A system for preparing chromium oxide powder by using chromium-containing wastewater as raw material

Abstract

The utility model discloses a system is prepared with containing chromium wastewater as raw material chromic oxide powder relates to sewage treatment technical field, including pH adjusting mechanism, enrichment transformation mechanism, analytical solution concentration drying mechanism, calcining mechanism, containing chromium wastewater is through pH adjusting mechanism, containing chromium wastewater pH is adjusted to weak acidity, and the containing chromium wastewater after pH adjustment enters enrichment transformation mechanism, and resin adsorption saturation is with ammonia water analysis, and analytical solution goes analytical solution concentration drying mechanism processing. The resin after analysis can go adsorption again after acid transformation. In analytical solution concentration drying mechanism, through evaporation concentration and drying, can obtain the mixed powder of ammonium chromate and ammonium dichromate. In subsequent calcining mechanism, the mixed powder obtained above is carried out high temperature calcining treatment, can obtain chromic oxide powder with high purity, uniform particle size, and the industry standard requirement is met, realizes the effective utilization of chromium resources in containing chromium wastewater, and reduces the preparation difficulty of pigment grade chromic oxide.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment technology, and in particular to a system for preparing chromium oxide powder using chromium-containing wastewater as raw material. Background Technology

[0002] Chromium trioxide (Cr2O3) plays a crucial role in the chromium salt chemical industry as a chemical raw material. Cr2O3 is a green crystalline substance, resistant to high temperatures and corrosion, and exhibits good lightfastness and chemical stability. Its product quality is mainly divided into two categories: industrial grade and pigment grade, each with different technical requirements in different application fields. Industrial grade Cr2O3 is primarily used in lower-end fields such as metallurgy and refractory materials, while pigment grade Cr2O3, also known as chromium oxide green, is a high-end product, widely used in coatings, inks, and other fields.

[0003] Currently, Cr2O3 in China is mainly produced using the thermal decomposition method of chromic anhydride (CrO3). This process is complex, involves harsh operating conditions, and generates dust containing hexavalent chromium during roasting, posing a significant environmental hazard. The thermal decomposition method using sodium dichromate and ammonium sulfate is the primary process for producing chromium oxide green abroad. This process produces a wide variety of products and does not generate harmful gases. However, the products produced have a high sulfur content, and the byproduct, sodium chromium sulfate, is difficult to recover and reuse.

[0004] Chromium metal possesses excellent corrosion resistance, maintains its luster for a long time, and exhibits good wear resistance, heat resistance, and high hardness. Therefore, chromium metal has wide applications in electroplating, such as hard chromium plating, decorative chromium plating, and zinc chromium passivation. During the electroplating process, due to rinsing of the plated parts, disposal of the plating bath, and replacement and cleaning of the filter cloth and filter element of the plating bath filter, a certain amount of chromium-containing wastewater is generated. The main pollutants in chromium-containing wastewater include Cr2O72-, Cr3+, Zn2+, Cu2+, Fe3+, and Ni2+. The conventional method for treating chromium wastewater is reduction neutralization flocculation. First, under acidic conditions, a reducing agent is added to reduce Cr2O72- to Cr3+. Then, alkali is added to adjust the pH value of the wastewater, causing the metal ions to be converted into their corresponding hydroxide precipitates for removal. However, this method yields chromium sludge with a complex composition and low chromium content, making it difficult to reuse.

[0005] As can be seen from the above, pigment-grade chromium oxide has high requirements and is difficult to prepare, while chromium-containing wastewater contains a large amount of chromium resources, which are not being effectively utilized. Utility Model Content

[0006] The purpose of this invention is to provide a system for preparing chromium oxide powder using chromium-containing wastewater as raw material, in order to solve the problems existing in the prior art. By using chromium-containing wastewater as raw material, the system effectively utilizes waste chromium resources, and the obtained chromium oxide has high purity and uniform particle size, meeting industry standard requirements.

