Conceptual Design of a 1.46-Million Tons-Per-Year Lignite Preparation Facility for Sodium Reduction

摘要

A conceptual design is presented for a preparation facility processing 1.46 million tons per year (4000 tpd) of lignite in which the sodium content of the total product is reduced from 8.5 to 4 pct (as Na sub 2 O in ash). Sodium removal from the lignite is by ion exchange using hydrogen ions from aqueous sulfuric acid. Limited experimental data were obtained using a bench scale continuous countercurrent ion exchange unit for design purposes. The design of the ion exchanger, the lignite washing and dewatering facilities, and the waste water clean-up steps are included. Complete material balances and energy requirements are presented. A brief discussion of instrumentation and process control is given. Most equipment can be obtained commercially. To limit the environmental impact, extensive cleaning and reuse of process water are employed. Waste effluent is discharged to an evaporation pond. The total capital investment was estimated to be $21.88 million in mid-1979 dollars with annual operating costs of $6.08 million. The unit processing cost was determined at $4.17 per ton of lignite input. Raw materials represent 9 pct of the unit cost, whereas finance charges are nearly 32 pct. It was concluded that this ion exchange process is technically feasible, and in certain favorable circumstances, may be economically viable. (ERA citation 08:000081)