Pulsed high velocity process flow with hydrocyclone separation of inorganic solids in hydrothermal biomass conversion

Abstract

A system for thermochemical biomass conversion is dislcosed. The system comprises two or more pump systems each configured to pressurize biomass feedstock slurry and introduce it into an HTL process stream pressurized to at least 130 bar and also to depressurize HTL product and remove it from an HTL product stream pressurized to at least 130 bar, a heat exchanger system comprising separate tubes for feedstock input and product output configured to heat biomass feedstock slurry after it is introduced under pressure into the HTL process stream by counter- current exchange with the HTL product stream, an HTL reactor in fluid communication with and downstream from the heat exchanger system, and a control system configured to control each of the two or more pump systems so that the feedstock input flow it drives is pulsatile, wherein each of the two or more pump systems is configured to drive input of biomass feedstock and to remove HTL product stream from separate sets of input and output tubes within the heat exchanger that are dedicated to that pump system. A method for biomass conversion is also disclosed.

Description

[0001] Pulsed high velocity process flow with hydrocyclone separation of inorganic solids in hydrothermal biomass conversion. Field: The invention relates to hydrothermal liquefaction systems and methods generally and specifically to systems and methods which employ high velocity, pulsatile flow of the process stream and hydrocyclone solid separators employed under reactor conditions. Hydrothermal liquefaction (HTL) is a technique well known in the art for thermochemical biomass conversion. A subclass of solvent liquefaction where the solvent is water, HTL is advantageously applied to wet feedstocks. Aqueous biomass slurries comprising between 5 - 30 wt. % biomass dry matter are subject to thermal degradation at high temperatures (sub- or supercritical) and pressures. HTL has shown tremendous promise as a method for biomass conversion with exceptionally high total energy recovery in the product oil fraction. It has been demonstrated on small scale with good success using a diverse variety of different feedstocks (for review see Castello 2018). However, commercialization of the technology has proven difficult due to a number of technical challenges. We have previously presented solutions to several of these challenges: Our solution to the problems of pressurizing and loading an HTL reactor with viscous biomass slurries and of de-pressurizing and removing product oil are presented in WO2022 / 194332. In our system, a single pump both pressurizes the biomass feedstock stream and introduces it into the process stream and also depressurizes the product oil output stream so as to remove product oil. A single pump comprises a cylinder having an inlet end and an outlet end and having both a low pressure valve and a high pressure valve at both the inlet and the outlet end. Each cylinder comprises an inner hydraulic actuator segment which is separated from an inlet segment on the inlet end and from an outlet segment on the outlet end by a lower-pressure zone sealed by two or more gaskets and each further comprising an axially displaceable piston fitted with a piston ring which piston is adapted to move back and forth within the hydraulic actuator segment so as to alternately displace volume in the inlet segment when piston movement Is towards the inlet end and in the outlet segment when piston movement is towards the outlet end. The biomass feed stream is input through the low pressure valve on the inlet end of each cylinder while the product oil output is removed through the low pressure valve on the outlet end of each cylinder. By controlling the rate at which the piston moves through the hydraulic actuator segment, the feedstream loading / product output stroke and the feedstream pressurization and input / product depressurization and loading stroke can be of different duration. Our solution to the problem of heat exchanger cost and efficiency is presented in WO2021 / 024176. In our system, comparatively thin-walled conduits made of appropriate corrosion resistant, expensive alloy material such as Inconel 625 (™) are introduced into heat transfer members made of inexpensive carbon steel by expanded fit to provide excellent heat transfer efficiency as well as ease and economy of commercial production. In a preferred embodiment employed in the HYLIQ 5000 (™) modular HTL proto-type, six (6) conduits are mounted within a tubular heat transfer member that is in turn surrounded by an outer casing and insulation. This heat exchanger system supports an arrangement where three (3) separate pump cylinders are employed, each driving both biomass feed stream input and product oil output through two (2) conduits. Here we present additional solutions to the problem of heat exchanger fouling and also to the problem of corrosivity of product oil arising from inorganic compounds rich in alkalai metals, chlorides and sulfides. The underlying chemical reactions in HTL involve depolymerization of the biomass as well as partial deoxygenation of the resulting intermediates through dehydration, decarboxylation and decarbonylation reactions resulting in desirable production of crude bio oil. Concurrent undesirable char formation is an inevitable consequence of competing re-condensation and re-polymerisation reactions involving these same intermediates which reactions are prevalent at temperatures beneath 280oC (Chornet 1985, Elliot 2015, Mathanker 2021). For this reason, char formation exacerbates the problem of heat exchanger fouling during heating of biomass feed streams in HTL which are, in any case, notorious in their own right for settling and for viscous, non- Newtonian flow behaviour. The problem of heat exchanger fouling in HTL systems is so severe that leading researchers in the field at the US Department of Energy’s Pacific Northwest National Laboratory (PNNL) have recently proposed abandoning the use of heat exchangers altogether. They report in public presentations that they were unable to run their “traditional” heat-exchanger-centered pilot plant for more than 110 hours continuously without having to stop to correct a “plugging” event in the feed stream preheater and sometimes had to stop after only one hour continuous operation (Thorson 2023a; Thorson 2023b). They concluded that “commercial design” of HTL plants “should minimize use of heat exchangers” and proposed less efficient but less problematic methods for heating the biomass feed stream, such as the (FLASH-HTL) system Flashing for Low-fouling, Steam-based Heat recovery in Hydrothermal Liquefaction which is described in WO2024 / 