JP7065699B2 - Power generation method - Google Patents

Description

The present invention relates to a novel power generation method using bamboo as a raw material. Specifically, when bamboo is used as fuel for boilers in thermal power generation equipment, by applying a specific treatment to the bamboo material, the amount of harmful substances contained can be reduced to an extremely small amount, and the thermal power generation equipment can be stabilized for a long period of time. It provides a power generation method that can be operated.

The global warming phenomenon associated with the increase in carbon dioxide emissions has become a problem in recent years. The main cause of this is considered to be the use of fossil fuels such as petroleum and coal. In addition, the reserves of these fossil fuels are limited, and various energy sources alternative to petroleum and coal have been studied, and various uses of biomass have been proposed as the above-mentioned energy sources.

Particularly in recent years, there has been a movement to use biomass as a part of conventional coal or instead of coal in thermal power generation facilities.

On the other hand, bamboo represented by Moso bamboo has strong fertility, and as a result, the expansion of bamboo forests is regarded as a problem nationwide. That is, the expansion of the bamboo grove causes the forest to erode and kill the native trees, and the land that has become a bamboo grove has shallow bamboo roots and poor water retention, which makes it easy to cause landslides.

Under such circumstances, studies are being conducted to utilize the bamboo material obtained by cutting the bamboo in the so-called abandoned bamboo grove, where the growth of the bamboo is not controlled, as the biomass.

However, bamboo has a high content of potassium and chlorine, and when it is used as a boiler fuel for thermal power generation equipment, there is a problem that there is a concern that chlorine may corrode the equipment and potassium may generate clinker. As a method for solving such a problem, a method of eluting potassium and chlorine by immersing the finely divided bamboo material in water (Prior Patent Document 1), and a method of immersing the chipped bamboo material in water and then highly melting the material. A method of adhering a spotting substance to prevent chlorination (Prior Patent Document 2) and the like have been proposed.

However, the method for removing potassium and chlorine by elution with water has room for improvement in its removing effect. Further, although crushing is necessary to increase the removal rate of potassium and chlorine by the pulverization, there is also a problem that bamboo is difficult to crush and requires a lot of time and effort.

Japanese Patent No. 5735959 Japanese Unexamined Patent Publication No. 2018-021134

Therefore, an object of the present invention is to remove potassium and chlorine to the extent that there is almost no effect on the thermal power generation equipment when the bamboo material is used as a boiler fuel for the thermal power generation equipment, for example, and the thermal power generation equipment is used for a long period of time. The purpose is to provide a power generation method that can operate stably.

As a result of diligent research to solve the above problems, the present inventors have been able to reduce potassium and chlorine contained in bamboo material to extremely low levels by subjecting bamboo material to hydrothermal treatment under specific conditions. At the same time, it was found that a part of hemicellulose contained in the bamboo material can be removed and the subsequent pulverization becomes easy, and the present invention has been completed.

That is, according to the present invention, the processed product obtained by the pressurized hot water treatment step of treating the bamboo material at a temperature of 110 to 250 ° C. for 0.05 to 5 hours in the presence of water and the pressurized hot water treatment step is solid. Provided is a power generation method comprising a separation step of separating a substance residue and an extract, and a power generation step of using the solid substance residue obtained from the separation step as a part or all of boiler fuel in a power generation facility. To.

In the pressurized hot water treatment step, it is preferable to allow water to be present in a ratio of 3 to 100 parts by mass with respect to 1 part by mass of the bamboo material in order to sufficiently exert the effect of the pressurized water heat treatment.

Further, in the pressurized hot water treatment step, it is preferable to pressurize at a pressure 0.5 to 2 MPa higher than the standard vapor pressure of water at the temperature , because a high effect can be exhibited in a shorter time. ..

According to the present invention, the chlorine concentration in the solid residue obtained by separating from water in the separation step can be 100 ppmw or less, and the potassium concentration can be 500 ppmw or less, which are extremely low concentrations.

In the power generation method of the present invention, a fluidized bed boiler and a stoker-fired boiler are preferably used as the boiler used in the power generation process.

