阅读说明：本技术 一种高纯硝酸银的环保高效生产方法 (Environment-friendly efficient production method of high-purity silver nitrate ) 是由 柳忠琪 周也涛 张圣欢 林松 彭戴 于 2020-06-17 设计创作，主要内容包括：本发明公开了一种高纯硝酸银的环保高效生产方法,先通过银锭与硝酸反应得到硝酸银溶液,然后净化硝酸银溶液,再依次经过减压高效蒸发、高效结晶、固液分离、干燥和破碎包装,800～850kg银锭从进入生产线开始22～22.5 h即可得到1150～1210kg高纯硝酸银晶体成品；本发明方法利用双氧水吸收氮氧化物变成硝酸循环利用,除杂剂除杂后经负压滤芯与正压滤芯结合过滤,高效减压蒸发后利用气动隔膜泵与真空负压相结合的抽滤方式实现硝酸银固液高效分离,相较现有技术,本发明的高纯硝酸银生产制备方法具有环保、高效、成本低、质量高的特点。(The invention discloses an environment-friendly efficient production method of high-purity silver nitrate, which comprises the steps of firstly reacting silver ingots with nitric acid to obtain a silver nitrate solution, then purifying the silver nitrate solution, and then sequentially carrying out reduced-pressure efficient evaporation, efficient crystallization, solid-liquid separation, drying, crushing and packaging, wherein 1150-850 kg of silver ingots are subjected to 22-22.5 hours from the time when the silver ingots enter a production line to obtain 1150-1210 kg of high-purity silver nitrate crystal finished products; according to the method, nitric oxide is changed into nitric acid for recycling by absorbing hydrogen peroxide, the impurity removing agent is subjected to impurity removal and then is filtered by combining a negative pressure filter element and a positive pressure filter element, and after high-efficiency pressure reduction evaporation, the solid-liquid high-efficiency separation of silver nitrate is realized by using a suction filtration mode combining a pneumatic diaphragm pump and vacuum negative pressure.)

1. An environment-friendly and efficient production method of high-purity silver nitrate is characterized by comprising the following steps: comprises the steps of

a) Preparation of silver nitrate solution

a1) Taking 800-850 kg of silver ingots, ultrasonically cleaning and airing, and then sequentially washing with high-purity water, cleaning with acid liquor with the concentration of 3-5% and cleaning with alkali liquor with the concentration of 3-5%, so as to remove stains on the surfaces of the silver ingots;

a2) putting the dried silver ingot into a silver dissolution reaction kettle, adding 60-80L of high-purity water, adding 565-610L of analytically pure nitric acid with the concentration of 65-68%, and heating at the temperature of 85-110 ℃ to obtain a silver nitrate solution;

a3) adding hydrogen peroxide to absorb nitrogen oxides generated in the reaction process of silver ingots and analytically pure nitric acid, and then adding sodium hydroxide and urea as absorbents to ensure that waste gas is fully absorbed and discharged after reaching the standard;

b) purifying silver nitrate solution

b1) Transferring the silver nitrate solution into an impurity removal kettle in vacuum, heating to 80-85 ℃, adding an impurity removal agent, stirring for 1-1.5 h, standing for 0.5-1 h, performing suction filtration to a silicon carbide filter, performing negative pressure filtration, and transferring the filtrate to a neutralization tank;

b2) adding pure nitric acid, and adjusting the pH value of a silver nitrate solution in the tank to 1.0-2.0;

b3) filtering the silver nitrate solution to a polytetrafluoroethylene filter by a pneumatic diaphragm pump;

c) reduced pressure high efficiency evaporation

The silver nitrate solution enters an evaporation tank to finish reduced pressure evaporation within 2.2-2.5 h;

d) high efficiency crystallization

Transferring the silver nitrate solid-liquid mixture into a crystallizing tank filled with chilled water, and completing the crystallization of the silver nitrate within 2 hours;

e) solid-liquid separation

Feeding the completely crystallized silver nitrate solid-liquid mixture into a solid-liquid separation tank, and performing positive pressure suction filtration and negative pressure suction filtration by using a pneumatic diaphragm pump to realize solid-liquid separation within 2-2.2 h;

f) drying

Putting the silver nitrate solid into an oven, and drying at 94-98 ℃ for 8-9 h;

g) broken package

And crushing the silver nitrate solid by a crusher, and then packaging the silver nitrate solid in automatic packaging equipment to obtain 1150-1210 kg of high-purity silver nitrate finished product.