076806. Fouling is a well known problem with heat exchangers, in general, even in the absence of the char formation phenomena which plague HTL. Empirical “fouling factors” for process fluids are routinely applied in heat exchanger design to ensure adequate capacity is installed when “fouling resistance” is accounted for. For HTL heat exchangers converting lignocellulosic biomass streams, Ghadge and coworkers (2022) report a typical range of empirical “fouling factors” of between 0.002 and 0.005 m2.h.C.KCal -1 (which corresponds to a negative heat transfer coefficient of between 172 and 430 W / m2*K) at flow rates of 10 - 20 cm / s. The significance of this problem is further illustrated by Ghadge’s report of actual heat transfer coefficients observed under “fouled” conditions which are of the samer order of magnitude as the fouling resistance itself - between 204 and 499 W / m2*K. We have discovered that “fouling factor” for lignocellulosic biomass streams in HTL processing can be significantly reduced through the use of pulsed, high velocity flow through the feed stream heat exchanger and downstream HTL reactor. This can be routinely achieved using our combined reactor loading / unloading pump system described in WO2022 / 194332. The combined feeding / unloading pump system can be controlled so that the pressurized feedstream input stroke is very rapid, creating rapid velocity pulsatile input flow within the range 50 - 500 cm s-1. We have previously demonstrated how oscillatory flow, in general, improves heat exchanger efficiency, by introducing turbulence into the forward flow (Johannsen 2021). Turbulence is well known to enhance heat exchanger efficiency. Moreover, in most systems previously studied, turbulence reduces heat exchanger fouling (Hasan 2012; Ying 2012; Wang 2016; Tu 2022), presumably by disrupting“ residence time” within semi-stationary layers on wall surfaces - a technical effect which is particularly relevant to the avoidance of char formation. High velocity itself is also expected to reduce fouling. Thus, high velocity, pulsatile flow of the process stream simultaneously improves both efficiency and “fouling factor” of HTL heat exchangers. This combined reactor loading / unloading pump system operated so as to provide high velocity, pulsatile flow can be employed with beneficial effect where multiple systems are operated in paralell together with multiple post-reactor hydrocyclones configured to remove inorganic solids from the product stream. The multiple hydrocyclones, operated under reactor conditions where inorganic solids are insoluble in aqueous phase, can be used in such manner that the high velocity process flow pulse driven by one pump is processed by one hydrocyclone with enhanced separation performance due to high velocity, notwithstanding discontinuous operation. In one aspect, the invention relates to a system for thermochemical biomass conversion comprising: - two or more pump systems each configured to pressurize biomass feedstock slurry and introduce it into an HTL process stream pressurized to at least 130 bar and also to depressurize HTL product and remove it from an HTL product stream pressurized to at least 130 bar; - a heat exchanger system comprising separate tubes for feedstock input and product output configured to heat biomass feedstock slurry after it is introduced under pressure into the HTL process stream by counter-current exchange with the HTL product stream; - an HTL reactor in fluid communication with and downstream from the heat exchanger system; and - a control system configured to control each of the two or more pump systems so that the feedstock input flow it drives is pulsatile; - wherein each of the two or more pump systems is configured to drive input of biomass feedstock and to remove HTL product stream from separate sets of input and output tubes within the heat exchanger that are dedicated to that pump system. In an embodiment of the invention, the system further comprises two or more hydrocyclone separators configured to separate solids from the HTL product stream downstream from the HTL reactor, - wherein each of the two or more hydrocyclone separators is configured to process the product output flow driven by one pump. In an embodiment of the invention, the heat exchanger comprises comparatively thin-walled conduits with wall thickness less than 3.5 mm made of corrosion resistant alloy material that is introduced into heat transfer members made of carbon steel or similar material by expanded fit. In an embodiment of the invention, the heat exchanger comprises comparatively thin-walled conduits with wall thickness less than 3.5 mm made of appropriate corrosion resistant, expensive alloy material that is introduced into heat transfer members made of inexpensive carbon steel or similar material by expanded fit. In an embodiment of the invention, the hydrocyclone separators have internal diameter within the range 6 and 30 cm. In one aspect, the invention relates to a method for biomass conversion comprising the steps of inputing biomass feedstock slurry and removing product oil output from the system for thermochemical biomass conversion of the invention or any of its embodiments. In an embodiment of the invention, the method is conducted in such manner that the pulsatile feedstock input flow produced by each of the one or more pump systems has at least twice the velocity of the net average flow that the pump drives through the heat exchanger input and output tubes. In an embodiment of the invention, the method is conducted in such manner that the pulsatile feedstock input flow produced by each of the one or more pump systems has at least twice the velocity of the net average flow that the pump drives through the heat exchanger input and output tubes. In an embodiment of the invention, the method conducted in such manner that the pulsatile feedstock input flow produced by each of the one or more pump systems is oscillatory such that net average forward flow includes both forward and reverse components In an embodiment of the invention, the method is conducted in such manner that the pulsatile feedstock input flow produced by each of the one or more pump systems is oscillatory such that net average forward flow includes both forward and reverse components. In an embodiment of the invention, the pulsatile feedstock input stroke includes at least three forward strokes and at least two backward strokes. In an embodiment of the invention, the pulsatile feedstock input stroke includes at least three forward strokes and at least two backward strokes. In an embodiment of the invention, the heat transfer coefficient obtained is at least 700 W / m2*K. In an embodiment of the invention, the heat transfer coefficient obtained is between 750 W / m2*K and 1000 W / m2*K.

