Coal plays a vital role in electricity generation worldwide and is expected to contribute significantly to thermal power generation for the foreseeable future, especially in countries such as India. Carbon capture and sequestration technologies therefore become imperative in order to minimize CO2 emissions. A systematic and comprehensive assessment of the most promising of these technologies—consisting of supercritical boiler parameters, oxy-coal combustion, and low temperature flashing for simultaneous CO2 and SO2 capture—for typical Indian environmental and fuel conditions has been carried out in the present study. The results show that up to 93.3 % of CO2 and 95 % of SO2 generated during combustion can be captured while producing a sequestration-ready CO2 stream of 95.5 mol% purity compressed to a supercritical pressure of 110 bar. The energy penalty for this suite of technologies amounts to about 8.5 % drop in the net power plant efficiency to 33 % despite adopting efficiency measures such as supercritical boiler technologies. © 2016, Springer-Verlag Berlin Heidelberg.

Sreenivas Jayanti

Department Of Chemical Engineering

D. Kareemulla

Boilers

Carbon capture

Carbon dioxide

Coal

Energy efficiency

Environmental technology

Fossil fuel power plants

PLANT LAYOUT

PULVERIZED FUEL

Temperature

Carbon capture and sequestrations

CO2 ENRICHMENT

ENERGY PENALTIES

LAYOUT SIMULATIONS

Oxyfuel combustion

PULVERIZED COAL COMBUSTION

Thermal efficiency

Coal combustion

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Clean Technologies and Environmental Policy

CO2 capture from coal-fired power plants is necessary for continued use of coal as a fuel. Proven CO2 capture techniques such as amine absorption and oxyfuel combustion entail significant energy penalty leading to considerable decrease in the net thermal efficiency of the power plant. Recent studies of high-ash Indian coals show that CO2 has sufficient reactivity for coal gasification in temperature ranges of interest to IGCC. Against this background, we analyse in the present study, a new power plant layout which uses part of the sequestered flue gas stream for high-pressure gasification of the coal within the framework of an IGCC power plant with CO2 capture. Detailed thermodynamic calculations of the new plant layout, referred to here as Oxy-RFG-IGCC-CC, using commercial power plant simulation software show that the optimized Oxy-RFG-IGCC-CC plant with CO2 capture produces power at an overall thermal efficiency of 34.2%, which is nearly the same as that of current generation of pulverized coal boiler-based power plants without CO2 capture or that of a conventional IGCC with post-combustion capture. The proposed simpler layout is also 1.9% more efficient than a comparable CO2-capture-enabled IGCC plant that uses steam for coal gasification. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.

Improving efficiency of CCS-enabled IGCC power plant through the use of recycle flue gas for coal gasification

Detailed plant layout studies of oxy-enriched CO2 pulverized coal combustion-based power plant with CO2 enrichment

Gasification of solid fuels such as coals, lignite and biomasses has been studied using isothermal and non-isothermal thermogravimetric analysis (TG) with CO2 as gasifying agent. Non-isothermal TG of three Indian coals (two bituminous and one sub-bituminous coal), one lignite and two biomass fuels (Casuarina and empty fruit bunches) at a constant heating rate of 20 °C min-1 in the temperature range from 25 to 1200 °C showed a clear separation of DTG peaks associated with pyrolysis and CO2 gasification. Based on these studies, isothermal TG experiments were conducted in the temperature range from 900 to 1100 °C for coals and from 800 to 1000 °C for biomass fuels. These results show that the CO2 gasification rate follows coal rank for the three coals and the lignite. The two biomasses have significantly higher reactivities than the three coals. The higher reactivity of one coal is attributed to the presence of calcium-containing minerals in its inorganic matter. The kinetic parameters for each fuel were extracted from the isothermal TG results using the volumetric reaction model for the coals and a zeroth-order model for biomass fuels. Biomass and lignite are found to have a much higher reactivity index and much lower conversion time than the three coals under identical conditions. © 2015 Akadémiai Kiadó, Budapest, Hungary.

