Project for extracting and refining sodium thiocyanate and sodium thiosulfate from 100m³/day of desulfurization wastewater

The size of the device can be adjusted according to the daily amount of desulfurization waste liquid

If you are interested in cooperating, please contact us by phone or for a face-to-face meeting

It would be best to include a simple market analysis, an introduction to the manufacturing process, and an overview of the project, so that everyone can gain a basic understanding

Sodium thiocyanate (NaSCN) has a wide range of applications; in the pharmaceutical industry it is used for the isolation of antibiotics； Used as a spinning solvent for polyacrylonitrile fibers in the textile industry ； Used in the printing and dyeing industry as a dye diffuser, fabric dye, etc ； Used in the pesticide industry to manufacture fungicides, insecticides, herbicides, etc ； It is used in the chemical industry as a detector for metals such as silver and copper, and as a raw material for manufacturing thiourea. Therefore, producing sodium thiocyanate has high economic value. During the coking process, part of the sulfur in coal is converted into sulfides such as hydrogen sulfide (H2S), which, together with ammonia (NH3) and hydrogen cyanide (HCN), become impurities in the gas. These impurities significantly affect the quality of the gas, so it must be desulfurized before it can be used. At present, many coking plants in China use the soda ash desulfurization process. This is one of the liquid-phase desulfurization technologies widely applied in the field of gas purification within China’s coal chemical industry. During the desulfurization process, this method generates by-products such as sodium thiocyanate, sodium sulfate, and sodium thiosulfate as the desulfurization waste liquid accumulates over time. The accumulation of these by-products increases the viscosity of the desulfurization solution, **reducing the efficiency of desulfurization. As a result, coking plants regularly discharge a portion of this waste liquid; if it is not utilized, it is discharged as industrial waste, thereby inevitably polluting the environment. Coking desulfurization crude salt contains a high concentration of sodium thiocyanate; it is therefore a chemical product with high added value. By extracting sodium thiocyanate from this material for industrial use, waste can be turned into a valuable resource. This not only contributes to environmental protection but also allows for the full utilization of waste resources, bringing economic benefits. It meets the goals of energy conservation and emission reduction, making it a practical solution. Some coking enterprises evaporate the water from desulfurization waste liquid to obtain crude salts of sodium thiocyanate, sodium sulfate, and sodium thiosulfate, but these crude salts require further comprehensive utilization as resources.

At present, the main method for extracting sodium thiocyanate from coking desulfurization wastewater in China is vacuum distillation concentration, followed by stepwise crystallization to obtain sodium thiocyanate and sodium thiosulfate products respectively. The purity of sodium thiocyanate obtained by this method is relatively low, and it is difficult to reach over 95%. In the coking plant, steam is used to evaporate the water from the desulfurization waste liquid, resulting in solid mixed salts. Approximately 4 tons of waste liquid are required to produce 1 ton of solid mixed salts, and the production cost per ton of such solid mixed salts is around 700 yuan. Some chemical plants purchase these solid mixed salts from coking plants, with a market price of 50–100 yuan per ton. Using this method, 30 tons of desulfurization wastewater can be processed per day, and the coking plant incurs an annual cost of 2.1 million yuan for the harmless treatment of such wastewater. Sodium thiocyanate with lower purity has limited applications, a very low price, and poor economic viability. It is of great significance to improve the salt extraction process in order to obtain high-purity sodium thiocyanate from the crude salt resulting from coking desulfurization. To address the shortcomings of existing methods for utilizing coking desulfurization waste liquid, our company has developed a new process for extracting sodium thiocyanate from desulfurized crude salt. By taking advantage of the fact that sodium thiosulfate and sodium sulfate have very low solubility in methanol, while sodium thiocyanate has higher solubility in methanol—and that its solubility changes significantly with temperature—this process enables the separation of sodium thiosulfate, sodium sulfate, and sodium thiocyanate from the crude salt. It features high selectivity, high product purity, as well as energy efficiency and environmental friendliness; the purity of the extracted sodium thiocyanate can reach over 98%. This set of equipment makes full use of waste resources; its process is simple and easy to implement, it saves energy, produces no waste gases, liquids, or solids, which is beneficial for environmental protection. It also has low production costs, offering good economic and environmental benefits, and it opens up new avenues for the comprehensive utilization of crude salt resources obtained from coking desulfurization.

This post was last edited by szq7768 on 2017-5-22 at 16:56. Since the system was put into operation in February 2014, production has been running smoothly. As the manufacturing process was continuously refined and optimized and production volume increased, the raw material consumption met the design specifications. Meanwhile, the purity of the sodium thiocyanate product improved, rising from 97.5% at the start of operations to 98.3%, which further reduced production costs and led to significant improvements in the company’s operational efficiency

Main features of this process: 4.1 For the first time, this system uses methanol instead of ethanol to extract sodium thiocyanate from crude salt. Methanol has no toxic side effects on the human body, is much cheaper than ethanol, and exhibits good selectivity for extracting sodium thiocyanate and sodium thiosulfate; it hardly extracts other ions present in crude salt, such as thiosulfate and sulfate ions. Through processes such as pressure filtration, evaporation and concentration, cooling crystallization, washing and centrifugation, and drying to remove moisture, a sodium thiocyanate product with a purity of over 98% can be obtained. 4.2 The low-concentration methanol generated during the extraction of crude salt with methanol is distilled and recovered, allowing for its reuse in the production process. Economic savings were achieved in raw material usage, reducing consumption and lowering production costs. 4.3 Good economic benefits. Coked desulfurized crude salt is very inexpensive; the methanol extractant used for extraction is low in cost, the process requires little energy, all materials involved in the process are recycled, the sodium thiocyanate obtained has a high purity, it has a wide range of industrial applications, and it possesses high economic value. 4.4 The process is simple, easy to operate, and energy-efficient. This device features a simple process flow, consisting only of basic steps such as extraction, pressure filtration, concentration and crystallization, centrifugation, and drying, making it very easy to operate. 4.5 After treating the wastewater, sodium thiocyanate product and distilled water can be recovered; no waste liquids or residues are generated throughout the process. There is no emission of exhaust gases or wastewater during production, which not only makes full use of material resources but also contributes to environmental protection, making it a green manufacturing process.

Methanol is well known to the public and is toxic. Industrial alcohol contains about 4% methanol, and if criminals use it to make fake alcoholic drinks, consuming such drinks can lead to methanol poisoning. The lethal dose of methanol is about 70 milliliters. Blatant nonsense