• Energy Research

Aqueous phase recirculation increased the bio-crude yield and energy recovery along with promoting the production of N-heterocyclic compounds that lead to harsher required hydrotreating conditions.

Hydrothermal liquefaction (HTL) is a promising technology for converting organic-rich waste biomass such as swine manure (SM) and sewage sludge (SS) into energy-dense bio-crude. Until now, one of the major challenges associated with HTL is the pumpability of high dry-matter containing fibrous feedstocks for continuous processing. In this context, this batch scale study presents a suitable approach for enhancing the pumpability of the fibrous material, specifically SM, by co-processing with SS. Obtained results showed that SM was not pumpable itself due to its fibrous nature, but became pumpable by the addition of SS at overall 25 % dry matter content. It was highlighted that the sample mixture containing ~80 % of the SM was smoothly pumped with 20 % SS. Subsequently, HTL experiments were carried out on samples mixed under the ratios SM:SS (100:0, 0:100, 50:50, 80:20, and 20:80). The highest bio-crude yield (42.38 %) via maximum synergistic effect was obtained from the sample SM/SS (50:50) at ratio 1:1 with the best HHV of 36 MJ/kg. Almost 60–70 % mass of all bio-crudes contained volatiles at 350 °C. ICP-AES measurements revealed that the majority of the inorganic elements were concentrated into the solid phase, while 40–50 % of the potassium and sodium were transferred to the aqueous phase. In conclusion, using SS as a co-substrate with SM not only enhances the pumpability of SM, but its co-liquefaction has demonstrated beneficial synergistic effects on improving the energy recovery of the bio-crude.

Hydrothermal liquefaction (HTL) bio-crude is known as a potential alternative to conventional fossil fuels in the existing infrastructure. Although HTL has enormous potential as a process for renewable fuel production, developing economically viable HTL-based value-chains has encountered extensive challenges owing to the contaminants and the complex matrix it possesses. Therefore, devising efficient downstream processing and blending strategies is of high importance. This study evaluates different bio-crude refining scenarios; namely 1) pre-stabilization using partial hydrotreating, 2) fractionation through vacuum distillation and 3) the integration of the former processes, in producing a compliant HTL-derived road diesel blendstock. The combination of the distillation fractions is optimized through a multi-objective optimization method minimizing the deviation from the road diesel standard specifications. The optimized blend fuels are combusted in an optical accessible compression-ignited chamber (OACIC) to assess the exhaust emissions. Partial hydrotreating successfully improves the distillation recovery from 22.7 wt% (raw bio-crude) to 55.6 wt% along with a significant improvement in the physicochemical properties. The hydrotreated bio-crude distillate mixture is an adequate diesel blendstock that complies with the standard specification by at least 5 wt% contribution to the finished fuel. The results also show that with a slight improvement in the desulphurization of bio-crude, the bio-blendstock share can increase up to 10 wt%. With the comparable GHG emission profile to the reference diesel, the hydrotreated bio-crude distillate mixture heralds a promising green blendstock that can significantly contribute to meeting the current road transport diesel fuel demand.

This study investigates the integration of a biomass mechanical pretreatment technology and hydrothermal liquefaction for the valorization of biopulp; the organic fraction of municipal solid waste. A preliminary screening of the hydrothermal liquefaction conditions was carried out to investigate the impact of temperature (350 and 400 °C) and the presence of alkali catalyst (K2CO3) during the hydrothermal conversion of biopulp. Sub-critical conditions and the presence of the catalyst were noticed to have a significant positive impact on the energy recovery of the bio-crude. Therefore, the 350 °C-catalytic experiment was deemed as the reference test. To increase the energy recovery in the biocrude, recirculation of the aqueous phase was further investigated. In this case, the obtained aqueous phase was fractionated into a distillate and a concentrate phase. By recirculating the concentrate phase in four consecutive cycles, the bio-crude production yield and energy recovery increased to 49.3% and 84.3%, respectively. Additionally, evaporation of the aqueous phase revealed to have a positive impact on the removal of nitrous compounds (mostly in the form of ammonia) during the fractionation process. In conclusion, the recirculation-assisted HTL of biopulp is an energy efficient process to valorize the organic matter of municipal solid waste.

