A method for preparing calcium chrome sand

Abstract

A method for preparing calcium-chrome sand comprises the following steps: subjecting chromium-containing sludge to tempering, decomposition, roasting and other processes, ensuring that the Cr element is retained in the calcium-chrome sand in a non-toxic, non-volatile low-valent state, and preparing calcium-chrome sand with high added value; collecting sulfur-containing flue gas during the roasting process to prepare sulfuric acid, so that sulfate contained in the sludge is reduced and decomposed and used for acid production, thereby avoiding diffusion of sulfur element to form air pollution, achieving harmless treatment of chromium-containing sludge, and comprehensively utilizing chromium, calcium and sulfur elements in the chromium-containing sludge as resources, significantly reducing emission of hazardous solid wastes in related production processes, and reducing hazardous waste disposal costs; and the generated calcium-chrome sand can be used as a raw material for the production of stainless steel, chromium alloys, ceramics, colored glass, artificial stone, microcrystalline glass, coatings and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial hazardous solid waste treatment, and in particular relates to a method for preparing calcium chrome sand. Background Art

[0002] Chromium-containing sludge is a solid hazardous waste generated by industries such as steel and nonferrous metals. Its composition fluctuates greatly with the raw materials and production processes. For example, after the wastewater from the chromate passivation process of the cold rolling production unit of a steel enterprise is treated, a large amount of chromium-containing sludge will be produced, the main components of which are calcium sulfate, calcium sulfite and chromium compound precipitation. The carcinogenic heavy metal Cr in the sludge is easily soluble and the content reaches 0.5-20%, so it is included in the scope of hazardous waste. The moisture content of chromium-containing sludge after being pressed into cakes is generally 50%-60%. In addition, chromium-containing sludge also contains a small amount of Zn, Pt, F and other elements, which makes it impossible to recycle in metallurgical production, and cannot be directly used in the production of building materials such as glass, becoming a burden for steel and electroplating companies.

[0003] The Cr element contained in chromium-containing sludge is a high-value mineral resource and a scarce mineral in China. More than 80% of China's annual consumption relies on imports. Chromium is widely used. In the building materials industry, it can be used as a colorant for glass, ceramics, artificial stone, and coatings, and can also be used as a crystal nucleation agent for microcrystalline glass, etc. In the metallurgical industry, chromium is the main raw material for the production of stainless steel and chromium-containing alloys. Calcium oxide is the main component of many silicate building materials and an important metallurgical auxiliary material.

[0004] There are many technologies for treating chromium-containing sludge, including solidification and stabilization landfill, acid leaching, ammonia leaching, high-temperature alkaline roasting leaching, microbial method and other methods. Generally, the chromium element is enriched and then recovered, or the sludge is used as a small proportion of raw materials for cement, ceramics, etc. These technologies have problems such as high treatment cost, incomplete harmless treatment, large flue gas treatment volume, and secondary heavy metal pollution.

[0005] At present, chromium-containing sludge from steel, nonferrous metals and other enterprises is generally outsourced for disposal, which is costly. Environmentally friendly and resource-based disposal of chromium-containing sludge is a technical problem that needs to be solved urgently for related enterprises to achieve zero solid waste emissions. Summary of the invention

[0006] The purpose of the present invention is to provide a preparation method of calcium chrome sand, which takes chromium-containing sludge as a main raw material, enriches chromium in the chromium-containing sludge in a harmless low-valent state in residues to form calcium chrome sand, and simultaneously decomposes sulfur in the chromium-containing sludge during the treatment process and releases it for use in preparing sulfuric acid or sodium sulfite, thereby achieving harmless treatment and resource utilization of the chromium-containing sludge, turning the chromium-containing sludge into treasure, and the generated calcium chrome sand can be used as a raw material for the production of stainless steel, chromium alloy, ceramics, colored glass, artificial stone, microcrystalline glass, coatings, etc.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] A method for preparing calcium chrome sand comprises the following steps:

[0009] 1) Preparation of batch materials

[0010] The chromium-containing sludge and the conditioning material are uniformly mixed and granulated to form a chromium-containing sludge batch; the weight ratio of the conditioning material to the chromium-containing sludge is 1:0.5-50;

[0011] The tempering material components include SiO 2 :1-80%、Al 2 O 3 :1-30%、CaF 2 :0-1%、B 2 O 3 :0-2%、Na 2 O: 0.2-5%, K 2 O: 0.1-1%, P 2 O 5 :0.1-2%、Fe 2 O 3 :0.05-8%, C:10-83%;

[0012] 2) Drying

[0013] Drying the chromium-containing sludge and pellets at a temperature of 100 to 280°C;

[0014] 3) Calcination

[0015] The chromium-containing sludge batch material is roasted to form calcium chrome sand, the roasting temperature is 850-1180°C, and the roasting time is 30-180 minutes; sulfur-containing flue gas is collected during the roasting process;

[0016] 4) Cooling.

[0017] Preferably, in step 1), the batch material particle size D 50 0.5~10mm.

[0018] Preferably, in step 2), the drying time is 20 to 240 minutes.

