Bamboo charcoal

Abstract

The present invention provides bamboo charcoal in which phosphorus (P), potassium (K), or ash content is increased while effectively reducing chlorine (Cl). [Solution] The bamboo charcoal according to the present invention has a chlorine content ratio of 0.05 or less to potassium. Furthermore, the bamboo charcoal according to the present invention has a chlorine content ratio of 0.2 or less to phosphorus. Furthermore, the bamboo charcoal according to the present invention has a chlorine content ratio of 0.05 or less to ash.

Description

Technical Field

[0001] The present invention relates to bamboo charcoal with effectively reduced chlorine content.

Background Art

[0002] Bamboo charcoal obtained by carbonizing bamboo is effectively used in screen ink and the like (see Patent Documents 1 and 2 below). In recent years, in consideration of the impact on the environment, halogen-free conversion with effectively reduced chlorine content has been desired.

[0003] Here, in order to achieve halogen-free conversion of bamboo charcoal obtained by carbonizing bamboo, it is necessary to perform a washing step of washing bamboo chips with washing water independently of the carbonization step before or after the carbonization step of carbonizing the raw material bamboo chips, and it has been difficult to reduce the manufacturing cost.

[0004] In particular, when the washing step is performed before the carbonization step, carbonizing bamboo chips containing moisture due to the washing step deteriorates the carbonization efficiency, and in some cases, an inert gas or the like is generated, making it difficult to perform uniform carbonization.

[0005] Therefore, when the washing step is performed before the carbonization step, a drying step of drying the water content of the washed bamboo chips to a predetermined value (for example, 20% or less) after the washing step and before the carbonization step becomes essential, and furthermore, it becomes difficult to reduce the manufacturing cost.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] This invention has been made in view of the prior art described above, and aims to provide bamboo charcoal in which chlorine (Cl) is effectively reduced while increasing the phosphorus (P), potassium (K), or ash content containing these.

[0008] The present invention provides bamboo charcoal in which the chlorine content ratio to potassium is 0.05 or less. Furthermore, the present invention provides bamboo charcoal in which the chlorine content ratio to phosphorus is 0.2 or less. Furthermore, the present invention provides bamboo charcoal in which the chlorine content ratio to the ash content is 0.05 or less.

[0009] The bamboo charcoal according to the present invention is preferably produced by a method for producing bamboo charcoal, which includes a carbonization step in which bamboo chips are contained in a carbonization treatment space and superheated steam generated by a carbonization superheated steam generation mechanism is supplied to the bamboo chips for carbonization treatment, and a carbonization exhaust line is provided, with one end of which is fluidly connected to the carbonization treatment space and the other end open to the outside, and a carbonization exhaust fan inserted in the carbonization exhaust line, while operating the carbonization superheated steam generation mechanism so that the carbonization treatment temperature in the carbonization treatment space is maintained at 450°C to 600°C, and operating the carbonization exhaust fan so that the pressure upstream of the carbonization exhaust fan in the carbonization exhaust line is 100 to 300 Pa.

[0010] In one embodiment of the above-mentioned manufacturing process, the carbonization treatment is carried out by a carbonization apparatus comprising a water supply unit, a carbonization unit, and a control unit.

[0011] The carbonization unit comprises a carbonization case that forms a carbonization processing space, a carbonization screw conveyor that transports bamboo chips from one side to the other in the axial direction of the carbonization case in accordance with rotational drive around its axis, a carbonization superheated steam generation mechanism that supplies superheated steam generated by heating steam or atomized water supplied from the water supply unit into the carbonization case, a carbonization exhaust line with one end fluidly connected to the inside of the carbonization case, a carbonization exhaust fan interposed in the carbonization exhaust line, a carbonization temperature sensor that detects the temperature inside the carbonization case, and a carbonization pressure sensor that detects the pressure upstream of the carbonization exhaust fan in the carbonization exhaust line.

[0012] The control unit is configured to control the operation of the carbonization screw conveyor so that the conveying speed of the carbonization screw conveyor becomes a predetermined set speed, and to control the operation of the carbonization superheated steam generation mechanism so that the carbonization processing temperature in the carbonization case becomes 450°C to 600°C based on the value detected from the carbonization temperature sensor, while also controlling the operation of the carbonization exhaust fan so that the pressure upstream of the carbonization exhaust fan in the carbonization exhaust line is maintained at 100 to 300 Pa based on the value detected from the carbonization pressure sensor.

[0013] The above manufacturing method may preferably include a drying step prior to the carbonization step, in which bamboo chips are placed in a drying space and dried by supplying superheated steam generated by a drying superheated steam generation mechanism.

