Research On Safety Control Model Of Typical Chemical Process

Chemical industry occupies an important position in the national economy in China. Major accidents such as fire, explosion and poisoning occur frequently during the chemical production due to complex process, dangerous materials and strict conditions, cause large casualties and property losses. So the research on the safety control of the chemical process has important significance in theory and practice.Safety control model of the chemical process is built by exampled with the typical chemical process-methanol distillation based on the risk analysis and assessment. Hazard and operability analysis (HAZOP) and chemical process simulation are applied to accomplish the inherent safety design of the chemical process; according to the layers of protections analysis (LOPA) to analysis and the effectiveness assessment of the chemical protective layers. The appropriate protective layers are selected to perfect the safety control of the chemical process.According to the concept of the inherent safety design of the chemical process, using HAZOP method to analysis the risk of the process, the potential hazard and key process parameters that affect the process are found. The result of HAZOP can provide a detail basis for hazard control and inherent safety design. The distribution of the key process parameters of the key installations such as the temperature, flux, pressure and so on are simulated by applying the chemical process simulation. The simulation makes the traditional experience-based risk analysis and inherent safety design quantitatively, and perfects the inherent safety design from the safety control of the process further.The acceptable risk function of the chemical process is established based on the chemical accidents statistics analysis. The mathematical relationship between death toll and accident probability in the chemical accidents is derived, too. Combined with the accident consequence evaluation, the method to confirm the acceptable risk standard TP (Threshold Probability) of the scenes that may cause fire, explosion and poisoning accidents has been proposed in the paper.It is pointed out that people should select the appropriate protections to reduce the risk of the process after the inherent safety design. The LOPA method is applied to analyze the efficiency of the independent protections in the selected accident scenes that may cause fire, explosion and poisoning accidents. The mitigated probability (MP) of the scene can be got by the product of the PFDs (probability of failure on demand) of all the independent protective layers. The effectiveness of the protections is assessed by comparing of MP and TP. All the above efforts remedy the insufficient of the existing methods.Improving the major accident emergency ability is the last defensive line of the safety control of the chemical process, because the major accident emergency is the last layer of the protective layers. The emergency capability assessment indexes system to the major accident is built to assess the capability of dealing with the major accident in the paper. The emergency assessment solves the problem that the emergency can’t be quantified, and makes the protections analysis more completely.Finally, the concept and method about risk assessment of the chemical process are proposed based on the safety control model of the chemical process. The risk of the chemical process can be assessed by the value of the risk reduction factor (RRF).