JPS587330B2 - Exhaust gas deodorization method and deodorization device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for deodorizing foul odors and exhaust gas generated from a heating drying oven for paints, printing inks, adhesives, etc., and a deodorizing device used in this deodorizing method.

Formaldehyde is a substance that actually has a strong odor as a malodorous component of the exhaust gas from a hot air drying oven, and if formaldehyde is removed, most of the deodorizing work can be said to be completed.

In other words, the types and amounts of malodorous components in the exhaust gas from a hot air softening furnace vary depending on the type of furnace and the type of material to be dried. The results are shown in the table below.

In addition to the substances listed in the table above, the exhaust gas contains:
Resin components and solvent components in paints are decomposed by low-temperature heating, or by reductive decomposition due to formaldehyde present in the atmosphere of a furnace. do.

In this way, the exhaust gas components and their amounts differ depending on the type of furnace, but in the above-mentioned LP gas direct-fired hot air complete circulation furnace, the amount of formaldehyde is the largest among the components, and the solvent component is incinerated with a gas burner during the circulation process. Because of this, the amount of solvent components is small.

On the other hand, in the case of heavy oil heat exchange hot blast furnaces, LP gas direct-fired semi-circulation furnaces, and kerosene direct-fired hot blast furnaces, the solvent components are not incinerated and are emitted in large quantities in the form of purple smoke, and tar-like substances are also emitted. Among the hot air furnaces of the above types, the LP gas direct-fired hot air complete circulation furnace is used, and the hot air generating device is capable of continuing neutral combustion, and the hot air circulation form of the furnace, etc. If sufficient consideration is given, the amount can be kept to an extremely small amount.

However, formaldehyde is recognized as an exhaust gas component of all the above-mentioned types of furnaces, and is characterized by its large amount.

Conventionally, the following methods have been adopted to treat foul-smelling exhaust gases from drying ovens for paints, printing inks, adhesives, and the like.

That is, (1) direct heating method, (2) catalyst method, (3) activated carbon adsorption method, (4) water shower cleaning method, etc.

Among these, (1) the direct heating method introduces the furnace exhaust gas into a gas-fired high-temperature furnace made of refractory bricks, heats it to a high temperature of 650℃ to 700℃, and holds it for 0.3 seconds or more to eliminate the odor components of the exhaust gas. It should be incinerated.

According to this direct heating method, all of the malodorous exhaust gas components are organic, so by incinerating them at high temperatures, the organic materials are combusted into carbon dioxide gas and water vapor, and this method is beginning to be adopted as the most reliable method.

However, the incineration method has disadvantages in that the fuel cost is enormous and the running cost of the drying furnace is extremely high.

For example, if we simply calculate the amount of heat generated by incineration for a displacement of 50 m3/min, it will be: 50 m3/min x 60 min x 1.2 x (750℃-
120℃)×0.24=544.320kcal/hr
It becomes.

Furthermore, this value does not take into account heat loss of the furnace body, and is simply the amount of heat required for heating.

Next, (2) the catalytic method heats the exhaust gas to about 300°C and causes an oxidation reaction with a platinum catalyst to oxidize and decompose the malodorous components, deodorizing it. There are drawbacks.

That is, since the catalyst is platinum, it is expensive, and the effectiveness of the catalyst decreases, so it needs to be replaced every 1 to 2 years.
Furthermore, since it is necessary to heat the exhaust gas to the reaction temperature of 300° C. or higher, equipment and fuel costs are required for this purpose.

Furthermore, a serious drawback is that the tar-like substances in the exhaust gas components adhere to the catalyst and reduce the effectiveness of the catalyst, so operations such as water cooling and water washing are necessary before introducing the catalyst into the catalyst chamber.

Next, (3) the activated carbon adsorption method removes malodorous components in exhaust gas by adsorbing them to activated carbon, but since the temperature of the exhaust gas in the furnace is 100°C to 170°C, it is not possible to adsorb the malodorous components in the activated carbon as is. is not possible, and water-cooling operation is absolutely necessary for effective adsorption.

(4) In the water shower cleaning method, the exhaust gas is introduced into an adsorption tower with one water shower and passed through the water shower, but formaldehyde in the exhaust gas is water-soluble, so it will temporarily dissolve in the water. However, it has the disadvantage that it evaporates again and formaldehyde is released, and that components other than water-soluble formaldehyde cannot be removed.

The purpose of the exhaust gas deodorizing method of the present invention is to eliminate the various drawbacks of the prior art described above, and to remove the organic solvent components contained in the exhaust gas from the foul-smelling exhaust gas generated by heating drying ovens for paints, printing inks, adhesives, etc. Another object of the present invention is to provide a method for removing foul odors from exhaust gas by reliably removing tar-like substances and formaldehyde through reaction.

Another object of the present invention is to provide a method for deodorizing exhaust gas that can reliably remove malodorous components in a short time.

Still another object of the present invention is to provide a deodorizing apparatus comprising a first and a second absorption tower for carrying out the method of deodorizing exhaust gas of the present invention.

