Boiler feed water, specifically for steam generation requires high purity water. The feed quality requirement varies depending on the manufacturer/generator. Poor water quality and/or system design results in increased maintenance and downtime. The design of the water treatment system is a function of the water quality that varies dramatically depending on the water source and region.
BOILER FEED WATER PURIFIACTION PROCESS
The main contaminants to remove are hardness, iron, silica, sodium and chlorides. The basic process removes the suspended matter before reverses osmosis (dissolved solids reduction) and finally EDI polishing. RO pre-treatment commonly consists of coagulation, flocculation, clarification, sand filtration, etc. Essentially 100% of the suspended particles must be removed in the pre-treatment. RO removes approximately 99+% of dissolved salts in water or TDS.
EDI is the final polisher. Continuous Electrodeionization (CEDI or EDI) is a process that uses electricity to produce ultra-pure deionized/demineralized water. While it utilizes ion exchange resin, it is continuously self-regenerated without the use of chemicals (i.e. caustic and acid used with conventional ion exchange systems).
There are a number of advantages to EDI versus mixed bed (IX):
1. Easier to obtain permits
2. Green technology – chemical free process
3. Lower operating costs
4. No hazardous waste (no neutralization sump/system required)
5. No handling, disposal, or storage issues/concerns
7. Smaller footprint/space requirement
The industry standard is moving toward RO+EDI versus conventional treatment with ion exchange. Particularly in the United States where it is becoming difficult to obtain permits for the hazardous chemicals (storage and disposal). We have boiler feed water systems utilizing RO-EDI technology in California, Hawaii, Venezuela, etc.