Method for producing barium sulfate and byproduct calcium chloride solution by using gypsum slag

Abstract

The invention provides a method for producing barium sulfate and a byproduct calcium chloride solution by using gypsum residues. The method comprises the following steps: dissolving commercially available barium chloride with recycled steam condensate water, and carrying out filter pressing to obtain barium chloride filtrate; dissolving gypsum with recycled steam condensate water, and then carrying out filter pressing to obtain a calcium sulfate solution; mixing the calcium sulfate solution with the barium chloride filtrate for reaction to obtain reaction slurry; filtering the reaction slurry to obtain a barium sulfate filter cake and a byproduct calcium chloride solution; washing and filtering the barium sulfate filter cake by using a vacuum belt filter; and water-washed barium sulfate obtained by filter pressing after water washing in the secondary washing section is dried and packaged to obtain a barium sulfate product. The method for producing the barium sulfate and the byproduct calcium chloride solution by using the gypsum residues can save energy and reduce emission, and is simple, low in cost and high in economic benefit.

Description

Technical Field

[0001] The invention relates to the technical field of industrial waste recycling, in particular to a method for producing barium sulfate and a byproduct calcium chloride solution by utilizing gypsum slag. Background Art

[0002] Environmental protection and material recycling industries have huge development potential. Material recycling is an important guarantee for the sustainable development of the national economy. It can not only save resources and make them sustainable, but also reduce environmental pollution, maintain ecological balance, and improve social and economic benefits.

[0003] In recent years, the substantial increase in investment in environmental protection and material recycling industries has brought the global environmental protection and material recycling industries into a stage of rapid development and has become an important part of the global national economy. my country is a country with a large amount of materials, and environmental protection and material recycling work are also particularly important. To this end, the country has successively issued a number of relevant policies and regulations to promote my country's sustainable development and vigorously promote the development of global resource comprehensive utilization.

[0004] In the industrial production process of nonferrous smelting industry, a large amount of gypsum slag is often produced. The utilization rate of gypsum is reduced, resulting in a large amount of gypsum slag being stored. This not only causes a waste of resources, but also easily has a significant impact on the environment.

[0005] Therefore, there is an urgent need to develop a method that can effectively process and reuse gypsum to ensure that a large amount of stockpiled gypsum slag resources can be comprehensively recycled, improve resource utilization, and reduce the impact on the environment. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for producing barium sulfate and a byproduct calcium chloride solution by utilizing gypsum slag, which can save energy and reduce emissions, has low cost, high economic benefits and a simple method.

[0007] In order to solve the above technical problems, the present invention provides a method for producing barium sulfate and a by-product calcium chloride solution by using gypsum slag, comprising the following steps:

[0008] Dissolving commercially available barium chloride with recovered steam condensate and filtering to obtain barium chloride filtrate;

[0009] Dissolving the gypsum with the recovered steam condensate and filtering it to obtain a calcium sulfate solution;

[0010] Mixing the calcium sulfate solution and the barium chloride filtrate to react to obtain a reaction slurry;

[0011] The reaction slurry is hydraulically filtered to obtain a barium sulfate filter cake and a by-product calcium chloride solution;

[0012] The barium sulfate filter cake is washed and filtered using a vacuum belt filter;

[0013] The water-washed barium sulfate obtained after water washing in the secondary washing stage is filtered and dried and packaged to obtain the barium sulfate product.

[0014] Furthermore, the dissolution temperature of the commercially available barium chloride in the recovered steam condensate is 75 to 103° C., and the dissolution time is 6 to 10 hours.

[0015] Furthermore, the gypsum is gypsum powder obtained by desulfurization and ball milling of waste gypsum produced in the non-ferrous smelting industry.

[0016] Furthermore, the vacuum belt filter includes a primary washing section and a secondary washing section.

[0017] Furthermore, when the barium sulfate filter cake is washed and filtered by a vacuum belt filter, tap water is added from the secondary washing section, and the water washing filtrate obtained by filter pressing after water washing in the secondary washing section is returned to the primary washing section to wash the barium sulfate filter cake.

