JPS6396489A - Gas processing device - Google Patents

Abstract

PURPOSE:To prevent the bulkhead of a honeycomb body from the accumulation of dust thereon, by a method wherein honeycomb bodies provided with vent holes are arranged in the flow path direction of gas, and gaps, specified times of the diameter of the vent holes, are formed between the honeycomb bodies. CONSTITUTION:A plurality of heat exchanging elements 12, consisting of a ceramic honeycomb body provided with a multitude of parallel vent holes 13, are arranged in series along the flow direction of high-temperature gas including dust. A gap L is provided between the elements 12 consisting of the honeycomb body. The gap L is designed so as to be 2-60 times of the diameter of the vent holes 13 and preferably within the range of 3.5-10 times of the diameter. The opening rate of the vent holes is designed so as to be 80% or more of the area of the end of the heat exchanging element 12. As a result, dust in the gas will never be accumulated on the bulkheads tat the fore end of the honeycomb body and the clogging of the vent holes may be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an improvement in a gas treatment device in which honeycomb bodies are arranged in series.

"Prior art and its problems" To explain a rotary regenerative heat exchanger as an example of a gas treatment device, a honeycomb-shaped heat exchange element with many ventilation holes is used in the evening. The length of the exchange element in the direction of the gas flow path is limited. In particular, when the heat exchange element is made of ceramics, its length is limited by processes such as molding, green body handling, and firing, and the maximum length is about 400 mm, but usually 100 mm.
The length in the direction of the flow path is approximately mm.

In a conventional heat exchanger, a plurality of such heat exchange elements are arranged in series along the gas flow path direction, and
They are arranged adjacent to each other. When heat exchange is carried out by flowing a gas, for example, a gas containing gas, into this heat exchange element, dust may adhere to the position of the ventilation hole on the adjacent end surfaces of the plurality of elements.
In the end, there was a risk of dust clogging in the ventilation holes.

As a solution to this dust blockage, it has been proposed to use a jig such as a rod to flatten the ventilation holes of each heat exchange element, or to completely match the pitches of the many ventilation holes formed. is not possible, and there is still the problem of dust clogging at the eight locations.

On the other hand, as another solution, it is also conceivable to arrange a plurality of the heat exchange elements in rows in the lateral direction (direction perpendicular to the gas flow path).

However, in this arrangement, the cross-sectional area of the flow path in the portion where the heat exchange element is provided increases extremely, and the gas flow rate in that portion decreases. Normally, the transport capacity of dust contained in dust-containing gas is proportional to the 0.6 to 1.0 power of the gas flow velocity, so when the flow velocity decreases as described above, the dust transport capacity decreases and the dust or fall easily,
This cancels out the dust blockage prevention effect achieved by arranging the elements in a row. Moreover, since the cross-sectional area of the flow path must be increased at the portion where the heat exchange element is provided, the heat exchanger itself becomes larger.

``Object of the Invention'' An object of the present invention is to provide a gas treatment device that does not cause dust clogging in the ventilation holes and does not reduce the gas flow rate.

"Summary of the Invention" The present invention provides a gas treatment device in which a plurality of honeycomb bodies each having a plurality of mutually parallel ventilation holes arranged in series along the direction of a gas flow path. Between the mutual honeycomb bodies, from twice the equivalent diameter of the above-mentioned ventilation hole to 60 mm
It is characterized by having double the gap.

In this way, by providing a predetermined gap between the honeycomb bodies, even if the cells of each honeycomb body arranged in series in the flow path direction do not completely correspond to each other, dust can be prevented from flowing along the gas flow. Since the dust is carried, it is possible to prevent dust from accumulating on the partition walls of the honeycomb body on the downstream side.

The reason why the gap between the honeycomb bodies is set to 2 to 60 times the equivalent diameter of the ventilation hole is that high-pressure air is forced to flow through the gas flow path, so-called suit blow, which causes the gas to adhere to the front end surface of the honeycomb body. In order to scatter the dust, it is necessary that the above-mentioned gap be at least twice the equivalent diameter of the ventilation hole, and in order to prevent the gas treatment equipment from becoming unnecessarily large, it is necessary to This is because it is appropriate that the diameter is 60 times or less the equivalent diameter of the ventilation hole.

