Method for preparing feed-grade basic zinc chloride from high-chlorine zinc-containing smoke dust

Abstract

A method for preparing feed-grade basic zinc chloride by using high-chlorine zinc-containing smoke dust comprises the following steps: leaching treatment: mixing the high-chlorine zinc-containing smoke dust with water, and leaching under a neutral condition to obtain crude zinc chloride leachate; primary impurity removal treatment: adding a precipitator into the crude zinc chloride leaching solution, and filtering after the reaction is finished to obtain a filtrate which is an impurity-removed solution; secondary impurity removal treatment: further adding an oxidizing agent into the impurity-removed solution, and filtering after reaction to obtain a filtrate which is a refined zinc chloride solution; and precipitation treatment: mixing the refined zinc chloride solution with an alkaline solution, filtering after reaction, washing filter residues, and drying to obtain a basic zinc chloride product. According to the method, the high-chlorine zinc-containing smoke dust is used as a raw material, and the basic zinc chloride product with high quality, high purity and few impurities is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of zinc chloride preparation, and in particular to a method for preparing feed-grade basic zinc chloride by utilizing high-chlorine zinc-containing smoke. Background Art

[0002] Basic zinc chloride has the molecular formula Zn5(OH)8Cl·H2O, and its microscopic particles are white or colorless and transparent. Basic zinc chloride is insoluble in water, but easily soluble in weak acids and weak bases. Compared with zinc sulfate, it has the advantages of high absorption rate, low water absorption, and high zinc content. In addition, basic zinc chloride will not antagonize other trace element additives such as copper, iron, zinc, and manganese, and is an ideal new generation of zinc element additives. However, the treatment of high-chlorine zinc dust and zinc slag in existing industrial technology is relatively cumbersome, and high-chlorine zinc dust is prone to yellowing, discoloration, and caking in the preparation of zinc oxide, zinc sulfate and other products, which seriously affects the quality. If a zinc-containing feed additive product is prepared, it is easy to react with other ingredients in the feed after addition, causing the feed to deteriorate.

[0003] The Chinese patent with publication number CN107555469B provides a process for co-producing zinc sulfate and ammonium chloride using high-chlorine zinc slag. It adopts water washing → ammonia leaching → acid leaching, and recovers zinc and chlorine through a step-by-step secondary separation method, thereby achieving the co-production of zinc sulfate and ammonium chloride. However, ammonia water and ammonia gas are used in this process, which is costly and has a low cost-effectiveness for synthesizing ammonium chloride products with low added value. The Chinese patent with publication number CN103060561B uses an organic extractant to separate the chlorine-containing phase, and then uses a sodium carbonate solution for back extraction to obtain a sodium chloride solution. This process requires the use of multiple organic phases, has a high production cost and is not environmentally friendly, and converts chloride ions into industrial salt sodium chloride with low added value.

[0004] Therefore, the present invention aims to develop a method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke to better meet practical needs. Summary of the invention

[0005] The technical problem solved by the present invention is to provide a method for preparing feed-grade basic zinc chloride by utilizing high-chlorine zinc-containing smoke, so as to obtain a feed-grade basic zinc chloride product with stable quality, high purity and few impurities.

[0006] The technical problem solved by the present invention is achieved by adopting the following technical solutions:

[0007] A method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke, characterized in that it comprises

[0008] Leaching treatment: Mix high-chlorine zinc-containing ash with water and leach under neutral conditions to obtain crude zinc chloride leachate;

[0009] Primary impurity removal treatment: add a precipitant to the crude zinc chloride leaching solution, filter after the reaction is completed, and the filtrate is the impurity removal solution;

[0010] Secondary impurity removal treatment: further adding an oxidant to the impurity removal solution, filtering after the reaction, and the filtrate is a refined zinc chloride solution;

[0011] Precipitation treatment: Mix the refined zinc chloride solution with the alkaline solution, filter after the reaction, wash and dry the filter residue to obtain the basic zinc chloride product.

[0012] Furthermore, the zinc content in the high-chlorine zinc-containing fly ash is 30-50%, and the chlorine content is ≥10%.

[0013] Furthermore, the leaching treatment is carried out at room temperature: the high-aluminum zinc-containing smoke dust is crushed and sieved to obtain smoke dust powder, and the smoke dust powder is stirred and rinsed with distilled water at a solid-liquid ratio of 1:1-2, and the rinsing time is 50-70 minutes. After the rinsing is completed, it is filtered, and the filtrate is a crude zinc chloride leaching solution.

[0014] Furthermore, in the first impurity removal treatment, the precipitant is 200-300 mesh zinc powder, and the mass ratio of the zinc powder to the sum of lead, arsenic and cadmium elements in the high-chlorine zinc-containing ash is 2-4:1; stirring is maintained during the impurity removal process. The control of zinc powder particle size is more critical. When the zinc powder particle size is too large and the contact area is insufficient, the zinc powder particles are easily wrapped by inert metals during the replacement reaction, resulting in an incomplete replacement reaction, which in turn leads to excessive lead, arsenic and cadmium, and the product is difficult to meet the national standard requirements.

