JP5047056B2 - Method for falling tar decomposition system and tar decomposition system - Google Patents

Description

  The present invention relates to a method for bringing down a tar decomposition system having a reactor having a catalyst layer for decomposing a tar content contained in a gasification gas. It also relates to the tar decomposition system.

  Gasification technology has attracted attention as a technology for converting energy efficiently from waste (organic waste) containing organic matter such as wood chips and sewage sludge and biomass fuel. It is possible to generate power by burning the gas generated by gasification in an internal combustion engine such as a gas engine or a gas turbine, and the power generation efficiency is to directly burn fuel to generate steam. It has a feature of higher efficiency by a boiler power generation system that generates power by using a power source (Patent Document 1).

  However, the generated gas generated from the gasification equipment contains dust, tar, and other harmful corrosive substances / contaminants. If it is directly input to the power generation equipment such as a gas engine, the combustion equipment, piping, nozzles, Other problems such as clogging and corrosion occur.

  Therefore, the gasification gas generated from the gasification facility needs to be detoxified. That is, as shown in FIG. 2 of Patent Document 1, the gasification gas generated from the gasification facility 1 is collected by the high-temperature dust collection facility 2, and the dust in the gasification gas is removed. It is introduced into a tar decomposition facility 3 which is a reactor equipped with a decomposition catalyst layer 3a, and the tar content in the gasification gas is decomposed. Thereafter, the gasification gas is cooled in the gas cooling facility 4, and the low-temperature dust collection facility ( (Not shown) and the like, and further detoxified (for example, Patent Document 1).

  In addition, when the gasification treatment by the gasification equipment is finished, air flows in, so that the catalyst component is reduced nickel or carbon deposited on the catalyst surface (generally, carbon is deposited on the catalyst surface with use). ) Burns and the temperature rises. As a result, the catalyst may deteriorate, or the internal structure of the tar decomposition facility may be damaged. Therefore, a configuration is known in which the catalyst in the reactor of the tar decomposition facility is discharged from the reactor at the time of the gasification process, and the discharged catalyst is made into a non-oxidizing atmosphere (see Patent Document 2).

JP-A-11-21565 JP 2007-99927 A (Claim 5)

  However, since the tar decomposition system of Patent Document 2 is configured to discharge the catalyst from the reactor and store it in a non-oxidized state when the operation is stopped, the catalyst discharging mechanism and the catalyst are charged again into the reactor. Means are required and the apparatus configuration is complicated. Moreover, since it is necessary to fill the catalyst when the system is in operation, work for that is necessary, and preparation time until the system is in operation is required.

  Conventionally, a metal catalyst such as Ni has been used as a catalyst. This metal catalyst such as Ni is used in the reduction zone during its catalytic action. However, if the catalyst is cooled in the reduced state when the gasification process is finished (or also referred to as “falling”), it is necessary to raise the temperature in the inert gas when the system is started again. For this reason, conventionally, the temperature of the catalyst has been raised in an externally heated reactor (for example, a burner) or a heat exchanger for heating an inert gas.

  In addition, when the catalyst is stored in a reduced state as in the past, if the catalyst comes into contact with the atmosphere for some reason and oxidation begins, the combustion reaction proceeds at once due to self-heating, and the catalyst is thermally deteriorated. It was necessary to store in an inert gas.

  Therefore, the present invention has been made in view of the above-mentioned problems of the prior art, and its purpose is to eliminate the combustion reaction due to oxidation of the catalyst by oxidizing the catalyst at the fall of the tar decomposition system. It is another object of the present invention to provide a method for starting a tar decomposition system that can perform oxidation treatment with a simpler equipment configuration. Moreover, it is providing the tar decomposition system.

The above-mentioned subject is achieved by the invention described in each claim. That is, the method for lowering the tar decomposition system according to the present invention is a method for lowering the tar decomposition system having a reactor having a catalyst layer for decomposing the tar content contained in the gasification gas,
The catalyst layer is cooled in an inert gas atmosphere, and the catalyst is lowered by oxidation treatment.

