Full Length Article Investigation of new control strategies for acid gas absorber columns to improve the response rates using dynamic process simulation Christian Heinze a,⇑ , Chris Higman b , Jose Marasigan c , Bernd Epple a a TU Darmstadt, Institute for Energy Systems and Technology, Darmstadt, Germany b Higman Consulting GmbH, Schwalbach am Taunus, Germany c Electric Power Research Institute (EPRI), Palo Alto, USA article info Article history: Received 13 October 2016 Received in revised form 23 March 2017 Accepted 28 March 2017 Available online xxxx Keywords: Integrated gasification combined cycle IGCC Acid gas removal AGR Absorber column Trayed column Load changes Dynamic behavior abstract 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 perfor- mance of industrial plant. The initial hypothesis could be verified and further refined. A number of pro- posals 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. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Intermittent renewable sources, notably wind and solar power, are often considered ‘‘must-takes” for a utility due to their negligi- ble fuel costs, low emissions, and regulatory constraints. Because these resources can vary in output from 0% to 100% over a short period, other generating resources must cycle to accommodate these variations. The existing units called on for this cycling response will vary by location and fuel prices. In many parts of the world, depending on the make-up of the existing generator fleet, natural gas prices, and the extent of renewables penetration, such cycling may be largely accomplished by natural gas combined cycle (NGCC) and simple cycle gas turbine plants. However, in others, coal plants will be called upon to handle more renewables-driven cycling service. The necessity for improved flexibility for coal-fired power plants has been highlighted in a number of conferences over the last year or two, e.g. [2]. Like most coal-based generating units, integrated gasification combined cycle (IGCC) plants have been typically designed to operate at base load, but they do embody characteristics that can make them particularly suitable for cycling service. The current IGCC operating experiences demonstrates http://dx.doi.org/10.1016/j.fuel.2017.03.086 0016-2361/Ó 2017 Elsevier Ltd. All rights reserved. Abbreviations: AGR, acid gas removal; ASPEN, Advanced System for Process Engineering; EPRI, Electric Power Research Institute; IGCC, integrated gasification combined cycle; MDEA, methyldiethanolamine; MEA, monoethanolamine; NGCC, natural gas combined cycle; RKSWS, Redlich-Kwong-Soave with Wong-Sandler mixing rules; RRA, Rapid Response Absorber. ⇑ Corresponding author at: TU Darmstadt, Institut Energiesysteme und Energi- etechnik, Otto-Berndt-Str. 3, 64287 Darmstadt, Germany. E-mail address: christian.heinze@est.tu-darmstadt.de (C. Heinze). Fuel xxx (2017) xxx–xxx Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel Please cite this article in press as: Heinze C et al. Investigation of new control strategies for acid gas absorber columns to improve the response rates using dynamic process simulation. Fuel (2017), http://dx.doi.org/10.1016/j.fuel.2017.03.086