COMPRESSOR STATION DISCHARGE GAS COOLING STUDY OF COSTS AND BENEFITS FOR THE NOVA SYSTEM

摘要

NOVA Corporation of Alberta operates a major gas gathering, transmission and distribution pipeline system in the province of Alberta in Canada. Nearly half of the compressor stations in this system have aerial cooling capacity. These coolers have been designed to ensure that the temperature of the discharge gas from the station does not exceed the permissible upper limit set for the station under the most limiting flow conditions. In conformity with the design principles, the coolers were, till recently, operated only to the extent required to prevent the station discharge gas temperature from exceeding this upper limit. Because the coolers are designed for the most stringent flow conditions anticipated, their use under 'average' flow conditions would result in station discharge temperatures being significantly lower than the permissible maximum. Recent studies within NOVA have determined that the benefits of operating existing coolers in the system continuously at or close to their rated capacities significantly outweigh the incremental costs associated with such operation. The benefits include both cost savings due to system wide reduction in the fuel gas use and net reductions in the emissions of CO{sub}2 and NO{sub}2. Based on the results of these studies, NOVA has now revised the operating philosophy for aerial coolers in its system such that they operate continuously and control is exercised only when the station discharge temperature reaches a set minimum limit.