Granular calcium-based waste desulfurizer recycling system and method

Abstract

The invention relates to a granular calcium-based waste desulfurizer recycling system which comprises a waste desulfurizer treatment system, a uniform mixing and granulating system, a material distribution system, an ignition sintering system, a large flue, an oxidant injection system and a desulfurization system, the waste desulfurizing agent treatment system comprises a waste desulfurizing agent bin, a disc feeder and a coke powder bin, a double-roller crusher is arranged below the coke powder bin, then a four-roller crusher is connected below the coke powder bin, and a water spraying device is mounted at an outlet of the four-roller crusher; the crushed waste desulfurizer and coke powder enter a raw material conveying system; raw materials are conveyed to the uniform mixing and granulating system through a conveying belt, the uniform mixing and granulating system comprises a cylinder mixer and a cylinder granulator, and the mixed raw materials enter the ignition sintering system through the material distribution system; waste gas generated by sintering is discharged into a large flue, an oxidizing agent injection system is installed on the large flue, and sintering flue gas passing through the oxidizing agent injection system enters a desulfurization system. According to the method, the waste desulfurizer can be treated, and the sinter cost can be reduced.

Description

Technical Field

[0001] The present invention relates to a method for recycling calcium-based waste desulfurizer. By mixing the waste desulfurizer with coke powder and entering the sintering process, the problem of difficult treatment of waste desulfurizer is solved, belonging to the field of environmental protection technology in iron and steel metallurgy. Background Art

[0002] The atmospheric pollutants emitted by iron and steel enterprises generally include SO2, NOx, dust, etc. According to the national requirements for ultra-low emissions of iron and steel enterprises, the sintering, coking, and blast furnace processes of iron and steel enterprises must carry out the treatment of atmospheric pollutants and meet the requirements of ultra-low emission concentrations of pollutants. For example, the hot blast stove of the blast furnace requires SO2 to be less than 50 mg / m 3 、the sintering flue gas requires SO2 to be less than 35 mg / m 3 、NOx to be less than 50 mg / m 3 etc.

[0003] The existing flue gas desulfurization and denitrification methods mainly include calcium method, activated carbon method, ammonia method, etc. Among them, the calcium method is widely used due to its high desulfurization efficiency and low operating cost. The mainstream calcium method is to spray hydrated lime for desulfurization in the circulating fluidized bed method. In recent years, the desulfurization method of forming fixed beds by solidifying active hydrated lime into particles of a certain size and shape and filling them into the desulfurization tower has also been applied to a certain extent.

[0004] Regardless of which calcium method is used for desulfurization, the formed desulfurization products are all desulfurization products containing calcium sulfite and calcium sulfate. Due to the instability of calcium sulfite, its treatment has always been a difficult problem. At present, the main feasible treatment process is to add a small amount of powder-type desulfurization ash to the cement production process (generally less than 2%), and slowly digest it, but the harm to buildings is always a hidden danger; other methods such as in-situ burial are no longer allowed by the state. Granular desulfurization waste has emerged in recent years and contains certain components of silicon dioxide and magnesium oxide. It cannot be simply treated according to the treatment method of powder-type desulfurization ash. Iron and steel enterprises generally entrust others to dispose of and recycle it, and the disposal cost is 150-300 yuan / t, which further increases the environmental protection operation cost. Therefore, there is an urgent need for a new solution to solve the above technical problems.

[0005] The sintering process is a process of forming ore at high temperature, and some calcium-containing fluxes are required to form calcium ferrite liquid phase to make the sintered ore have a certain strength. When different desulfurization processes are used for flue gas at different locations in a steel plant, such as using granular calcium-based desulfurizer for hot blast stove desulfurization and using circulating fluidized bed desulfurization for sintering, in this case, two different disposal methods are required for the two desulfurization products. How to simply and efficiently treat granular calcium-based desulfurizer is a difficult problem.

[0006] Patent literature retrieval was conducted on the disposal method and reuse method of granular calcium-based waste desulfurizer. Using granular desulfurizer as the retrieval keyword, the patents retrieved were mainly about its production methods; using sintering and desulfurization ash as keywords, the retrieval results were mostly about the utilization methods such as using desulfurization ash as raw materials for cement and building materials. There is no patent on the combined treatment of granular desulfurization waste and the sintering process. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a reuse system for granular calcium-based waste desulfurizer, aiming to dispose of the granular calcium-based waste desulfurizer generated in other processes through the steel plant sintering process. The granular calcium-based desulfurizer and coke powder are mixed and crushed under certain conditions to meet the requirements of sintering materials, and part of the sintering flux is replaced to enter the sintering process, thereby eliminating the waste.

