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Title: Optimal Integrated Design of Air Separation Unit and Gas Turbine Block for IGCC Systems

Abstract

The Integrated Gasification Combined Cycle (IGCC) systems are considered as a promising technology for power generation. However, they are not yet in widespread commercial use and opportunities remain to improve system feasibility and profitability via improved process integration. This work focuses on the integrated design of gasification system, air separation unit (ASU) and the gas turbine (GT) block. The ASU supplies oxygen to the gasification system and it can also supply nitrogen (if required as a diluent) to the gas turbine block with minimal incremental cost. Since both GT and the ASU require a source of compressed air, integrating the air requirement of these units is a logical starting point for facility optimization (Smith et al., 1997). Air extraction from the GT can reduce or avoid the compression cost in the ASU and the nitrogen injection can reduce NOx emissions and promote trouble-free operation of the GT block (Wimer et al., 2006). There are several possible degrees of integration between the ASU and the GT (Smith and Klosek, 2001). In the case of 'total' integration, where all the air required for the ASU is supplied by the GT compressor and the ASU is expected to be an elevated-pressure (EP) type.more » Alternatively, the ASU can be 'stand alone' without any integration with the GT. In this case, the ASU operates at low pressure (LP), with its own air compressor delivering air to the cryogenic process at the minimum energy cost. Here, nitrogen may or may not be injected because of the energy penalty issue and instead, syngas humidification may be preferred. A design, which is intermediate between these two cases, involves partial supply of air by the gas turbine and the remainder by a separate air compressor. These integration schemes have been utilized in some IGCC projects. Examples include Nuon Power Plant at Buggenum, Netherlands (both air and nitrogen integration), Polk Power Station at Tampa, US (nitrogen-only integration) and LGTI at Plaquemine, US (stand-alone). However, there is very little information on systematic assessment of air extraction, nitrogen injection and configuration and operating conditions of the ASU and it is not clear which scheme is optimal for a given IGCC application. In this work, we address the above mentioned problem systematically using mixed-integer optimization. This approach allows the use of various objectives such as minimizing the investment and operating cost or SOx and NOx emissions, maximizing power output or overall efficiency or a weighted combination of these factors. A superstructure is proposed which incorporates all the integration schemes described above. Simplified models for ASU, gas turbine system and steam cycle are used which provide reasonable estimates for performance and cost (Frey and Zhu, 2006). The optimal structural configuration and operating conditions are presented for several case studies and it is observed that the optimal solution changes significantly depending on the specified objective.« less

Authors:
; ; ;
Publication Date:
Research Org.:
National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States). In-house Research; National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States)
Sponsoring Org.:
USDOE Assistant Secretary for Fossil Energy (FE)
OSTI Identifier:
1014423
Report Number(s):
NETL-TPR-2483
TRN: US201113%%27
Resource Type:
Conference
Resource Relation:
Conference: AIChE Monday, November 9, 2009: 3:15 PM Lincoln D (Gaylord Opryland Hotel)
Country of Publication:
United States
Language:
English
Subject:
24 POWER TRANSMISSION AND DISTRIBUTION; COMBINED CYCLES; COMPRESSED AIR; COMPRESSION; COMPRESSORS; CONFIGURATION; CRYOGENICS; DESIGN; EFFICIENCY; ENERGY ACCOUNTING; GAS TURBINES; GASIFICATION; NITROGEN; OPERATING COST; OPTIMIZATION; OXYGEN; PERFORMANCE; POWER GENERATION; POWER PLANTS; STEAM

