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 (www.ptcvalue.com). 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.