OCR Text |
Show 5.9.5 High pressure pumps requires close clearances between the pump gear and housing. High viscosity materials and those containing solids tend to score the surfaces, causing wear which results in gradually decreasing outlet pressure. Materials transport is critical in the proper design of an incineration system. This applies as well to the heat exchanger, piping, and valving on the system downstream of the pump prior to injection nozzles. Seme waste materials, such as Toluene Di Isocynate (TDI), have a very narrow operating range for temperature. Due to its high viscosity at room temperature, this material must be maintained at 300°F (4500 SSU) in order to properly pump and atomize. (Fig. 1) However, at 400°F, polymerization of the liquid takes place. It is, therefore, very important to know the characteristics of the waste in the design stage so that proper selection of heat exchanger conditions is made. If high pressure steam is available, the saturation temperature must be reviewed to insure that polymerization will not take place and cause complete plugging of the exchanger and associated piping. Backup controls must be included to prevent a low temperature condition resulting in freeze-up and complete shutdown of a system. All of the piping, valves, and downstream nozzles would become a solid waste disposal problem. The pipe lines must be designed to provide smooth flow of the liquids. High velocity tends to cause erosion and rapid failure of piping with a corrosive liquid. Low velocity or dead zones must be eliminated to prevent dropout of solids and heavier components. This could cause pipe blockage. |