Further, in the present invention, a bamboo material having strength and difficult to crush is supplied to the pressurized hot water treatment step in a relatively large state, and the strength obtained by treating the bamboo material before the power generation step is lowered. By crushing the solid residue, it becomes possible to economically perform crushing for optimization as a fuel with a small amount of crushing energy.

Further, the above-mentioned solid matter residue can be used as a part or all of the boiler fuel, but when the boiler fuel is coal and is used as a part thereof, the above-mentioned solid matter residue which is easy to pulverize can be used. By co-crushing with coal in the crushing step, crushing can be performed more economically, and since it can be sufficiently mixed with coal, a stable calorific value can be maintained in the boiler.

The power generation method of the present invention employs a step of treating the bamboo material with pressurized hot water under specific conditions, so that the content of potassium and chlorine is extremely smaller than that of the bamboo material, specifically, the chlorine concentration is high. Since a solid residue having a potassium concentration of 50 ppm or less and a potassium concentration of 500 ppm or less can be obtained, by using this as a fuel for a boiler of a thermal power generation facility, it is stable for a long period of time with almost no influence of potassium and chlorine. Then, it becomes possible to operate the thermal power generation facility.

Further, by treating the bamboo material with pressurized hot water, a part of the hemicellulose component is removed, and the obtained solid material residue becomes a material that can be easily crushed. It becomes possible to crush the surface.

Furthermore, the extract obtained by the pressurized water heat treatment contains useful components such as hemicellulose contained in bamboo material, which can be effectively used for other purposes.

In the method of the present invention, a typical flow sheet for performing pressurized hot water treatment in a batch manner. In the method of the present invention, a typical flow sheet for continuously performing pressurized hot water treatment.

In the present invention, examples of the bamboo material include known bamboo materials such as Moso bamboo, broken bamboo, matake, and four-sided bamboo. Will be done. In addition, branches and leaves may be cut off as needed.
It is preferable in terms of handling that the bamboo material is processed to an appropriate size before being subjected to the pressurized hot water treatment step. Specifically, it is preferably processed to have an average major axis of 5 to 500 mm, preferably 20 to 300 mm. Of course, in the above processing, atomization of less than 5 mm may be performed, but it takes a lot of time and effort, and the effect of the pressurized hot water treatment is sufficient if it is processed to the above size, and there is a big difference due to atomization. not.

However, in the pressurized hot water treatment step described later, when handleability at the time of supply to the apparatus is required, it may be preferable to perform atomization, and the aspect of atomization is excluded in the present invention. is not. It is also possible to recover fine powder generated when cutting or crushing bamboo material and use it as a part of the raw material.

As a processing method, after logging, it can be cut into an appropriate size if necessary, and then processed with a crusher such as a hammer mill. When using a crusher without a cutter such as a hammer mill, it is possible to significantly reduce the replacement frequency. Of course, it is also possible to use a crusher having a cutter such as a cutter mill or a ring mill.

The greatest feature of the present invention is to have a pressurized hot water treatment step of treating bamboo material with pressurized hot water under specific conditions, and to use the solid residue after such treatment as fuel.

In the pressurized hot water treatment, the bamboo material is subjected to a temperature of 150 to 220 ° C. , preferably 165 to 190 ° C. for 0.05 to 5 hours, preferably 0.1 to 0.5 in the presence of water. It is done by time processing.

When the temperature in the pressurized hot water treatment is lower than the above range, potassium and chlorine cannot be sufficiently extracted. Further, the extraction amount of the active ingredient such as hemicellulose is also reduced. Further, when the temperature is higher than the above range, the decomposition of cellulose starts, the decomposed product dissolves in water, the amount of solid matter that can be used as fuel decreases, and the amount of lignin decomposed increases, which is not preferable.

Further, if the time of the pressurized hot water treatment is too short, potassium and chlorine cannot be sufficiently extracted, and if it is too long, the effect reaches a plateau, which is not economical.