  According to this configuration, the catalyst layer can be cooled in an inert gas atmosphere, and the catalyst can be lowered by oxidation treatment. Therefore, a mechanism for discharging and refilling the catalyst from the reactor as in the prior art is not required, and the apparatus configuration can be simplified. In addition, after the catalyst layer is cooled in an inert gas atmosphere state, the reduced metal catalyst can be suitably oxidized (combustion reaction process), and the catalyst can be prevented from deteriorating and lowered. In addition, since the oxidized metal catalyst does not need to be stored in an inert gas atmosphere environment, it can be stored as it is, thus preventing a combustion reaction due to contact with the atmosphere as in the conventional case, resulting in equipment fires. Absent. Further, it is not necessary to raise the temperature in an inert gas as in the prior art, and the temperature can be raised by sensible heat of the combustion gas or the burner at the time of restart.

  In the present invention, the inert gas supplied to the catalyst layer of the reactor is circulated to the reactor through a cooling means for cooling the inert gas.

  According to this configuration, since the inert gas supplied to the catalyst layer of the reactor is circulated to the reactor via the cooling means for cooling the inert gas, the inert gas can be used efficiently and inert. Gas usage cost can be reduced. The inert gas is cooled and dehumidified by the cooling means.

  In the present invention, the moisture concentration of the inert gas is 5% or less.

  According to this configuration, the moisture concentration of the inert gas can be reduced to 5% or less, which is preferable because sintering deterioration (deterioration due to aggregation) due to hydration of the catalyst by moisture can be suppressed. By cooling the inert gas with the cooling means as described above and dehumidifying it, the moisture concentration of the inert gas can be reduced to 5% or less.

Examples of the inert gas include combustion exhaust gas, N ₂ and CO ₂ gas. Examples of the combustion exhaust gas include combustion exhaust gas when fuel is burned in a gasification facility, combustion exhaust gas discharged from a gas utilization facility, and the like. Examples of the catalyst include metal-based catalysts, such as nickel-based metal catalysts or composite oxide reforming catalysts containing nickel, magnesia, and calcia.

  In the present invention, the catalyst layer is cooled to 700 ° C. or lower in an inert gas atmosphere.

  According to this configuration, the metal-based catalyst can be prevented from being thermally deteriorated by cooling the metal-based catalyst to 700 ° C. or lower and then performing oxidation treatment (combustion reaction treatment). Moreover, it is preferable to cool the temperature of a metal catalyst to the range of 500 to 700 degreeC.

  In the present invention, the catalyst is oxidized using a catalyst oxidation gas having an oxygen concentration of 1% or less as the oxidation treatment of the catalyst.

  According to this configuration, since the catalyst oxidation treatment can be performed using the catalyst oxidation gas having an oxygen concentration of 1% or less, it is possible to control the combustion reaction not to be performed at once. When the oxygen concentration exceeds 1%, the heat of oxidation is larger than the heat removal by the inert gas of the catalyst, which is not preferable because the catalyst is thermally deteriorated. Examples of the catalytic oxidation gas include air, oxygen, high-concentration oxygen gas, and the like.

  In the present invention, the catalyst is oxidized so that the temperature of the catalyst layer does not exceed 800 ° C. when the catalyst is oxidized.

  According to this configuration, in the oxidation treatment of the catalyst, the oxidation treatment can be controlled so that the temperature of the catalyst layer does not exceed 800 ° C. When the temperature of the catalyst layer exceeds 800 ° C., the thermal deterioration of the catalyst becomes severe, which is not preferable. Moreover, it is preferable to control the oxidation treatment so that the temperature of the catalyst layer is suppressed to 500 ° C. to 700 ° C., which is lower than 800 ° C. The temperature control of the catalyst layer is performed by providing a low-temperature inert gas. Moreover, when the temperature of a catalyst layer is less than 500 degreeC, since a catalyst is not fully oxidized, it is unpreferable.

