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 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, wherein (a) the emitted gas production rate Te during the hydrothermal carbonisation reaction is determined; (b) the emitted gas production rate Te determined is compared with a value of predefined setpoint gas production rate Te, and (c) at least one of the reaction drive parameters selected from the temperature within the reactor, the amount of reagent injected, and the residence time in the reactor is adjusted, to adjust the emitted gas production rate Te, so that the value of this emitted gas production rate Te tends to be equal to the value of the setpoint gas production rate Tc.

2. The method according to claim 1, wherein the method is carried out continuously, and the emitted gas production rate Te is determined by measuring the flow rate of non-condensable gases emitted at the outlet of the reactor.

3. The method according to claim 2, wherein, during a step prior to the implementation of the hydrothermal carbonisation reaction or upon activating the HTC method, the setpoint gas flow rate value (D.sub.c) is predefined as a function of the desired dryness of the final product.

4. The method according to one of claim 2, wherein the measurement of the flow rate of non-condensable emitted gas at the outlet of the reactor is carried out after the emitted gas has passed through condensation or dehydration means.

5. The method according to one of claim 2, wherein the temperature within the reactor is adjusted by monitoring the temperature of the heat transfer fluid, and/or the residence time in the reactor is adjusted by monitoring the incoming biomass flow rate.

6. The method according to claim 1, wherein the method is carried out in a batch mode, and the emitted gas production rate is determined by measuring the pressure prevailing within the reactor at the end of the carbonisation and cooling cycle at a set target temperature.

7. The method according to claim 6, wherein the residence time in the reactor is adjusted by monitoring the reaction time.

8. The method according to claim 6, wherein the temperature within the reactor is adjusted by cooling the sealed reactor by exchange with a heat transfer fluid through the wall of the reactor or a coil.

9. The method according to claim 1, wherein the amount of injected reagent is regulated, namely increased and/or decreased, depending on the emitted gas production rate determined.

10. A method for dehydrating biomass comprising hydrothermal carbonisation of the biomass, resulting in carbonised sludge, and mechanically dehydrating the carbonised sludge; injecting the biomass, a heat transfer fluid and a reagent into a reactor, 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, wherein (a) the emitted gas production rate Te during the hydrothermal carbonisation reaction is determined; (b) the emitted gas production rate Te determined is compared with a value of predefined setpoint gas production rate Te, and (c) at least one of the reaction drive parameters selected from the temperature within the reactor, the amount of reagent injected, and the residence time in the reactor is adjusted, to adjust the emitted gas production rate Te, so that the value of this emitted gas production rate Te tends to be equal to the value of the setpoint gas production rate Tc.

11. A facility for the hydrothermal carbonisation of biomass containing organic matter, comprising a reactor, a first inlet feeding the biomass into the reactor, a second inlet injecting a heat transfer fluid into the reactor, and an injector injecting a reagent into the reactor, a circulator circulating a mixture comprising the biomass, the heat transfer fluid and the reagent under specific pressure and temperature conditions for transforming the organic matter, a sensor determining the emitted gas production rate Te; comparing the emitted gas production rate Te determined with a setpoint gas production rate Tc, and a sensor monitoring and controlling the facility making it possible to adjust at least one of the reaction drive parameters, which are the temperature within the reactor, the amount of reagent injected, and the residence time in the reactor, in order to adjust the emitted gas production rate Te, so that the value of this emitted gas production rate tends to be equal to the value of the setpoint gas production rate.

12. The facility according to claim 11, wherein the facility is adapted to a continuously operating method, the facility outputting emitted gas into the reactor and determining the emitted gas production rate comprise means for measuring the emitted gas flow rate De such as a flow meter at the outlet of the reactor.

13. The facility according to claim 12, wherein condensation or dehydration means are provided upstream of the means for measuring the emitted gas flow rate De in a continuous method.

14. The facility according to claim 11, wherein the facility is adapted to a batch operation method, and the sensor measuring the emitted gas production rate Te comprising measuring pressure in the reactor at the end of the cycle.

15. The facility of claim 11, further comprising cooling by indirect contact with the heat transfer fluid in the reactor for a batch method.

16. The facility according to claim 11, wherein the facility comprises a press downstream of the reactor, the press comprising at least a biomass inlet, a biomass outlet, the biomass inlet of the press being in fluid connection with the carbonised sludge outlet of the reactor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0082] 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:

[0083] FIG. 1 is a schematic view of one embodiment of a continuous hydrothermal biomass carbonisation facility according to the invention.

[0084] 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

[0085] 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

[0086] 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.

[0087] This hydrothermal reaction comprises the following steps: [0088] a sludge injection step in which sludge is injected into the reactor 1 through a first inlet 11, [0089] 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, [0090] 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, [0091] a step of continuously extracting at least part of the mixture contained in the reactor 1 through a sludge outlet 14.

[0092] 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%.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] During the implementation of the method according to the invention, the following steps are carried out:

[0097] 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.

[0098] 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 r 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] The resulting relationship can be represented as follows: Ln (1/P)=f (Ln ((100−TS)/TS)) with f(x)=−0.3226*x+1.6631 with: [0105] 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 [0106] TS representing the final dryness of the cake in % of Total Solids (expressed in %).

[0107] This formula is equivalent to the following:

Ln P=f(Ln(TS/(0.0001−TS)) with f(x)−03226*x10.8734with: [0108] 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 [0109] TS: final dryness of the cake in g/L.

[0110] 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.