Journal of Thermal Analysis and Calorimetry

Evaluation of CO2 gasification kinetics for low-rank Indian coals and biomass fuels

Emission of carbon dioxide from fossil fuel-fired thermal power plants is a major concern for energy providers all around the world. In this context, carbon capture from thermal power plants and the energy penalty incurred in the process are important issues. The present work reports on a detailed analysis of gas-fired power plant layouts with in-built carbon capture, i.e. the flue gas from these power plants contains mainly carbon dioxide and water vapour. Four layouts, two of which are based on pressurized oxyfuel combustion and two on chemical looping combustion (CLC), have been considered. Based on detailed mass balance, energy and thermodynamic analyses of the power plant layouts, the net efficiencies for each plant have been computed. After accounting for thermodynamic irreversibilities and CO2 compression to 110 bar, these have been found to vary between 31 and 52 % for the four plants. Despite the technological maturity of oxyfuel combustion, it is concluded that CLC-based plants would be future-ready in the sense that they can readily accommodate CCS with only 2 % loss in overall thermal efficiency for CO2 capture. © 2015 Springer-Verlag.

Comparative analysis of four gas-fired, carbon capture-enabled power plant layouts

Of the various clean combustion technologies with carbon capture and sequestration (CCS) possibilities, chemical-looping combustion (CLC) promises to be an efficient and attractive method for oxidizing fuels without the energy penalty required for oxygen separation from air. The present work reports on a detailed thermodynamic analysis of 1,500 MWth, syngas-fueled, CLC-based power generation system which includes a provision for CCS. Taking account of the exothermic nature of the reaction of syngas with the selected oxygen carrier, NiO, in the fuel reactor, operating temperatures of air and fuel reactors are fixed at 900 and 908 °C, respectively. The CLC reactor system operates at atmospheric pressure on fuel/air side, and generates supercritical steam. An overall plant lay-out has been prepared such that the steam side, which is rated at 240 bar/538/552/566 °C, is very similar to that of a conventional thermal power plant making retrofitting a distinct possibility. A detailed analysis of the ideal cycle shows that a highly promising gross cycle efficiency of 41.22 % and net cycle efficiency of 36.77 % can be achieved after accounting for the energy cost of CO2 compression to 110 bar to facilitate CCS. © 2014 Springer-Verlag.

Syngas-fueled, chemical-looping combustion-based power plant lay-out for clean energy generation

Coal is the mainstay of electrical power generation in India. In this study, an experimental and theoretical assessment is made of the possibility of retrofitting an existing pulverized coal boiler for operation in oxy-coal mode. Experiments have been conducted using non-isothermal thermogravimetric analysis for a typical Indian coal to assess its reactivity under simulated oxy-coal combustion. Computational fluid dynamics simulations of a tangentially fired, 210 MWe pulverized coal boiler of a typical Indian design have been carried out with a typical Indian coal composition to study the relative effect of oxy-coal mode operation on the flow and heat transfer characteristics within the boiler. A process flow diagram has been developed for a 662 MWt power plant to include a retrofitted boiler and CO2 sequestration. It is concluded that a 70:30 volumetric mix of CO2 to O2 in the oxidizer composition will leave the essential features of the flow, temperature and heat transfer characteristics more or less unchanged, thus enabling retrofitting. An overall thermal efficiency loss of 11% is estimated for a retrofitted plant which delivers a flue gas which does not require chemical means of CO 2 sequestration. © IMechE 2012.

Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy

Assessment of retrofitting possibility of an Indian pulverized coal boiler for operation with Indian coals in oxy-coal combustion mode with CO2 sequestration

Journal	Data powered by TypesetClean Technologies and Environmental Policy
Publisher	Data powered by TypesetSpringer Verlag
ISSN	1618954X
Open Access	No