[0014] In this case, a drying exhaust line is provided, with one end of which is fluidly connected to the drying space and the other end open to the outside, and a drying exhaust fan is inserted into the drying exhaust line. The drying process is performed while operating the drying superheated steam generation mechanism so that the temperature in the drying space is maintained within a predetermined drying temperature range, and operating the drying exhaust fan so that the pressure upstream of the drying exhaust fan in the drying exhaust line is 100 to 300 Pa.

[0015] For example, the drying and carbonization processes are carried out by a carbonization apparatus comprising a water supply unit, a drying unit, a carbonization unit, and a control unit.

[0016] The drying unit comprises a drying case that forms a drying processing space, a drying screw conveyor that transports bamboo chips from one side to the other in the axial direction of the drying case in accordance with rotational drive around its axis, a drying superheated steam generation mechanism that supplies superheated steam generated by heating steam or atomized water supplied from the water supply unit into the drying case, a drying exhaust line with one end fluidly connected to the inside of the drying case, a drying exhaust fan interposed in the drying exhaust line, a drying temperature sensor that detects the temperature inside the drying case, and a drying pressure sensor that detects the pressure upstream of the drying exhaust fan in the drying exhaust line.

[0017] The carbonization unit comprises a carbonization case that forms a carbonization processing space and directly or indirectly receives dried bamboo chips discharged from the other side in the axial direction of the drying case; a carbonization screw conveyor that transports the bamboo chips from one side to the other in the axial direction of the carbonization case in accordance with rotational drive around the axis; a carbonization superheated steam generation mechanism that supplies superheated steam generated by heating steam or atomized water supplied from the water supply unit into the carbonization case; a carbonization exhaust line with one end fluidly connected to the inside of the carbonization case; a carbonization exhaust fan interposed in the carbonization exhaust line; a carbonization temperature sensor that detects the temperature inside the carbonization case; and a carbonization pressure sensor that detects the pressure upstream of the carbonization exhaust fan in the carbonization exhaust line.

[0018] The control unit is configured to control the operation of the drying screw conveyor so that the conveying speed of the drying screw conveyor becomes a predetermined set speed, and to control the operation of the drying superheated steam generation mechanism so that the temperature inside the drying case becomes a predetermined drying processing temperature based on the value detected from the drying temperature sensor, while controlling the operation of the drying exhaust fan so that the pressure upstream of the drying exhaust fan in the drying exhaust line is maintained at 100 to 300 Pa based on the value detected from the drying pressure sensor, and to control the operation of the carbonization screw conveyor so that the conveying speed of the carbonization screw conveyor becomes a predetermined set speed, and to control the operation of the carbonization superheated steam generation mechanism so that the carbonization processing temperature inside the carbonization case becomes 450 to 600°C based on the value detected from the carbonization temperature sensor, while controlling the operation of the carbonization exhaust fan so that the pressure upstream of the carbonization exhaust fan in the carbonization exhaust line is maintained at 100 to 300 Pa based on the value detected from the carbonization pressure sensor. [Effects of the Invention]

[0019] The bamboo charcoal according to the present invention can effectively reduce chlorine (Cl) while increasing the phosphorus (P), potassium (K), or ash content containing these. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 is a schematic diagram of a carbonization apparatus that can be used for producing bamboo charcoal according to one embodiment of the present invention. [Figure 2] Figure 2 is a graph showing the results of Verification 1, in which bamboo charcoal was produced by carbonizing raw bamboo chips without washing treatment using the carbonization apparatus with superheated steam. Multiple types of bamboo charcoal with different manufacturing conditions were produced by varying the carbonization temperature, and the relationship between carbonization temperature and chlorine content was verified by measuring the chlorine content of the multiple types of bamboo charcoal produced. [Figure 3] Figure 3 is a graph showing the results of Verification 2, in which the same verification as Verification 1 was performed on raw bamboo chips with a different chlorine content than those used in Verification 1. [Figure 4]FIG. 4 is a graph showing the contents of chlorine, phosphorus, potassium, and calcium in bamboo charcoal according to an embodiment of the present invention, and the contents of chlorine, phosphorus, potassium, and calcium in washed bamboo chips obtained by performing a washing process on the raw bamboo chips.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, an embodiment of bamboo charcoal according to the present invention will be described with reference to the accompanying drawings.

[0022] First, a carbonization device 1 that can be suitably used for manufacturing bamboo charcoal according to the present embodiment will be described. FIG. 1 shows a schematic diagram of the carbonization device 1.