[0008] To achieve the above object, the technical solution of the present invention is as follows. A reuse system for granular calcium-based waste desulfurizer includes a waste desulfurizer treatment system, a raw material transportation system, a mixing and granulation system, a feeding system, an ignition and sintering system, a main flue, an oxidant injection system, and a desulfurization system. The characteristics are that the waste desulfurizer treatment system includes a waste desulfurizer bin, a disk feeder, a coke powder bin, a pair-roll crusher is arranged under the coke powder bin, a four-roll crusher is connected under the pair-roll crusher, and a water spraying device is installed at the outlet of the four-roll crusher; the crushed waste desulfurizer and coke powder enter the raw material transportation system; the raw materials are transported to the mixing and granulation system through a conveyor belt. The mixing and granulation system includes a rotary mixer and a rotary granulator. The mixed raw materials enter the ignition and sintering system through the feeding system; the waste gas generated after sintering is discharged into the main flue, and an oxidant injection system is installed on the main flue. The oxidant injection system includes an ozone generator and a spray gun, and a nozzle is connected to the spray gun. The sintering flue gas passing through the oxidant injection system enters the desulfurization system.

[0009] Further, the waste desulfurizer refers to the waste after fixed-bed calcium-based desulfurization, and the main chemical component ranges are CaCO3: 30-50 wt%, Ca(OH)2: 10-25 wt%, CaSO3: 0-10 wt%, CaSO4: 10-20 wt%, SiO2: 1-4.5 wt%, MgO: 0.5-2.5 wt%. The shape is a columnar body, and the particle size is 5-40 mm.

[0010] Further, when the waste desulfurizer enters the sintering process, the feeding amount is 0.5-3 t / h. When adding the waste desulfurizer, the amount of limestone used in sintering is reduced. For every 1 t of waste desulfurizer added, the amount of limestone used is reduced by 0.5-1 t to maintain the alkalinity stability of the sintered ore.

[0011] Further, both the double-roll crusher and the four-roll crusher are jaw crushers. The roll spacing of the double-roll crusher is 5 mm, and the roll spacing of the four-roll crusher is 3 mm.

[0012] Further, the water spraying device is a quarter-inch water pipe made of 304 stainless steel. A stainless steel ball valve is installed on the water pipe to control the water flow rate at 0.5 - 0.8 t / h. The end of the water pipe is connected to a straight-section quarter-inch stainless steel water pipe made of 304 stainless steel with a length of 300 mm, and 5 stainless steel conical atomizing nozzles are evenly connected to it.

[0013] Further, an oxidant injection system is connected at the large flue. The purpose is to oxidize SO2 in the flue gas to prevent the SO2 concentration from being too high and exceeding the treatment capacity of the desulfurization system. The oxidant used is ozone, which is provided by an ozone generator. The power of the ozone generator is 450 - 600 kw, and the ozone production is 80 - 120 kg / h. There are 4 spray guns, which are respectively connected to both sides of the large flue and are made of 316L stainless steel. 316L stainless steel spiral nozzles are connected to the spray guns.

[0014] Further, the desulfurization system is the circulating fluidized bed desulfurization method, and the desulfurizer used is quicklime.

[0015] A method for treating granular calcium-based waste desulfurizer using the above system includes the following steps:

[0016] (1) The waste desulfurizer enters the waste desulfurizer silo and is discharged through a disk feeder. It enters the double-roll crusher for rough crushing together with the coke from the coke powder silo. The mixture coming out of the double-roll crusher enters the four-roll crusher for fine crushing. When the waste desulfurizer enters the sintering process, the original limestone used in sintering reduces the dosage according to the addition amount and composition of the waste desulfurizer.

[0017] (2) Start the water spraying device at the outlet of the four-roll crusher to atomize and spray water on the mixture, so that the crushed waste desulfurizer is wetted and adheres to the coke powder. When the water spraying device sprays water, the water spraying amount of the water adding device on the cylindrical mixer decreases, and the reduced water amount is the same as that of the water spraying device.

[0018] (3) Through the transportation system, the crushed coke powder and waste desulfurizer enter the sintering blending and granulating system, and are fully blended and granulated in the cylindrical mixer and the cylindrical granulator.

[0019] (4) The raw materials after mixing and granulating enter the ignition sintering system through the sintering feeding system.

