Development of the MSF process, USA
There was a long-standing dispute as to who should receive credit for the development of the original, long tube MSF evaporator, resolved with acceptance that original work was being undertaken simultaneously in the US and UK, and ultimately settled by a cross-licensing agreement.
The following is the recollection of Gordon Leitner, who led the Aqua-Chem effort in the USA.
The 1955 discovery and development of the MSF evaporator
The mid-1950s development of the first commercial MSF units almost proved to be an economic disaster for Aqua-Chem. At the time, the Wisconsin-based company was known simply as the 'water technologies division' of Cleaver Brooks; it wasn’t until 1969 that the name was changed to Aqua-Chem.
In 1954, we received an order for four distillers that were to be installed on the US Navy aircraft carrier Independence. However, the Navy required us to test one production unit on seawater for 30 days before the units could be installed on the ship. Our test work was carried out at what was then the International Nickel Company Seawater Test Facility at Wrightsville Beach, North Carolina, USA. The site later became the home of the first US Office of Saline Water (OSW) test station.
Based on our experience with vapour compression distillers operating at positive pressure, we designed the MSF units with centrifugal vapour separators. After several weeks of testing we were still unable to produce acceptable product water quality and the Navy was threatening to cancel the contract, which would have been a financial disaster for our company.
By now, Richard Goeldner and I were living at the test site, trying everything we could think of to modify the units so that we could pass the performance test. We worked through the Christmas holidays and on the 31st of December 1954, we sent a telegram to the home office that we were able to make good quality water in the first stage. By mid-January 1955, the entire unit was producing water that would meet or exceed the quality specifications.
One of the design changes we made was to install mesh type mist eliminators. At the time, it was a first in the industry, but that innovation is now standard on all seawater distillation units.
Although they still were a bit reluctant, the Navy authorities gave us permission to complete the test, and the units were installed on the aircraft carrier. The Navy has since given recognition to the value of that early work and all of the next generation of US aircraft carriers built since then have Aqua-Chem distillers.
While development of MSF for marine applications was still under way, the US and UK teams continued to adapt the MSF process for larger, land-based desalination units.
For those of us involved in the discovery/development of 'long tube' MSF, this was one of our finest hours. With the patent disclosures for long tube and brine recirculation designs on paper, we really had no idea if an MSF unit with many stages could be made to work.
One design concern was that the condensing tubes would have to pass through a tube sheet for each stage. Would the vapors tend to pass through the space between the tube and the tube sheet? Our vice president, the late Fred Loebel, said, 'Let’s build an experimental unit, and let’s pull a bullet through each tube to expand the tube against each tube stage separator plate.'
Concurrently, our engineers were carrying out calculations on an early computer and predicting that it was not necessary to seal the opening between tube and tube sheet. We then built the 24-stage experimental unit shown, in 1957, with the openings sealed in half of the unit, and not sealed in the other half. (Note two parallel tubular condensers. Either can be used in conjunction with the single flash chamber on the far side.) Performance was beyond expectations, with no difference between the two sections.
In 1958, Southern California Edison invited proposals for a research project to be located at the Mandalay Station near Oxnard, California. Their Chief Mechanical Engineer, T. M. Hotchkiss, wrote, 'The local water supply in the area where the station is located was of inferior quality. Furthermore, the local supplies were being used at near their maximum capacity. Consequently, there was a great deal of local interest in methods for alleviating this situation.'
During the evaluation of the proposals, Mr. Hotchkiss had visited our plant and observed our long tube MSF pilot plant in operation. After reviewing several alternate methods that were offered, Aqua-Chem’s proposal was selected was selected as offering the most promise for the research program.
In response to the ensuing contract a 568m3/d long tube MSF distilling plant with brine recirculation, representing a new concept in distilling plant design, went online in December 1959. It was integrated with the existing power plant and designed to produce high purity distilled water using low-grade steam. The plant proved to be a highly successful research project and was later moved to Catalina Island, off the coast of California, to help alleviate a growing water shortage.
While the early work was under way in the US, Dr. Adolf Frankel of Richardson Westgarth was working along similar lines. In the period 1958–1962, this British company and Weir were in active competition. In 1962, G&J Weir Ltd. and Richardson Westgarth Ltd. merged their land-based desalination activities under a jointly owned company, Weir Westgarth.