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Specialist Chemical Engineering Solutions
Within the Power Generation Industry there are basically three application areas for chemicals. These are for the treatment of the boiler feed water, the recirculation of the cooling tower water and the effluent treatment plant. Depending on the power source for the power station it will make a difference to the operating pressure within the boiler drum. Generally coal-fired power stations run at around 200 bar; CCGT plants operate the high pressure drum at 120 bar while in combined heat and power plants these run at lower pressures in the order of 60 bar. The treatment required for demineralised boiler feed is the use of an oxygen scavenger which will either be a commodity product like hydrazine or a speciality product such as carbohydrazide. These will be injected into the outlet of the deaerator. Also added on the discharge side of the deaerator will be an amine or ammonia, although if the latter is required then careful consideration has to be given to the storage tanks as the vapours will require scrubbing. Lastly, phosphates are added to the boiler drum. These can either be blended or trisodium phosphate and this is where the high pressure pumps are required.
For the treatment of the open evaporative cooling towers you will be adding an oxidising biocide like sodium hypochlorite. In order to optimise the use of the sodium hypochlorite acid will be dosed to control the pH. For smaller cooling circuits the use of sodium hypobromous acid can be used which is a blend of sodium bromite and sodium hypochlorite. Lastly a corrosion inhibitor will be introduced into the system which is usually dosed in proportion to the make up water.
Finally, there is the effluent treatment plant which will require pH correction as this will be receiving the blowdown from the boilers plus the regen liquors from the demineralisation plant.
| Process Stage | Problem | Consequences | Chemical Solution | Gee's Solution |
|---|---|---|---|---|
| Boiler Water Treatment | Boiler Corrosion & Scaling | Poor Efficiency Boiler Failure |
Hydrazine Carbohydrazide Trisodium Sulphate Blended Phosphate Ammonia Amines |
Effluent Treatment Plant Package Plant For Coal (HP) 200+ Bar For CCGT (MP) 120 Bar for HP drum For CHP (LP) 80 Bar Single drum |
| Cooling Towers | Legionella | Health Issues | Sodium Hypochloride Electrochlorination Hypo Bromous Acid |
Effluent Treatment Plant Package Plant Michael Smith Systems KB Michael Smith Systems KTB |
| Cooling Towers | pH Control | Corrosion / Scaling Poor Disinfection |
Inorganic Acid | Effluent Treatment Plant Package Plant |
| Effluent Treatment | Disposal Ion Exchange,
Regenerate Liquor and Boiler Blowdown |
Consent Failure | Inorganic Acid Inorganic Alkalis |
Effluent Treatment Plant Package Plant |
| Final Discharge | Disposal of cooling tower purge water | Consent Failure due to Chlorine | Sodium Bisulphate | Effluent Treatment Plant Package Plant |
