Pre-Combustion CO 2 Capture Technologies Treating Gaseous Fuels - EU-FP6-Project CACHET

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1 P R E P R I N T ICPWS XV Berlin, September 8 11, 2008 Pre-Combustion CO 2 Capture Technologies Treating Gaseous Fuels - EU-FP6-Project CACHET Dr.-Ing. Axel Gottschalk Process Design Center GmbH Joseph-von-Fraunhofer-Straße Dortmund Germany gottschalk@process-design-center.com Capture and storage of carbon dioxide (CO 2 ) with hydrogen (H 2 ) production from fossil fuels is a large-scale option for long-term emissions reduction with potentially global application. CACHET is a 3-year, integrated research project, funded by the European Commission and the international industrial/governmental CO 2 Capture Project (CCP). It aims to develop technologies to reduce greenhouse gas emissions from power stations by 90% with the potential to halve the incremental cost of low-carbon energy. The hydrogen produced can be used to provide energy, with water as the only by-product. Any improved economics may also be interesting for industrial processes, which use H 2 at large scale, such as crude oil refining, chemical manufacture and fuel cells for use in transport. CO 2 capture from natural gas fuel for large scale H 2 supply to fuel cells for use in transport or power generation will also be made more viable, improving the opportunity for the development of an H 2 fuelled economy ahead of the emergence of cost-effective renewable-based H 2 supply. Introduction The intention is that the CACHET processes will be ready for pilot-scale testing from 2009, precommercial demonstrations will follow and readiness for full-scale commercialisation is expected around Four pre-combustion capture technologies have been identified as the most promising for conversion of natural gas to H 2 while simultaneously capturing CO 2. Results achieved in the 1 st year of the CACHET project have been reported previously [1, 2]. This paper focuses on the consortium s substantial progress in each of the four technologies during the 2 nd year of the project. All members of the consortium (see Figure 1) have a strong desire to learn by doing. The highlights of this include the multicolumn Sorption Enhanced Water Gas Shift (SEWGS) unit at the Energy Research Centre of the Netherlands (ECN), the 120 kw chemical looping Figure 1: Project Partners of the EU-FP6-Project CACHET

2 reactor at the Technical University of Vienna and the cold mock-up unit to test catalyst loading and fluid dynamics in the HyGenSys reformer at Institut Français du Pétrole (IFP). The membrane team has successfully scaled-up membrane tubes by an order of magnitude and at ECN a new multi-tubular reactor is under construction for the next testing stage. The experimental aspects are well supported by on-going optimisation, integration, health, safety, environmental and economic evaluation to ensure a deep understanding of the potential of each of these technologies in true industrial scenarios. As independent consultant, the work of Process Design Center (PDC) focuses on the development of innovative process schemes applying the key technologies mentioned above. Based on technoeconomic evaluations, including mass- and energy balances and integration, a fair and significant comparison of the competing processes is ensured. Improvements in the reactor exchanger simulator, reactor tubes design and general arrangement with TECHNIP (France). Reactor bayonet concept, including material selection and mechanical design, were clarified. Detailed reactor design (see Figure 2) and cost optimisation by TECHNIP. Construction of the cold mock-up, which will demonstrate both the fluid dynanics and catalyst loading system. Advanced Steam Methane Reforming The advanced steam methane reforming technology incorporates a convectively heated reformer integrated with a gas turbine. This new process arrangement, having a high level of energy integration, leads to a co-generation of H 2 and electrical power that can be readily combined with CO 2 capture. The HyGenSys process proposed by IFP is an advanced steam reforming unit converting natural gas into syngas enabling pre-combustion CO 2 capture with an activated MDEA unit and production of H 2 rich fuel gas. The H 2 is used to provide the heat required for reforming and power production (based on Siemens 4000F gas turbine). The HyGenSys unit is composed of a combination of a hot gas generator (Siemens SGT-700), an advanced steam methane reformer including dedicated reactor exchanger, an expander (Dresser- Rand E-248) and a Heat Recovery Steam Generator. The pressurized hot exhaust gas from the hot gas generator transfers heat to the reaction and enables a high energy integration with additional power production. The following achievements and/or improvements have been made in the 2 nd year of the CACHET project: Further optimisation of the HyGenSys IFP simulations in accordance with the reactor/ exchanger, the Siemens turbines and the heat recovery calculations at the National Technical University of Athens (NTUA). Figure 2: HyGenSys reactor exchanger concept [3] Energy intensification has reduced both the number of HyGenSys trains from four to three and the number of absorbers of the amine unit from two to one. The net efficiency slightly increased to 44.5 % with a global CO 2 capture rate of 78 %. Economic evaluation by PDC. RedOx Technologies The RedOx technologies comprise three novel and highly innovative processes for integrating chemical looping into a process to produce H 2 from natural gas with simultaneous CO 2 capture, which use metal oxide particles for oxygen (O 2 ) transfer. The 1 st involves chemical looping combined with autothermal reforming, the 2 nd chemical looping with steam methane reforming and the 3 rd process features direct H 2 production with CO 2 capture: i) Autothermal chemical looping reforming, CLR(a) - a chemical-looping unit is used for 2

