Design, Modelling, and Experimental Validation of a Scalable Continuous-Flow Hydrothermal Liquefaction Pilot Plant

Abstract

In this study, the design and practical implementation of a novel, scalable plug-flow pilot plant for hydrothermal liquefaction of organic feedstock is presented. The overall discussion comprises the system’s design, process modelling, and simulation, as well as results for an experimental validation of the proposed design with a focus on fluid dynamics and heat transfer. The design criteria take into account the scalability of the plug-flow processing system, optimized non-isothermal flow conditions of highly viscous liquids in a tubular system at harsh process conditions, specifically high pressure and medium temperatures, and overall maintenance suitability. A novel forced flow oscillation system as well as unique heat exchange design to reduce the energy consumption during system operation, maximize local flow mixing, and minimize plugging are proposed and experimentally tested. To achieve a better understanding and optimization of Hydrothermal Liquefaction (HTL) (and other) processing systems, a mathematical model of heat transfer coupled with non-isothermal fluid flow was also developed and implemented.

Synergies during hydrothermal liquefaction of cow manure and wheat straw

“…The slurries were fed in three different campaigns to the continuous HTL pilot plant (Aarhus University, Foulum, Denmark). The pilot plant detailed design [34] and operation [35] is described elsewhere. In short, the pilot plant is composed of: one main positive displacement high pressure pump; one integrated counter-current heat exchanger section that uses the product stream for heating the incoming slurry; one trim heater section to assure set point temperature is reached; one reactor section that provides the necessary reaction residence time for the slurry and; one take-off system composed of pistons and valves.…”

Feasibility of Utilizing Wastewaters for Large-Scale Microalgal Cultivation and Biofuel Productions Using Hydrothermal Liquefaction Technique: A Comprehensive Review

“…The above discussions regarding the pros and cons of HTL process evoks that there is a need of design commercial scale hydrothermal equipment which can process a large-scale microalgal biomass in a very short period to bio-oil. Recently, Johannsen et al (2021) have nicely designed a large-scale HTL batch reactor for processing of biomass. The core part of the HTL plant is equipped with 58 type-K thermocouples.…”

“…The main unit is also outfitted with a trim heater, reactor, cooler, thermocouples, and heat exchangers. This large-scale HTL plant made up with the polycarbonate coffer and inner protective steel and it has the active suction from all areas (Johannsen et al, 2021). This kind of experimentations are highly needed for pilot plant set up with HTL technique with which the large-scale algal slurry can be processed to bio-oil in a timely manner.…”

Comparative investigation on the value-added products obtained from continuous and batch hydrothermal liquefaction of sewage sludge

“…Pacific Northwest National Laboratory has reported 37 wt% yields of biocrude achieved from 12 wt% dry matter slurry in a continuously stirred-stank HTL system (Marrone et al, 2018). The novel pilot-scale continuous HTL plant incorporated an oscillating flow technology, developed by Aarhus University in Denmark, and has processed algae and SS with a capacity of up to 100 L/h (Anastasakis et al, 2018;Johannsen et al, 2021). Average yields of 25 wt% biocrude was obtained by HTL of 4 wt% dry primary sludge slurry at 350 °C with a 5 h retention time.…”