Sliding Mode Control And Adaptive Control Of Micro Chemical Process For Hydrogen Production Via Methanol Reforming

Hydrogen has been considered as a possible alternative to fossil fuels because of its advantages of cleanness and high efficiency. However, its nature of low density, small molecules and explosiveness results in difficulties in storage and transportation. Therefore, people begin to explore hydrogen production by reforming of the liquid materials. Because of the adequate sources, high H:C ratio and moderate reforming temperature, methanol is considered as a suitable material for hydrogen production. Therefore, methanol reforming for hydrogen production has become a hot research topic, while the process control of methanol reforming is a problem has to be solved before application. Focusing on the process control of methanol reforming for hydrogen production, the main work of this paper is as follows:(1) The author participated in building a micro chemical experiment platform for hydrogen production through methanol reforming for verifying the control algorithm. The results of system identifications indicate that the uncertainty of methanol reforming model parameters is significant. The model parameters change with system conditions and catalyst activity.(2) A sliding mode controller is designed to counteract the model parameters uncertainty. Adaptive control is employed to reduce the switching frequency of control, which is beneficial to weakening the chattering. Meanwhile, the derivative of input is also employed to weaken the chattering. A high-gain observer is introduced to estimate the state variables which are used for feedback control. Considering the presence of interference in actual plant, an improvement is wired in the sliding mode controller to enhance the anti-interference capability.(3) An improvement is made for the adaptive controller designed by Sunan Huang et al.. Based on the errors are bounded, the system could be asymptotically stable under some conditions; the parameter k(t) is extended to a general form, which makes parameters selection more flexible; the interference has been taken into consideration and the controller could achieve good performance under interference. In addition, the adaptive controller still uses the derivative of the input to smooth the control input.(4) Based on the suitable ratios between inputs of methanol reforming, an overall control strategy is designed for the process of methanol reforming. The sliding mode controller and the adaptive controller are employed separately to manipulate the methanol flow and water flow. A variable ratio controller with restraint of reforming temperature is designed to manipulate the reforming air flow. Finally, the overall control strategy is applied on the experiment platform to verify its feasibility.