[0023] As shown in FIG. 1, the carbonization device 1 includes a water supply unit 90 that supplies steam or atomized water, a carbonization unit 200, and a control unit 300.

[0024] The carbonization unit 200 is configured to carbonize bamboo chips to produce bamboo charcoal. Specifically, as shown in FIG. 1, the carbonization unit 200 includes a carbonization case 210, a carbonization screw conveyor 220, a carbonization superheated steam generation mechanism 230, a carbonization exhaust line 80, and a carbonization exhaust fan 82 inserted into the carbonization exhaust line 80.

[0025] The carbonization case 210 forms a carbonization treatment space 210A for the bamboo chips, which are the objects to be processed. As shown in FIG. 1, the carbonization case 210 has a carbonization inlet 210(in) for receiving bamboo chips on one side of the carbonization treatment space 210A and a carbonization outlet 210(out) for discharging bamboo chips from the other side of the carbonization treatment space 210A.

[0026] The carbonization screw conveyor 220 is configured to transport the bamboo chips supplied into the carbonization case 210 from the carbonization receiving port 210 (in) toward the carbonization discharge port 210 (out) on the other side of the carbonization case 210 in the axial direction, in response to rotational drive around its axis.

[0027] Specifically, the carbonization screw conveyor 220 includes a carbonization conveyor actuator 222, such as an electric motor, which is operated and controlled by the control unit 300; a rotating shaft 224, which is housed longitudinally within the carbonization case 210 and rotated around its axis by the carbonization conveyor actuator 222; and a conveying body 226, such as a spiral blade, provided on the rotating shaft 224.

[0028] The carbonization superheated steam generation mechanism 230 is configured to generate superheated steam by heating steam or atomized water supplied from the water supply unit 90, and to supply the generated superheated steam into the carbonization case 210.

[0029] As shown in Figure 1, the carbonization superheated steam generation mechanism 230 includes a carbonization cover 240 that is detachably connected to the carbonization case 210, and a carbonization fluid heating pipe 250 supported by the carbonization cover 240.

[0030] More specifically, the carbonization case 210 is provided with an upward carbonization opening that opens the carbonization processing space 210A upward between the carbonization receiving port 210(in) and the carbonization discharge port 210(out) with respect to the conveying direction of the carbonization screw conveyor 220, and the carbonization cover 240 is connected to the carbonization case 210 so as to airtightly close the upward carbonization opening.

[0031] The carbonization fluid heating tube 250 is a long, hollow member made of a conductive material such as Inconel, Hastelloy®, or stainless steel, which generates heat in response to the voltage applied from the voltage supply unit 260, which is operated under the control unit 300. It is configured to receive steam or atomized water supplied from the water supply unit 90 into its internal space, and when it is heated by the voltage applied from the voltage supply unit 260, it converts the steam or atomized water in the internal space into superheated steam, which is then released to the outside.

[0032] More specifically, the carbonization fluid heating tube 250 is supported by the carbonization cover 240 such that, when the carbonization cover 240 is connected to the carbonization case 210, the first end on one longitudinal side and the second end on the other longitudinal side extend outward from the carbonization cover 240, and the intermediate portion between the first and second ends faces the carbonization upper opening.

[0033] The first and second ends are provided with first and second power supply points, respectively, and one of the first and second ends is provided with an inlet for introducing steam or atomized water from the water supply mechanism 90 into the internal space of the carbonization fluid heating tube 250.

[0034] In the illustrated configuration, as shown in Figure 1, the water supply unit 90 has a boiler 91, and steam is supplied from the boiler 91 to the inlet of the carbonization fluid heating pipe 250. In Figure 1, reference numeral 93 denotes a control valve that adjusts the amount of steam supplied from the boiler 91 to the carbonization fluid heating pipe 250. The control valve 93 is operated under control by the control unit 300 or manually operated.

[0035] One or more discharge ports (not shown) are provided in the middle portion of the carbonization fluid heating tube 250, and the superheated steam generated by the carbonization fluid heating tube 250 is discharged to the outside from the one or more discharge ports and supplied to the carbonization processing space 210A through the carbonization upper opening.

[0036] The carbonization exhaust line 80 has one end fluidly connected to the carbonization processing space 210A, and the other end is directly or indirectly open to the atmosphere.

[0037] As shown in Figure 1, in the illustrated configuration, the carbonization apparatus 1 has a forced oxidation mechanism 85, and the other end of the carbonization exhaust line 80 is fluidly connected to the forced oxidation mechanism 85.

