Study of ammonia removal in coal gasification processes using integrated systems approach: Final report

Staged combustion was tested as an approach to controlling NO/sub x/ emissions from ammonia carryover in gasifier fuel streams. Conditions for testing simulated a combined cycle gasifier system with hot-gas cleanup and thus high fuel and air temperatures. Low-Btu GE fixed-bed gasifier and medium-Btu Texaco entrained-bed gasifier gas compositions were tested. Ammonia levels ranged from 500 to 10,000 ppM with 5000 ppM taken as the nominal concentration. Baseline tests were also performed with ammonia-free gas to evaluate thermal NO/sub x/ formation. Catalytic dissociation was also tested as an ammonia removal approach. The catalyst was a platinum/nickel combination on two monolith supports. Staged combustion produced a minimum NO/sub x/ level of 50 ppM (corrected to 15 percent O/sub 2/) at about 70 percent theoretical air for the fixed-bed simulated gas and 50 ppM at 50 percent theoretical air for the entrained-bed gas. Ammonia destruction ranged from 95 to 98 percent at the minimum NO/sub x/ condition. With both gas compositions, NO/sub x/ emissions asymptotically leveled off at high inlet ammonia levels. The Texaco medium-Btu gas composition produced a greater fraction of thermal to total NO/sub x/ with 5000 ppM inlet ammonia. The low-Btu GE simulated gas composition yielded only 6 tomore » 40 percent thermal NO/sub x/. NO/sub x/ emissions decreased with longer residence times and higher pressures. 24 refs., 61 figs., 14 tabs.« less