WO2023232953A2

WO2023232953A2 - Heat exchange system and method for heating a utilization heat carrier medium by cooling an incoming flow of liquid biomass

Info

Publication number: WO2023232953A2
Application number: PCT/EP2023/064715
Authority: WO
Inventors: Per AASTED
Original assignee: Aalborg Csp A/S
Priority date: 2022-06-01
Filing date: 2023-06-01
Publication date: 2023-12-07
Also published as: WO2023232953A3

Abstract

Herein is disclose a method and a heat exchange system for heating a utilization heat carrier medium (13) by cooling an incoming flow of liquid biomass (17), the method comprising the steps of passing the flow of liquid biomass through a first heat exchanger (21) for transferring thermal energy from the flow of liquid biomass to a flow of a first liquid heat carrier medium, passing the flow of the first liquid heat carrier medium from the first heat exchanger to a first evaporator (9), where liquid refrigerant evaporates and thereby cools the first liquid heat carrier medium, passing the evaporated, gaseous refrigerant from the first evaporator to a compressor ((4), where the gaseous refrigerant is compressed, and passing the compressed gaseous refrigerant from the compressor to a refrigerant liquefier (5, 6, 7), wherein the gaseous refrigerant is cooled by transferring thermal energy to the utilization heat carrier medium and is liquefied. Furthermore is disclosed a tubular heat exchanger comprising a cutter arrangement (49) comprising at least one cutting edge (50) within the inlet plenum and cutter drive means (32) arranged to drive the at least one cutting edge to sweep across the inlet tube sheet in close proximity to the plane surface of the inlet tube sheet so that an opening edge (47) of each of the through-holes may be swept by at least one of the cutting edges so as to cut any possible solid matter (51) clogging the through-holes of the inlet tube sheet.

Description

Heat exchange system and method for heating a utilization heat carrier medium by cooling an incoming flow of liquid biomass

The present invention relates to a heat exchange system and a method for heating a utilization heat carrier medium by cooling an incoming flow of liquid biomass, wherein a refrigerant undergoes phase transitions in a heat exchange cycle.

Brief description of the invention

The present invention relates in a first aspect to a method for heating a utilization heat carrier medium by cooling an incoming flow of liquid biomass, the method comprising the steps of passing the flow of liquid biomass through a first heat exchanger for transferring thermal energy from the flow of liquid biomass to a flow of a first liquid heat carrier medium, passing the flow of the first liquid heat carrier medium from the first heat exchanger to a first evaporator, where liquid refrigerant evaporates and thereby cools the first liquid heat carrier medium, passing the evaporated, gaseous refrigerant from the first evaporator to a compressor, where the gaseous refrigerant is compressed, and passing the compressed gaseous refrigerant from the compressor to a refrigerant liquefier, wherein the gaseous refrigerant is cooled by transferring thermal energy to the utilization heat carrier medium and is liquefied.

In some embodiments a flow rate of the incoming liquid biomass is at least 10 m3/hr, such as at least 20 m3/hr, such as at least 25 m3/hr.

Liquid biomass typically has a temperature at which ammonia is prone to evaporate at a significant rate from the liquid biomass. Thus, by heating a utilization heat carrier medium by cooling an incoming flow of liquid biomass, the temperature of the liquid biomass is reduced, while the utilization heat carrier medium is heated. By reducing the temperature of liquid biomass, the evaporation rate of ammonia is reduced. This has two advantages. Firstly, since ammonia gas has a very sharp odor, a reduced evaporation of ammonia leads to a less odor rich liquid biomass. Secondly, by reducing the evaporation of ammonia, the ammonia will remain in the liquid biomass, and thus offer a more ammonia rich fertilizer based on the liquid biomass. Thus, the use of a flow of liquid biomass to heat the utilization heat carrier medium has more advantages also for the handling of the flow of liquid biomass.

The first liquid heat carrier medium is preferably water, such as tap water and could alternatively be e.g. an oil or a brine. The utilization heat carrier medium is preferably water, e.g. for district heating or industrial use.

By using a first liquid carrier medium to transfer thermal energy from the flow of liquid biomass to the first evaporator, the risk of formation of ice particles in the liquid biomass in the heat exchanger due to low local temperature of the evaporating refrigerant, which carries a high risk of clogging the heat exchanger together with solid or gel-formed particles in the liquid is avoided. Also, a better heat transfer from the liquid biomass in the first heat exchanger may be obtained with liquids on both sides of the heat exchange, i.e. the liquid biomass and the first liquid heat carrier medium, as opposed to liquid /gaseous phase on the two sides of the heat exchanger, i.e. the liquid biomass and the evaporated refrigerant.

According to one embodiment, the refrigerant liquefier is a condenser, in which the gaseous refrigerant is condensed to liquid refrigerant, which may be used for refrigerants as ammonia (NH4) and R134a (1,1,1,2-Tetrafluoroethane).

According to another embodiment, the refrigerant is carbon dioxide (CO2) and the refrigerant liquefier comprises a gas cooler, which is arranged for or configured for cooling the compressed refrigerant by heat exchanging with the utilization heat carrier medium and an intermediate pressure receiver tank, also known as a flash tank, connected to an outlet of the gas cooler via a receiver expansion valve. In some embodiments, the liquid biomass in the heat exchanger is configured to flow in a plurality of tubes, the plurality of tubes being surrounded by the utilization heat carrier medium. Thus, for example, the liquid heat carrier medium may be configured to flow over the plurality of tubes.

In some embodiments, passing the flow of liquid biomass through a first heat exchanger for transferring thermal energy from the flow of liquid biomass to a flow of a first (or further) liquid heat carrier medium, includes passing the flow of liquid biomass through a plurality of tubes.

In some embodiments, the first (or further) liquid heat carrier medium flows around the plurality of tubes.

