KR200259453Y1 - Circulation & Flow Control Type Catalyst Oxidation Desorber - Google Patents

Abstract

The present invention has been recently developed and used as a facility for desorbing and regenerating activated carbon in a facility equipped with an activated carbon adsorption tower, which is one of VOC removal facilities, in a facility for discharging high molecular organic compound vapor (VOC) such as a coating facility, a printing facility, and a cleaning facility. The device is an improved desorption facility.

However, since the simple activated carbon adsorption tower (the first method) is simple in structure and low in equipment cost, it is widely used as a VOC removal facility. However, activated carbon can be adsorbed any longer due to the adsorption of a certain amount of VOC. Due to the lack of characteristics, it has to be replaced every certain period, which causes a problem of excessive activated carbon replacement cost.

Therefore, the above problem has been solved by installing an activated carbon regeneration device, and has been using a method of desorption and condensation treatment by applying steam heat to the activated carbon desorption method which has been generally used.

However, this method has a problem in that the desorption apparatus itself is expensive and the equipment cost is high due to the use of corrosion resistant materials using steam, and additional utilities such as steam or cooling water are required.

In order to solve the above problems, recently, a desorption hot fan, a catalytic combustion device, and a heat exchanger are installed to heat and heat the air heated by a heater mounted on the catalytic combustion device to generate and remove hot air, and the VOC generated during desorption is again catalytically burned. It is being developed and used to inject it into the device and discharge it into the atmosphere after catalytic combustion decomposition (figure 3).

The present invention (figure 4) is a further development of the recently developed method (figure 3), which is not the method of heat exchanger with heat recovery efficiency less than 50%. By reducing the heat recovery efficiency to near 100%, the cost of operation is reduced and the heat exchanger is not needed. Secondly, the cost of the catalyst bed inlet temperature is controlled by the degassing hot wind flow rate rather than the heat of the heater. Therefore, the facility cost and operation cost were reduced. Third, in relation to the VOC removal performance, it was operated in a full circulation method for a certain period of time after the operation.Therefore, there is no discharge to the atmosphere, and even if the outside air is introduced and exhausted for oxygen supply after a certain time, the exhaust flow rate itself. Less than 99% catalytic cracking in the second stage catalyst bed It has been improved so that the VOC in the air has little emissions.

As a result, when the present method is applied, the installation cost is 30% lower than the recent use method, and the annual operation cost is much less than 1/5, and the VOC emission is much less than 1/5 to 1/10. Has an effect.

Description

Circulation & Flow Control Type Catalyst Oxidation Desorber

Many facilities, such as painting, printing, and washing facilities, use high molecular organic compounds. In this process, a large amount of high molecular volatile organic compound gas (VOC) is called vapor, which is emitted into the atmosphere. It is causing pollution.

In order to prevent air pollution due to such VOCs, various types of purification facilities are used, but most of them use a simple and inexpensive first carbon activated carbon adsorption method.

However, activated carbon has to be replaced every certain period of time because the adsorption of a certain amount of VOC is saturated and can not be adsorbed anymore, which results in excessive activated carbon replacement costs.

Therefore, the above problem has been solved by installing an activated carbon regeneration device, and has been using a method of desorption and condensation by applying steam heat shown in FIG.

However, this method has a problem in that the desorption device itself is expensive and the equipment cost is high due to the use of corrosion resistant materials using steam, and additional utilities such as steam or cooling water are required.

Recently, a method of catalytic combustion treatment after desorption by hot air shown in FIG. 3 has been developed and used.

The present invention is a step further than the third method, and devised several breakthrough improvement methods to minimize air emissions during desorption, thereby improving the prevention of air pollution, and dramatically reducing the desorption equipment installation cost and operation cost to provide an economical device. Koss devised.

In order to explain the system of the present invention, the activated carbon adsorption method and the catalytic combustion method are explained as follows.