[0002] BRIEF DESCRIPTION OF THE FIGURES Figure 1. Shows an HTL pumping cylinder as described in WO2022 / 194332 used in the HYLIQ 5000 (™) system. Figure 2. Shows one section of a heat exchanger system as described in WO2021 / 024176 used in the HYLIQ 5000 (™) system. Figure 3. Shows an HTL reactor used in the HYLIQ 5000 (™) system. Figure 4. Shows a series of small hydrocyclone separators used in the HYLIQ 5000 (™) system. Figure 5. Piping and instrumentation diagram (P&ID) for the feedstock input and product output pumps of the HYLIQ 5000 (™) system. Figure 6. Piping and instrumentation diagram (P&ID) for the heat exchanger, HTL reactor and hydrocyclone separators of the HYLIQ 5000 (™) system.

[0003] DESCRIPTION OF EMBODIMENTS In some embodiments, the invention provides a system for thermochemical biomass conversion comprising: - two or more pump systems each configured to pressurize biomass feedstock slurry and introduce it into an HTL process stream pressurized to at least 130 bar and also to depressurize HTL product and remove it from an HTL product stream pressurized to at least 130 bar; - a heat exchanger system comprising separate tubes for feedstock input and product output configured to heat biomass feedstock slurry after it is introduced under pressure into the HTL process stream by counter-current exchange with the HTL product stream; - an HTL reactor in fluid communication with and downstream from the heat exchanger system; and - a control system configured to control each of the two or more pump systems so that the feedstock input flow it drives is pulsatile; - wherein each of the two or more pump systems is configured to drive input of biomass feedstock and to remove HTL product stream from separate sets of input and output tubes within the heat exchanger that are dedicated to that pump system. In some embodiments the system further comprises: - two or more hydrocyclone separators configured to separate solids from the HTL product stream downstream from the HTL reactor, - wherein each of the two or more hydrocyclone separators is configured to process the product output flow driven by one pump. In some embodiments, the dimensions of the hydrocyclone separators are determined according to common standards as described in Chemical Engineering Design (2013) by G. Towler and R. Sinnot. All dimensions are derived from the hydrocyclone internal diameter. In some embodiments, internal diamater of the hydrocyclones is between 6 and 30 cm. The hydrocyclones shown in Figure 4 have internal diameter 10 cm. In some embodiments, each of the two or more pump systems corresponds to one or more embodiments presented in WO2022 / 194332, which is hereby incorporated by reference in entirety. In some embodiments, the heat exchanger corresponds to one or more embodiments presented in WO2021 / 024176, which is hereby incorporated by reference in entirety. In some embodiments the heat exchanger comprises comparatively thin-walled conduits with wall thickness less than 3.5 mm, or less than 2.0 mm, made of appropriate corrosion resistant, expensive alloy material that is introduced into heat transfer members made of inexpensive carbon steel or similar material by expanded fit. It is generally advantageous that each of the two or more pump systems is configured to drive input of biomass feedstock and to remove HTL product stream from separate sets of input and output tubes within the heat exchanger that are dedicated to that pump system because, in this manner, the velocity of each pulse can be enhanced and overall control of flow improved compared with the situation where two or more pump systems drive a single input and a single output tube. In some embodiments, the system includes any or all of the features exhibited by the commercial proto type HYLIQ 5000 (™) modular HTL system produced by CIRCLIA NORDIC ApS, Aarhus, Denmark. This comprises three separate pumping cylinders as described in WO2022 / 194332, one example of which is shown in Figure 1. Biomass feedstream is introduced into the pressurized HTL process stream through the inlet end (on the left as shown) while HTL product oil is removed through the the outlet end (on the right as shown). Each pumping cylinder drives process flow through one tubular input conduit and through one tubular output conduit within a bundle of six (6) conduits within a heat exchanger assembly as described in WO2021 / 024176, one linear section of which is shown in Figure 2. Process flow through the inlet conduits is driven downstream of the heat exchanger system into a combined single tube which then comprises the HTL reactor - 