3 autothermal partial oxidation of the fuel in order to produce a nitrogen-free syngas without the penalties of an air-separation unit. ii) Integrated chemical looping steam reforming CLR(s) - a chemical-looping process is used as the heat source for a fluidised bed heat exchanger reformer (FBHE/R), fuelled by a waste stream from the H 2 /CO 2 separation, thus considerably reducing the penalties of gas separation. iii) One-step decarbonisation - a third process is added to the loop to split steam to produce H 2 directly and to avoid any separation of CO 2 and H 2. All processes provide very important advantages in reducing the efforts for gas separation in relation to H 2 production. Particles based on iron-, nickel-, manganese oxides as well as perovskites are being investigated and several of those have shown excellent performance, during continuous operation in 300 W and 500 W chemical-looping combustors. Several hundred hours of continuous operation confirm that there is no degradation of particles, that syngas without methane can be produced by CLR(a) and that low stoichiometric ratios suitable for CLR(a) are possible. Testing of particles has been successfully performed in pressurized semi-batch and semi-continuous units. Furthermore, scaling-up has been performed and a 100 kw chemicallooping combustor/reformer has been designed, built and put into operation. A model has been developed for the reactor system and will be validated by testing in the 100 kw unit, using kinetic data for the oxygen carriers, and provide a basis for preliminary design and costing of fullscale units Hydrogen Membrane Reactors Hydrogen membrane reactors are an attractive option for CO 2 capture in gas fired power stations because they combine the efficient conversion of natural gas into H 2 for power production with capture of the remaining CO 2, all in one reactor. They allow for one step reforming, or single step water gas shift reaction. The membrane reactors are integrated in a natural gas combined cycle, where the hydrogen is used for power generation while the remaining gas stream predominantly consists of CO 2 at relatively high pressure. The resulting H 2 rich gas stream can be used directly in a combined cycle gas turbine (CCGT) power plant. The objective is to develop and evaluate the potential of H 2 membrane reactors using palladium (Pd) or Pd-alloy membrane technology for the capture of CO 2. The membrane developers, i.e. SINTEF (Norway) and Dalian Institute of Chemical Physics (DICP) from China have succeeded in scaling up their membrane preparation methods. The developed membranes will now be tested under relevant process conditions in a Process Development Unit (PDU) for membrane reactor testing (see Figure 3), which is currently under construction. Retetante vent CH4 H2O H2 CO2 CO N2 H2O N2 Test rig in Permeate vent Gas analysis out Membrane reactor 8x Manifolding Figure 3: PDU test rig with membrane reactor [3] DICP now produces 50 cm long pure Pd membranes with 220 cm 2 separation area on a low cost ceramic support and capped with new high temperature/high pressure sealings provided by ECN, which allow operation up to 550 C and 38 bar. These membranes will be applied in water gas shift and steam reforming membrane reactors. SINTEF produces 50 cm Pd/Ag membranes prepared by a two-step method in which first the thin defect-free Pd-alloy film is prepared by sputtering deposition onto a perfect surface of a silicon wafer. In a second step the membrane is removed from the wafer and transferred to a porous stainless steel support. This allows preparation of thin (~ 2 µm) defect-free composite membranes with a film thickness that supports pore size ratios (m/m) less than one, which is two orders of magnitude smaller than typically obtained by conventional direct deposition techniques. SINTEF focuses on application of their membranes in the water gas shift membrane reactor. Both types of membranes have been tested extensively with H 2 /N 2 gas mixtures and in simulated feed gases for water gas shift and reformer membrane reactors. The membranes showed sufficient performance in terms of flux, stability and separation factors under relevant process conditions to start the actual construction of the PDU (see Figure 4). 3

