JPH1172203A - Method and equipment for utilizing energy of combustion gas and treating combustion gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable efficient utilization of the energy of combustion gas, to recover produced CO2 gas efficiently and compactly without releasing it into the atmosphere and also to suppress generation of dioxin or to decompose or remove harmful substances such as the dioxin and a sulfur oxide without releasing them into the atmosphere. SOLUTION: Either coal or organic waste pulverized respectively or both of them are mixed with water and slurry 11 is prepared. This slurry 11 is further mixed with water and kept in a supercritical or subcritical state under the presence of oxygen or air and either the coal or the organic waste in the slurry or both of them are combusted. The energy the combustion gas holds is utilized and the temperature of this combustion gas is lowered. The combustion gas of which the temperature is lowered is introduced into a settler 20 and the water 23 is formed in a lower layer and liquefied CO2 22 in an upper layer. The liquefied CO2 22 is recovered from the upper layer formed in the settler 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the combustion of coal or organic waste or a mixture thereof in a supercritical or subcritical state of water, utilizing the energy generated by the combustion, and being the main component of the combustion gas. The present invention relates to a method and an apparatus for recovering carbon dioxide as liquefied CO ₂ .

[0002]

2. Description of the Related Art Conventionally, fuels such as coal, petroleum, and LNG,
When combustible waste is combusted with air at high temperatures, harmful nitrogen oxides and sulfur oxides are generated,
Equipment for removing these from the combustion waste gas is required. Combustion waste gas also contains a large amount of CO ₂ gas,
It is required to reduce the emission to prevent global warming. From the viewpoint of fuel diversification, it has been proposed to use low-grade coal, organic waste, and the like as fuel. However, when these fuels are burned, harmful substances such as dioxin may be released. . There have been proposed methods of producing a clean high-energy gas by burning at a relatively low temperature (350 to 600 ° C.) where harmful nitrogen oxides are hardly generated (for example, JP-A-64-75587 and JP-A-64-58787). 64-75591). In these methods, water and oxygen or air are added to coal or an organic liquid fuel, and an oxidation exothermic reaction is performed in a subcritical or supercritical state of water.

[0003]

However, in the above-mentioned conventional method, the produced high-energy gas contains a large amount of CO ₂ gas, which has a problem that it is released to the atmosphere as it is. The high-energy gas is directly supplied to the gas turbine and used for power generation. However, the high-energy gas contains ash extracted from the supercritical water, and has a problem that it adheres to the blades of the turbine. SUMMARY OF THE INVENTION An object of the present invention is to efficiently utilize the energy of a combustion gas, to efficiently and compactly recover the generated CO ₂ gas without releasing it into the atmosphere, to use the energy of the combustion gas, and to treat the combustion gas. It is to provide a device. Another object of the present invention is to suppress the generation of dioxin or to efficiently decompose or remove harmful substances such as dioxins and sulfur oxides without releasing them to the atmosphere. It is to provide the device.

[0004]

The invention according to claim 1 is
As shown in FIG. 1, one or both of finely divided coal and organic waste and water are mixed with water to prepare a slurry 11, and the slurry 11 is further mixed with water to form oxygen or air. Burning either or both of the coal and organic waste in the slurry 11 in the supercritical or subcritical state in the presence of A step of lowering the temperature of the gas, a step of introducing the cooled combustion gas into the settler 20 to form water 23 in the lower layer and liquefied CO ₂ 22 in the upper layer, and a step of liquefying C 2 from the upper layer formed in the setter 20.
And a method for treating combustion gas, including a step of recovering O ₂ 22. The gas burned by bringing the slurry 11 into a supercritical state or a subcritical state has high energy, and this energy is used. As a result of this energy utilization, CO ₂ and moisture contained in the cooled combustion gas are liquefied by the settler 20 to separate and form water 23 in the lower layer and liquefied CO ₂ 22 in the upper layer. By liquefying and recovering CO ₂ , CO ₂ generated by combustion is reduced.
_{The two} gases can be collected efficiently and compactly without releasing them into the atmosphere and without requiring a large tank. In the present invention, the supercritical state means a temperature range of 374 ° C. or more and 600 ° C. or less and a pressure range exceeding 220 atm, and the subcritical state means a temperature range of 200 ° C. or more and less than 374 ° C.
It means the pressure range from atm to 220 atm.