In addition, the tar decomposition system of the present invention is
A tar cracking system having a reactor equipped with a catalyst layer for cracking tar content contained in a gasification gas,
An inert gas supply means for supplying an inert gas to the catalyst layer;
Catalyst oxidation gas supply means for supplying a catalyst oxidation treatment gas for oxidizing the catalyst to the catalyst layer;
Temperature measuring means for measuring the temperature of the catalyst layer;
Oxygen concentration measuring means for measuring the oxygen concentration of the catalyst oxidizing gas supplied by the catalyst oxidizing gas supply means;
When the tar decomposition system is brought down, the catalyst layer is brought into an inert gas atmosphere by the supply of the inert gas by the inert gas supply means, and the temperature measured by the temperature measurement means is set to 700 ° C. or less. Control means for controlling the supply of the catalyst oxidation gas by the catalyst oxidation gas supply means and oxidizing the catalyst, and
The control means controls the oxygen concentration of the catalyst oxidizing gas to be 1% or less during the oxidation treatment of the catalyst, and controls the temperature measured by the temperature measuring means. The temperature is controlled so as not to exceed 800 ° C.

  In the present invention, the inert gas supplied to the catalyst layer of the reactor is circulated to the reactor via a cooling means for cooling the inert gas.

  The operational effects of these tar decomposition systems are the same as those described above.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic flow of a tar decomposition system according to an embodiment of the present invention.

  The tar decomposition system 2 treats a tar component in a gasification gas (about 800 to 900 ° C.) generated by a gasification facility 1 such as a fluidized bed gasification furnace or a circulating fluidized bed gasification furnace with a catalyst. The tar decomposition system 2 includes a reactor 2a having a catalyst layer. The catalyst is preferably a nickel-based metal catalyst, more preferably a composite oxide reforming catalyst containing nickel, magnesia and calcia.

  Although not shown in FIG. 1, dust and the like in the gasification gas are collected by the high-temperature dust collection equipment through a high-temperature dust collection equipment composed of a ceramic filter or the like between the gasification equipment 1 and the tar decomposition system 2. You may comprise so that dust may be removed.

  From the gasification gas introduced into the tar decomposition system 2, the tar in the gasification gas is decomposed by the catalyst. Thereafter, the gasified gas is supplied to the gas cooling facility 40, cooled, sent to a low-temperature dust collection facility (not shown), etc., and appropriately charged with a chemical, neutralized, and rendered harmless. Thereafter, the gasified gas is supplied to the gas utilization facility 3 and provided for combustion or the like.

  In the embodiment of FIG. 1, the operation of the gasification facility 1 is stopped, and a method of falling the tar decomposition system 2 will be described. The system in FIG. 1 is configured to use the combustion exhaust gas of the gasification facility 1 as an inert gas.

(1) The gasification operation of the gasification facility 1 is switched to the combustion operation. The combustion exhaust gas in which the biomass fuel is completely burned by the combustion operation is discharged from the gasification facility 1. The discharged combustion exhaust gas passes through a pipe (not shown), flows into the tar decomposition system 2, is then cooled by the gas cooling facility 40, the valve 33 is opened, the valve 32 is closed, and the pushing fan 50 is operated. The cooled combustion exhaust gas is circulated to the tar decomposition system 2 according to the circulation path line P. Since the combustion exhaust gas is cooled by the gas cooling facility 40, the temperature of the catalyst layer of the reactor 2a is lowered. If the amount by which the combustion exhaust gas is filled in the circulation path line P is secured, the combustion operation of the gasification facility 1 can be stopped, the exhaust of the combustion exhaust gas can be stopped, and the valve 31 can be closed. Further, as another embodiment, the combustion operation of the gasification facility 1 can be stopped after a predetermined time has elapsed, the discharge of combustion exhaust gas can be stopped, and the valve 31 can be closed. Further, as another embodiment, when the temperature of the catalyst layer measured by the temperature measuring device 21 starts to decrease, the combustion operation of the gasification facility 1 is stopped, the discharge of the combustion exhaust gas is stopped, and the valve 31 is closed. it can. As another embodiment, when oxygen O ₂ is generated in the combustion exhaust gas, the combustion operation of the gasification facility 1 can be stopped, the exhaust of the combustion exhaust gas can be stopped, and the valve 31 can be closed. The above series of controls may be executed by the control device 20.

