Review Of Stack Gas Scrubber Operating Experience On An Oil-Fired Steam Generator

Abstract

Abstract Operating experience of a prototype stack gas scrubbing system to remove sulfur dioxide from the flue gas of an oil-fired steam generator located at a Kern River Field steam drive project near Bakersfield, California, is outlined. This paper presents a description and summarizes performance from initial startup through the end of the six-month demonstration test. The scrubber is used to desulfurize 500 to 740 ppm sulfur dioxide flue gas from a 50 MMBtu/hr oil-fired steam generator. Introduction Curtailment of natural gas fuel supplies compounded by expansions of steam drive projects at Kern River Field, Kern County, California, greatly increased the need for fuel oil and for crude as incremental fuels beginning in 1973. At present, virtually all steam generators are oil fired with either fuel oil or lower-tier crude. Both these fuels contain approximately 1.1 weight percent sulfur which is converted to sulfur dioxide percent sulfur which is converted to sulfur dioxide during combustion. Increased ambient sulfur dioxide concentrations in the atmosphere at populated areas near the southern perimeter of Kern River Field have approached the National Ambient Air Quality Standard of 80 microgram per cubic meter for sulfur dioxide. This led to early limited use of tall stacks to increase dispersion of sulfur dioxide into the atmosphere, thus reducing ground level sulfur dioxide concentrations at receptor areas. However, continued steam drive expansions have increased the use of sulfur bearing fuels and the eventual need to reduce sulfur dioxide emissions. Basically, there are two methods for complying with sulfur dioxide emission standards while burning oil. These are removal of sulfur dioxide from the flue gas before it is emitted to the atmosphere, or the use of low sulfur fuel oil. The demand for very low sulfur fuel oil is rapidly increasing and the future price and availability are not favorable. After technical and preliminary economic evaluations, a development program was commenced to design, build, and test a full-scale stack gas scrubber for sulfur dioxide removal from the flue gases of an oil-fired 50 MMBtu/hr steam generator. The successful completion of this test program produced valuable insight into the reliability and costs of removing sulfur dioxide from oil-fired steam generator flue gases. This paper describes the scrubber system and presents operating experience at the Yarn River Field presents operating experience at the Yarn River Field installation. PROCESS AND DESIGN CONSIDERATIONS PROCESS AND DESIGN CONSIDERATIONS Gas absorption is employed in wet scrubbers to remove sulfur dioxide from steam generator flue gas. Absorption is a process in which a soluble gas component of a gas mixture is dissolved into a liquid. Removal of sulfur dioxide from a flue gas stream passing through a wet scrubber involves preferential passing through a wet scrubber involves preferential solution of the sulfur dioxide into an aqueous scrubbing liquor followed by reaction with active alkaline constituents in the liquor. The reaction products are sulfur containing salts which are purged from the scrubber in a small bleed stream and sent to disposal, or regeneration of the active alkaline compounds. Use of tray-type wet scrubbers for sulfur dioxide removal has a number of advantages. The mobility of liquid absorbents is a major advantage because the reacting surface can be constantly and rapidly renewed by turbulence in the liquid, a very large area of reactive surface can be developed, recycling can be used to advantage in achieving high absorbent utilization, and absorbent solubility in aqueous systems makes absorbent molecules more accessible to the sulfur dioxide. Regeneration of spent scrubbing liquor is more applicable to utilities or refineries where very large amounts of sulfur dioxide must be removed and a strong economic incentive exists for regeneration of the alkaline absorbent for reuse.