2. The method for environment-friendly and high-efficiency production of high-purity silver nitrate according to claim 1, characterized in that the diameter of the filtration pore of the silicon carbide filter in the step b 1) is less than or equal to 1 μm; the diameter of the filtration pore of the polytetrafluoroethylene filter in the step b 3) is less than or equal to 0.45 μm.

3. The method for environment-friendly and high-efficiency production of high-purity silver nitrate according to claim 1, wherein the evaporation concentration in the step c) is performed at a negative pressure of-70 to-90 KPa and a temperature of 70 to 90 ℃.

4. The method for environment-friendly and high-efficiency production of high-purity silver nitrate according to claim 1, characterized in that the solid-liquid separation tank in the step e) consists of a stainless steel filter screen, a pneumatic diaphragm pump and a vacuum system of-80 to-90 KPa.

Technical Field

The invention relates to a production method of silver nitrate, in particular to an environment-friendly high-efficiency production method of high-purity silver nitrate.

Background

Silver nitrate is used as a silver chemical product, is a production raw material and a foundation of other silver high-value-added products, and has wide application in the fields of mirror making, medicine, electroplating, superfine silver powder and the like. With the improvement of the product quality requirements of downstream industries, silver nitrate gradually develops towards high purification.

At present, the main method for preparing high-purity silver nitrate is a reaction process of adding nitric acid to dissolve silver, and then silver nitrate crystals are obtained through processes of impurity removal, filtration, evaporation, concentration, crystallization, centrifugation, drying, packaging and the like. During the reaction process of adding nitric acid to dissolve silver, a large amount of nitrogen oxide waste gas (NOx) is generated, and the main reaction is as follows:

2HNO₃(concentrated) + Ag = AgNO₃+H₂O+NO₂↑

4HNO₃(diluted) +3Ag =3AgNO₃+2H₂O+NO↑。

With NO and NO₂The main nitrogen oxide is an important reason for forming photochemical smog and acid rain, and poses great threat to human health and ecological environment, the common industrial treatment methods include reduction method, liquid absorption method, biological method, adsorption method and the like, from the aspects of investment and operation cost, environmental protection, absorption efficiency, long-term stability and the like, the liquid absorption method is most commonly applied in actual production at present, different absorption agents adopted by different absorption principles have different actual effects, and how to select the absorption agents is a difficult problem facing a plurality of enterprises.

In order to obtain high-purity silver nitrate, the silver nitrate solution needs to be purified and decontaminated to remove some solid impurities and Cu²⁺、Fe³⁺And the like metal impurity ions. In principle, solid impurities are removed by filtration, and impurity removing agents or metal impurity ions are removed by high-temperature impurity removal, so that the silver nitrate product meets the high-purity requirement. At present, most of production and preparation processes are low in purification and impurity removal efficiency.

Aiming at the evaporation and concentration process of the silver nitrate solution, the evaporation pressure and temperature have great influence on the evaporation efficiency, and the proper pressure and temperature range is found, so that the efficiency of the evaporation and concentration process is facilitated, and the silver utilization rate of the evaporation process is reduced.

The solid-liquid mixture after the silver nitrate is fully crystallized is usually centrifugally dewatered by a centrifugal machine, the process efficiency is low, and the centrifugal machine running at a high speed has certain potential safety hazard.

In view of the problems in the prior art, it is necessary to design an environment-friendly and efficient method for preparing high-purity silver nitrate.

Disclosure of Invention

The invention aims to solve the technical problems of low efficiency, outstanding environmental protection problems, high cost, unstable quality and the like in the existing industrial production of high-purity silver nitrate, and provides an environment-friendly and high-efficiency production method of high-purity silver nitrate.

The technical scheme adopted by the invention for solving the technical problems is as follows: an environment-friendly and efficient production method of high-purity silver nitrate comprises the following steps

a) Reacting silver ingot with nitric acid to obtain silver nitrate solution

a1) Taking 800-850 kg of national standard No. 1 silver ingots as a batch, and removing stains on the surfaces of the silver ingots through a customized ultrasonic cleaning and airing system, high-purity water cleaning, acid liquor cleaning with the concentration of 3-5%, alkali liquor cleaning with the concentration of 3-5% and other processes in sequence;

a2) putting the cleaned and dried silver ingot into a silver dissolution reaction kettle, adding 60-80L of high-purity water, starting an automatic steam heating system, proportionally and gradually adding 565-610L of analytically pure nitric acid with the concentration of 65-68% at a constant speed, controlling the temperature to be within the range of 85-110 ℃ and heating to react to obtain a silver nitrate solution;

