Process Economics Program Report 63
Sulfur Dioxide Removal From Stack Gases
Published: July 1970
This report is concerned primarily with the possibility of profitable recovery of sulfur or its compounds from coal fired electric power plant stack gases. Air pollution control requirements are also covered, concerning not only sulfur compounds but also particulates and nitrogen oxides.
The need for air pollution control changes the ground rules for comparison of processes. The evaluation is then not on the basis of whether a control plant is profitable compared with no control, but whether it is profitable compared with the cheapest control method, probably some form of alkaline injection, wet scrub process. That is, does the incremental income from a by-product justify the increased capital and operating costs necessary to obtain it? Such a comparison will make it easier to justify a recovery process as opposed to a non-recovery process, which has no salable by-product.
Because of extensive development work, certain processes have been commonly called "first generation," while others have been called "near first generation" or "second generation." The designation as first generation does not necessarily mean that the process is economically or even technically feasible, but only that it has been widely promoted earlier than the others.
To provide a sound basis for comparison, an extensive study was made of what constitutes a modern, large, fossil fuel power plant; what is the average fuel; and what is the average composition and amount of stack gas flow. The parallel problem of fly ash removal was also treated extensively, because processes for pollutant control are likely either to increase or decrease the cost of this expensive control job. Much of the fly ash portion of this study is applicable to the problem of particulate removal in situations unrelated to SO2 control.