In the pressurized hot water treatment step, the amount of water to be present may be sufficient as long as it can extract potassium and chlorine, but if it is used too much, excessive energy is required for concentration in the reuse of the extract. It requires a lot of labor to process the extract, which is industrially disadvantageous. Therefore, it is preferable to allow water to be present in a proportion of 3 to 100 parts by mass, preferably 4 to 50 parts by mass, and more preferably 5 to 30 parts by mass with respect to 1 part by mass of the treated bamboo material.

The 1 part by mass of the bamboo material is based on the dry weight excluding water, and the amount of water to be present is adjusted within the above range including the amount of water contained in the bamboo material.

The dry weight of the bamboo material, the solid residue described later, and the like was measured at 100 ° C. after drying for 24 hours while flowing nitrogen at 10 L / min per 10 g.

The pressure in the pressurized hot water treatment is set to a pressure higher than the pressure at which the water can maintain the liquid state at the temperature, but the theoretical steam pressure corresponding to the temperature is used in order to exert a sufficient extraction effect of potassium and chlorine. It is preferable to set the pressure higher by 0.001 to 2 MPa. Further preferably, in the present invention in which the pressure is set to 0.01 to 1 MPa higher, the apparatus used for the pressurized hot water treatment is not particularly limited to an apparatus capable of achieving the above conditions, and an autoclave is generally used. Further, the operation of the pressurized hot water treatment may be performed in batch or continuously.

According to the pressurized hot water treatment of the present invention, potassium and chlorine can be effectively removed together with hemicellulose by decomposing hemicellulose of bamboo material and dissolving the decomposed product in water. As a result, the efficiency of removing potassium and chlorine is significantly improved. Incidentally, according to the present invention, the chlorine concentration in the solid residue obtained by the separation step described later can be reduced from 100 ppmw or less, more preferably 50 ppm or less, still more preferably 20 ppm or less. Further, the potassium concentration can be reduced from 500 ppmw to 100 ppm or less, more preferably 30 ppm or less.

The amount of hemicellulose removed is higher at higher temperatures and increases as the time increases. In the present invention, the removal rate of hemicellulose after the pressure hot water treatment can be achieved to be 20% or more, particularly 50% or more, and further 80% or more, based on the amount of hemicellulose contained in the raw bamboo material.

In addition, lignin has a benzene ring and is highly valuable as a high-calorie fuel. Therefore, it is preferable to reduce the ratio of decomposition and dissolution in water as much as possible. According to the pressurized hot water treatment, 10 to 60% by mass, further 15 to 50% by mass, based on the amount of lignin contained in the raw material. In particular, it can be suppressed to 20 to 40% by mass.

Cellulose has high value as a fuel. Therefore, it is preferable to reduce the ratio of decomposition and dissolution in water as much as possible. According to the pressurized hot water treatment, 20% by mass or less, further 10% by mass or less, particularly 5 based on the amount of lignin contained in the raw material. It can be suppressed to mass% or less.

The amounts of bamboo cellulose, hemicellulose, and lignin before and after the pressure hot water treatment can be analyzed by a known method. For example, bamboo materials before and after treatment are extracted with ethanol after soxsley extraction, hydrolyzed with sulfuric acid, hemicellulose and cellulose are quantified by analyzing constituent sugars such as glucol and xylose, and insoluble ones after sulfuric acid hydrolysis are used as lignin. A method of quantification can be mentioned.

In the present invention, the processed product obtained in the pressurized hot water treatment step is sent to the separation step. In the separation step, the treated product is separated into a solid residue and an extract.

