Expert opinion

A Unique Way to Optimize the Operation of Heat Exchangers


     Present-day production is a complex process of turning raw materials into finished products that meet requirements of society. One of the highest relevance priority development fields of the Bukhara Oil Refinery is the improvement of technological processes for the production of high-quality petroleum products.
     At the Bukhara Oil Refinery, a catalytic reforming unit is operated for the production of the high-octane number component of motor gasoline. A key role in the efficient management of the technological process of the plant is played by continuously circulating hydrogen-containing gas (VSG). The raw material of the process is heavy naphtha. When it arrives at the plant, it is mixed with Hydrogen Bearing Gas and heated by the resulting heat of the mixture of Hydrogen Bearing Gas and riformate (high-octane product) in two unique heat exchangers. Heat exchangers are vertical shell and tube devices known as the «Texas Tower» of positions 21E-01 A and B, manufactured by DELAUNAY ET FILS (France).
     As a result of 20 years of continuous operation of these devices and natural processes, the heat exchangers were blocked in 2017, which led to a decrease in their throughput. Therefore, one of the main technological parameters was violated, namely, the circulation of ratio of Hydrogen Bearing Gas to raw materials, which adversely impacted the quality and volumes of the production of reformate.
     If in 2003, with an average load of 79.3 m3/h, the consumption of Hydrogen Bearing Gas was averaged 49 thousand nm3/h, then in 2015, with overall load of 78 m3/h, the Hydrogen Bearing Gas consumption was averaged 24 thousand nm3/h. By 2017, with constant loading this figure continued to decline and reached a level of 16 thousand nm3/h. As a result, in order to maintain the circulation of the Hydrogen Bearing Gas at the acceptable minimum levels, it was necessary to reduce the unit utilization rate, as well as to reduce the production of the reformate and, hence, the amount of gasoline. Moreover, due to the reduced capacity of heat exchangers, the cost of heating raw materials has increased significantly. Therefore, in 2003, the consumption of fuel gas supplied to the 21F01 heater was 2 thousand nm3/h, whereby in 2018 this figure was already 3 thousand nm3/h.
     It should be noted that with a further reduction in the consumption of Hydrogen Bearing Gas, due to the low capacity of the heat exchangers 21E01 A/B, the risk of blocking the compressor 21KM01 increases, which can lead to a complete stop of the catalytic reforming unit and then the entire plant as a whole.
     Specialists of the Bukhara Oil Refinery took actions to eliminate this problem three times. Thus, in 2012 and 2015, heat exchangers were washed with a riformate for 34 and 24 hours, accordingly. Moreover, in 2018, during the overhaul of technological installations in the period from April 25 to May 15, 2018, flushing of these heat exchangers with xylene, toluene was conducted. However, this procedure did not give the expected effect. The consumption indicator of Hydrogen Bearing Gas remained unchanged.
     After studying the global experience, two methods of solution of the problem were identified:
     Method 1: Purchase of new heat exchangers. Work was carried out to find potential suppliers. In consequence, commercial offers for the supply of heat exchangers in the amount of 2 units 21E01 A/B were received: from Entrepose Pt Istana Karang Laut (Indonesia) in the amount of 7,922,000 euros, delivery time – about 8 months and from Rominserv (Romania) in the amount of 1,691,285 US dollars, delivery time – 8-10 months
Chief Mechanic of Bukhara Oil Refinery
You can read the whole articles in the printed version of the magazine.


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