275369 Modeling and Control Studies for the Elevated Pressure Air Separation Unit in an IGCC Power Plant

Monday, October 29, 2012
Hall B (Convention Center )
Kosan Roh, Hyojin Lee and Jay H. Lee, Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Korea

Korea is one of the highest energy consuming countries, being ranked at the 8th in the world in terms of total energy consumption. Unfortunately, it is extremely resource-poor and 97% of the total energy resource is currently being imported from abroad. Therefore, the Korean government is intent on improving the energy supply and demand situation for the reason of national energy security. Recently, IGCC (Integrated Gasification Combined Cycle) power plant is attracting lots of attention as an alternative system of generating electricity from coal in an eco-friendly way. The coal is gasified with oxygen to generate the syn-gas, which is composed of carbon monoxide and hydrogen. After going through several cleaning steps, the syngas is sent to the combined cycle unit for generating the electricity. IGCC gives a higher thermal efficiency than the conventional pulverized coal power plant. Also, it is easier to implement CCS(Carbon Capture and Storage) technology in an IGCC power plant for slowing down the climate change.

 However, the overall configuration is relatively complicated and also the level of integration among the units is very tight. The level of availability is often very low for an IGCC power plant because the operational know-hows and control strategies for IGCC power plants are yet to mature. Therefore, the plant-wide control study for an IGCC power plant is needed for its stable and efficient operation.

 Air Separation Unit (ASU) is a part of the IGCC power plant. It separates air into oxygen and nitrogen and sends them to the gasifier and the gas turbine. The ASU consumes about 10% of the gross power output and also accounts for about 15% of the total operating cost. Also, it introduces the largest time lag during the operation. Therefore, the operation of ASU should be optimized in order to achieve good control of the overall IGCC plant.

 In this research, Elevated Pressure Air Separation Unit (EP ASU) in an IGCC power plant is studied from the viewpoint of dynamic systems analysis. EP ASU, which is operated at a high pressure, is an improvement from the general ASU and gives significant energy savings. Firstly, equation-based modeling of the cryogenic rectification column in EP ASU has been carried out using the software platform of gPROMS. Also, the transient behavior in response to various disturbances is studied through the dynamic simulation. At the end, based on the dynamic analysis, PID controllers are applied to EP ASU for the product purity and flow rate control.

Acknowledgement

This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(2011-0006839).


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