Thermodynamic analysis of a novel solar-hybrid system for low-rank coal upgrading and power generation

摘要

This work proposed and analyzed an integrated solar hybrid system for upgrading and utilization of low rank coals using coal pre-drying, low-temperature pyrolysis and power generation, efficiently converting the low-rank coal into exportable value-added coal while generating electric power locally. The collected solar energy could be utilized in a cascade way to feed coal pre-drying and low-temperature pyrolysis. The low-energy density raw syngas discharged from the pyrolyzer is efficiently utilized by co-combusting with upgraded coal in the conjunct boiler and a large amount sensible heat of the upgraded coal is effectively recovered through pre-heating the condensate/feed water in the steam turbine unit. A case study for Zhundong lignite upgrading and utilization using the proposed system integrated with a typical 600 MW supercritical power plant was performed. The thermodynamic analysis results showed that, the overall energy and exergy efficiencies could reach 90.0% and 89.8%, respectively, with the product energy distribution ratio at 47.8 MJ/(kW h). The equivalent conversion efficiency of the coal upgrading process soars to 98.8% and the net solar-to-UGC efficiency reaches 49.4%. This proposed concept may provide a science and technology foundation for efficient utilization of the low-rank coal resources and a promising way to advance the solar energy utilization. (C) 2017 Elsevier Ltd. All rights reserved.