[0038] By providing the carbonization exhaust line 80, the carbonization exhaust fan 82, and the forced oxidation mechanism 85, unwanted gases such as tar generated during the carbonization process of bamboo chips can be drawn from the carbonization space 210A and released into the atmosphere after being burned by the forced oxidation mechanism 85.

[0039] As shown in Figure 1, the carbonization apparatus 1 further includes a carbonization temperature sensor 219 for detecting the temperature of the carbonization processing space 210A, and a carbonization pressure sensor 89 for detecting the pressure upstream of the carbonization exhaust fan 82 in the carbonization exhaust line 80.

[0040] The control unit 300 is configured to control the operation of the carbonization exhaust fan 82 based on the pressure value signal from the carbonization pressure sensor 89, so that the pressure upstream of the carbonization exhaust fan 82 in the carbonization exhaust line 80 is maintained within a predetermined carbonization exhaust pressure reduction range.

[0041] The predetermined carbonization exhaust pressure reduction range is set appropriately according to the amount of bamboo chips contained in the carbonization space 210A and the transport speed of the carbonization screw conveyor 220, within a range in which the pressure inside the carbonization space 210A is maintained at a pressure higher than atmospheric pressure, while effectively discharging unwanted gases generated during the carbonization process from the carbonization space 210A, and preventing excessive suction of superheated steam supplied to the carbonization space 210A from the carbonization superheated steam generation mechanism 230.

[0042] Furthermore, the control device 300 is configured to control the operation of the carbonization superheated steam generation mechanism 230 so that the carbonization processing temperature in the carbonization processing space 210A reaches a predetermined temperature based on the value detected from the carbonization temperature sensor 219.

[0043] As shown in Figure 1, the carbonization apparatus 1 further includes a drying section 100 located upstream of the carbonization section 200 with respect to the processing flow direction of the bamboo chips.

[0044] If the bamboo chips contain excessive moisture (for example, moisture content exceeding 20%) during the carbonization process by the carbonization unit 200, uniform carbonization becomes difficult, and in some cases, problems such as the generation of inert gas may occur.

[0045] The drying section 100 is provided in the carbonization apparatus 1 to prevent such problems. Therefore, if the bamboo chips to be processed are sufficiently dry (for example, with a moisture content of 20% or less), the drying process in the drying section 100 can be omitted.

[0046] As shown in Figure 1, the drying unit 100 includes a drying case 110, a drying screw conveyor 120, a drying superheated steam generation mechanism 130, a drying exhaust line 70, and a drying exhaust fan 72 inserted into the drying exhaust line 70.

[0047] The drying case 110 forms a drying space 110A for the bamboo chips to be processed. As shown in Figure 1, the drying case 110 has a drying inlet 110(in) for receiving bamboo chips into one side of the drying space 110A, and a drying outlet 110(out) for discharging bamboo chips from the other side of the drying space 110A.

[0048] The drying screw conveyor 120 is configured to transport the bamboo chips supplied into the drying case 110 from the drying inlet 110 (in) toward the drying outlet 110 (out) on the other side of the drying case 110 in the axial direction, in response to rotational drive around its axis.

[0049] Specifically, the drying screw conveyor 120 includes a drying conveyor actuator 122, such as an electric motor, which is operated and controlled by the control unit 300; a rotating shaft 124, which is housed longitudinally within the drying case 110 and rotated around its axis by the drying conveyor actuator 122; and a conveying body 126, such as a spiral blade, provided on the rotating shaft 124.

[0050] The drying superheated steam generating mechanism 130 is configured to generate superheated steam by heating steam or atomized water supplied from the water supply unit 90, and to supply the generated superheated steam into the drying case 110.

[0051] As shown in Figure 1, the drying superheated steam generation mechanism 130 includes a drying cover 140 that is detachably connected to the drying case 110, and a drying fluid heating pipe 150 supported by the drying cover 140.

[0052] More specifically, the drying case 110 is provided with an upward drying opening that opens the drying processing space 110A upward between the drying inlet 110(in) and the drying outlet 110(out) in relation to the conveying direction of the drying screw conveyor 120, and the drying cover 140 is connected to the drying case 110 so as to airtightly close the upward drying opening.

[0053] The drying fluid heating tube 150 is a long, hollow member made of a conductive material such as Inconel, Hastelloy (registered trademark), or stainless steel, which generates heat in response to the voltage applied from the voltage supply unit 260, whose operation is controlled by the control unit 300. It is configured to receive steam or atomized water supplied from the water supply unit 90 into its internal space, and when it is heated by the voltage applied from the voltage supply unit 260, it converts the steam or atomized water in the internal space into superheated steam, which is then released to the outside.

