SACR promises low NOx at low cost5 March 2002
Selective Auto-Catalytic Reduction, could be a powerful new weapon in the emissions reduction armoury.
SACR employs an injector grid to introduce hydrocarbons - natural gas, propane or diesel - plus ammonia into the boiler within an ideal temperature window in the upper cavity zone. The conditions create an autocatalytic chemical reaction (with autoignition and autothermal heating). The effect is to reduce NOx, as well as carbon monoxide and unburned carbon.
A particular advantage of the process is that the chemical reaction removes NOx with high efficiency but with minimal ammonia slip. Test results suggest that exhaust NOx is reduced to less than 120 mg/Nm3 (about 0.10 lb/MMBtu), while ammonia slip is estimated to be in the region of 2-4 ppm. Gas input is less than 0.15 per cent.
SACR, according to its developers, Mitsui Babcock, offers high levels of NOx reduction at a fraction of the cost previously encountered by plant operators for such emissions reduction performance.
Among the advantages claimed for SACR is that it is insensitive to coal type, so can be used with a wide range of traded coals. Also, the process has very little impact on plant output, while the implementation of the technology is cheaper than comparable systems available on the market. At a time when emissions reduction is becoming an increasingly important factor on all coal-fired plant operations, Mitsui Babacock believes SACR presents a cost-effective means of complying with legislation.
The technology is currently being demonstrating at a 200 MW plant in the United States in conjunction with a utility.
It is expected that SACR will be commercially available in both the USA and Europe within the year.