JP5113207B2 - Operation method of volatile organic compound processing equipment - Google Patents

Description

  The present invention relates to an operation method for improving the efficiency of processing work in processing a volatile organic compound from a gas before discharging the gas containing the volatile organic compound.

  Exhaust gas generated from factories may contain volatile organic compounds that cause problems if discharged into the atmosphere as they are. In this case, before exhaust gas is discharged into the atmosphere, the contained volatile organic compounds must be treated. As a method for this, an adsorption tower containing activated carbon or other adsorbent is used to adsorb volatile organic compounds contained in exhaust gas to the adsorbent, reduce the concentration in the gas and discharge it to the atmosphere. An adsorption / desorption system is generally used in which a volatile organic compound is desorbed to make the adsorption tower reusable and the volatile organic compound is treated.

  For the above desorption, it is necessary to bring a gas not containing a volatile organic compound into contact with the adsorbent. Since adsorption cannot be performed simultaneously with desorption by a single adsorption tower, desorption is preferably carried out promptly. As a method of speeding up desorption, a method of introducing a large amount of desorption gas, a method of reducing pressure by sucking with a vacuum pump, a method of introducing high-temperature desorption water vapor to promote desorption which is an endothermic reaction, etc. There is.

  In order to introduce high-temperature desorption water vapor, a large amount of fuel is consumed for its heating, so a method for saving fuel has been studied. In Patent Document 1, desorbed water vapor containing the recovered volatile organic compound is guided to a combustion furnace, and the volatile organic compound is burned as a fuel (Claim 1). It is described that the steam is heated (Claim 2).

  On the other hand, in Patent Document 2, an adsorption tower that sucks with a vacuum pump is provided with a plurality of adsorbent layers provided with an adsorbent, thereby increasing the desorption speed without using a high-performance vacuum pump. A method has been proposed. The adsorption tower described in this document introduces a gas containing alcohols, which are volatile organic compounds, from below, and extracts exhaust gas from which alcohols have been reduced from above (Patent Document 2 FIG. 1). Desorption gas introduction holes (purge air introduction pipes) are provided between the uppermost adsorbent layer and each adsorbent layer, and desorbed gas exhaust holes (exhaust conduits) are adsorbed between each adsorbent layer and the lowermost layer. It is provided at a location below the agent layer (Patent Document 2 [0039]). Then, an automatic valve of a desorption gas introduction hole and an exhaust conduit underneath with one adsorbent layer is opened sequentially from the top as a set and closed as soon as desorption is completed (Patent Document 2 [0042] ] To [0045]).

  However, this method is a method in which each layer is desorbed stepwise by suction, and in the method using heated desorption water vapor, even if the method of Patent Document 2 in which gas is sucked from each layer is adopted, such an effect is not obtained. Absent.

JP 2007-2222736 A JP 2002-293754 A

  However, as described in Patent Document 1 (FIG. 1), exhaust gas containing a volatile organic compound is introduced from the lower side of the adsorption tower, and the treated gas is discharged from the upper side. Is introduced from the upper part of the adsorbent layer, desorbed from all parts of the adsorbent layer, and extracted from the lower side of the adsorbent layer, it takes too much time for the desorption water vapor to pass through the adsorbent layer. End up. That is, it takes too much time from the start of heating to generate desorption steam in the combustion furnace until the organic compound is extracted along with the steam and reaches the combustion furnace (steam generator). Until then, the recovered volatile organic compound could not be used as fuel, and another fuel such as LNG gas had to be used, resulting in waste.

  Accordingly, the present invention reduces the time lag from the start of desorption until it can be used as fuel when desorbing a volatile organic compound from an adsorption tower using heated desorption water vapor, thereby suppressing fuel waste. With the goal.

This invention
As the supply port to the desorption water vapor adsorption tower consists of multiple stages divided in both end directions,
Among them, the supply port on the one end side of the adsorption tower is provided on the side face of the position occupied by the adsorption layer inside the adsorption tower,
Opening from the supply port located at one end of the adsorption tower, introducing desorption water vapor from the middle of the adsorption layer, and desorbing and extracting organic compound-containing water vapor containing volatile organic compounds from the one end side of the adsorption tower Thus, the above problem has been solved.

  Among the plurality of supply ports, the supply port that opens first is the one closest to the one end side, that is, the supply port side from which the organic compound-containing water vapor is extracted. For this reason, time until desorption water vapor first escapes from the adsorption layer and reaches the combustion furnace can be shortened as compared with the case where the entire area of the adsorption layer is passed as in the conventional case. Thereby, the time which should heat a combustion furnace only with fuel can be shortened.

