Development of a System To Utilize Flue Gas From Enhanced Oil Recovery Combustion Projects
Authors: Kaye S.E. , Ting V.C. , Fair J.C. 
Published: December 2007

Summary
A process has been developed that uses low-heat-value (LHV) flue gas from underground-combustion enhanced oil recovery projects to provide energy for air compression while incinerating air pollutants. The modified gas-turbine/catalytic-combustor system, ancillary equipment, and field test data on prototype catalytic combustors are described.

Introduction
Two factors that have hindered wider application of underground combustion or fireflooding as an enhanced oil recovery process are the high cost of compressed air and the cost of treating flue gas to meet environmental standards. Nearly 10 years ago, the Production Research Dept. of Gulf Research and Development Co. (GR and DC) initiated a study of methods to utilize the energy potential of flue gas to supplement the fuel used for air compressors while at the same time incinerating the hydrocarbons and sulfur compounds contained in flue gas.Early feasibility and economic studies proved sufficiently promising that GR and DC proposed and operated a joint industry research program to study utilization of LHV flue gas. The program explored flammability limits of fuel-enriched flue gas as well as the use of precious-metal combustion catalysts to eliminate the need for supplemental fuel. Reciprocating engines, steam-driven turbines, and gas turbines were examined as potential heat engines to make use of the hot gases produced. By the end of the agreed-upon program late in 1976, it had been concluded that catalytic combustion of flue gas without supplemental fuel was technically feasible and that economics favored the use of gas turbines for power recovery from the flue gas products of combustion. The resulting system was sufficiently promising that GR and DC chose to support further development of this concept without outside funding.This paper describes the gas turbine system and ancillary equipment developed in subsequent years. Data from small-scale high-pressure combustor tests using flue gas from an active combustion project are presented to illustrate anticipated system performance.

Previous Experience in LHV Gas Utilization
Published literature contains a number of references to the recovery of energy from gases of low calorific content. Gas turbines fueled by LHV blast-furnace flue gas have been built in Europe for more than 20 years. Successful operation of gas turbines on the products of coal gasification with air also has been reported. An engineering study performed on a system for utilizing the process off-gas from modified in-situ oil shale retorting found the system to be economically feasible. However, each of these LHV gases contains sufficient quantities of H2 and CO that flame combustion can be sustained without supplemental fuel. Composition of flue gas from an enhanced oil recovery combustion project was found to differ substantially from those gases previously mentioned. Hydrocarbons of the paraffin series contributed most of the heat value with relatively small amounts of CO and H2. Nitrogen and carbon dioxide dilute these constituents sufficiently that flue-gas heat values of less than 100 Btu/scf (3.73 MJ/m3) are common. Such a mixture normally is considered nonflammable at room temperature and pressure. Stinson was an early proponent of utilizing the flue-gas energy and correctly assessed the potential to reduce fireflood operating cost. By supplementing the flue-gas heat content with JP4 gas turbine fuel, Stinson reported that the "foul smelling compounds usually found in produced gases can be effectively destroyed by passing them through a gas turbine."
JPT
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