چكيده به لاتين
Over the last decades, as global energy demand and crude oil prices rise, alternative routes to produce hydrocarbons and petrochemicals are becoming more economically attractive. Natural gas is rapidly becoming an important source of worldwide energy. Gas to liquid (GTL) is one of the main processes that liquefied natural gas through chemical conversion. The key concept of a GTL process is the chemical conversion of natural gas into longer chain hydrocarbons that can be upgraded and separated into useful hydrocarbons such as naphtha, diesel, kerosene, etc.
The approach of this work is to introduce another systematic method which could automatically select the optimal configuration between alternatives much faster than previous methods. Existing methods mostly connects common process simulator and computing programs, consuming long processing times to achieve the optimal configuration. Due to this work and the set targets, a generalized disjunctive programming formulation is presented which includes 3 mains (Generate search space by the separation matrix, Simulate and Optimize).
In this work, the possible structures such as simple and complex configurations that separate the four LTFT GTL main products, are generated by the separation matrix.
Peng Robinson equation of state is used for thermodynamic properties and equilibrium prediction package. The simulation of each configuration is carried out in two steps. Initially, shortcut simulations are carried out according to FUG algorithm, to find the preliminary data (minimum reflux, minimum stages, and location of feed stage) needed as the initial estimate for the next step, rigorous simulations, according to inside-out algorithm.
A wide variety of effective design variables in the distillation process such as the number of equilibrium stages, feed stage location, columns’ pressure, side streams and their locations and flow rates in a complex configuration, are optimized through minimizing TAC for each configuration.
Optimization results show that direct sequence has the best overall performance with the lowest total annual cost ($ 10.59 million per year) and the lowest exergy loss compared to other sequences. The research results show the superiority of direct sequence while the indirect sequence is repetitive in LTFT GTL plants licenses. However, the indirect sequence increases the TAC about 27% compared to direct sequence. The results show that the LTFT GTL separation process could be an attractive research platform.
