A Discussion on Waste Gas Treatment Technologies and Applications in Pharmaceutical Enterprises
As the quality requirements of people's living environment continue to increase, the situation of industrial waste gas reduction is extremely severe. The technology and application of waste gas treatment for pharmaceutical enterprises have been analyzed to further implement the Scientific Outlook on Development and develop a circular economy.
1. Organic solvent method
The best way to control solvent waste gas is to improve the recovery efficiency of the solvent. Reduce the emission of solvent at the source. There are many methods for the chemical industry to improve the solvent recovery efficiency and reduce solvent emissions. Most of these methods are mature and reliable. Currently, the methods for recovering organic solvents from waste gas include:
1.1 Adsorption method.
The adsorption method is the most widely used deep solvent recovery technology. Its principle is to use adsorbents such as granular activated carbon, activated carbon fibers, or zeolites with porous structures to capture organic substances in the waste gas. When the waste gas passes through the adsorption bed, the organic substances in the waste gas are adsorbed by the adsorbents on the bed layer, and the waste gas is purified. Due to the high price of the adsorbents, they need to be desorbed and regenerated for recycling. When the adsorbents reach saturation, water vapor (or hot air) is introduced to heat the adsorption bed for desorption and regeneration. The organic substances are blown off and released along with the water vapor (or hot air) in the vapor mixture and leave the adsorption bed. The vapor mixture is cooled by a condenser to condense into liquid. If the organic solvent is water-soluble, the distillation method is used to separate and purify the liquid mixture; if it is water-insoluble, it is directly separated and recovered by a separator. The adsorption method can be divided into the following categories: Firstly, direct adsorption method: The organic waste gas is adsorbed by activated carbon, achieving a purification rate of over 95%. The equipment is simple, the investment is small, but the activated carbon needs to be replaced frequently, which increases the loading, transportation, and replacement procedures, resulting in increased operating costs. Secondly, adsorption-recycling method: Using fiber activated carbon to adsorb the organic waste gas, and then using hot water vapor (or hot air) to reverse blow for desorption and regeneration; this method requires the provision of necessary steam volume. Thirdly, new adsorption-catalytic combustion method: This method combines the advantages of adsorption method and catalytic combustion method, using a new type of adsorption material (honeycomb-shaped activated carbon) for adsorption. When approaching saturation, hot air is introduced to perform desorption and analysis; the desorbed waste gas is introduced into the catalytic combustion bed for flameless combustion, which is thoroughly purified. The hot gas is recycled in the system, greatly reducing energy consumption. This method has the characteristics of stable operation, low investment, low operating costs, and convenient maintenance. It is suitable for the treatment of large volume and low-concentration waste gas and is currently a relatively mature and practical method for treating organic waste gas in China. To achieve a high recovery rate, the system requires a very high pressure or a very low temperature, resulting in a significant increase in equipment and energy costs.
2 Fermentation Exhaust Gas Treatment Technology
With the rapid technological development of pharmaceutical enterprises, the biological fermentation process has become one of the essential technologies for pharmaceutical production. Therefore, during the production process, a large amount of untreated exhaust gas is discharged into the atmosphere, causing some fermentation metabolites to be carried away with the exhaust gas, and even generating special unpleasant odors. That is, the concentration of the drug components or intermediates in the air keeps increasing, which in turn poses hazards to humans and the environment. Therefore, it is necessary to treat the fermentation exhaust gas. The composition of fermentation exhaust gas is complex, and there are not many treatment methods in both domestic and foreign countries. Moreover, there is no thorough, economical, and reasonable solution. In foreign countries, a membrane filter is usually installed after the gas-liquid separation device of the fermentation tank. The membrane filter has a high separation efficiency, but it is affected by sterilization steam from the fermentation exhaust gas, resulting in a short service life of the membrane filter and high maintenance costs; moreover, for the exhaust gas, the pressure drop resistance is large, which will bring a series of problems. First of all, air pressure.
