Thermodynamic analysis of polygeneration systems based on catalytic hydropyrolysis for the production of bio-oil and fuels

Abstract

Novel polygeneration concepts based on catalytic hydropyrolysis and hydrodeoxygenation are presented and compared via process simulation and thermodynamic analysis. These systems process and convert biomass into high-quality bio-oil and fuels such as synthetic natural gas (SNG), molecular hydrogen (H 2) and methanol (MeOH). Twelve system layouts were evaluated and compared with regards to their energy demands and performances. Detailed thermodynamic models were developed, considering the different technological alternatives for the valorisation of bio-char, removal of carbon dioxide, fuel upgrading and water electrolysis, as well as the opportunities for energy integration. The results show that the standard system, which produces only bio-oil, reaches an energy efficiency of 61 % (LHV). This value can be increased by 7 to 28 %-points when co-producing SNG, 10 to 21 %-points when producing H 2 , and 10 to 19 %-points when producing MeOH. The highest values are achieved by co-production of SNG as light hydrocarbons are produced in the hydropyrolysis, and limited processing is therefore required to reach the desired product quality. High system efficiencies are possible mainly because of the high efficiency of the core hydropyrolysis process. Carbon conversion efficiencies are highest when generating SNG or MeOH and reach a maximum when electrolysis and char gasification are implemented (98 % and 95 %). The performance of these polygeneration systems is strongly impacted by the type of CO 2-separation process and electrolyser-these processes have a strong influence on the power and heating demands, as well as on the potential energy savings and waste heat valorisation.

The Influence of Active Phase Loading on the Hydrodeoxygenation (HDO) of Ethylene Glycol over Promoted MoS2/MgAl2O4 Catalysts

“…Excessive cracking leading to only gaseous products was observed during the first ~20 h on stream by Dayton et al [44] who performed catalytic hydropyrolysis of woody biomass using a pre-reduced commercial hydrotreating catalyst at 375 °C and 3 bar H2. Some cracking will, however, most likely occur during pyrolysis and potentially also during HDO, so it is important to consider how to utilize these by-products, for example through water gas shift and steam reforming to regain H2 for the reaction, or by subsequent production of SNG as a valuable by-product by methanation [3].…”

“…Catalytic hydropyrolysis is an efficient process for the direct production of diesel and gasoline type fuels from solid lignocellulosic biomass such as wood and agricultural residues [1][2][3][4][5]. Such fuels are necessary to reach the goal of becoming independent of fossil fuels, especially in the heavy duty and aviation sector, which are not immediately moving towards electrification.…”

Techno-economic analysis of polygeneration systems based on catalytic hydropyrolysis for the production of bio-oil and fuels

“…The present section builds on models developed in a previous paper by the authors [20]: the process and thermodynamic performances (inputs, outputs, efficiencies) of each type of plant are given in Appendix A.…”

“…The layout of the biorefineries investigated in this paper is presented in a previous study by the authors [20], but a short description is given for ease of reading. The main processes, common to all plant designs, are the feedstock preparation, the hydropyrolysis and hydrodeoxygenation, and the gas-liquids separation.…”

“…The models developed to compare the polygeneration concepts were developed and presented in Nguyen and Clausen [20]. The aim was to compute mass and energy balances for further component sizing and economic evaluations.…”