(1) Activated carbon adsorption method

Activated carbon has a lot of micropores and a large surface area. When VOCs with high molecular weight, such as benzene, toluene, and xylene gas, pass through the activated carbon layer, organic gas molecules are introduced into the micropores by force to van der Waals force, and saturated at this site. Adsorbed in a condensed state by maintaining a high concentration above the vapor pressure. This adsorption characteristic means that the VOC is continuously adsorbed and has a limited characteristic that can not be adsorbed anymore. This means that the activated carbon introduced into the adsorption column is no longer able to remove the VOC when the activated carbon is saturated. It must be replaced or removed and reused.

The desorption process for desorption and reuse of activated carbon is performed by applying hot air or steam of 100 ° C. or higher because the activated carbon micropores are restored to their original state by the evaporation and desorption of VOC adsorbed on the surface of the activated carbon in the liquid phase.

(2) catalytic combustion method

The catalyst is made of platinum, palladium, etc. It does not participate directly in the reaction itself, but lowers the activation energy of the reactants to promote the reaction, so it burns at 150 ~ 350 ℃, much lower than the combustion oxidation temperature of VOC 600 ~ 800 ℃ It is a substance that enables oxidation and saves energy. The catalytic combustion method is a method of using such a catalyst to raise the temperature to 150 ~ 350 ℃ capable of combustion cracking through the catalyst bed to remove the combustion cracking reaction scheme is as follows.

As shown in the above reaction, when decomposing VOC in the catalyst layer, the gas temperature is increased by the heat of oxidization, and the degree of rise is proportional to the VOC concentration. Higher efficiency enables more than 95% high efficiency processing.

Then describe what has been used so far for the activated carbon adsorption method is as follows.

(1) Non-removable adsorption tower (FIG. 1 method)

As shown in FIG. 1, the activated carbon 101 is filled in a simple container in the simplest manner, and then VOCs are adsorbed and removed therein, and thus the structure is simple and the equipment cost is low.

However, this method has the following big problem

Since it is a simple device without a desorption and regeneration device, activated carbon must be replaced when saturated by continuous adsorption of VOC, so there is an excessive problem of replacing activated carbon.

For example, in a facility where about 3000kg of organic solvent is used and evaporates a year, the amount of activated carbon is 8500-10000kg and the replacement cost is 8,500,000-10,000,000 won.

(2) Steam and cooling condensation desorption system (figure 2)

This method improves the problems of the first method, and installs a desorption device to regenerate activated carbon. Operation of the desorption device is performed during a period of non-operation. The desorption and regeneration of the activated carbon 101 using steam heat is performed after desorption. After condensing the discharged VOC and steam in the condenser (4) is separated and treated with the solvent and water condensed in the oil and water separation tank (5).

This will be described in detail as follows.

As shown in FIG. 2, the system is configured to close the adsorption tower inlet damper 102 and the outlet damper 103 and open the steam inlet valve 104 and the outlet valve 105 while the exhaust fan 2 is stopped. When steam of ℃ is heated, it heats VOC adsorbed on activated carbon. As a result, the adsorbed VOC is evaporated and desorbed, and together with steam enters the cooling water condenser (4), condensing and cooling, steam is water and VOC is organic compound liquid (mainly organic solvent). ) And the condensed liquid is separated into the oil-water separation tank (5) at the bottom, and the wastewater is treated with wastewater and the organic solvent is treated separately.

In this method, since the system is rather complicated and uses steam, the production cost of the desorption device such as the condenser (4) is not only expensive, but the system itself is the use of steam and water. There is a disadvantage of using expensive equipment.

(3) Hot air and temperature controlled catalytic combustion desorption apparatus (FIG. 3 method)

This method is recently used to improve the equipment cost and utility problems of FIG. 2, and as in FIG. (Figure 3 is the state that the inventor of the present invention acquired the utility model as the '1 tower type adsorption / desorption type adsorption tower', which is a VOC removal facility for automobile paint booth)

In the desorption method, activated carbon is desorbed by hot air heat-exchanged in the heat exchanger (8) by air heated by the heater (701), and the VOC generated during desorption is discharged to the atmosphere after catalytic combustion decomposition in the catalytic combustion device (7). That's the way. At this time, the capacity of the desorption apparatus, which is the amount of desorption hot air fan, is generally used by selecting about 5 to 10% of the air volume of the exhaust fan 2 in consideration of the equipment cost, operation cost, desorption effect, desorption time, and explosion prevention of the desorption apparatus.

