Experimental characterization of a high sulfur Hungarian brown coal for its potential industrial applications

摘要

Differently from the conventional combustion and entrained flow gasification technologies, fixed-bed up-draft gasification process tested in pilot scale appears very suitable for the "multipurpose transformation" of Hungarian low-rank and high sulfur brown coal (for the production of electrical energy, heat and eventually gaseous or liquid fuels). This paper presents the positive results of the wide-range analysis (led jointly by Sotacarbo in Italy and by Ormosszen in Hungary) on the possibility to use the Hungarian coal from the North-East basins for energy purposes. At this stage, there is no scientific literature on this subject (the energetic use of this fuel, which is very complex in conventional power generation plants), whereas there are several studies on the geological properties of the Hungarian brown coal and on the energetic exploitation of the Mecsek basin's high-rank coal. In addition to the conventional characterization (proximate, ultimate and thermal analyses), a series of bench-scale experimental tests were carried out to preliminary assess the combustion performance of Hungarian brown coal and to set a pilot-scale experimentation in the Sotacarbo gasification pilot plant As results from the experimental tests, the air-blown up-draft gasification of about 11 kg/h of Hungarian brown coal allows to produce about 24-25 kg/h of raw syngas, characterized by a lower heating value of 3.55 MJ/kg. The high sulfur content in primary fuel is one of the main problems when that coal is used. As a matter of fact, conventional cold gas desulfurization processes are typically not sufficient for an efficient syngas desulfurization. But a very high H2S and COS removal efficiency has been experimentally obtained treating syngas with a zinc oxide-based hot gas desulfurization system. This process allowed to obtain a final H2S and COS global concentration lower than 20 ppm (by volume), operating at about 400 °C.