According to a particularly preferred embodiment of the invention, the gap is 3.5 to 10 times the equivalent diameter of the vent.

By making the above-mentioned gap 3.5 times or more the equivalent diameter of the ventilation hole, dust can be removed even without using suit blowing during normal operation when applied to gas treatment equipment, especially rotary regenerative heat exchangers. It becomes possible to scatter the particles naturally. In addition, by making the above-mentioned gap within 10 times the equivalent diameter of the vent hole, when removing firmly attached dust using a suit blow, it is possible to prevent a decrease in the static pressure of the suit blow fluid, and to prevent the gas from blowing. Processing equipment can be made more compact.

According to a particularly preferred embodiment of the present invention, the porosity of the vents is set to 80% or more of the area of the end face of the honeycomb body in order to prevent a decrease in the static pressure of the suit flow fluid.

In the above description, the gas treatment apparatus will mainly be explained using a rotary regenerative heat exchanger as an example, or the present invention is not limited to this. It can be widely applied to gas processing equipment, such as heat exchangers that use honeycomb bodies as heat storage bodies, heat exchangers that use honeycomb bodies mainly as conduction heat transfer bodies, and heat exchangers that use honeycomb bodies mainly as radiation heat transfer bodies. A heat exchanger to be used, a catalytic reactor that uses a honeycomb body as a catalyst, etc. are also included in the gas treatment apparatus of the present invention.

The dust concentration in the gas flowing through the vents of the honeycomb body is
It is preferable to set it to 50mq/Nm to I09/Nnf.

If the dust concentration is smaller than 50mq/Nrn',
Dust clogging is less likely to occur even if the gaps between the honeycomb bodies are not made as described above. If the dust concentration is greater than 1Oq/Nm, it may be advisable to provide another decontamination device upstream of this gas treatment device, rather than providing the gaps between the honeycomb bodies as described above.

As for the material of the honeycomb body, ceramics such as alumina, mullite, cordierite, β-subodumene, aluminum titanate, and silicon carbide are preferred from the viewpoint of heat resistance and corrosion resistance. It may be made of glass, steel, aluminum, or the like.

The cross-sectional shape of the ventilation holes in the honeycomb body is preferably square, or may be rectangular, hexagonal, triangular, circular, or formed by laminating a flat plate and a corrugated plate, or a corrugated plate and a corrugated plate. But that's fine.

The equivalent diameter of the ventilation holes in the honeycomb body may be 2 mm to 15 mm. When the diameter is smaller than 2 mm, dust tends to clog the vent hole, and when it is larger than 15 mm, gas processing performance such as heat transfer performance and catalytic performance deteriorates.

“Embodiments of the invention” Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, this heat exchange body 11 has a number of heat exchange elements 12 made of a ceramic honeycomb body having a large number of parallel ventilation holes 13, and a heat exchange element 12 having a number of tanks, as indicated by arrows, for exchanging high-temperature dust-containing gas. When arranged in series along the flow direction,
A gap is provided between the heat exchange elements 12.

In the present invention, when the heat exchange element 12 is shown in a cross section perpendicular to the gas flow direction in FIG.
Assuming that the size of the three is the same, it is determined based on the relationship with the equivalent diameter. Here, the equivalent diameter O is determined by the following general formula.

D = (4X wetted area)/(wetted edge length) Here, the wetted area refers to the cross-sectional area of the vent hole 13, and the wetted edge length refers to the cross-sectional inner circumference length of the vent hole 13. Therefore, for example, if the cross section of the ventilation hole 13 is made up of a square with length A on one side, the equivalent diameter will be calculated by calculating it into the above general formula, and the length A on one side of this square will be calculated as A. One defeat.

