Chromium-containing waste treatment method

Abstract

The invention provides a chromium-containing waste treatment method, and relates to the technical field of hazardous waste treatment.The chromium-containing waste treatment method comprises the steps that in the pretreatment and compatibility stage, chromium-containing waste is refined, classified, put in storage and homogenized, and mixed chromium-containing waste is formed through compatibility and mixing according to the proportion based on component detection; calculating the adding amount of the mixed waste according to an adding amount calculation formula, and adding the mixed waste into a cement kiln; in the co-processing stage, the production data of the cement kiln are monitored in real time, the K / Cr element mass ratio is dynamically adjusted, and the production parameters and the solid waste doping amount are adjusted; in the cement grinding stage, a composite reducing agent is added as a backup measure, Cr < 6 + > in the cement is reduced into Cr < 3 + >, the content of Cr < 6 + > is reduced, and the quality of a finally produced cement product is ensured; according to the invention, through the control of three links of previous compatibility, middle control and later regulation, the safe and harmless treatment of the chromium-containing hazardous waste is ensured, and the cement product is qualified, green and environment-friendly, so that the harmless treatment of the chromium-containing waste is finally realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hazardous waste treatment, in particular to a chromium-containing waste treatment method. BACKGROUND

[0002] In industrial production, the main sources of chromium are electroplating, printing and dyeing, leather metallurgy and other industries. Chromium in hazardous waste mainly exists in the forms of metallic chromium, trivalent chromium and hexavalent chromium. All chromium compounds are toxic, among which hexavalent chromium is the most toxic.

[0003] The current domestic chromium-containing disposal methods mainly include biological material adsorption, evaporation, precipitation, activated carbon adsorption, ion exchange resin, electrodialysis, etc., which are mainly used for repairing heavy metal pollution industrial objects, recovering precious metals, enriching metals and removing heavy metal ions from water bodies. These forms of treatment have the problems of difficult treatment, high cost, low efficiency and secondary pollution.

[0004] Therefore, the present application provides a chromium-containing waste treatment method, which disposes chromium-containing waste by cement kiln to realize harmless disposal of chromium-containing waste. SUMMARY

[0005] The purpose of the present application is to provide a chromium-containing waste treatment method, which disposes chromium-containing waste by cement kiln, controls the treatment process through three links of front-end compatibility, middle-end control and rear-end adjustment, ensures the safe and harmless disposal of chromium-containing hazardous waste, and makes the cement product qualified and environmentally friendly, so as to ultimately realize the harmless disposal of chromium-containing waste.

[0006] The present application provides a chromium-containing waste treatment method, and the treatment steps are as follows: S1. Pretreatment and compatibility stage The chromium-containing waste is classified into three categories according to the content of Cr element, and is stored and homogenized, where the content of Cr element <1000 ppm is low, 1000 (including) -2000 ppm is medium, 2000 (including) -4000 ppm is high, and more than 4000 ppm is controlled not to enter the factory; The homogenized three types of waste are detected for composition, mixed in proportion based on the detection results, mixed chromium-containing waste is formed, and homogenized again to control the chlorine content to be 1.0%-1.5% and the Cr content to be ≤3000 ppm; The dosage of the mixed waste is calculated according to the addition amount calculation formula, and is added into the cement kiln by belt conveying, spray gun or pumping; S2. Co-disposal stage Real-time monitoring of cement kiln production data, dynamic adjustment of K / Cr element ratio, and dynamic adjustment of production parameters and solid waste addition amount to ensure that the calcination effect meets the environmental protection requirements; S3. Cement grinding stage In the cement grinding process, the composite reducing agent is added based on the co-processing condition, the Cr 6+ in the cement is reduced to Cr 3+ , the content of Cr 6+ is reduced, and the quality of the final cement product is ensured.

[0007] Further, in step S1, the formula for calculating the mixing amount of the chromium-containing waste is: Mixing amount = coefficient mu x raw material amount x (national standard value - background value) / (measured value - national standard value); In the formula: Coefficient mu: quality insurance coefficient, generally set to 0.65-0.75; Raw material amount: total amount of cement raw material to be mixed; National standard value: upper limit of the allowable content of Cr 6+ in the national standard; Background value: initial content of Cr 6+ in the cement raw material; Measured value: expected content of Cr 6+ in the cement after mixing the chromium-containing waste.

