| 论文简介 |
Zhundong (ZD) coal comes from the largest coalfield in the world with a reserve of 390 billion tons. However, the high content of sodium and calcium in ZD coal causes severe fouling. Presently, no pulverized coal-fired furnace can burn ZD coal alone. In this study, kaolin addition is proposed to address fouling in a full-scale furnace burning ZD coal. Before performing a long-term full-scale furnace test, a series of fundamental studies in a thermogravimetric analyzer (TGA) and drop tube furnace was conducted to demonstrate the effectiveness of kaolin in reducing sulfates. The TGA results show that kaolin addition decreases the decomposition temperature of sulfates in coal ash by higher than 120 °C, and kaolin addition at 1150 °C eliminates all sulfates in the ash. Further experiments on ash deposition and particulate matter (PM) formation in a drop tube furnace at 1350 °C show that kaolin addition successfully eliminates severe ash deposition and fouling on probe surfaces and reduces the amount of PM1.0 by one-half. An analysis of the morphology and composition of fine particles and ash deposition clearly shows that kaolin addition reduces the formation of the sulfate aerosol and prevents its adhesion on the surfaces of larger ash particles. It further decreases the content of sulfur, sodium, and calcium in PM1.0. On the basis of the lab-scale studies, a 9-month long test was conducted in a 350 MW full-scale furnace burning ZD coal with kaolin addition. This long-term test shows that by reducing the average sodium and calcium content in ZD coal ash to 2.1 and 13.8 wt % through kaolin addition, severe ash deposition and fouling can be avoided. Elemental analysis of the fly ash also shows that the sulfur content after kaolin addition is only 1.8 wt %. By comparison, previous tests of coal cofiring without kaolin addition, conducted in the same furnace burning the same ZD coal, show more than 6.0 wt % of sulfur in fly ash. This study demonstrates that kaolin addition, which greatly reduces sulfates, is efficient in reducing fouling in furnaces burning ZD coal. |
(创新港)
