Application Traditionally for water treatment demineralisation plants, 96 or 98% sulphuric acid has been diluted to 3 or 4% in two stages by using rubber lined measuring/dilution tanks. These systems are expensive, prone to failure and require a large space envelope. To overcome these limitations, pipeline mounted Liquid Jet Pumps are now being used to perform the dilution in one stage. In the north west of England a new combined heat & power station had installed a number of Liquid Jet Pumps constructed from a special cast metal alloy, Carpenter 20, for diluting sulphuric acid from 96 to 4%. Unfortunately during commissioning a number of the units failed in operation due to porous castings. Transvac investigated the problem and recommended that Transvac corrosion resistant Liquid Jet Pumps with PTFE contact parts replaced the failed units.

Solution The new units were designed to retrofit into the same pipeline positions occupied by the Carpenter 20 units to minimise pipeline modifications. After installation and successful commissioning, the performance of the Transvac PTFE units was monitored closely over a long period by the plant chemist. At the end of this period he was so impressed with their performance that he replaced all the remaining Carpenter 20 units with Transvac PTFE units.

Advantages

• Low cost
• Custom designed
• Compact
• No moving parts
• Simple to operate
• Maintenance free
• Easy to install

Principle of Operation

In operation pressurised motive water is accelerated through a jet nozzle creating a region of low pressure into which the concentrated sulphuric acid is entrained. The two fluid streams then combine and thoroughly mix in the diffuser throat. The mixture is then decelerated in the diverging cone to regain pressure to overcome system backpressures.

Design

Each Liquid Jet Pump is custom designed to suit the process conditions. It is common practice to include a metering valve in the suction line to the unit to trim the flowrate of the concentrated acid and a non-return valve to prevent any backflow into the acid storage tank.

The process of diluting sulphuric acid is very exothermic and corrosive. PTFE is an ideal material for this application as it is corrosion resistant and is suitable for the high temperature transient pockets that occur during operation.

Construction

Standard materials for this application are PTFE contact parts supported by a carbon steel shell with flanged connections, but we can also supply hastelloy and other suitable materials. The units are designed to comply with the latest European standards and CE marked where applicable.