60℃~80℃, liquid-gas ratio 1:500.

[0051] Desulfurization mechanism: Iron oxide reacts chemically with sulfur dioxide in flue gas to generate ferrous sulfite, which is further oxidized to obtain ferric sulfate. The main reactions are:

[0052] Fe 2 O 3 +3SO 2 →Fe 2 (SO 3 )3

[0053] Fe 2 (SO 3 ) 3 +1.5O 2 →Fe 2 (SO 4 ) 3

[0054] High temperature decomposition mechanism: Ferrous sulfate enters the rotary kiln for high temperature calcination, controlling the temperature at 900-950°C for 60 minutes with an excess of 5% air. The reactions involved are:

[0055] Fe 2 (SO 4 ) 3 →Fe 2 O 3 +3SO 3

[0056] Sulfuric acid absorption mechanism: Sulfuric acid is produced by absorbing sulfur trioxide with sulfuric acid, and the absorption temperature and concentration are controlled by heat exchange to produce qualified sulfuric acid products. The main reactions involved are:

[0057] SO 3 +H 2 O→H 2 SO 4

[0058] like Figure 1 The desulfurization tower 1, the desulfurization liquid circulation pump 2, the silicon slag filter 3, the concentration crystallizer 4, the centrifuge 5, the rotary kiln 6, the sulfuric acid absorption tower 7 and the sulfuric acid absorption circulation pump 8 are connected in sequence through pipelines. The silicon slag filter 3 is used to filter the desulfurization slurry to obtain the silicon slag filter cake and the ferric sulfate filtrate; the concentration crystallizer 4 is used to concentrate the ferric sulfate solution and crystallize the ferric sulfate; the centrifuge 5 is used to separate the sulfuric acid Iron crystals and ferric sulfate mother liquor; a rotary kiln 6, used for oxidative decomposition of ferric sulfate to produce iron concentrate and sulfur trioxide flue gas; a sulfuric acid absorption tower 7, used for sulfuric acid to absorb sulfur trioxide in the flue gas to produce sulfuric acid; a sulfuric acid absorption circulating pump 8, one side of the sulfuric acid absorption tower 7 is connected to a treatment box 701, the inside of the treatment box 701 is connected to a filter plate 702, which is used to treat and reduce dust on the sulfur trioxide gas, the inside of the sulfuric acid absorption tower 7 is provided with a double-layer spray structure, and the lower end of the sulfuric acid absorption tower 7 is connected to a circulating spray structure.

[0059] Reference Figure 2 The lower end of the sulfuric acid absorption tower 7 is connected to a long plate 9, and the four corners of the lower end of the long plate 9 are connected to springs 901. A damper 902 is arranged inside the spring 901, and a vertical cylinder 903 is connected to the lower end of the spring 901. The device is supported by the long plate 9, and the spring 901 and the damper 902 below are used to make the device more stable.

[0060] Reference Figure 3 A vertical plate 703 is connected to the bottom of the treatment box 701, and a recovery box 704 is connected to the lower end of the treatment box 701. A first transfer pipe 705 is connected to the upper end of one side of the treatment box 701, and a second transfer pipe 706 is connected to the other side of the first transfer pipe 705. One end of the second transfer pipe 706 is connected to the sulfuric acid absorption tower 7. Before the sulfur trioxide flue gas is discharged to the sulfuric acid absorption tower 7, it first enters the treatment box 701 through the first transfer pipe 705 to cooperate with the internal filter plate 702 for dust reduction treatment, and then is discharged to the sulfuric acid absorption tower 7 through the second transfer pipe 706.

[0061] Reference Figure 4 , Figure 5A solution placement area 707 is provided at the lower end of the sulfuric acid absorption tower 7. Two third transfer pipes 708 are connected to the outer side of the sulfuric acid absorption tower 7 near the solution placement area 707. One end of each of the two third transfer pipes 708 is connected to a water pump 709. One end of the water pump 709 is connected to a fourth transfer pipe 710. One end of each of the fourth transfer pipes 710 is connected to a fifth transfer pipe 711 through a flange ring. The other side of the fifth transfer pipe 711 is connected to a plurality of water pipes 712 at equal intervals. The water pipe 71 A plurality of nozzles 713 are connected to the lower end of the sulfuric acid absorption tower 7, a buffer plate 714 is arranged below the nozzle 713, and a plurality of through holes are provided on the buffer plate 714. A demister plate 715 is connected to the upper end of the sulfuric acid absorption tower 7, and an exhaust pipe 716 is connected to the middle of the upper end of the sulfuric acid absorption tower 7. After the sulfur trioxide flue gas is discharged to the sulfuric acid absorption tower 7, the flue gas is sprayed by the nozzle 713, and the flue gas is blocked by the buffer plate 714 below, so that the flue gas is fully contacted with the treatment solution to react.

