Renewable diesel
WHR
Hot water
O gas
WHR
Hot water
Green naphtha
Hot water
LP steam
WHR
WHR
WHR
Product fractionator
LP steam
DM water
SAF
DM water
Stripper bottoms
Figure 5 Improved product fractionator design using WPHEs to maximise waste heat recovery (WHR)
Conventional water-cooled shell-and-tube heat exchangers are designed to avoid a temperature cross so that the cooling water return temperature is the same as or lower than the outlet product or vapour/condensate temperature. As a result, the difference between the cooling water supply and return temperatures is sometimes less than 10°C. This means a large amount of cooling water needs to circulate between the HVO complex and the cooling water plant. When WPHEs are first used to maximise the WHR from process streams, the remaining
cooling duty is minimised. In addition, for the final trim cooling or condensing duty, the cooling water return temperature can be maximised in a single heat exchanger with a minimal flooded weight and plot space requirement, thereby reducing the amount of cooling water in circulation by up to 50% (see Figure 6 ). This will reduce the piping and pump cost of a new cooling water system (or minimise load on an existing system), as well as the energy consumption of the circulation pump. Summary and conclusions HVO processing has clearly made its way into
Renewable diesel
Hot water
O gas
T max
Hot water
Green naphtha
Hot water
m min .
LP steam
Cooling water
Product fractionator
LP steam
DM water
SAF
DM water
Stripper bottoms
Figure 6 Improved product fractionator design using WPHEs to minimise cooling water requirement
www.decarbonisationtechnology.com
42
Powered by FlippingBook