[0015] Furthermore, in the secondary impurity removal treatment, the oxidant is potassium permanganate or hydrogen peroxide or hypochlorous acid, and the amount of the oxidant added is 1.2 to 1.5 times the theoretical consumption; stirring is maintained during the reaction, the reaction temperature is 70 to 90° C., and the reaction time is 0.8 to 1.2 h.

[0016] Furthermore, after the secondary impurity removal treatment, the obtained refined zinc chloride solution has a zinc ion concentration of 40-80 g / L and a pH value of 4-5; and the contents of lead, cadmium and manganese in the refined zinc chloride solution are all lower than 5 ppm.

[0017] Furthermore, in the precipitation treatment, the refined zinc chloride solution and the alkaline solution are added by a peristaltic pump, the pH value is maintained between 5.5 and 6.5 during the reaction, the temperature is maintained at 70 to 90° C., and the reaction is carried out for 1 to 3 hours; the flow rate is controlled to ensure that the refined zinc chloride solution and the alkaline solution are added at the same time; stirring is maintained during the reaction, and after the addition is completed, the reaction is continued for 20 to 40 minutes.

[0018] Furthermore, the flow rate of the refined zinc chloride solution is 7-9 ml / min, and the flow rate of the alkaline solution is 2-6 ml / min.

[0019] Furthermore, the alkaline solution is a sodium oxide solution with a mass concentration of 10 to 30%.

[0020] Beneficial effects: The method for preparing feed-grade basic zinc chloride by utilizing high-chlorine zinc-containing smoke of the present invention has the advantages of easy control of the preparation process and low cost; the chloride ions in the high-chlorine zinc-containing smoke are processed to become components of basic zinc chloride; the purity of the prepared basic zinc chloride is not less than 99%, which meets the relevant provisions of GB / T22546-2008 on basic zinc chloride as a feed additive, and can be used as a feed additive; the product has no yellowing, discoloration or caking; and because the product has high purity and few impurities, it is not easy to react with other components in the feed after being added into the feed, and the quality of the feed is more stable.

[0021] The method for preparing feed-grade basic zinc chloride by utilizing high-chlorine zinc-containing smoke dust of the present invention can timely process the high-chlorine zinc-containing smoke dust generated in the existing zinc sulfate production process, thereby solving the problem that the high chloride ion content in the existing zinc sulfate production process affects the quality of subsequent products. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The X-ray diffraction pattern of basic zinc chloride prepared in Example 1 is shown in FIG. DETAILED DESCRIPTION

[0023] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0024] Example 1

[0025] The method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke described in this embodiment comprises the following steps:

[0026] Leaching treatment: Take 250g of high-chlorine zinc dust, crush, pulverize, pass through a 200-mesh sieve, and test the content as shown in Table 1;

[0027] Table 1: Composition of high chlorine zinc dust raw materials in Example 1

[0028]

[0029] At room temperature, high-chlorine zinc-containing ash is mixed with 500 ml of distilled water, the stirring speed is 400 r / min, and the rinsing time is 60 min; after rinsing, the filtrate is filtered, and the filtrate is a crude zinc chloride leaching solution. The composition detection of the crude zinc chloride leaching solution is shown in Table 2.

[0030] Table 2 Composition of crude zinc chloride leachate in Example 1

[0031]

[0032] Primary impurity removal treatment: Place the crude zinc chloride leachate in a beaker and place it on an electromagnetic stirrer, set the stirring speed to 400r / min, slowly add 2g of zinc powder, the particle size of the zinc powder is about 200 mesh, and the zinc powder addition time is 20min; after the zinc powder is added, small spherical black precipitates immediately appear in the solution; as the zinc powder is continuously added, the black spherical precipitates gradually increase. After the zinc powder is added, continue to stir and react for 10min, the solution becomes turbid and fine bubbles are generated. The reaction solution is filtered, and the filtrate is the impurity removal solution. The composition of the impurity removal solution is shown in Table 3.

[0033] Table 3 Composition of impurity removal solution in Example 1

[0034]

[0035] Secondary impurity removal treatment: 0.27g potassium permanganate was dissolved in 20ml water, and added dropwise to the impurity removal solution. The reaction temperature was set at 80°C, the stirring speed was 400r / min, the reaction time was 1 hour, and the yellow-black precipitate was filtered out to obtain a clear, transparent and colorless refined zinc chloride impurity removal solution. The composition of the refined zinc chloride impurity removal solution is shown in Table 4.

