An environment friendly and efficient lignite-fired power generation process based on a boiler with an open pulverizing system and the recovery of water from mill-exhaust

Abstract

This paper advances a novel lignite-fired power generation process based on a OPSB (boiler with an open pulverizing system) and the recovery of water from mill-exhaust after the comprehensive analysis of the open pulverizing system used for high-moisture coals and heat/water recovery from boiler exhaust. Then, the thermal calculation method that applies to OPSB is presented based on heat and mass balance analyses of the boiler. Finally, an efficient unit applying the OPSB process is compared with a conventional 600 MW lignite-fired power unit, and the performance of the efficient unit is calculated and discussed in detail. The results show that the efficient unit not only yields a notable increase in the boiler's (2.6%) and the power plant's (1.3%) thermal efficiency but also provides a remarkable advantage in water recovery due to the mass of water vapor concentrated in mill-exhaust. In the efficient unit, the volume fraction of water vapor in mill-exhaust reaches 34%, the water reclaimed from mill-exhaust is so much that a lignite-fired power plant with zero water consumption can be expected, while the pollutant emissions can be reduced in proportion to the increase in boiler thermal efficiency.