a3) hydrogen peroxide with a certain concentration range is added at the front end of the nitrogen oxide waste gas treatment system to absorb nitrogen oxide generated in the reaction process of silver ingots and analytically pure nitric acid, and absorption liquid (nitric acid) is recycled until the reaction is finished; urea and sodium hydroxide absorbent are added at the rear end of the waste gas treatment system for further absorption, so that the NOx emission concentration is always less than 150ppm, and the emission can reach the standard stably for a long time;

b) purifying silver nitrate solution

b1) Transferring the silver nitrate solution into an impurity removal kettle in vacuum, heating to 80-85 ℃, keeping, adding an impurity removal agent, stirring for 1-1.5 h, standing for 0.5-1 h, performing suction filtration to a silicon carbide filter, performing negative pressure filtration, and transferring the filtrate to a neutralization tank;

b2) adding a proper amount of superior pure nitric acid, and adjusting the pH value of the silver nitrate solution in the neutralization tank to 1.0-2.0;

b3) pumping the silver nitrate solution with the adjusted pH value through a pneumatic diaphragm pump, and filtering the silver nitrate solution to a polytetrafluoroethylene filter for filtration;

c) reduced pressure high efficiency evaporation

The silver nitrate solution after positive pressure and negative pressure combined filtration treatment enters an evaporation tank for reduced pressure evaporation, and evaporation is completed within 2.2-2.5 h;

d) high efficiency crystallization

When the high-efficiency evaporation is finished, transferring the silver nitrate solid-liquid mixture into a crystallizing tank filled with chilled water to complete cooling crystallization of the silver nitrate within 2 hours;

e) solid-liquid separation

Feeding the completely crystallized silver nitrate solid-liquid mixture into a solid-liquid separation tank, performing positive pressure suction filtration and negative pressure suction filtration by using a pneumatic diaphragm pump, realizing solid-liquid separation for 2-2.2 hours, and preparing the obtained silver nitrate solid for the next drying procedure;

f) drying

Putting the silver nitrate solid subjected to solid-liquid separation into an oven, and drying at 94-98 ℃ for 8-9 h to obtain a dried silver nitrate crystal;

g) broken package

And crushing the dried silver nitrate solid by a crusher, and then packaging the silver nitrate solid in automatic packaging equipment to obtain finished silver nitrate. And obtaining 1150-1210 kg of high-purity silver nitrate crystal finished product after 800-850 kg of silver ingots enter the production line for 22-22.5 hours, wherein the detection result shows that the finished product silver nitrate meets the high-grade purity standard in GB/T670-2007 chemical reagent silver nitrate.

In the environment-friendly and efficient production method of high-purity silver nitrate, the diameter of the filtration pore of the silicon carbide filter in the step b 1) is less than or equal to 1 mu m; the diameter of the filtration pore of the polytetrafluoroethylene filter in the step b 3) is less than or equal to 0.45 μm.

The environment-friendly and efficient production method of the high-purity silver nitrate is characterized in that the evaporation and concentration in the step c) are carried out at negative pressure of-70 to-90 KPa and at the temperature of 70-90 ℃.

The environment-friendly and efficient production method of high-purity silver nitrate comprises the step e) that the solid-liquid separation tank consists of a stainless steel filter screen, a pneumatic diaphragm pump and a-80 to-90 KPa vacuum system.

The invention has the beneficial effects that:

most of nitrogen oxide waste gas generated in the reaction process of silver ingots and nitric acid is converted into nitric acid by hydrogen peroxide for recycling, and a small amount of nitrogen oxide which is not absorbed is absorbed by alkali liquor and urea at the rear end of a waste gas system, so that the recycling of the nitric acid is realized, the discharge amount of waste gas and waste water is reduced, the treatment cost is reduced, and the method is more environment-friendly; in the filtering process after impurity removal of the silver nitrate solution, a filtering method of effectively combining negative pressure (less than or equal to 1 mu m) and positive pressure (less than or equal to 0.45 mu m filter element) is adopted, so that the filtering efficiency and the filtering quality are improved, and the product purity is higher; in the process of evaporating and concentrating the silver nitrate solution, negative pressure of 70-90 KPa and reduced pressure evaporation at the temperature of 70-90 ℃ are adopted, the efficiency of evaporating and concentrating the silver nitrate solution is improved, the effective utilization rate of silver is ensured (the total silver amount taken away by water vapor in the evaporation process is less than or equal to 1 thousandth), a mode of combining a pneumatic diaphragm pump and vacuum suction filtration of 80-90 KPa is adopted in the solid-liquid separation process of the fully crystallized silver nitrate, the high-efficiency separation of solid and liquid is realized, and the process is more efficient.