[0019] Preferably, sulfuric acid is prepared from the sulfur-containing flue gas collected during the roasting process in step 3).

[0020] Preferably, in step 4), waste heat in the calcium chrome sand is recovered during the cooling process.

[0021] The melting temperature of the calcium chrome sand of the present invention is 950-1300°C.

[0022] Furthermore, calcium chrome sand is prepared in multiple batches according to the method, and the obtained calcium chrome sand is sent to corresponding silos for homogenization according to different chromium contents. Thereafter, the calcium chrome sand is taken out from different silos according to a preset ratio and mixed and homogenized to obtain calcium chrome sand with the required chromium content.

[0023] Preferably, the number of the silos is 3 to 10.

[0024] In the method of the present invention, after the chromium-containing sludge is mixed with the tempering material and tempered, in the subsequent roasting and cooling process, the reducing agent in the tempering material preferentially reacts with oxidizing substances such as oxygen in the environment, making the environment reductive, ensuring that the Cr element in the chromium-containing sludge is retained in the calcium chrome sand in a non-toxic, non-volatile low-valent state, and preparing high-value-added calcium chrome sand; at the same time, the flue gas generated by the decomposition of sulfate is collected during the roasting process and used to prepare sulfuric acid, avoiding the diffusion of sulfur elements to form atmospheric pollution. While achieving the harmless treatment of chromium-containing sludge, the method can comprehensively utilize the chromium, calcium and sulfur elements in the chromium-containing sludge, significantly reduce the emission of hazardous solid waste in related production processes, and reduce the cost of hazardous waste disposal.

[0025] Since Na is added to the conditioning material 2 O.K 2 O.B 2 O 3 The combination of low melting point flux and carbon reducing agent can significantly reduce the decomposition temperature of sulfate, so that the decomposition temperature of sulfate in chromium-containing sludge is reduced from more than 1400℃ to 800-1150℃, reducing equipment investment and energy consumption in the treatment process, thereby reducing production costs.

[0026] During the roasting process, the reducing agent C in the quenching and tempering material reacts with the O 2 and sulfate decomposition products in chromium-containing sludge O 2 The reaction generates CO, which in turn promotes the decomposition of sulfate, thereby completely decomposing the sulfate component in the chromium-containing sludge, and the escaped sulfur-containing gas is discharged in the form of flue gas. The use of sulfur-containing flue gas in the production of sulfuric acid allows it to be used reasonably, avoids the diffusion of sulfur elements to form air pollution, fully utilizes the resource value of chromium-containing sludge, significantly reduces the emission of hazardous solid waste in related production processes, and reduces the cost of hazardous waste disposal.

[0027] Due to the need to produce different products using calcium chrome sand with different chromium contents as raw materials, calcium chrome sand can be prepared in multiple batches according to the method of the present invention. The obtained calcium chrome sand is respectively sent to corresponding silos for homogenization according to different chromium contents, and then the calcium chrome sand is taken out from different silos according to a preset ratio and mixed and homogenized to obtain the calcium chrome sand with the required chromium content. In this way, calcium chrome sand with stable composition can be prepared according to different needs, so that its composition is controlled within a certain range, the composition and performance stability of calcium chrome sand are improved, which is beneficial to product application and market promotion, and further improves the value of calcium chrome sand.

[0028] The present invention adds Na 2 O.K 2 O.B 2 O 3 The low-melting-point combined flux reduces the melting temperature of calcium chrome sand, which is 950-1300℃, with stable composition, low melting energy consumption and high added value. It can be used as raw material for the production of stainless steel, chromium alloy, green glass, microcrystalline glass, ceramic glaze, coating, etc., and has good economic value and promotion and application prospects.

[0029] Beneficial effects of the present invention:

[0030] 1. The present invention tempers and roasts the chromium-containing sludge, and the reducing agent in the tempering material makes the environment reducing, thereby ensuring that the Cr element in the chromium-containing sludge is retained in the calcium-chrome sand in a non-toxic, non-volatile low-valent state, and preparing calcium-chrome sand with high added value, thereby realizing the resource utilization of chromium and calcium elements in the chromium-containing sludge, significantly reducing the emission of hazardous solid waste in related production processes, and reducing the cost of hazardous waste disposal.

[0031] 2. In the treatment process of the chromium-containing sludge of the present invention, after the chromium-containing sludge is mixed with the conditioning material, due to the addition of Na 2 O.K 2 O.B 2 O 3 The low melting point combined flux can reduce the decomposition temperature of sulfate in chromium-containing sludge and the roasting temperature of batch materials, reduce energy consumption, and thus reduce production costs.

[0032] 3. Reductant C in the conditioning material and O in the environment 2 and sulfate decomposition products in chromium-containing sludge O 2 The reaction generates CO, which can promote the decomposition of sulfate and completely decompose the sulfate component in the chromium-containing sludge. The sulfur-containing flue gas formed can be used to make sulfuric acid, so that the sulfur element can be reasonably used, the diffusion of sulfur element to form air pollution can be avoided, and the resource value of the chromium-containing sludge can be fully utilized.

