Fuel, Vol.203, 964-972, 2017
Investigation of new control strategies for acid gas absorber columns to improve the response rates using dynamic process simulation
Increasing penetration of intermittent renewable sources of electrical energy such as wind or solar into the energy mix places an increasing demand on the flexibility of other power plant, in particular fossil fuel-based units. The suppliers of natural gas combined cycle equipment have been particularly successful in designing plants with increased ramp rates. In a recent review (Todd et al., 2014) EPRI has analysed the potential for using such equipment to improve the ramp rates of IGCC power plant. The review concluded that this was certainly possible, and identified the limiting equipment to be the acid gas removal system. Experience with such units in chemical applications has shown that at faster ramping rates than about 3%/min, the design sulfur specification cannot be maintained and a short-term sulfur breakthrough occurs. In that review it was postulated that this could be attributed to reduced solvent flow in the lower part of the column, while the hold-up required for higher load operation was being built up. Follow up work has been performed at the Technical University of Darmstadt to verify this hypothesis and propose mitigation measures. A typical tray column using a physical solvent was modeled, initially in ASPEN Plus and then in ASPEN Plus Dynamics. The dynamic model was calibrated against typical performance of industrial plant. The initial hypothesis could be verified and further refined. A number of proposals for mitigation measures were investigated and evaluated. The understanding gained by this work will be applicable also to packed columns and chemical solvents, though in the latter case the model will need to be extended to include kinetic effects. This paper describes the simulation work and a control strategy to improve the ramp rate of an acid gas removal system. (C) 2017 Elsevier Ltd. All rights reserved.
Keywords:Integrated gasification combined cycle;IGCC;Acid gas removal;AGR;Absorber column;Trayed column;Load changes;Dynamic behavior