[0018] Furthermore, when the barium sulfate filter cake is washed and filtered by a vacuum belt filter, the primary washing filtrate obtained by filtering after washing in the primary washing stage is used to dissolve the barium chloride.

[0019] Furthermore, the primary washed barium sulfate obtained by filter pressing after washing in the primary washing stage is washed in the secondary washing stage with tap water added from the secondary washing stage.

[0020] Furthermore, the water-washed barium sulfate is dried using a two-stage hollow double-blade dryer, the drying temperature is 100-103° C., and the drying time is 100-150 min.

[0021] Furthermore, the moisture content of the barium sulfate at the end point of barium sulfate drying is ≤0.2%.

[0022] The present invention provides a method for producing barium sulfate and byproduct calcium chloride solution by using gypsum slag, which reacts the waste gypsum produced by the non-ferrous smelting industry with relatively cheap barium chloride, and through washing and filtering, not only can the waste gypsum slag resources produced by the non-ferrous smelting industry be comprehensively recycled, but also can produce barium sulfate products and calcium chloride byproducts with high added value. It not only improves the utilization rate of resources and reduces the impact of waste resource storage on the environment, but also has low cost, high economic value and good economic benefits.

[0023] In addition, the present invention provides a method for producing barium sulfate and a byproduct calcium chloride solution by utilizing gypsum slag, wherein gypsum powder and barium chloride are dissolved in water and filtered to obtain solutions for direct reaction, and then washed and filtered to obtain a high-purity barium sulfate product and a high-purity byproduct calcium chloride solution. The method is simple, the reaction principle is simple, and the reaction conditions are low, and the reaction can be completed at room temperature, thereby having good economic benefits.

[0024] Meanwhile, the present invention provides a method for producing barium sulfate and a by-product calcium chloride solution by utilizing gypsum slag, wherein a barium sulfate filter cake obtained by reacting a gypsum solution with a barium chloride solution is washed and filtered by a vacuum belt filter, tap water is added from a secondary washing section, a water washing filtrate obtained by filtering after water washing in the secondary washing section is returned to a primary washing section to wash the barium sulfate filter cake, and a primary washing filtrate obtained by filtering after washing in the primary washing section is used to dissolve barium chloride, thereby reducing the discharge of substances in the process, achieving energy conservation and emission reduction, and reducing the impact on the environment.

[0025] Therefore, the method for producing barium sulfate and byproduct calcium chloride solution by utilizing gypsum slag provided by the present invention is simple, low in cost, can save energy and reduce emissions, is environmentally friendly, has high economic benefits, has good application prospects, and is worthy of promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flow chart of a method for producing barium sulfate and by-product calcium chloride solution using gypsum slag is provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] See also Figure 1 The present invention provides a method for producing barium sulfate and a byproduct calcium chloride solution by using gypsum slag, comprising the following steps:

[0028] Step 1) Purchase commercially available barium chloride, and in order to save water and reduce resource waste, fully dissolve the barium chloride in the recovered steam condensate to obtain a barium chloride solution, and then remove the dissolved residue in the solution by filter pressing to obtain a barium chloride filtrate.

[0029] In addition, based on the relationship between the solubility of barium chloride and temperature, the dissolution rate and the consumption of heat energy by temperature are comprehensively considered. In order to speed up the dissolution rate and improve the process efficiency while minimizing the consumption of heat energy and reducing costs, the dissolution temperature of commercially available barium chloride in the recovered steam condensate is controlled to 75-103°C and the dissolution time is controlled to 6-10h.

[0030] As a specific embodiment of the present invention, in order to achieve an optimal dissolution rate while minimizing the consumption of heat energy, the dissolution temperature of commercially available barium chloride in the recovered steam condensate is controlled to 780° C. and the dissolution time is controlled to 8 hours.

[0031] Step 2) Take the waste gypsum generated by the non-ferrous smelting industry, crush it for desulfurization, and then put it into a ball mill to obtain gypsum powder, and then dissolve the gypsum powder with recycled steam condensate to obtain a calcium sulfate solution and insoluble impurities, and then filter the solid-liquid mixture to remove the insoluble residue to obtain a calcium sulfate solution.