The first heat exchanger may in particular comprise a tubular heat exchanger having a shell enclosing a tube bundle extending between an inlet plenum and outlet plenum of the tubular heat exchanger, the shell being provided with a shell side inlet opening and a shell side outlet opening, and the inlet plenum being provided with a tube side inlet opening and the outlet plenum being provided with a tube side outlet opening, and wherein the flow of liquid biomass passes from the tube side inlet opening to the tube side outlet opening, and the flow of the first liquid heat carrier medium passes from the shell side inlet opening to the shell side outlet opening.

It is noted that the liquid biomass has a high viscosity compared to water, e.g. typically such as a factor 10 higher than the viscosity of water. As the liquid biomass further is a non-newtonian fluid, the viscosity is not constant and the heat transfer properties of the liquid biomass may be impaired. By using a plurality of tubes being surrounded by liquid heat carrier medium, a sufficient heat transfer between the liquid biomass and the liquid heat carrier medium is obtained.

The method may further comprise the step of recirculating a part of the flow of liquid biomass through the first heat exchanger from an outlet of the first heat exchanger to an inlet of the first heat exchanger by means of a first pump arrangement. Hereby, the total transfer of heat or thermal energy from the liquid biomass may be improved.

In some embodiments, since the recirculated part of the flow of liquid biomass has a lower temperature than the incoming flow of liquid biomass, the recirculation may decrease the overall temperature of the flow of liquid biomass through the first heat exchanger, which may reduce a temperature difference between the first liquid heat carrier medium and the flow of liquid biomass, to thereby further reduce the risk of ice particle formation. Additionally, such lower temperature diffence may reduced any built up of struvit.

In some embodiments, the step of recirculating a part of the flow of liquid biomass through the first heat exchanger include adding the recirculated part of the flow of biomass to the incoming flow of liquid biomass, to thereby increase the combined flow of liquid biomass through the first heat exchanger. Hereby, a flow rate of the combined flow of the incoming flow of liquid biomass and the recirculated flow of liquid biomass through the first heat exchanger may be at least 2 times the flow rate of the incoming flow of liquid biomass.

Preferably, a flow rate of the combined flow of the incoming liquid biomass and the recirculated part of liquid biomass through the first heat exchanger may be at least 3 times the flow rate of the incoming flow of liquid biomass, such as in the range of 3 to 6 times said flow rate. In some embodiments, the flow rate of incoming liquid biomass is between 15 m3/hr and 50 m3/hr, such as between 20 m3/hr and 30 m3/hr, such as about 25 m3/hr. In some embodiments, the recirculated flow of liquid biomass has a flow rate of twice the flow rate of the incoming liquid biomass.

In some embodiments, the method may further comprise the step of passing a flow of liquid biomass from an outlet of the first heat exchanger through a second heat exchanger for transferring thermal energy from said flow of liquid biomass to a flow of a second liquid heat carrier medium, passing the flow of the second liquid heat carrier medium from the second heat exchanger to a second evaporator, where liquid refrigerant evaporates and thereby cools the second liquid heat carrier medium, passing the evaporated, gaseous refrigerant from the second evaporator and to a compressor, and passing the compressed, gaseous refrigerant from the compressor to the gas cooler, wherein the gaseous refrigerant is cooled by transferring thermal energy to the utilization heat carrier medium.

The compressor may be the same compressor as the gaseous refrigerant of the first evaporator is passed to, such as a two-step compressor, or the compressor may comprise to different compressor, a low-pressure compressor to which the evaporated, gaseous refrigerant from the second evaporator is led, and a high- pressure compressor to which the compressed refrigerant from the low-pressure compressor is led as well as the evaporated, gaseous refrigerant from the first evaporator.

The second heat exchanger may likewise comprises a tubular heat exchanger having a shell enclosing a tube bundle extending between an inlet plenum and outlet plenum of the tubular heat exchanger, the shell being provided with a shell side inlet opening and a shell side outlet opening, and the inlet plenum being provided with a tube side inlet opening and the outlet plenum being provided with a tube side outlet opening, and wherein the flow of liquid biomass passes from the tube side inlet opening to the tube side outlet opening, and the flow of the second liquid heat carrier medium passes from the shell side inlet opening to the shell side outlet opening.

The second liquid heat carrier medium is preferably water (tap water), and could instead be e.g. an oil or a brine.

The boiling temperature of the liquid refrigerant in the second evaporator is preferably at least 6° C lower than the boiling temperature of the liquid refrigerant in the first evaporator, such as at least 10° C lower, which means that the first evaporator is a high pressure evaporator and the second evaporator is a low pressure evaporator. It is an advantage of passing the flow of liquid biomass through a first heat exchanger and a second heat exchanger, having a first high pressure evaporator and a second low pressure evaporator, respectively, that a temperature difference between the flow of liquid biomass and the first, respectively second liquid heat carrier medium, can be kept lower than if only one heat exchanger is employed.

The method may further comprise the step of recirculating a part of the flow of liquid biomass through the second heat exchanger from an outlet of the second heat exchanger to an inlet of the second heat exchanger by means of a second pump arrangement, wherein the flow rate of the liquid biomass through the second heat exchanger may be at least 2 times, preferably at least 3 times the flow rate of the incoming flow of liquid biomass, more preferred in the range of 3 to 6 times said flow rate.

The liquid biomass is preferably a slurry with at least 2 to 10 % by weight of solid matter, such as 4 to 8%, such as liquid or semi-liquid manure. The liquid biomass may for example be degassed slurry, unfiltered wastewater, liquid industry bioresiduals including particles of various sizes.

The present invention furthermore relates to a heat exchange system for heating a utilization heat carrier medium by cooling an incoming flow of liquid biomass, the heat exchange system including a first heat exchanger for cooling the incoming flow of liquid biomass, a first heat carrier circuit arranged for providing a first liquid heat carrier medium to the first heat exchanger to transfer thermal energy from the incoming flow of liquid biomass, a compressor arrangement for compressing a refrigerant in a gaseous state, a refrigerant liquefier arranged to receive the compressed refrigerant from the compressor arrangement, the refrigerant liquefier being arranged to heat the utilization heat carrier medium by heat exchange with the compressed refrigerant, which is thereby cooled, and liquefy the refrigerant, a first evaporator arranged for receiving liquid refrigerant from the refrigerant liquefier via a first evaporator expansion valve, the first evaporator being arranged for cooling the first heat carrier medium by means of evaporation of the liquid refrigerant, the first evaporator being arranged to discharge evaporated, gaseous refrigerant to the compressor arrangement.