A second aspect of the present invention is the invention according to the first aspect, wherein an alkaline aqueous solution is added when the slurry 11 is prepared or when one or both of coal and organic waste in the slurry 11 is burned. Is the way. If there is a possibility that dioxin may be generated by the combustion of organic waste, etc., chlorine (C) is added by adding an alkaline aqueous solution at the time of preparing a slurry or burning organic waste or the like in the slurry.
l), the generation of dioxin is suppressed, and even when the generation cannot be suppressed, dioxin can be decomposed with high efficiency in a supercritical state.

A third aspect of the present invention is the invention according to the first or second aspect, wherein water 23 is recovered from a lower layer formed in the setra 20 as shown in FIG.
This is a treatment method including a step of adding slaked lime slurry to the water. Slaked lime slurry (Ca (O
H) ₂ ), the SOx dissolved in the water 23 becomes C
It is settled as aSO _4, and harmful substances can be removed before wastewater treatment.

As shown in FIG. 1, a fourth aspect of the present invention is a slurry tank 10 for storing a slurry 11 in which one or both of finely divided coal and organic waste and water are mixed. A heater 15 for heating the slurry 11 supplied from the heater 10 and water further mixed with the slurry; and heating the slurry 11 and the water supplied from the heater 15 in the supercritical state or subcritical state in the presence of oxygen or air. A reactor 16 which is brought to a critical state and burns either or both of the coal and organic waste in the slurry.
A gas-solid separator 17 that removes cinders in the combustion gas generated in the reactor 16; and a heat utilization device 18 that uses energy by the combustion gas from which the cinders have been removed and lowers the temperature of the combustion gas. A settler 20 for liquefying the combustion gas cooled down by the heat utilization device 18 and separating it vertically into liquefied CO ₂ 22 and water 23, and a liquefaction for collecting and storing the liquefied CO ₂ 22 from the upper layer formed in the settler 20 A CO ₂ tank 25 and a combustion gas energy utilization and combustion gas processing apparatus. The energy of the gas burned in the reactor 16 is effectively used by the heat utilization device 18, and liquefied CO ₂ 22 is formed from the cooled combustion gas in the setra 20, which is efficiently recovered.

The invention according to claim 5 is the invention according to claim 4, wherein as shown in FIG. 1, water 23 is recovered and stored from the lower layer formed in the settler 20, and the slaked lime slurry is mixed with the water 23. This is a processing apparatus provided with a thickener 26 for sedimenting sulfide contained in the water 23. When the slaked lime slurry is mixed with the water 23 collected by the thickener 26 and allowed to stand,
SOx dissolved in the water 23 becomes CaSO ₄ and settles, and harmful substances can be removed before wastewater treatment.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. As shown in FIG. 1, a slurry tank 10 contains pulverized coal as a starting material, water as a solvent, and organic waste pulverized by pulverization or pulverization.
A slurry 11 mixed with an alkaline aqueous solution is stored.
Numeral 12 is a blade for stirring these starting materials. Examples of coal include grass coal, lignite, sub-bituminous coal, bituminous coal, anthracite, etc.
Sawdust, combustible waste and the like are exemplified as the organic waste, and aqueous solutions such as NaOH and KOH are exemplified as the alkaline aqueous solution. Coal and organic waste are less than several mm in advance,
Preferably, it is pulverized to a particle size of 300 μm or less according to the capacity of the pump. Water preferably has a slurry concentration of 5-6.
0% by weight is added. If the slurry concentration is less than 5% by weight, the liquefaction efficiency is poor, and if it exceeds 60% by weight, the slurry lacks fluidity and becomes difficult to handle. The slurry concentration is more preferably 40 to 55% by weight. In addition, when there is a possibility that dioxin may be generated by the combustion of organic waste, the alkaline aqueous solution traps chlorine (Cl) generated by burning in a supercritical state or a subcritical state, thereby suppressing the generation of dioxin. Or act to decompose with high efficiency.

