(100e) Hydrodeoxygenation of Karanja Oil for the Production of Green Diesel: Process Design with Heat Integration and Economic Analysis

Hydrodeoxygenation of karanja oil for the production of Green Diesel:Process design with heat integration and economic analysis

Current energy scenario motivates the use of renewable energy to address the limitations of fossil fuels. Biomass is the best renewable carbon source for all forms of energy including transportation fuels. The transportation fuels are the leading energy-consuming sector with ~27% share of energy consumption globally. The inedible vegetable oils such as karanja oil are the promising biomass for the transportation fuels due to long hydrocarbon chain with lower oxygen content. Hydrodeoxygenation (HDO) is the most promising route for removal of oxygen from vegetable oil and production of diesel range hydrocarbons known as green diesel. The green diesel has high energy density with high cetane number and is suitable for direct use in existing combustion engines [1-2]. The HDO of vegetable oil can be envisaged through two different routes: (i) direct HDO and (ii) two-step HDO (hydrolysis of vegetable oil followed by HDO of fatty acid).

       In the present work, the conceptual processes were designed using karanja oil as feedstock. The heat integration was done to minimize the energy consumption. The minimum hot and cold utility requirements and maximum heat recovery within the process were calculated using grand composite curve as shown in Fig. 1. The heat exchange network was further designed based on the principle of pinch analysis. The economics of the heat-integrated processes were then evaluated. The capital investment was practically identical for both the processes. The 0.12 MMT/annum karanja oil was obtained as the optimum plant capacity. The production cost of green diesel was estimated as 0.812 $/kg and 0.773$/kg for direct and two-step HDO respectively. The feedstock was found to contribute around 75-80% of the production cost with only about 1.8-4.1% contribution from the utilities. The co-product credit (about 15%) was significant in the two-step process. Based on discounted cash flow analysis, the minimum selling price of green diesel was found to be 1.142 $/kg and 1.164 $/kg for 8.5% rate of return for direct and two-step HDO. The green diesel is thus economically competitive with the current retail price of the petrodiesel.

References:

• 1.Kalnes TN, Marker T, Shonnard DR, Koers KP. Green diesel production by hydrorefining renewable feedstocks. Biofuels Technol 2008:7–11.
• 2.Knothe G. Biodiesel and renewable diesel: A comparison. Prog Energy Combust Sci 2010;36:364–73. doi:10.1016/j.pecs.2009.11.004.

Fig. 1. Grand composite curve for direct and two-step HDO.