Apparatus and method for converting biomass

Abstract

It relates to a method and an apparatus for converting biomass into hydrothermal charcoal.

Description

[0001] describe

[0002] The present invention relates to an apparatus and method for converting biomass into hydrothermal charcoal. More particularly, it relates to an apparatus and method for efficiently converting biomass into hydrothermal charcoal that is a usable material for various uses.

[0003] As is known, biomass can be converted into hydrochar, a solid material with a high carbon content resulting from the conversion of biomass by thermochemical methods in the presence of pressurized hot water.

[0004] The above-mentioned materials can be effectively utilized in various ways: such materials are used, for example, as solid fuels, catalysts or soil conditioners.

[0005] Typically, the conversion of biomass into hydrothermal charcoal takes place in a reactor in which a quantity of biomass is placed, with a water content greater than 60% and / or sufficient water content to ensure that the biomass is completely immersed in water. This biomass is introduced and maintained for a time interval, typically but not exclusively between 3 and 8 hours, at a temperature between 180 and 250° C. and at a pressure higher than the vapor tension of water at these temperatures (thus, typically between 10 and 50 bars), depending on the chemical characteristics of the biomass.

[0006] When unloading the material thus obtained, it is necessary to return the system to ambient temperature, for example by pressure reduction, wherein a rapid drop in temperature ensues, precisely from the process temperature to about 100° C., leading to partial evaporation of the water.

[0007] Therefore, the main problem of the prior art relates to the large energy losses, since the energy spent to bring the biomass inside the reactor to the required temperature is then lost when unloading.

[0008] It is an object of the present invention to provide an apparatus for converting biomass into hydrothermal charcoal which operates efficiently.

[0009] A further object of the present invention is to obtain a plant for converting biomass into hydrochar, in which the energy losses in the unloading phase of the hydrochar obtained are significantly reduced.

[0010] According to the present invention, all of the above objects and advantages are achieved by a method for converting biomass into hydrothermal charcoal by means of an apparatus comprising:

[0011] - a first reactor, a second reactor, a third reactor, into which biomass can be loaded from the outside and hydrothermal char can be unloaded from the device to the outside;

[0012] - a fourth reactor, a fifth reactor and a sixth reactor, in which the conversion of biomass into hydrochar can be carried out at a process temperature between 180° C. and 250° C., at a process pressure corresponding to or above the vapor tension of water at said process temperature, i.e. between 10 and 50 bars, for a time span equal to a reaction time between 3 and 8 hours;

[0013] - a heat exchanger, via which the first reactor, the second reactor, the third reactor are indiscriminately connected to the fourth reactor, the fifth reactor and the sixth reactor.

[0014] In the apparatus, the first reactor, the second reactor, the third reactor, the fourth reactor, the fifth reactor and the sixth reactor are also directly connected to each other.

[0015] In particular, the method according to the invention provides the following in an initial state:

[0016] - the first reactor is filled with hydrothermal char, process water and gases produced during the reaction (from now on these three substances as a whole are defined as "process products") and is pressurized at the process pressure and at an unloading temperature between 30°C and 50°C;

[0017] - the second reactor is filled with biomass and water or partly or completely recycled liquid formed downstream in the process (from now on these substances as a whole are defined as "feedstock") and pressurized at the process pressure;

[0018] - the third reactor is empty and pressurized at the process pressure;

[0019] - said fourth reactor is filled with process product, pressurized at said process pressure and at reaction temperature;

[0020] - the fifth reactor is empty and pressurized at process pressure;

[0021] - the sixth reactor is filled with feedstock, pressurized at the process temperature and partially heated at a temperature between 160° C. and 210° C.;

[0022] The method provides a first loop wherein, simultaneously:

[0023] - the first reactor is successively isolated from the rest of the plant, depressurized at atmospheric pressure, emptied of the process products it contains, loaded with feedstock and, finally, pressurized at the process pressure;

[0024] - the process product contained in the fourth reactor is transferred to the third reactor through the heat exchanger in countercurrent with the feedstock transferred from the second reactor to the fifth reactor through the heat exchanger, so as to transfer heat from the process product to the feedstock;

[0025] - the air contained in the third reactor and the fifth reactor is transferred to the second reactor and the fourth reactor respectively;

[0026] - In the sixth reactor, the feedstock is brought to the reaction temperature, wherein reactions and conversion into hydrothermal charcoal and other process products take place.