[0020] (5) After the ignition sintering starts, the ozone generator on the large flue starts, and ozone is sprayed into the large flue through the spray gun. Through the strong oxidation of ozone, SO2 is oxidized to SO3. The oxidized sintering flue gas enters the desulfurization system. The increase of SO3 is more conducive to reacting with Ca(OH)2 to form calcium sulfate, which is thus absorbed by the sintering desulfurization system.

[0021] In the present invention, the waste desulfurizer bin, coke powder bin, disc feeder, double-roll crusher, four-roll crusher, conveyor belt, cylindrical mixer, cylindrical pelletizer, feeding system, ignition and sintering system, main flue, and ozone generator are all common equipment used in sintering.

[0022] The beneficial effects of the present invention are as follows: Using the granular desulfurizer waste from other processes of iron and steel to replace the limestone flux used in sintering can not only dispose of the desulfurizer solid waste but also reduce the cost of sintering flux.

[0023] The present invention has the following positive effects compared with the prior art:

[0024] (1) Without major modifications to the original sintering process, only the granular calcium-based waste desulfurizer raw material needs to be processed to meet the requirements of the sintering flux and then enter the original sintering process, with relatively low investment;

[0025] (2) The calcium hydroxide contained in the waste desulfurizer has good digestion effect and certain viscosity, which is beneficial to improving the pelletizing effect during sintering when combined with iron ore powder;

[0026] (3) The waste desulfurizer is mixed and crushed with coke powder, and the calcium-based compounds it contains have a catalytic combustion effect, which is beneficial to the full combustion of sintering coke powder;

[0027] (4) The waste desulfurizer is mixed with coke powder and water is added, so that the calcium-based compounds fill the pores of the coke powder. During the sintering process, calcium ferrite phase is easily formed with the surrounding iron ore powder. Calcium ferrite has a catalytic effect, causing the reduction reaction of CO and NO generated by the local combustion of coke powder: 2CO + 2NO → 2CO2 + N2, which is beneficial to the reduction of nitrogen oxides in sintering flue gas and can also reduce the operation cost of denitrification of sintering flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 : Flow chart of waste desulfurizer reuse;

[0029] Figure 2 : Structure diagram of water addition device;

[0030] Figure 3 : Oxidant injection system diagram.

[0031] In the figure: 1 - straight section water pipe; 2 - conical atomizing nozzle; 3 - ball valve; 4 - quarter water pipe; 5 - oxidant spray gun; 6 - main flue; 7 - spiral nozzle; 8 - ozone generator. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] In order to deepen the understanding of the present invention, the following detailed description is made in conjunction with the accompanying drawings for this embodiment.

[0033] Example 1:

[0034] Taking a steel plant as an example, the area of the sintering trolley is 198m 2 , referring to Figure 1 , during the normal production of the sintering process, the coke powder from the coke powder silo first enters the double-roll crusher for coarse crushing, and then enters the four-roll crusher for fine crushing. The crushed coke powder is transported by belt to the cylindrical mixer and the cylindrical granulator for mixing and granulation. The mixture is distributed onto the sintering machine through the feeding system, and sintered through the ignition sintering system. The generated flue gas enters the circulating fluidized bed desulfurization system through the main flue for desulfurization.

[0035] Example 2

[0036] Taking a steel plant as an example, the area of the sintering trolley is 198m 2 , the volume of the blast furnace is 1280m 3 , the hot blast stove adopts the SDS calcium-based method for desulfurization. The desulfurization product is a calcium-based waste gas desulfurizer with a size of 5 - 25mm, in the shape of a cylinder. The monthly output of the waste desulfurizer is 200t, and the outsourcing disposal cost is 200 yuan / t. Now, the desulfurization waste of the blast furnace hot blast stove is centrally treated through the sintering process.

[0037] First, the composition of the granular calcium-based waste desulfurizer is detected, and the results are as follows:

[0038] Table 1 Main chemical components of the granular calcium-based waste desulfurizer

[0039] Component CaO <![CDATA[SiO2]]> MgO <![CDATA[Ca(OH)2]]> <![CDATA[CaCO3]]> <![CDATA[Calcium sulfite]]> <![CDATA[CaSO4]]> Content, % 54.45 3.05 1.13 19.55 48.50 2.05 14.28

[0040] According to this chemical composition, the substitution ratio of limestone is determined to be 1:1, and the addition amount of the waste desulfurizer is 2.5t / h.