[0008] Further, in step S1, the homogenization method of the chromium-containing waste adopts any one of the herringbone distribution method, the wave distribution method and the horizontal inclined layer stacking method.

[0009] Further, in step S3, the composite reducing agent is composed of at least two of ferrous sulfate heptahydrate, mineral powder, calcium sulfite and complex reducing agent.

[0010] Further, in step S3, the adding position of the composite reducing agent includes at least one of the positions of the gypsum warehouse, the cement grinding aid warehouse, the cement fine powder return pipe and the mineral powder grinding position.

[0011] Further, in step S3, the adding process of the composite reducing agent is a combined way of liquid spraying and powder mixing.

[0012] Further, in step S2, in the cement kiln co-processing process, the mass ratio of K / Cr elements is controlled to be 1:1.2 ~ 1:1.4, and the content of K2O in the clinker is not higher than 0.7%.

[0013] The beneficial effects of the present application are: The application provides a chromium-containing waste treatment method, in the pretreatment and compounding stage, the chromium-containing waste is classified and stored separately for homogenization, and based on component detection, mixed chromium-containing waste is formed by compounding and mixing in proportion, and then the addition amount of the mixed waste is calculated according to the addition amount calculation formula, and is added into the cement kiln; in the co-disposal stage, the cement kiln production data is monitored in real time, the K / Cr element mass ratio is dynamically adjusted, the production parameters and the solid waste addition amount are adjusted; in the cement grinding stage, the composite reducing agent is used as a backup means, and is added according to the co-disposal situation, Cr 6+ is reduced to Cr 3+ in the cement, the Cr 6+ content is reduced, and the quality of the final cement product is ensured; the treatment method provided by the application ensures the safe and harmless disposal of chromium-containing hazardous waste, qualified cement products and green environmental protection through the control of the three links of front-end compounding, middle control and rear adjustment, so that the harmless disposal of chromium-containing waste is finally realized. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor.

[0015] Figure 1 A- gypsum warehouse, B- cement grinding aid warehouse, C- cement grinding fine powder return pipe, D- mineral powder grinding position. DETAILED DESCRIPTION

[0016] In order to facilitate the understanding of the present application, the following will be a more comprehensive description of the present application by embodiments, and the following gives the preferred embodiments of the present application. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. Any modification or equivalent replacement of the technical solutions of the present application without creative result will also be within the scope of protection of the present application.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0018] The numerical values disclosed in the embodiments of the present application are approximate values, not definite values. Within the error or experimental conditions, all values within the error range can be included without being limited to the specific numerical values disclosed in the embodiments of the present application.

[0019] Unless otherwise specifically indicated, all materials, reagents, solvents, and the like used in the present application are available from commercial vendors or are prepared by conventional methods.

[0020] The embodiment provides a chromium-containing waste treatment method, and treatment steps are as follows: S1. Pretreatment and compounding stage The chromium-containing waste is classified into three categories of high, medium and low according to the content of Cr element, and is stored and homogenized, specifically, the content of Cr element <1000 ppm is low, 1000 (including) -2000 ppm is medium, 2000 (including) -4000 ppm is high, and more than 4000 ppm is controlled not to enter the factory; The homogenized three types of waste are detected for composition, mixed according to the proportion based on the detection results, mixed chromium-containing waste is formed, and is homogenized again, the chlorine content is controlled to be 1.0%-1.5%, and the Cr content is ≤2500 ppm; The addition amount of the mixed waste is calculated according to the addition amount calculation formula, and is added into the cement kiln by means of belt conveying, spray gun or pumping; Specifically, in this step, the compounding of the chromium-containing waste is divided into three levels, wherein the first level is to control from the source, to make a solid waste entry plan, and to ensure that the harmful components of the solid waste entering the factory do not exceed the disposal capacity of the cement kiln; the second level is to divide the solid waste into three categories of high, medium and low according to the content of Cr element, to store and homogenize by calculation through the grab of the travelling crane, and to clearly stipulate that the homogenized solid waste can enter the kiln, and the homogenized material is detected, and the detection results are used for laboratory proportioning and adjustment in the disposal process of the cement kiln; the third compounding mainly controls and calculates the addition amount of the kiln solid waste, the addition amount of the homogenized solid waste is calculated by the method and standard stipulated in HJ-662 and GB30760 national standards, and the addition is strictly added according to the standard, so that the product quality is controlled.

