New design for seawater desalination

presented by the inventor

Independent seawater distillation consultant

Robert Bom    Ruysdaelkade 22    1521 SV Wormerveer, The Netherlands    Tel. & Fax: +31 75 621 8822    E-mail: bomhart@xs4all.nl

Principles of design and operation

A novel design of multi-effect distillation plant is offered, with short vertical tubes: MED-STV. The concept is suitable for small to large capacity installations and presents the following advantages in comparison with existing MED plant design:

- reduction on investment, presently estimated to be 10 - 20 %;

- lower maintenance cost;

- shorter delivery.

The above advantages are obtained through the use of identical heat-exchanger modules made of suitable plastic, mass-produced by injection moulding and incorporating short vertical tubes. A typical module is shown in Fig. 1. Effects of the envisaged multi-effect distillation plant are housed in a vacuum-tight vessel, preferably made of concrete. Modules are applied in stacks of five. Stacks in one effect are placed side by side in a row, forming one wide disposition of stacks, constituting the heat exchanger in the effect in question. Such an assembly of modules is called an Aqua-Bloc. Fig. 2 shows a small Aqua-Bloc, two stacks wide, with total height of about 4 m. Rows of stacks of subsequent effects are placed parallel, at short distance, allowing easy cross-over of vapour from one effect into the next at five different levels, with minimum loss of pressure.

The design is presently aimed at low temperature application, using low pressure primary steam at saturation temperature of 75 °C max. Trouble-free operation is ensured with distillation at low temperature level and the use of non-corroding materials: engineering polymers and special grade of concrete. Double-fluted tubes are the preferred choice, made of an aluminium alloy which is developed for the purpose of seawater distillation.

For use in a ten to twelve effect installation, one module would typically produce 280 liters of distillate per hour. Capacity of the plant which is shown in the image of Fig. 3 would be 15,000 m³/day.

Present status and program

Patent position:

An international application, or PCT application, was filed on December 9, 1997, based on application in The Netherlands on December 9, 1996 (priority date). An international search was conducted by the European Patent Office (EPO). The search report is positive, since all publications found are classified as A-publication. Patent on the invention was granted in The Netherlands in June 1998.

Feasibility:

Results of preliminary studies into technical and economical feasibility are positive.

Business plan

The intention is to sell the present package, which includes all rights of patent (priority rights), preliminary technical and economical feasibility studies, principles of module design, basic choice of materials, availability of technical consultancy.

Ideal buyers profile:

Company already successfully engaged in seawater desalination or in related market, searching for new technologies or new products and capable and willing to invest in application development.

References and publications

The inventor of the Aqua-Bloc, Robert Bom, graduated from Delft University of Technology in 1957. After a brief engagement with marine steam propulsion, he was active in multi-stage flash distillation for more than 25 years with Werkspoor, Stork and Esmil, in The Netherlands. He then concentrated on the multi-effect principle and succeeded in finding the application which is now denoted by MED-STV, or the Aqua-Bloc. The system is described in detail in New Concept Multi-Effect VTE, presented by P. Robert Bom at the IDA World Congress on Desalination and Water Reuse, October 6-9, 1997, Madrid, Spain. An updated description is given in New ways in multi-effect distillation, with short vertical tubes, presented by P.R. Bom at the International Conference "The Next Breakthrough in Seawater Desalination", June 3-5, 1998, Curaçao, Netherlands Antilles.

For more information:

Please contact Robert Bom, at the abovementioned address.

Fig. 1: Typical module

Fig. 2: Aqua-Bloc, composed of ten modules

Fig. 3: Image of 15,000 m³/day STV multi-effect distillation unit