Maximisation of an oil refinery profit with products quality and NO2 constraints

Today science and engineering are concerned with maximising profit while maintaining minimum air emissions from chemical plants such as oil refineries. Air emissions, such as NO2, when exists in large amounts, it could cause different types of serious diseases and illnesses. This research focuses on studying NO2 emissions from oil refineries while maintaining a maximum profit and the desired final products quality such as sulphur contents in fuel or octane number for gasoline. This paper aims to analyse the cost-profit of an oil refinery with the inclusion of Visbreaker unit. Visbreaker unit contribution to the revenue of oil refinery was not included in previous literature. The Economic power of Visbreaking unit in an oil refinery is given a good chance, for the first time in research work; to be evaluated economically and show its strength and money return to the plant with other product and NO2 constraints. The objectives of visbreaking are to reduce the viscosity of the feed stream, reduce the amount of residual fuel oil produced by a refinery and increase the proportion of middle distillates in the refinery output. In addition, the aim of the study is to find how to reduce NO2 emissions from oil refineries using different technologies while maintaining profit at maximum possible level using mathematical modeling approach. The three methods being used for NO2 reduction are; balancing, fuel switching and use of technology for NO2 reduction. NO2 emissions will be reduced by using the above three methods to reach different reduction percentage ranging from 20% to 80%. The profit of the oil refinery for each reduction target of NO2 was analysed and looked at closely. For example, at the 20% of NO2 reduction target, profits were $720 million. At the 80% reduction target, profits dropped down to $701 million. The contribution of Visbreaker to final products was calculated. For example, Visbreaker was responsible for adding 60,000 bbl of light and heavy naphtha to final products with total sales of around $6.0 million per year for this contribution. The model is mixed integer nonlinear (MINLP) and GAMS package is used to run a case study to validate the developed model. In addition to maximising profits, maintaining good quality products, reducing NO2 emissions and focus on Visbreaker products contributions is investigated deeply. (C) 2017 Elsevier Ltd. All rights reserved.