Still another object of the present invention is to provide an absorption tower with extremely small static pressure loss.

Still another object of the present invention is to provide an absorption tower that is small, lightweight, and simple in structure.

Still another object of the present invention is to provide an absorption tower that is easy to clean and maintain.

Still another object of the present invention is that the amount of circulating drug solution is extremely small;
The object of the present invention is to provide an absorption tower in which the pump can be made smaller and have a lower water head, and the chemical tank formed at the bottom of the absorption tower can also be made smaller.

The basic composition of the specific invention of the present invention is a paint, a printing ink,
A chemical reaction occurs between the foul-smelling exhaust gas containing formaldehyde generated by heating drying ovens for adhesives, etc., and a chemical solution whose main component is a mixture of an oxidizing agent and a surfactant, which flows down in a ring-shaped film over multiple stages. and a step of reacting and removing organic solvent components and tar-like substances contained in the exhaust gas, and a chemical solution containing urea flowing down the exhaust gas that has passed through the step in the form of a ring-shaped film over multiple stages. This is a method for deodorizing exhaust gas, which includes a step of causing a chemical reaction to mainly remove formaldehyde contained in the exhaust gas that has passed through the above steps.

The basic structure of the related invention of the present invention is to have a chemical tank at the lower end, an inlet for the gas to be treated above the chemical tank, and an inlet for the gas to be treated at the top. A vertical cylindrical body formed with an exhaust port, and a cylindrical body disposed in multiple stages inside the vertical cylindrical body between the inlet port and the exhaust port, and each having an overflow end portion for the chemical liquid. A receiving plate and one end of the upper and lower overflow of the receiving plate are connected to each other, and the chemical solution is guided to the lower receiving plate to flow down in the form of an annular film, and the chemical solution and the treated object are an annular air-permeable guide member provided in multiple stages for contact with gas; a pump means for supplying a chemical solution from the chemical solution tank onto a receiving plate located at the top of the receiver; This is an absorption tower comprising a gas flow generating means for causing the gas to be processed to flow from the port to the exhaust port.

Embodiments of the present invention will be described below based on the drawings.

The method of the present invention comprises a first absorption tower 1 which reacts an organic solvent component contained in an exhaust gas containing formaldehyde with a tar-like substance, and a second absorption tower 2 which mainly reacts and removes formaldehyde from the exhaust gas. This is realized by

The first and second absorption towers 1 and 2 have substantially the same structure, and have chemical liquid tanks 1a and 2a at the lower ends, and air inlets 1b and 2a above the chemical liquid tanks 1a and 2a, respectively. 2b is further comprised of an upright cylinder having exhaust ports 1c and 2c at the top, respectively.

Then, inside the first and second absorption towers 1 and 2, and
Between the inlet ports 1b, 2b and the exhaust ports 1c, 2c, there are circular receiving plates 1d, 2d, 1e, 2e, 1f, 2f, 1 for chemical liquid.
g, 2g, 1h, 2h, 1i, 2i are respectively disposed and fixed in multiple stages in the vertical direction, and each of these receiving plates 1d, 2d..., 1i, 2i has an overflow end. A, A, . . . are formed.

And these upper and lower overflow ends A, A, A
, . . . are annular air permeable guide members B, B, and B, each of which is made of stainless steel wire mesh or the like and is provided in multiple stages.
The air permeable guide member is connected by B, . B,B
, B, . . . guide the chemical liquid from the upper receiving plate (for example, 1d) to the lower receiving plate (for example, 1e) and make it flow down in an annular film shape, and also allow the chemical liquid and the treated object to flow down. gas(
In other words, it functions to bring the gas into sufficient contact with the exhaust gas (exhaust gas).

Reference numerals 3 and 4 designate fluid pumps which pump the chemical liquid in the chemical liquid tanks la and 2a through pipe members 5, 6, 7 and 8 to the receiving plates 1d and 2d.
It is meant to flow upward.

A blower 9, which is an airflow generating means, is attached to the popular port 1b of the first absorption tower 1. It functions to supply air into tower 1.

Then, the exhaust port 1c of the first absorption tower 1 and the second absorption tower 2
It is connected to the popular port 2b by a duct 10.

Chemical solution X stored in the chemical solution tank 1a of the first absorption tower 1
1 is a mixture of the Xa drug and the Xb drug shown in Table 3.

A common property of Xa drugs is that they are oxidizing agents.

The chemical liquid X2 stored in the chemical liquid tank 2a of the second absorption tower 2 is a chemical liquid containing urea.

In addition, although 16 types of X1 chemical solutions are listed in Table ■,
The type of X1 chemical solution is not limited to these.

Furthermore, it has been confirmed that the formaldehyde removal efficiency is further increased when a certain type of catalyst is added to the X2 chemical solution.

The action will be explained below.

Exhaust gas discharged from a heating drying oven (not shown) is forced into the first absorption tower 1 by a blower 9 and flows in the direction of the arrow in FIG.

