JP6970631B2 - Operation method of volatile organic compound processing equipment - Google Patents

Description

The present invention relates to an apparatus for treating a volatile organic compound from the gas before discharging the gas containing the volatile organic compound.

Exhaust gas generated from factories may contain volatile organic compounds that cause problems if they are discharged into the atmosphere as they are. In this case, the volatile organic compounds contained must be treated before the exhaust gas is discharged into the atmosphere. As a method for this, a volatile organic compound contained in the exhaust gas is adsorbed on the adsorbent by an adsorption tower having an adsorbent such as activated carbon, and the concentration in the gas is reduced and discharged to the atmosphere. After that, a suction / desorption method is generally used in which water vapor is introduced into the adsorption tower to desorb the volatile organic compound from the adsorbent so that the adsorption tower can be reused and the volatile organic compound is treated.

This utilizes the fact that the amount of adsorption of activated carbon that adsorbs volatile organic compounds basically depends on the temperature. The lower the temperature of the activated carbon, the higher the adsorption amount, and the higher the temperature, the lower the adsorption amount. Therefore, the activated carbon is adsorbed at a low temperature, and when it is desorbed, it is heated to a high temperature. To desorb activated carbon at a high temperature, the amount of heat such as high-temperature desorption steam, high-temperature gas that burns fuel, and residual gas after evaporating water with the amount of heat of the high-temperature gas to generate desorption steam is used. It is carried out to introduce the gas having (Patent Document 1).

In the operation of the volatile organic compound processing apparatus using this adsorption tower, it is desirable to improve the thermal efficiency as much as possible because the fuel for generating the desorbed steam accounts for most of the cost. It has been studied to burn desorbed volatile organic compounds and utilize the heat of combustion to assist the generation of desorbed steam to suppress fuel consumption.

On the other hand, if the amount of volatile organic compounds contained in the exhaust gas introduced into the adsorption tower is too large, the load on the device becomes too high. When a high concentration of volatile organic compounds is contained, it is desirable to reduce the amount of volatile organic compounds in advance by another method for exhaust gas before introduction, and to use an adsorption tower for the remaining volatile organic compounds. .. Patent Document 2 proposes to introduce a gas after performing temperature control in advance to cool the gas to an appropriate temperature according to the dew point temperature of the gas.

Japanese Unexamined Patent Publication No. 2014-168741 Japanese Unexamined Patent Publication No. 2014-526

It is an object of the present invention to further reduce the energy and load required for the operation of steam while maintaining the work efficiency in the operation of the volatile organic compound processing apparatus.

This invention
The concentration of the volatile organic compound in the volatile organic compound-containing gas is reduced by adsorbing the volatile organic compound to the activated carbon by using an adsorption tower having an adsorbent accommodating portion filled with the active carbon that adsorbs the volatile organic compound.
In operating a volatile organic compound processing apparatus that desorbs the volatile organic compound from the activated carbon by contacting it with a high-temperature gas after adsorption.
The adsorption tower is equipped with a thermometer capable of measuring the internal gas temperature.
Detachable steam was used as the high temperature gas, and
Measure the temperature of the volatile organic compound-containing gas to be introduced,
The lower the temperature, the more the amount of desorbed water vapor introduced was suppressed, and the above-mentioned problem was solved by the operation method.

This is based on the following new findings. In order to fully restore the adsorption performance of the activated carbon once adsorbed, sufficient desorption is required, so it was common to set the heating target temperature uniformly. However, when adsorption is performed in a low temperature environment, a sufficient amount of adsorption can be expected due to its nature, so it is not necessary to thoroughly desorb in order to restore the adsorption performance, and it was found that the required heating amount can be reduced. On that basis, it was confirmed that the amount of gas required for temperature rise is specifically different when water vapor is used than when gas such as air is used.

In the past, activated carbon was heated and desorbed to the same temperature as in summer operation regardless of the season, but in winter the temperature of the volatile organic compound-containing gas into which activated carbon is introduced becomes lower, and the amount that can be adsorbed is higher than in summer. improves. Then, if the activated carbon is sufficiently cooled by the outside air temperature without thorough desorption, the required adsorption amount can be secured.

In particular, the amount of water vapor required to secure the required desorption rate differs greatly between the case where the adsorption temperature is around 30 ° C and the case where the adsorption temperature is around 35 ° C, despite the slight temperature difference. I found it. Comparing the amount of water vapor required at around 35 ° C as a reference, it was found that the amount of water vapor required at around 30 ° C can be reduced from 2/3 or less to nearly half. In a lower temperature environment, the amount of water vapor reduction compared to the amount of temperature decrease is smaller than the decrease tendency to around 30 ° C, but it can be further reduced in addition to the rapid reduction tendency to around 30 ° C, so it is 35 ° C. The amount of reduction compared to the environment before and after is further expanded. Therefore, even in the adsorption environment not only in winter but also in the time when the temperature difference from summer is not so large, such as spring and autumn, the difference in the required amount of steam caused by the slight difference in adsorption occurs. The amount of steam can be significantly reduced by determining the temperature based on the specific difference between about 35 ° C. and about 30 ° C.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to reduce the energy required for the generation of desorption steam and the like, and to improve the energy efficiency of the entire device.