The slurry discharged from the slurry tank 10 is pumped by a pump 13. As will be described later, the high pressure water, which is pumped by the pump 14 and preheated as necessary by the heat of the combustion gas, and this slurry are mixed and then sent to the heater 15. Here, the amount of high-pressure water is adjusted so that the temperature becomes 400 to 600 ° C. depending on the amount of heat generated by underwater combustion. The heater 15 heats the mixture of the slurry and water to about 150 to 350 ° C. prior to bringing the mixture of the slurry and water into a supercritical state or a subcritical state. The mixture of the slurry and water heated by the heater 15 is supplied to the reactor 16. The reactor 15 is further supplied with liquefied oxygen or air, where combustion takes place. By the heat of the combustion reaction, the slurry reaches a supercritical state or a subcritical state (200 to 600 ° C., 100 atm or more). The supercritical state of this slurry is
For example, when the temperature is 400 ° C., the pressure is 221 to 300.
Retained in atm. If the pressure is below the lower limit of the pressure range, the reaction is slow and the conversion efficiency is not good. If the pressure exceeds the upper limit of the pressure range, the reactor is overloaded, which is not efficient. A solid-gas separator 17 is provided on the discharge side of the combustion gas of the reactor 16.
Is provided. In this embodiment, the solid-gas separator 17 is
A cyclone 17a for removing the combustion gas in the combustion gas generated in the reactor 16, and a filter 17 for removing the combustion gas in the combustion gas remaining without being completely removed by the cyclone 17a.
b. The combustion gas discharged from the filter 17b is guided to a heat utilization device 18 for utilizing the energy of the combustion gas and lowering the temperature of the combustion gas.

In the heat utilization device 18, the energy of the combustion gas is used, for example, for rotating a turbine for power generation, for district heating of a local government, or for a heat source of a hot spring or a heated water pool. Used for etc. When turning the turbine for power generation, it is preferable not to supply combustion gas directly to the turbine, but to turn the turbine with another heat medium via a heat exchanger. As a result of using this heat energy,
The temperature of the combustion gas passing through the heat utilization device 18 decreases. When the use of heat energy is performed in a closed combustion gas flow path, the pressure of the combustion gas is maintained, but the use of this heat energy does not necessarily have to be performed in a closed combustion gas flow path. Since the temperature of the combustion gas is gradually lowered, when the temperature of the combustion gas is not lowered to the temperature at which CO ₂ in the combustion gas is liquefied when the combustion gas is introduced into the later-described settler 20, the combustion is performed by the secondary heat utilization device. The gas is passed through, where the combustion gas is further cooled. In this embodiment, the combustion gas in the first heat utilization device 18 is 400 to 600 ° C. to 2 ° C.
The temperature is lowered to 00 ° C., but the pressure is maintained at 221 to 300 atm. This temperature and pressure are determined by the amount of CO
_Since the liquefaction of ₂ is still high, a heat exchanger 19 for preheating water for mixing with the slurry is provided as a secondary heat utilization device, and the combustion gas is passed through the heat exchanger 19. By passing through the closed combustion gas flow path in the heat exchanger 19, the temperature of the combustion gas decreases from 200 ° C. to 60 ° C., and the pressure is maintained at 221 to 300 atm. On the other hand, the 30 ° C. water supplied to the heat exchanger 19 is
After heating to 150 ° C., the slurry is mixed with the slurry fed as described above and supplied to the heater 15.

The combustion gas that has passed through the heat exchanger 19 is led to a settler 20. The settler 20 has a closed large cross-sectional area and is configured to allow the liquid to be contained to stand still. When the combustion gas that has passed through the heat exchanger 19 and cooled to 60 ° C. is introduced into the settler 20, the moisture and the CO ₂ gas in the combustion gas are liquefied. The density of liquefied CO ₂ gas is about 0.5 g / cm ³ and the density of water is about 1 g
/ Cm ³ , so that liquefied CO
₂ is formed by separating water in the lower layer. When air is supplied to the mixer 13 and mixed with the slurry instead of oxygen, the N ₂ gas 24 is liquefied CO ₂ 22
The gas is stored as gas on the upper side, and is released to the atmosphere from inside the setra 20 by opening a discharge valve (not shown). A discharge pipe 20a for liquefied CO ₂ 22 formed in the setra 20 is provided on the upper side wall of the setra 20, and this discharge pipe 20a is connected to a tank 25 for storing liquefied CO ₂ . Drain pipe 20b on the lower side wall of setra 20
The drainage pipe 20 b is connected to the thickener 26. Thickener 26 stores water 23 formed in setra 20. If harmful substances such as SOx are dissolved in the water 23 due to the combustion of the organic waste, slaked lime slurry (Ca (OH) ₂ ) is added to the thickener 26 and mixed to settle the SOx to CaSO ₄ . . The supernatant water of this thickener 26 is further treated as wastewater.

