Treatment of Dichloroethane Waste Gas

The problem of treating dichloroethane waste gas is becoming increasingly severe. Dichloroethane waste gas treatment is a type of halogenated hydrocarbon that needs to be treated, commonly represented by EDC. At room temperature, it is a colorless or light yellow transparent, heavier than water, and volatile liquid that is difficult to dissolve in water. It is miscible with most commonly used organic solvents and has a stimulating odor similar to chloroform. Due to its strong solubility and low boiling point, it has long been used as a solvent, extractant, dry cleaner, wetting agent, raw material for pesticide manufacturing and various chemicals.

However, dichloroethane has a low boiling point and is prone to volatilization during industrial production, causing environmental pollution. The commonly used processes for treating dichloroethane waste gas include low-temperature condensation, solvent absorption, activated carbon adsorption, and membrane separation.

The low-temperature condensation method is a process that utilizes the relationship between the saturated vapor pressure of dichloroethane and the decrease in temperature, lowering the temperature below the boiling point of dichloroethane and transforming it from a gaseous state to a liquid state. This process has a good recovery effect on high concentration dichloroethane waste gas, but incomplete condensation will still result in high concentration waste gas being discharged.

The solvent absorption method is a process that utilizes the high solubility of dichloroethane, selects other high boiling organic solvents to absorb dichloroethane waste gas, and then distills and recovers dichloroethane. The processing efficiency of this process is low, the solvent absorption is insufficient, and the absorbent itself will also evaporate, resulting in secondary pollution.

Activated carbon adsorption method is a process that utilizes the adsorption properties of activated carbon to adsorb dichloroethane in exhaust gas, and then recovers dichloroethane through steam blowing. The adsorption effect of activated carbon in this process is greatly affected by moisture, and the adsorption performance decreases significantly after multiple blow off regenerations; And dichloroethane is easily catalyzed and decomposed by impurities in activated carbon, producing hydrogen chloride gas. When it comes into contact with water, it turns into hydrochloric acid and corrodes equipment severely, shortening the service life of pipeline equipment.

The basic principle of membrane separation method is to use a polymer membrane with selective permeability for dichloroethane. Under a certain pressure, dichloroethane is allowed to permeate through the polymer membrane and be enriched. The gas removed from dichloroethane is left in the permeate side and discharged from the system. This process is simple and has low energy consumption. However, at the same time, the membrane has a short lifespan, high investment costs, and is limited to the field of high concentration and low air volume waste gas treatment. The concentration of the waste gas after removing dichloroethane is still high, and it is generally used as a pretreatment process for low air volume and high concentration waste gas.

In response to the current problems in the treatment of dichloroethane waste gas, Jiangsu Haipu Functional Materials Co., Ltd. has developed HDV type polymer nanoadsorbent, which can adsorb and remove dichloroethane from waste gas. After adsorption saturation, the nano adsorbent is desorbed and regenerated using steam, and dichloroethane steam can be condensed and recovered. The specific process is as follows:

The specific process description is as follows: the dichloroethane waste gas in the workshop is first extracted by a vacuum pump and then subjected to secondary condensation. The condensed and liquefied dichloroethane is received in a storage tank, and the uncondensed dichloroethane waste gas is connected to an adsorption tower containing nano adsorbents for adsorption and enrichment. After adsorption, the waste gas can be discharged in compliance with standards. After the adsorbent is saturated, low-pressure steam is introduced into the adsorption tower for stripping, which can separate and recover dichloroethane. The nano adsorbent after steam desorption can be reused for adsorption. The adsorption tower is usually equipped with two units, one for adsorption and one for desorption as a backup. For high concentration exhaust gases, two or more units can also be configured (as shown in the figure below).

This process can achieve a removal rate of over 99% for dichloroethane in exhaust gas and has been validated on multiple project sites.

Advantages of HDV type nano adsorbent:

• Controllable pore structure and high pore volume;

• Has good physical and chemical stability, is resistant to acid, alkali, and organic solvents, has high thermal stability and mechanical strength, and is wear-resistant;

• The surface exhibits high hydrophobicity, and humidity has no effect on adsorption performance;

• Easy to regenerate and stable adsorption performance;

• No hazardous waste is generated without the need for replacement.