In one embodiment, the refrigerant liquefier is a condenser, which is arranged for condensation of the gaseous refrigerant to liquid refrigerant, which is used with a refrigerant such as ammonia (NH4) or R134a.

In another embodiment, the heat exchange system is arranged to use carbon dioxide (CO2) as the refrigerant, wherein the refrigerant liquefier comprises a gas cooler, which is arranged for cooling the compressed refrigerant by heat exchanging with the utilization heat carrier medium and an intermediate pressure receiver tank (flash tank) connected to an outlet of the gas cooler via a receiver expansion valve.

In some embodiments, the heat exchange system comprises a plurality of tubes, such as a tube bundle, and the liquid biomass is configured to flow through the tubes.

Thus, the heat exchange system may be configured to allow the liquid biomass to flow through the plurality of tubes.

In some embodiment the heat exchange system is configured to allow the liquid heat carrier medium around the plurality of tubes, such as around the tubes in the tube bundle. The liquid heat carrier medium, such as the first liquid heat carrier medium and/or the second liquid heat carrier medium may be configured to flow around the plurality of tubes, such as around the tubes in the tube bundle.

In some embodiments, the heat exchange system is a shell-and-tube type heat exchange system having the liquid biomass running through the tubes, and the liquid heat carrier medium flowing over the tubes in the shell.

The first heat exchanger comprises preferably a first tubular heat exchanger having a shell enclosing a tube bundle extending between an inlet plenum and outlet plenum of the first tubular heat exchanger, the shell being provided with a shell side inlet opening and a shell side outlet opening, and the inlet plenum being provided with a tube side inlet opening and the outlet plenum being provided with a tube side outlet opening, and wherein the flow of liquid biomass is arranged to or configured to pass from the tube side inlet opening to the tube side outlet opening, and the flow of the first liquid heat carrier medium is arranged to or configured to pass from the shell side inlet opening to the shell side outlet opening. In some embodiments, the tube bundle comprises a plurality of tubes, the plurality of tubes being arranged parallel to each other. The plurality of tubes may be arranged so that the tubes are straight and parallel to each other.

The heat exchange system may further comprise a first pump arrangement arranged to recirculate a part of the flow of liquid biomass from a tube side outlet opening of the first heat exchanger to a tube side inlet opening of the first heat exchanger.

In some embodiments, the heat exchange system may comprise a heat carrier circuit to drive a flow of the first liquid heat carrier medium in a counter flow. The heat carrier circuit may include a pump. The heat exchange system may further comprise a second heat exchanger for cooling the incoming flow of liquid biomass, wherein the second heat exchanger is arranged to receive the flow of liquid biomass from an outlet of the first heat exchanger, a second heat carrier circuit arranged for providing a second liquid heat carrier medium to the second heat exchanger to transfer thermal energy from the incoming flow of liquid biomass, and a second evaporator arranged for receiving liquid refrigerant from the intermediate pressure receiver tank via a second evaporator expansion valve, the second evaporator being arranged for cooling the second heat carrier medium by means of evaporation of the liquid refrigerant, the second evaporator being arranged to discharge evaporated, gaseous refrigerant to the compressor arrangement.

The second heat exchanger may also comprise a tubular heat exchanger having a shell enclosing a tube bundle extending between an inlet plenum and outlet plenum of the tubular heat exchanger, the shell being provided with a shell side inlet opening and a shell side outlet opening, and the inlet plenum being provided with a tube side inlet opening and the outlet plenum being provided with a tube side outlet opening, and wherein the flow of liquid biomass is arranged to pass from the tube side inlet opening to the tube side outlet opening, and the flow of the second liquid heat carrier medium is arranged to pass from the shell side inlet opening to the shell side outlet opening.

The first evaporator expansion valve and the second evaporator expansion valve are preferably adjusted so that the boiling temperature of the liquid refrigerant in the second evaporator is at least 6° C lower than the boiling temperature of the liquid refrigerant in the first evaporator, such as at least 10° C lower. The heat exchange system may further comprise a second pump arrangement arranged to recirculate a part of the flow of liquid biomass from an outlet of the second heat exchanger to an inlet of the second heat exchanger.

According to an embodiment of the disclosure, a heat exchange system is provided, configured for heating a utilization heat carrier medium by cooling an incoming flow of liquid biomass. The heat exchange system comprises a first heat exchanger configured for cooling the incoming flow of liquid biomass and a first heat carrier circuit configured for providing a first liquid heat carrier medium to the first heat exchanger to transfer thermal energy from the incoming flow of liquid biomass. The heat exchange system further comprises a compressor arrangement configured for compressing a refrigerant in a gaseous state, a refrigerant liquefier configured to receive the compressed refrigerant from the compressor arrangement, wherein the refrigerant liquefier is being configured to heat the utilization heat carrier medium by heat exchange with the compressed refrigerant. The compressed refrigerant is thereby cooled, and the refrigerant is liquefied. The heat exchange system further comprises a first evaporator configured for receiving liquid refrigerant from the refrigerant liquefier, e.g. via a first evaporator expansion valve. The first evaporator is configured for cooling the first heat carrier medium by means of evaporation of the liquid refrigerant, and the first evaporator is configured to discharge evaporated, gaseous refrigerant to the compressor arrangement.

In some embodiments, the refrigerant liquefier is a condenser, which is configured for condensation of the gaseous refrigerant to liquid refrigerant.

In some embodiments, the heat exchange system is configured for use of carbon dioxide (CO2) as the refrigerant. The refrigerant liquefier may comprise a gas cooler, which is configured for cooling the compressed refrigerant by heat exchanging with the utilization heat carrier medium and an intermediate pressure receiver tank connected to an outlet of the gas cooler e.g. via a receiver expansion valve. Generally, as disclosed above with heat exchange system comprising a first heat exchanger and a second heat exchanger, it is envisaged that the heat exchange system may comprise a plurality of heat exchangers, provided in series or in parallel. The heat exchange system may accordingly comprise a plurality of heat carrier circuits, compressor arrangements, refrigerant liquefiers and evaporators to provided for heating of a utilization heat carrier medium as disclosed above. The same applies for the method mutatis mutandis.

