The combination of sorbent injection and selective noncatalytic reduction (SNCR)

The combination of sorbent injection and selective noncatalytic reduction (SNCR) technologies has been investigated for simulataneous SO2/NOx removal. A slurry composed of a urea‐based solution and various Ca‐based sorbents was injected at a range of temperatures and reactant/pollutant stoichiometries. Testing on a natural gas pilot‐scale reactor with doped pollutants achieved up to 80% reduction of SO2 and NOx at reactant/pollutant stoichiometric ratios of 2 and 1, respectively. SO2 emission reductions from slurry injection were enhanced compared with dry Ca(OH)2 sorbent injection methods possibly due to sorbent fracturing to smaller, more reactive particles. Emissions from NH3 slip and N2O formation were reduced in comparison with others' published results while similar NOx reductions were obtained. The injection of the urea‐based solution enhanced the SO2 removal, likely due to the formation of a (NH4)2Ca(SO4)2·H2O compound. The results of this pilot scale study have shown high reduction of both SO2 and NOx, suggesting the need for full scale studies to further assess this combined sorbent/urea‐based slurry injection technology.

The feasibility of using an integrated method consisting of physical coal cleaning, mild gasification (MG) and low temperature oxidation (LTO) to produce chars with SO 2 emissions at least 50% lower than those of their parent coals was studied. MG and LTO studies were conducted in both a batch fluidized-bed reactor (FBR) and in continuous feed reactors. Combustion properties of coal-char blends were determined at the U.S. EPA in a 14 kW pilot-scale combustor and ash deposition behaviors of selected fuels were determined at UNDEERC in a drop tube furnace (DTF). This project was cost-shared with the U.S. EPA and the U.S. DOE through UNDEERC. MG chars were prepared from six different coals in the FBR. Under non-optimized conditions, desulfurized chars with SO 2 emissions 60-71% lower than the parent coals were made, depending on the coal. Chars prepared from four of the six coals had SO a emissions less than 2.5 Ibs SO2/MMBtu. Treatment of a high chlorine coal reduced its chlorine content over 93%. Optimization of process conditions revealed that the greatest reduction in SO_ emissions was obtained using smaller particle diameters, steam during both MG and LTO, a higher temperature and higher oxygen partial pressure. For the only coal tested under optimized conditions, SO 2 emissions were reduced nearly 67%, from 4.60 to 1.49 ibs SO2/MMBtu. Over 150 pounds of chars were prepared in the continuous feed reactors. A total of about 350 pounds of different coal-char blends were prepared for tests at the U.S. EPA. These tests were completed July 31 and the results are currently being analyzed. Results of ash deposition tests at UNDEERC will be available for the final report.

The overall objective of this two-year program is to produce low sulfur char using an integrated process scheme which combines physical coal cleaning, mild gasification and char desulfurization. The goal of the project is to produce chars with 50% or more lower sulfur emissions than that of the parent coa!, and at minimum meet 1995 emission standards of 2.5 Ibs SO_/MMBtu. This project is a cooperativeeffort between the ISGS, UNDEERC and the U.S. EPA and is cost-sharedwith the U.S. EPA and the U.S. DOE through UNDEERC.