[0054] More specifically, the drying fluid heating tube 150 is supported by the drying cover 140 such that, when the drying cover 140 is connected to the drying case 110, the first end on one longitudinal side and the second end on the other longitudinal side extend outward from the drying cover 140, and the intermediate portion between the first and second ends faces the upper opening for drying.

[0055] The first and second ends are provided with first and second power supply points, respectively, and one of the first and second ends is provided with an inlet for introducing steam or atomized water from the water supply mechanism 90 into the internal space of the drying fluid heating tube 150.

[0056] As described above, in the illustrated configuration, the water supply unit 90 has a boiler 91, and steam is supplied from the boiler 91 to the inlet of the drying fluid heating pipe 150. In Figure 1, reference numeral 92 denotes a control valve that adjusts the amount of steam supplied from the boiler 91 to the drying fluid heating pipe 150. The control valve 92 is operated under control by the control unit 300 or manually operated.

[0057] One or more discharge ports (not shown) are provided in the middle portion of the drying fluid heating tube 150, and the superheated steam generated by the drying fluid heating tube 150 is discharged to the outside from the one or more discharge ports and supplied to the drying processing space 110A through the drying upper opening.

[0058] The drying exhaust line 70 has one end fluidly connected to the drying processing space 110A, and the other end fluidly connected to the carbonization exhaust line 80.

[0059] By providing the drying exhaust line 70 and the drying exhaust fan 72, excess steam from the drying processing space 110A can be released into the atmosphere without affecting the processing of the bamboo chips, which are the material to be processed. The drying exhaust fan 72 is configured to be operated and controlled by the control unit 300.

[0060] As shown in Figure 1, the carbonization apparatus 1 further includes a drying temperature sensor 119 for detecting the temperature of the drying space 110A, and a drying pressure sensor 79 for detecting the pressure upstream of the drying exhaust fan 72 in the drying exhaust line 70.

[0061] In this case, the control unit 300 is configured to control the operation of the drying exhaust fan 72 based on the pressure value signal from the drying pressure sensor 119, so that the pressure upstream of the drying exhaust fan 72 in the drying exhaust line 70 is maintained within a predetermined drying exhaust pressure reduction range.

[0062] The predetermined drying exhaust pressure reduction range is set appropriately within a range in which the drying space 110A is maintained at a pressure higher than atmospheric pressure, depending on the amount of bamboo chips contained in the drying space 110A and the conveying speed of the drying screw conveyor 120.

[0063] Furthermore, the control device 300 is configured to control the operation of the drying superheated steam generation mechanism 130 so that the drying temperature of the drying space 110A reaches a predetermined temperature based on the value detected from the drying temperature sensor 119.

[0064] As shown in Figure 1, in the illustrated configuration, the carbonization apparatus 1 further has an intermediate conveying section 50 between the drying section 100 and the carbonization section 200 with respect to the processing direction of the bamboo chips, and the bamboo chips are supplied to the carbonization case 210 from the intermediate conveying section 50.

[0065] The intermediate transport section 50 includes an intermediate transport case 51 that defines an airtight intermediate transport space, and an intermediate transport screw conveyor 52 that transports the material to be processed from one side to the other within the intermediate transport space of the intermediate transport case 51.

[0066] The intermediate transport case 51 has an intermediate receiving port 51(in) and an intermediate discharge port 51(out) formed to communicate with one side and the other side of the intermediate transport space, respectively, and the drying discharge port 110(out) of the drying case 110 is airtightly connected to the intermediate receiving port 51(in) of the intermediate transport case 51, and the intermediate discharge port 51(out) of the intermediate transport case 51 is airtightly connected to the carbonization receiving port 210(in) of the carbonization case 210.

[0067] The intermediate conveying screw conveyor 52 includes a rotating shaft 52a that traverses the conveying space longitudinally with at least one end extending outward, a conveying body 52b such as a helical blade provided on the rotating shaft 52a, and an actuator (not shown) such as an electric motor that is operated by the control unit 300 and rotates one end of the rotating shaft 52a.

[0068] As shown in Figure 1, the carbonization apparatus 1 is further equipped with a hopper 20 capable of accommodating bamboo chips upstream of the drying section 100 in the processing direction of the bamboo chips, and the drying inlet 110(in) of the drying case 110 is directly or indirectly connected to the outlet of the hopper 20.