[0041] See Figure 1 , Figure 2 and Figure 3 , a method for recycling granular calcium-based waste desulfurizer, including a waste desulfurizer treatment system, a raw material transportation system, a mixing and granulation system, a feeding system, an ignition sintering system, a main flue 6, an oxidant injection system, and a desulfurization system; the waste desulfurizer treatment system includes a waste desulfurizer silo, a disc feeder, a coke powder silo, a double-roll crusher is arranged under the coke powder silo, a four-roll crusher is connected under the double-roll crusher, and a water spraying device is installed at the outlet of the four-roll crusher; the crushed waste desulfurizer and coke powder enter the raw material transportation system; the raw material is transported to the mixing and granulation system through a conveyor belt, the mixing and granulation system includes a cylindrical mixer and a cylindrical granulator, and the mixed raw material enters the ignition sintering system through the feeding system; the exhaust gas generated after sintering is discharged into the main flue 6, an oxidant injection system is installed on the main flue 6, the oxidant injection system includes an ozone generator 8 and a spray gun 5, a nozzle 7 is connected to the spray gun, and the sintering flue gas passing through the oxidant injection system enters the desulfurization system.

[0042] The method for treating granular calcium-based waste desulfurizer using the above system includes the following steps:

[0043] (1) 200 t of waste desulfurizer enters the waste desulfurizer bin at one time, and is discharged through a disc feeder at a feeding speed of 2.5 t / h. The coke flow rate from the coke bin is 9.9 t / h, and they enter the double-roll crusher for coarse crushing together. The mixture coming out of the double-roll crusher enters the four-roll crusher for fine crushing; after crushing, the proportion of waste desulfurizer with a particle size less than 3 mm is greater than 85%. When 2.5 t / h of waste desulfurizer enters the sintering process, the original limestone used in sintering is reduced by 2.5 t / h;

[0044] (2) Start the water spraying device at the four-roll crusher inlet. Two of the five conical atomizing nozzles spray atomized water on the mixture at a water spraying rate of 0.7 t / h, so that the crushed waste desulfurizer is wetted and adheres to the coke powder; when the water spraying device sprays water, the water spraying rate of the water adding device on the rotary drum mixer is reduced by 0.7 t / h;

[0045] (3) Through the transportation system, the crushed coke powder and waste desulfurizer enter the sintering blending and granulation system, and are fully blended and granulated in the rotary drum mixer and the rotary drum granulator;

[0046] (4) The raw materials after mixing and granulation enter the ignition sintering system through the sintering feeding system;

[0047] (5) After the ignition sintering starts, the ozone generator 8 on the main flue 6 starts, and ozone is injected into the main flue 6 through the spray gun 7. Through the strong oxidation of ozone, SO2 is oxidized to SO3, and the oxidized sintering flue gas enters the desulfurization system and is absorbed.

[0048] After implementation, the chemical composition of the sinter is as shown in Table 2 below:

[0049] Table 2 Chemical composition of sinter, %

[0050]

[0051] Judging from the chemical composition, after treating the waste desulfurizer, there is no obvious change in the sinter, and it has no impact on the quality of the sinter.

[0052] The production change of the desulfurization system is as shown in Table 3 below:

[0053] Table 3 Production change of desulfurization system

[0054]

[0055] Judging from the production change of the desulfurization system, there is no obvious impact on the desulfurization process, and the inlet SO2 concentration rises by 66.2 mg / m 3 within the controllable range.

[0056] The substitution of limestone reduces the cost per ton of ore by 0.897 yuan, saves the disposal cost of waste desulfurizer by 1.888 yuan / t, the desulfurization cost per ton of ore increases by 0.36 yuan / t, and the total cost per ton of ore can be reduced by 2.425 yuan / t, which has great economic benefits.

[0057] It should be noted that the above embodiments are not used to limit the protection scope of the present invention, and equivalent transformations or substitutions made on the basis of the above technical solutions all fall within the protection scope of the claims of the present invention.

Claims

1. A particulate calcium-based waste desulfurizer reuse system, characterized in that, The system includes a spent desulfurizer treatment system, a raw material transportation system, a mixing and granulating system, a feeding system, an ignition and sintering system, a main flue, an oxidant injection system, and a desulfurization system. The spent desulfurizer treatment system includes a spent desulfurizer silo, a disc feeder, a coke powder silo. There is a pair-roll crusher under the coke powder silo. The pair-roll crusher is connected to a four-roll crusher. A water spraying device is installed at the outlet of the four-roll crusher. The crushed spent desulfurizer and coke powder enter the raw material transportation system. The raw materials are transported to the mixing and granulating system through a conveyor belt. The mixing and granulating system includes a rotary mixer and a rotary granulator. The mixed raw materials enter the ignition and sintering system through the feeding system. The waste gas generated after sintering is discharged into the main flue. An oxidant injection system is installed on the main flue. The oxidant injection system includes an ozone generator and a spray gun. A nozzle is connected to the spray gun. The sintering flue gas passing through the oxidant injection system enters the desulfurization system.