[0032] Step 3) Mix the calcium sulfate solution and the barium chloride filtrate to obtain a reaction slurry. The process is simple, and the reaction equation is as follows:

[0033] CaSO4+BaCl2=BaSO4↓+CaCl2

[0034] During the reaction, the insoluble barium sulfate generated by the reaction is suspended in the calcium chloride solution to obtain a reaction slurry.

[0035] Step 4) The obtained reaction slurry is filtered to obtain a barium sulfate filter cake and a by-product calcium chloride solution.

[0036] Since the gypsum and barium chloride are dissolved and filtered to remove the insoluble impurities, a relatively pure calcium sulfate solution and barium chloride filtrate are obtained, and the relatively pure calcium sulfate solution and barium chloride filtrate are reacted and filtered to obtain a relatively pure calcium chloride solution, the obtained calcium chloride solution can be directly sold as a by-product. Not only is the economic value high, but the process is simple and efficient, and has high economic benefits.

[0037] Step 5) Since the barium sulfate precipitate obtained by filtration is easily doped with a certain amount of calcium chloride, the barium sulfate filter cake obtained by pressure filtration needs to be further washed.

[0038] The obtained barium sulfate filter cake is washed and filtered by a vacuum belt filter. The vacuum belt filter adopts a two-stage vacuum washing and filtration. Among them, fresh tap water is used for washing in the secondary washing section, that is, tap water is added from the secondary washing section. In the secondary washing section, fresh tap water is used to wash the primary washed barium sulfate with water, and then filter presses to obtain a water-washed slurry. The water-washed slurry is separated by filter presses to obtain a water-washed filtrate and a water-washed barium sulfate. The water-washed filtrate is returned to the primary washing section to wash the barium sulfate filter cake. The water-washed filtrate is used to wash the barium sulfate filter cake in the primary washing section to obtain a primary washing slurry. The primary washing slurry is separated by pressure filtration to obtain a primary washing barium sulfate and a primary washing filtrate. The primary washing barium sulfate is further washed with water in the secondary washing section, and the primary washing filtrate is returned to the barium chloride dissolution site to dissolve the barium chloride.

[0039] The invention makes full use of water washing filtrate to wash the barium sulfate filter cake in the primary washing section, and uses the primary washing filtrate to dissolve the barium chloride, so that the waste liquid in the process can be fully utilized, and the waste of water resources is reduced, which not only saves costs and improves economic benefits, but also achieves energy conservation and emission reduction, reduces the impact on the environment, and is green and environmentally friendly.

[0040] At the same time, since a certain amount of calcium chloride is doped in the barium sulfate filter cake, after the barium sulfate filter cake is repeatedly washed, the calcium chloride doped in the barium sulfate filter cake remains in the washing liquid, so that finally a vacuum filtrate with a high calcium chloride content is produced in the filtration section of the vacuum belt filter. The vacuum filtrate calcium chloride solution can be stored for sale or evaporated and concentrated into products for sale, which can not only make full use of resources but also provide further economic benefits.

[0041] Step 6) The water-washed barium sulfate obtained by water washing and pressure filtration in the secondary washing stage is dried and then packaged to obtain the barium sulfate product.

[0042] The water-washed barium sulfate is dried using a two-stage hollow double-paddle dryer, with each stage of drying temperature being 100 to 103° C. and the drying time being 100 to 150 minutes.

[0043] When the barium sulfate drying end point has a barium sulfate moisture content of ≤0.2%, the barium sulfate product is obtained. The barium sulfate product can be packaged by an automatic metering and packaging machine for sale. Thus, the barium sulfate product with high added value is obtained, which not only improves the utilization rate of resources and reduces the impact of waste resource storage on the environment, but also increases the economic value and improves the economic benefits.

[0044] The following is a specific description of a method for producing barium sulfate and a byproduct calcium chloride solution using gypsum slag provided by the present invention by way of example.

