At present, the modeling method used in the batch process by signed directed graph (SDG) is oriented to the process in normal running state, which cannot describe the operating logic in abnormal running state, and it is inadequate to cover all faults and hazards.When the SDG model used for computer-aided hazard and operability study (HAZOP) is built for the complex chemical process including the batch process, the model of the batch process cannot always be associated to that of the other continuous systems.In order to meet the demand of computer-aided HAZOP, the paper presents a dynamic SDG modeling method based on the present SDG-HAZOP modeling method to deal with the batch process.The idea and procedures of dynamic modeling were elaborated.A real case about the fly ash removal in a complex process of coal-to-oil was modeled and analyzed by using the proposed method, which can resolve two problems at the same time: the sequential model about the SDG modeling of the batch process and the maximal covering of the faults and hazards.