[0021] Specifically, in the embodiment, the waste data entering the factory and the detection classification are shown in Table 1 as follows: Table 1 Enterprise Code Solid Waste Category Total Cr / ppm Cr Introduction Amount Inbound No. A Bulk (336-064-17) 4350 0.321 High B Bulk (336-062-17) 3520 0.229 High C Bulk (336-062-17) 2843 0.174 Medium D Bulk (772-003-18) Slag 1192 0.078 Medium E Bulk (802-006-49) 2053 0.183 Medium F Bulk (336-064-17) 873 0.003 Low G Bulk (336-064-17) 356 0.000 Low H Bulk (336-062-17) 306 0.062 Low I Ton Bag (271-003-02) Activated Carbon 231 0.002 Low J Ton Bag (772-003-18) Slag 98 0.060 Low Specifically, in the embodiment, the detection results after the second compounding and homogenization are shown in Table 2 as follows: Table 2

[0022] Specifically, in the embodiment, based on the 5000t / d production line, the addition amount calculation of the mixed chromium-containing waste after the third compounding is shown in Table 3 as follows: Table 3

[0023] In this step, the addition amount calculation formula of the mixed chromium-containing waste is: Mixing amount = coefficient μ × material amount × (national standard value - background value) / (measured value - national standard value); In the formula: Coefficient μ: mass insurance coefficient, generally set to 0.65-0.75; Raw material amount: total amount of cement raw material to be mixed; National standard value: upper limit of allowable content of Cr in national standard (HJ-662, GB-30485); 6+ Background value: initial content of Cr in cement raw material; 6+ Measured value: expected content of Cr in cement after mixing with mixed chromium-containing waste. 6+

[0024] S2. Collaborative disposal stage Real-time monitoring of cement kiln production data, dynamic adjustment of production parameters and solid waste mixing amount, to ensure that the calcination effect meets environmental protection requirements; Specifically, in this step, the mass ratio of K / Cr elements is between 1:1.2 and 1:1.4, and the K2O content in clinker is not higher than 0.6%.

[0025] In this step, the heavy metal ions in the mixed solid waste added externally can be solid-solubilized to a certain extent in the mineral phase. The radius difference between Cr 3+ and Fe 3+ is less than 15%, which can be replaced to form a substitution-type solid solution; the ionic Pauling radius of Cr 3+ and the ionic Pauling radius of Ca 3+ are both greater than 15%, so they can enter these hollow positions in the form of interstitials for solid solution; a small part of Cr 3+ replaces Si 4+ in dicalcium silicate and tricalcium silicate and enters the interior of the mineral crystal lattice during high-temperature calcination; at the same time, Cr2O3 reacts with the abundant CaO in the cement kiln to form calcium chromate, i.e. the Cr2O3 formed by the reaction and the Cr2O3 that replaces silicon atoms in the crystal lattice are mainly combined in the hydrated calcium silicate gel (C-S-H) to achieve solidification; In this step, during the calcination process in the cement kiln, by establishing a quality monitoring system and a feedback adjustment mechanism, an internal control index for water-soluble chromium in cement is developed for linkage control, real-time monitoring of production data, reporting of abnormal mechanisms, and immediate adjustment of production parameter and solid waste mixing amount.

[0026] S3. Cement grinding stage During the cement grinding process, a composite reducing agent is added according to the collaborative disposal situation to reduce Cr 6+ in cement to Cr 3 + ​​​, reduce the content of Cr 6+ , ensure the quality of the final cement product.

[0027] Specifically, in the embodiment, the composite reducing agent is arranged at the following positions respectively: A next to the gypsum warehouse, a new storage warehouse is built, where the powdered composite reducing agent is added, weighed by a weighing scale, and then enters the cement mill together with the gypsum through the belt conveyor into the cement mill for grinding; B next to the cement grinding aid warehouse, where the liquid composite reducing agent is added, which is sprayed into the cement mill through the conveying pipeline together with the grinding aid for reaction; C at the cement fine powder return pipe, where the powdered composite reducing agent is added, which enters the cement mill from the cement fine powder return pipe through the weighing scale and the feeder chute for grinding and reaction.