[0007] To achieve the above objectives, this utility model provides the following solution: This utility model provides a system for preparing chromium oxide powder using chromium-containing wastewater as raw material, comprising: The pH adjustment mechanism includes a chromium-containing wastewater collection tank, a pH-adjusting acid and alkali collection tank, a pH-adjusting reaction tank, a filter press, and a filter press permeate collection tank connected in sequence. The chromium-containing wastewater collection tank includes an inlet and an outlet. The inlet is used to receive chromium-containing wastewater, and the outlet is connected to the inlet of the pH-adjusting reaction tank. The pH-adjusting acid and alkali collection tank is used to supply acid and alkali reagents to the pH-adjusting reaction tank. The outlet of the pH-adjusting reaction tank is connected to the filter press, and the outlet of the filter press is connected to the inlet of the filter press permeate collection tank. The enrichment and transformation mechanism includes a chromium ion exchange column, a wastewater treatment system, an eluent preparation tank, a transformation dilute acid preparation tank, an eluent collection tank, and a multi-media filter. The wastewater outlet of the filter press permeate collection tank is connected to the inlet of the multi-media filter, the outlet of the multi-media filter is connected to the inlet of the chromium ion exchange column, the chromium ion exchange column is also connected to the eluent preparation tank and the transformation dilute acid preparation tank, and the outlet of the chromium ion exchange column is connected to the inlet of the wastewater treatment system and the inlet of the eluent collection tank, respectively. The eluent concentration and drying mechanism is connected to the outlet of the eluent collection tank. The eluent passes through the eluent concentration and drying mechanism to obtain a mixed powder of ammonium chromate and ammonium dichromate. The calcination mechanism is used to calcine a mixture of ammonium chromate and ammonium dichromate at high temperature to obtain chromium oxide powder.

[0008] In some embodiments, a chromium-containing wastewater booster pump is provided between the chromium-containing wastewater collection tank and the pH-adjusting reaction tank, and the wastewater from the chromium-containing wastewater collection tank is transported to the pH-adjusting reaction tank via the chromium-containing wastewater booster pump.

[0009] In some embodiments, a pH-adjusting acid-base collection tank and a pH-adjusting reaction tank are provided with a pH-adjusting acid-base booster pump, and the acid-base reagents in the pH-adjusting acid-base collection tank are transported to the pH-adjusting reaction tank via the pH-adjusting acid-base booster pump.

[0010] In some embodiments, a sodium dichromate suspension lift pump is provided between the pH adjustment reaction tank and the filter press. The sodium dichromate suspension formed in the pH adjustment reaction tank is transported to the filter press by the sodium dichromate suspension lift pump for solid-liquid separation to obtain filter press permeate and combined sludge.

[0011] In some embodiments, a filter press permeate collection tank and a multi-media filter are provided with a filter press permeate booster pump, and the wastewater in the filter press permeate collection tank is transported to the multi-media filter via the filter press permeate booster pump.

[0012] In some embodiments, the eluent preparation tank and the dilute acid preparation tank are respectively connected to the chromium ion exchange column via an eluent booster pump and a dilute acid booster pump. The ammonia solution in the ammonia preparation tank is transported to the chromium ion exchange column via the eluent booster pump, and the acid solution in the dilute acid preparation tank is transported to the chromium ion exchange column via the dilute acid booster pump.

[0013] In some embodiments, the chromium ion exchange column includes an eluent outlet and a resin outlet, the eluent outlet being connected to the eluent collection tank and the resin outlet being connected to the wastewater treatment system.

[0014] In some embodiments, the eluent concentration and drying mechanism includes an evaporation and concentration device and a spray drying device, wherein the inlet of the evaporation and concentration device is connected to the outlet of the eluent collection tank, and the outlet of the evaporation and concentration device is connected to the inlet of the spray drying device.

[0015] In some embodiments, the calcination mechanism includes a high-temperature calcination device, the inlet of which is connected to the outlet of the spray drying device.