For example, if the adsorption tower treatment capacity is 300m 3, the desorption device capacity is about 15-30m 3 / min.

The reason for selecting and using 5 ~ 10% of the exhaust fan air flow rate is that if the capacity of the desorption device is excessively large, the desorption equipment cost and operation cost are expensive, and if it is too small, the desorption time is long and the desorption time is severe. In addition, the amount of heat supplied is so small that it is almost completely desorbed due to the loss of heat. In addition, if the amount of VOC desorption is large, the desorption capacity may be relatively high.

This method is described in detail as follows.

Adsorption tower mouth. When the outlet dampers 102 and 103 are closed and the desorption apparatus is operated while the exhaust fan 2 is stopped, the desorption hot air fan 6 and the heater 701 of the catalytic combustion apparatus are first operated.

At the initial stage of operation, outside air flows into the adsorption tower 1 as it is through the heat exchanger 8, passes through the activated carbon bed, and then exits and is heated to a predetermined temperature (usually 250 ° C.) by the heater 701 of the catalytic combustion device, followed by a catalyst bed ( 703 and the heat exchanger is exhausted to the stack (3).

Of course, at this time, the activated carbon bed inlet temperature is low, so that desorption is not performed at all. Therefore, since there is no VOC combustion decomposition in the catalyst bed, it enters the heat exchanger 8 as it is at 250 ° C.

Next, since the heated air of 250 ° C. has already passed through the heat exchanger 8, the outside air entering the heat exchanger 8 is increased to 70 to 80 ° C. and enters the adsorption tower 1. At this time, since the inlet temperature of the activated carbon layer is increased to 70-80 ° C., VOC desorption starts to occur at a small amount, and the air containing a small amount of VOC is heated again to 250 ° C. in the heater 701 to enter the catalyst 703 layer. Here, a small amount of VOC is decomposed to generate heat of decomposition, and the air passing through the catalyst layer 703 is discharged through the smoke exchanger 8 while the temperature is slightly increased (260 to 270 ° C).

When this process is repeated, the temperature flowing into the activated carbon 101 layer gradually increases, and accordingly, the amount of VOC desorption increases, and the heat of VOC decomposition in the catalyst layer gradually increases, so that the outside air temperature passing through the catalyst layer through the heat exchanger also increases to 170 ° C. Will enter.

As a result, when a certain time has elapsed since the initial operation, it is operated in a state of equilibrium and the equilibrium temperature is operated in the state shown in FIG.

Here, the capacity of the heater 701 is required to increase the amount of desorption air from the initial temperature to the temperature (200 to 400 ° C.) required for catalytic combustion. When the temperature for catalyst combustion is 250 ° C., about 3 kw / m3 is used. A heater of about 45 kw is required, for example for a desorption unit capacity of 15 m 3 / min.

However, since the heater capacity is 45kw, the heating capacity does not continue to operate at 45kw during the desorption time, and when the temperature flowing into the heater is gradually increased, the heating calorific value is gradually reduced by the heating calorie control by the automatic temperature control 702.

That is, since the heater heating is automatically adjusted to be set at a preset catalytic combustion temperature, for example, 250 ° C. so that the temperature is automatically maintained at 250 ° C. at all times, the air introduced at room temperature operates at a maximum heat of 45 kw, but gradually. When the temperature of the desorption air rises, the heat is gradually reduced, and when the equilibrium temperature (about 150 ° C.) is reached, it is operated while heating at about 20 kW.

What should be noted here is why additional heat of 20kw is required even in equilibrium when the amount of heat generated by the decomposition of VOC in the catalyst layer is enough to be used for desorption.

This is because the air discharged to the stack after heat exchange is discharged into the atmosphere with a large amount of heat, resulting in a large amount of heat loss.

The present invention considered the following technical problem.