4 Finally, single membrane tube reactor tests for both reforming and water gas shift that have been carried out affirm the principle of hydrogen membrane reactors i.e.: Parallel reaction and H 2 separation; Equilibrium shift towards high conversions; WGS reaction at increased temperature; Reforming at decreased temperature. CO 2 stream at low pressure, ready for compression and transport to a geological storage site or for use in enhanced oil recovery, and on the other hand an impure H 2 stream at high pressure and high temperature as ideal gas turbine fuel, diluted with nitrogen if necessary. The objective is to develop, and evaluate the potential of the SEWGS process. This will involve testing the performance of the preferred adsorbent/catalyst materials in a singlecolumn lab-scale test rig, demonstrating the fully cyclic process in a multi-column lab-scale test rig, using the generated process data to estimate industrial-scale performance, and quantifying the effect on the overall power production system incorporating SEWGS. In the 1 st project year a single column unit was constructed and used to gain confidence in the SEWGS process by running cyclically with adsorbent only. In the 2 nd project year work on the single column unit was extended to include both adsorption and shift reaction using a simulated syngas feed and the principle of Sorption Enhanced Water Gas Shift was demonstrated. Figure 4: PDU membrane reactor [3] Meanwhile, reactor modelling work at ECN and the techno-economic assessment work at PDC and NTUA showed that both membrane water gas shift and membrane reformer reactors are viable options for pre-combustion CO 2 capture in natural gas combined cycles power plant. Sorption Enhanced Water Gas Shift The Sorption Enhanced Water Gas Shift (SEWGS) process enables the production of hot high pressure H 2 in a catalytic water gas shift reactor with simultaneous adsorption of CO 2 at high temperature. The system is adsorbing and desorbing CO 2 in a cyclical steady state. The feed to the SEWGS unit is syngas from an autothermal reformer, after the high temperature shift reactor. The products are on the one hand a Figure 5: Six Bed SEWGS Unit [3] In addition, construction and commissioning of the multi-column unit took place (see Figure 5): six columns, each three times as tall as that in the single column unit that will allow full cyclic operation to be demonstrated in the lab. 4

5 In the meanwhile, work is also being carried out to optimise the SEWGS system, both in terms of improving the pressure swing SEWGS cycle to minimise the requirement for rinse and purge gases and also its integration into the overall power generation cycle. Novel Capture Technologies Beside the key technologies described above CACHET seeks out and assesses new, highpotential CO 2 capture concepts and applications. An assessment of the application of CACHET technologies to other H 2 production concepts concluded that CACHET technologies could potentially outperform conventional H 2 manufacturing technologies in ammonia production and refinery hydro-processing. The assessment also identified interesting synergies between gasifiers and H 2 membrane or sorbent enhanced water gas shift technologies. A survey and review of pre-combustion decarbonisation capabilities in Russia, AC countries and new member states, expanded the breadth of countries surveyed adding Bulgaria, Croatia, Cyprus, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Slovakia, Slovenia, and Turkey and increased the depth into countries previously reported, i.e. Poland, Romania and Russia. Survey results continue to indicate the research focus within these countries is predominantly on H 2 production for fuel cell vehicles rather than CO 2 capture. They also observe that, with the exception of Russia, natural gas reserves are limited, so capture from coal-based processes will be the likely direction of future CO 2 capture research. Distinctly different than Western European R&D, studies of hydrogen production using plasmas that produce elemental carbon are common in Russia, and Turkey is studying use of indigenous resources hydrogen sulfide for hydrogen and boron for sodium borohydrate carrier to use in a hydrogen infrastructure. A technical and economic assessment of highpotential capture concepts is currently evaluating the performance of some selected technologies based on sorbent enhanced reforming, CO 2 permeable membranes and micro-channel based reforming concepts. Process flowsheets and calculations have been developed to serve as the bases for assessing these concepts. Process Integration and Optimization Possible combinations of various CACHET key technologies are investigated. The goal is to arrive at an even more sustainable process for precombustion carbon capture by looking for synergies between different key technologies. Currently several promising combinations of technologies have been identified. The assessment of these concepts has been started. Summary and Conclusion An overview about technologies investigated in CACHET for H 2 production with CO 2 capture from natural gas was given. Considerable effort has been spent in designing and building large experimental equipment, which will help to increase understanding and confidence in each of the technologies at this larger scale. Techno-economic evaluation enables a fair comparison of the different key technologies both during and at the end of the CACHET-project. Further improvements are expected in the 3 rd and last year of CACHET due to the on-going process development and optimisation to improve the performance of the key technologies under investigation. Acknowledgements The author thanks and acknowledges the essential contribution from the European Commission (project no ), the CO 2 Capture Project (CCP) [4] and every one of the 28 partners in the consortium (see Figure 1), particularly those who have contributed to this paper. Literature [1] J. Forsyth: Carbon Dioxide Capture and Hydrogen Production from Gaseous Fuels CACHET : A New Project in EU FP6. Proceedings 8th International Conference on Greenhouse Gas Control Technologies (GHGT-8), 2006, Trondheim, Norway. [2] A. Gottschalk: CACHET: R&D of precombustion CO2 capture technologies treating gaseous fuels. ProcessNet 2007, Aachen, Germany, Chemie Ingenieur Technik, 79, No.9, (2007). [3] EU-FP6-Project CACHET: 2 nd Newsletter, April 2008, [4] CO2 Capture Project: 5