(329f) Improved Plant Efficiency and Reduced Process Complexity in a Coal-Fueled 50 Kwth Chemical Looping Combustion System with a Unique Spouted Fluidized Bed Reactor
AIChE Annual Meeting
Tuesday, October 30, 2018 - 2:15pm to 2:36pm
A 50 kWth dual-reactor CLC pilot plant has been constructed, commissioned and operated, verifying the effectiveness of each major component. The pilot plant includes a uniquely designed spouted bed fuel reactor, incorporating aspects from both bubbling and circulating fluidized bed reactors, in addition to features that enhance gas distribution and solids agitation. The turbulence minimizes axial and radial temperature and concentration gradients, promoting fast pyrolysis, tar cracking and preventing particle agglomeration. Parametric campaigns were conducted to study the effects of the following parameters on combustion efficiency and OC performance: operating pressure (1-4 bar), gasification agent ratios (CO2:H2O) and OC size (125-500 µm). This study demonstrated that CLC with a spouted bed as the reducer is a feasible coal-based power generation technology that can realize >95% CO2 separation efficiency, >97% combustion efficiency, and >90% in-line coal ash separation, while importantly preventing particles from adhering to each other, and thus, increasing the OC lifetime and plant productivity via the suggested fuel injection method. Additionally, tests suggested that the combustion process is further benefited by use of catalytic red mud oxygen carrier due to its high reactivity, significantly improving coal char gasification, high mechanical and thermal stability in cycling reactions and strong ability to convert in-situ syngas to CO2/H2O. Results also indicated favorable emission rates due to the near elimination of both prompt and thermal NOx formation when reacting at 950°C and in the absence of air. Process fluid dynamics and oxygen carriers appeared effective in preventing char slip and sulfur deposition, respectively, considering mass balances showed most of the fuel sulfur content was emitted directly from the reducer or retained in the ash.