The above extract contains potassium, chlorine, and metal extracted from bamboo, as well as hemicellulose decomposition products, lignin decomposition products, cellulose decomposition products, and other substances contained in bamboo, and is separately purified. It can be used effectively. Examples of the metal include aluminum, silicon, phosphorus, sulfur, calcium, chromium, manganese, iron, nickel, copper, zinc, sodium and magnesium. Organic substances include carboxylic acids such as formic acid, acetic acid and propionic acid, dicarboxylic acids such as oxalic acid, malonic acid, succinic acid and adipic acid, acetone, butanone, 2-pentanone, 2-hexanone, 2-heptanone and 2-octanone. Examples thereof include various organic substances such as ketones, aldehydes such as formaldehyde, acetic aldehyde, propion aldehyde, and butyl aldehyde, alcohols, and aromatic ring compounds.
The solid residue is mainly composed of cellulose from bamboo, and can be obtained as a solid having the same form as before the pressurized hot water treatment, including some residues such as lignin and hemicellulose that have not been extracted. .. Solid residues include metals and organics such as aluminum, silicon, phosphorus, sulfur, calcium, chromium, manganese, iron, nickel, copper, zinc, sodium and magnesium.

For the separation of the processed product, a known separator, specifically, a device such as a pressurized / normal pressure / vacuum filter, a centrifuge or the like is used without particular limitation.

If the pressurized hot water treatment device has the above-mentioned separation function, specifically, is an autoclave with a cage for putting an object to be treated and has a structure having a discharge port for an extract. The separation step can be carried out in the device.

The solid residue separated in the separation step can be further washed with water to remove potassium and chlorine contained in the attached extract, and the removal rate can be further improved. preferable. In washing with water, it is possible to use water having a temperature of 150 ° C. or lower, preferably 110 ° C. or lower. The water used for washing is preferably 2 to 50 parts by mass, particularly 5 to 30 parts by mass, and more preferably 10 to 30 parts by mass with respect to 1 part by mass of the dry weight of the solid residue.

Further, in the present invention, the potassium concentration and the chlorine concentration in the bamboo material and the solid content residue are the values measured by the method shown in the examples.

In the present invention, the solid residue obtained from the separation step has a significantly low concentration of potassium and chlorine contained therein, and is sent to the power generation step and used as a part or all of the boiler fuel in the thermal power generation facility of the step. By doing so, the corrosion of the device due to chlorine and the occurrence of coaching due to potassium are extremely effectively suppressed.

In the present invention, the thermal power generation facility is not particularly limited as long as it has a structure capable of burning solid residue, but a fluidized bed boiler in which the size of the fuel to be charged into the furnace is loosely restricted is particularly suitable.

In the present invention, the solid residue is preferably dried when it is supplied to the power generation step. The drying is preferably carried out so that the water content is 10% by mass or less, preferably 5% by mass or less. Further, a known dryer is used for such drying without particular limitation. Of course, it can be dried in the sun, or it can be dried in combination with the above-mentioned drying device.

Further, it is preferable to provide a crushing step for crushing the solid residue before or after the drying. As the apparatus used for the pulverization, a known pulverizer such as a pin mill, a hammer mill, a cutter mill, a ring mill, or a jet mill may be appropriately selected and used depending on the state of the solid residue. Further, a plurality of crushers may be combined. In crushing, the solid residue is in a state where it can be easily crushed in a state where the fibers of the bamboo material are dissolved due to the reduction of hemicellulose by the pressurized hot water treatment, so that the solid residue should be easily crushed. Can be done.

The size of the solid residue supplied to the boiler in the power generation process depends on the type of the boiler, but in the case of the fluidized bed boiler, the average major axis can be adjusted to 10 mm or less, and in the case of the stoker-fired boiler, it is 30 mm. It is preferable to adjust to the following size.

The solid residue is preferably used as a part of a boiler fuel such as coal. That is, the calorific value of the solid residue increases to about 20000 kcal / kg as a result of the enrichment of lignin by the pressure hot water treatment. However, since the calorific value is slightly inferior to the calorific value of coal, in order to maintain a sufficient calorific value in the boiler, for example, when the boiler fuel is coal, 0.1 is compared with the coal. It is preferably used in a proportion of about 70% by mass, preferably 1 to 50% by mass.

When the above coal is used as fuel, it is preferable to co-mill the solid residue with coal. As the crusher used for such co-grinding, a pin mill is preferably used, but other crushers can also be appropriately selected and used.

Further, in the case of the fluidized bed boiler, for example, the solid residue is generally charged directly into the furnace of the boiler.

