Performance and Economic Analysis of Biomass/Coal Co-Gasification IGCC Systems With Supercritical Steam Bottom Cycle: Part 1 — Post-Combustion Carbon Capture

2012 ◽  
Author(s):  
Ting Wang ◽  
Henry A. Long
Keyword(s):  
Carbon Capture ◽  
Ghg Emissions ◽  
Combined Cycle ◽  
Production Costs ◽  
Low Grade ◽  
Integrated Gasification Combined Cycle ◽  
Lower Efficiency ◽  
Capital Costs ◽  
Reduce Emissions ◽  
Steam Cycle

In recent years, Integrated Gasification Combined Cycle (IGCC) technology has been gaining steady popularity for use in clean coal power operations with Carbon Capture and Sequestration (CCS). This study focuses on investigating two approaches to improve efficiency and further reduce the greenhouse gas (GHG) emissions. First, replace the traditional subcritical Rankine steam cycle portion of the overall plant with a supercritical steam cycle. Second, add different amounts of biomass as feedstock to reduce emissions. Part 1 focuses on investigating post-combustion CCS and Part 2 on analyzing pre-combustion CCS, using both sour-shift and sweet-shift processes. Employing biomass as a feedstock has the advantage of being carbon neutral or even carbon negative if CCS is implemented. However, due to limited feedstock supply, such plants are usually small (2–50MW), which results in lower efficiency and higher capital and production costs. Considering these challenges, it is more economically attractive and less technically challenging to co-combust or co-gasify biomass wastes with coal. Using the commercial software, Thermoflow®, this study analyzes the baseline plants around 235MW and 267 MW for the subcritical and supercritical designs, respectively. The results clearly show that utilizing a certain type of biomass with low-grade coals up to 50% (wt.) can, in most cases, not only improve the efficiency and reduce overall emissions, but may be economically advantageous, as well. The CO2 emissions decrease by about 7,000 tons/MW-year, making both plants carbon-negative with only 10% biomass in the feedstock. In addition, implementing a supercritical steam cycle raises the efficiency (1.6 percentage points) and lowers the capital costs ($300/kW), regardless of plant layout. Implementing post-combustion CCS consistently causes a drop in efficiency (at least 7–8 points) from the baseline, and increases the costs by $3,000-$4,000/kW and $0.06-$0.07/kW-hr. The SOx emissions also decrease by about 190 tons/year (7.6 × 10−6 tons/MW-year), while the NOx emissions are all but eliminated through post-combustion CCS. Finally, the CCS cost is around $65-$72 per ton of CO2.

A System Performance and Economics Analysis of IGCC With Supercritical Steam Bottom Cycle Supplied With Varying Blends of Coal and Biomass Feedstock

2011 ◽  
Author(s):  
Henry A. Long ◽  
Ting Wang
Keyword(s):  
Carbon Capture ◽  
Ghg Emissions ◽  
Capital Cost ◽  
Combined Cycle ◽  
Production Costs ◽  
Integrated Gasification Combined Cycle ◽  
Cost Of Electricity ◽  
Biomass Ratio ◽  
Integrated Gasification ◽  
Steam Cycle

In recent years, Integrated Gasification Combined Cycle Technology (IGCC) has been gaining steady popularity for use in clean coal power operations with carbon capture and sequestration. Great efforts have been continuously spent on investigating various ways to improve the efficiency and further reduce the greenhouse gas (GHG) emissions of such plants. This study focuses on investigating two approaches to achieve these goals. First, replace the traditional subcritical Rankine steam cycle portion of the overall plant with a supercritical steam cycle. Second, add different amounts of biomass as co-feedstock to reduce carbon footprint as well as SOx and NOx emissions. Employing biomass as a feedstock to generate fuels or power has the advantage of being carbon neutral or even becoming carbon negative if carbon is captured and sequestered. Due to a limited supply of feedstock, biomass plants are usually small, which results in higher capital and production costs. In addition, biomass can only be obtained at specific times in the year, meaning the plant cannot feasibly operate year-round, resulting in fairly low capacity factors. Considering these challenges, it is more economically attractive and less technically challenging to co-combust or co-gasify biomass wastes with coal. The results show that supercritical IGCC the net plant efficiency increases with increased biomass blending in the all cases. For both subcritical and supercritical cases, the efficiency increases initially from 0% to 10% (wt.) biomass, and decreases thereafter. However, the efficiency of the blended cases always remains higher than that of the pure coal baseline cases. The emissions (NOx, SOx, and effective CO2) and the capital cost all decrease as biomass ratio increases, but the cost of electricity increases with biomass ratio due to the high cost of the biomass used. Finally, implementing a supercritical steam cycle is shown to increase the net plant output power by 13% and the thermal efficiency by about 1.6 percentage points (or 4.56%) with a 6.7% reduction in capital cost, and a 3.5% decrease in cost of electricity.