[0069] In the illustrated configuration, as shown in Figure 1, an upstream conveying unit 30 is interposed between the hopper 20 and the drying unit 100.

[0070] The upstream transport section 30 includes an upstream transport case 31 that defines an airtight upstream transport space, and an upstream transport screw conveyor 32 that transports the material to be processed from one side to the other within the upstream transport space of the upstream transport case 31.

[0071] The upstream transport case 31 has an upstream receiving port 31(in) and an upstream discharge port 31(out) formed to communicate with one side and the other side of the upstream transport space, respectively, the outlet of the hopper 20 is airtightly connected to the upstream receiving port 31(in) of the upstream transport case 31, and the upstream discharge port 31(out) of the upstream transport case 31 is airtightly connected to the drying receiving port 110(in) of the drying case 110.

[0072] As shown in Figure 1, the carbonization apparatus 1 is further provided with an upstream on-off valve 40 that directly or indirectly opens and closes the drying inlet 110(in) of the drying case 110. By providing the upstream on-off valve 40, the amount of bamboo chips fed into the drying section 100 can be controlled.

[0073] Furthermore, by providing the upstream on-off valve 40, the inflow of air into the drying case 110 can be more reliably prevented, thereby effectively maintaining the superheated steam atmosphere inside the drying case 110.

[0074] In other words, since the inside of the drying case 110 is pressurized by the superheated steam released from the drying fluid heating pipe 130, it is possible to some extent to prevent air from flowing in from the drying inlet 110(in) of the drying case 110 even without the upstream shut-off valve 40. However, by providing the upstream shut-off valve 40, this inflow of air can be prevented more reliably.

[0075] Furthermore, by providing the upstream on-off valve 40 to prevent the inflow of air into the drying space 110A, the operation control of the drying exhaust fan 72 by the control device 300 to maintain the drying space 110A within a predetermined pressure range, and / or the operation control of the carbonization exhaust fan 82 by the control device 300 to maintain the carbonization space 210A within a predetermined pressure range, can be performed more easily and accurately.

[0076] The upstream on-off valve 40 may be configured to be opened and closed by an actuator whose operation is controlled by the control unit 300. In the illustrated configuration, the upstream on-off valve 40 is interposed in the piping connecting the upstream discharge port 31 (out) of the upstream transport case 31 and the drying inlet 110 (in) of the drying case 110.

[0077] Furthermore, as shown in Figure 1, the carbonization apparatus 1 is provided with a downstream on-off valve 60 that directly or indirectly opens and closes the carbonization outlet 210 (out) of the carbonization case 210.

[0078] By providing the downstream on-off valve 60, the inflow of air into the carbonization case 210 can be more reliably prevented, thereby effectively maintaining the superheated steam atmosphere inside the carbonization case 210.

[0079] In other words, since the inside of the carbonization case 210 is pressurized by the superheated steam released from the carbonization fluid heating pipe 230, it is possible to some extent to prevent air from flowing in from the carbonization outlet 210 (out) of the carbonization case 210 even without the downstream shut-off valve 60. However, by providing the downstream shut-off valve 60, this inflow of air can be prevented more reliably.

[0080] Furthermore, by providing the downstream on-off valve 40 to prevent the inflow of air into the carbonization processing space 210A, the operation control of the carbonization exhaust fan 82 by the control device 300 to maintain the carbonization processing space 210A within a predetermined pressure range and / or the operation control of the drying exhaust fan 72 by the control device 300 to maintain the drying processing space 110A within a predetermined pressure range can be performed more easily and accurately.

[0081] The downstream on-off valve 60 may be configured to be opened and closed by an actuator whose operation is controlled by the control unit 300. In the illustrated configuration, the downstream on-off valve 60 is provided at the carbonization outlet 210(out) of the carbonization case 210.

[0082] Here, the inventor of the present application, In a method for producing bamboo charcoal by carbonizing bamboo chips with superheated steam, it is possible to remove contained chlorine while carbonizing the raw bamboo chips with superheated steam by performing the carbonization treatment at a lower temperature than the normal temperature (650°C to 750°C), and • By maintaining a superheated steam atmosphere in the carbonization treatment space by pressurizing it to a pressure higher than atmospheric pressure, an effective carbonization state can be achieved. At the same time, by venting the carbonization treatment space to maintain the pressure within a predetermined carbonization range, appropriately set according to carbonization conditions such as the amount of bamboo chips being processed, it may be possible to effectively prevent chlorine, which can be washed off from the bamboo chips during carbonization with superheated steam, from reattaching to the bamboo chips, thereby obtaining bamboo charcoal with effectively reduced chlorine content. I came up with this novel idea and conducted the following verification.