[0016] The present invention achieves the following technical advantages over the prior art: This invention relates to a system for preparing chromium oxide powder from chromium-containing wastewater. The system includes a pH adjustment mechanism, an enrichment and transformation mechanism, a solution concentration and drying mechanism, and a calcination mechanism. The chromium-containing wastewater is adjusted to a weakly acidic pH in the pH adjustment mechanism to ensure that the hexavalent chromium exists only as dichromate ions. This weakly acidic condition also reduces the oxidizing power of dichromate ions, thus protecting the subsequent anion exchange resin. The pH-adjusted wastewater then enters the enrichment and transformation mechanism. After the resin becomes saturated, it is desorbed with ammonia water. The desorbed solution is then treated in the solution concentration and drying mechanism. The desorbed resin can be re-adsorbed after acid transformation. In the solution concentration and drying mechanism, a qualified mixed solution of ammonium chromate and ammonium dichromate is first evaporated and concentrated, then dried using a spray drying method to obtain a mixed powder of ammonium chromate and ammonium dichromate. In the subsequent calcination process, the mixed powder obtained above is subjected to high-temperature calcination to obtain chromium oxide powder with high purity, uniform particle size, and meeting industry standard requirements. This enables the effective utilization of chromium resources in chromium-containing wastewater and reduces the difficulty of preparing pigment-grade chromium oxide. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the system for preparing chromium oxide powder using chromium-containing wastewater as raw material in this utility model; In the diagram: 1. Chromium-containing wastewater collection tank; 2. pH-adjusting acid and alkali collection tank; 3. pH-adjusting reaction tank; 4. Filter press; 5. Combined sludge; 6. Filter press permeate collection tank; 7. Chromium ion exchange column; 8. Wastewater treatment system; 9. Eluent preparation tank; 10. Transformation dilute acid preparation tank; 11. Eluent collection tank; 12. Evaporation and concentration device; 13. Spray drying device; 14. High-temperature calcination device; 15. Multi-media filter; 16. Chromium-containing wastewater lift pump; 17. pH-adjusting acid and alkali lift pump; 18. Filter press permeate lift pump; 19. Eluent lift pump; 20. Transformation dilute acid lift pump; 21. Sodium dichromate suspension lift pump. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] The purpose of this invention is to provide a system for preparing chromium oxide powder using chromium-containing wastewater as raw material, so as to solve the problems existing in the prior art.

[0021] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] The system for preparing chromium oxide powder using chromium-containing wastewater as raw material in this embodiment is as follows: Figure 1 As shown, it includes: The pH adjustment mechanism includes a chromium-containing wastewater collection tank 1, a pH-adjusting acid and alkali collection tank 2, a pH-adjusting reaction tank 3, a filter press 4, and a filter press permeate collection tank 6 connected in sequence. The chromium-containing wastewater collection tank 1 includes an inlet and an outlet. The inlet is used to receive chromium-containing wastewater, and the outlet is connected to the inlet of the pH-adjusting reaction tank 3. The pH-adjusting acid and alkali collection tank 2 is used to supply acid and alkali reagents to the pH-adjusting reaction tank 3. The outlet of the pH-adjusting reaction tank 3 is connected to the filter press 4, and the outlet of the filter press 4 is connected to the inlet of the filter press permeate collection tank 6. The enrichment and transformation mechanism includes a chromium ion exchange column 7, a wastewater treatment system 8, an eluent preparation tank 9, a transformation dilute acid preparation tank 10, an eluent collection tank 11, and a multi-media filter 15. The wastewater outlet of the filter press permeate collection tank 6 is connected to the inlet of the multi-media filter 15, and the outlet of the multi-media filter 15 is connected to the inlet of the chromium ion exchange column 7. The chromium ion exchange column 7 is also connected to the eluent preparation tank 9 and the transformation dilute acid preparation tank 10. The outlet of the chromium ion exchange column 7 is connected to the inlet of the wastewater treatment system 8 and the inlet of the eluent collection tank 11, respectively. The eluent concentration and drying mechanism is connected to the outlet of the eluent collection tank 11. The eluent passes through the eluent concentration and drying mechanism to obtain a mixed powder of ammonium chromate and ammonium dichromate. The calcination unit is used to calcine a mixture of ammonium chromate and ammonium dichromate powders at high temperature to obtain chromium oxide powder.

[0023] In some embodiments, a chromium-containing wastewater lift pump 16 is provided between the chromium-containing wastewater collection tank 1 and the pH adjustment reaction tank 3, and the wastewater from the chromium-containing wastewater collection tank 1 is transported to the pH adjustment reaction tank 3 via the chromium-containing wastewater lift pump 16.

[0024] In some embodiments, a pH adjustment acid-base collection tank 2 and a pH adjustment reaction tank 3 are provided with a pH adjustment acid-base booster pump 17, and the acid and base reagents in the pH adjustment acid-base collection tank 2 are transported to the pH adjustment reaction tank 3 by the pH adjustment acid-base booster pump 17.

[0025] In some embodiments, a sodium dichromate suspension lift pump 21 is installed between the pH adjustment reaction tank 3 and the filter press 4. The sodium dichromate suspension formed in the pH adjustment reaction tank 3 is transported to the filter press 4 by the sodium dichromate suspension lift pump 21 for solid-liquid separation, to obtain filter press 4 permeate and integrated sludge 5.