In the installation of the desorption system to operate the activated carbon adsorption system economically, the desorption by hot air and the catalytic combustion of the desorbed VOC are adopted.

(1) Reduction of operation cost by eliminating or minimizing the large amount of heat loss to the atmosphere in the conventional method.

(2) Significantly reduce the heater capacity used in the conventional method and reduce the equipment cost by eliminating the heat exchanger.

(3) Maximize air pollution prevention by virtually eliminating VOCs emitted to the air during desorption

1 is a non-removable adsorption tower

2 is steam and cold steel condensation desorption unit

3 is a hot air and temperature controlled catalytic combustion desorption apparatus

4 is a catalytic combustion type desorption apparatus for circulation and flow rate change

* Explanation of symbols for main parts of the drawings

1 ... Adsorption Tower 2 ... Activated Carbon

102.Adsorption tower entrance opening and closing damper 103 ... Suction tower exit opening and closing damper

2 ... supply fan 3 ... stack

4 ... condenser 5 ... oil separator

6. Desorption hot fan 7. Catalytic combustion device

701 ... heater 702 ... automatic temperature controller

703 ... 1 stage catalyst layer 704 ... 2 stage catalyst layer

705 ... temperature difference automatic temperature controller 8 ... heat exchanger

Circulating hot air piping

The present invention shown in FIG. 4 has the following three other characteristics as compared to FIG.

First, the heat recovery method is not based on the conventional heat exchanger (8), but adopts the complete circulation method in which the hot gas is directly circulated without the heat exchanger.

However, if there is a risk of catalyst damage or explosion due to lack of oxygen or excessive heat generation during catalyst desorption, a certain amount of external air is injected and exhausted.

Secondly, the catalyst bed inlet temperature control method is controlled by the desorption hot air flow rate without controlling the heater heat amount.

The third stage is catalyzed by the first stage and catalytically decomposes the VOC continuously generated from the circulating hot air, and the second stage removes the VOC discharged to the outside with high efficiency for the second time with high efficiency. .

The operation of FIG. 4 having the above three features is similar to that of FIG. 2 and FIG.

Adsorption tower mouth. When the desorption device is operated while the outlet dampers 102 and 103 are closed and the exhaust fan 2 is stopped, the initial desorption hot air fan 6 and the heater 701 are operated. At this time, the exhaust air open / close valve 903 is operated. Air inlet on and off valve 902 is briefly opened and closed to put the circulating air at this time, the removable hot air flow control valve 901 is a low temperature signal (for example, 250 ℃) set by the automatic temperature controller located at the rear end of the heater And the air volume is controlled to keep only a part (about 1/5) of the desorption hot air fan's maximum amount of air flow through the heater 701. The heated air after the heating to the first stage catalyst layer 703 is operated in a circulating state to enter the adsorption tower (1) after the combustion and decomposition.

If it continues to operate in such a circulation state, the circulating hot air temperature gradually increases, and the amount of VOC desorbed from the activated carbon 101 layer gradually begins to increase.

Increasing the amount of desorbed VOC inevitably increases the temperature of the circulating air passing through the catalyst layer by the heat of decomposition while passing through the first stage catalyst layer 703, which desorbs more VOC amount to raise the temperature and raise the heater to a high temperature. The air introduced into the 701 is higher than the temperature set in the automatic temperature controller 702 to open the removable hot air flow control valve 901 to gradually increase the amount of circulating air.

Increasing the amount of circulating air, together with the increase in temperature, results in an increase in the heat of desorption, thereby accelerating desorption, thereby gradually increasing the desorption efficiency.

However, because the device is fully circulating, the catalytic combustion cracking gradually consumes oxygen in the circulating air, and at some point, the catalytic cracking may be hampered by the lack of oxygen.

To prevent this, by installing an oxygen concentration measuring instrument to be below a certain concentration or by installing a timer to reach the set time, the air inlet opening / closing damper 903 is opened and a certain amount of air is introduced and exhausted to the stack as much as the inflow amount. Configure it to continue to cycle.