[0083] Verification 1 Bamboo charcoal was produced by drying and carbonizing raw bamboo chips with a chlorine content of 2190 ppm using the carbonization apparatus 1 without any washing treatment.

[0084] The drying process was carried out under the following conditions. The operation of the drying exhaust fan 72 was controlled so that the pressure upstream of the drying exhaust fan 72 in the drying exhaust line 70 was maintained within a predetermined reduced pressure range (100 to 300 Pa), while the operation of the drying superheated steam generation mechanism 130 was controlled so that the drying process temperature detected by the drying temperature sensor 119 was maintained at 400°C to 600°C, thereby obtaining bamboo chips in a dried state (moisture content of 20% or less).

[0085] The carbonization process was carried out under the following conditions. Multiple types of bamboo charcoal chips with different carbonization temperatures were produced by controlling the operation of the carbonization exhaust fan 82 so that the pressure upstream of the carbonization exhaust fan 82 in the carbonization exhaust line 80 is maintained within a predetermined carbonization exhaust pressure reduction range (100 to 300 Pa), while controlling the operation of the carbonization superheated steam generation mechanism 230 so that the carbonization processing temperature detected by the carbonization temperature sensor 219 is maintained at 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, and 700°C, respectively.

[0086] The chlorine content of bamboo charcoal chips produced at carbonization temperatures of 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, and 700°C was 1460 ppm, 164 ppm, 196 ppm, 257 ppm, 850 ppm, 1250 ppm, and 1610 ppm, respectively. The results of Verification 1 are shown in Figure 2.

[0087] Verification 2 Bamboo charcoal was produced by drying and carbonizing raw bamboo chips with a chlorine content of 740 ppm under the same conditions as in Study 1, without any washing treatment.

[0088] The chlorine content of bamboo charcoal chips produced at carbonization temperatures of 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, and 700°C was 902 ppm, 157 ppm, 160 ppm, 150 ppm, 175 ppm, 974 ppm, and 676 ppm, respectively. The results of Verification 2 are shown in Figure 3.

[0089] As is clear from the results of Verification 1 and 2, when carbonizing bamboo chips with superheated steam, if the carbonization temperature is maintained at a lower temperature than the normal carbonization temperature, 450°C to 600°C, and the carbonization exhaust fan 82 is operated so that the pressure upstream of the carbonization exhaust fan 82 in the carbonization exhaust line 80 is maintained within a predetermined carbonization exhaust pressure reduction range, it was possible to produce bamboo charcoal with effectively reduced chlorine content without washing.

[0090] Verification 3 Bamboo charcoal was produced by drying and carbonizing raw bamboo chips with chlorine (Cl), phosphorus (P), potassium (K), and calcium (Ca) content of 2190 ppm, 207 ppm, 3650 ppm, and 146 ppm, respectively, using the carbonization apparatus 1 without any washing treatment.

[0091] The drying process was carried out under the following conditions. The operation of the drying exhaust fan 72 was controlled so that the pressure upstream of the drying exhaust fan 72 in the drying exhaust line 70 was maintained within a predetermined reduced pressure range (100 to 300 Pa), while the operation of the drying superheated steam generation mechanism 130 was controlled so that the drying process temperature detected by the drying temperature sensor 119 was maintained at 400°C to 600°C, thereby obtaining bamboo chips in a dried state (moisture content of 20% or less).

[0092] The carbonization process was carried out under the following conditions. The operation of the carbonization exhaust fan 82 was controlled so that the pressure upstream of the carbonization exhaust fan 82 in the carbonization exhaust line 80 was maintained within a predetermined carbonization exhaust pressure reduction range (100 to 300 Pa), while the operation of the carbonization superheated steam generation mechanism 230 was controlled so that the carbonization processing temperature detected by the carbonization temperature sensor 219 was maintained at 500°C, thereby producing bamboo charcoal chips.

[0093] The chlorine (Cl), phosphorus (P), potassium (K), and calcium (Ca) content of the bamboo charcoal chips produced in this manner was 257 ppm, 2200 ppm, 8420 ppm, and 459 ppm, respectively. The results of Verification 3 are shown in Figure 4.

[0094] As a comparative example, washed bamboo chips were prepared by washing raw bamboo chips with the same components, and washed bamboo charcoal chips were produced by drying and carbonizing these washed bamboo chips. The chlorine (Cl), phosphorus (P), potassium (K), and calcium (Ca) content of these chips was then measured.

