Hydrothermal carbonisation method

Abstract

The invention relates to a method for hydrothermal carbonisation of biomass containing organic matter, the method comprising: injecting the biomass, a heat transfer fluid and a reagent into a reactor (1), circulating a mixture consisting of the biomass, the heat transfer fluid and the reagent under specific pressure and temperature conditions for transforming the organic matter by hydrothermal carbonisation. The invention consists in: 1) determining the production rate of the emitted gas T.sub.e during the hydrothermal carbonisation reaction; 2) comparing the determined production rate of the emitted gas T.sub.e with a predefined value for the set gas production rate T.sub.c, and 3) adjusting at least one of the reaction control parameters chosen from among the temperature within the reactor (1), the quantity of injected reactant, and the residence time in the reactor in order to adjust the production rate of the emitted gas T.sub.e, such that the value of said production rate of the emitted gas Te tends to be equal to the value of the set gas production rate T.sub.c. The invention is applicable to treatment of biomass containing organic matter.

Claims

1. A method for the hydrothermal carbonisation of a biomass containing organic matter, the method comprising: injecting the biomass, a heat transfer fluid and a reagent into a reactor; circulating in the reactor a mixture consisting of the biomass, the heat transfer fluid, and the reagent; subjecting the mixture to specific pressure and temperature conditions in the reactor such that the organic matter in the biomass undergoes a hydrothermal carbonisation reaction in the reactor and the biomass is transformed into a carbonized biomass, determining an emitted gas production rate Te in the reactor during the hydrothermal carbonisation reaction; comparing the emitted gas production rate Te in the reactor to a predefined setpoint gas production rate Tc; and adjusting at least one reaction drive parameter such that the emitted gas production rate Te in the reactor tends to be equal to or to approach the predefined setpoint gas production rate Tc, wherein the at least one reaction drive parameter is selected from the group consisting of a temperature in the reactor, an amount of the reagent injected into the reactor, and a residence time of the biomass in the reactor.

2. The method according to claim 1, wherein the method is carried out continuously, and wherein the method further comprises: measuring a flow rate of non-condensable gases emitted from an outlet of the reactor during the hydrothermal carbonisation reaction; and calculating the emitted gas production rate Te based on the measurement of the flow rate of non-condensable gases emitted from the outlet of the reactor.

3. The method according to claim 2, further comprising: prior to or during the hydrothermal carbonisation reaction, defining the predefined setpoint gas production rate Tc as a function of a desired dryness of the biomass after the biomass has been subjected to a dehydration process performed subsequent to the hydrothermal carbonisation reaction.

4. The method according to claim 2, further comprising: prior to measuring the flow rate of the non-condensable gases emitted from the outlet of the reactor, passing the non-condensable gases through a condenser or other dehydration means.

5. The method according to one of claim 2, further comprising: adjusting the temperature in the reactor during the hydrothermal carbonisation reaction by modifying a temperature of the heat transfer fluid injected into the reactor; and/or adjusting the residence time of the biomass in the reactor during the hydrothermal carbonisation reaction by modifying a flow rate of the biomass injected into the reactor.

6. The method according to claim 1, wherein the reactor is sealed during the hydrothermal carbonisation reaction and the method is carried out in a batch mode, and wherein the method further comprises: cooling the reactor to a set target temperature; after cooling the reactor to the set target temperature, measuring a pressure prevailing in the reactor at the set target temperature; and calculating the emitted gas production rate Te based on the measurement of the pressure prevailing in the reactor at the set target temperature.

7. The method according to claim 6, further comprising: adjusting the residence time of the biomass in the reactor based on a reaction time of a previous hydrothermal carbonisation reaction carried out in the reactor.

8. The method according to claim 6, further comprising: cooling the reactor to the set target temperature by heat exchange with another heat transfer fluid through a wall of the reactor or a coil within the reactor.

9. The method according to claim 1, further comprising: increasing or decreasing the amount of the reagent injected into the reactor such that the emitted gas production rate Te tends to be equal to or to approach the predefined setpoint gas production rate Tc.