According to the production and preparation process of the silver nitrate, 1150-1210 kg of high-purity silver nitrate crystal finished products can be obtained within 24 hours from the beginning of feeding of 800-850 kg of silver ingots into a production link, so that compared with the preparation process in the prior art, the production and preparation method of the high-purity silver nitrate has the characteristics of environmental protection, high efficiency, low cost and high quality.

Detailed Description

The invention mainly focuses on the reutilization of nitric acid in the reaction process, a special purification process and high-efficiency solid-liquid separation.

The silver dissolution process is as follows.

800-850 kg of national standard No. 1 silver ingots are taken as a batch, and various stains shown by the silver ingots are washed off through a customized ultrasonic cleaning and drying system and processes of high-purity water washing, 3-5% acid washing, 3-5% alkali liquor and the like.

Putting the cleaned and dried silver ingot into a silver dissolving reaction kettle, adding 60-80L of high-purity water, starting an automatic steam heating system, adding 65-68% of analytically pure nitric acid at a constant speed in stages according to a proportion, controlling the temperature within the range of 85-110 ℃, and reacting to obtain a silver nitrate solution.

Hydrogen peroxide with a certain concentration range is added into a pretreatment part of a nitrogen oxide waste gas system to absorb nitrogen oxide generated in the reaction process of silver ingots and nitric acid, and absorption liquid is recycled. And sodium hydroxide and a urea absorbent are added at the rear end of the waste gas system to further absorb the pretreated nitric oxide so as to ensure that the waste gas is fully absorbed and discharged up to the standard.

The silver dissolving process of the invention adopts the introduction of hydrogen peroxide with a certain concentration range to convert most of the nitrogen oxide waste gas into nitric acid for recycling, and a small amount of nitrogen oxide which is not absorbed is absorbed by alkali liquor and urea at the rear end of a waste gas system, thereby realizing the recycling of the nitric acid, reducing the discharge amount of waste gas and waste water and simultaneously reducing the treatment cost. In the existing large-scale silver dissolving process, nitrogen oxide waste gas is converted into nitrogen to be discharged or adsorbed by an adsorbent, so that the treatment difficulty is high, the cost is high, the discharge is easy to reach the standard, a large amount of waste water, waste solids and the like are generated, and the cost is increased.

The specific purification process is as follows.

Transferring the silver nitrate solution into an impurity removal kettle in vacuum, heating to 80-85 ℃, adding an impurity removal agent, stirring for 1-1.5 h, standing for about 0.5-1.5 h, performing vacuum filtration to a1 mu m silicon carbide filter by using negative pressure, and transferring the solution into a neutralization tank.

Adding a proper amount of superior pure nitric acid, and adjusting the pH value of the silver nitrate solution in the neutralization tank to 1.0-2.0. The silver nitrate solution with the adjusted pH value is pumped by a pneumatic diaphragm pump and is filtered under positive pressure by a polytetrafluoroethylene filter element (less than or equal to 0.45 mu m).

The special purification process can ensure that the impurity content of the silver nitrate solution is in a lower level, and simultaneously improves the production efficiency. The prior purification technology adopts a mode of impurity removal by an impurity removing agent and secondary crystallization, and has the disadvantages of time and labor consumption, low production efficiency and high production cost.

The efficient solid-liquid separation is as follows.

And (3) feeding the completely crystallized silver nitrate solid-liquid mixture into a solid-liquid separation tank, combining a pneumatic diaphragm pump with vacuum filtration of 80-90 Kpa to realize high-efficiency solid-liquid separation of the silver nitrate, and directly feeding the separated product into an oven for drying.

The high-efficiency solid-liquid separation technology of the invention combines vacuum filtration and pneumatic diaphragm pump filtration processes, and can realize high-efficiency solid-liquid separation. The existing mode is centrifugal drying of a centrifugal machine, needs a small amount of centrifugal drying for multiple times, and has the disadvantages of large labor capacity, low production efficiency and certain potential safety hazard.

The invention is further illustrated by the following examples, without limiting the scope of protection to these examples.