Configuration example diagram of a volatile organic compound processing apparatus for executing the operation method according to the present invention.

Hereinafter, embodiments of the present invention will be described. The present invention is an operation method of a volatile organic compound processing apparatus 10 that reduces the concentration of a volatile organic compound-containing gas so that it can be discharged into the atmosphere, and adsorbs the volatile organic compound to the adsorbent. The adsorption tower 11 that adsorbs with this processing device 10 has activated carbon as an adsorbent, and the adsorbed volatile organic compounds can be desorbed from the adsorbent by contacting with heated steam, and the adsorbent can be used repeatedly. The desorbed volatile organic compounds are recovered and used as fuel for obtaining heated steam. FIG. 1 shows an example of an overall image of the processing apparatus 10 that performs these series of cycles.

The volatile organic compound processed by the processing apparatus operated by the operation method according to the present invention is an organic compound that can become a gas by heating at normal pressure, and a compound that is liquid at room temperature is particularly easy to be 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.

Each adsorption tower 11 has a rectangular shape or a cylindrical shape, and an adsorbent accommodating portion 12 filled with an adsorbent that adsorbs volatile organic compounds and can be desorbed by heating is provided inside the apparatus. Granular activated carbon can be used as this adsorbent. In order to pass through the inside of the adsorption tower 11 in the vertical direction, it must pass through the adsorbent accommodating portion 12. Both the bottom surface and the top surface of the adsorbent accommodating portion 12 are housed in the adsorbent tower 11.

A thermometer 13 is provided in the adsorbent accommodating portion 12 for accommodating the activated carbon of the adsorption tower 11, and is connected to a control valve 24 described later.

An introduction port 17 for the volatile organic compound-containing gas A is provided on the upper end side of the adsorbent accommodating portion 12 of the adsorption tower 11, and the volatile organic compound-containing gas A is introduced by the pressure generated by the raw gas blower 14. .. On the lower end side of the adsorbent accommodating portion 12, a discharge port 18 for the treated gas B whose concentration is reduced by adsorbing the volatile organic compound to the adsorbent is provided. The discharge port 18 discharges into the atmosphere.

Further, a steam supply port 25 for the desorbed steam F is provided below the lower end of the adsorbent accommodating portion 12 of the adsorption tower 11. Further, a steam discharge port 26 for extracting the steam organic compound-accompanied gas K from which the volatile organic compound has been desorbed is provided on the upper end side of the upper end of the adsorbent accommodating portion 12. The water vapor organic compound-accompanied gas K is conveyed from the water vapor discharge port 26.

The steam organic compound-accompanied gas K is supplied to the condenser 15 and cooled by the cooling water P. By cooling, the volatile organic compound contained in the gas K accompanied by the steam organic compound is separated and recovered (recovered organic compound Q), and the remaining gas is used as exhaust R.

Valves are provided at the inlet and outlet to each suction tower 11. That is, a valve 21 is provided at the introduction port 17, a valve 22 is provided at the discharge port 18, and a valve 23 is provided at the steam discharge port 26. Further, the steam supply port 25 is provided with a control valve 24.

In the adsorption step for treating the volatile organic compound-containing gas A, the valve 21 and the valve 22 are opened, the valve 23 and the control valve 24 are closed, and the raw gas blower 14 is used to open the volatile organic compound-containing gas from the introduction port 17. A is aerated through the activated carbon 12. At this time, the temperature at the start of adsorption is measured with the thermometer 13. This temperature is basically the temperature of the activated carbon 12, and is also the temperature of the volatile organic compound-containing gas A. If the adsorption tower 11 is sufficiently cooled and the concentration of the volatile organic compound-containing gas A is about 50 to 1000 ppm, this temperature is almost the same during operation and can be regarded as the same.

The activated carbon 12 adsorbs the volatile organic compound, and the treated gas B from which the volatile organic compound has been removed is discharged from the discharge port 18. When the activated carbon 12 sufficiently adsorbs the volatile organic compound and the calculated adsorption amount exceeds the permissible value, the adsorption is stopped and the process is switched to the desorption step.

In the desorption step, the valves 21 and 22 are closed, the valves 23 and the control valve 24 are opened, and the desorption steam F is brought into contact with the activated carbon, contrary to the adsorption step. At this time, the open amount of the control valve 24, that is, the supply amount of the attached / detached steam F is adjusted according to the value of the thermometer 13 at the start of adsorption measured earlier. Specifically, the lower the value of the thermometer 13 in the adsorption step, the more the amount of desorbed water vapor F to be introduced is suppressed. The lower the temperature at the time of adsorption, the larger the amount of volatile organic compounds that can be adsorbed. Therefore, when the adsorption step is performed again after the desorption step, even if the desorption is not thoroughly performed, the potential adsorption required for the adsorption step is sufficient. This is because the amount can be secured. That is, when the temperature at the start of adsorption is low, the amount of desorption steam F can be suppressed, the consumption of fuel required to generate the desorption steam F can be suppressed, and the operational load of the device can be reduced. can.