[0027] Advantageously, the method according to the invention can provide the following: at the end of the first cycle, a second cycle is performed, wherein, simultaneously, the operation of the first reactor during the first cycle is performed by the third reactor, the operation of the second reactor during the first cycle is performed by the first reactor, the operation of the third reactor during the first cycle is performed by the second reactor, the operation of the fourth reactor during the first cycle is performed by the sixth reactor, the operation of the fifth reactor during the first cycle is performed by the fourth reactor and the operation of the sixth reactor during the first cycle is performed by the fifth reactor.

[0028] Furthermore, the method according to the present invention may provide the following: at the end of the second cycle, a third cycle is performed, wherein, simultaneously, the operation of the first reactor during the first cycle is performed by the second reactor, the operation of the second reactor during the first cycle is performed by the third reactor, the operation of the third reactor during the first cycle is performed by the first reactor, the operation of the fourth reactor during the first cycle is performed by the fifth reactor, the operation of the fifth reactor during the first cycle is performed by the sixth reactor and the operation of the sixth reactor during the first cycle is performed by the fourth reactor.

[0029] By using the method according to the present invention, hydrothermal charcoal and other process products can be obtained more efficiently than in the prior art.

[0030] This efficiency is obtained by decoupling the three characteristic times of the thermochemical process of biomass conversion in the presence of pressurized hot water, namely:

[0031] 1. Time for feeding raw materials and unloading process products (time 1);

[0032] 2. Process time (usually but not exclusively 3 to 8 hours) (Time 2);

[0033] 3. Heat exchange time between input raw materials and output process products (time 3).

[0034] In fact, with the method according to the invention, continuous operation of the device can be ensured regardless of the process time (time 2) in terms of feeding and unloading (time 1) and regardless of the time it takes for the heat exchanger to complete a countercurrent heat exchange (time 3).

[0035] Therefore, the high heat exchange efficiency obtainable by decoupling the heat exchange time (time 3) from the other two characteristic times of the system involves a significant reduction in operating costs directly related to the supply of thermal energy required to bring the feedstock from ambient temperature to process temperature in each cycle.

[0036] In this way, the heat exchanger has all the time required for complete heat exchange (time 3), with minimal impact on both reaction time (time 2) and loading / unloading time (time 1).

[0037] Compared to conventional state-of-the-art solutions for implementing thermochemical processes for converting biomass, the process according to the invention allows to obtain more favorable operating costs and less energy waste.

[0038] Advantageously, in the method according to the invention, the variation of the level in the device can be managed by means of an expansion vessel.

[0039] The objects and advantages of the present invention are also achieved by an apparatus for converting biomass into hydrothermal charcoal, the apparatus comprising:

[0040] - a first reactor, a second reactor, a third reactor, into which raw materials can be loaded from the outside, and process products can be unloaded from the device to the outside;

[0041] - a fourth reactor, a fifth reactor and a sixth reactor in which the conversion of biomass into process products can be carried out at a process temperature between 180° C. and 250° C., at a process pressure corresponding to or above the vapor tension of water at said process temperature, i.e. between 10 bar and 50 bar, for a time span equal to a reaction time of typically, but not exclusively, between 3 and 8 hours;

[0042] - a heat exchanger, through which the first reactor, the second reactor, the third reactor are indiscriminately connected to the fourth reactor, the fifth reactor and the sixth reactor;

[0043] The first reactor, the second reactor, the third reactor, the fourth reactor, the fifth reactor and the sixth reactor are also directly connected to each other.

[0044] Furthermore, the apparatus according to the present invention may comprise a loading / unloading pump suitable for loading feedstock into or unloading the process product from at least one of the first reactor, the second reactor, the third reactor, the fourth reactor, the fifth reactor and the sixth reactor.

[0045] Advantageously, a feed pump may be included, which is suitable for pressurizing at least one of the first reactor, the second reactor, the third reactor, the fourth reactor, the fifth reactor and the sixth reactor.