[0026] In some embodiments, a filter press permeate collection tank 6 and a multi-media filter 15 are provided with a filter press permeate booster pump 18, and the wastewater in the filter press permeate collection tank 6 is transported to the multi-media filter 15 by the filter press permeate booster pump 18.

[0027] In some embodiments, an eluent preparation tank 9 and a dilute acid preparation tank 10 are respectively connected to the chromium ion exchange column 7 via an eluent booster pump 19 and a dilute acid booster pump 20. The ammonia solution in the ammonia preparation tank is transported to the chromium ion exchange column 7 via the eluent booster pump 19, and the acid solution in the dilute acid preparation tank is transported to the chromium ion exchange column 7 via the dilute acid booster pump 20.

[0028] In some embodiments, the chromium ion exchange column 7 includes an eluent outlet and a resin outlet, with the eluent outlet connected to an eluent collection tank 11 and the resin outlet connected to a wastewater treatment system 8.

[0029] In some embodiments, the eluent concentration and drying mechanism includes an evaporation and concentration device 12 and a spray drying device 13. The inlet of the evaporation and concentration device 12 is connected to the outlet of the eluent collection tank 11, and the outlet of the evaporation and concentration device 12 is connected to the inlet of the spray drying device 13.

[0030] In some embodiments, the calcination mechanism includes a high-temperature calcination device 14, the inlet of which is connected to the outlet of the spray drying device 13.

[0031] Working principle: The wastewater from the chromium-containing wastewater collection tank 1 is pumped to the pH adjustment reaction tank 3 via the chromium-containing wastewater lift pump 16 to adjust its pH value to weakly acidic. The pH adjustment reaction tank uses acid and alkali collection tank 2 to deliver acid and alkali reagents to achieve the acid-alkali adjustment operation. After the reaction in the pH adjustment reaction tank 3 is completed, the weakly acidic wastewater is pumped to the filter press 4 via the sodium dichromate suspension lift pump 21 for solid-liquid separation to obtain filter press 4 permeate and comprehensive sludge 5. The filter press 4 permeate is then pumped to the filter press permeate collection tank 6.

[0032] Wastewater from filter press permeate collection tank 6 is pumped to multi-media filter 15 via filter press permeate booster pump 18. The outlet of multi-media filter 15 is connected to the inlet of chromium ion exchange column 7. After passing through chromium ion exchange column 7, hexavalent chromium ions are exchanged onto the resin using the resin's selective separation characteristics. The effluent after exchange is discharged into wastewater treatment system 8 for further treatment. When the resin in chromium ion exchange column 7 becomes saturated, it is regenerated using ammonia solution. Specifically, an ammonia solution of suitable concentration is prepared in an ammonia preparation tank and pumped to chromium ion exchange column 7 via eluent booster pump 19. The eluent flowing out of the outlet (a mixed solution of ammonium chromate and ammonium dichromate) enters eluent collection tank 11 and then enters the eluent concentration and drying mechanism. The resin after eluent exchange is a hydroxide-type resin, which can be re-adsorbed after acid treatment and transformation. Specifically, an acid solution of suitable concentration is prepared in a dilute acid preparation tank and pumped to chromium ion exchange column 7 via transformation dilute acid booster pump 20. The resin effluent is discharged into wastewater treatment system 8 for further treatment.

[0033] The eluent, consisting of a mixed solution of ammonium chromate and ammonium dichromate in the eluent collection tank 11, enters the evaporation and concentration device 12 for evaporation and concentration. The concentrated mother liquor is then spray-dried by the spray drying device 13 to obtain ammonium chromate and ammonium dichromate crystalline powders. The evaporation and concentration temperature is set to 80~110℃, and the specific gravity of the concentrated liquid at the end of the evaporation and concentration is preferably 1.4~1.5 g / cm³. The atomization method used for spray drying is centrifugal atomization or pressure atomization. The spray drying time is preferably 0.5~3 hours.

[0034] The spray-dried ammonium chromate and ammonium dichromate mixed crystal powder is calcined at high temperature in a high-temperature calcination apparatus 14 to obtain chromium oxide powder with high purity, uniform particle size, and meeting industry standards. The calcination temperature is set to 700~900℃, and the calcination time is set to 1~3h.

