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membranes. Sulfuric acid, if necessary, initially would be supplied as a concentrated <br /> liquid containing 93 to 98 percent of the acid. It would be added to the feedwater <br /> tank as a diluted solution containing approximately 10 percent acid. The acid would <br /> reduce the pH of the RO feedwater and prevent precipitation of any residual calcium <br /> as calcium carbonate. <br /> Sodium hexa meta phosphate, if required, would be supplied as a dry powder and <br /> would be injected into the steam drum of the boiler as a solution of approximately 10 <br /> percent concentration. The chemical would prevent precipitation and scaling by <br /> alkali metal sulfates. <br /> Dissolved Oxyaen Corrosion Control <br /> The most common form of corrosion in the water-steam cycle in the boiler system is <br /> caused by the presence of oxygen dissolved from the air in the boiler feed water. <br /> Most of the oxygen is removed in the deaerator, however, the residual oxygen must <br /> be reduced to less than 0.03 ppm by the addition of an oxygen scavenging chemical <br /> such as sodium sulfite. This chemical is a dry powder and will be added to the boiler <br /> feedwater after the deaerator. The sodium sulfite will be added in sufficient <br /> concentration to maintain a residual in the feed water at the boiler inlet. The amount <br /> added will be determined based on the feed water characteristics. <br /> PH Correction <br /> The feed water pH should be adjusted to a level between 8.5 and 9.0 to protect the <br /> preboiler system. The pH will be adjusted by either the addition of a base or an acid <br /> chemical depending upon the natural pH of the boiler water without adjustment. <br /> Caustic soda (sodium hydroxide) will be used as the base, and sulfuric acid or <br /> sodium bisulfate will be used as the acid. <br /> Sodium hydroxide is used to raise the pH. It is a caustic strong base chemical <br /> supplied as a flake or a 50 percent solution. It would be metered into the boiler <br /> feedwater stream as a diluted solution of approximately 10 percent. <br /> If the boiler feed water is too alkaline, sulfuric acid will be used to lower the pH. <br /> Sulfuric acid is supplied as a concentrated liquid containing 93 to 98 percent of the <br /> acid and would be metered into the feed water as a diluted solution containing <br /> approximately 10 percent acid. <br /> G:\LM\M78545.002\Reclamation\Reclamexh.DOC D-44 <br />