[0036] Table 4: Composition of refined zinc chloride impurity removal liquid in Example 1

[0037]

[0038]

[0039] Precipitation treatment: Use a peristaltic pump to drop 15% sodium hydroxide and refined zinc chloride solution at the same time, and the two react at 80°C. The flow rate of refined zinc chloride solution is 8.3ml / min, and the flow rate of 15% sodium hydroxide is 3-4ml / min. The pH is controlled to be between 5.5 and 6, and the dropwise addition is completed in about one hour. Continue to react for half an hour, filter the reaction solution, take the filter residue, wash the filter residue with distilled water, and dry it to obtain 45.9g of white basic zinc chloride powder.

[0040] The obtained white basic zinc chloride powder was tested, and the results are shown in Table 5.

[0041] Table 5 Basic zinc chloride powder composition in Example 1

[0042]

[0043] The product purity was calculated to be 99% according to the Rirtveld full spectrum fitting method in X-ray diffraction. Figure 1 shown.

[0044] Example 2

[0045] The method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke described in this embodiment comprises the following steps:

[0046] Leaching treatment: Take 250g of high-chlorine zinc dust, crush, pulverize, pass through a 200-mesh sieve, and test the content as shown in Table 6;

[0047] Table 6 Composition of high chlorine zinc dust raw materials in Example 2

[0048]

[0049] At room temperature, 500 g of high-chlorine zinc-containing fly ash was mixed with 500 ml of distilled water, the stirring speed was 400 r / min, and the rinsing time was 60 min; after rinsing, the filtrate was filtered, and the filtrate was a crude zinc chloride leaching solution. The composition detection of the crude zinc chloride leaching solution is shown in Table 7.

[0050] Table 7 Composition of crude zinc chloride leachate in Example 2

[0051]

[0052]

[0053] Primary impurity removal treatment: 500 ml of crude zinc chloride leachate was placed in a beaker and placed on an electromagnetic stirrer, the stirring speed was set to 400 r / min, and 2 g of zinc powder was slowly added. The particle size of the zinc powder was about 250 mesh, and the zinc powder addition time was 20 min. After the zinc powder was added, small black spherical precipitates immediately appeared in the solution. As the zinc powder was continuously added, the black spherical precipitates gradually increased. After the zinc powder was added, the stirring reaction was continued for 10 min, and the solution became turbid and fine bubbles were generated. The reaction solution was filtered, and the filtrate was the impurity removal solution. The composition of the impurity removal solution is shown in Table 8.

[0054] Table 8 Composition of impurity removal solution in Example 2

[0055]

[0056] Secondary impurity removal treatment: 0.3g potassium permanganate was dissolved in 20ml water, and added dropwise to the impurity removal solution. The reaction temperature was set to 85°C, the stirring speed was 400r / min, the reaction time was 1.1 hours, and the yellow-black precipitate was filtered out to obtain a clear, transparent and colorless refined zinc chloride impurity removal solution. The composition of the refined zinc chloride impurity removal solution is shown in Table 9.

[0057] Table 9 Composition of refined zinc chloride impurity removal liquid in Example 2

[0058]

[0059] Precipitation treatment: Use a peristaltic pump to drop 30% sodium hydroxide and refined zinc chloride solution at the same time, and the two react at 80°C. The flow rate of refined zinc chloride solution is 8.3ml / min, and the flow rate of 15% sodium hydroxide is 3-4ml / min. The pH is controlled to be between 5.5 and 6, and the dropwise addition is completed in about one hour. Continue to react for half an hour, filter the reaction solution, take the filter residue, wash the filter residue with distilled water, and dry it to obtain 46.13g of white basic zinc chloride powder.

[0060] The obtained white basic zinc chloride powder was tested, and the results are shown in Table 10.

[0061] Table 10 Composition of basic zinc chloride powder in Example 2

[0062]

[0063] The product purity was calculated to be 99% according to the Rirtveld full spectrum fitting method in X-ray diffraction.

[0064] Example 3

[0065] Compared with Example 1, in the precipitation step, 0.27 g of potassium permanganate was replaced with 0.57 g of hypochlorous acid with a concentration of 30%, and the other steps remained unchanged, to obtain 46.3 g of white powdered basic zinc chloride with a yield of 96%, as shown in Table 11. According to the X-ray diffraction Rietveld full fitting method, the purity of the product was 99%.

[0066] Table 11 Composition of basic zinc chloride powder in Example 3

[0067]

[0068] Comparative Example 1

[0069] Compared with Example 1, the difference is that the pH of the reaction of the refined zinc chloride solution and the sodium hydroxide solution is changed to 7, and the rest is the same. The indicators of the basic zinc chloride product finally obtained are shown in Table 12:

[0070] Table 12 Basic zinc chloride composition in comparative example 1

[0071]

[0072] It can be seen that when the pH of the reaction between refined zinc chloride solution and sodium hydroxide solution is improperly controlled, the zinc content will be too high and the chlorine content will be too low. Too high a pH will cause the zinc hydroxide content in the reaction system to be too high and the encapsulated chloride ion content to be too low, and the final product will not meet the content required by the national standard.