[0062] refer to Figure 6 A concentrator crystallizer 4 and a centrifuge 5 are arranged between the silicon slag filter 3 and the rotary kiln 6. The mother liquor separated by the centrifuge 5 is returned to the concentrator crystallizer 4 through a pipeline (reference Figure 1 ), the concentration crystallizer 4 includes a barrel 401, a rotating rod 402 is connected to the inside of the barrel 401, and two stirring rods 403 are respectively arranged on the upper and lower sides of the rotating rod 402, a motor 404 is connected to the upper end of the rotating rod 402, a heat-conducting ring plate 405 is connected to the outer wall of the barrel 401, and a plurality of heaters 406 are connected at equal intervals inside the heat-conducting ring plate 405, a protective cover 407 is arranged on the outside of the barrel 401, and an electric valve 408 is connected to the lower end of the barrel 401, the heater 406 is started for heating, and the heat is transferred to the inside of the barrel 401 through the heat-conducting ring plate 405, and the stirring rod 403 is driven to rotate by the rotation of the rotating rod 402 to stir the iron sulfate solution in the barrel 401, and the heat transferred by the heat-conducting ring plate 405 is continuously evaporated to produce crystals, and the crystallized part is transmitted to the centrifuge 5 by controlling the switch of the electric valve 408, so as to realize the key concentrated crystallization, realize the flow of iron sulfate into the rotary kiln, and achieve the output of iron concentrate.

[0063] Working principle or reaction process: raw material limonite solution and flue gas enter the desulfurization tower 1, in the desulfurization tower 1, sulfur dioxide reacts with iron oxide in limonite to generate ferrous sulfite, and ferrous sulfite further oxidizes to generate ferric sulfate, and the ferric sulfate solution enters the silicon slag filter 3 through the desulfurization liquid circulation pump 2 for filtration, the filter cake obtained by filtration is silicon slag, and the filtrate obtained by filtration is ferric sulfate solution, and the ferric sulfate solution enters the concentration crystallizer 4, and the ferric sulfate solution in the concentration crystallizer 4 is concentrated and crystallized to obtain a ferric sulfate solid-liquid mixture; the ferric sulfate solid-liquid mixture enters the centrifuge 5 for separation, the separated solid is ferric sulfate crystals, and the separated liquid is the mother liquor returned to the concentration crystallizer 4; the ferric sulfate crystals enter the rotary kiln 6, and the pulverized coal is burned by the burner to provide heat for the rotary kiln 6, and the cold air enters the burner for combustion after heat exchange with the iron concentrate discharged from the rotary kiln 6 in the cooler to recover heat, and the ferric sulfate in the rotary kiln 6 is thermally decomposed to produce iron trioxide iron concentrate and sulfur trioxide flue gas; the sulfur trioxide flue gas enters the sulfuric acid absorption tower 7;

[0064] The flue gas enters the treatment box 701 and the filter plate 702 through the first transfer pipe 705 for pretreatment. After the flue gas is subjected to dust reduction treatment, it is discharged from the second transfer pipe 706 to the inside of the sulfuric acid absorption tower 7. The water pump 709 is started according to the amount of flue gas to guide the treatment solution in the solution placement area 707 to the fifth transfer pipe 711 through the fourth transfer pipe 710. The fifth transfer pipe 711 discharges the solution to the water pipe 712 for spraying through the nozzle 713. The buffer plate 714 below cooperates to make the flue gas and the treatment solution fully contact and react chemically to generate sulfuric acid. The sulfuric acid product is transported out of the system through the sulfuric acid absorption circulation pump 8, and its sulfur trioxide flue gas enters the sulfuric acid absorption tower 7 to reach the key output of sulfuric acid.

[0065] Embodiment 1

[0066] according to Figure 1 The process flow shown requires that the raw material limonite is Fe 30% SiO 2 50%, limonite solution concentration 30%, control limonite solution 100kg / h.

[0067] Desulfurization tower control: boiler flue gas temperature 130℃~150℃, liquid-gas ratio 1:1000.

[0068] Control the ferrous sulfate to 100kg / h, the rotary kiln calcination temperature to 930℃, the calcination time to 1 hour, and the oxygen content in the flue gas to 3%;

[0069] Sulfuric acid absorption tower control: absorption liquid sulfuric acid concentration 98%, temperature 60°C, liquid-gas ratio 1:500.

[0070] According to the above process operation, the final analysis results are as follows:

[0071] Iron concentrate: iron content 68.1%

[0072] Sulfuric acid: H 2 SO 4 98.1%.