80 meters of SS316L (EN1.4401) stainless steel tubing (internal diameter 42 mm, wall thickness 10.5 mm) as shown in Figure 3 without the surrounding insulating material that is used in practice. The three phase (aqueous, oil and gas) HTL product stream downstream of the HTL reactor is fed into three hydrocyclone separators shown in Figure 4 which are operated sequentially where flow through the system is pulled by operation of the three pumps operating sequentially. Piping and instrumentation diagrams (P&IDs) for the feedstock input and product output pumps of the HYLIQ 5000 (™) system are shown in Figure 5 while those for the heat exchanger, HTL reactor and hydrocyclone separators are shown in Figure 6. One skilled in the art will readily understand that, as shown, biomass feedstock slurry is drawn from a storage tank (1) maintained under conditions of constant recirculation. Each of three pump cylinders (2a, 2b, 2c) acts to draw the feedstream through low pressure valves (3a, 3b, 3c) on the inlet end (left side as shown) and to introduce the pressurized feedstock stream to the HTL process stream through high pressure valves (4a, 4b, 4c) on the inlet end. Each of three pump cylinders (2a, 2b, 2c) further acts to withdraw pressurized HTL output through high pressure valves (5a, 5b, 5c) situated on the outlet end (right side as shown) and to output depessurized product through low pressure valves (6a, 6b, 6c) on the outlet end. An axially displaceable piston (7a, 7b, 7c) in each pump cylinder moves towards the outlet end on a feedstream loading / product output stroke and towards the inlet end on the feedstream pressurization and input / product depressurization and loading stroke. The duration of the two respective pump strokes can be controlled in such manner that the feedstream loading stroke is slower whereas the feedstream pressurization and input stroke is faster. This results in a pulsatile input whereby the quantity of feedstream corresponding to one loading stroke is rapidly introduced to the HTL process flow with a velocity of between 50 and 500 cm / s. Each pump cylinder (2a, 2b, 2c) drives process flow through both an input (8a, 8b, 8c) and an output (9a, 9b, 9c) conduit within the heat exchanger (10). The process flow through the inlet conduits (8a, 8b, 8c) is combined downstream of the heat exchanger (10) into one flow (11) that is directed through the HTL reactor (12). The process flow (13) downstream of the HTL reactor is routed into a circuit connected to each of three hydrocyclones (14a, 14b, 14c) each of which is configured to process flow driven by one pump cyclinder (2a, 2b, 2c) through one output conduit (9a, 9b, 9c) in the heat exchanger (10). The pump cyclinders are controlled so as to operate sequentially such that at any given moment, only one pump cyclinder is withdrawing product output from the combined HTL product circuit. The HTL reactor (12) may comprise a trimheater. Regarding the figures, the following figure references are noted: 101: HTL pumping cylinder 201: One section of the heat exchanger system 301: HTL reactor 401: Series of hydrocyclone separators. 501: Feedstock in 502: Feed tank 503: Water expansion tank 504: Pressure exchangers 505: Low pressure 506: High pressure 507: Solidflush Out 508: TPS Inlet 601: Solids In some embodiments, the invention provides a method for biomass conversion comprising the steps of inputing biomass feedstock slurry and removing product oil output from a system for thermochemical biomass conversion comprising: - two or more pump systems each configured to pressurize biomass feedstock slurry and introduce it into an HTL process stream pressurized to at least 130 bar and also to depressurize HTL product and remove it from an HTL product stream pressurized to at least 130 bar; - a heat exchanger system comprising separate tubes for feedstock input and product output configured to heat biomass feedstock slurry after it is introduced under pressure into the HTL process stream by counter-current exchange with the HTL product stream; - an HTL reactor in fluid communication with and downstream from the heat exchanger system; and - a control system configured to control each of the two or more pump systems so that the feedstock input flow it drives is pulsatile; - wherein each of the two or more pump systems is configured to drive input of biomass feedstock and to remove HTL product stream from separate sets of input and output tubes within the heat exchanger that are dedicated to that pump system. In some embodiments the method is conducted in such manner that the pulsatile feedstock input flow