(741h) Advanced Control Automation System of the Syngas Chemical Looping Process: Dynamic Model Simulation and Controller Development

Authors: 
Hsieh, T. L., The Ohio State University
Xu, D., The Ohio State University
Fan, L. S., The Ohio State University
Tong, A., The Ohio State University
Over the last two decades of development, chemical looping has become an attractive energy and/or chemical production technology with near-zero CO2 emissions. In a chemical looping process, metal oxide particles serve as an oxygen carrier to indirectly convert carbonaceous fuels such as syngas, natural gas, coal or biomass into a concentrated stream of CO2 without the need for energy intensive gas-gas separation techniques. The metal oxide-based oxygen carrier supplies oxygen to the fuel from air via a cyclic reduction-oxidation reaction without direct contact of the fuel with the nitrogen-laden air stream. Ohio State University has been developing an advanced chemical looping technology which utilizes a unique moving bed design to maximize fuel conversion to concentrated CO2 and oxygen carrier conversion to minimize the solid circulation rate. Further, OSU has developed non-mechanical integrated reactor system that allows the oxygen carrier particles to circulate while preventing the gases present in each reactor from mixing. These concepts have been successfully demonstrated and scaled from laboratory testing to a 250kWth â?? 3 MWtbyh pilot plant constructed at the National Carbon Capture Center. One of the main challenges for operating the chemical looping unit at larger scale is the complexity of controlling and integrating multiple auxillary components simultaneously while maintaining proper operation of the chemical looping reactor system. Due to the interconnected nature of the reactor configuration and the high nonlinearity of the governing equations of the process dynamics, it is difficult to adjust or control the value of one process variable without manipulating multiple inputs. Therefore, the level of knowledge and experience required for the operators is relatively high to correctly perform state transitions between different operating conditions. The presented work seeks to develop a sophisticated control algorithm which is capable of performing automated action sequence to startup, maintain steady state and shutdown the chemical looping process. Multiple aspects of the project will be discussed, including the development of dynamic models of the SCL process, the design of a hybrid sliding mode controller structure, the instrument and equipment design for automation, and the test results of concept demonstration performed on the sub-pilot and pilot scale SCL units integrated with the developed control algorithms.