According to a second aspect, the present invention relates to a tubular heat exchanger comprising a shell enclosing a tube bundle extending between an inlet plenum and outlet plenum of the heat exchanger, the shell being provided with a shell side inlet opening and a shell side outlet opening, and the inlet plenum being provided with a tube side inlet opening and the outlet plenum being provided with a tube side outlet opening, the heat exchanger comprising an inlet tube sheet with a plurality of through-holes accommodating inlet ends of the tubes of the tube bundle, the inlet tube sheet comprising a plane surface facing the inlet plenum, a cutter arrangement comprising at least one cutting edge within the inlet plenum and cutter drive means arranged to drive the at least one cutting edge to sweep across the inlet tube sheet in close proximity to the plane surface of the inlet tube sheet so that an opening edge of each of the through-holes may be swept by at least one of the cutting edges so as to cut any possible solid matter clogging the through-holes of the inlet tube sheet.

The tubes of the tube bundle extend preferably substantially straight from the inlet plenum to the outlet plenum, so that the interior of the tubes are easier to clean manually should they become clogged by solid material in the liquid biomass.

The inner opening area of each of the tubes of the tube bundle is preferably in the range of 170 mm² to 1400 mm², more preferably in the range of 300 mm² to 700

2 mm . The inner diameter of each of the tubes of the tube bundle is preferably in the range of 15 mm to 40 mm, more preferably in the range of 20 mm to 30 mm. In some embodiments the inner diameter of each of the tubes is below 50 mm, such as below 40 mm.

The bundle of tubes comprises preferably in the range of 30 to 150 tubes, such as in the range of 60 to 120 tubes, such as in the range 30-100 tubes, such as in the range of 30-60 tubes.

The extent of the tubes of the tube bundle is preferably in the range of 3 meter to 12 meter, such as in the range of 5 meter to 8 meter. In some embodiments, the tubes of the tube bundle may be provided in series, with a tube connector therebetween.

In some embodiments, the tubes are made from a heat transferring metal, such as steel. In some embodiments, the tubes are made from a flexible heat transferring material.

Furthermore, the present invention relates to the use of such tubular heat exchanger as described herein for heat exchanging between a slurry containing at least 2 to 10 % by weight of solid matter, such as 4 to 8% and a heat carrier medium, and wherein the slurry passes from the tube side inlet opening to the tube side outlet opening, and the flow of the heat carrier medium passes from the shell side inlet opening to the shell side outlet opening. The slurry is preferably a liquid biomass, such as more preferably liquid manure.

Furthermore, the present invention relates to the method described herein, wherein the tubular heat exchanger of the first heat exchanger is a tubular heat exchanger as disclosed herein. In particular, the tubular heat exchanger of the second heat exchanger may also be a tubular heat exchanger as disclosed herein. The present invention also relates to a heat exchange system as disclosed herein, wherein the tubular heat exchanger of the first heat exchanger is a tubular heat exchanger as disclosed herein.

The present invention furthermore relates to a heat exchange system as disclosed herein, wherein the tubular heat exchanger of the second heat exchanger is a tubular heat exchanger as disclosed herein.

In the present disclosure, a heat exchange system having a first heat exchanger is disclosed, additionally a heat exchange system having a first and a second heat exchanger is disclosed. It is envisaged that the heat exchange system as herein disclosed may also have a plurality of heat exchangers, as herein described. For example, this could be envisaged should a larger temperature decrease be provided.

It is envisaged that any embodiments or elements as described in connection with any one aspect may be used with any other aspects or embodiments, mutatis mutandis.

Brief description of the drawing

Embodiments and examples of the present disclosure are illustrated by the enclosed drawing of which

Fig. l is a diagram of a first embodiment of a heat exchange system,

Fig. 2 is a diagram of a second embodiment of a heat exchange system,

Fig. 3 is a diagram of a third embodiment of a heat exchange system,

Fig. 4 is a section of a tubular heat exchanger,

Fig. 5 shows a cutter arrangement,

Fig. 6 shows an inlet tube sheet, Fig. 7 shows a detail of a cross-section of an inlet tube sheet under use of the tubular heat exchanger.

Fig. 8 is a diagram of a further embodiment of a heat exchange system.

Detailed description of the examples

The first embodiment of a heat exchange system 1 shown in Fig. 1 comprises an inlet 18 for an incoming flow of liquid biomass 17, which typically comes from a biological processing arrangement, such as for the production of biogas. The incoming flow of liquid biomass has a temperature of a temperature of e.g. 41 °C and is during its passage through the heat exchange system 1 cooled to a temperature of the outlet flow of the liquid biomass 19 to e.g. 14 °C. The thermal energy removed from the flow of liquid biomass 17 is transferred to a utilization heat carrier medium 13 which enters the heat exchange system at the inlet for the utilization heat carrier medium 14 and exits at the outlet for the utilization heat carrier medium 15, where the flow may be driven by means of a pump 16 for utilization heat carrier medium. The utilization heat carrier medium may e.g. be water for a district heating system or for an industrial plant.