  (2) The control device 20 acquires the temperature of the catalyst layer from the temperature measuring device 21, and opens the valve 23 when the temperature of the catalyst layer becomes 700 ° C. or lower, or preferably 500 ° C. or higher and 700 ° C. or lower. The atmosphere (corresponding to catalytic oxidation gas) flows into the circulation path line P. The inflow amount of the atmosphere is controlled by the control device 1. For example, the oxygen concentration measuring device 22 is installed in the circulation path line P, and is configured to measure the oxygen concentration of the atmosphere flowing through the circulation path line P and combustion exhaust gas (hereinafter referred to as circulation gas). The control device 1 controls the inflow amount of the atmosphere so that the oxygen concentration measured by the oxygen concentration measuring device 22 is 1% or less with respect to the circulating gas. A known measuring device can be used for the temperature measuring device 21 and the oxygen concentration measuring device 22.

  (3) In addition, the control device 20 controls the inflow amount of the atmosphere so that the oxygen concentration is 1% or less with respect to the circulating gas, and at the same time acquires the temperature of the catalyst layer from the temperature measuring device 21, and the temperature is The cooling capacity of the gas cooling facility 40 is controlled so that the temperature is less than 800 ° C., more preferably 700 ° C. or less, and even more preferably 500 ° C. or more and 700 ° C. or less. Moreover, in addition to the structure which controls the cooling capacity of the gas cooling equipment 40, or independently, the inflow amount of air can be controlled so that the temperature range of 700 ° C. or less can be maintained.

  (4) Moreover, the control apparatus 20 acquires the moisture value measured by the moisture measuring device (not shown) which measures the water | moisture content of the combustion exhaust gas or circulating gas cooled with the gas cooling equipment 40, and combustion exhaust gas or circulating gas The cooling capacity of the gas cooling equipment 40 is controlled so that the moisture value of the gas cooling equipment is 5% or less.

  (5) When the oxidation of the catalyst is completed, the control device 20 discharges the circulating gas in the circulation path line P from a discharge path (not shown) in order to end the oxidation process. Further, as the discharge path, for example, the valve 32 may be opened and discharged to the gas utilization facility. The timing for completing the oxidation of the catalyst can be realized by monitoring the amount of decrease in the measured oxygen concentration (consumption of oxygen) and the point in time when the temperature rise of the catalyst disappears.

  In the above embodiment, the temperature measuring device 21 (corresponding to the temperature measuring means) may be provided in the catalyst layer or on the downstream side of the catalyst layer in order to accurately grasp the temperature in the catalyst layer. You may comprise so that the temperature of several places can be measured. Further, the temperature measuring device 21 may be a contact thermometer or a non-contact thermometer.

  Further, the inert gas and the catalytic oxidation gas may be supplied to the catalyst layer using the same pipe, or may be supplied through different pipes.

  The control device 20 (corresponding to the control means) is configured by an information processing device, firmware, a dedicated circuit, or the like. In the case of the information processing device, a program describing a control procedure, a memory for storing the program, and an arithmetic unit It is realized by cooperation with hardware resources such as a CPU and main memory.

(Another embodiment)
The falling method of the tar decomposition system 2 of the embodiment of FIG. 2 is configured to use nitrogen gas as an inert gas.

  (1) The gasification operation of the gasification facility 1 is stopped and the valve 31 is closed. The control device 20 opens a valve for nitrogen gas and causes the nitrogen gas to flow into the circulation path line P. The amount of inflow is such that it circulates by flowing into the piping and various facilities of the circulation path line P. Nitrogen gas is preferably flown into the front stage of the gas cooling facility 40, but may be flowed into the piping of another circulation pass line P. Before or after the inflow of nitrogen gas, the valve 32 is closed and the valve 33 is opened. Nitrogen gas introduced by the pushing fan circulates in the circulation path line P.

  (2) The control device 20 acquires the temperature of the catalyst layer from the temperature measuring device 21, and opens the valve 23 when the temperature of the catalyst layer becomes 700 ° C. or lower, or preferably 500 ° C. or higher and 700 ° C. or lower. Then, high-concentration oxygen gas (corresponding to catalytic oxidation gas) flows into the circulation path line P. The inflow amount of the high concentration oxygen gas is controlled by the control device 1. For example, the oxygen concentration measuring device 22 is installed in the circulation path line P, and is configured to measure the oxygen concentration of high-concentration oxygen gas and nitrogen gas (hereinafter referred to as circulation gas) flowing through the circulation path line P. The control device 1 controls the inflow amount of the high concentration oxygen gas so that the oxygen concentration measured by the oxygen concentration measuring device 22 is 1% or less with respect to the circulating gas. A known measuring device can be used for the temperature measuring device 21 and the oxygen concentration measuring device 22.