In this way, the distance is determined in relation to the equivalent diameter of the ventilation holes 13, but if this distance ML is relatively narrow,
When a dust-containing gas flows into the heat exchange element 12, dust clogging occurs in the vent hole 13. This dust clogging occurs as a result of a series of the following phenomena. That is, (1) dust adhesion to the partition wall portion 14 on the front end surface of the heat exchange element 12 on the downstream side with respect to the flow direction of the metal gas;

■ Accumulation of dust on the front end face @ wall portion 14.

(2) Dust adhesion to the inner wall of the vent hole 13 downstream of the front end face and narrowing of the gas flow path.

■Clogging of the gas flow path due to dust.

(However, if the accumulated dust scatters at the beginning of the above process ① or ②, dust clogging will not occur.) Therefore, in the present invention, the above-mentioned interval [
When the equivalent diameter of the ventilation hole 13 is 0, L≧20. With the interval L%, dust can be forcibly removed by soot blowing, that is, by flowing high-pressure air through a nozzle or the like through a gas flow path, rather than by rubbing.

In addition, dust scattering due to the natural flow of dust-containing gas, shi≧3.50 It was confirmed that this is a good thing.

However, when considering an increase in the size of the heat exchange element 12, and more particularly, an increase in the size of the container that accommodates it, it is preferable that Φ≦600.

Furthermore, if the adhesion of dust is strong and the adhering dust is to be removed by suit blowing, it is desirable that the ratio be ≤100 in order to prevent a decrease in the static pressure of the suit blowing fluid. Moreover, this value is reasonable considering the size of the heat exchange element 12 and the size of the container that houses it, even considering the natural scattering of dust.

Therefore, the above gap is 2D≦shi　≦60D or more preferably, 3.50≦L≦IOC It is set within the range of .

In addition, in order to prevent a decrease in the static pressure of the suit blow fluid, it is necessary to suppress irreversible polytropic expansion of the suit blow fluid (usually gas) between the heat exchange elements 12, and for this purpose, the above-mentioned It is preferable that the aperture ratio of the ventilation holes 13 be 80% or more of the end surface area of the heat exchange element 12.

FIG. 3 shows a case where such a heat exchanger 11 is applied to a rotary regenerative heat exchanger 15, which is an example of gas processing equipment.

That is, the heat exchange body 11 is configured to be rotatable around the rotating shaft 16, and each of the 12 heat exchange elements constituting the heat exchange body 11 has a predetermined gap set according to the above conditions. The 6-rotation regenerative heat exchanger 15 includes a fixed exhaust gas inlet 17, an exhaust gas outlet 18, a preheated air outlet 19, a preheated air outlet 20, and a heat exchanger 11 rotating around a rotating shaft 16, and the heat exchanger One half of the body 11 is used as a flow path A for metal heating gas such as exhaust gas, and the other half is used as a flow path B for heated gas such as preheated air. Therefore, the exhaust gas is cooled from the exhaust gas population 17 through the flow path A, and flows out from the exhaust gas outlet 18. Further, the preheated air is heated from the preheated air population 19 through the flow path B,
It flows out from the preheated air outlet 20.

The rotary regenerative heat exchanger 15 is configured such that the heat exchanger 11 is fixed, and the exhaust gas population 17, exhaust gas outlet 18, preheating air population 19, and preheating air outlet 20 rotate relative to it. It's okay if it's done.

Example 1 A heat exchanger 11 made of a ceramic honeycomb body was applied to a rotary regenerative heat exchanger 15 and tested under the following conditions. No pressure loss was observed, and heat could be recovered without pressure loss for 9 days without suit blowing.