10. A method for dehydrating biomass comprising: injecting the biomass, a heat transfer fluid, and a reagent into a reactor: circulating in the reactor a mixture consisting of the biomass, the heat transfer fluid, and the reagent; subjecting the mixture to specific pressure and temperature conditions in the reactor such that organic matter in the biomass undergoes a hydrothermal carbonisation reaction in the reactor and the biomass is transformed into a carbonized biomass, determining an emitted gas production rate Te in the reactor during the hydrothermal carbonisation reaction; comparing the emitted gas production rate Te in the reactor to a predefined setpoint gas production rate Tc; adjusting at least one reaction drive parameter such that the emitted gas production rate Te in the reactor tends to be equal to or to approach the predefined setpoint gas production rate Tc, wherein the at least one reaction drive parameter is selected from the group consisting of a temperature in the reactor, an amount of the reagent injected into the reactor, and a residence time of the biomass in the reactor; and after the hydrothermal carbonisation reaction, mechanically dehydrating the carbonized biomass to form a dehydrated biomass.

11. The method according to claim 2, wherein the emitted gas production rate Te is determined during the hydrothermal carbonisation reaction in the reactor, the emitted gas production rate Te is compared to the predefined setpoint gas production rate Tc during the hydrothermal carbonisation reaction in the reactor, and the at least one reaction drive parameter is adjusted in real time during the hydrothermal carbonisation reaction in the reactor.

12. The method according to claim 1, wherein the Te is at least partly attributable to gases emitted from the organic matter during the hydrothermal carbonisation reaction.

13. The method according to claim 1, wherein, during the hydrothermal carbonisation reaction, the organic matter undergoes hydrolysis and then decarboxylation and dehydration.

14. The method according to claim 1, wherein the reagent comprises a catalyst configured to initiate the hydrothermal carbonisation reaction.

15. The method according to claim 14, wherein the reagent comprises at least one acid catalyst selected from the group consisting of sulphuric acid, linear C.sub.1-C.sub.6 carboxylic acids, and branched C.sub.1-C.sub.6 carboxylic acids, and wherein the linear C.sub.1-C.sub.6 carboxylic acids and the branched C.sub.1-C.sub.6 carboxylic acids are mono-, di-, or tricarboxylic acids.

16. The method according to claim 6, wherein the set target temperature is 75 degrees Celsius, and wherein the method further comprises: calculating an estimated final dryness of the biomass after the carbonized biomass has been subjected to a subsequent dehydration process according to the following equation:
Ln P=f(Ln(TS/(0.0001TS)), where f(x)=03226*x+10.8734, P is the pressure prevailing in the reactor at the set target temperature in Pa, and TS is the final dryness of the biomass in g/L.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and features of the invention will become apparent from the detailed description of non-limiting implementations and embodiments, and the following figures in which:

(2) FIG. 1 is a schematic view of one embodiment of a continuous hydrothermal biomass carbonisation facility according to the invention.

(3) FIG. 2 is a graphical representation which highlights the variation in dehydration performance and in the flow rate of reaction gas and the amount of reagent for a facility for implementing a method carried out continuously; and

(4) FIG. 3 is a graphical representation of a mathematical relationship between the dryness of the final cake and the final pressure at 75 C. of an HTC reactor implementing a batch carbonisation method.

DETAILED DESCRIPTION

(5) The device represented in FIG. 1 comprises a reactor 1 arranged to implement a hydrothermal reaction. The following description will focus on embodiments with sludge, but could be implemented with other types of biomass, such as organic waste.

(6) This hydrothermal reaction comprises the following steps: a sludge injection step in which sludge is injected into the reactor 1 through a first inlet 11, a step of injecting steam as a heat transfer fluid, in which steam is injected into the reactor 1 via a second inlet 12, the second inlet 12 preferably being distinct from the first inlet 11, a circulation step in which a mixture consisting of the sludge and the steam injected into the reactor 1 is circulated within the reactor 1, a step of continuously extracting at least part of the mixture contained in the reactor 1 through a sludge outlet 14.

(7) The sludge, containing organic matter, comes for example from a hopper 2 to be conveyed into a duct (inlet 11 of the device), for example by gravity. The sludge arriving in the duct typically has a dryness in solids content by weight of between 10 and 30%, typically between 18 and 24%.

(8) The internal space of the reactor 1 is further configured to form a degassing volume 13 in an upper part of this internal space (that is a part of higher altitude than other parts of this internal space). In this degassing volume 13, the mixture does not circulate. This degassing volume 13 is arranged to recover gaseous non-condensables and especially CO.sub.2.