[0046] Furthermore, in the device according to the invention an expansion vessel may be comprised, which is suitable for managing level variations within said device.

[0047] Advantageously, at least one of the first reactor, the second reactor and the third reactor may be a tank to reduce the cost of the entire device.

[0048] Further characteristics and details of the invention will be better understood from the following detailed description provided by way of non-limiting examples and the accompanying drawings, in which:

[0049] Figure 1 is a schematic diagram of an apparatus for converting biomass into hydrothermal charcoal, the apparatus being made in accordance with the present invention;

[0050] Figure 2 It is a display Figure 1 A diagram of the operation of the device;

[0051] Figure 3 is a summary subtitle, explaining the existence of Figure 2 The symbols in the figure.

[0052] Referring to the drawings, reference numeral 10 denotes an apparatus for converting biomass into hydrothermal charcoal.

[0053] The plant 10 according to the invention comprises six reactors 12 , 14 , 16 , 18 , 20 , 22 which have the same capacity and are connected to one another and to a heat exchanger 24 and to a gas (air) expansion vessel 26 .

[0054] In particular, the apparatus 10 includes a first reactor 12, a second reactor 14 and a third reactor 16 (in which loading and unloading of raw materials and process products are respectively carried out between the apparatus and the outside) and a fourth reactor 18, a fifth reactor 20 and a sixth reactor 22 (in which reactions are carried out, i.e., conversion of raw materials into process products).

[0055] In the fourth reactor 18, the fifth reactor 20 and the sixth reactor 22, the reaction conditions of the materials are the same as those provided by the prior art, wherein the production is not carried out in a continuous mode, namely a temperature of 220°C, a pressure of 20 bar and a reaction time of about 3 hours.

[0056] Of course, the process temperature may differ from 220°C, i.e. the temperature may be between 180°C and 250°C, the pressure may differ from 20 bar, but in any case it must correspond to or be higher than the vapour tension of water at the process temperature, and the time may be longer than 3 hours.

[0057] The heat exchanger 24 operates in countercurrent and at high efficiency.

[0058] The entire apparatus 10, ie all six reactors 12, 14, 16, 18, 20, 22 and the heat exchanger 24, is always kept at the reaction pressure, ie a pressure of 20 bar.

[0059] Any level changes are managed via a gas (air) expansion vessel 26 .

[0060] The loading and unloading of materials, raw materials and process products are carried out in isolated single reactors at atmospheric pressure, and in particular, the first reactor 12, the second reactor 14 and the third reactor 16 according to the embodiment mode of the present invention are reactors responsible for loading and unloading materials.

[0061] In the absence of gas (air), repressurization is performed solely by the feed pump 32, thus compressing the fluid only.

[0062] Generally speaking, the operating procedure of the apparatus 10 provides a series of continuous cycles with each cycle lasting 3 hours.

[0063] However, the reaction time may differ from 3 hours and is determined according to the type of starting materials and / or the chemical-physical characteristics of the process product to be obtained, ie usually but not exclusively from 3 to 8 hours.

[0064] In one of the last three reactors, and in particular by rotating the fourth reactor 18, the fifth reactor 20 and the sixth reactor 22, the reaction of converting the biomass into hydrothermal char occurs.

[0065] In particular, in each of the reactors 18, 20, 22, in the first stage of the cycle, the reaction and subsequent conversion of the biomass into hydrothermal char occurs by rotation within a limited time, the material reaches a nominal temperature, i.e., 220°C, the material leaves the heat exchanger 24, and the reaction then occurs.

[0066] In one of the first three reactors, and in particular by rotating the first reactor 12, the second reactor 14 and the third reactor 16, materials are unloaded and loaded with the outside, in particular raw materials are loaded and process products are unloaded.

[0067] In particular, each of the reactors 12, 14, 16 in which unloading and loading is performed by rotation is first isolated from the rest of the plant 10 and its internal pressure is reduced until it is equal to atmospheric pressure. First, the reactor is unloaded with process products, and then loaded with feedstock. The loaded material is brought to the nominal reaction pressure, i.e. 20 bar, and finally the reactor in question is put back into communication with the rest of the plant 10.