[0045] 1) Dissolve and filter the barium chloride purchased from the market with the recovered steam condensate to obtain a saturated barium chloride solution. In order to increase the reaction speed and degree of the calcium sulfate solution and the barium chloride, the barium chloride is usually dissolved in water to form a barium chloride solution, and then reacted with the calcium sulfate solution. The solubility of barium chloride at different temperatures is 31.6g at 0°C, 35.7g at 20°C, 39.4g at 35°C, 52.4g at 80°C, and 59.4g at 100°C. According to the relationship between solubility and temperature, the dissolution rate and the consumption of heat energy by temperature are comprehensively considered. In order to speed up the dissolution rate, improve process efficiency, minimize the consumption of heat energy, and reduce costs, the dissolution temperature of barium chloride is selected to be 80°C. At 80°C, a dissolution tank of suitable size is selected as the dissolution equipment, and the recovered steam condensate is heated to 80°C with steam to dissolve the industrial barium chloride to form a saturated solution. Among them, the operation cycle of dissolution including water distribution, adding barium sulfide, heating, dissolution, and filtration is controlled to be completed within 8 hours.

[0046] In addition, since the saturated barium chloride solution obtained by dissolution has less impurities and colloids, it has a good filtration speed and a filtration coefficient of about 0.25m 3 / (m 2*h), in order to improve the separation efficiency of impurities and colloids in the solution, a suitable filter press is selected according to the processing volume to filter and separate the saturated barium chloride solution. Among them, when the dissolution operation cycle is 8 hours, the filter press process is controlled within 2 hours, so that the average total time for filtration per day is about 6 hours.

[0047] 2) Take the waste gypsum generated by the non-ferrous smelting industry, crush it for desulfurization, and then put it into a ball mill to obtain gypsum powder, and then dissolve the gypsum powder with recycled steam condensate to obtain a solid-liquid mixture formed by a saturated calcium sulfate solution and insoluble impurities, and then filter the solid-liquid mixture to remove the insoluble residue to obtain a saturated calcium sulfate solution.

[0048] 3) Mix the saturated calcium sulfate solution and the saturated barium chloride filtrate to obtain a reaction slurry. The process is simple, and the reaction equation is as follows:

[0049] CaSO4+BaCl2=BaSO4↓+CaCl2

[0050] During the reaction, the insoluble barium sulfate generated by the reaction is suspended in the calcium chloride solution to obtain a reaction slurry.

[0051] Among them, a suitable reaction tank is selected according to the reaction amount requirement, and a saturated barium chloride solution and a saturated calcium sulfate solution are added to the reaction tank. The reaction of calcium sulfate and barium chloride is very thorough and the reaction speed is fast. The reaction may be completely completed within 2 hours.

[0052] 4) Select a suitable filter press according to the processing volume requirement, and filter the obtained reaction slurry to obtain a barium sulfate filter cake and a by-product calcium chloride solution.

[0053] Among them, although the barium sulfate precipitation product has little colloid, the barium sulfate is a viscous material with fine particles, the filtration performance is general, the filtration speed is moderate, and the filtration coefficient is 0.15m 3 / (m 2 *h), and the obtained reaction slurry is filtered by a filter press to obtain a barium sulfate filter cake and a byproduct calcium chloride solution. The filter press operation process takes 2 hours, and the average total time for filtration per day is 9 hours, which is 2700 hours in 300 days. The byproduct calcium chloride solution after the filter press can be sold and sent to enterprises in need for use, so the calcium chloride solution does not need to be evaporated and concentrated. It is recommended to design a calcium chloride solution storage tank for storage in a cycle of 7 days.

[0054] 5) Since the barium sulfate precipitate obtained by filter pressing is easily doped with a certain amount of calcium chloride, the barium sulfate filter cake obtained by filter pressing needs to be further washed.