produced by each of the one or more pump systems has at least twice the velocity of the net average flow that the pump drives through the heat exchanger input and output tubes. In some embodiments the method is conducted in such manner that the pulsatile feedstock input flow produced by each of the one or more pump systems is oscillatory such that net average forward flow includes both forward and reverse components as described in WO2016 / 004958. In some embodiments, oscillation is provided by an input stroke that includes at least two forward strokes and at least one backward stroke, or at least three forward strokes and at least two backward strokes. In some embodiments, the method further comprises use of two or more hydrocyclone separators configured to separate solids from the HTL product stream downstream from the HTL reactor, wherein each of the two or more hydrocyclone separators is configured to process the product output flow driven by one pump. In some embodiments, heat transfer coefficient obtained using the method is at least 700 W / m2*K, or at least 800 W / m2*K, or between 750 W / m2*K and 1000 W / m2*K. Examples. 1. Measurement of initial heat exchanger efficiency of the HYLIQ 5000 (™) modular HTL system. The initial heat exchanger efficiency of this system was estimated using hot water as follows: A 9.5 m long section of a heat exchanger as described in WO2021 / 024176 was prepared using three (3) Inconel 625 (™) conduits having initial wall thickness 1.2 mm and initial internal diameter 24.27 mm that were subject to mechanical expansion so as to fit within carbon steel heat transfer members that were fit together so as to have a combined tubular geometry. Water heated to 60oC was driven through two of the conduits at constant flow 58 cm / s counter-current to cold water 17.5oC driven through the third conduit. The difference in temperature between the cold water stream at the inlet and outlet was used to estimate the heat transfer capability of the system as 1.6 kW / m, corresponding to a heat transfer coefficient for this system of 808 W / m2*K. 2. Demonstration of improved heat exchanger efficiency through application of pulsed high velocity process flow. The HYLIQ 5000 (™) modular HTL system was employed on site at an industrial bio-diesel production facility to process residual bio-waste sludge. A baseline test of the system operated with water alone was conducted as follows: A baseline run with water alone was initiated at flow rate 820 kg / hr corresponding to net linear velocity of 17.0 cm / s. Initially cold water 17oC was introduced to the HYLIQ 5000 (™) and run through the pumps into the heat exchanger and then the HTL reactor at process temperature 329oC after which output product oil was removed through the heat exchanger and pumps. The pumps were operated so as to provide a pulsatile input velocity that was twice the net average flow. The temperature of inlet and outlet points of the heat exchanger inlet and outlet conduits for a total of 12 individual temperature measurements were taken with minimum 60 s repeat cycle. Averages obtained over a period of one hour after flow through the system was stabilized were used to calculate the obtained heat transfer coefficient (U) of the system at this flow rate according to the formula U = Q / A*LMTD where LMTD is “logarithmic mean temperature difference.” Q was calculated as the change in specific enthalpy Q1 of the hot input stream to output and of the cold input stream Q2 to output with the assumption that heat loss was equal on both sides and that Q1=Q2. LMTD was calculated using the formula [ΔTin (hot in - cold in) - ΔTout (hot out - cold out)] / [and ln (ΔTin / ΔTout)]. The observed heat transfer coefficient in this run was 1003.91 W / m2*K. As shown, notwithstanding considerably lower net average velocity flow, the heat transfer coefficient of the system operated with water alone using pulsed high velocity flow was improved compared with the continuous flow measurement of 808 W / m2*K described in example 1. 