  (3) Moreover, the control device 20 acquires the temperature of the catalyst layer from the temperature measuring device 21 at the same time as controlling the inflow amount of the high concentration oxygen gas so that the oxygen concentration becomes 1% or less with respect to the circulating gas. The cooling capacity of the gas cooling facility 40 is controlled so that the temperature falls below 800 ° C., more preferably below 700 ° C., and even more preferably between 500 ° C. and below 700 ° C. Moreover, in addition to the structure which controls the cooling capacity of the gas cooling equipment 40, or independently, the inflow amount of the high concentration oxygen gas can be controlled so that the temperature range of less than 700 ° C. can be maintained.

  (4) Moreover, the control apparatus 20 acquires the moisture value measured by the moisture measuring device (not shown) which measures the water | moisture content of the nitrogen gas or circulating gas cooled with the gas cooling equipment 40, and nitrogen gas or circulating gas The cooling capacity of the gas cooling equipment 40 is controlled so that the moisture value of the gas cooling equipment is 5% or less.

  (5) When the oxidation of the catalyst is completed, the control device 20 discharges the circulating gas in the circulation path line P from a discharge path (not shown) in order to end the oxidation process.

(Experimental example 1)
In the system shown in FIG. 2, the temperature change of the nickel-based metal catalyst when the set value of the oxygen concentration was varied was evaluated. The cooled nitrogen gas was flowed into the catalyst layer and the temperature was adjusted to 600 ° C., and then high-concentration oxygen gas was flowed under the following conditions. The oxygen concentration of the circulating gas is 0.8% (condition 1), 1% (condition 2), 1.2% (condition 3), 2% (condition 4), 3.5% (condition 5) with respect to the circulating gas. As a result of evaluating the temperature change of the catalyst when it was changed to), under the conditions 1 and 2, the catalyst could be oxidized while suppressing the temperature change of the catalyst within 700 ° C. On the other hand, in the cases of conditions 3, 4, and 5, the higher the oxygen concentration, the more rapidly the temperature of the catalyst increased, and the catalyst temperature could not be controlled below 800 ° C.

  In addition, as a result of installing the temperature measuring device in the upper layer (circulation gas inlet) and the lower layer (outlet) of the catalyst layer under the above conditions, the measurement result of the temperature measuring device installed in the upper layer of the catalyst layer is better in any condition. The result was severe temperature fluctuation.

(Experimental example 2)
Catalytic activity K / K ₀ (total reaction rate ratio after oxidation treatment (K)) after the nickel catalyst exposed to the gasification gas is purged with nitrogen gas and oxidized under an oxygen concentration of 1% And the overall reaction rate (K ₀ ) ratio of the catalyst before use. The case where the moisture concentration of nitrogen gas and the oxidation treatment temperature were changed was evaluated. As a result, under the condition where the water concentration was 0%, the catalyst activity K / K ₀ was about 0.9 and there was almost no change in the temperature range of the catalyst during oxidation treatment from 500 ° C. to 700 ° C. Under the condition of a moisture concentration of 5%, the catalyst activity K / K ₀ decreased from about 0.85 to about 0.75 in the temperature range of the catalyst during the oxidation treatment of 500 ° C. or more and 700 ° C. or less. Further, under the condition where the water concentration was 20%, the catalyst activity K / K ₀ decreased from about 0.75 to about 0.6 in the temperature range of the catalyst during the oxidation treatment of 500 ° C. or more and 700 ° C. or less. From the above results, it was found that the catalyst activity decreased as the oxidation treatment temperature was higher and the moisture concentration in the inert gas to be purged was higher. This is thought to be due to thermal degradation at high temperatures and promotion of sintering by water vapor.

