Development of a quantitative risk assessment method for a biomass gasification unit by combining DEMATEL-ISM and CM-TOPSIS

Once the safety of a biomass gasification unit is threatened, the leakage of syngas may result, which will have a great impact on humans, the environment, property and society. This study proposes a method for the risk assessment of biomass gasification units that integrates the DEMATEL-ISM with the CM-TOPSIS methods. The risk assessment process is divided into two stages. In the first stage, a directed hierarchical structure describing the relationships among accident factors can be obtained by using the DEMATEL-ISM method. The centrality, total degree and clustering coefficient are introduced to determine the weights of accident factors. The weight calculation results not only provide objectivity but also reflect the interrelationships among accident factors. In the second stage, CM-TOPSIS is used to calculate and prioritize the risks of accident factors. The results of risk values calculated by TOPSIS integrate the fuzziness and randomness of the assessment results of the CM, which can reduce the uncertainty of the results. More importantly, for high-risk factors, the directed hierarchical structure obtained in the first stage can be used to analyse the transmission routes of accident factors that lead to their occurrence. Finally, a case study and a comparative analysis are conducted to prove the effectiveness and applicability of the proposed method. The results show that pump and flow control valve failures are the highest risk accident factors. Moreover, the transmission routes that cause pump failure are determined and analysed for the purpose of safe production.