[0073] Comparative Example 2

[0074] Compared with Example 1, the difference is that during the precipitation reaction, the flow rates of sodium hydroxide and refined zinc chloride solution are doubled, the reaction time is 30 minutes, and the other conditions remain unchanged. The basic zinc chloride product obtained has indicators as shown in Table 13.

[0075] Table 13 Basic zinc chloride composition in comparative example 2

[0076]

[0077] It can be seen that when the flow rate is improperly controlled and the reaction time is not sufficient, the basic zinc chloride crystals have not been completely formed, and there are still a large number of unreacted zinc hydroxide crystals in the system, resulting in the basic zinc chloride product having a high zinc content and a low chlorine content, and the product is unqualified.

[0078] Comparative Example 3

[0079] In this control example, in a decontamination process, 80-mesh zinc powder was used instead of 200-mesh zinc powder, and the rest remained unchanged. The basic zinc chloride product obtained had the indicators shown in Table 14.

[0080] Table 14 Basic zinc chloride composition in comparative example 3

[0081]

[0082] It can be seen that the control of zinc powder particle size is more critical. When the zinc powder particle size is too large and the contact area is insufficient, the outside of the zinc powder particles will be wrapped by inert metal during the replacement reaction, and the replacement reaction will not be complete, resulting in excessive lead, arsenic and cadmium, and the product will not meet national standards.

[0083] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke, characterized in that: include Leaching treatment: Mix high-chlorine zinc-containing ash with water and leach under neutral conditions to obtain crude zinc chloride leachate; Primary impurity removal treatment: add a precipitant to the crude zinc chloride leaching solution, filter after the reaction is completed, and the filtrate is the impurity removal solution; Secondary impurity removal treatment: further adding an oxidant to the impurity removal solution, filtering after the reaction, and the filtrate is a refined zinc chloride solution; Precipitation treatment: Mix the refined zinc chloride solution with the alkaline solution, filter after the reaction, wash and dry the filter residue to obtain the basic zinc chloride product.

2. The method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke according to claim 1, characterized in that: The zinc content in high-chlorine zinc-containing fly ash is 30-50%, and the chlorine content is ≥10%.

3. The method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke according to claim 1, characterized in that: The leaching treatment is carried out at room temperature: the high-aluminum zinc-containing smoke dust is crushed and sieved to obtain smoke dust powder, and the smoke dust powder and distilled water are stirred and rinsed at a solid-liquid ratio of 1:1-2. The rinsing time is 50-70 minutes. After the rinsing is completed, it is filtered, and the filtrate is a crude zinc chloride leaching solution.

4. The method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke according to claim 1, characterized in that: In the primary impurity removal treatment, the precipitant is 200-300 mesh zinc powder, and the mass ratio of the zinc powder to the total amount of lead, arsenic and cadmium elements in the high-chlorine zinc-containing fly ash is 2-4:1; stirring is maintained during the impurity removal process.

5. The method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke according to claim 1, characterized in that: In the secondary impurity removal treatment, the oxidant is potassium permanganate or hydrogen peroxide or hypochlorous acid, and the amount of the oxidant added is 1.2 to 1.5 times the theoretical consumption; stirring is maintained during the reaction, the reaction temperature is 70 to 90° C., and the reaction time is 0.8 to 1.2 hours.

6. The method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke according to claim 5, characterized in that: After the secondary impurity removal treatment, the obtained refined zinc chloride solution has a zinc ion concentration of 40-80 g / L and a pH value of 4-5; and the contents of lead, cadmium and manganese in the refined zinc chloride solution are all lower than 5 ppm.

7. The method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke according to claim 1, characterized in that: During the precipitation treatment, the refined zinc chloride solution and the alkaline solution are added by a peristaltic pump. During the reaction, the pH value is maintained between 5.5 and 6.5, the temperature is maintained at 70 to 90°C, and the reaction is carried out for 1 to 3 hours. The flow rate is controlled to ensure that the refined zinc chloride solution and the alkaline solution are added at the same time. Stirring is maintained during the reaction. After the addition is completed, the reaction is continued for 20 to 40 minutes.

8. The method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke according to claim 7, characterized in that: During the precipitation treatment, the flow rate of the refined zinc chloride solution is 7-9 ml / min, and the flow rate of the alkaline solution is 2-6 ml / min.

9. The method for preparing feed-grade basic zinc chloride using high-chlorine zinc-containing smoke according to claim 7, characterized in that: The alkaline solution is a sodium oxide solution with a mass concentration of 10 to 30%.

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