[0035] This utility model uses specific examples to illustrate its principles and implementation methods. The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the idea of ​​this utility model. In summary, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A system for preparing chromium oxide powder using chromium-containing wastewater as raw material, characterized in that, include: The pH adjustment mechanism includes a chromium-containing wastewater collection tank, a pH-adjusting acid and alkali collection tank, a pH-adjusting reaction tank, a filter press, and a filter press permeate collection tank connected in sequence. The chromium-containing wastewater collection tank includes an inlet and an outlet. The inlet is used to receive chromium-containing wastewater, and the outlet is connected to the inlet of the pH-adjusting reaction tank. The pH-adjusting acid and alkali collection tank is used to supply acid and alkali reagents to the pH-adjusting reaction tank. The outlet of the pH-adjusting reaction tank is connected to the filter press, and the outlet of the filter press is connected to the inlet of the filter press permeate collection tank. The enrichment and transformation mechanism includes a chromium ion exchange column, a wastewater treatment system, an eluent preparation tank, a transformation dilute acid preparation tank, an eluent collection tank, and a multi-media filter. The wastewater outlet of the filter press permeate collection tank is connected to the inlet of the multi-media filter, the outlet of the multi-media filter is connected to the inlet of the chromium ion exchange column, the chromium ion exchange column is also connected to the eluent preparation tank and the transformation dilute acid preparation tank, and the outlet of the chromium ion exchange column is connected to the inlet of the wastewater treatment system and the inlet of the eluent collection tank, respectively. The eluent concentration and drying mechanism is connected to the outlet of the eluent collection tank. The eluent passes through the eluent concentration and drying mechanism to obtain a mixed powder of ammonium chromate and ammonium dichromate. The calcination mechanism is used to calcine a mixture of ammonium chromate and ammonium dichromate at high temperature to obtain chromium oxide powder.

2. The system for preparing chromium oxide powder from chromium-containing wastewater according to claim 1, characterized in that: A chromium-containing wastewater lift pump is installed between the chromium-containing wastewater collection tank and the pH adjustment reaction tank, and the wastewater from the chromium-containing wastewater collection tank is transported to the pH adjustment reaction tank via the chromium-containing wastewater lift pump.

3. The system for preparing chromium oxide powder from chromium-containing wastewater according to claim 1, characterized in that: A pH-adjusting acid-base collection tank is provided between the pH-adjusting acid-base booster pump, and the acid-base reagents in the pH-adjusting acid-base collection tank are transported to the pH-adjusting acid-base booster pump.

4. The system for preparing chromium oxide powder from chromium-containing wastewater according to claim 1, characterized in that: A sodium dichromate suspension lift pump is installed between the pH adjustment reaction tank and the filter press. The sodium dichromate suspension formed in the pH adjustment reaction tank is transported to the filter press by the sodium dichromate suspension lift pump for solid-liquid separation to obtain filter press permeate and integrated sludge.

5. The system for preparing chromium oxide powder from chromium-containing wastewater according to claim 4, characterized in that: A filter press permeate collection tank is provided between the filter press permeate collection tank and the multi-media filter, and the wastewater in the filter press permeate collection tank is transported to the multi-media filter via the filter press permeate collection tank.

6. The system for preparing chromium oxide powder from chromium-containing wastewater according to claim 1, characterized in that: The eluent preparation tank and the dilute acid preparation tank are respectively connected to the chromium ion exchange column by an eluent booster pump and a dilute acid booster pump. The ammonia solution in the ammonia preparation tank is transported to the chromium ion exchange column by the eluent booster pump, and the acid solution in the dilute acid preparation tank is transported to the chromium ion exchange column by the dilute acid booster pump.

7. The system for preparing chromium oxide powder from chromium-containing wastewater according to claim 1, characterized in that: The chromium ion exchange column includes an eluent outlet and a resin outlet. The eluent outlet is connected to the eluent collection tank, and the resin outlet is connected to the wastewater treatment system.

8. The system for preparing chromium oxide powder from chromium-containing wastewater according to claim 1, characterized in that: The eluent concentration and drying mechanism includes an evaporation concentration device and a spray drying device. The inlet of the evaporation concentration device is connected to the outlet of the eluent collection tank, and the outlet of the evaporation concentration device is connected to the inlet of the spray drying device.

9. The system for preparing chromium oxide powder from chromium-containing wastewater according to claim 8, characterized in that: The calcination mechanism includes a high-temperature calcination device, the inlet of which is connected to the outlet of the spray drying device.

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