3. Demonstration of improved “fouling factor” through application of pulsed high velocity process flow. The system described in example 2 was used to process a stream of process residual sludge from a biodiesel plant comprising about 18 wt. % dry matter at flow rate 820 kg / hr corresponding to net linear velocity about 17.0 cm / s. Process residual was input at about 33.5oC and run through the HTL reactor at process temperature 320oC. The pumps were operated so as to provide a pulsatile input velocity that was twice the net average flow. The temperature of inlet and outlet points of the heat exchanger inlet and outlet conduits for a total of 12 individual temperature measurements were taken with minimum 60 s repeat cycle. Averages obtained over a period of one hour after flow through the system was stabilized were used to calculate the obtained heat transfer coefficient (U) (as described in example 2) of the system at this flow rate of 980.99 W / m2*K. Process residual was input in a subsequent separate run at flow rate 847 kg / hr corresponding to linear velocity about 17.6 cm / s at temperature 45oC and run through the HTL reactor at process temperature 328oC. The pumps were operated so as to provide a pulsatile input velocity that was twice the net average flow. The temperature of inlet and outlet points of the heat exchanger inlet and outlet conduits for a total of 12 individual temperature measurements were taken with minimum 60 s repeat cycle. Averages obtained over a period of six hours after flow through the system was stabilized were used to calculate the obtained heat transfer coefficient (U) of the system (as described in example 2) at this flow rate of 807.38 W / m2*K. This shows that the heat transfer coefficient of this system operated with biodiesel residual sludge using pulsed high velocity flow was diminished by less than 20% compared with the “water only” baseline determined in example 2 and was considerably greater than the “best case” of 499 W / m2*K reported by Ghadge and coworkers (2022). 4. Demonstration of adequate separation efficiency from discontinuous, sequential operation of comparatively small hydrocyclones processing pulsed high velocity process flow driven by multiple pump systems. In the on-site test of the HYLIQ 5000 (™) modular HTL system referred to in examples 2 and 3, the product stream downstream from the HTL reactor was subject to solid / liquid separation using the hydrocyclone separators shown in Figure 4. The hydrocyclones were operated in a manner that was discontinuous in that each hydrocyclone was associated with the pulsed high velocity process flow driven by one of the three pumps employed as shown in Figure 6. Although data concerning detailed mass balances and size distributions of separated particles were not determined, approximately 300 kg solid dry matter was separated by the hydrocyclones over a period of about 72 hours run time. This indicates that the hydrocyclones functioned with reasonable efficiency. The embodiments and examples described are descriptive only and not intended to limit the scope of the invention(s) as defined by the claims. PATENT REFERENCES CITED WO2021 / 024176 WO2022 / 194332 WO2024 / 076806 NON-PATENT REFERENCES CITED Castello, D. et al. “Continuous Hydrothermal Liquefaction of Biomass: A Critical Review,”Energies (2018) 11:3165. Chornet, E. and Overend, R. “Biomass liquefaction: an overview,” Chapter 54, Fundamentals of Thermochemical Biomass Conversion, Elsevier 1985. Elliot, D. et al. “Hydrothermal liquefaction of biomass: Developments from batch to continuous process,” Bioresource Technology (2015) 178:147. Ghadge, R. et al. “Design and scale-up challenges in hydrothermal liquefaction process for biocrude production and its upgradation,” Energy Conservation and Management (2022) 14: 100223 Hasan, B. et al. “The use of turbulence generators to mitigate crystallization fouling under cross flow conditions,” Desalintion (2012) 288:108. Johannsen, I. et al. “Design, Modelling, and Experimental Validation of a Scalable Continuous-Flow Hydrothermal Liquefaction Pilot Plant,” Process (2021) 9:234. Mathanker, A. et al. “A Review of Hydrothermal Liquefaction of Biomass for Biofuels Pro- duction with a Special Focus on the Effect of Process Parameters, Co- Solvents, and Ex- traction Solvents,” Energies (2012) 14:4916. Thorson, M. “3.4.2.301 PNNL Hydrothermal PDUs: Systems development and integration,” PNNL May 3, 2023. Towler, G. and Sinnott, R. Chemical Engineering Design: Principles, Practice and Economics of Plant and Process Design, 2d edition (2013) Elsevier Thorson, M. “Hydrothermal liquefaction of wet wastes for SAF,” PNNL June 20, 2023. Tu, J. et al. “Experimental study on the particle fouling properties of magnetic nanofluids in a corrugated tube with built-in twisted turbulator under variable magnetic field,” Powder Technology (2022) 400:117216. Ying, W. et al. “A CFD-based analysis on trends of heat exchanger fouling,” Asia- Pacific Power and Energy Engineering Conference (2012). Wang, L.C. et al. “Relationships between the characteristics of CaCO3 fouling and the flow velocity in smooth tube,” Experimental Thermal and Fluid Science (2016) 74:143