Time setting of the timer predicts the VOC concentration to some extent and calculates the possible time without supplying oxygen to the amount of oxygen in the air staying in the adsorption tower 1 to set the time in the timer.

External air inflow is supplied more than three times in consideration of theoretical oxygen supply consumed for the combustion decomposition of VOC. Considering that desorption VOC concentration is high at thousands ppm, it is about 3㎥ / min when the circulation air volume is 15㎥ / min. Supply it.

In addition to the above description, one more device is provided, which is an automatic controller 705 caused by a temperature difference before and after the first stage catalyst layer 703.

The role of the automatic controller 705 is that when the temperature difference before and after the first stage catalyst layer is detected by a predetermined temperature difference or more, the outside air open / close valve 902 and the exhaust air open / close valve 903 are opened to introduce the outside air, thereby deteriorating the catalyst due to excessive temperature rise. It also prevents explosion by detecting high concentration of VOC. In general, when the catalyst inlet temperature is set at 250 ℃, the temperature difference control is 250 ℃ or less and the temperature after passing through the catalyst bed is below 500 ℃. In addition, since the VOC concentration per 100 ° C of temperature difference is about 1000ppm, the temperature difference control 250 ° C means operating below 2500ppm, and considering the lower limit of most VOC concentrations above 10000ppm, the possibility of explosion is blocked. It also plays a role.

The present invention has been improved as follows compared to the previous method.

In the case of the simple adsorption tower shown in FIG. 1, a desorption device has been installed as in FIG. 2 in order to reduce the excessive operating cost due to the replacement of activated carbon. However, the installation cost is expensive and a separate utility such as cooling water and steam has been required.

So, we have reached the stage of using the method shown in FIG.

The present invention improves the third degree method by introducing several characteristics including the complete circulation method, and its effects can be summarized into the following two.

First, it maximizes heat recovery by adopting the complete circulation method, and the catalyst bed inlet temperature control method is controlled by the desorption hot air flow rate to increase the desorption efficiency and the heater capacity is about 1/10 of the third degree method. Saved.

Second, in relation to the VOC removal performance, it is operated in a complete circulation method for a certain time after operation, so there is no VOC emission to the atmosphere, and even if some exhaust gas is exhausted after a certain time, the flow rate itself is low, and in the first stage catalyst bed Since catalytic decomposition flows into the second stage catalyst bed at a high temperature of 400 ℃ or higher, and the secondary removal is performed more than 99%, VOC removal performance is discharged to 1/5 ~ 1/10 that is insignificant compared to VOC emission of the third method. Improved dramatically.

Although the effect of the above design is described, it is presented as an example because it is rather abstract.

[Design Criteria]

Adsorption tower capacity: 100N㎥ / min

Activated carbon quantity: 200Kg

Desorption device capacity: 5N㎥ / min

VOC Type: Toluene

VOC Emission (Adsorption): 3Kg

Toluene average concentration when desorbed: about 3300 mg / N㎥ = 800ml / N㎥ (ppm)

Catalytic cracking efficiency

* Space velocity = amount of processing gas (N㎥ / h) ÷ amount of catalyst (㎥)

Required performance: 90% or more

Desorption time: 3 hours

Desorption cycle: 1 day

(1) third way

※ Heater capacity: 20kw (20N of 5N㎥ / min air is increased by 250 ℃)

※ Desorption Hot Air Fan: 8㎥ / min @ 150 ℃ × 100mmAq × 0.8kw

※ Catalyst amount: 7.5L (Based on 40000 / h space velocity)

※ Estimated time of desorption: about 3 hours

※ Catalyst inlet temperature: 250 ℃

※ VOC removal efficiency when desorption: 95%

※ VOC outlet discharge: 3kg × (1-0.95) = 0.15kg

<Approximate facilities cost>

Catalytic combustion unit: 3,000,000

Heater: 1,500,000

Catalyst: 2,000,000

Heat exchanger: 3,000,000

Removable Hot Air Fan: 300,000

Pipeline: 2,000,000

Electric facility: 3,000,000 (including control device)