Temperature of exhaust gas population 17 140°C to 180°C Temperature of exhaust gas outlet 18 90°C to 110°C Temperature of preheating air population 19 20°C to 35°C Temperature of preheating air outlet 20 85°C to 100°C Dust in exhaust gas Content
0.39/Nrri' dust component Sodium sulfate,
Cross-sectional shape of potassium sulfate and sodium chloride vent hole 13 - Square partition part 1 with side 13 mm
Thickness i of 4 1 mm Gap (4,61D) 60 mm Porosity 86.2% Example 2 The heat exchange body 11 made of a ceramic honeycomb body was prepared in Example 1. Similarly, when the test was applied to the rotary regenerative heat exchanger 15 and tested under the following conditions, no increase in pressure loss was observed for three months despite suit blowing, and there was no evidence of dust adhesion. There wasn't.

Temperature at exhaust gas outlet 17: 240°C Temperature at exhaust gas outlet 18: 190°C Temperature at preheating air outlet 19: 30°C Temperature at preheating air outlet 20: 90°C Dust content in exhaust gas: 5(+/ Nrrr dust component SOx and neutralization in exhaust gas Acidic ammonium sulfate is generated by ammonia inhalation Cross-sectional shape of vent hole 13 - Square BF with 5 sides [section 14
Thickness t 0.5mm gap (7,60)
38mm Porosity 82.6% Example 3 A ceramic honeycomb body supporting platinum was arranged in the same manner as the heat exchanger 11 in Figure 1, and used as a catalyst carrier for decomposing hydrocarbons in exhaust gas. When tested under these conditions without suit blowing, there was no increase in pressure loss and no signs of dust blockage.

Exhaust gas temperature 350℃ Dust content in exhaust gas 0.19/Nm Dust component
Cross-sectional shape of carbon ventilation hole 13 - Thickness of square partition wall 14 with sides of 2.5 mm 0.5 mm Gap gap (480) 120 mm Open area ratio
69.4% Comparative Example A heat exchanger 11 made of a ceramic honeycomb body with a gap equal to or less than the equivalent diameter of the ventilation hole 13 was applied to a rotary regenerative heat exchanger 15 and tested under the following conditions. After one month, the pressure loss increased, and after two years, almost all the ventilation holes 13 were completely blocked by dust. In addition, suit blowouts were performed regularly.

Temperature at exhaust gas inlet 17: 150°C Temperature at exhaust gas outlet 18: 90°C Temperature at preheating air outlet 19: 50°C Temperature at preheating air outlet 20: 100°C Dust content and dust components in exhaust gas Same as in Example 2) Vent hole 13
Cross-sectional shape and thickness t of partition wall portion 14 Example 2. Same gap L
(0,40) 2mm "Effects of the Invention" As explained above, according to the gas treatment apparatus of the present invention,
Since a predetermined gap is provided between a plurality of honeycomb bodies arranged in series in the direction of the gas flow path, the dust in the gas is absorbed by the front end surface of the honeycomb body on the downstream side in the direction of the flow path. The dust can be scattered by the natural flow of gas or by suit blowing without adhering to the gas, thereby preventing the dust from clogging the vent hole, and as a result, reducing the gas flow rate.

[Brief explanation of the drawing]

Figure 1 is a partial sectional view showing the arrangement of the honeycomb body in the gas treatment device of the present invention, Figure 2 is an end view taken along line II-H in Figure 1, and Figure 3 is the gas treatment device of the present invention. FIG. 2 is a sectional view of a rotary regenerative heat exchanger that is an example of the present invention. In the figure, 11 is a heat exchange body, 12 is a heat exchange element, 13
14 is a partition wall, and 15 is a rotary regenerative heat exchanger.

Claims (3)

[Claims] (1) In a gas treatment device in which a plurality of honeycomb bodies formed in a honeycomb shape with a large number of mutually parallel ventilation holes are arranged in series along the gas flow path direction, between the honeycomb bodies A gas treatment device characterized in that a gap is provided between 2 times and 60 times the equivalent diameter of the ventilation hole. (2) The gas treatment device according to claim 1, wherein the gap is 3.5 to 10 times the equivalent diameter of the vent hole. (3) The gas treatment device according to claim 1 or 2, wherein the aperture ratio of the vent holes is 80% or more of the area of the end face of the honeycomb body.