[0013]

As described above, the present invention provides a method for slurrying coal or organic waste and burning it in a supercritical or subcritical state in the presence of oxygen and utilizing the energy of the combustion gas. Has the following excellent effects. (1) The generated CO ₂ gas can be efficiently recovered without lowering the energy use efficiency without releasing it to the atmosphere. Further, since the recovered CO ₂ is stable liquefied CO ₂ , it can be compactly recovered, and its storage and handling are easy. As a result, the emitted CO ₂ is contained to prevent global warming. (2) Low-grade coal, organic waste,
Even if fuel containing harmful substances such as combustible waste is used,
Release of harmful substances such as x and NOx into the atmosphere can be suppressed or reduced. (3) Since harmful substances such as dioxin or sulfur oxide can be efficiently decomposed or removed, it is possible to reduce the size of a processing apparatus which can be easily used even by a small-scale local government. (4) Since the processing apparatus can be configured by a combination of small and simple apparatuses, the process can be downsized and simplified as compared with the conventional one.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus for performing energy utilization and processing of a combustion gas according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Slurry tank 11 Slurry 15 Heater 16 Reactor 17 Solid-gas separator 18 Heat utilization device 20 Setra 25 Liquefied CO ₂ tank 26 Thickener

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10J 3/48 C10J 3/48

Claims (5)

[Claims] 1. A slurry obtained by mixing one or both of finely divided coal and organic waste and water with water.
And preparing the slurry (11) further mixed with water to maintain a supercritical state or a subcritical state in the presence of oxygen or air, and either the coal or the organic waste in the slurry (11). A step of burning one or both of them; a step of using the energy held by the combustion gas and lowering the temperature of the combustion gas; and a step of introducing the temperature-reduced combustion gas into a setra (20) to form water in a lower layer.
(23) a step of forming liquefied CO ₂ (22) in the upper layer, and a step of recovering liquefied CO ₂ (22) from the upper layer formed in the settler (20). Processing method. 2. The preparation of the slurry (11) or the slurry (11)
The treatment method according to claim 1, wherein an alkaline aqueous solution is added at the time of burning one or both of the coal and the organic waste therein. 3. Water (23) from the lower layer formed in the setra (20)
The method according to claim 1 or 2, further comprising the step of adding slaked lime slurry to the collected water (23) after collecting the water. 4. A slurry (11) in which one or both of finely divided coal and organic waste and water are mixed.
A slurry tank (10) for storing water, a heater (15) for heating the slurry (11) supplied from the tank (10) and water further mixed with the slurry, and a heater (15) supplied from the heater (15). A reactor (16) in which the heated slurry (11) and water are brought into a supercritical or subcritical state in the presence of oxygen or air to burn either or both of the coal and organic waste in the slurry (11) ), A solid-gas separator (17) for removing the cinders in the combustion gas generated in the reactor (16), and utilizing the energy of the combustion gas from which the cinders are removed and lowering the temperature of the combustion gas A heat utilization device (18), and a settler (20) that liquefies the combustion gas cooled by the heat utilization device (18) and vertically separates it into liquefied CO ₂ (22) and water (23).
When the settler (20) the formed upper layer from liquefied CO ₂ (22) was collected in store liquefied CO ₂ tank (25) and the processing unit of energy utilization and combustion gas of the combustion gas having a. 5. Water (23) from the lower layer formed in the setra (20)
Thickener (2) for collecting and storing and mixing slaked lime slurry with the water (23) to precipitate sulfide contained in the water (23).
The processing apparatus according to claim 4, further comprising (6).