The incoming flow of liquid biomass 17 passes through a pump 20 and into a first heat exchanger 21 comprising a front tubular heat exchanger 22 and a back tubular heat exchanger 23 from a tube side inlet opening 26 into an inlet plenum 30 of the front tubular heat exchanger 22, through the tubes 43 and into the outlet plenum 31 from which it leaves through the tube side outlet opening 27. From there, the flow of liquid biomass 17 enters the inlet plenum 30 of the back tubular heat exchanger 23 through a tube side inlet opening 26, passes the tubes into the outlet plenum 31 and out through the tube side outlet opening 27 to the second heat exchanger 35. A heat carrier circuit 24 of the first heat exchanger 21 drives a flow of a liquid heat carrier, such as water, in a counter flow by means of a pump 25 for the heat carrier of the first heat exchanger 21. The heat carrier enters the back tubular heat exchanger 23 through a shell side inlet opening 28 and exits through a shell side outlet opening 29 into the shell side inlet opening 28 of the front tubular heat exchanger 22. After heat exchanging with the flow of liquid biomass inside the tubes 43 of the front tubular heat exchanger 22, the heat carrier exits through the shell side outlet opening 29 from which is passes onto the high pressure evaporator 9, where the heat carrier is cooled by heat exchanging with an evaporating refrigerant. In order to increase the heat transfer in the first heat exchanger 21, a recirculation circuit 33 may be employed, where a part of the liquid biomass 17 is recirculated from the tube side outlet opening 27 of the back tubular heat exchanger 23 through a recirculation pump 34 of the first heat exchanger 21 and into the incoming flow of liquid biomass 17. The recirculation circuit 33 may provide a flow of liquid biomass of the magnitude of the incoming flow rate of liquid biomass 17 through the inlet 18 for incoming flow of biomass, even the double or triple or even more of the incoming flow rate of liquid biomass 17 through the inlet 18, depending on the dimensioning of the heat exchange system 1, the requirements of cooling of the liquid biomass 17 and the properties of the liquid biomass 17.

The flow of liquid biomass passes from the first heat exchanger 21 to the second heat exchanger 35, which is arranged substantially as the first heat exchanger 21 with a front tubular heat exchanger 36 and a back tubular heat exchanger 37, a heat carrier circuit 38 that includes a low pressure evaporator 11, where the pressure of the refrigerant is lower than in the high pressure evaporator 10 of the first heat exchanger 21, so that the heat carrier, such as water, of the second heat exchanger is cooled to a lower temperature than the heat carrier of the first heat exchanger 21, and a recirculation circuit 40 for the liquid biomass. The liquid biomass 17 exits the second heat exchanger 35 from the tube side outlet opening 27 of the back tubular heat exchanger 37 to further use or treatment outside of the heat exchange system 1.

The heat exchange system 1 includes a heat pump based on carbon dioxide as refrigerant, comprising a compressor arrangement 2 with a low pressure compressor 3 and a high pressure compressor 4 from which the gaseous, compressed refrigerant at a pressure of about 80 bar is passed to the gas cooler 5, where it is cooled by heat exchanging with the utilization heat carrier medium 13. The gaseous refrigerant passes from the gas cooler 5 to a receiver tank 6, also known as a flash tank via a receiver expansion valve 7, where the pressure is reduced to about 35 bar with the result that most of the gaseous refrigerant is liquefied in the receiver tank 6. Surplus amounts of gaseous refrigerant from the receiver tank 7 passes to the high pressure compressor 4 via the flash valve 8.

Liquid refrigerant from the receiver tank 7 is sent to the high pressure evaporator 9 via the high pressure evaporator expansion valve 10 and to the low pressure evaporator 11 via the low pressure evaporator expansion valve 12, respectively, in order to cool the heat carrier of the first heat exchanger 21 and of the second heat exchanger 35, respectively.

It is understood that the heat pump could be designed for operating with a different refrigerant, such as ammonia (NH4) or R134a (1,1,1,2-Tetrafluoroethane), which would operate differently and have a condenser in place of the gas cooler 5, such amended system design would be obvious to do for the skilled person in the technical field.

The second embodiment of the heat exchange system 1 shown in Fig. 2 deviates from the heat exchange system of Fig. 1 in that the second tubular heat exchanger 35 of Fig. 1 is omitted from the embodiment of Fig. 2, so that the outlet flow of biomass 19 exits the heat exchange system 1 from the tube side outlet opening 27 of the back tubular heat exchanger 23 and the low pressure evaporator 11 and the low pressure compressor 3 of the embodiment of Fig. 1 are omitted in the embodiment of Fig. 2. This provides a more simple system design that is less expensive to manufacture and maintain but extracts less thermal energy from the flow of liquid biomass 17.

The third embodiment of the heat exchange system 1 shown in Fig. 3 has only one tubular heat exchanger 21, 35 in each of the first heat exchanger 21 and the second heat exchanger 35 as compared to the embodiment of Fig. 1. A tubular heat exchanger particularly useful for heat exchange between a slurry with an amount of suspended solid matter 51, such as 2 to 10 % by weight of solid matter 51 on the tube side and a thermal carrier medium, such as water on the shell side of the tubular heat exchanger is shown in Fig. 4. The tubular heat exchanger of Fig. 4 would be useful in the heat exchange systems 1 of Figs. 1 to 3 for liquid biomass such as liquid manure or slurry from a wastewater treatment plant.

The tubular heat exchanger of Fig. 4 comprises, as is common for a tubular heat exchanger, a tube side inlet 26 to an inlet plenum 30 and a tube side outlet 27 from an outlet plenum 31 as well as a shell side inlet 28 and a shell side outlet 29. The tube bundle 44 inside the shell 42 comprises a plurality of straight tubes 43, such as 30 to 150 tubes 43 in the bundle 44 of a length of 3 to 12 meter, connecting the inlet plenum 30 with the outlet plenum 31. The tubes 43 are at the inlet plenum 30 connected to an inlet tube sheet 45 illustrated in Fig. 6 with a corresponding number of through-holes 46 and a corresponding outlet tube sheet at the outlet plenum 31. The tubes 43 have an internal diameter of 15 to 40 mm, which is very small tubular heat exchangers for a slurry with solid matter, which commonly are equipped with tubes of an internal diameter in the range of 65 mm to 125 mm to avoid the solid matter in the slurry from clogging the flow through the tubes 43. However, a smaller internal diameter of the tubes 43 provides for an improved heat transfer between the slurry and the thermal heat carrier medium.

