refining india 2022
the overhead condenser brings the out- let pressure closer to the inlet pressure, which means the outlet pressure is main- tained high. Consequently, the vapour fraction at the outlet is reduced while the liquid fraction is increased, which means more valuable molecules are recovered. So, in the end, the light end product flow (or reflux flow) is maximised while the off- gas flow is minimised. Alfa Laval provides overhead condenser optimisation solutions with Compabloc heat exchangers in various processes ranging from ADU overhead condensers to much simpler stripper overhead con- densers. Upgrading to higher grade mate- rial in Compabloc does not necessarily result in a huge cost increase thanks to the much lighter weight of heat transfer plates because Compabloc usually needs much less heat transfer area and the plate itself is thinner than a tube. Recover and reuse low-grade energy Several streams cooled with cooling water or ambient air waste low-grade
down coolers, and even condensers use a considerable amount of cooling water and add a burden to the cooling water supply system. However, this can be completely changed if heat exchangers with signif- icant temperature cross can be used. This can generate hot water or preheat boiler feed water instead of returning warm water to the water-cooling sys- tem. Recovering waste heat in this way could change those heat exchangers from cost generators to profit generators (see Figure 4 ). For decades, many refiners have selected Alfa Laval solutions for waste heat recovery from low-grade energy sources around the fractionator column. For example, air coolers or shell and tube condensers have been changed to com- pact condensers with temperature cross to recover energy from vapour to hot water. Similarly, simple shell and tube coolers with cooling water have been changed to coolers with temperature cross and a tight temperature approach to recover energy from the bottom prod-
uct or rundown stream and generate hot water. Recovered energy is reused in various applications, such as boiler feed water preheating, freshwater generation, waste- water evaporation, and district heating, which brings significant Opex saving at very small Capex. Conclusion While energy saving, emission control, and molecule management are gaining focus, optimising the performance of the fractionator beyond the limit of conven- tional technology is fully in line with such a trend. This will save energy by optimis- ing the feed bottoms exchanger and the overhead condenser and recovering val- uable molecules through the overhead condenser. Energy can be recovered by optimising coolers that use cool- ing water, which will also reduce cooling water usage. Of course, alternatively, the energy saved can be used for increasing capacity in the plant instead of reducing energy costs.
P min
WHR
25˚C
min
O gas
dP min 30˚C
Fractionator
max
Light end
Re ex drum
T max
WHR
R/D max
P min
Feed
Q min
WHR
Q max
Bottom product
Figure 4 Recover and reuse low-grade energy from streams in the fractionator
energy because when using conventional shell and tube technology it was easier than the more expensive option of recov- ering the energy. Product coolers, run-
DWC technology for improved separation and reduced CO 2 emissions
Srinivasulu Kaalva, Chanchal Samanta, Chiranjeevi Thota, Bharat L Newalkar and Ravikumar Voolapalli Bharat Petroleum Corporation Ltd
The two most important challenges today’s refinery and petrochemical indus- tries are facing from a sustainability point of view are reducing carbon footprints from operation while maintaining a prof- itability margin by improving the yield of value-added products. Improved separation efficiency plays a key role in increasing product yields with minimum energy consumption, thereby reducing CO₂ emissions. The divided wall column (DWC) concept, which combines the operation of two conventional columns in one shell, is an advanced separation tech- nique that helps improve energy efficiency in the range of 10-30% while reducing cap- ital expenditure and space requirements. DWC technology is a very promising sep- aration system. In the last two decades, it has found applications in different indus- tries, especially specialty chemicals, petro- chemicals, and refineries. Global specialty chemicals producers are actively imple- menting this technology in their separation applications. To capture the opportunities in these areas, BPCL has developed its own DWC technology and implemented it successfully in Kochi Refinery, one of the flagship refineries of Bharat Petroleum Corporation Limited (BPCL). The key features of the technology are: • BHARAT DWC (B-DWC) is a novel and patented technology developed by BPCL for naphtha separation based on the DWC concept • Based on B-DWC technology, a DWC column was configured for naphtha sepa- ration into four different streams
control strategies in China, India is poised to become one of the major specialty chemicals manufacturers in the world. To meet the future demand for chemicals in India, it is important to use energy-effi- cient technologies to reduce the cost of production, as well as refinery carbon foot- prints. In view of this, DWC technology can find a place in the following separation applications: • Solvent recovery • Extractive distillation
Liquid split
A
Re ux
Vertical wall creates a feed and draw-o section
A,B,C
Boiling point A<C<B
C
Main column
• API purification • Gas separation • Refinery separation applications
Vapour split
B
There is tremendous scope for convert- ing or designing new DWC columns for dif- ferent types of applications in India. Based on preliminary analysis, approximately 100 separation columns in Indian refiner- ies can be converted to DWC. In addition, due to the competitive price advantage in India compared to other developed nations presently licensing this technology, India can become a global technology provider and earn foreign exchange, as well as provide employment for Indian nationals across the globe. BPCL has signed an agreement with Engineers India Limited (EIL) to license this technology using the trade name ‘BharatEng-DWC Technology’. BPCL-EIL is advancing to jointly provide end-to-end technology, including process design, inter- nals supply, installation, and commissioning for both greenfield and retrofitting units.
Figure 1 Schematic of DWC concept (left) and photo of the naphtha splitter at Kochi Refinery with DWC technology (right)
commissioned on 11th March 2019, and high-quality separation was achieved Although the DWC concept is well known, very few global players are licens- ing the technology due to the design complexity and associated operational challenges. Typically, two conventional col- umns are required, or more energy (~30%) is needed to achieve separation similar to that obtained in B-DWC. BPCL was the first Indian company to successfully dem- onstrate DWC technology based on indig- enous know-how. B-DWC technology is a versatile and energy-efficient separation technology, and it can be applied to any separation sys- tem that separates three or four products. Due to changes in geopolitics and pollution
BPCL was the first Indian company to successfully demonstrate DWC technology
• B-DWC technology was implemented at Kochi Refinery by modifying an existing conventional three-cut column into a four- cut B-DWC • The modified column was successfully
Contact: dlcrdcsupport@bharatpetroleum.in
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