2. The granular calcium-based waste desulfurizer reuse system according to claim 1, wherein The spent desulfurizer refers to the waste after fixed-bed calcium-based desulfurization. The main chemical component ranges are as follows: CaCO3: 30 - 50 wt%, Ca(OH)2: 10 - 25 wt%, CaSO3: 0 - 10 wt%, CaSO4: 10 - 20 wt%, SiO2: 1 - 4.5 wt%, MgO: 0.5 - 2.5 wt%. The shape is a columnar body, and the particle size is 5 - 40 mm.

3. The particulate calcium-based waste desulfurizer reuse system according to claim 1, wherein When the spent desulfurizer enters sintering, the addition amount is 0.5 - 3 t / h. When adding the spent desulfurizer, the amount of limestone used in sintering is reduced simultaneously. For every 1 t of spent desulfurizer added, the amount of limestone used is reduced by 0.5 - 1 t to maintain the alkalinity stability of the sinter.

4. The particulate calcium-based waste desulfurizer reuse system according to claim 1, wherein, Both the pair-roll crusher and the four-roll crusher are jaw crushers. The roll spacing of the pair-roll crusher is 5 mm, and the roll spacing of the four-roll crusher is 3 mm.

5. The particulate calcium-based waste desulfurizer reuse system according to claim 1, characterized in that, The water spraying device is a quarter-inch water pipe made of 304 stainless steel. A stainless steel ball valve is installed on the water pipe to control the water flow rate at 0.5 - 0.8 t / h. The end of the water pipe is connected to a straight-section quarter-inch stainless steel water pipe made of 304 stainless steel with a length of 300 mm. Five stainless steel conical atomizing nozzles are evenly connected to it.

6. The particulate calcium-based waste desulfurizer reuse system according to claim 1, wherein The oxidant injection system is connected at the main flue. The purpose is to oxidize SO2 in the flue gas to prevent the SO2 concentration from being too high and exceeding the treatment capacity of the desulfurization system. The oxidant used is ozone provided by an ozone generator. The power of the ozone generator is 450 - 600 kw, and the ozone production amount is 80 - 120 kg / h. There are 4 spray guns, which are respectively connected to both sides of the main flue. The material is 316L stainless steel. A 316L stainless steel spiral nozzle is connected to the spray gun.

7. The particulate calcium-based waste desulfurizer reuse system according to claim 1, characterized in that The desulfurization system is the circulating fluidized bed desulfurization method, and the desulfurizer used is quicklime.

8. A method for reusing granular calcium-based waste desulfurizer, characterized in that Using the system described in any one of claims 1 - 7, the method includes the following steps: (1) The spent desulfurizer enters the spent desulfurizer silo, is discharged through the disc feeder, and enters the pair-roll crusher for rough crushing together with the coke from the coke powder silo. The mixture coming out of the pair-roll crusher enters the four-roll crusher for fine crushing. When the spent desulfurizer enters the sintering process, the amount of limestone originally used in sintering is reduced according to the addition amount and composition of the spent desulfurizer. (2) Start the water spraying device at the four-roll crusher inlet to atomize the water spray on the mixture, so that the crushed waste desulfurizer is wetted and adheres to the coke powder; when the water spraying device sprays water, the water spraying volume of the water adding device on the rotary mixer is reduced, and the reduced water volume is the same as that of the water spraying device; (3) Through the transportation system, the crushed coke powder and waste desulfurizer enter the sintering blending and granulating system, and are fully blended and granulated in the rotary mixer and rotary granulator; (4) The raw materials after mixing and granulation enter the ignition sintering system through the sintering feeding system; (5) After the ignition sintering starts, the ozone generator on the main flue is started, and ozone is injected into the main flue through the spray gun. Through the strong oxidation of ozone, SO2 is oxidized to SO3. The oxidized sintering flue gas enters the desulfurization system. The increase of SO3 is more likely to react with Ca(OH)2 to form calcium sulfate, which is then absorbed by the sintering desulfurization system.

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