[0073] Desulfurization tower: desulfurization efficiency is 93.6%, and the sulfur content of desulfurized tail gas is 45mg / M3.

[0074] Embodiment 2

[0075] according to Figure 1 The process flow shown requires that the raw material limonite is Fe 35% SiO 2 45%, limonite solution concentration 35%, control limonite solution 100kg / h.

[0076] Desulfurization tower control: boiler flue gas temperature 130℃~150℃, liquid-gas ratio 1:1000.

[0077] Control the ferrous sulfate to 100kg / h, the rotary kiln calcination temperature to 950℃, the calcination time to 1 hour, and the oxygen content in the flue gas to 3%;

[0078] Sulfuric acid absorption tower control: absorption liquid sulfuric acid concentration 98%, temperature 65°C, liquid-gas ratio 1:500.

[0079] According to the above process operation, the final analysis results are as follows:

[0080] Iron concentrate: iron content 67.2%

[0081] Sulfuric acid: H 2 SO 4 98.3%.

[0082] Desulfurization tower: desulfurization efficiency is 92.8%, and the sulfur content of desulfurized tail gas is 46mg / M3.

[0083] Embodiment 3

[0084] according to Figure 1 The process flow shown requires that the raw material limonite is Fe 35% SiO 2 45%, limonite solution concentration 35%, control limonite solution 200kg / h.

[0085] Desulfurization tower control: boiler flue gas temperature 130℃~150℃, liquid-gas ratio 1:1000.

[0086] Control the ferrous sulfate to 200kg / h, the rotary kiln calcination temperature to 950℃, the calcination time to 1 hour, and the oxygen content in the flue gas to 3%;

[0087] Sulfuric acid absorption tower control: absorption liquid sulfuric acid concentration 98%, temperature 60°C, liquid-gas ratio 1:500.

[0088] According to the above process operation, the final analysis results are as follows:

[0089] Iron concentrate: iron content 66.8%

[0090] Sulfuric acid: H 2 SO 4 98.4%.

[0091] Desulfurization tower: desulfurization efficiency is 91.9%, and the sulfur content of desulfurized tail gas is 43mg / M3.

[0092] The above embodiment can fully realize the desulfurization of limonite flue gas to produce iron concentrate and sulfuric acid, and the obtained iron concentrate has high iron content, high sulfuric acid concentration and good desulfurization efficiency.

[0093] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for producing iron concentrate and sulfuric acid by desulfurization of limonite flue gas, characterized in that: The method comprises the following steps: raw material limonite solution and flue gas enter a desulfurization tower (1) to react and generate ferrous sulfite, and the ferrous sulfite is further oxidized to generate ferrous sulfate; the ferric sulfate solution enters a silicon slag filter (3) through a desulfurization liquid circulation pump (2) to be filtered, the filter cake obtained by filtration is silicon slag, and the filtrate obtained by filtration is a ferrous sulfate solution; The ferric sulfate solution enters the concentrating crystallizer (4), where the ferric sulfate solution is concentrated and crystallized to obtain a ferric sulfate solid-liquid mixed solution; the ferric sulfate solid-liquid mixed solution enters the centrifuge (5) for separation, where the separated solid is ferric sulfate crystals, and the separated liquid is the mother liquor that is returned to the concentrating crystallizer; Ferrous sulfate crystals enter the rotary kiln (6), coal powder is burned by the burner to provide heat for the rotary kiln, cold air is exchanged with the iron concentrate discharged from the rotary kiln in the cooler to recover heat and then enters the burner to assist combustion, and the ferrous sulfate is decomposed by heat in the rotary kiln to produce ferric oxide (iron concentrate) and sulfur trioxide flue gas; the sulfur trioxide flue gas enters the sulfuric acid absorption tower (7), sulfuric acid enters the sulfuric acid absorption tower (7) through the sulfuric acid absorption circulation pump (8), sulfuric acid absorbs sulfur trioxide gas in the sulfuric acid absorption tower (7) to generate sulfuric acid, and the product sulfuric acid is transported out of the system through the sulfuric acid absorption circulation pump (8).

2. The method for producing iron concentrate and sulfuric acid by desulfurization of limonite flue gas according to claim 1, characterized in that: The desulfurization tower (1), desulfurization liquid circulation pump (2), silicon slag filter (3), concentration crystallizer (4), centrifuge (5), rotary kiln (6), sulfuric acid absorption tower (7) and sulfuric acid absorption circulation pump (8) are connected in sequence.

3. The method for producing iron concentrate and sulfuric acid by desulfurization of limonite flue gas according to claim 1, characterized in that: The raw material limonite contains 20-40% Fe and 40-50% SiO2, the concentration of the limonite solution is 20-40%, the flue gas temperature in the desulfurization tower (1) is 130°C-150°C, and the liquid-gas ratio is 1:1000.

