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power plantHydrazine Injection for Boiler Water Treatment

Corrosion is a major problem for steam boiler systems in power plants with high consumption of make-up water. Fresh untreated water contains dissolved oxygen, which together with the high temperature, is highly corrosive for the carbon steel piping used in steam generation systems.

To avoid corrosion in the system, oxygen is removed from the system water, as well as in the make up water added to the system, by using scavenger chemicals.  One scavenger chemical commonly used, especially in high pressure systems, is Hydrazine.  Hydrazine efficiently eliminates the residual oxygen by reacting with the oxygen forming water and gaseous nitrogen.

The amount of hydrazine required is relatively small, a mixture of about 200 parts per billion.  Flow rates are relatively low, typically from 200 mL/min to 800 mL/min, but can go as high as 1.5 mL/min. Consistency and accuracy are important.

FMI’s QVG50 variable speed valveless piston pumps have proven ideal for injecting hydrazine since they are self priming and will not lose prime even at very low flow rates. The integral RH miniature pump head features chemically inert, sapphire-hard ceramic internals, which provides millions of maintenance-free, calibration-free cycles of service. The QVG50 is controlled using FMI’s V300 Variable Speed Controller, which includes a 4-20 mA electronic control input, typically used in process control applications. The QVG50 can inject Hydrazine directly into the system line, or into a storage tank when additional contact time is preferred.

FMI pump application diagram

pump application diagram

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