چكيده به لاتين
Wax precipitation is one of the serious problems in oil refineries. The presence of wax in petroleum, oils and diesel fuel leads to clogging in pipelines, car filters and air pollution. To prevent these problems, it is necessary to know exactly the nature of wax and how it is precipitated. it is necessary to Know the nature of wax for converting wax into valuable products. The catalytic dewaxing unit is the most well-known technology for converting wax into valuable products such as gasoline and kerosene. In the catalytic dewaxing unit, using catalysts such as zeolite and nickel, the normal paraffins of the feed are converted into branched isoparaffins, and the amount of wax in the feed is reduced and they are converted into gasoline and kerosene. Catalytic dewaxing unit can improve the low temperature fluidity of diesel and produce diesel with high quality and low freezing. Experimental results and previous research results for 5 samples of North Sea oil and 3 samples of normal mixtures of alkanes and two samples of two-component mixtures have been analyzed. A multi-solid model has been proposed to investigate wax behavior and the Peng-Robinson equation of state for equilibrium calculations of liquid and solid phases and the model results have been compared with the experimental results. To improve the prediction results of the multi-solid model, the compressed oil component has been expanded and then grouped and divided into paraffinic, naphthenic and aromatic. After determining the behavior of wax in the studied oil, the catalytic dewaxing unit was modeled in aspen hysys software. The reactor of catalytic dewaxing unit is an important for converting paraffins into isoparaffins. Defining the individual reactions of the components is a difficult and time-consuming process. Therefore, in this research, each group of oil components has been divided into a pseudo-component, and a reaction is defined for each pseudo-component. To measure the weight of precipitated wax and the cloud point of the produced diesel fuel, aspen hysys and matlab software are connected and the amount of wax and the cloud point of the diesel fuel have been calculated. Finally, the optimal ranges for temperature, pressure, feed and hydrogen rate were determined by the Latin cube sampling method, and at these optimal points, wax weight and cloud temperature of diesel fuel were calculated using a multi-solid model. The cloud point calculated by the multi-solid model had a value of 0.134 for the input feed and 5.28% error for the produced diesel. At the optimal temperatures of 372.92, 492.25, and 522 K and pressure 1465.8, 1620, 1311.5 kPa, the cloud point value was 237.8, 238.1, and 238.13, respectively. The amount of precipitated wax at the temperature of 522 K was 3%, which shows a 70% efficiency of the process at this temperature compared with the initial amount of 10%.
