Optimering av bränngasförbrukningen i SynSat-anläggningen på Preem Raffinaderi, Göteborg
Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Publicerad
2003
Författare
Ohlsson, Sofia
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Preem Refinery consumes large amounts of energy in their plants. Due to the fact that the fluids cause fouling in units, the heat transfer in heat exchangers and heaters are deteriorated. This eventually results in a high consumption of fuel. The energy use in the heater is also affected by the amount of excess air, incoming flows and temperatures. The work is based on the SynSat plant. The system that is studied consists of four heat exchangers placed in series followed by a gas-fired heater. The task of the system is to deliver gas oil to the desulphurising reactor at an adequate temperature. The modelling was performed in Matlab and the calculations were carried out in three steps: - Calculation of the instantaneous fouling - Calculation of the temperature profile in the heat exchanger train at existing operating conditions. - Optimisation of the fuel consumption. The model is based on detailed information from the process regarding temperatures and flows as well as the unit geometries. Two different operating conditions have been used as references. 2002-03-08 when the units showed a substantial amount of fouling and also 2003-08-02 when both the heat exchangers and the heater were recently cleaned. The presence of fouling mainly affects the fuel consumption by giving a lower temperature from the heat exchangers. Therefore a larger temperature increase must occur in the heater to achieve the specified reactor temperature. Fouling deteriorates the heat transfer in the heater and increases the fuel consumption further. The result of this work is a tool that can be used to investigate and optimise the fuel efficiency when producing MK1 in the SynSat plant. Since the modelling is performed in Matlab it is too complicated to implement in the daily work at Preem Refinery. The advantages are that it can be modified to corporate with other product qualities and also to be developed for application on other plants. Through statistical methods the model may be simplified and transferred to a user-friendlier interface, e.g. Excel. When producing MK1 it is the custom to bypass the heat exchangers 15E15, 15E2 and 15E3 by 70% and to maximize the use of 15E4. The calculations show that maximum use of all heat exchangers results in the minimum use of fuel. However, this solution only reduces the consumption with approximately 1,5 %. For the case with fouling in the system the fuel consumption can de reduced. This is achieved by using the heat exchangers as much as possible. Compared to the fouled reference case the consumption may be reduced as much as 13 %. The results may seem somewhat trivial, which is caused by the fact that the temperature limitations haven't led to any constraints in the two cases. The results would probably have been very different if MK3 was studied instead of MK1, since MK3 usually implies larger flows and higher temperature demands.
Beskrivning
Ämne/nyckelord
Kemiteknik , Chemical Engineering