Treatment of Volatile Compounds from Municipal Solid Waste Pyrolysis to Obtain High Quality Syngas: Effect of Various Scrubbing Devices

Abstract

Volatile compounds produced from pyrolysis of municipal solid waste (MSW) are treated in a scrubbing system, which includes a hot char filter, a condenser cooled with ice water, a cooking oil scrubber, and a Na2CO3 solution scrubber, aimed at obtaining high quality syngas. The performances of each treatment device are evaluated at a laboratory scale. The results indicate that hot char filtration is able to capture 71% of particulates and 32% of the tar, and, thanks to its catalytic activity, syngas yield increased significantly from 0.21 to 0.39 m3N/kgMSW, and the molar percentage of combustible fractions in the syngas increased by 35%. The condenser can capture 90%, 85%, 87%, and 90% of evaporated Na, K, Ca, and Mg, respectively; 50% of particulates and 98% of the tar in the syngas. The cooking oil scrubber collected a major portion of tar, with 144 mg/m3N remaining in the syngas after scrubbing, and the dew point of the tar decreased below 50 °C. The scrubber filled with Na2CO3 solution of 5 wt% running at 70 °C and liquid/gas (L/G) ratio of 6 reduced the concentrations of tar and H2S in syngas to 38.5 mg/m3N and 16 ppm, respectively. Consequently, the tar dew point decreased to a level of about 25–30 °C, then acceptable for downstream applications, such as feeding of a gas engine. The results provide detailed information on the cleaning effects of various syngas cleaning units, their reciprocal influence and contributions to the total removal efficiency, which helps in choosing suitable options for volatile treatment to obtain high quality syngas from MSW pyrolysis.