[0068] The remaining four reactors are heat exchanged by transferring heat from the mixture consisting of the process products at the end of the reaction (i.e. at the end of the cycle) to the incoming feedstock (i.e. at the beginning of the cycle). The reactors are emptied and filled two-to-two by material transfer at isobaric pressure (i.e. nominal reaction pressure of 20 bar).

[0069] Now, refer to Figure 2 and Figure 3 The operation of the apparatus 10 in the first cycle is described in detail.

[0070] In the initial state of the first cycle, the first reactor 12 is filled with the process product to be unloaded and pressurized. In other words, the first reactor 12 is loaded with the process product at a temperature of 40° C. and a pressure of 20 bar.

[0071] The second reactor 14 is filled with feedstock and pressurized and is therefore at a pressure of 20 bar.

[0072] The third reactor 16 is empty and pressurized, and is therefore at a pressure of 20 bar.

[0073] The fourth reactor 18 is filled with process product at the end of the reaction and is therefore at a temperature of 220° C. and a pressure of 20 bar.

[0074] The fifth reactor 20 is empty and pressurized, and is therefore at a pressure of 20 bar.

[0075] The sixth reactor 22 is filled with feedstock, partially heated to a temperature of about 200° C., and pressurized and thus at a pressure of 20 bar.

[0076] In the first cycle, the following operations are performed.

[0077] The process product contained in the fourth reactor 18 passes in countercurrent through the interior of the heat exchanger 24 to transfer heat to the feedstock contained in the second reactor 14 ; in this way, the process product is transferred to the third reactor 16 and the feedstock is transferred to the fifth reactor 20 .

[0078] The pressure inside the five reactors 14, 16, 18, 20, 22 (ie, all reactors except the first reactor 12) is kept constant, ie, 20 bar, and the six reactors are connected in parallel.

[0079] The air contained in the previously empty third reactor 16 and fifth reactor 20 is vented into the second reactor 14 and fourth reactor 18, respectively, which are emptied of their respective materials.

[0080] The reaction of the raw material takes place in the sixth reactor 22; in other words, the raw material, which is initially partially heated, is brought to the reaction temperature, namely to 220°C.

[0081] Unloading and loading of material occurs in the first reactor 12 .

[0082] Specifically, the first reactor 12 is isolated from the rest of the plant 10 and subsequently depressurized to atmospheric pressure via the first valve 28. The process product is unloaded from the first reactor 12 at atmospheric pressure via the first loading / unloading pump 30. The estimated time required for the unloading operation is approximately equal to half the cycle time, i.e. about 1.5 hours.

[0083] Subsequently, the feedstock is loaded at atmospheric pressure into the same first reactor 12 by means of a first loading / unloading pump 30. The estimated time required for the loading operation is approximately equal to half of the cycle time, ie, about 1.5 hours.

[0084] The first reactor 12 is then pressurized by means of the feed pump 32 at the nominal pressure of the apparatus 10 , ie to 20 bar.

[0085] Finally, the first reactor 12 is reconnected to the apparatus 10 .

[0086] At the end of the first cycle, the first reactor 12 is filled with the material to be converted, ie the feedstock, and is pressurized at the nominal pressure of the plant, ie 20 bar.

[0087] The second reactor 14 is empty and pressurized at the nominal pressure of the plant.

[0088] The third reactor 16 is filled with process products to be unloaded and pressurized. In particular, the hydrothermal char in the third reactor 16 is at a temperature of 40° C. and a pressure of 20 bar.

[0089] The fourth reactor 18 is filled with the initial feed, partially heated at a temperature of 200°C and pressurized at a nominal value, ie 20 bar.

[0090] The fifth reactor 20 is empty and pressurized at the nominal pressure of the plant.

[0091] The sixth reactor 22 is filled with process product and pressurized at a nominal pressure value.

[0092] Subsequently, a second cycle is performed with similar material replacement and conversion to those described above, but with operation of a different reactor.

