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Lima F.V.,University of Minnesota | Daoutidis P.,University of Minnesota | Tsapatsis M.,University of Minnesota | Marano J.J.,JM Energy Consulting
Industrial and Engineering Chemistry Research | Year: 2012

This paper investigates the alternative of precombustion capture of carbon dioxide from integrated gasification combined cycle (IGCC) plants using membrane reactors equipped with H 2-selective zeolite membranes for the water gas shift reaction. Specifically, a one-dimensional and isothermal membrane reactor model is developed. This model is used for simulation and optimization studies considering cocurrent and countercurrent modes of reactor operation. The simulation results indicate successful countercurrent cases that satisfy all of the specified targets and constraints. With use of this developed model, a novel optimization problem is formulated and solved to guide the selection of the optimal reactor design among typical scenarios of operation. The optimization results suggest as optimal solution a reactor design with a preshift followed by a membrane reactor. The obtained optimal design enables a more efficient membrane use by placing it in the optimal location. This design also results in savings of as high as 25% (in the range of 10-25%) in terms of membrane material when compared to the original membrane reactor design. For the price range of zeolite membranes considered on the order of $1000-10-000/m 2 and for large-scale applications, in which the membrane surface areas are on the order of 2000 m 2, 25% of savings implies cost reductions on the order of millions of dollars (as high as $5-000-000 in this case). © 2012 American Chemical Society. Source

Marano J.,JM Energy Consulting | Spivey J.J.,Louisiana State University | Morreale B.,U.S. National Energy Technology Laboratory
Chemical Engineering Progress | Year: 2015

Low-cost natural gas will invigorate the chemicals industry over the next decade, as producers look to increase the role of natural gas as a feedstock in established processes, as well as develop new processes to convert methane into chemicals currently derived from petroleum. Today, natural gas is the predominant feedstock for the production of ammonia, methanol, and hydrogen within the U.S. chemicals sector. Due to its chemical stability, methane is currently not converted directly into petrochemicals. Methane-derived synthesis gas is used in several areas outside of the U.S. to produce synthetic transportation fuel, lube oils, and waxes via the Fischer-Tropsch process. The mixed effluent stream is fractionated to purify ethylene and recover the byproducts, which are valuable intermediates for producing a variety of chemical products. While low-cost ethane is the preferred feedstock for ethylene production, using more ethane feedstock in place of petroleum-based feedstocks has had significant ramifications. Celanese, BP, and Eastman Chemical have made significant progress in catalyst development aimed at producing acetic acid, ethanol, and monoethylene glycol directly from synthesis gas. Source

Ciferno J.,U.S. National Energy Technology Laboratory | Marano J.J.,JM Energy Consulting
AIChE 2012 - 2012 AIChE Annual Meeting, Conference Proceedings | Year: 2012

Barring the imposition of a carbon tax (or equivalent cap-and-trade program) and corresponding international agreements, it is highly unlikely that carbon capture and storage/sequestration (CCS) will be implemented in any meaningful way in the near future. This is due to inherent inefficiency and higher costs associated with this option for mitigating climate change. Unfortunately, the science of climate change suggests that the world community must begin to act sooner rather than later. From an Industrial Ecology viewpoint, a preferable approach to carbon storage in perpetuity would be to re-use the carbon associated with the fossil-fuel derived CO2 already being omitted. However, options for directly utilizing CO2 are quite limited, with enhanced oil recovery (EOR) being the only physical use of CO2 of any appreciable size. The concept of converting CO2 to useful products has been explored in the past, but has fallen from favor in many policy circles due to the lack of a clear vision of how re-utilization of fossil carbon could be implemented. Given current in-action, it is worth re-visiting this concept. Energetically, it is clear that the large-scale conversion of CO2 to useful products requires a source of external energy that is not fossil-fuel derived; otherwise, the conversion process becomes itself a source of CO2 emissions. Sources for the required energy could be direct solar or nuclear energy, or electricity generated from these primary energy resources. Obviously, a source of CO2 is also required; however, all sources are of equal value. Atmospheric and mobile emissions are of little value due to the problems associated with collecting and concentrating them. Whereas, CO2 from stationary point sources, and in particular large point sources such as coal and natural gas-fired power plants, are the "low hanging fruit" for implementing carbon re-use. Finally, useful products from CO2 must be identified. It is suggested here that instead of pursuing a piecemeal approach consisting of an assortment of finished chemicals and material goods, a holistic approach be taken. Currently, the only existing commodity market that is big enough to absorb the large scale re-utilization of CO2 lies in the petroleum sector. Thus, the basis for any carbon re-utilization platform should be the production of a petroleum substitute, a "synthetic" oil that may be refined and converted into a multitude of finished products. This paper first compares and contrasts carbon storage with carbon utilization, and then moves on to quantify the scale of any carbon re-utilization effort; as well as, CO2 life-cycle limitations of re-use. After all, in this approach much of the synthetic oil, like petroleum, will end up being (re-) combusted as an end-use transportation fuel. Thus, carbon re-use can only be considered as an interim strategy for cost effectively transitioning away from fossil fuels. We also briefly touch on the implications of large scale carbon re-use for CCS R&D, since the requirements for CO2 capture, transport and short-term storage will be quite different than what is anticipated for long-term CO2 sequestration. Finally, we briefly discuss the possible economic implications of this strategy. A follow-on paper at this conference identifies and analyzes what the present and best future options for producing a CO2-derived synthetic oil might be. Source

Morrow W.R.,Lawrence Berkeley National Laboratory | Marano J.,JM Energy Consulting | Hasanbeigi A.,Lawrence Berkeley National Laboratory | Masanet E.,Northwestern University | Sathaye J.,Lawrence Berkeley National Laboratory
Energy | Year: 2015