[0095] As part of the washing process, the raw bamboo chips were impregnated with deionized water and then boiled and cooled. The conditions for drying and carbonization were the same as those in Verification 3 above.

[0096] The chlorine (Cl), phosphorus (P), potassium (K), and calcium (Ca) content of the washed bamboo charcoal chips was 49 ppm, 87 ppm, 355 ppm, and 197 ppm, respectively. The results of the comparative example are also shown in Figure 4.

[0097] From the results of Verification 3 and the comparative example, it was found that when washing is performed, not only chlorine (Cl) but also phosphorus (P), potassium (K), and calcium (Ca) ash is removed. On the other hand, when carbonization is performed without washing, by supplying superheated steam to maintain the carbonization temperature at 500°C and controlling the operation of the carbonization exhaust fan 82 so that the pressure upstream of the carbonization exhaust fan 82 in the carbonization exhaust line 80 is maintained within a predetermined carbonization exhaust pressure reduction range (100-300 Pa), it is possible to effectively reduce chlorine (Cl) while increasing the ash content of phosphorus (P), potassium (K), and calcium (Ca).

[0098] More specifically, the ratio of chlorine (Cl) to potassium (K) was 0.6 (=2190 / 3650) in the raw bamboo chips, 0.13 (=257 / 355) in the comparative example, and 0.03 (=257 / 8420) in Verification 3.

[0099] Therefore, according to a method for producing bamboo charcoal in which superheated steam is supplied so that the carbonization temperature is 450°C to 600°C without washing, and the operation of the carbonization exhaust fan 82 is controlled so that the pressure upstream of the carbonization exhaust fan 82 in the carbonization exhaust line 80 is maintained within a predetermined carbonization exhaust pressure reduction range (100 to 300 Pa), it is considered that bamboo charcoal with a chlorine content ratio of 0.05 or less to potassium, which has been difficult to obtain conventionally, can be effectively produced.

[0100] Furthermore, the ratio of chlorine (Cl) to phosphorus (P) was 10.58 (=2190 / 207) in the raw bamboo chips, 0.563 (=49 / 87) in the comparative example, and 0.117 (=257 / 2200) in Verification 3.

[0101] Therefore, according to a method for producing bamboo charcoal in which superheated steam is supplied so that the carbonization temperature is 450°C to 600°C without washing, and the operation of the carbonization exhaust fan 82 is controlled so that the pressure upstream of the carbonization exhaust fan 82 in the carbonization exhaust line 80 is maintained within a predetermined carbonization exhaust pressure reduction range (100 to 300 Pa), it is considered that bamboo charcoal with a chlorine content ratio of 0.2 or less to phosphorus, which has been difficult to obtain in the past, can be effectively produced.

[0102] Furthermore, the ratio of chlorine (Cl) content to ash containing phosphorus (P), potassium (K), and calcium (Ca) was 0.547 (=2190 / (207+3650+146)) for the raw bamboo chips, 0.0766 (=49 / (87+355+197)) for the comparative example, and 0.023 (=257 / 2200+8420+459) for Verification 3.

[0103] Therefore, according to a method for producing bamboo charcoal in which superheated steam is supplied so that the carbonization temperature is 450°C to 600°C without washing, and the operation of the carbonization exhaust fan 82 is controlled so that the pressure upstream of the carbonization exhaust fan 82 in the carbonization exhaust line 80 is maintained within a predetermined carbonization exhaust pressure reduction range (100 to 300 Pa), it is considered that bamboo charcoal with a chlorine content ratio of 0.05 or less to ash content, which has been difficult to obtain conventionally, can be effectively produced. [Explanation of symbols]

[0104] 1. Carbonization apparatus 70 Dry exhaust line 72 Drying exhaust fan 79 Drying pressure sensor 82 Carbonization Exhaust Fan 89 Carbonization pressure sensor 90 Water supply section 100 Drying section 110 Drying Case 119 Drying temperature sensor 120 Drying Screw Conveyor 130 Superheated steam generation mechanism for drying 200 Carbonized section 210 Carbonization Cases 210A Carbonization treatment space 219 Carbonization temperature sensor 220 Carbonization Screw Conveyor 230 Superheated steam generation mechanism for carbonization 300 Control Unit

Claims

1. Bamboo charcoal characterized by having a chlorine content ratio of 0.05 or less to potassium.

2. Bamboo charcoal characterized by having a chlorine content ratio of 0.2 or less relative to phosphorus.

3. Bamboo charcoal characterized by having a chlorine content ratio of 0.05 or less relative to ash content.

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