Claims

CLAIMS 1. A system for thermochemical biomass conversion comprising: - two or more pump systems each configured to pressurize biomass feedstock slurry and introduce it into an HTL process stream pressurized to at least 130 bar and also to depressurize HTL product and remove it from an HTL product stream pressurized to at least 130 bar; - a heat exchanger system comprising separate tubes for feedstock input and product output configured to heat biomass feedstock slurry after it is introduced under pressure into the HTL process stream by counter-current exchange with the HTL product stream; - an HTL reactor in fluid communication with and downstream from the heat exchanger system; and - a control system configured to control each of the two or more pump systems so that the feedstock input flow it drives is pulsatile; - wherein each of the two or more pump systems is configured to drive input of biomass feedstock and to remove HTL product stream from separate sets of input and output tubes within the heat exchanger that are dedicated to that pump system.

2. The system of claim 1 further comprising two or more hydrocyclone separators configured to separate solids from the HTL product stream downstream from the HTL reactor, - wherein each of the two or more hydrocyclone separators is configured to process the product output flow driven by one pump.

3. The system of claim 1 or 2, wherein the heat exchanger comprises comparatively thin-walled conduits with wall thickness less than 3.5 mm made of corrosion resistant alloy material that is introduced into heat transfer members made of carbon steel or similar material by expanded fit.

4. The system of claim 1 or 2, wherein the heat exchanger comprises comparatively thin-walled conduits with wall thickness less than 3.5 mm made of appropriatecorrosion resistant, expensive alloy material that is introduced into heat transfer members made of inexpensive carbon steel or similar material by expanded fit.

5. The system according to any of claims 2-4, wherein the hydrocyclone separators have internal diameter within the range 6 and 30 cm.

6. A method for biomass conversion comprising the steps of inputing biomass feedstock slurry and removing product oil output from the system for thermochemical biomass conversion of any of claims 1-5.

7. A method for biomass conversion comprising the steps of inputing biomass feedstock slurry and removing product oil output from the system for thermochemical biomass conversion of claim 2.

8. The method of any of claims 6-7 conducted in such manner that the pulsatile feedstock input flow produced by each of the one or more pump systems has at least twice the velocity of the net average flow that the pump drives through the heat exchanger input and output tubes.

9. The method of claim 7 conducted in such manner that the pulsatile feedstock input flow produced by each of the one or more pump systems has at least twice the velocity of the net average flow that the pump drives through the heat exchanger input and output tubes.

10. The method of any of claims 6-9 conducted in such manner that the pulsatile feedstock input flow produced by each of the one or more pump systems is oscillatory such that net average forward flow includes both forward and reverse components 11. The method of any of claims 6-10 conducted in such manner that the pulsatile feedstock input flow produced by each of the one or more pump systems isoscillatory such that net average forward flow includes both forward and reverse components.

12. The method of any of claims 6-11, wherein the pulsatile feedstock input stroke includes at least three forward strokes and at least two backward strokes.

13. The method of any of claims 6-12, wherein the pulsatile feedstock input stroke includes at least three forward strokes and at least two backward strokes.

14. The method of any of claims 6-13, wherein the heat transfer coefficient obtained is at least 700 W / m2*K.

15. The method of any of claims 6-14, wherein the heat transfer coefficient obtained is between 750 W / m2*K and 1000 W / m2*K.

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