| dc.description.abstract | This report focuses on the production of hydrocarbons in a biomass to liquid (BtL) process with integration of hydrogen production. The hydrogen will be produced from high temperature electrolysis of steam utilizing excess heat in the plant. This represents a novelty which will increase the carbon efficiency of the plant, and lower the production cost.
The design and evaluation of the plant have been done by simulations in Aspen Hysys V9.
The conventional method of producing hydrocarbons in a BtL plant uses steam to adjust the syngas ratio by converting some of the CO into \ch{CO2} and hydrogen. In this case, the \ch{CO2} emissions from the plant are larger and the carbon efficiency is lower, typically 30-40\%.
However, the hydrogen enhanced BtL plant in this report has shown a carbon efficiency of 97\%. This is because \ch{CO2} is not removed from the syngas due to the low concentration obtained when using the produced hydrogen to convert \ch{CO2} into CO and simultaneously adjusting the syngas ratio. The only carbon emission is the purge, which nonetheless is required to remove the inerts to avoid accumulation in the process.
By heat integrating the whole process, the energy efficiency is found to be 70.4\%.
The high temperature electrolysis for production of hydrogen and oxygen from steam currently have a high electrical energy consumption and investment cost. It is expected that the electricity consumption and equipment cost will be significantly reduced between 2020 and 2050. Currently, the HTE technology is only demonstrated in pilot scale for hydrogen production.
From the economic evaluation of the profitability of the project it is estimated that the production cost for one liter of products is 5.32 NOK. This is significantly lower than the 7.04 NOK/L estimated for the conventional steam BtL plants. The plant will also be able to tolerate the higher discounted cash-flow rate of return of 15\% compared to 5\% for the steam BtL plant.
Compared to a conventional steam BtL plant, the hydrogen enhanced plant will have higher investment and operating costs, but this will be compensated by the increased production of hydrocarbons. | |