FIG. 1 shows a typical flow sheet in which pressurized hot water treatment is performed in a batch manner in the method of the present invention.

According to FIG. 1, the bamboo material 1 is supplied to the crusher 3 and crushed into bamboo chips having an appropriate size, for example, an average major axis of 5 to 500 mm. Bamboo chips are supplied to the reactor 4 which performs the pressurized hot water treatment together with an appropriate amount of water 2. An autoclave equipped with a heater 5 is generally used for the reactor 4, and after adding water and bamboo chips, the reactor 4 is sealed and heated at a predetermined temperature by a heater provided in the reactor for a predetermined time. Although not shown, if the pressure inside the reactor is higher than the theoretical vapor pressure, a nitrogen pipe for pressurization is provided.

The solid residue and the extract taken out from the reactor are separated by a separator 6 represented by a centrifuge, the extract 7 is used for other purposes, and the solid residue is a dryer 8 equipped with a heater 9. It is dried under the specified conditions. Although not shown, it is preferable to provide a washing machine to wash the solid residue with water before drying it, and to drain the solid residue as necessary.

The solid residue after drying is adjusted to an appropriate size by the crusher 10 as needed, and is put into the furnace of the boiler of the power generation facility.

When the solid content residue of the present invention is co-fired with coal, the crusher 10 can use a coal crusher, and in that case, it is also preferable to co-crush with coal as described above. Is.

Although the example of the batch type is shown for the reactor 4, a continuous reaction can also be performed. For example, after the crusher, the bamboo is stored in a tank (bamboo storage tank), and when a certain amount of bamboo is stored, the bamboo storage tank is raised to the reaction pressure and gradually put into the reactor from above. It is also possible to take out the bamboo from under the reactor so that the bamboo in the reactor becomes almost constant and transfer it to the separator 6. The same may be performed for the separator 6 and later.

FIG. 2 shows a typical flow sheet in which the pressurized hot water treatment is continuously performed in the method of the present invention.

In the continuous mode shown in FIG. 2, it is preferable that the bamboo material 1 and water are transferred in a slurry state in order to improve the fluidity in the subsequent steps. Therefore, it is preferable that the bamboo material 1 and water 2 are put into the crusher 3 and wet-crushed to obtain, for example, a slurry containing bamboo material having an average major axis of less than 5 mm. The slurry obtained by the crusher is stored in the slurry storage tank 12, and a predetermined amount is supplied to the reactor 4 having a pressure-resistant structure by using a pressure pump.

The water slurry of bamboo material supplied to the reactor 4 moves in the reactor at a predetermined speed by adjusting the take-out amount by a valve provided in the take-out portion on the outlet side. The water slurry of the bamboo material is preheated by the preheater 13 as necessary, then heated to a predetermined temperature by the heater 5, and is treated with pressurized hot water.

The treated slurry continuously taken out from the reactor 4 is separated into a solid residue and an extract 7 by a separator 6 via a hopper 15. Further, as described with reference to FIG. 1, the solid residue separated by the separator 6 is washed with water and then dried by the dryer 8. Since the solid residue after drying is finely pulverized, it does not need to be crushed in particular, and is put into the furnace of the boiler of the power generation facility alone or together with coal.

Hereinafter, examples will be shown to more specifically explain the present invention, but the present invention is not limited to these examples.

In the examples and comparative examples, the concentrations of potassium and chlorine in the bamboo material and the solid residue were measured by the following methods.

After drying 100 g of the sample in an oven at 100 ° C. for 24 hours, if necessary, the sample was pulverized to an average major axis of 2 mm or less by a pin mill, and about 10 g of the obtained powder was analyzed by XRF (fluorescent X-ray analyzer). Chlorine concentration and potassium concentration were measured. In the case of Moso bamboo used in the examples, the above measurement results were a chlorine concentration of 3000 ppm and a potassium concentration of 5000 ppm.