Citation Formats

Ravindra S. Kamath, Ignacio E. Grossmann, Lorenz T. Biegler, and Stephen E. Zitney. Optimal Integrated Design of Air Separation Unit and Gas Turbine Block for IGCC Systems. United States: N. p., 2009. Web.
Ravindra S. Kamath, Ignacio E. Grossmann, Lorenz T. Biegler, & Stephen E. Zitney. Optimal Integrated Design of Air Separation Unit and Gas Turbine Block for IGCC Systems. United States.
Ravindra S. Kamath, Ignacio E. Grossmann, Lorenz T. Biegler, and Stephen E. Zitney. Thu . "Optimal Integrated Design of Air Separation Unit and Gas Turbine Block for IGCC Systems". United States. doi:. https://www.osti.gov/servlets/purl/1014423.
@article{osti_1014423,
title = {Optimal Integrated Design of Air Separation Unit and Gas Turbine Block for IGCC Systems},
author = {Ravindra S. Kamath and Ignacio E. Grossmann and Lorenz T. Biegler and Stephen E. Zitney},
abstractNote = {The Integrated Gasification Combined Cycle (IGCC) systems are considered as a promising technology for power generation. However, they are not yet in widespread commercial use and opportunities remain to improve system feasibility and profitability via improved process integration. This work focuses on the integrated design of gasification system, air separation unit (ASU) and the gas turbine (GT) block. The ASU supplies oxygen to the gasification system and it can also supply nitrogen (if required as a diluent) to the gas turbine block with minimal incremental cost. Since both GT and the ASU require a source of compressed air, integrating the air requirement of these units is a logical starting point for facility optimization (Smith et al., 1997). Air extraction from the GT can reduce or avoid the compression cost in the ASU and the nitrogen injection can reduce NOx emissions and promote trouble-free operation of the GT block (Wimer et al., 2006). There are several possible degrees of integration between the ASU and the GT (Smith and Klosek, 2001). In the case of 'total' integration, where all the air required for the ASU is supplied by the GT compressor and the ASU is expected to be an elevated-pressure (EP) type. Alternatively, the ASU can be 'stand alone' without any integration with the GT. In this case, the ASU operates at low pressure (LP), with its own air compressor delivering air to the cryogenic process at the minimum energy cost. Here, nitrogen may or may not be injected because of the energy penalty issue and instead, syngas humidification may be preferred. A design, which is intermediate between these two cases, involves partial supply of air by the gas turbine and the remainder by a separate air compressor. These integration schemes have been utilized in some IGCC projects. Examples include Nuon Power Plant at Buggenum, Netherlands (both air and nitrogen integration), Polk Power Station at Tampa, US (nitrogen-only integration) and LGTI at Plaquemine, US (stand-alone). However, there is very little information on systematic assessment of air extraction, nitrogen injection and configuration and operating conditions of the ASU and it is not clear which scheme is optimal for a given IGCC application. In this work, we address the above mentioned problem systematically using mixed-integer optimization. This approach allows the use of various objectives such as minimizing the investment and operating cost or SOx and NOx emissions, maximizing power output or overall efficiency or a weighted combination of these factors. A superstructure is proposed which incorporates all the integration schemes described above. Simplified models for ASU, gas turbine system and steam cycle are used which provide reasonable estimates for performance and cost (Frey and Zhu, 2006). The optimal structural configuration and operating conditions are presented for several case studies and it is observed that the optimal solution changes significantly depending on the specified objective.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 2009},
month = {Thu Jan 01 00:00:00 EST 2009}
}

