THE ONLINE PROCESS ANALYSIS OF FREEZE POINT FOR PETROLEUM PRODUCTS UTILIZING THE NEW CRYOCOOLERS AND THEIR PULSE TUBE TECHNOLOGY

摘要

Today’s petroleum refineries are striving more and more towards increased productivity andrnhigher quality standards. One of the critical parameters that must be measured in order tornachieve better production results is the Freeze Point of aviation jet fuel. Freeze Point is definedrnas the temperature at which the hydrocarbon crystals, formed on sample cooling, disappear asrnthe temperature of the cooled sample is allowed to rise. The importance of this measurementrnis to provide operations with control feedback data that can be used to adjust the refiningrnprocess of the stream being measured. Considering the high throughput of product in suchrnprocesses, the laboratory approach is not the most desired solution, due to the lag-timernbetween sampling, result reporting and the actual time of the lab test employed. Therefore,rncontinuous on-line analysis has been considered the most ideal for yielding instantaneousrnreporting and quality control feedback. The historical design approach of an online freeze pointrnanalyzer has resulted in a dual device that incorporates an external chiller (normally waterrnbased coolant) with a secondary device that cools the sample being analyzed using Peltierrncooling. These systems can work well but often result in high maintenance. External chillerrnsystems typically utilize CFC’s (Chlorofluorocarbon refrigerant gases), which are notrnenvironmentally friendly. Peltier based systems can reach maximum cool down temperaturesrnof -75℃ to -80℃ (-103 ℉ to -112℉) which in some processes is borderline for finding a CloudrnPoint. Cloud Point is defined as the temperature at which the smallest cluster of wax crystalsrncan first be observed as the sample is being cooled. The determination of Cloud Point isrnrequired first, to determine the Freeze Point.rnA new cooling approach is being utilized that will address a number of the concerns outlinedrnabove. A compact cryocooler used in an online analyzer will provide the benefits of fastrncooling, removal of external chillier requirements and direct cooling to –135 ℃ or colder.