How are Internal Treatment Chemicals Fed?
Common feeding methods include the use of chemical solution tanks and proportioning pumps or special ball briquette chemical feeders. In general, softening chemical (phosphates, soda ash, causti, etc.) are added directly to the fee-water at a point near the entrance to the boiler drum. They may also be fed through a separate line discharging in the feed-water drum of the boiler. The chemicals should discharge in the fee-water section of the boiler so that reactions occur in the water before it enters thesteam generating areas. Softening chemicals may be added continously or intermittently depending on feed-water hardeness and other factors. Chemicals added to react with dissolved oxygen (sulphate, hydrazine, etc.) preferably should be fed continously as far back in the feed-water system as possible. Similarly, chemicals used to prevent scale and corrosion in the feed-water system (polyphosphates, organics, etc.) should be fed continous-ly. Chemicals used to prevent condensate system co
