A dynamic HAZOP case study using the Texas City refinery explosion

© 2016 Elsevier Ltd. The catastrophic explosion that occurred at Texas City on 23 March 2005 during the start-up of the raffinate splitter resulted in an estimated 15 deaths and 180 injuries. Since the incident, several studies have investigated the root causes of the disaster. Some contributing factors to the incident include wider organisational, process safety management, and human elements. There have also been some attempts to model the sequence of events before the incident, and the consequences of the resulting fires and explosions. This study provides a dynamic model of the sequence of events leading up to the incident and replicates the reported process variables during the isomerisation unit start-up on the day of the incident. The resulting simulation model is used as the framework for a dynamic hazard and operability (HAZOP) study

Applications of dynamic simulations in the process industries : a safety case study using Texas City refinery explosion

Although process safety performance in petroleum refineries is much better today compared to several decades ago, major accidents still occur occasionally. The explosion and fires at Texas City refinery on 23 March 2005 is regarded as one of the worst industrial accidents in US history to date. Dynamic process simulation provides an effective means to collect, collate and analyze data from previous incidents and offer recommendations of good practice to further improve process safety outcomes.A simulation of the sequence of events that led to the catastrophic explosions at Texas City refinery is presented in Aspen HYSYS. An initial steady state simulation of the operation of the raffinate splitter column at Texas City forms the basis for a subsequent dynamic simulation of the filling of the distillation column from 0213hrs until 1313hrs when the explosion occurred. A PID (proportional, integral, derivative) control scheme is implemented with appropriate tuning parameters.The dynamic simulation of the overall tower filling dynamics from 1000hrs to 1320hrs when the explosion occurred revealed that the feed to the column vaporised at approximately 1310 hrs. This happened as a result of the additional heat input into the column through the feed-product heat exchanger. Subsequently, thermal expansion of the liquid in the column led to the filling of the overhead vapour line with hydrocarbon liquids and an increase in pressure as a result of the hydrostatic liquid head. Flammable hydrocarbon vapours subsequently flowed from the overhead line through the collection headers into the blowdown drum. An alternative accident pathway is presented as the basis for a quantitative hazard and operability study, HAZOP

A systems engineering framework for the design of bioprocess operator training simulators

Operator training simulators (OTS) are widely used in several industries including chemical processing, oil and gas, medicine, aircraft and nuclear facilities. However, developing a biorefinery OTS is a complex engineering design activity that requires a structured technique. This paper presents a structured methodology that applies design frameworks from other disciplines and a user-centred approach for biorefinery OTS design. These include the definition of end user requirements (operator training needs), and the analysis of these requirements using Quality Function Deployment (QFD). Furthermore, an algorithm for bioprocess optimisation and automatic adjustment of operating parameters is developed for integration into the OTS. This algorithm is based on the Nelder-Mead simplex method for multi-dimensional function minimisation. Identified user requirements were categorized into primary, secondary and tertiary training needs, with increasing levels of detail from primary to tertiary needs. The relationships between identified operator training needs and OTS technical and functional specifications were investigated, and a priority rating assigned to the most important OTS specifications. Identified OTS specifications were evaluated for robustness to ensure that important features were not omitted from the final design

A systems engineering framework for the design of bioprocess operator training simulators

Operator training simulators (OTS) are widely used in several industries including chemical processing, oil and gas, medicine, aircraft and nuclear facilities. However, developing a biorefinery OTS is a complex engineering design activity that requires a structured technique. This paper presents a structured methodology that applies design frameworks from other disciplines and a user-centred approach for biorefinery OTS design. These include the definition of end user requirements (operator training needs), and the analysis of these requirements using Quality Function Deployment (QFD). Furthermore, an algorithm for bioprocess optimisation and automatic adjustment of operating parameters is developed for integration into the OTS. This algorithm is based on the Nelder-Mead simplex method for multi-dimensional function minimisation. Identified user requirements were categorized into primary, secondary and tertiary training needs, with increasing levels of detail from primary to tertiary needs. The relationships between identified operator training needs and OTS technical and functional specifications were investigated, and a priority rating assigned to the most important OTS specifications. Identified OTS specifications were evaluated for robustness to ensure that important features were not omitted from the final design

Operator training simulators for biorefineries: current position and future directions

Recent technological advances in the development of alternative energy sources, including biofuels, for transportation and energy requirements have demonstrated the need for highly skilled engineers and operators in the biotechnological industries. Although operator training simulators (OTS) used in the traditional chemical process industries may be used to train biorefinery operators and engineers, several distinct aspects of bioprocess operations make their direct application limited. The development and deployment of OTSs for use in biotechnological processes is therefore beginning to gain increasing attention. This review paper examines the present status of OTS development and use in biorefineries, including future considerations on how an OTS may be used to improve operator competence, maximise biorefinery operational efficiencies and protect people and the environment. The general premise of an OTS is that model‐based operator training simulators can be used to verifiably enhance the training of industrial operators to run complex biorefineries. Only a few examples of the design and application of OTSs in large‐scale biorefineries have so far been reported. A discussion of the mathematical models used for OTS development is briefly presented, as well as available OTS design frameworks and vendors, including their benefits and drawbacks. The review concludes by looking at possible future directions of OTS development and use in biorefineries and their contribution in facilitating the transition to a bio‐based economy. © 2018 Society of Chemical Industr