Others: 500,000

--------------------------------------

Total KRW 18,000,000

〈Annual Power Costs〉

Heater: Average power 14kw

Hot air fan: about 1 kw

--------------------------------------

15kw total

15 kw × 3 / h × 330 days / year × 100 yuan / kwh

= 1,500,000 won

(2) fourth way

※ Heater capacity: 2kw (Increase air 20 ℃ to 250 ℃ of initial 0.5N㎥ / min)

※ Desorption hot air fan: 8㎥/min@150℃×100mmAg×0.8kw

※ Catalyst amount: 3.75L of 1st stage (based on space speed 80000 / h)

2nd stage 1.5L (Based on 20000 / h space velocity)

※ Catalyst inlet temperature: 1st stage 250 ℃

2nd stage 400 ℃

※ Theoretical air volume required to disassemble VOC 3kg: 30 N㎥

A ₀ = (1 / 0.21) (9 × 22.4 / 92) = 10Nm3 / kg

10 Nm3 / kg × 3kg-VOC = 30 Nm3

※ Size of adsorption tower: 2.2mW × 3mL × 3mH

※ Volume inside adsorption tower: 20㎥ (actually available combustion air)

※ Complete circulation time: about 1 hour (theoretical combustion air is about 10 N㎥)

※ Oxygen (outside air) supply time after complete circulation: about 2 hours

Ambient air supply = 0.5 N㎥ / min × 120 minutes

= 60 Nm3 (actually supplied combustion air)

※ VOC outlet discharge amount: 0.02㎏

3 kg × (1-0.99) × 2 hours (external discharge time) / 3 hours (desorption time)

= 0.02 kg

<Approximate facilities cost>

Catalytic combustion unit: 3,000,000

Heater: 200,000

Catalyst: 1,500,000

Removable Hot Air Fan: 300,000

Pipeline: 2,500,000

Electric facilities: 2,000,000 (including control device)

Others: 500,000

--------------------------------------

Total 10,000,000 KRW

〈Annual Power Costs〉

Heater: 2kw average power

Hot air fan: about 1kw

--------------------------------------

15kw total

3kw × 3 / h × 330 days / year × 100 round / kwh

= 300,000 won

The above review is described with an example to present the effect of the design in more detail, but the improvement effect will be different because the design criteria change for each VOC emission facility.

However, there are some differences, but in terms of economy, the installation cost is at least 30% lower than the third degree method, and the annual maintenance cost is much less than one fifth, and the VOC emission at the second outlet is less than that of the third degree method. / 5 to 1/10 is less emitted, so there is almost no air pollution.

Claims (1)

Figure 4 shows the construction of a system that is applied to an apparatus for desorption and regeneration of activated carbon in activated carbon adsorption tower. Desorption hot air fan (6) and desorption hot air fan (6) for desorption hot air supply and an air heating heater (701) provided with desorption tower damper (102) and outlet desorption damper (103) for adsorption tower inlet and outlet air blocking when desorption to activated carbon adsorption tower (1). A catalytic combustion device 7 composed of a first stage catalyst layer 703 and a second stage catalyst layer 704 for catalytic decomposition of desorbed volatile organic vapors, Inlet connection pipe with hot air flow rate control valve 901 that gradually increases and adjusts the initial flow of hot air in the catalytic combustion device inlet to the catalytic combustion device inlet and the catalyst combustion device first stage catalyst layer for circulation supply of hot air. Hot air circulation pipe (9) connected from the outlet between the second stage catalyst bed and the adsorption tower desorption hot air inlet, and the outside air inlet pipe and exhaust air connected to the front end of the hot air flow control valve and interlocked with a timer and having an air inlet on / off valve (902). Consisting of exhaust air piping located at the exit of the catalytic combustion device with an on / off valve 903, The automatic temperature controller 702 located in front of the first stage catalyst bed interlocked with the flow rate control valve 901 and the automatic temperature controller by the temperature difference before and after the first stage catalyst bed interlocked with the external air inlet on / off valve and the exhaust air on / off valve. A catalytic combustion desorption unit for circulation and flow rate changes, characterized in that it comprises a device with a series of systems in which 705 is installed.