Energy Evaluation for Lignite Pyrolysis by Solid Heat Carrier Coupled with Gasification

Abstract

In order to utilize lignite in a clean and highly efficient way, an energy system for lignite pyrolysis by solid heat carrier coupled gasification is proposed in this study. The process is simulated and analyzed by Aspen Plus 11.1 on the basis of experimental data. The energy consumption distribution of the system and the mass ratio of the solid heat carrier to lignite, the most important technological parameters, are revealed. The choice of gasifier has the greatest impact on the energy efficiency of the system. Results show that, with a lignite handling capacity of 41.7 t•h −1 , the yields of tar and coal gasified gas are 1.6 and 25.7 t•h −1 , respectively, and 17% of the char is burnt to supply energy for the system while the remainder is used in the gasifier. Also, the surface moisture present in lignite and the phenol water from the tar can be utilized as the gasification agent in the coupled process, saving up to 8.9 t•h −1 water and decreasing the handling capacity of phenol water by 2.7 t•h −1 , thereby reducing the net volume of polluted water emitted by the system. It is possible for the system as a whole to achieve an energy efficiency of up to 85.8%. The study also shows that the majority of the energy used by the system is consumed during the drying and pyrolysis processes. Exploiting new technology, integrating and optimizing the energy use of the system to reduce energy consumption will be beneficial to improving the overall system performance.

Co-pyrolysis of lignite and Shendong coal direct liquefaction residue

“…2a. The HS content in co-pyrolysis of DLR of 0.425-0.85 mm with lignite decreased with the lignite particle size increasing, which is highly consistent with pyrolysis of lignite alone [15]. This is probably related to the low heating rate and the secondary reactions inside the large particles [14].…”

Assessment of low‐rank coal and biomass co‐pyrolysis system coupled with gasification

“…Therefore, tar ought to be simplified in the modeling. In this model, tar is assumed as a mixture of C 6 H 6 O, C 7 H 8 , and C 10 H 8 …”

“…The PR‐BM method is used to estimate the physical properties of conventional components. This method determines thermodynamic properties of compounds used in the system based on Peng‐Robinson cubic state equation along with Boston‐Mathias alpha function, and this method is recommended to be utilized in coal chemical simulations domain . Coal, biomass, char, and ash are considered nonconventional components which enthalpy and density are calculated through HCOALGEN and DCOALIGT in ASPEN plus, respectively.…”

“…However, low‐rank coal has unfavorable characteristics for combustion, like high moisture content, high ash content, and low heating value. As a result, low‐rank coal is neither environmentally friendly nor economically beneficial for combustion and the energy efficiency about lignite power plants is less than 38% . In recent years, the increasing demand for energy and the serious environmental problems have posed major challenges to energy production .…”

“…Rupesh studied air‐steam gasification of biomass with sorbent‐enabled CO 2 capture by ASPEN plus‐ and found that with CaO addition, H 2 mole fraction increased by 28.1% with a 42.6% reduction in CO 2 . Jie investigated energy consumption of lignite pyrolysis and gasification and found that drying and pyrolysis processes comprise approximately 85% of the total energy consumption. Snyder compared the costs of biomass slow pyrolysis, fast pyrolysis, and gasification and found that fast and slow pyrolysis are both promising approaches to reduce atmospheric CO 2 .…”