[0093] In the second cycle, with respect to the first three reactors 12, 14, 16 in which unloading and loading of materials are performed, the operation of the first reactor 12 is performed by the third reactor 16, the operation of the second reactor 14 is performed by the first reactor 12, and the operation of the third reactor 16 is performed by the second reactor 14.

[0094] Regarding the last three reactors 18 , 20 , 22 in which the reaction of converting biomass into hydrothermal charcoal is carried out, the operation of the fourth reactor 18 is carried out by the sixth reactor 22 , the operation of the fifth reactor 20 is carried out by the fourth reactor 18 , and the operation of the sixth reactor 22 is carried out by the fifth reactor 20 .

[0095] In the third cycle, with respect to the first three reactors 12, 14, 16 in which unloading and loading of materials are performed, the operation of the first reactor 12 in the first cycle is performed by the second reactor 14, the operation of the second reactor 14 in the first cycle is performed by the third reactor 16, and the operation of the third reactor 16 in the first cycle is performed by the first reactor 12.

[0096] Regarding the last three reactors 18, 20, 22 in which the reaction of converting biomass into hydrothermal charcoal is carried out, the operation of the fourth reactor 18 in the first cycle is carried out by the fifth reactor 20, the operation of the fifth reactor 20 in the first cycle is carried out by the sixth reactor 22, and the operation of the sixth reactor 22 in the first cycle is carried out by the fourth reactor 18.

[0097] The cycles after the third cycle are the same as the first cycle described above.

[0098] The capacity of the reactor can be changed according to the needs and can also be changed according to the total number of reactors.

[0099] In particular, by increasing the number of reactors, it is possible to:

[0100] - increase the productivity for the same heat exchange time (time 3) while maintaining the same capacity of the reactor; or

[0101] - Reduce the capacity of the reactor while maintaining the same production rate.

[0102] Furthermore, variations may be provided which are considered to be included within the scope of the invention as defined by the following claims.For example, in case of pressure loss, a compressor may be added to restore the pressure of the expansion vessel.

[0103] Furthermore, depending on the moisture content of the biomass, it may be necessary to add water or to recycle part or all of the liquid formed downstream in the process.

[0104] According to a variant of the invention, the first reactor 12 , the second reactor 14 and the third reactor 16 as previously described can be replaced by tanks, with attendant cost savings.

[0105] In this case, the discharge of the process product from the reactor transferred via the exchanger to the tank is carried out by passing the process product through a suitable membrane, taking advantage of the pressure drop between the reactor and the atmosphere.

[0106] Furthermore, when the pressure is exhausted in the passage through the diaphragm, it is necessary to start the compressor to maintain the nominal pressure throughout the cycle time.

Claims

1. A method for converting biomass into hydrothermal charcoal by means of an apparatus (10), the apparatus comprising: - a first reactor (12), a second reactor (14), a third reactor (16), into which raw materials can be loaded from the outside, and process products can be unloaded from the device (10) to the outside; - a fourth reactor (18), a fifth reactor (20) and a sixth reactor (22) in which the conversion of biomass into hydrochar is carried out at a process temperature between 180° C. and 250° C., at a process pressure corresponding to or above the vapor tension of water at said process temperature, i.e. between 15 bar and 30 bar, for a time span equal to a reaction time between 3 and 8 hours; a heat exchanger (24), through which the first reactor (12), the second reactor (14), the third reactor (16) are indiscriminately connected to the fourth reactor (18), the fifth reactor (20) and the sixth reactor (22); - the first reactor (12), the second reactor (14), the third reactor (16), the fourth reactor (18), the fifth reactor (20) and the sixth reactor (22) are also directly connected to each other; The method provides the following in the initial state: - the first reactor (12) is filled with process product, pressurized at the process pressure and at an unloading temperature between 30°C and 50°C; - the second reactor (14) is filled with feedstock and pressurized at the process pressure; - the third reactor (16) is empty and pressurized at the process pressure; - the fourth reactor (18) is filled with process product, pressurized at the process pressure and at the reaction temperature; - the fifth reactor (20) is empty and pressurized at process pressure; - the sixth reactor (22) is filled with feedstock, pressurized at the process temperature and partially heated at a temperature between 160°C and 210°C; The method provides a first loop wherein, simultaneously: - the first reactor (12) is successively isolated from the rest of the plant (10), depressurized at atmospheric pressure, emptied of the process products it contains, loaded with feedstock and, finally, pressurized at the process pressure; - the process product contained in the fourth reactor (18) is transferred to the third reactor (16) through the heat exchanger (24) in countercurrent with the feedstock transferred from the second reactor (14) to the fifth reactor (20) through the heat exchanger (24) to transfer heat from the process product to the feedstock; - the air contained in the third reactor (16) and the fifth reactor (20) is transferred to the second reactor (14) and the fourth reactor (18), respectively; - In the sixth reactor (22), the feedstock is brought to the reaction temperature and reacts and is converted into process products.