(9) The reactor 1 is also provided with a non-condensables outlet connecting the degassing volume 13 to a discharge duct 15 for possible subsequent treatment. This non-condensables outlet is driven by a valve 16 to monitor pressure in the reactor 1.

(10) At this degassing volume or duct 15, means of measuring the gas flow rate 2, such as a flow meter 18, are installed, for example downstream of the duct 15, preferably after a condenser 17, and thus make it possible to measure the emitted gas flow rate, De, during the reaction.

(11) During the implementation of the method according to the invention, the following steps are carried out:

(12) During a preliminary step, referred to as step 0, a setpoint flow rate value D.sub.C is chosen as a function of the desired dryness of the dehydrated biomass and this predetermined value of the gas flow rate D.sub.c (setpoint flow rate) is entered into the monitoring means of the facility, and then the HTC reaction, and preferably an ultradehydration, as seen above, is implemented.

(13) During the hydrothermal reaction, an emitted gas flow rate D.sub.e is measured, preferably at regular intervals or continuously. The measurement of the emitted gas flow rate is processed by the monitoring and control means, with which the value of the emitted gas flow rate D.sub.e is compared with that of the setpoint gas flow rate D.sub.c (+/X %). Depending on the difference noted between the values of the emitted gas flow rate D.sub.e and the setpoint gas flow rate D.sub.c, at least one of the three parameters such as the temperature T within the reactor 1 is adjusted by monitoring the heat transfer fluid inlet 12, and/or preferably the amount of reagent injected into the reactor 1 from a reagent tank 3 and/or the residence time in the HTC reactor 1.

(14) By regulating at least one of these parameters, this value of De can thus be modified so that it is equal to D.sub.C, or at least approaches D.sub.C. This regulation step is repeated throughout the hydrothermal reaction (feedback loop), subsequent measurements making it possible to monitor that the emitted gas flow rate D.sub.e corresponds to the setpoint gas flow rate D.sub.c or to adjust the drive parameters until these two emitted gas flow rates D.sub.e and setpoint gas flow rate D.sub.c correspond to each other.

(15) As could have been noticed, stability of the quality of the sludge entering the facility has shown a clear relationship between dehydrating performance and amount of reagent injected. This reagent is a catalyst for the HTC reaction, especially an acid catalyst, chosen from citric acid, formic acid, sulphuric acid and acetic acid.

(16) FIG. 2 is a graphical representation which highlights the variation of the dehydration performance and the flow rate of non-condensable gases (noted NC) emitted by the reactor in continuous operation within the scope of the implementation of a continuous hydrothermal carbonisation method, in which the amount of injection of the reagent is adjustable while the other parameters are fixed such as a constant reaction time of 2 h30, a constant reaction temperature of 185 C., and a single type of sludge treated.

(17) In FIG. 3, a mathematical relationship between the dryness of the final cake and the final pressure at 75 C. of a 3 litres HTC micropilot operating in a batch tank is represented.

(18) As the HTC micro-pilot is completely sealed, the demonstration of reaction gas production is revealed by the final pressure in the reactor. As the test protocol is fixed, the initial amount of product is constant and the initial pressure is equal to the ambient pressure. Any higher pressure after the reaction is the result of a gas residing in the reactor whose saturation pressure is much higher than that of water.

(19) The resulting relationship can be represented as follows: Ln (1/P)=f (Ln ((100TS)/TS)) with f(x)=0.3226*x+1.6631 with: P representing the final pressure at 75 C. in the hydrothermal carbonisation reactor (in bar), which corresponds to the gas production by the HTC reaction, and TS representing the final dryness of the cake in % of Total Solids (expressed in %).

(20) This formula is equivalent to the following:
Ln P=f(Ln(TS/(0.0001TS)) with f(x)03226*x10.8734with: P: representing the final pressure at 75 C. in the hydrothermal carbonisation reactor (in Pa), which corresponds to the gas production by the HTC reaction, and TS: final dryness of the cake in g/L.

(21) The method according to the invention thus allows an adjustment of at least one functional parameter in real time of a continuous hydrothermal carbonisation method and an adjustment of at least one functional parameter from one batch to another for a batch hydrothermal carbonisation method. The adjustment time of a method according to the invention is thus optimised.