Coal-Liquefaction Preheater Coking. Final Report, October 1, 1981-September 30, 1982

摘要

This is the final report on Sandia's Coal-Liquefaction Preheater Coking program. The literature was reviewed for reported incidences of material deposition in coal-slurry preheaters. The results of the review indicate that the mechanism of material deposition is a two-step process in which masses of slurry separate from the bulk phase, adhere to the tube wall and subsequently undergo carbonization. The separation of the slurry masses is caused by the high slurry viscosities that exist during slurry gelling. These masses adhere due to their sticky nature. Case studies of material deposition incidences in the Wilsonville preheater were conducted. The results of these case studies indicate that material deposition was promoted by solvent vaporization, which would increase slurry viscosities during gelling, and by low flow rates which would increase the probability of slurry masses adhering to the tube wall. A set of preheater modifications designed to reduce the in-situ coal concentration in the slurry phase, which would minimize viscosities during gelling and thereby suppress material deposition, was formulated. The modifications include elimination of gas feed to the slurry preheater, recycle of 650 exp +0 F boiling solvent, and a decrease in the feed-slurry coal concentration. (ERA citation 08:025329)