4. The method for producing iron concentrate and sulfuric acid by desulfurization of limonite flue gas according to claim 1, characterized in that: The rotary kiln operating conditions are as follows: decomposition temperature of 900-950° C., reaction time of 1 hour, decomposition reaction atmosphere of oxidizing atmosphere, and oxygen content of kiln outlet gas of ≥2-4%.

5. The method for producing iron concentrate and sulfuric acid by desulfurization of limonite flue gas according to claim 1, characterized in that: The control process conditions of the sulfuric acid absorption tower are: temperature 60°C to 80°C, liquid-gas ratio 1:

500.

6. The method for producing iron concentrate and sulfuric acid by desulfurization of limonite flue gas according to claim 2, characterized in that: The desulfurization liquid circulation pump (2) is used for conveying the desulfurization liquid; the silicon slag filter (3) is used for filtering the desulfurization slurry to obtain silicon slag filter cake and iron sulfate filtrate; the concentration crystallizer (4) is used for concentrating the iron sulfate solution and crystallizing the iron sulfate; the centrifuge (5) is used for separating the iron sulfate crystals and the iron sulfate mother liquor; the rotary kiln (6) is used for oxidizing and decomposing the iron sulfate to produce iron concentrate and sulfur trioxide flue gas; the sulfuric acid absorption tower (7) is used for sulfuric acid to absorb sulfur trioxide in the flue gas to produce sulfuric acid; the sulfuric acid absorption circulation pump (8) is used for pressurized conveying of sulfuric acid.

7. The method for producing iron concentrate and sulfuric acid by desulfurization of limonite flue gas according to claim 6, characterized in that: The concentrating crystallizer (4) comprises a barrel (401), the barrel (401) is internally connected to a rotating rod (402), and two stirring rods (403) are respectively arranged on the upper and lower sides of the rotating rod (402), the upper end of the rotating rod (402) is connected to a motor (404), the outer wall of the barrel (401) is connected to a heat-conducting ring plate (405), and a plurality of heaters (406) are connected at equal intervals inside the heat-conducting ring plate (405), the outer side of the barrel (401) is provided with a protective cover (407), and the lower end of the barrel (401) is connected to an electric valve (408).

8. The method for producing iron concentrate and sulfuric acid by desulfurization of limonite flue gas according to claim 7, characterized in that: The sulfuric acid absorption tower (7) is connected to a treatment box (701) on one side, and a filter plate (702) is connected inside the treatment box (701) for treating and reducing dust on sulfur trioxide gas. A double-layer spray structure is arranged inside the sulfuric acid absorption tower (7), and a circulating spray structure is connected to one side of the lower end of the sulfuric acid absorption tower (7). The lower end of the sulfuric acid absorption tower (7) is connected to a long plate (9), and the four corners of the lower end of the long plate (9) are connected to springs (901), and the springs (901) are provided with a plurality of filters. A damper (902) is provided at the bottom of the spring (901), and the lower end of the spring (901) is connected to a vertical cylinder (903), a vertical plate (703) is connected below the treatment box (701), and a recovery box (704) is connected to the lower end of the treatment box (701), a first transfer pipe (705) is connected to the upper end of one side of the treatment box (701), and the other side of the first transfer pipe (705) is connected to a second transfer pipe (706), and one end of the second transfer pipe (706) is connected to the sulfuric acid absorption tower (7).

9. The method for producing iron concentrate and sulfuric acid by desulfurization of limonite flue gas according to claim 8, characterized in that: A solution placement area (707) is provided at the lower end of the sulfuric acid absorption tower (7). Two third transfer pipes (708) are connected to one end of the outside of the sulfuric acid absorption tower (7) near the solution placement area (707). One end of each of the two third transfer pipes (708) is connected to a water pump (709), and one end of the water pump (709) is connected to a fourth transfer pipe (710). One end of each of the fourth transfer pipes (710) is connected to a fifth transfer pipe (711) via a flange ring, and the other side of the fifth transfer pipe (711) is connected to a plurality of water pipes (712) at equal intervals. The lower end of the water pipe (712) is connected to a plurality of nozzles (713), and buffer plates (714) are arranged at intervals below the nozzles (713), and the buffer plates (714) are provided with a plurality of through holes. A demisting plate (715) is connected to the upper end of the sulfuric acid absorption tower (7), and an exhaust pipe (716) is connected to the middle of the upper end of the sulfuric acid absorption tower (7).

10. A system for producing iron concentrate and sulfuric acid by desulfurization of limonite flue gas, characterized in that: A structural connection formed by using the method according to any one of claims 1 to 9.

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