This study involves the investigation of municipal solid waste (MSW) based biofuel in order to demonstrate its utilization as a diesel blendstock in a compression ignition (CI) engine. The biofuel was produced from the Hydrothermal Liquefaction (HTL) process. The tested biofuels represented both distilled (known as nonupgraded HTL biofuel) and hydrotreated (known as upgraded HTL biofuel) fuels, obtained from raw bio-crude. The effects of the HTL biofuel and diesel blending on the combustion and emission characteristics were investigated. A comparative study of nonupgraded and upgraded HTL biofuel in terms of combustion and emissions was conducted. The upgraded HTL biofuel was blended with reference diesel (RD) by 5%, 10%, and 40% by weight, respectively, and the nonupgraded HTL biofuel was blended with RD by 10% by weight. The experiments were conducted in an optically accessible compression ignition chamber (OACIC) with engine-like thermodynamic conditions. The parameters were recorded at a constant speed and at fixed thermodynamic conditions. The heat release rate (HRR), in-cylinder pressure, ignition delay (ID), flame lift-off length (FLOL), and in-flame soot were measured. The PM, CO, NOx, and CO2 were also recorded. In summary, the HTL blends exhibited a close resemblance to the reference diesel across a range of combustion parameters and regulated emissions. Furthermore, the upgraded HTL blends outperformed the nonupgraded blend in terms of both combustion characteristics and emissions.

In this study, the potential of the pyrolysis method to overcome the negative effects of Azolla-filiculoides in infected areas was thoroughly investigated. Non-catalytic pyrolysis experiments were conducted at a temperature range of 400-700 °C. The highest possible bio-oil yield (35 wt%) was attained at 500 °C. To achieve the best chemical composition of bio-oil and higher amount of synthesis gas the catalytic pyrolysis were conducted in a dual-bed quartz reactor at the optimum temperature (500 °C). Although, all three catalysts (pyro-char, modified pyro-char (MPC), and Mg-Ni-Mo/MPC) showed almost an impressive performance in promotion of the common reactions, Mg-Ni-Mo/MPC catalyst have illustrated the stunning results by increasing the percentage of furan compounds from 5.25% to 33.07%, and decreasing the acid compounds from 25.56% to 9.09%. Using GC-MS and GC-FID liquid and gaseous products were fully analyzed. The carbon-based catalysts were also evaluated via FTIR, FESEM, EDX, and BET analyses.

This study focuses on the valorization of the organic fraction of municipal solid waste (biopulp) by hydrothermal liquefaction. Thereby, homogeneous alkali catalysts (KOH, NaOH, K2CO3, and Na2CO3) and a residual aqueous phase recirculation methodology were mutually employed to enhance the bio-crude yield and energy efficiency of a sub-critical hydrothermal conversion (350 °C, 15–20 Mpa, 15 min). Interestingly, single recirculation of the concentrated aqueous phase positively increased the bio-crude yield in all cases, while the higher heating value (HHV) of the bio-crudes slightly dropped. Compared to the non-catalytic experiment, K2CO3 and Na2CO3 effectively increased the bio-crude yield by 14 and 7.3%, respectively. However, KOH and NaOH showed a negative variation in the bio-crude yield. The highest bio-crude yield (37.5 wt.%) and energy recovery (ER) (59.4%) were achieved when K2CO3 and concentrated aqueous phase recirculation were simultaneously applied to the process. The inorganics distribution results obtained by ICP reveal the tendency of the alkali elements to settle into the aqueous phase, which, if recovered, can potentially boost the circularity of the HTL process. Therefore, wise selection of the alkali catalyst along with aqueous phase recirculation assists hydrothermal liquefaction in green biofuel production and environmentally friendly valorization of biopulp.