  From the results of the above experimental examples, it was found that it is important to oxidize the catalyst at an oxygen concentration of 1% or less and to reduce the moisture concentration of the inert gas to 5% or less and to avoid oxidation treatment in a high temperature range. . Moreover, it turned out that catalyst activity deterioration can be suppressed suitably by oxidizing a catalyst on suitable conditions.

(Other embodiments)
(1) In the above embodiment, the gasification facility may be a gasification melting furnace or a carbonization / dry distillation facility, and is not particularly limited.
(2) In the above embodiment, FIGS. 1 and 2 illustrate the example in which the temperature measuring device 21 is provided at a substantially intermediate position with respect to the gas flow direction of the catalyst layer, but instead the temperature measuring device 21 is You may provide in the exit side of a catalyst layer. However, when the temperature measuring device 21 is provided not only in the catalyst layer but also on the outlet side of the catalyst layer, hydrocarbon gas such as ethane or ethylene contained in the gasification gas is decomposed by the catalyst by an endothermic reaction, and the catalyst temperature is increased. It is preferable that the temperature of the catalyst can be increased when the decrease in the temperature is caused.
(3) As gasification gas applicable to this invention, the gasification gas etc. which were produced | generated by burning various solid fuel, industrial waste, etc. other than various organic wastes are mentioned.

Schematic flowchart showing a tar decomposition system according to an embodiment of the present invention. Schematic flowchart showing a tar decomposition system according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gasification equipment 2 Tar decomposition system 2a Reactor 3 Gas utilization equipment 20 Control apparatus 21 Temperature measuring device 22 Oxygen concentration measuring device 23 Valve 31, 32, 33 Valve 40 Gas cooling equipment 50 Pushing fan P Circulation pass line

Claims (8)

A method for deactivating a tar decomposition system having a reactor having a catalyst layer for decomposing a tar content contained in a gasification gas,
A method for starting a tar decomposition system, wherein the catalyst layer is cooled in an inert gas atmosphere, and the catalyst is subjected to an oxidation treatment to start up.   The start-up of the tar decomposition system according to claim 1, wherein the inert gas supplied to the catalyst layer of the reactor is circulated to the reactor through a cooling means for cooling the inert gas. Method.   The method for starting up a tar decomposition system according to claim 1 or 2, wherein the catalyst layer is cooled to 700 ° C or lower in an inert gas atmosphere.   4. The tar decomposition system according to claim 1, wherein the catalyst is oxidized using a catalyst oxidation gas having an oxygen concentration of 1% or less as the oxidation treatment of the catalyst. 5. Falling method.   5. The method for bringing down the tar decomposition system according to claim 1, wherein the catalyst layer is oxidized so that the temperature of the catalyst layer does not exceed 800 ° C. 5.   6. The method for starting up a tar decomposition system according to claim 1, wherein the moisture concentration of the inert gas is 5% or less. A tar cracking system having a reactor equipped with a catalyst layer for cracking tar content contained in a gasification gas,
An inert gas supply means for supplying an inert gas to the catalyst layer;
Catalyst oxidation gas supply means for supplying a catalyst oxidation treatment gas for oxidizing the catalyst to the catalyst layer;
Temperature measuring means for measuring the temperature of the catalyst layer;
Oxygen concentration measuring means for measuring the oxygen concentration of the catalyst oxidizing gas supplied by the catalyst oxidizing gas supply means;
When the tar decomposition system is brought down, the catalyst layer is brought into an inert gas atmosphere by the supply of the inert gas by the inert gas supply means, and the temperature measured by the temperature measurement means is set to 700 ° C. or less. Control means for controlling the supply of the catalyst oxidation gas by the catalyst oxidation gas supply means and oxidizing the catalyst, and
The control means controls the oxygen concentration of the catalyst oxidizing gas to be 1% or less during the oxidation treatment of the catalyst, and controls the temperature measured by the temperature measuring means. A tar decomposition system characterized in that the temperature is controlled so as not to exceed 800 ° C. The tar decomposition system according to claim 7, wherein the inert gas supplied to the catalyst layer of the reactor is circulated to the reactor through a cooling means for cooling the inert gas.

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