The clogging with solid matter 51 is illustrated in Fig. 7, where the inlet plenum 30 is to the left of the figure, which shows a tube 43 connected to a through-hole 46 of an inlet tube sheet 45. Solid matter 51 in the flow of the slurry from left to right of the figure deposits at and around the opening edge 47 of the through-hole 46 an effectively decreasing the area of the through-hole 46 and with increasing deposit of solid matter 51, the through-hole 46 and the tube 43 risk clogging to a degree that effectively hinders flow through it. In the tubular heat exchanger of Fig. 4, this is prevented by providing the inlet tube sheet 45 with a plane surface 48 facing the inlet plenum 30 and by placing a cutter arrangement 49 in very close proximity to the plane surface 48. The cutter arrangement 49 comprises four cutting edges 50, such as sharpened knife edges 50, and a cutter drive motor 32 arranged to rotate the cutter arrangement 49 by means of a drive axle (not shown) so that the cutting edges 50 sweep across the inlet tube sheet 45 in close proximity to the plane surface 48 whereby the opening edges 47 of each of the through-holes 46 are swept by the cutting edges 50 so as to cut any possible solid matter 51 clogging the through-holes 46 of the inlet tube sheet 45. This acts as a macerator for reducing the size of the solid particles and hinders the clogging at the opening edges and reduces the risk of clogging at other positions in the heat exchange system downstream of the cutter arrangement 49 as the average size of the particles of the solid matter 51 will be reduced. The cooperation of the cutter arrangement 49 and the inlet tube sheet 45 is comparable to the working of the crossing knife and the hole plate of a meat grinder.

Fig. 8 shows a heat exchange system according to an embodiment of the present invention. The heat exchange system configured for heating a utilization heat carrier medium by cooling an incoming flow of liquid biomass 17, comprises a first heat exchanger 21 for cooling the incoming flow of liquid biomass 17 and a first heat carrier circuit 24 arranged for providing a first liquid heat carrier medium to the first heat exchanger 21 to transfer thermal energy from the incoming flow of liquid biomass. The first liquid heat carrier medium flows in the shell 42 around tubes 43. The flow of liquid biomass 17 passes through a pump 20 and into heat exchanger 21 via inlet 26, and exits via outlet 27. The liquid biomass 17 flows through a plurality of tubes 43 from inlet 26 to outlet 27.

The heat exchange system comprises a compressor arrangement 2 for compressing a refrigerant in a gaseous state and a refrigerant liquefier 5, 6, 7 arranged to receive the compressed refrigerant from the compressor arrangement 2. The refrigerant liquefier 5, 6, 7 is being arranged to heat the utilization heat carrier medium by heat exchange with the compressed refrigerant, which is thereby cooled, and liquefy the refrigerant. A first evaporator 9 is arranged for receiving liquid refrigerant from the refrigerant liquefier 5, 6, 7 via a first evaporator expansion valve 10. The first evaporator 9 is arranged for cooling the first heat carrier medium by means of evaporation of the liquid refrigerant, and the first evaporator 9 is arranged to discharge evaporated, gaseous refrigerant to the compressor arrangement 2.

A heat carrier circuit 24 of the first heat exchanger 21 drives a flow of a first liquid heat carrier medium, such as water, in a counter flow by means of a pump 25. The heat carrier enters the heat exchanger 21 through a shell side inlet opening 28. After heat exchanging with the flow of liquid biomass inside the heat exchanger 21, the first liquid heat carrier medium exits through the shell side outlet opening 29 from which is passes onto the high pressure evaporator 9.

The heat exchange system 1 includes compressor 4 from which the gaseous, compressed refrigerant is passed to the gas cooler 5, where it is cooled by heat exchanging with the utilization heat carrier medium 13. The gaseous refrigerant passes from the gas cooler 5 to a receiver tank 6, also known as a flash tank via a receiver expansion valve 7, where the pressure is reduced so that most of the gaseous refrigerant is liquefied in the receiver tank 6. Surplus amounts of gaseous refrigerant from the receiver tank 7 passes to the high pressure compressor 4 via the flash valve 8.

In some embodiments, the heat exchange system is a transportable heat exchange system. List of reference numbers

1 Heat exchange system

2 Compressor arrangement

3 Low pressure compressor

4 High pressure compressor

5 Gas cooler

6 Receiver tank

7 Receiver expansion valve

8 Flash valve

9 High pressure evaporator (first evaporator)

10 High pressure evaporator expansion valve

11 Low pressure evaporator (second evaporator)

12 Low pressure evaporator expansion valve

13 Utilization heat carrier medium

14 Inlet utilization heat carrier medium

15 Outlet utilization heat carrier medium

16 Pump for utilization heat carrier medium

17 Incoming flow of liquid biomass

18 Inlet for incoming flow of liquid biomass

19 Outlet flow of liquid biomass

20 Pump for flow of liquid biomass

21 First heat exchanger

22 Front tubular heat exchanger of first heat exchanger

23 Back tubular heat exchanger of first heat exchanger

24 Heat carrier circuit of first heat exchanger

25 Pump for heat carrier of first heat exchanger

26 Tube side inlet opening

27 Tube side outlet opening

28 Shell side inlet opening

29 Shell side outlet opening 30 Inlet plenum

31 Outlet plenum

32 Cutter drive motor

33 Recirculation circuit of first heat exchanger

34 Recirculation pump of first heat exchanger

35 Second heat exchanger

36 Front tubular heat exchanger of second heat exchanger

37 Back tubular heat exchanger of second heat exchanger

38 Heat carrier circuit of second heat exchanger

39 Pump for heat carrier of second heat exchanger

40 Recirculation circuit of second heat exchanger

41 Recirculation pump of second heat exchanger

42 Shell

43 Tube

44 Tube bundle

45 Inlet tube sheet

46 Through-holes

47 Opening edge of through-hole

48 Plane surface

49 Cutter arrangement

50 Cutting edge

51 Solid matter

Claims

1. Method for heating a utilization heat carrier medium (13) by cooling an incoming flow of liquid biomass (17), the method comprising the steps of passing the flow of liquid biomass through a first heat exchanger (21) for transferring thermal energy from the flow of liquid biomass to a flow of a first liquid heat carrier medium, passing the flow of the first liquid heat carrier medium from the first heat exchanger to a first evaporator (9), where liquid refrigerant evaporates and thereby cools the first liquid heat carrier medium, passing the evaporated, gaseous refrigerant from the first evaporator to a compressor ((4), where the gaseous refrigerant is compressed, and passing the compressed gaseous refrigerant from the compressor to a refrigerant liquefier (5, 6, 7), wherein the gaseous refrigerant is cooled by transferring thermal energy to the utilization heat carrier medium and is liquefied.