[0028] Specifically, in the step, 15KG ferrous sulfate (about 0.1‰ to 0.12‰) is added at A; 7KG sodium thiosulfate solution (about 0.03‰ to 0.06‰, whether to add or not is determined according to the situation) is added at B; and 8KG ferrous sulfate (whether to add or not is determined according to the situation, about 0.03‰ to 0.06‰) is added at C.

[0029] After testing, the water-soluble Cr 6+ content of the final cement product is 6.2.

[0030] In summary, the chromium-containing waste treatment method provided by the application, in the pretreatment and compounding stage, the chromium-containing waste is classified and stored separately and homogenized, and based on the component detection, the mixed chromium-containing waste is compounded and mixed in proportion, and then the addition amount of the mixed waste is calculated according to the addition amount calculation formula, and is added into the cement kiln; in the co-disposal stage, the cement kiln production data is monitored in real time, and the production parameters and the solid waste addition amount are dynamically adjusted; in the cement grinding stage, the composite reducing agent is added as a backup measure to reduce the Cr 6+ in the cement to Cr 3+ , reduce the content of Cr 6+ , and ensure the quality of the final cement product; the treatment method provided by the application ensures the safe and harmless disposal of chromium-containing hazardous waste, the qualified cement product, and the green environmental protection through the control of the three links of the front compounding, the middle control and the rear adjustment, so that the harmless disposal of the chromium-containing waste is finally realized.

[0031] The above is only a preferred embodiment of the application and is not intended to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A method for treating chromium-containing waste, characterized in that: The processing steps are as follows: S1. Pretreatment and compatibility stage Chromium-containing wastes are classified into three categories according to their Cr content: high, medium, and low, and then stored separately for homogenization treatment; The three types of waste after homogenization are tested for composition, and based on the test results, they are mixed in proportion to form mixed chromium-containing waste, which is then homogenized again to control the chlorine content to 1.0%~1.5% and the Cr content to ≤3000 ppm; Calculate the dosage of mixed waste according to the dosage calculation formula and add it into the cement kiln; S2. Co-processing stage Real-time monitoring of cement kiln production data, dynamic adjustment of K / Cr element mass ratio, and dynamic adjustment of production parameters and solid waste addition amount to ensure that the calcination effect meets environmental protection requirements; S3. Cement grinding stage In the cement grinding process, composite reducing agent is added based on the synergistic treatment situation to reduce the Cr in cement. 6+ Reduction to Cr 3+ , reduce Cr 6+ content to ensure the quality of the final cement product.

2. The method for treating chromium-containing waste according to claim 1, wherein: In step S1, the formula for calculating the amount of mixed chromium-containing waste is: Addition amount = coefficient μ × raw material amount × (national standard value - background value) / (measured value - national standard value); Where: Coefficient μ: quality insurance coefficient, set to 0.65-0.75; Raw meal quantity: the total amount of cement raw meal to be added; National standard value: Cr in national standard 6+ The upper limit of the permissible content; Background value: Cr in cement raw material 6+ Initial content of Measured value: Cr in cement after adding mixed chromium-containing waste 6+ expected content.

3. The method for treating chromium-containing waste according to claim 1, wherein: In step S1 , the homogenization method for the mixed chromium-containing waste is any one of a herringbone distribution method, a wave distribution method, and a horizontal inclined layer stacking method.

4. The method for treating chromium-containing waste according to claim 1, wherein: The composite reducing agent in step S3 is composed of a mixture of at least two of ferrous sulfate heptahydrate, calcium sulfite, sodium borohydride, sodium hexametaphosphate, and a copper-containing metal complexing agent.

5. The method for treating chromium-containing waste according to claim 1, wherein: The addition location of the composite reducing agent in step S3 includes at least one of the following: beside the gypsum warehouse, beside the cement grinding aid warehouse, the cement ground powder return pipe, and the mineral powder grinding location.

6. The method for treating chromium-containing waste according to claim 1, wherein: The process of adding the composite reducing agent in step S3 is a combined method of liquid spraying and powder mixing.

7. The method for treating chromium-containing waste according to claim 1, wherein: In step S2, during the cement kiln co-processing process, the K / Cr element mass ratio is controlled to be between 1:1.2 and 1:1.4, and the K2O content in the clinker is not higher than 0.7%.

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