[0055] The obtained barium sulfate filter cake is washed and filtered by a vacuum belt filter. The vacuum belt filter adopts a two-stage vacuum washing and filtration. Among them, fresh tap water is used for washing in the secondary washing section, that is, tap water is added from the secondary washing section. In the secondary washing section, fresh tap water is used to wash the primary washed barium sulfate with water, and then the water washing slurry is filtered to obtain a water washing slurry. The water washing slurry is separated by filtering to obtain a water washing filtrate and a water washing barium sulfate. The water washing filtrate is returned to the primary washing section to wash the barium sulfate filter cake. The water washing filtrate is used to wash the barium sulfate filter cake in the primary washing section to obtain a primary washing slurry. The primary washing slurry is filtered and separated to obtain a primary washing barium sulfate and a primary washing filtrate. The primary washing barium sulfate is further washed with water in the secondary washing section, and the primary washing filtrate is returned to the barium chloride dissolution site to dissolve the barium chloride.

[0056] In order to control costs, it is necessary to control the total amount of washing water used for the barium sulfate filter cake. During stirring and washing, the liquid-to-solid ratio should be controlled as small as possible to reduce the subsequent evaporation of the washing filtrate. Therefore, the water-soluble substances of the barium sulfate filter cake obtained after stirring and washing only drop to 30% of the original, and it is impossible to ensure that the product meets the requirements. Therefore, the barium sulfate filter cake must be washed twice to ensure that the water-soluble substance content of the final barium sulfate product meets the quality index requirements of the barium sulfate product. The primary and secondary washing of the barium sulfate filter cake can be completed directly on the primary washing section and secondary washing section of the vacuum belt filter.

[0057] In addition, fresh tap water is added from the secondary washing section, and the vacuum filtrate after the second washing is returned to the primary washing section for a second washing, and the vacuum filtrate after the first washing is returned to the barium chloride dissolving tank for dissolving barium chloride. Finally, the vacuum filtrate with a high calcium chloride content is produced in the filtration section of the vacuum belt filter, which is stored for sale or evaporated and concentrated into products for sale.

[0058] The embodiment of the present invention fully utilizes the water washing filtrate to wash the barium sulfate filter cake in the primary washing stage, and utilizes the primary washing filtrate to dissolve the barium chloride, so that the waste liquid in the process can be fully utilized, and the waste of water resources is reduced, which not only saves costs and improves economic benefits, but also achieves energy conservation and emission reduction, reduces the impact on the environment, and is green and environmentally friendly.

[0059] At the same time, since a certain amount of calcium chloride is doped in the barium sulfate filter cake, after the barium sulfate filter cake is washed repeatedly, the calcium chloride doped in the barium sulfate filter cake remains in the washing liquid, and finally a vacuum filtrate with a high calcium chloride content is produced in the filtration section of the vacuum belt filter. The vacuum filtrate calcium chloride solution can be stored for sale or evaporated and concentrated into products for sale, which can not only make full use of resources but also provide further economic benefits.

[0060] 6) The water-washed barium sulfate obtained by filtering after washing is dried and packaged to obtain the barium sulfate product. The barium sulfate is dried by a hollow paddle dryer. The hollow paddle dryer mainly consists of two parts, the first part is a jacketed cylindrical fixed shell, and the second part is a rotating hollow shaft and hollow blades. During drying, the barium sulfate is added from the top of one end of the shell. Under the action of the rotating hollow paddle, after drying, the dried barium sulfate leaves from the bottom of the other end of the shell. Steam is passed through the shell and the hollow paddle, and the heat is transferred to the barium sulfate in the dryer in a partition heat transfer manner. After the barium sulfate obtains heat, the temperature rises and the water evaporates gradually. The water vapor generated after evaporation leaves the dryer from the outlet above the shell under the action of the induced draft fan.

[0061] When barium sulfate with a high moisture content is processed, the hollow paddle dryer is usually dried using a two-stage hollow double-paddle dryer, which includes a first-stage hollow paddle dryer installed above and a second-stage hollow paddle dryer installed in parallel below.

