Simulation of Chemical Substances Leakage Accident Consequence in the surroundings of Reservoirs by Using PHAST and ALOHA Consequence Modeling Software

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Abstract

In our country, in spite of the risks of exposure to chemicals, generally, there is not a planned program to respond to emergency situations due to the nature of the material and relevant risks, the risk level and scope of their expansion in a way that they be most effective in the shortest possible time. One of the important steps to manage the emissions of these gases is consequence modelling of their emission. In the meantime, models such as ALOHA (provided by United States Environmental Protection Agency, EPA) and PHAST because of better user interface and higher accuracy of results, have found wider application in the chemical industry and they have been used in this study.

Since the chemical and petrochemical industries often deal with operating units high-risk chemicals under high temperature and pressure such as reactors and storage reservoirs, so accidents such as explosions, fires and chemical leakage are probable. Evaluating and consequence of the risks such as hazardous chemicals release in the environment are of the most urgent and most important steps to increase the level of safety in existing or under construction units. The aim of this study was to determine the fire and explosion radius of toxic gas emissions scenarios from reservoirs, to determine toxicity safe and explosion radius with regard to the release of toxic gases from reservoirs based on NIOSH recommendations and also the effects of variables such as temperature, wind speed and direction on the statue of toxic gases release from the South Pars refinery reservoirs. In order to do this research, ALOHA, PHAST modelling methods have been used. The results of this study show that release of toxic and hazardous gases from pressurized reservoirs in similar scenarios, in winter, is more widespread than summer and variables such as temperature, wind speed and direction have significant effect on the statue of toxic gases release, the radius of the fire and explosion and variables such as temperature, wind speed and direction do not have significant effect on the statue of toxic gases release, the radius of the fire and explosion.

Introduction

Nowadays, world population increases along with the progress of civilization is so massive that it is called population explosion. Such an excessive increase has brought abundant social problems such as reducing the possibility food providing in developing countries, small houses in the world’s great cities, environmental pollution by industries in many countries etc. Among these major problems, environmental pollution has been raised as acute problem in recent years and it has been spread around the world gradually. During the last 30 years, environmental impacts have been increased to a very high rate because of several issues such as increasing world population, increasing consumption and industrial activity; although pollution has decreased to a certain level, but many environmental impacts, have grown in size and scale so much and have passed the identified threshold that beyond this threshold, the impact on human health and habitats can no longer be ignored (Meysami, 2013).

On the other hand, the chemicals have engaged extensively in human life and they are integral part of human life. But concerns about their effects on human health and the environment are global issues. There are now almost 575,000 chemical substances and every year, hundreds of new chemical enter the market. It is obvious that these materials can have varied health and environmental impacts depending on the type and combination of these materials. Thus, the same requirements should be considered for all chemicals that are produced or imported or used and necessary information should be provided to protect employees and consumers against the risks of chemical substances by reducing exposure, replacing hazardous materials and enforcing rules and regulations ((Hosseini Jenab et al., 2012).

In our country with the development of industry as well as petrochemical industry, the potential of industrial accidents is increasing. By considering this fact that the large numbers of employees are working in environments with potential danger of explosion and release of toxic substances and petrochemical plants adjacency to each other and inhabited cities, we will recognize the importance of having an emergency plan and also employees’ knowledge of this program in the industry (Langhari et al, 2010).

Release of toxic and dangerous substances in process and chemical industries is one of the threatening factors of working people and residents around these industries and it has been harmful to the environment (Etabi et al., 2010).

 

Determining the damage radius during an accident in line with the release of toxic gases is of utmost importance. Nowadays, modeling software is used for this purpose. This process is used to determine the margin of safety and danger. So that in case of such an event we can take away people from the danger zone and decrease the mortality rate (Tseng et al., 2012).

Conclusion:

As consequence modeling results show, planning emergency response in the operations area surrounding the release of toxic gases in the first phase of South Pars, is one of the necessary measures. We can also be confident in line with the efficiency of hydrogen sulfide gas detectors in the path of gas emissions. According to the results of propane reservoirs 1 and 3 scenarios modeling in the charts of ALOHA software in small leaks, variable such as temperature and wind speed, both in winter and in summer, according to in [Tables 2 and 3], has on significant effect spreading toxic substances, the radius of thermal radiation, safe and toxicity radius are obtained. Also detectors at the obtained distances show the leakage of toxic substances. But according to the results of scenario no. 2 modeling on the charts of PHAST software in small leaks, variable such as temperature and wind speed in summer and in winter do not have any significant impact on the spread of toxic substances, the radius of heat radiation, and explosion and safe radius. But in the large leaks in both models, expansion of toxic substances, the radius of thermal radiation, safe and explosion radius, according to [Tables 8 and 9] could have a significant impact.

References

  1. Etabi, F, Narimannejad, A., Khoshgard, A., (2011), Modeling sudden release of ammonia from storage and preparing an emergency response plans.
  2. Hosseini, Jenab., (2012), Chemicals Safety Information, Sharif university Publication.
  3. Langhari, M., Shahmohammadi, A, Rashtchiyan, D., (2010), Analysis of ALOHA and PHAST consequence modeling software, the First International Conference on oil and energy safety inspection.
  4. Meysami, H., Ebadi, T., Minne Pour, M., Ezazi Pour., (2013), The simulation of events consequences by  using PHAST software  and bases on choosing Worst case, the first International Conference on Process Engineering in Oil, Gas, Petrochemical and Energy.
  5. Tseng, j, (2012), Consequnce Evaluation of Toxic Chemical Release by ALOHA, International Symposium on Safety Science and Technology

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