However, this adjustment value is not determined according to a general gas adsorption isotherm, but is preferably performed after measuring the adsorption amount and the desorption amount for each temperature for each property of the adsorption tower. Desorption It has been confirmed that desorption using steam F does not follow the behavior of the adsorption isotherm in a gas that is not steam, and for proper operation, the removal rate of the gas to be treated is 80%. As mentioned above, it is desirable to supply a steam amount commensurate with the amount so as to be preferably 90%.

The amount of vapor required for desorption to achieve such a sufficient removal rate sharply decreases when the adsorption temperature is around 30 ° C., based on the case where the adsorption temperature is around 35 ° C. It is considered that there is a singular point where the required vapor amount changes specifically between around 35 ° C and around 30 ° C. Therefore, as a condition of the adsorption temperature, it is distinguished between 34 ° C. or higher and 31 ° C. or lower. The temperature of 34 ° C or higher corresponds to the above-mentioned situation of around 35 ° C, and corresponds to the operation in the summer. The adsorption temperature as a reference for this summer is preferably 34 ° C. or higher and 37 ° C. or lower.

When the adsorption temperature is 31 ° C. or less, a sufficient removal rate can be realized with a steam amount Vex of 2/3 or less with respect to the steam amount Vsummer supplied to realize a sufficient removal rate at the time of the summer standard. .. At the adsorption temperature of 15 ° C. or higher and 31 ° C. or lower, it is desirable to operate with a steam amount of 1/3 or more and 2/3 or less of Vsummer. At the adsorption temperature of 0 ° C. or higher and 15 ° C. or lower, it is desirable to operate with a steam amount of 1/4 or more and 1/2 or less of Vsummer.

The desorbed volatile organic compound becomes a water vapor organic compound-accompanied gas K together with the desorbed water vapor whose temperature has dropped, and is discharged from the water vapor discharge port 26. This steam organic compound-accompanied gas K is introduced into the condenser 15, cooled with cooling water P to recover the contained volatile organic compound (recovered organic compound Q), and the remaining gas is exhausted (R) for treatment.

Hereinafter, examples of the present invention will be shown. Volatile organic compounds with a toluene concentration of 300 ppm so that the passing air velocity is 0.5 m / s in the adsorption tower (activated carbon layer area: 1.0 m ^{2, activated carbon layer thickness: 0.3 m) manufactured by Kurimoto, Ltd.} The compound-containing gas A was introduced and adsorbed so that the adsorption time was 80 minutes. The desorption time was 40 minutes, and the removal rate required to be considered as complete desorption in operation was set to 90%.

When operated at an adsorption temperature of 35 ° C., the amount of steam required for a removal rate of 90%, Vsummer, was 27 kg. This Vsummer is used as a reference.

When operated at an adsorption temperature of 30 ° C., the amount of steam required for a removal rate of 90%, Vex30, was 14 kg, which could be reduced to 52% with respect to Vsummer.

When operated at an adsorption temperature of 10 ° C., the amount of steam required for a removal rate of 90%, Vex10, was 10 kg, which could be reduced to 37% with respect to Vsummer.

10 Processing device 11 Adsorption tower 12 Activated carbon (adsorbent accommodating part)
13 Thermometer 14 Raw gas blower 15 Condenser 17 Inlet 18 Discharge port 21, 22, 23 Valve 24 Control valve 25 Steam supply port 26 Steam discharge port A Volatile organic compound-containing gas B After treatment Gas F Detachable water vapor K Steam organic compound Accompanying gas P Cooling water Q Recovered organic compound R Exhaust

Claims (2)

The concentration of the volatile organic compound in the volatile organic compound-containing gas is reduced by adsorbing the volatile organic compound to the activated carbon by using an adsorption tower having an adsorbent accommodating portion filled with the active carbon that adsorbs the volatile organic compound.
In operating a volatile organic compound processing apparatus that desorbs the volatile organic compound from the activated carbon by contacting it with a high-temperature gas after adsorption.
The adsorption tower is equipped with a thermometer capable of measuring the internal gas temperature.
Detachable steam was used as the high temperature gas, and
Measure the temperature of the volatile organic compound-containing gas to be introduced,
An operation method of a volatile organic compound processing apparatus that suppresses the amount of desorbed water vapor to be introduced as the temperature is lower. The range of suppression of the amount of desorbed water vapor is
The amount of the desorbed water vapor to be introduced when the temperature is 34 ° C. or higher is used as a reference value.
The method for operating a volatile organic compound processing apparatus according to claim 1, wherein the amount of the desorbed water vapor introduced when the temperature is 31 ° C. or lower is suppressed to 2/3 or less of the reference value.

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