The U.S. EPA is in the final stages of promulgating regulations to reduce CO2 emissions from the electricity generating industry. A major component of EPA's regulatory strategy targets improvements to power plant operating efficiencies. As the EPA expands regulatory requirements to other industries, including petroleum refining, it is likely that plant efficiency improvements will be critical to achieving CO2 emission reductions. This paper identifies efficiency improvement measures applicable to refining, and quantifies potential cost of conserved energy for these measures. Analysis is at the U.S. petroleum refining sector national-level employing an aggregated notional refinery model (NRM), with the aim of estimating the efficacy of efficiency improvements for reducing emissions. Using this method, roughly 1500 petajoules per year (PJ/yr) of plant fuel savings and 650 gigawatt-hour per year (GWh/yr) of electricity savings (representing 54% and 2% of U.S. refining industry consumption, respectively) are potentially cost-effective. This equates to a potential 85 Mt-CO2/yr reduction. An additional 458 PJ/yr fuel reduction and close to 2750 GWh/yr of electricity reduction (27 Mt-CO2/yr) are not cost-effective at prevailing natural gas market prices. Results are presented as a supply-curve ordering measures from low to high cost of fuel savings versus cumulative energy reduction. © 2015. Source

Lima F.V.,University of Minnesota | Daoutidis P.,University of Minnesota | Tsapatsis M.,University of Minnesota | Marano J.J.,JM Energy Consulting
11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings | Year: 2011

According to DOE projections, carbon dioxide (CO 2) emissions from the combustion of fossil fuels will exceed six billion metric tons by 2035. About one-third of these emissions originate from coal-fired electricity generation [1]. These emissions will need to be mitigated in order to reduce the impact of projected climate change within this century [2]. Thus, there is a need to develop new technologies for economical production of electricity from coal that minimize the release of CO 2 to the atmosphere. Integrated Gasification Combined Cycle (IGCC) power plants are a promising technology that can achieve higher efficiencies than conventional pulverized coal (PC)-fired plants. IGCC units also enable CO 2 capture with lower penalties in energy efficiency and cost of electricity than their PC counterparts [3]. In this presentation, we investigate the alternative of pre-combustion capture of CO 2 from IGCC plants using membrane reactors equipped with H2-selective molecular sieve (zeolite) membranes for the water gas shift (WGS) reaction. A challenge with using H2-selective membranes in the WGS section of coal-based gasification plants is their stability under high pressure and temperature conditions, and in the presence of steam and possibly other traces components such as hydrogen sulfide (H 2S). Typical membrane materials used or proposed for H2 separations as well as the issues associated with each group of materials under WGS conditions [4] are: (i) metals (typically Pd-based): high cost, stability in the presence of contaminants (H 2S) and H2 embrittlement; (ii) polymers: thermal degradation; (iii) amorphous silica: hydrothermal stability. Zeolite-based, molecular sieve membranes are one promising alternative for this application, as they are hydrothermally stable and have potential for high selectivity and flux [5]. The objective of this work is to develop a membrane reactor model for the WGS reaction using zeolite membranes. The developed model will be used for stand-alone simulation and optimization studies, and will ultimately be integrated into an IGCC system model. These studies aim to determine the membrane characteristics necessary to achieve the U.S. DOE R&D goal of 90% CO 2 capture [6] and to obtain desired H 2 recovery and CO conversion values. The desired targets should be reached for an optimal membrane use and without violating constraints in the reactor outlet streams, such as the retentate stream (rich in CO 2) for capture and sequestration and the permeate stream (rich in H 2) for power generation. Regarding the modeling task, we have developed a one-dimensional and isothermal shell and tube membrane reactor model for the WGS reaction. The model assumes the catalyst is packed in the tube side, a thin membrane layer is placed on the interior surface of the tube wall and the sweep gas flows in the shell side. This reactor model was simulated considering co-current and counter-current flow configurations to obtain steady-state compositions for primary species (CO, H 2O, CO 2, H 2 and N 2) present in the retentate and permeate streams. Several case studies have been performed assuming different membrane characteristics (permeance and selectivity). For each case study, we calculated the values of the membrane reactor parameters, such as CO conversion, H 2 recovery/productivity and CO 2 capture; and computed stream purities, such as the CO 2 purity in the retentate and H2 purity in the permeate. Target values for these parameters as well as constraints for the reactor streams were defined based on data reported by the DOE [7]. The simulation set up considers WGS reactor operating conditions that are taken from the literature and are consistent with IGCC units. Simulation results showed good agreement with published simulation data [8] and a better performance for the counter-current configuration when compared to the co-current mode. Regarding the optimization task, we formulated and solved a novel optimization problem using the developed membrane reactor model to guide the selection of the optimal reactor design among typical scenarios of operation, including: (i) pre-shift, membrane separator, WGS reactor; (ii) pre-shift, WGS membrane reactor; (iii) WGS reactor, membrane separator; (iv) stand-alone WGS membrane reactor. To address all of these design alternatives in one formulation, the decision variables considered in the problem were specified as the lengths associated with the reaction and permeation zones. The problem was solved with the objectives of maximizing the CO conversion and H2 recovery, while minimizing the cost of membrane used as a function of its surface area required. This problem was also subjected to the target specifications in the membrane reactor parameters and constraints in the retentate and permeate streams that were mentioned above. Optimization results indicated as optimal solution the reactor design with a pre-shift followed by a WGS membrane reactor and potential savings in membrane material when compared to the original membrane reactor design. Source

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