SOFC(Solid Oxide Fuel Cell)μ-CHP(Combined Heat and Power)System with Oxy-combustion Based on Oxygen Separation Membranes

摘要

Combined heat and power(CHP)based on solid oxide fuel cells(SOFC)offers a great promise for highly efficient power generation.For fuel cell technology high electrical and overall performance can be achieved already at the scale of single kilowatts.Alternative stack designs in different system configurations were considered.Numerous demonstration units operated on various fuels,exhibiting high LHV-based efficiency exceeding 40％and 85％,electrical and overall,respectively.Electrochemical power generation with fuel cells enforces substantial reduction of emissions typical for other energy conversion systems(NOx,SOx,heavy metals,etc.),however CO2 remains in the flue gas leaving SOFC-systems.In the new concept of a CCS-ready power generator with SOFCs,anode off-gas is combusted in high purity(above 99.5％)oxygen,yielding high concentration of CO2 in the exhaust stream after water is condensed.Such system can be equipped with carbon sequestration module,for example algae-based,placed downstream of afterburner and water condenser.Effective oxygen permeation rate of the perovskite oxygen transport membranes operating at high temperatures can exceed 10 Nml/(cm2 min)for LSCF(La0.6Sr0.4Co0.2Fe0.8O3?δ)or BSCF(Ba0.5Sr0.5Co0.8Fe0.2O3?δ)membranes.At this level,incorporation of membranes in the SOFC-based micro-CHP unit becomes technically feasible to achieve near zero-emission levels when system is coupled with CCS module.The system was studied using commercial modelling software.The micro-CHP unit with solid oxide fuel cells with air-combustion of anode off-gas was considered as a reference technology.Sensitivity analysis was performed focusing on the influence of permeation rate on a system efficiency.Efficiency penalty resulting from power consumption of membrane module varies in the 8-10％-point range.Results of the study clearly show that micro-power generators with SOFCs can be coupled with oxygen separation membranes for generation of CO2-rich exhaust stream.