Methyl Chloride
Recovery

The Challenge

The customer is a multinational manufacturer of chemical compounds. They need to internally recover methyl chloride from their process equipment (mainly reactors) to avoid pollution and reuse in the process.

The average effluent composition is:

MeCL > 90%
Ethanol > 5 %
Ether < 3 %
Nitrogen gas < 2 %
Water < 0.1 %

Methyl chloride is a complex VOC because of its very low boiling point (-24°C). Consequently, recovery in the liquid phase is difficult in the presence of water. Therefore, special attention and a dedicated technical solution are required. Tests need to be done with liquid nitrogen in order to check the real cooling capacity of the cryogenic loops.

Our Solution

A cryogenic condensation unit with a refrigerated condensate tank.
The effluent cooling is divided into two steps: condensation at -85/-90 °C and final freezing at approx. -140 °C.
The temperature at the condenser outlet is controlled by automatic injection of liquid nitrogen in the coils, which must be set according to the requirements in terms of emission limits and/or recovery yield.
The liquid nitrogen used in the systems is kept in a separate circuit under pressure, and can be reused in gaseous form.
An ejector that uses gas nitrogen as the high-pressure driving fluid is provided before the effluent is vented to the atmosphere.
The condensate fractions are collected in a tank, which is refrigerated at approx. –85 °C using LIN in order to avoid re-evaporation.

Plant Design Data:

Quantity per batch: 700 kg
Recovered product: solvents mixture concentration 90-95 %
Total VOC flowrate at the outlet: < 100 g/h

Main Utilities Consumption:

Liquid nitrogen: approx. 3,300 kg/h at maximum flowrate
Gas nitrogen: 30-35 Nm³/h (during vacuum phase)

The Results

Proven Technology – Polaris tackled a new and difficult problem. The plant was fully erected, tested, and demonstrated under real working conditions to verify the temperature profiles in the cryogenic circuit before arriving at the customer’s door.

Guaranteed Without the Use of Further Treatment – The plant was designed with margins to ensure emission limits were always met, often even exceeding expectations. In addition, the unit could be continuously operated at temperatures below the melting point of the VOCs.

Built To Be Safer – The process reduces the flammability risks from hot temperatures or activated carbons, among others, which alternate technologies use for the treatment of process vents.