  In addition, among all the supply ports, the one at the other end side that is to be opened last is provided at the other end side rather than the adsorption layer, so that the entire adsorption layer can be desorbed.

  Specifically, when the supply port on the one end side is provided at a position closer to the one end side than the position in the center of both ends of the adsorption layer, the time until the supplied desorption water vapor passes through the adsorption layer is reduced. It can be greatly shortened. In addition, it is preferable that the supply port on the other end side is located at the end portion on the other end side of the adsorption layer or on the other end side than that. This is because the desorption efficiency of the adsorbent at a position farthest from the supply outlet is lower than the supply port located on the most other end side.

  A temperature sensor may be provided in the combustion furnace, and a fuel control circuit may be provided to reduce the amount of fuel supplied to the combustion furnace when a temperature increase in the combustion furnace is detected. When desorbed water vapor containing volatile organic compounds reaches the combustion furnace, the amount of combustible material supplied to the combustion furnace increases and the temperature rises. Fuel can be saved by reducing the amount of fuel supplied so that the temperature is appropriate.

  After that, if the temperature sensor detects a decrease in the temperature of the combustion furnace, it means that the amount of volatile organic compound to be supplied has decreased, so the supply port on the other end side is opened and the adsorption layer is opened. It is possible to supply desorption water vapor to the portion where the volatile organic compound is not yet desorbed, increase the volatile organic compound desorbed and supplied to the combustion furnace, and stabilize combustion in the combustion furnace. Moreover, you may open each supply port in order with progress of time from what exists in the said one end side. In this case, a time for opening each supply port is set in advance. Further, each supply port may be opened over time, and only the supply port on the other end side may be opened when the temperature sensor detects a decrease in temperature.

  The adsorption layer may be composed of only one layer, or a plurality of layers may be provided for each supply port of desorption water vapor provided in a plurality of stages. When divided into a plurality of layers, the supply port located closest to the one end side is located at the position where the adsorption layer located closest to the one end side is present, or the adsorption layer and one of them is located on the other end side. Provided between the adsorption layer.

  The outlet may be provided on the one end side more than the supply port on the one end side, and may be on the side surface of the portion occupied by the adsorption layer, or on the one end side from the end of the adsorption layer.

  By implementing this invention in an adsorption tower for treating a gas containing a volatile organic compound, consumption of fuel used for removing the volatile organic compound can be suppressed and energy saving can be achieved.

Conceptual diagram of an adsorption tower and its peripheral devices for carrying out the present invention Flow chart of desorption process for carrying out this invention Flow chart of adsorption process and desorption process with two adsorption towers

  Embodiments of the present invention will be described below. The present invention relates to a volatile organic compound processing apparatus that reduces the concentration of a volatile organic compound-containing gas so that the gas can be discharged into the atmosphere, collects the volatile organic compound, and uses it as a fuel. FIG. 1 shows an example of an overall image of a volatile organic compound processing apparatus according to the present invention.

  The volatile organic compound to be treated in the present invention is an organic compound that can be converted into a gas when heated at normal pressure, and particularly, a liquid that is liquid at room temperature is easily adsorbed. Examples thereof include hydrocarbon solvents such as alcohols having about 1 to 8 carbon atoms such as methanol, ethanol and isopropyl alcohol, and aromatic organic compounds such as toluene and benzene.

  The volatile organic compound processing apparatus for carrying out the present invention includes an adsorption tower 11, a combustion furnace 13, and a heat exchanger 14.

  The adsorption tower 11 has a substantially cylindrical shape, and the inside is partitioned by a single porous plate 20 provided in the vicinity of the lower end. An adsorption layer 12 filled with an adsorbent that adsorbs volatile organic compounds and can be desorbed by heating is provided on the perforated plate. Examples of the adsorbent include activated carbon.

  An inlet 17 for the volatile organic compound-containing gas A is provided at the upper end side of the adsorption layer 11 of the adsorption tower 11, and the concentration of the volatile organic compound is adsorbed by the adsorbent at the lower end side of the adsorption layer 12. A post-treatment gas B outlet 18 is provided. The discharge port 18 discharges into the atmosphere.

  Further, the desorption water vapor F supply ports 15A to 15E having a plurality of stages (five stages in FIG. 1 in total) are provided on the side surface and the lower end of the portion of the adsorption tower 11 where the adsorption layer 12 is provided. The uppermost supply port 15A is located above the center of the adsorption layer 12 in the vertical direction and below the porous plate 20 at the upper end of the adsorption layer 12, and the lowermost supply port 15E is lower than the lower end of the adsorption layer 12. Located below. Further, the outlet 16 for extracting the organic compound-containing water vapor K from which the organic compound has been desorbed is provided on the upper end side of the upper end of the adsorption layer 12.