2. Method according to claim 1, wherein the refrigerant liquefier is a condenser, in which the gaseous refrigerant is condensed to liquid refrigerant.

3. Method according to claim 1, wherein the refrigerant is carbon dioxide (CO2) and the refrigerant liquefier comprises a gas cooler (5), which is arranged for cooling the compressed refrigerant by heat exchanging with the utilization heat carrier medium and an intermediate pressure receiver tank (5) connected to an outlet of the gas cooler via a receiver expansion valve (7).

4. Method according to any of claims 1 to 3, wherein the first heat exchanger comprises a tubular heat exchanger (22, 23) having a shell (42) enclosing a tube bundle (44) extending between an inlet plenum (30) and an outlet plenum (31) of the tubular heat exchanger, the shell being provided with a shell side inlet opening (28) and a shell side outlet opening (29), and the inlet plenum being provided with a tube side inlet opening (26) and the outlet plenum being provided with a tube side outlet opening (27), and wherein the flow of liquid biomass passes from the tube side inlet opening to the tube side outlet opening, and the flow of the first liquid heat carrier medium passes from the shell side inlet opening to the shell side outlet opening.

5. Method according to any of claims 1 to 4, further comprising the step of recirculating a part of the flow of liquid biomass through the first heat exchanger from an outlet of the first heat exchanger (27) to an inlet of the first heat exchanger (26) by means of a first pump arrangement (34).

6. Method according to claim 5, wherein a flow rate of the combined flow of the incoming liquid biomass and the recirculated flow of liquid biomass through the first heat exchanger is at least 2 times the flow rate of the incoming flow of liquid biomass.

7. Method according to any of claims 1 to 6, further comprising the step of passing a flow of liquid biomass from an outlet of the first heat exchanger through a second heat exchanger (35) for transferring thermal energy from said flow of liquid biomass to a flow of a second liquid heat carrier medium, passing the flow of the second liquid heat carrier medium from the second heat exchanger to a second evaporator (11), where liquid refrigerant evaporates and thereby cools the second liquid heat carrier medium, passing the evaporated, gaseous refrigerant from the second evaporator and to a compressor (3), and passing the compressed, gaseous refrigerant from the compressor to the gas cooler (5), wherein the gaseous refrigerant is cooled by transferring thermal energy to the utilization heat carrier medium.

8. Method according to claim 7, wherein the second heat exchanger comprises a tubular heat exchanger having a shell enclosing a tube bundle extending between an inlet plenum and outlet plenum of the tubular heat exchanger, the shell being provided with a shell side inlet opening and a shell side outlet opening, and the inlet plenum being provided with a tube side inlet opening and the outlet plenum being provided with a tube side outlet opening, and wherein the flow of liquid biomass passes from the tube side inlet opening to the tube side outlet opening, and the flow of the second liquid heat carrier medium passes from the shell side inlet opening to the shell side outlet opening.

9. Method according to claim 7 or 8, wherein the boiling temperature of the liquid refrigerant in the second evaporator is at least 6° C lower than the boiling temperature of the liquid refrigerant in the first evaporator, such as at least 10° C lower.

10. Method according to any of claims 7 to 9, further comprising the step of recirculating a part of the flow of liquid biomass through the second heat exchanger from an outlet of the second heat exchanger to an inlet of the second heat exchanger by means of a second pump arrangement (41).

11. Method according to claim 10, wherein a flow rate of the combined flow of the incoming flow of liquid biomass and the recirculated flow of liquid biomass through the first heat exchanger is at least 2 times the flow rate of the incoming flow of liquid biomass.

12. Method according to any of claims 1-11, wherein the liquid biomass is a slurry with at least 2 to 10 % by weight of solid matter, such as 4 to 8%.

13. Method according to any of claims 1-12, wherein the liquid biomass is liquid manure.

14. Heat exchange system (1) for heating a utilization heat carrier medium by cooling an incoming flow of liquid biomass, the heat exchange system including a first heat exchanger for cooling the incoming flow of liquid biomass, a first heat carrier circuit arranged for providing a first liquid heat carrier medium to the first heat exchanger to transfer thermal energy from the incoming flow of liquid biomass, a compressor arrangement (2) for compressing a refrigerant in a gaseous state, a refrigerant liquefier arranged to receive the compressed refrigerant from the compressor arrangement, the refrigerant liquefier being arranged to heat the utilization heat carrier medium by heat exchange with the compressed refrigerant, which is thereby cooled, and liquefy the refrigerant, a first evaporator arranged for receiving liquid refrigerant from the refrigerant liquefier via a first evaporator expansion valve (10), the first evaporator being arranged for cooling the first heat carrier medium by means of evaporation of the liquid refrigerant, the first evaporator being arranged to discharge evaporated, gaseous refrigerant to the compressor arrangement.

15. Heat exchange system according to claim 14, wherein the refrigerant liquefier is a condenser, which is arranged for condensation of the gaseous refrigerant to liquid refrigerant.

16. Heat exchange system according to claim 14, which is arranged to use carbon dioxide (CO2) as the refrigerant, wherein the refrigerant liquefier comprises a gas cooler, which is arranged for cooling the compressed refrigerant by heat exchanging with the utilization heat carrier medium and an intermediate pressure receiver tank connected to an outlet of the gas cooler via a receiver expansion valve.

