Economic benefits of dual stripper and dual fractionator flow scheme vs a single stripper 1-8
Parameters
Unit
Conventional single stripper flow scheme (base case)
Dual stripper and dual fractionator flow scheme
Fractionator feed heater duty
MMKcal/hr tonne/hr tonne/hr $MM/year
41.1 Base Base Base Base Base Base Base Base
17.7
MP steam generation LP steam consumption
(12.4)
(18) (8.5)
Utility cost
Estimated erected cost (EEC) for additional equipment NPV from process improvements
$MM $MM
+12.5 + 45.5
CO₂ emission (Scope 1 & 2)
tonne/year $MM/year
(~65,000) (1)
CO₂ credit
+ 3.3 + 68
NPV including CO₂ credit
$MM
Notes: 1. 327 m3/hr (49,362 BPSD) two-stage HCU with conversion of 99.5 vol%. 2. Fuel consumption is based on 90% heater efficiency. 3. CO₂ reduction credit $50/tonne. 4. Onstream hours: 8,400 hours per year. 5. NPV is for 15 years at 10% discount rate basis. 6. Simple payback period 18 months and with CO₂ credit payback period will further reduce to 13 months. 7. Utility price basis: • Fuel gas: $35.7/MMKcal • MP steam: $13.3/tonne • LP steam: $11.9/tonne 8. Scope 1 & 2 CO₂ emission basis: • 0.262 tonne of CO₂/MMKcal of fuel gas • 0.208 tonne of CO₂/tonne of MP steam • 0.196 tonne of CO₂/tonne of LP steam
Table 3
Economic and emission minimisation goals The dual stripper and dual stripper with dual fractiona - tor process flow schemes provide an efficient means to separate the reactor effluent from the reactor section to high-quality products from an HCU while still meeting the stringent requirements of diesel product specifications. The dual stripper and dual fractionator flow scheme reduces the product fractionator feed heater duty by more than 50% compared with the conventional single stripper design. Due to the reduction in the product fractionator feed heater duty, CO 2 emissions from the HCU will also be reduced, as noted in the examples presented in this discussion. The dual stripper and dual fractionator flow scheme are commercially proven solutions that provide improved profit - ability while helping refiners achieve their energy efficiency improvement goals across their asset base. These are solu - tions that can be applied to new and existing HCUs. References 1 Wood Mackenzie, Refinery emissions: Implications of Carbon Tax and Mitigation Options, Nov 2021. 2 Baars F, Oruganti S, Kalia P, Oil refinery/petrochemical integration in a CO₂-constrained world; Part 2, Hydrocarbon Processing, Aug 2021. 3 www.epa.gov/climateleadership/ scope-1-and-scope-2-inventory-guidance Kiran Ladkat is Principal Hydroprocessing Process Specialist at Honeywell UOP, specialising in design of hydrotreating and HCUs. He has 25 years’ experience in the refinery and petrochemical industry and been granted 14 US patents. He holds a bachelor’s degree in chemical engineering from Pune University. Email: kiran.ladkat@Honeywell.com Jan De Ren is Global Sr. Offering Manager for UOP’s Fluid Catalytic Cracking, Hydroprocessing, and Heavy Oil technologies in Honeywell UOP’s office in Des Plaines, USA. He holds an MSc in applied chemi - cal engineering from the University of Antwerp, Belgium and has nine granted US patents. Email: jan.deren@Honeywell.com Kiran Kashibhatla is Global Project Development Manager – UPT Hydroprocessing and Heavy Oil technologies in Honeywell UOP’s office in Bracknell, UK. He has 16 years’ experience in refining and petrochem - icals and holds a master’s in chemical engineering from Indian Institute of Technology, Roorkee. Email: kiran.kashibhatla@honeywell.com
the hot stripper, it was proposed to use two fractionators, namely a light fractionator, which will receive the feed from the cold stripper and a heavy fractionator, which will receive the feed mainly from the hot stripper. Figure 7 presents the dual stripper and dual fractiona- tor flow scheme. The cold and hot stripper bottoms liquid streams will feed separate fractionator columns: a light fractionator and a heavy fractionator, respectively. The cold stripper bottoms liquid is preheated with available process heat in the fractionation section to reach a certain vaporisa- tion and then fed directly to the light fractionator. The light fractionator is steam stripped, and its objective is to separate the kerosene and naphtha portions from the diesel and unconverted oil products, which is routed to the heavy fractionator and fed just below the diesel product draw stage as a combined bottoms product. The fractionator feed heater provides heat only to the bottoms liquid from the hot stripper. The heavy fractionator operates at a partial vacuum and will perform the required separation between the diesel and unconverted oil streams. Because the heavy fractionator operates at a partial vac- uum, the required heavy fractionator feed heater outlet tem - perature is lower than what would otherwise be required for an atmospheric column, thereby reducing the required fractionator heater duty and subsequent stack emissions. Improved relative volatilities between diesel and uncon - verted oil at the lower operating pressure in the heavy frac- tionator reduce the required heater duty by more than 50%, compared with the conventional single stripper design. Table 3 provides a summary of the utility consumption, economic, and CO₂ emission benefits with a dual stripper and dual frac - tionator flow scheme as compared to a conventional single stripper flow scheme. As summarised in Table 3, the reduction in total fuel consumption for this 327 m3/hr (49,362 BPSD) two-stage HCU improves the facility’s NPV by $45.5 million. If CO₂ avoidance is at $50 per tonne, the NPV boost attributa - ble to the dual stripper and dual fractionator flow scheme approaches $68 million.
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PTQ Q3 2023
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