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  • The Integrated Gasification Combined Cycle (IGCC) systems are considered as a promising technology for power generation. However, they are not yet in widespread commercial use and opportunities remain to improve system feasibility and profitability via improved process integration. This work focuses on the integrated design of gasification system, air separation unit (ASU) and the gas turbine (GT) block. The ASU supplies oxygen to the gasification system and it can also supply nitrogen (if required as a diluent) to the gas turbine block with minimal incremental cost. Since both GT and the ASU require a source of compressed air, integrating themore » air requirement of these units is a logical starting point for facility optimization (Smith et al., 1997). Air extraction from the GT can reduce or avoid the compression cost in the ASU and the nitrogen injection can reduce NOx emissions and promote trouble-free operation of the GT block (Wimer et al., 2006). There are several possible degrees of integration between the ASU and the GT (Smith and Klosek, 2001). In the case of 'total' integration, where all the air required for the ASU is supplied by the GT compressor and the ASU is expected to be an elevated-pressure (EP) type. Alternatively, the ASU can be 'stand alone' without any integration with the GT. In this case, the ASU operates at low pressure (LP), with its own air compressor delivering air to the cryogenic process at the minimum energy cost. Here, nitrogen may or may not be injected because of the energy penalty issue and instead, syngas humidification may be preferred. A design, which is intermediate between these two cases, involves partial supply of air by the gas turbine and the remainder by a separate air compressor. These integration schemes have been utilized in some IGCC projects. Examples include Nuon Power Plant at Buggenum, Netherlands (both air and nitrogen integration), Polk Power Station at Tampa, US (nitrogen-only integration) and LGTI at Plaquemine, US (stand-alone). However, there is very little information on systematic assessment of air extraction, nitrogen injection and configuration and operating conditions of the ASU and it is not clear which scheme is optimal for a given IGCC application. In this work, we address the above mentioned problem systematically using mixed-integer optimization. This approach allows the use of various objectives such as minimizing the investment and operating cost or SOx and NOx emissions, maximizing power output or overall efficiency or a weighted combination of these factors. A superstructure is proposed which incorporates all the integration schemes described above. Simplified models for ASU, gas turbine system and steam cycle are used which provide reasonable estimates for performance and cost (Frey and Zhu, 2006). The optimal structural configuration and operating conditions are presented for several case studies and it is observed that the optimal solution changes significantly depending on the specified objective.« less
  • Parametric studies are conducted for optimizing the integration design between gas turbine compressor and air separation unit (ASU) of integrated gasification combined cycle (IGCC) power plant. The ASU is assumed as low pressure double-distillation column process which is integrated at the interstage location of the compressor, and integration design criteria of air extraction and reversing heat exchanger are defined and mathematically formulated. With the performance prediction of compressor by through-flow analysis, the effects of pinch-point temperature difference (PTD) in the reversing heat exchanger, the amount and the pressure of extracted air are quantitatively examined. As the extraction air amount ormore » the PTD is increased, the power consumption is increased. The compressor efficiency deteriorates as the increase of the flow rate of air extracted at higher pressure while improving at lower pressure air extraction. Furthermore, optimal integration condition for compressor efficiency maximization is found by generating the compressor characteristic curve.« less
  • Future IGCC plants with CO{sub 2} capture should be operated optimally in the face of disturbances without violating operational and environmental constraints. To achieve this goal, a systematic approach is taken in this work to design the control system of a selective, dual-stage Selexol-based acid gas removal (AGR) unit for a commercial-scale integrated gasification combined cycle (IGCC) power plant with pre-combustion CO{sub 2} capture. The control system design is performed in two stages with the objective of minimizing the auxiliary power while satisfying operational and environmental constraints in the presence of measured and unmeasured disturbances. In the first stage ofmore » the control system design, a top-down analysis is used to analyze degrees of freedom, define an operational objective, identify important disturbances and operational/environmental constraints, and select the control variables. With the degrees of freedom, the process is optimized with relation to the operational objective at nominal operation as well as under the disturbances identified. Operational and environmental constraints active at all operations are chosen as control variables. From the results of the optimization studies, self-optimizing control variables are identified for further examination. Several methods are explored in this work for the selection of these self-optimizing control variables. Modifications made to the existing methods will be discussed in this presentation. Due to the very large number of candidate sets available for control variables and due to the complexity of the underlying optimization problem, solution of this problem is computationally expensive. For reducing the computation time, parallel computing is performed using the Distributed Computing Server (DCS®) and the Parallel Computing® toolbox from Mathworks®. The second stage is a bottom-up design of the control layers used for the operation of the process. First, the regulatory control layer is designed followed by the supervisory control layer. Finally, an optimization layer is designed. In this paper, the proposed two-stage control system design approach is applied to the AGR unit for an IGCC power plant with CO{sub 2} capture. Aspen Plus Dynamics® is used to develop the dynamic AGR process model while MATLAB is used to perform the control system design and for implementation of model predictive control (MPC).« less
  • This appendix is a compilation of work done to predict overall cycle performance from gasifier to generator terminals. A spreadsheet has been generated for each case to show flows within a cycle. The spreadsheet shows gaseous or solid composition of flow, temperature of flow, quantity of flow, and heat heat content of flow. Prediction of steam and gas turbine performance was obtained by the computer program GTPro. Outputs of all runs for each combined cycle reviewed has been added to this appendix. A process schematic displaying all flows predicted through GTPro and the spreadsheet is also added to this appendix.more » The numbered bubbles on the schematic correspond to columns on the top headings of the spreadsheet.« less