Development of Pre-treatment Process for Aceh Low-rank Coal by Simultaneously Capture of Sulfur and Trace Element

Abstract

Low-rank coal is a potential fuel for power plant, both for gas and steam turbine systems. Since the low-rank coal contain high fraction of sulfur and some trace metals, therefore burning of that coal will release SO₂ emission in flue gas and trace element particulates in fly ash. In order to suppress the SO₂ emission in flue and trace element (especially Hg) in fly ash, pulverized coal was mixed with bentonite (as desulfurizer and adsorbent) before subjected to furnace or burner. Introduce of bentonite hopefully can capture the sulfur compound (both in form of SO₂ and S) and trace element particularly mercury (Hg). Experimental was performed at desulfurizer/adsorbent content of 0, 2, 4, 6, 8, 10, 12, 14 and 16% (by weight) and burning temperature of 700, 800 and 900 ^oC. The 20 gr sample of coal-bentonite mixture with particle sizes -60/pan was put in the ceramic boat then placed in the Electric Tube Furnace. Air flow rate was fixed at 1.5l (l = stoichiometric air consumption) and reaction was run for 30 minutes. Sulfur and Hg retentions in bottom ash were analyzed using Spectrophotometer and AAS, respectively. It was found that the addition of bentonite can increase S and Hg retention in bottom ash. Maximum adsorption capacity of S and Hg was observed at bentonite dosage of 16% and combustion temperature of 700 ^oC. Adsorption efficiency for S reached up to 63.5%, while for Hg was 57.2%.

 

Keywords:Aceh low-rank coal; adsorbent; bentonite; bottom ash;desulfurizer;fly ash;SO₂ emission;traces element