2. The method according to claim 1, wherein: At the end of the first cycle, a second cycle is performed, wherein, simultaneously, the operation of the first reactor (12) during the first cycle is performed by the third reactor (16), the operation of the second reactor (14) during the first cycle is performed by the first reactor (12), the operation of the third reactor (16) during the first cycle is performed by the second reactor (14), the operation of the fourth reactor (18) during the first cycle is performed by the sixth reactor (22), the operation of the fifth reactor (20) during the first cycle is performed by the fourth reactor (18) and the operation of the sixth reactor (22) during the first cycle is performed by the fifth reactor (20).

3. The method according to claim 2, wherein: At the end of the second cycle, a third cycle is performed, wherein, simultaneously, the operation of the first reactor (12) during the first cycle is performed by the second reactor (14), the operation of the second reactor (14) during the first cycle is performed by the third reactor (16), the operation of the third reactor (16) during the first cycle is performed by the first reactor (12), the operation of the fourth reactor (18) during the first cycle is performed by the fifth reactor (20), the operation of the fifth reactor (20) during the first cycle is performed by the sixth reactor (22), and the operation of the sixth reactor (22) during the first cycle is performed by the fourth reactor (18).

4. The method according to claim 1, wherein: The level changes within the device are managed by an expansion vessel (26).

5. The method according to claim 2, wherein: The level changes within the device are managed by an expansion vessel (26).

6. The method according to claim 3, wherein: The level changes within the device are managed by an expansion vessel (26).

7. The method according to any one of the preceding claims 1 to 6, wherein: Water is added to the biomass, or the liquid formed downstream in the process is partially or completely recirculated through the biomass.

8. An apparatus (10) for converting biomass into hydrothermal charcoal, comprising: - a first reactor (12), a second reactor (14), a third reactor (16), into which raw materials can be loaded from the outside, and process products can be unloaded from the device (10) to the outside; - a fourth reactor (18), a fifth reactor (20) and a sixth reactor (22) in which the conversion of biomass into hydrochar is carried out at a process temperature between 180° C. and 250° C., at a process pressure corresponding to or above the vapor tension of water at said process temperature, i.e. between 10 bar and 50 bar, for a time span equal to a reaction time between 3 and 8 hours; a heat exchanger (24), through which the first reactor (12), the second reactor (14), the third reactor (16) are indiscriminately connected to the fourth reactor (18), the fifth reactor (20) and the sixth reactor (22); The first reactor (12), the second reactor (14), the third reactor (16), the fourth reactor (18), the fifth reactor (20) and the sixth reactor (22) are also directly connected to each other.

9. The device (10) according to claim 8, wherein A loading / unloading pump (30) is included and is adapted to load feedstock into or unload the process product from at least one of: the first reactor (12), the second reactor (14), the third reactor (16), the fourth reactor (18), the fifth reactor (20), and the sixth reactor (22).

10. The device (10) according to claim 8, wherein A feed pump (32) is included and is adapted to pressurize at least one of the first reactor (12), the second reactor (14), the third reactor (16), the fourth reactor (18), the fifth reactor (20), and the sixth reactor (22).

11. The device (10) according to any one of the preceding claims 8 to 9, wherein: An expansion vessel (26) is included and is adapted to manage level changes within the apparatus.

12. The device (10) according to any one of the preceding claims 8 to 10, wherein: At least one of the first reactor (12), the second reactor (14), and the third reactor (16) is a tank.

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