  The combustion furnace 13 generates heat for generating the desorption water vapor F, and the organic compound-containing water vapor sent from the fuel supply port 21 for supplying the fuel D and the outlet 16 of the adsorption tower 11. A steam supply port 22 for supplying K, a burner (not shown), a chimney (not shown), and a combustion furnace temperature sensor 24 for measuring the internal temperature are provided. The heat generated in the combustion furnace 13 is supplied to the heat exchanger 14.

  The heat exchanger 14 is provided with a water supply port 26 that supplies water E that is a source of water vapor, and supplies desorption water vapor F obtained by heating the water E to the supply ports 15 </ b> A to 15 </ b> E of the adsorption tower 11. The desorption water vapor supply path 25 and the water vapor temperature sensor 28 that measures the internal temperature of the desorption water vapor supply path 25 are provided. The water supply port 26 has a function of spraying water E into the desorption water vapor supply path 25. Moreover, the desorption water vapor supply path 25 is branched (27a, 27b) on the way, and one branch 27b is connected to the opening 29 to the atmosphere, and a circulation path is formed between the branch 27a and the heat exchanger 14. Forming.

  In the volatile organic compound processing apparatus according to the present invention, first, the volatile organic compound contained in the volatile organic compound-containing gas A introduced into the adsorption tower 11 is adsorbed by the adsorbent of the adsorption layer 12. The treated gas B that has passed through the adsorption layer 12 exits from the outlet and is released into the atmosphere. This adsorption work is performed until a certain period of time elapses or until the adsorption capacity becomes below a certain level. In order to stop the adsorption by detecting a decrease in the adsorption capacity, a volatile organic compound detection device (not shown) is provided at the discharge port 18 where the concentration of the volatile organic compound contained in the gas B after the treatment is determined. A control circuit is provided that, when measured and exceeds a predetermined value, interprets that the adsorption capacity of the adsorption layer 12 has reached its limit and issues a command to close the valve of the inlet 17.

  On the other hand, preparation for desorption is proceeded before the adsorption is completed. Since the desorption water vapor F cannot be supplied immediately, if heating is started after the completion of adsorption, a time lag occurs before the desorption begins, and the originally necessary adsorption process is stopped. In addition, when there are two or more adsorption towers 11, the adsorption process can be performed on the other side even if the adsorption process is stopped on one side, but in that case, the desorption water vapor F is always prepared.

  This desorption process will be described with reference to the flow of FIG. First, combustion of the fuel D is started in the combustion furnace 13, and the air in the circulation path of the desorption water vapor supply path 25 is circulated by a fan (not shown) provided in the path (S11). When the water control circuit 30 detects the air temperature at this time with the water vapor temperature sensor 28 and confirms that the water control circuit 30 has reached the set temperature T1 or higher at which water vapor can be generated (S12), the desorption water vapor that returns to the heat exchanger 14 from the branch 27a The valve of the water supply port 26 of the water E into the supply path 25 is opened, and the water E is sprayed to generate water vapor in the heat exchanger 14 (S13). In the heat exchanger 14, the temperature of the water vapor generated by the water vapor temperature sensor 28 is detected, and the opening 29 is maintained until the desorption water vapor F reaches a temperature T2 suitable for desorption (S14) or until the adsorption is completed. The valve is opened and released into the atmosphere (S15). This is because desorption is an endothermic reaction, and desorption does not proceed quickly unless the steam is sufficiently hot. Here, the desorption water vapor F is superheated water vapor or saturated water vapor.

  When the adsorption in the adsorption tower 11 is completed and the desorption water vapor F becomes equal to or higher than the predetermined temperature T2 (S14), the opening control circuit 31 closes the valve to the opening 19 and supplies the supply closest to the outlet 16 The valve of the desorption water vapor F to the mouth 15A is opened (S16). The desorption water vapor F supplied to the supply port 15A desorbs the volatile organic compound adsorbed on the upper layer portion of the adsorption layer 12, and becomes an organic compound-containing water vapor K, which is delivered from the outlet 16 (S17). Here, the closer the supply port 15 </ b> A is to the upper end of the adsorption layer 12, the shorter the time until the desorbed organic compound-containing water vapor K passes through the adsorption layer 12 and reaches the upper outlet 16. As a result, the time until the organic compound-containing water vapor K reaches the water vapor supply port 22 communicating from the outlet 16 to the combustion furnace 13 (S18) is also shortened.