[0033] 4. Calcium chrome sand is prepared in multiple batches according to the method of the present invention. The obtained calcium chrome sand is homogenized according to different chromium contents. Then, according to the needs of different industries, the calcium chrome sand with the required chromium content can be obtained by mixing and homogenizing.

[0034] 5. The calcium chrome sand prepared by the present invention has stable composition, low melting temperature and high added value, and can be used as raw material for the production of stainless steel, chromium alloy, green glass, microcrystalline glass, ceramic glaze, coating, etc., and has good economic value and promotion and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1The process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the embodiments and drawings.

[0037] See also Figure 1 The method for preparing calcium chrome sand of the present invention comprises the following steps:

[0038] 1) Preparation of batch materials

[0039] The chromium-containing sludge and the conditioning material are uniformly mixed and granulated to form a chromium-containing sludge batch; the weight ratio of the conditioning material to the chromium-containing sludge is 1:0.5-50;

[0040] The tempering material components include SiO 2 :1-80%、Al 2 O 3 :1-30%、CaF 2 :0-1%、B 2 O 3 :0-2%、Na 2 O: 0.2-5%, K 2 O: 0.1-1%, P 2 O 5 :0.1-2%、Fe 2 O 3 :0.05-8%, C:10-83%;

[0041] 2) Drying

[0042] Drying the chromium-containing sludge batch material at a drying temperature of 100 to 280°C;

[0043] 3) Calcination

[0044] The chromium-containing sludge batch material is roasted to form calcium chrome sand, the roasting temperature is 850-1180°C, and the roasting time is 30-180 minutes; sulfur-containing flue gas is collected during the roasting process;

[0045] 4) Cooling.

[0046] Preferably, in step 1), the batch material particle size D 50 0.5~10mm.

[0047] Preferably, in step 2), the drying time is 20 to 240 minutes.

[0048] Preferably, sulfuric acid is prepared from the sulfur-containing flue gas collected during the roasting process in step 3).

[0049] Preferably, in step 4), waste heat in the calcium chrome sand is recovered during the cooling process.

[0050] The melting temperature of the calcium chrome sand of the present invention is 950-1300°C.

[0051] Furthermore, calcium chrome sand is prepared in multiple batches according to the method, and the obtained calcium chrome sand is sent to corresponding silos for homogenization according to different chromium contents. Thereafter, the calcium chrome sand is taken out from different silos according to a preset ratio and mixed and homogenized to obtain calcium chrome sand with the required chromium content.

[0052] Preferably, the number of the silos is 3 to 10.

[0053] The tempering material composition of the embodiment of the present invention is shown in Table 1; the process parameters of the embodiment of the present invention are shown in Table 2.

[0054] The melting temperature of the calcium chrome sand prepared in the embodiment of the present invention is 950-1300° C. The calcium chrome sand can be used as raw material for the production of stainless steel, chromium-containing alloys, green glass, microcrystalline glass, etc., and has good economic value and promotion and application prospects.

[0055]

[0056]

Claims

1. A method for preparing calcium chrome sand, Its characteristics are: The steps include: 1) Preparation of batch materials The chromium-containing sludge and the conditioning material are uniformly mixed and granulated to form a chromium-containing sludge batch; the weight ratio of the conditioning material to the chromium-containing sludge is 1:0.5-50; The tempering material components include SiO 2 :1-80%、Al 2 O 3 :1-30%、CaF 2 :0-1%、B 2 O 3 :0-2%、Na 2 O: 0.2-5%, K 2 O: 0.1-1%, P 2 O 5 :0.1-2%、Fe 2 O 3 :0.05-8%, C:10-83%; 2) Drying Drying the chromium-containing sludge batch material at a drying temperature of 100 to 280°C; 3) Calcination The chromium-containing sludge batch material is roasted to form calcium chrome sand, the roasting temperature is 850-1180°C, and the roasting time is 30-180 minutes; sulfur-containing flue gas is collected during the roasting process; 4) Cooling.

2. The method for preparing calcium chrome sand according to claim 1, It is characterized in that In step 1), the particle size D of the chromium-containing sludge batch material is 50 0.5~10mm.

3. The method for preparing calcium chrome sand according to claim 1, It is characterized in that In step 2), the drying time is 20 to 240 minutes.

4. The method for preparing calcium chrome sand according to claim 1, It is characterized in that The sulfur-containing flue gas collected during the roasting process in step 3) is prepared into sulfuric acid or sodium sulfite.

5. The method for preparing calcium chrome sand according to claim 1, It is characterized in that In step 4), the waste heat in the calcium chrome sand is recovered during the cooling process.

6. The method for preparing calcium chrome sand according to any one of claims 1 to 5, It is characterized in that The melting temperature of the calcium chrome sand is 950-1300°C.

7. The method for preparing calcium chrome sand according to claim 1, It is characterized in that According to the method, calcium chrome sand is prepared in multiple batches. The obtained calcium chrome sand is sent to corresponding silos for homogenization according to different chromium contents. Then, the calcium chrome sand is taken out from different silos according to a preset ratio and mixed and homogenized to obtain calcium chrome sand with the required chromium content.

8. The method for preparing calcium chrome sand according to claim 7, It is characterized in that The number of the silos is 3 to 10.

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