The report gives results of an engineering analysis of the applicability of molecular sieve technology to the control of NOx emissions from nitric acid plants. Field test data from a plant using this technology show that, after 6 months of operation, the plant still controls NOx emissions to well within the New Source Performance Standard (NSPS) (1.5 kg of NOx/metric ton of acid; equivalent to about 200 ppm NOx in the tail gas). Field test data from a second plant, 10 months after start-up, show that NOx emissions are below the NSPS, even though the sieve had been accidentally damaged. The process appears able to achieve an average effluent NOx concentration of 50 ppm, based on tests at the former plant; however, this concentration was not achieved during the tests at the latter plant because of the damaged sieve. Although a 2-year sieve life has not been demonstrated, there is no reason to believe it cannot be achieved, and it appears that molecular sieve technology is technically feasible. The economic feasibility of molecular sieve technology for this application was assessed by comparing this technology with the catalytic reduction and extended absorption processes, both of which usually limit effluent NOx concentration to only about 200 ppm. The capitalized cost for the molecular sieve process is higher than for catalytic reduction and lower than for extended absorption.

Prepared by Battle-Columbus Laboratories, Columbus, Ohio, under contract no. 68-02-1323, Task 17, ROAP no. 21ADH-008, program element no. 1AB014. Appendix : p. A1-A10. Includes bibliographical references (pages 56-57).