Desalination provides metering opportunities

Desalination (the process of removing salt and minerals from water to make it potable) is mainly necessary in countries suffering water stress such as Oman, Kuwait and Saudi Arabia in the Middle East and in Australia, North Africa, Spain, the USA and China. It is also used on ships, submarines and offshore facilities.

There are two main methods of desalination; reverse osmosis i.e. forcing water through a membrane to collect contaminants (the opposite of this process is known as forward osmosis) – and multistage flash.

The multistage flash method uses heat to convert salt water into fresh water. The term flash refers to rapidly bringing the water to a boil multiple times or in stages. As the salt water enters each stage of the conversion unit it is subjected to externally supplied steam heat and pressure. During each stage, fresh water vapour forms and is collected.

There are two areas in desalination where the use of robust, accurate meters is necessary – to monitor the use of chemicals to control costs and to monitor and control the environmental impact of desalination.

Measuring chemicals

Chemical pre-treatment and cleaning are a necessity in most desalination plants. This typically includes treatment against bio fouling, scaling, foaming and corrosion in thermal plants and against biofouling, suspended solids and scale deposits in membrane plants.

Litre Meter products might be ideally suited to some of these applications. For example, VFF meters used in chemical injection in the oil and gas industry will be suitable for measuring the flow of chemical pre-treatment in the desalination process.

Monitoring impacts

Measuring the intake flow of water to mitigate damage to environment (e.g. destruction of plankton, fish fry and fish eggs) is probably a high flow application not ideally suited to Litre Meter products but more for KEM turbines and Tricor Coriolis meters. However, measuring the flow and concentration of brine being returned to the sea in the multistage flash process may be more relevant. This entails measuring the mixture of brine in the mixer zone to minimise ecological impact of returning brine to the ocean.

 

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