Wednesday, May 21, 2014

Bonus Process Wednesday: more on the MV Cape Ray

From Chemistry World, some interesting tidbits on the U.S. Navy's newest chemical plant, i.e. the MV Cape Ray (article by Nina Notman): 
...Walker, however, says that unexpected issues may occur because the units are new and their set-up on ship unique, and they haven’t yet been tested on actual agents or precursors. ‘They have many kilometres of piping on board the ship, and the precursor chemical for sarin tends to crystallise and could back up and plug up the valves and the pipes. There could be breakdowns that would slow the process down,’ he says. The US government has predicted that the hydrolysis operation will take about 90 days. Blades remains confident: ‘The field-deployable hydrolysis unit was designed and built with an elegant simplicity and mechanical redundancy to address potential component failure. Should component repair or replacement be required, there are highly trained technicians as well as appropriate spare parts on board.’ 
The largest unknown is the weather. ‘There have been questions raised about what sea state they can operate in,’ says Walker. The Cape Ray is equipped with stabilisers, and because the ship has no set destination it can be navigated to avoid bad weather. Two sea trials have been carried out to evaluate safe operating parameters for both the equipment and the crew, says Blades. 
The neutralisation process 
The two field-deployable hydrolysis units are contained within a single environmentally sealed tent on board the ship. The plan is to operate the units in parallel 24 hours a day.
The mustard and DF will be neutralised slightly differently. ‘[Mustard] will be hydrolysed using a batch process facilitated by the titanium reactor at a ratio of approximately 13.5 parts 95°C water to one part ambient [mustard],’ explains Blades. The mustard breaks down in hot water to hydrochloric acid and thiodiglycol. The second step is to adjust the effluent’s pH to neutral using sodium hydroxide. ‘DF will be hydrolysed as a continuous feed process using a ratio of five parts ambient-temperature water to one part ambient-temperature DF,’ he says. DF breaks down to methyl phosphonic acid and hydrogen fluoride. A batch process using sodium hydroxide will again be used to adjust the pH. On board the ship there are approximately 220 ISO containers, each capable of holding 6600 gallons of water or caustic solution. The ship can desalinate additional water if required. 
‘The neutralisation process generates hazardous waste effluent in volumes of five to 13.5 times the volume of chemical warfare material being treated. These materials are similar to standard industrial chemicals, containing less than 0.1% agent, that are regularly processed by commercial facilities,’ says Blades. This effluent will be stored in the empty ISO containers. After all the chemicals have been neutralised, the Cape Ray will sail to Germany and then Finland to deliver the two effluents for incineration...
That whole "plugging up the valves" part sounds awful -- the "up the pressure and break it loose" solution probably doesn't work well there. Don't forget, the MV Cape Ray also has analytical chemists on board!:
There is an analytical laboratory on board the Cape Ray containing GC–MS instruments. Before the hydrolysis begins ‘analytical chemists in this laboratory will verify the identity of the neat agent, ensuring the chain of custody at the point of destruction,’ explains Forman. ‘After neutralisation, GC–MS analysis would again be used, this time to determine that the neutralisation has gone to completion.’
Pretty neat. Read the whole thing!

2 comments:

  1. "It was decided to destroy around 120 tonnes of isopropanol, which can be mixed with DF to make sarin, in Syria." That seems a bit silly. I can't imagine that's all the rubbing alcohol they have in Syria.

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  2. Hi 'anonymous', you've made a valid point. And it's not just the isopropanol that has other 'peaceful' uses, many of these chemicals have a battery of other harmless uses. But the Chemical Weapons Convention dictates that if the chemicals have been made for the specific purpose of being used to make chemical agents, they must to be destroyed regardless. When I was quizzing the UK MOD guys about this, they said no one would want to reuse the chemicals if they were permitted too anyway - due to purity and general bad PR concerns.

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