  When the organic compound-containing water vapor K reaches the combustion furnace 13 (S18), the total amount of combustibles supplied to the combustion furnace 13 increases, so the temperature in the combustion furnace 13 rises. This temperature rise is detected by the combustion furnace temperature sensor 24. A prescribed temperature T3 that is defined as exceeding the error in temperature rise during combustion of only fuel D is prescribed in the fuel control circuit 33 in advance, and when the temperature detected by the combustion furnace temperature sensor 24 becomes T3 or more (S19). ) Assuming that the combustibles have increased due to the arrival of the organic compound-containing water vapor K, the valve of the fuel D supplied to the fuel supply port 21 is throttled to save the fuel D (S20).

  However, since the organic compound contained in the organic compound-containing water vapor K decreases as the volatile organic compound adsorbed near the supply port 15A is gradually desorbed, the supply port 15B on the side closer to the outlet 16 in turn, The valves 15C, 15D, and 15E are opened so that the amount of the volatile organic compound supplied to the combustion furnace 13 is not excessively reduced. The opening timing may be determined by the elapsed time since the supply port 15A closest to the outlet 16 is opened, or the temperature decrease defined in advance by the combustion furnace temperature sensor 24 of the combustion furnace 13 may be determined. As shown, that is, when it is detected that the amount of combustible material to be burned has decreased, it may be opened sequentially. When the temperature drop is detected, if the supply port control circuit 32 that preliminarily defines the furnace temperature T4 that should be dealt with by reducing combustibles detects the temperature drop of the combustion furnace temperature sensor 24 (S21), supply Among the unopened valves of the ports 15B to 15E, the valve closest to the outlet 16 (upper end side) is opened (S22 to S25). One valve is opened, and once the furnace temperature rises, the furnace temperature is monitored again, and when the temperature drop is detected, the next valve is opened. This is continued until all the supply ports are opened (S26). When the next valve is opened, the supply port valve that has been opened is closed.

After the supply ports 15A to 15E are opened, when a time t1 at which the desorption in the adsorption layer 12 sufficiently proceeds (S27), the valves 15A to 15E are closed to complete the desorption (S28). If there is only one adsorption tower 11, the valve of the fuel supply port 21 for supplying the fuel D is closed, and the combustion in the combustion furnace 13 is ended (S29). In addition, the valve of the outlet 16 is also closed.
Excess desorption water vapor still generated in the heat exchanger 14 is released into the atmosphere by opening the valve of the opening 29 (S30).

  Thus, the desorption of the adsorption tower 11 is completed, and the adsorption layer 12 can be again adsorbed. Therefore, the inlet 17 of the volatile organic compound-containing gas A is opened to start the adsorption, and the adsorption is performed for a certain time. After that, desorption is performed in the same procedure as described above.

  As another embodiment of the present invention, the positions of the supply ports 15A to 15E, the outlet 16, the introduction port 17, and the discharge port 18 provided in the adsorption tower 11 may be reversed in the vertical direction.

  Another embodiment includes an embodiment provided with two adsorption towers 11. In the above-described embodiment in which the adsorption tower 11 is a single unit, the treatment of the volatile organic compound-containing gas A cannot be performed during desorption. Therefore, the treatment must be temporarily stopped and stored. When two adsorption towers 11 are provided, the adsorption can be started with another unit while the adsorption is completed with one unit and the desorption is started, so that the time required for the desorption is shorter than the time that can be adsorbed. Thus, the processing of the volatile organic compound-containing gas A can be continued without stopping. In order to realize this embodiment, the control circuit is prepared so that ports for supplying and discharging to each adsorption tower 11 are provided, and individual valves can be operated independently.

  FIG. 3 shows adsorption and desorption procedures in an embodiment provided with two such adsorption towers 11. First, the adsorption in the adsorption tower β starts with the completion of the adsorption in the adsorption tower α. By the time the adsorption capacity of the adsorption tower β is lowered, desorption is started from the adsorption layer 12 of the adsorption tower α. First, the supply port 15A is opened, and when the first organic compound-containing water vapor K reaches and the temperature of the combustion furnace 13 rises, the supply amount of the fuel D is reduced (S20). Then, while detecting the temperature fall (S21) of the combustion furnace 13, the supply ports 15B to 15E are opened sequentially (S16), and the desorption of the adsorption layer 12 is advanced. When the desorption has sufficiently progressed, the introduction of the desorption water vapor into the adsorption tower α is stopped (S41). Since the organic compound-containing water vapor K does not reach the combustion furnace 13, the supply amount of the fuel D is temporarily recovered (S42) and the combustion is maintained in order to compensate for the shortage of combustion substances. During this time, the desorption water vapor F is always generated, but all the supply ports 15A to 15E are closed, so that they are circulated from the branch 27a to the heat exchanger 14 or appropriately opened from the open port 29. Then, when the adsorption in the adsorption tower β is completed, the adsorption in the adsorption tower α whose function is recovered by desorption is started, while the supply of the desorption water vapor K to the adsorption tower β is started, and the desorption is performed in the same manner. Do.

