Techno-economic assessment of membrane assisted fluidized bed reactors for pure H2 production with CO2 capture

This paper addresses the techno-economic assessment of two membrane-based technologies for H2 production from natural gas, fully integrated with CO2 capture. In the first configuration, a fluidized bed membrane reactor (FBMR) is integrated in the H2 plant: the natural gas reacts with steam in the catalytic bed and H2 is simultaneously separated using Pd-based membranes, and the heat of reaction is provided to the system by feeding air as reactive sweep gas in part of the membranes and by burning part of the permeated H2 (in order to avoid CO2 emissions for heat supply). In the second system, named membrane assisted chemical looping reforming (MA-CLR), natural gas is converted in the fuel rector by reaction with steam and an oxygen carrier (chemical looping reforming), and the produced H2 permeates through the membranes. The oxygen carrier is re-oxidized in a separate air reactor with air, which also provides the heat required for the endothermic reactions in the fuel reactor. The plants are optimized by varying the operating conditions of the reactors such as temperature, pressures (both at feed and permeate side), steam-to-carbon ratio and the heat recovery configuration. The plant design is carried out using Aspen Simulation, while the novel reactor concepts have been designed and their performance have been studied with a dedicated phenomenological model in Matlab. Both configurations have been designed and compared with reference technologies for H2 production based on conventional fired tubular reforming (FTR) with and without CO2 capture. The results of the analysis show that both new concepts can achieve higher H2 yields than conventional plants (12-20% higher). The high electricity consumptions of membrane-based plants are associated with the required low pressure at the retentate side. However, the low energy cost for the CO2 separation and compression makes the overall reforming efficiency from 4% to 20% higher than conventional FTR with CO2 scrubbing. FBMR and MA-CLR show better performance than FTR with CO2 capture technology in terms of costs mainly because of lower associated CAPEX. The cost of H2 production reduces from 0.28 €/NmH23 to 0.22 €/NmH23 (FBMR) and 0.19 €/NmH23 (MA-CLR)

Integration of the environmental management aspect in the optimization of the design and planning of energy systems

The increasing concerns regarding the environmental pollution derived from anthropogenic activities, such as the use of fossil fuels for power generation, has driven many interested parties to seek different alternatives, e.g. use of renewable energy sources, use of “cleaner” fuels and use of more effective technologies, in order to minimize and control the quantity of emissions that are produced during the life cycle of conventional energy sources. In addition to these alternatives, the use of an integrated procedure in which the environmental aspect will be taken into account during the design and planning of energy systems could provide a basis on which emissions reduction will be dealt with a life cycle approach. The work presented in this paper focuses on the examination of the possibilities of integrating the environmental aspects in the preliminary phase of the conventional design and planning of energy systems in conjunction with other parameters, such as financial cost, availability, capacity, location, etc. The integration of the environmental parameter to the design is carried out within a context where Eco-design concepts are applied. Due to the multi-parameter nature of the design procedure, the tools that are used are Life Cycle Analysis and Multi-criteria Analysis. The proposed optimization model examines and identifies optimum available options of the use of different energy sources and technologies for the production of electricity and/or heat by minimizing both the financial cost and the environmental impacts, with regard to a multiple objective optimization subject to a set of specific constraints. Implementation of the proposed model in the form of a case study for the island of Rhodes in Greece revealed that an optimized solution both cost and environmental-wise, would be an almost balanced participation of renewables and non-renewable energy sources in the energy mix

Preliminary chemical engineering plant design

xv+572hlm.;24c