Comparison of Preanode and Postanode Carbon Dioxide Separation for IGFC Systems

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Eric Liese
Keyword(s):  
Fuel Cell ◽  
Power Density ◽  
Co2 Capture ◽  
Coal Gasification ◽  
Combined Cycle ◽  
Energy Technology ◽  
Integrated Gasification Combined Cycle ◽  
Lower Efficiency ◽  
Integrated Gasification ◽  
Cold Gas

This paper examines the arrangement of a solid oxide fuel cell (SOFC) within a coal gasification cycle, this combination generally being called an integrated gasification fuel cell cycle. This work relies on a previous study performed by the National Energy Technology Laboratory (NETL) that details thermodynamic simulations of integrated gasification combined cycle (IGCC) systems and considers various gasifier types and includes cases for 90% CO2 capture (2007, “Cost and Performance Baseline for Fossil Energy Plants, Vol. 1: Bituminous Coal and Natural Gas to Electricity,” National Energy Technology Laboratory Report No. DOE/NETL-2007/1281). All systems in this study assume a Conoco Philips gasifier and cold-gas clean up conditions for the coal gasification system (Cases 3 and 4 in the NETL IGCC report). Four system arrangements, cases, are examined. Cases 1 and 2 remove the CO2 after the SOFC anode. Case 3 assumes steam addition, a water-gas-shift (WGS) catalyst, and a Selexol process to remove the CO2 in the gas cleanup section, sending a hydrogen-rich gas to the fuel cell anode. Case 4 assumes Selexol in the cold-gas cleanup section as in Case 3; however, there is no steam addition, and the WGS takes places in the SOFC and after the anode. Results demonstrate significant efficiency advantages compared with IGCC with CO2 capture. The hydrogen-rich case (Case 3) has better net electric efficiency compared with typical postanode CO2 capture cases (Cases 1 and 2), with a simpler arrangement but at a lower SOFC power density, or a lower efficiency at the same power density. Case 4 gives an efficiency similar to Case 3 but also at a lower SOFC power density. Carbon deposition concerns are also discussed.

Evaluation of Using Supercritical Rankine Cycles in Integrated Coal Gasification Combined Cycles (IGCC)

2017 ◽  
Author(s):  
Henry A. Long ◽  
Ting Wang ◽  
Arian Thomas
Keyword(s):  
Coal Gasification ◽  
Energy Resource ◽  
Rankine Cycle ◽  
Combined Cycle ◽  
Modern World ◽  
Integrated Gasification Combined Cycle ◽  
Combined Cycles ◽  
Reduce Emissions ◽  
Integrated Gasification ◽  
Cycle Efficiency

Coal is a prominent energy resource in the modern world, particularly in countries with emerging economies. In order to reduce emissions, it is necessary to find a way to utilize coal in a cleaner manner, such as through supercritical and ultra-supercritical Rankine cycles and the Integrated Gasification Combined Cycle (IGCC). Two approaches — raising the boiler pressure and using a reheat scheme — have been proven to notably increase the Rankine cycle efficiency. Thus, this study aims to investigate the effects of implementing reheat and supercritical or ultra-supercritical pressure in the bottom Rankine cycle on the IGCC cycle efficiency. First, reference cases of a standalone Rankine cycle were studied with single and double reheat, including boiler pressure levels from subcritical to ultra-supercritical conditions, followed by similar combined cycle cases, and finally IGCC systems. The results indicate that the notable efficiency enhancement in the standalone subcritical Rankine cycle do not prevail in the studied IGCC systems. Thus, it is not economically worthwhile to implement supercritical or ultra-supercritical bottom Rankine cycles in IGCC applications.

Sign in / Sign up

Export Citation Format

Share Document