DESCRIPTION OF SYMBOLS 11 Adsorption tower 12 Adsorption layer 13 Combustion furnace 14 Heat exchanger 15A-15E Supply port 16 Outlet (organic compound containing water vapor | steam)
17 Inlet (volatile organic compound-containing gas)
18 Outlet (Gas after treatment)
21 Fuel supply port 22 Contained water vapor supply port 24 Combustion furnace temperature sensor 25 Desorption water vapor supply path 26 Water supply ports 27a and 27b Branch 28 Water vapor temperature sensor 29 Open port 30 Water control circuit 31 Open port control circuit 32 Supply port control circuit 33 Fuel control circuit A Gas containing volatile organic compound B Processed gas D Fuel E Water F Desorption steam H Discharge steam K Organic compound steam

Claims (8)

A gas containing a volatile organic compound is introduced into an adsorption tower having an adsorption layer filled with an adsorbent that adsorbs a volatile organic compound, and the content is reduced by adsorbing the volatile organic compound to the adsorbent. After exhausting the treated gas, the desorption water vapor heated in the combustion furnace is introduced to desorb the volatile organic compound from the adsorbent, and the desorbed organic compound-containing water vapor is introduced into the combustion furnace for combustion. A tower operation method,
The supply port to the adsorption tower of the desorption vapor is assumed to consist of a plurality of stages, divided across the direction of the adsorption tower, most of the supply opening one end side of which, the position occupied by the adsorption layer on the inside of the adsorption tower provided on the side surface, providing a test outlet for extracting an organic compound containing water vapor after desorbing the volatile organic compound in the by one end remote the one end side of the suction layer,
Desorption water vapor is introduced from the supply port located on the most end side,
Operation method of volatile organic compound adsorption tower.   The operation method according to claim 1, wherein a temperature sensor is provided in the combustion furnace, and the amount of fuel supplied to the combustion furnace is reduced when a temperature increase exceeding a predetermined value is detected after the start of combustion. A temperature sensor provided in the combustion furnace, the supply port of the most other-end side is opened when the temperature sensor is below a temperature limit value defined in advance, an operation method according to claim 1 or 2.   The said adsorption tower shall consist of two or more groups, and after performing adsorption | suction after finishing adsorption | suction in one adsorption tower, by performing adsorption | suction in the other adsorption tower, the process of the said gas is performed continuously. 4. The operation method according to any one of items 1 to 3. For an adsorption tower having an adsorption layer filled with an adsorbent for adsorbing an organic compound, a heat exchanger for heating desorption water vapor for desorbing the volatile organic compound from the adsorbent, and a heat exchanger A volatile organic compound processing apparatus for reducing the content of a gas containing a volatile organic compound, comprising a combustion furnace that burns fuel and desorbed organic compound-containing water vapor.
The supply port to the adsorption tower of the desorption water vapor is composed of a plurality of stages in both end directions, and the supply ports have a supply port control circuit that opens from the one at the most end side,
The volatile organic compound processing apparatus, wherein the outlet for extracting the organic compound-containing water vapor after desorbing the volatile organic compound is provided on the one end side more than the supply port on the one end side.   The combustion furnace has a temperature sensor, and has a fuel control circuit that reduces the amount of fuel supplied to the combustion furnace when the temperature in the furnace becomes equal to or higher than T3 by comparing a predetermined temperature T3 with the temperature in the furnace. The volatile organic compound processing apparatus according to claim 5. The combustion furnace has a temperature sensor;
The supply port control circuit, after the furnace temperature is compared with the temperature T4 previously defined and furnace temperature becomes T4 hereinafter to claim 5 or 6 opens the supply port in most other-end side The volatile organic compound processing apparatus as described.   Supply to each adsorption tower so that the desorption can be executed by supplying desorption water vapor to the other adsorption tower while one adsorption tower is performing adsorption. The volatile organic compound processing apparatus according to claim 5, wherein a plurality of ports are provided in both end directions.

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