(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

The chemical looping concept has been well established as a useful means for producing power and liquid fuels while inherently reducing the energy and economic penalties associated with capturing CO₂, but it is far from commercial deployment. Continued research is essential to overcome remaining challenges, such as the development of high-performance, low-cost oxygen carriers (OC) and the design of reducers for solid fuel application that minimize the potential for solid agglomeration. Previously, the UKy-CAER described a viable method for OC synthesis, recycling waste from the aluminum industry, or red mud. Now, the UKy-CAER offers a potential solution to address the latter technology gap.

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 NO_x 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.