Methylene Chloride
Recovery

The Challenge

The customer is a pharmaceutical manufacturing and development company that needs to recover the methylene chloride (MDC) from their process equipment. The MDC is present in both gaseous and liquid streams. Due to a previous experience with steam stripping, the client is reluctant to change technologies.

The goal is to reduce emissions below the limits set in European Directive no. 999/13/CE, while also reducing the MDC in the water to below 3 ppm. They require the Factory Acceptance Test (FAT) to include the complete erection and testing of the plant, showing the control of emission limits in the atmosphere and the recovery yield of MDC. To verify results, analysis will be performed by an external, independent authorized laboratory.

Our Solution

A plant composed of a double unit: a stripping unit for the removal of methylene chloride from water, and a cryogenic condensation unit to separate the VOC from the gaseous stream.
The stripping unit has the double option of stripping media: nitrogen or steam.
A gravity phase separator is provided to separate the methylene chloride-rich phase from the water-rich phase of the condensate streams.
The liquid nitrogen used in the systems is kept in a separate circuit under pressure, and can be reused in gaseous form.

Plant Design Data:

Gas Stream:
- Flowrate: max. 300 Nm³/h
- Duration of the emission: batch with variable flow (24 h/d, 5 d/w, 220 d/y)
- VOC present in the effluent: MDC up to saturation
Liquid Stream:
- Inlet wastewater flowrate: 500 kg/h
- Operation: continuous (24 h/d, 5 d/w, 220 d/y)
- MDC in the water: 3,100 ppm w/w

Main Utilities Consumption:

Stripping Unit:
- Process with nitrogen
  - Electric power: 5 kW
  - Gas nitrogen: approx. 15 Nm³/h
- Process with steam
  - Electric power: 5 kW
  - Steam: max 60 kg/h
Cryogenic Condensation Unit:
- Electric power: 6 kW
- Steam: approx. 5kg/h
- Chilled water: approx. 1 m³/h

The Results

Proven Technology – The plant was erected and fully tested at the Polaris facility, simulating the real process streams to verify the recovery efficiency.

Exceeded Expectations – By using a combination of steam and nitrogen, the stripping unit’s performance exceeded requirements. Additionally, the final content of MDC in the water reached a value of < 0.1 ppm. The cryogenic unit was designed with margins to ensure emission limits were always met, and the unit could continuously operate at temperatures below the melting point of the VOCs.