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Methyl Bromide Scrubbing for Q/PS Operations

A new scrubbing process that is capable of destroying methyl bromide from ventilation air streams has been demonstrated at the Port of Wilmington by Value Recovery, Inc. of Bridgeport , NJ ( The process* was run on actual produce imported into the United States that was fumigated with methyl bromide. Methyl bromide is a known ozone depleter and has been banned for specific applications by the Montreal Protocol, an agreement signed by over 180 countries in the early 90's meant to protect the ozone layer. However, this application was for the use of methyl bromide to fumigate imported goods that fall under the Quarantine and Preshipment (Q/PS) category that is specifically exempted from the Protocol for many reasons. One reason has been that no economically viable process for emission control of methyl bromide has been available to the fumigation industry so far.

Value Recovery's process chemically destroys the methyl bromide by reacting it with a proprietary aqueous reagent mix and converting it into non-hazardous water-soluble products. The scrubbing system, see figure, consists of a forced air blower that processes methyl bromide concentrations in air in the 1 to 2 volume % (~40 oz/1,000 ft ^3) range typical of fumigation operations and converts the air stream into a column of fine bubbles to enhance gas-liquid mass transfer through a column of water. Scrubber inlet and outlet concentrations of methyl bromide are measured instantaneously through an infra-red monitoring system developed for fumigation operations. Data collected so far have shown removal rates of greater than 91% in a one pass operation. In a modification to the process, a multiple pass operation that allows for recycling the air will increase the removal rates to above 98%. The company is also working on modifications that will increase the per pass removal to greater than 95%.

The reaction results in a non-hazardous aqueous waste that might be directly discharged to a POTW (dependent upon local regulations). This particular scrubber configuration was put together to allow for the rigid constraints of the fumigation industry, namely the need for a process that does not interrupt the flow of cargo, is portable, operates at room temperature and is as simple as possible.

The process can be easily adapted for other applications in the chemical industry that may require the removal or detoxification of alkyl halides from production related waste. These would include methyl chloride, methyl iodide, ethyl chloride, benzyl chloride, butyl bromide, allyl chloride etc in either gas or liquid streams.

* patent pending

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