OCR Text |
Show There have been at least two independent instances of excessive corrosion and maintenance problems where the unit was properly installed or misused. In the two cases, the customer bought the direct contact heat exchanger tower and used his own secondary exchanger and distribution system and, in both cases, he also ran with fuel oil after being told specifically not to. As a result, the secondary heat exchangers were not designed properly and the return water temperature to the unit was too high. This led to a continuous loss of water vapor and, eventually, a dry unit. The dry tower or, more accurately, moist environment, combined with fuel oil firing resulted in excessive corrosion and equipment failure. Generally, the corrosion potential resulting from natural gas firing which results from a small concentration of N0X in the working fluid is eliminated by using either 304 S/S, 316 S/S, or fiberglass reinforced plastic for the tower pump and secondary exchanger. Installations that have been designed and installed by the equipment supplier have not experienced any corrosion problems. If one anticipates an unusual flue gas composition containing trace compounds that may pose an acid corrosion problem, it may be advisable to perform a chemical analysis to determine the flue gas composition for a potential application. IMPACT ON EMISSIONS This process has the unique feature of resulting in both energy recovery and emissions reduction. Minimally, the plant emissions are reduced by virtue of the fact that the boiler efficiency is increased by roughly 10 to 15 percent. In addition, when burning natural gas, a small percentage of the N0X emissions are reduced by condensation of nitric oxide. In sulfur-bearing fuel applications, the SO2 emissions can be reduced significantly by the use of a water bath that is highly buffered resulting in an alkaline water spray. The resulting water bath must be discharged in a pH range of 6-8 which requires additional caustic storage, metering pump, and pH control or inclusion of this wastewater stream in the plant's existing water treatment facility. The emission reduction potential of this equipment can have significant effect in areas that the EPA has judged to be nonattainment and could 9-26 KVB1 O-P-281 |