Then, when the exhaust gas passes through the annular air permeable guide members B, B, B, etc. provided in multiple stages, the exhaust gas passes through the annular air permeable guide members B, B, B,... It reacts with the chemical solution X1 which flows down in an annular and film-like manner along ..., and at this time, the organic solvent component and the tar-like substance in the exhaust gas are reacted and removed.

The exhaust gas from which the organic solvent component and the tar-like substance have been reacted and removed is forced into the second absorption tower 2 through the duct 10, reacts with the chemical solution X2 to remove formaldehyde, and is discharged into the outside air from the exhaust port at 2°C. is discharged to.

Figures 3 to 6 partially show other embodiments of the absorption tower according to the present invention, and the feature of this embodiment is that the reaction between the exhaust gas and the chemical solution is made more sufficient. In addition to adding a breathable member C to the configuration shown in FIG. 1,
The point is that an annular chemical liquid supply pipe D is arranged at the upper end of the breathable member C.

As shown in FIG. 5, the drug solution supply pipe D is provided with a plurality of drug solution discharge ports D1 that open outward, and a cone-shaped plate D2 is attached at a position corresponding to the discharge ports D1. ing.

With this configuration, the chemical liquid discharged from the discharge port D1 is formed into a film by the plate D2 (see FIG. 6), and is supplied to the breathable member C in this film-like state.

Therefore, the chemical solution is sufficiently diffused on the breathable member C, and the reaction with the exhaust gas is sufficiently performed.

Note that the same pump may be used to supply the chemical solution to the pipe D.

As explained above, according to the present invention, it is possible to reliably remove organic solvent components, tar-like substances, and formaldehyde from the foul-smelling exhaust gas generated by a heating drying oven. Since the chemical reaction rate is high due to the reaction with the chemical solution formed in the chemical solution, the reaction for removing the bad odor is completed in an extremely short period of time.

Further, according to the deodorizing device of the present invention, the chemical solution only flows down from the upper receiving plate to the lower receiving plate, and since the breathable guide member is annular, the surrounding surface area can be increased. This has the effect that the pressure loss is extremely small, and the pump is also small and has a low water head.

Further, according to the deodorizing device of the present invention, the amount of circulating water for the chemical solution becomes extremely small, and the chemical solution tank can also be made smaller.

According to the deodorizing device of the present invention, it is small and lightweight, and has a simple structure, so that cleaning and maintenance can be easily performed.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the deodorizing device, Fig. 2 is a top view of the deodorizing device, Fig. 3 is a partial sectional view of an absorption tower of another embodiment, Fig. 4 is a plan view of Fig. 3, and Fig. 5 is a top view of the deodorizing device. The figure is a sectional view of the pipe, and FIG. 6 is a front view of the pipe. 1... First absorption tower, 2... Second absorption tower, 1a, 2a... Chemical tank, 1b, 2b
...Inlet, 1c, 2c...Exhaust port, 1d, 2d, 1e, 2e, 1f, 2f, 1g, 2g,
1h, 2h, 1i, 2i... Circular receiving plate, A, A
,... Overflow one end, B, B,...
- Breathable guide member, 3, 4...Fluid pump, 9
······Blower.

Claims (1)

[Scope of Claims] 1. A method in which foul-smelling exhaust gas containing formaldehyde generated by a heating drying oven for paints, printing inks, adhesives, etc., is annularly formed in a mixture of an oxidizing agent and a surfactant in multiple stages. A step of passing through the formed chemical solution flowing down in a film shape multiple times to cause a chemical reaction and removing organic solvent components and resin-like substances contained in the exhaust gas, and passing the exhaust gas through the above steps in multiple stages. The process consists of a step of passing through a chemical solution containing urea that flows down in a ring-shaped film multiple times to cause a chemical reaction, and mainly reacting and removing formaldehyde contained in the exhaust gas that has passed through the above steps. How to deodorize exhaust gas. 2. A vertical cylindrical body having a chemical tank at its lower end, a popular port for the gas to be treated above the chemical tank, and an exhaust port for the gas to be treated at the top; A circular receiving plate for a chemical solution is arranged in multiple stages inside the vertical tube between the air inlet and the exhaust port, and each has an overflow end for the chemical solution, and the upper and lower sides of the receiving plate The overflow end portions of the chemical liquid are connected to each other, and the chemical liquid is guided to a lower receiving plate to flow down in the form of an annular film, and the chemical liquid is brought into contact with the gas to be treated over a plurality of stages. an annular air-permeable guide member provided in the tank; pump means for supplying a chemical solution from the chemical solution tank onto the uppermost receiving plate of the receiving plates; Two absorption towers are connected in series, each consisting of an airflow generation means for causing gas to flow, and a chemical solution containing a mixture of an oxidizing agent and a surfactant as a main component flowing down into the first absorption tower, and a second absorption tower. A deodorizing device for foul-smelling exhaust gas containing formaldehyde generated from a heating drying oven for paints, printing inks, adhesives, etc., which is constructed by causing a chemical solution containing urea to flow down an absorption tower.