After entering the 21st century, the sustainable development strategy puts forward higher requirements for resource and energy conservation and environmental protection, so the rational utilization of organic solvents becomes increasingly urgent and acute. Solvent production and use enterprises can improve the recovery rate of solvent through the selection of high-performance vacuum pump, and realize the simultaneous improvement of economic and social benefits. Through reasonable selection of vacuum pump, the application of vacuum pump in solvent removal can achieve the purpose of reducing consumption, environmental protection and increasing efficiency.
Use of solvent in production
(1) In the process of chemical and pharmaceutical production, in order to realize the economical application, the phase state of solvent changes constantly. After many times of application, some impurities will inevitably be mixed in the solvent. At this time, distillation is often used to refine to meet the use quality index. In the refining process, considering the heat sensitivity, yield, quality and other indicators of the product, the solvent is mostly separated by vacuum drying and distillation for application. In the above process, the solvent undergoes the process from liquid state to gas state and then to liquid state. According to the law of conservation of matter, the final amount of solvent should be equal to the initial amount. But in actual production, the former is always less than the latter, the difference between them is the loss of solvent, which appears in the environment in various phases, causing environmental pollution.
(2) In the production process, many chemical reactions make use of the dispersity of the solvent, so that different materials in the reaction are dissolved in it and fully mixed, so as to ensure the complete reaction. In order to make the process proceed according to the set way, it is necessary to extract the intermediate from one solvent to another, so that there will inevitably be solvent residues in the final product.
(3) Before the final product is obtained, the product needs to be refined: for the solid product, a certain solvent is used to wash off the solid impurities, and then remove the solvent; for the liquid product, the residual solvent needs to be separated and removed to the maximum extent.
The application of vacuum pump in solvent removal mainly includes:
1. Used in solid product refining process (drying)
In the refining process of solid products, the last step is often drying. There are three main requirements: (1) to maintain the original physical properties of the finished product; (2) to achieve the quality indicators of solvent residues; (3) a certain production efficiency. In addition, solvent as the medium used in production, recovery means the reduction of cost and environmental protection. The recovery of solvent shall be based on that the solvent can be directly returned to the production link.
In order to meet the requirements of drying itself, vacuum pump is usually selected as the driving force. Because of the volatility of the solvent, especially in vacuum, even if the recovery solvent is cooled by cryogenic medium, some of the solvent will escape. If the solvent can be recovered at atmospheric pressure, the recovery of solvent will be greatly improved. In order to meet the requirements of the above three aspects, the vacuum pump can be selected: the vacuum pump has a strong ability to generate vacuum (the air extraction volume generated by unit volume and unit use power is large, the vacuum degree is high, and the operation is stable); the vacuum pump has no working liquid, which is convenient for normal pressure recovery after the pump.
2. It is used in the refining process (rectification) of liquid products. The last process is usually rectification. The main purposes are: to maintain the physical and chemical properties of the product; the refining yield of the product is as high as possible; taking the product as the positive fraction, to remove the low boiling part as the solvent and the high boiling part of the waste material, so as to achieve the product quality index. Liquid products usually have the heat sensitivity of thermal deterioration, so it is very important to achieve refining at a lower temperature. Similarly, from the consideration of economy and environmental protection, the removed solvent must be recycled.
The refining of liquid products is required to be carried out under high vacuum as much as possible, and the normal operating pressure is below 10Pa (one standard atmospheric pressure is 101325pa). There are two kinds of single pumps: slide pump and claw pump; roots vacuum unit.
The correct selection of vacuum pump has amazing economic benefits and environmental protection effects. Therefore, for every solvent production technician, this is a great event worthy of attention and of great significance. Through this paper, we can draw the following conclusions, the application of vacuum pump in solvent removal can achieve the following results: 1. Shorten the operation time of the whole section, reduce the amount of resin residue, improve the distillation rate; 2. Reduce the distillation end temperature, reduce the resin tendency of materials; 3. Reduce the raw material consumption of 2, 3 acid products.