17. Heat exchange system according to any of claims 14 to 16, wherein the first heat exchanger comprises a first tubular heat exchanger having a shell enclosing a tube bundle extending between an inlet plenum and outlet plenum of the first tubular heat exchanger, the shell being provided with a shell side inlet opening and a shell side outlet opening, and the inlet plenum being provided with a tube side inlet opening and the outlet plenum being provided with a tube side outlet opening, and wherein the flow of liquid biomass is arranged to pass from the tube side inlet opening to the tube side outlet opening, and the flow of the first liquid heat carrier medium is arranged to pass from the shell side inlet opening to the shell side outlet opening.

18. Heat exchange system according to any of claims 14 to 17, further comprising a first pump arrangement arranged to recirculate a part of the flow of liquid biomass from a tube side outlet opening of the first heat exchanger to a tube side inlet opening of the first heat exchanger.

19. Heat exchange system according to any of claims 14 to 18, further comprising a second heat exchanger for cooling the incoming flow of liquid biomass, wherein the second heat exchanger is arranged to receive the flow of liquid biomass from an outlet of the first heat exchanger, a second heat carrier circuit arranged for providing a second liquid heat carrier medium to the second heat exchanger to transfer thermal energy from the incoming flow of liquid biomass, and a second evaporator (11) arranged for receiving liquid refrigerant from the intermediate pressure receiver tank via a second evaporator expansion valve (12), the second evaporator being arranged for cooling the second heat carrier medium by means of evaporation of the liquid refrigerant, the second evaporator being arranged to discharge evaporated, gaseous refrigerant to the compressor arrangement.

20. Heat exchange system according to claim 19, wherein the second heat exchanger comprises a tubular heat exchanger having a shell enclosing a tube bundle extending between an inlet plenum and outlet plenum of the tubular heat exchanger, the shell being provided with a shell side inlet opening and a shell side outlet opening, and the inlet plenum being provided with a tube side inlet opening and the outlet plenum being provided with a tube side outlet opening, and wherein the flow of liquid biomass is arranged to pass from the tube side inlet opening to the tube side outlet opening, and the flow of the second liquid heat carrier medium is arranged to pass from the shell side inlet opening to the shell side outlet opening.

21. Heat exchange system according to claim 19 or 20, wherein the first evaporator expansion valve and the second evaporator expansion valve are adjusted so that the boiling temperature of the liquid refrigerant in the second evaporator is at least 6° C lower than the boiling temperature of the liquid refrigerant in the first evaporator, such as at least 10° C lower.

22. Heat exchange system according to any of claims 19 to 21, further comprising a second pump arrangement arranged to recirculate a part of the flow of liquid biomass from an outlet of the second heat exchanger to an inlet of the second heat exchanger.

23. Tubular heat exchanger comprising a shell enclosing a tube bundle extending between an inlet plenum and outlet plenum of the heat exchanger, the shell being provided with a shell side inlet opening and a shell side outlet opening, and the inlet plenum being provided with a tube side inlet opening and the outlet plenum being provided with a tube side outlet opening, the heat exchanger comprising an inlet tube sheet (45) with a plurality of through-holes (46) accommodating inlet ends of the tubes (43) of the tube bundle, the inlet tube sheet comprising a plane surface (48) facing the inlet plenum, a cutter arrangement (49) comprising at least one cutting edge (50) within the inlet plenum and cutter drive means (32) arranged to drive the at least one cutting edge to sweep across the inlet tube sheet in close proximity to the plane surface of the inlet tube sheet so that an opening edge (47) of each of the through-holes may be swept by at least one of the cutting edges so as to cut any possible solid matter (51) clogging the through-holes of the inlet tube sheet.

24. Tubular heat exchanger according to claim 23, wherein the tubes of the tube bundle extend substantially straight from the inlet plenum to the outlet plenum.

25. Tubular heat exchanger according to claim 23 or 24, wherein the inner opening area of each of the tubes of the tube bundle is in the range of 170 mm² to 1400 mm², preferably in the range of 300 mm² to 700 mm².

26. Tubular heat exchanger according to any of claims 23 to 25, wherein the inner diameter of each of the tubes of the tube bundle is in the range of 15 mm to 40 mm, preferably in the range of 20 mm to 30 mm.

27. Tubular heat exchanger according to any of claims 23 to 26, wherein the bundle of tubes comprises in the range of 30 to 150 tubes.

28. Tubular heat exchanger according to any of claims 23 to 27, wherein the extent of the tubes of the tube bundle is in the range of 3 meter to 12 meter.

29. Use of a tubular heat exchanger according to any of claims 23-28, for heat exchanging between a slurry containing at least 2 to 10 % by weight of solid matter, such as 4 to 8% and a heat carrier medium, and wherein the slurry passes from the tube side inlet opening to the tube side outlet opening, and the flow of the heat carrier medium passes from the shell side inlet opening to the shell side outlet opening.

30. Use according to claim 29, wherein the slurry is a liquid biomass, preferably wherein the slurry is liquid manure.

31. Method according to any of claims 2-13, wherein the tubular heat exchanger of the first heat exchanger is a tubular heat exchanger according to any of claims 23-28.

32. Method according to any of claims 8-13, wherein the tubular heat exchanger of the second heat exchanger is a tubular heat exchanger according to any of claims 23- 28.

33. Heat exchange system according to any of claims 17-22, wherein the tubular heat exchanger of the first heat exchanger is a tubular heat exchanger according to any of claims 23-28.

34. Heat exchange system according to any of claims 21-22, wherein the tubular heat exchanger of the second heat exchanger is a tubular heat exchanger according to any of claims 23-28.

35. Heat exchange system according to any of claims 14-22, wherein the heat exchange system comprises a plurality of tubes, the heat exchange system being configured to allow the liquid biomass to flow through the plurality of tubes.

36. Heat exchange system according to claim 35, wherein the heat exchange system is configured to allow the liquid heat carrier medium to flow around the plurality of tubes.

37. Method according to any of claims 1-13, wherein passing the flow of liquid biomass through a first heat exchanger (21) for transferring thermal energy from the flow of liquid biomass to a flow of a first liquid heat carrier medium, include passing the flow of liquid biomass through a plurality of tubes.

38. Method according to claim 37, wherein the first liquid heat carrier medium flows around the plurality of tubes.