[0062] Since the moisture content of the barium sulfate produced by the embodiment of the present invention is relatively high, up to 35% on average, the barium sulfate obtained by the embodiment of the present invention is dried using a two-stage hollow double-paddle dryer. When the barium sulfate is subjected to secondary drying, the barium sulfate directly enters the inlet of the second-stage hollow paddle dryer from the outlet of the first-stage hollow paddle dryer. After the first-stage drying, the moisture content of the barium sulfate is reduced from 30-40% to 10-15%, which does not meet the quality index requirements of the product. After the second-stage drying, the moisture content is reduced to 0.1%, which meets the product quality requirements. The drying temperature of each stage is 100-103°C, and the drying time is 100-150 minutes.

[0063] Since most of the hollow paddle dryers are made of stainless steel, the product quality is more guaranteed. In addition, the hollow paddle dryer has a compact structure, small footprint, high degree of mechanization, and low labor intensity. In addition, the main energy consumption of the hollow paddle dryer is water vapor. For every ton of barium sulfate product produced, about 1.0 to 1.2 tons of steam is consumed, and 40 to 60 kWh of electricity is consumed.

[0064] When the moisture content of barium sulfate at the end of drying is ≤0.2%, the barium sulfate product can be packaged by an automatic metering and packaging machine for storage or external sale, thereby obtaining a barium sulfate product with high added value. This not only improves the utilization rate of resources and reduces the impact of waste resource storage on the environment, but also increases the economic value and improves economic benefits.

[0065] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for producing barium sulfate and byproduct calcium chloride solution using gypsum slag, characterized in that: The steps include: Dissolving commercially available barium chloride with recovered steam condensate and filtering to obtain barium chloride filtrate; Dissolving the gypsum with the recovered steam condensate and filtering it to obtain a calcium sulfate solution; Mixing the calcium sulfate solution and the barium chloride filtrate to react to obtain a reaction slurry; The reaction slurry is hydraulically filtered to obtain a barium sulfate filter cake and a by-product calcium chloride solution; The barium sulfate filter cake is washed and filtered using a vacuum belt filter; The water-washed barium sulfate obtained after water washing in the secondary washing stage is filtered and dried and packaged to obtain the barium sulfate product.

2. The method for producing barium sulfate and byproduct calcium chloride solution by utilizing gypsum slag according to claim 1, characterized in that: The dissolution temperature of the commercially available barium chloride in the recovered steam condensate is 75 to 103° C., and the dissolution time is 6 to 10 hours.

3. The method for producing barium sulfate and byproduct calcium chloride solution by utilizing gypsum slag according to claim 1, characterized in that: The gypsum is gypsum powder obtained by desulfurizing and ball-milling waste gypsum produced in the nonferrous smelting industry.

4. The method for producing barium sulfate and byproduct calcium chloride solution by utilizing gypsum slag according to claim 1, characterized in that: The vacuum belt filter comprises a primary washing section and a secondary washing section.

5. The method for producing barium sulfate and byproduct calcium chloride solution by utilizing gypsum slag according to claim 4, characterized in that: When the barium sulfate filter cake is washed and filtered by a vacuum belt filter, tap water is added from the secondary washing section, and the water washing filtrate obtained by filtering after water washing in the secondary washing section is returned to the primary washing section to wash the barium sulfate filter cake.

6. The method for producing barium sulfate and byproduct calcium chloride solution by utilizing gypsum slag according to claim 5, characterized in that: When the barium sulfate filter cake is washed and filtered by a vacuum belt filter, the primary washing filtrate obtained by filtering after washing in the primary washing stage is used to dissolve the barium chloride.

7. The method for producing barium sulfate and byproduct calcium chloride solution by utilizing gypsum slag according to claim 6, characterized in that: The primary washed barium sulfate obtained by filtering after washing in the primary washing stage is washed in the secondary washing stage with tap water added from the secondary washing stage.

8. The method for producing barium sulfate and byproduct calcium chloride solution by utilizing gypsum slag according to claim 1, characterized in that: The water-washed barium sulfate is dried using a two-stage hollow double-blade dryer at a drying temperature of 100 to 103° C. and a drying time of 100 to 150 minutes.

9. The method for producing barium sulfate and byproduct calcium chloride solution by utilizing gypsum slag according to claim 8, characterized in that: The barium sulfate moisture content at the barium sulfate drying end point is ≤0.2%.

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