The powder prepared by the above method was extracted by socksley with ethanol, cellulose / hemicellulose was hydrolyzed with sulfuric acid, and sugar was analyzed by HPLC (high performance liquid chromatography) to quantify cellulose, hemicellulose, and lignin. The quantification of hemicellulose and lignin in the extract was also performed by HPLC. In the case of Moso bamboo used in the examples, the above measurement results were 42% cellulose, 22% hemicellulose, and 31% lignin.

Example 1
Bamboo material cut from the bamboo grove of Moso bamboo was crushed with a crusher (hammer mill) (Ueno Sangyo Co., Ltd.) to obtain bamboo chips with an average major axis of 30 mm. 600 g (dry weight) of the bamboo chips was charged into an autoclave (manufactured by Pressure Resistant Glass Industry Co., Ltd.) having a capacity of about 2 L together with 1.2 liters of water, and pressurized to about 0.7 MPa with nitrogen. Pressurized water heat treatment was performed for 10 minutes at a temperature of 180 ° C. and a pressure of 2 MPa (theoretical vapor pressure of 180 ° C. + 1 MPa).

The processed product obtained in the above-mentioned pressurized water heat treatment step was separated into an extract and a solid residue by a filter. Further, the separated solid residue was washed with 4.8 L of hot water.

The extract contained 64 g of a hemicellulose decomposition product, 37 g of a lignin decomposition product, and 10 g of other substances.

The residue after washing was dried in an oven at 100 ° C. for 24 hours to obtain 210 g of solid content residue. This solid content residue was pulverized by a pin mill to an average major axis of 2.7 mm. At that time, the crushing energy could be reduced by about 20% as compared with the raw material bamboo chips, and crushing could be performed with a small load. The main component of the obtained solid residue was cellulose, which contained 65% by mass of cellulose, 29% by mass of lignin, and 4% by mass of hemicellulose. The potassium concentration of this solid residue was 20 ppm, and the chlorine concentration was 15 ppm.

The abundance of potassium and chlorine is far less than the amount of potassium and chlorine contained in the raw material bamboo and the coal used in the thermal power generation equipment. For example, when it is supplied to the furnace of a fluidized layer boiler, there is almost no problem due to these elements.

Examples 2 and 3 Comparative Examples 1 and 2
In Example 1, a solid residue was obtained in the same manner except that the treatment conditions in the pressurized hydrothermal treatment step were changed as shown in Table 1. The results are also shown in Table 1.

In addition, for comparison, Comparative Examples 1 and 2 in which the extraction conditions are changed are also shown in Table 1.

1 Bamboo material 2 Water 3 Crusher 4 Reactor 5 Heater 6 Separator 7 Extract 8 Dryer 9 Heater 10 Crusher 11 Power generation equipment 12 Slurry storage tank 13 Preheater 14 Cooler 15 Hopper

Claims (6)

The processed product obtained from the pressurized hot water treatment step of treating the bamboo material at a temperature of 150 to 220 ° C. for 0.05 to 5 hours in the presence of water, and the above-mentioned pressurized hot water treatment step is separated into a solid residue and an extract. The average of bamboo materials to be subjected to the pressurized hot water treatment, including the separation step and the power generation step in which the solid residue obtained from the separation step is used as a part or all of the boiler fuel in the thermal power generation facility. A power generation method having a major axis of 5 to 500 mm and having a crushing step of crushing the solid residue after the pressurized hot water treatment step and before the power generation step . The power generation method according to claim 1, wherein in the pressurized hot water treatment step, water is present in a ratio of 3 to 100 parts by mass with respect to 1 part by mass of bamboo material. The power generation method according to claim 1 or 2, wherein in the pressurized hot water treatment step, pressurization is performed at a pressure 0.01 to 2 MPa higher than the standard vapor pressure of water at the temperature . The power generation method according to any one of claims 1 to 3, wherein the chlorine concentration in the solid residue obtained from the separation step is 100 ppmw or less and the potassium concentration is 500 ppmw or less. The power generation method according to any one of claims 1 to 4, wherein in the power generation step, the boiler is a fluidized bed boiler. The power generation method according to any one of claims 1 to 5 , wherein in the crushing step, the solid residue is co-crushed with coal.

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