JPS6037399B2 - Heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat exchanger useful for heating corrosive gases.

Steam gas heaters, which are a type of heat exchanger, generally employ a floating head type or a U-tube type to prevent damage caused by thermal expansion of metal.

This steam gas heater consists of a shell, a tube sheet, a bundle and a tube, the tube being passed through a hole in the bundle and fixed to the tube sheet by welding. There are two ways to use this steam heater: steam flows through the tube side while the heated gas flows through the shell side, and vice versa, but generally speaking, when the heated gas is at low pressure, the heated gas flows toward the shell side. It is advantageous to flow the gas to be heated. Therefore, in exhaust gas treatment plants and the like, a system is adopted in which steam is passed through the tube side and heated gas is passed through the shell side.
When the heated gas flows through the shell side, in conventional heat exchanger type steam gas heaters, the tube sheet, bundle, and outer surface of the tubes come into contact with the heated gas, so there is a problem of corrosion of these metal materials. occurs.

Usually, the material type, wall thickness, etc. of a steam gas heater are determined by considering pressure resistance, strength, and corrosion. Therefore, when the gas to be heated contains acidic gases such as S03, HC1, HF, etc. and dust, such as garbage incinerator exhaust gas, coal-fired boiler exhaust gas, and heavy duty boiler exhaust gas, CI-
Since there is a temperature range (dew point) that creates an extremely severe corrosive environment, it is necessary to select metal materials that are resistant to corrosion. When selecting this material, we also take into account inlet attack, pitting corrosion, crevice corrosion, deposit attack, and stress corrosion cracking when using austenitic stainless steel. It is necessary to use C270 Inconel 625, titanium, etc. Therefore, the manufacturing cost of a steam gas heater is significantly higher than when it is used in a mildly corrosive environment, and the cost reduction as a system, which is the original purpose of a steam gas heater, has not been achieved. There are an increasing number of cases where we have no choice but to give up on hiring.
In addition, vibration noise between the metal bundle and the tube is also a problem. Therefore, we investigated a method of lining or coating only the tube with resin.

In this case, the resin needs to have a thickness of 0.5 ribs or less in consideration of heat transfer efficiency. Furthermore, since the lining tube is intended to prevent direct contact between corrosive substances and metal, it is essential that pinholes, cracks, and peeling do not occur. However, if the bundle is made of metal, it cannot be put to practical use because it comes into contact with holes in the bundle due to vibrations or collisions, causing wear or peeling in a short period of time. The present invention aims to easily and inexpensively manufacture a heat exchanger that can be applied to heating gases containing acidic gases such as S03, HC1, and HF.

The second objective is to realize a heat exchanger that is free from vibration and noise. The configuration of the present invention to achieve such an object is to fix a tube piped inside a shell through which a fluid to be heated flows to a header, and to form a corrosion-resistant resin lining on the outer peripheral surface of the tube. The present invention is characterized in that a tube sheet and a bundle whose surfaces in contact with fluid are covered with a corrosion-resistant resin lining are mounted horizontally on the tube with a buffer ring interposed therebetween. The configuration of the present invention will be explained in detail below based on an embodiment shown in the drawings.

Note that this embodiment is an example of a U-tube type steam gas heater. The U-shaped tube 3 through which the tube flows has one end welded to the high temperature steam header 1 and the pond end to the low temperature steam header 2, respectively.

This U-shaped tube 3 is made by bending a tube material made of carbon steel or stainless steel with sufficient strength into a U shape, and then coating the outer peripheral surface with a corrosion-resistant lining 4. and,
A tube plate 5 and a bundle 7 are fitted with iron into the U-shaped tube 3 with a buffer ring 8 interposed therebetween. This tube plate 5 and bundle 7 also have a heated fluid (not shown) flowing inside the shell (not shown).
Corrosion-resistant resin lining 6 on the surface that comes into contact with the bush (that is, acidic gas)
is covered. Of course, in the case of a movable head type, the tube is a straight tube. The resin linings 4 and 6 may be formed using a known lining method such as a thermoplastic lining material such as vinylidene fluoride, Teflon, ethylene monochloride trifluoride, polyethylene, or polypropylene, or a lining material such as unsaturated polyester or epoxy resin. It is formed by applying hot fluidized bonding method, dispersion method, hand lay-up method, etc.

The resins of the lining 4 of the tube 3 and the lining 6 of the tube plate 5 etc. may be of the same type or of different types. However, since it is desirable that the lining material for the tube 3 be heat resistant and flexible, the above-mentioned lining material is used. The lining construction of the above-mentioned U-shaped tube 3 is as follows:
The tube 3 bent into a U shape is passed through the tube plate 5 with the buffer ring 8 attached and the bundle 7, and then welded to the headers 1 and 2, and then the tube plate 5 and the bundle 7 are attached to the header and bundle 7. I'll do it after I send it in. Alternatively, the tube 3 bent into a U shape may be lined with resin, the buffer ring 8 passed through the steel tube plate 5 and the bundle 7, and then both ends of the tube 3 are welded to each tube 2. do. in this case,
It is desirable to stop the lining 4 at a position where it will not be affected by the heat of welding. Further, the buffer ring 8 is
It is made of a composite material of rubber or asbestos and resin, and is shown in Figure 2A.
, B, it has a cylindrical shape with flanges.

The inner diameter may be larger than the outer diameter of the tube 3 when used for a bundle, but when used for a tube sheet, it is slightly smaller than the outer diameter of the tube 3 to prevent gas leakage. do. In addition, the outer diameter of the ring 8 is the same as the hole in the bundle 7 and the tube plate 5, and there is no bundle 7 at the flange portion, and the structure is such that it does not easily come off due to movement or vibration of the tube 3 with the tube plate 5 in between. It is said that It is preferable that the ring 8 is a one-piece molded product, but it may be cut in one place. In this manner, the present invention provides a structure in which a corrosion-resistant resin lining is applied to the outer peripheral surface of the tube and the surfaces of the tube sheet and bundle that come into contact with the heated fluid, and the tube sheet and bundle are attached to the tube with a buffer ring interposed. Therefore, even if tubes, tube sheets, etc. are made of carbon steel or other materials that are inexpensive but have poor corrosion resistance, they can be prevented from being corroded by gases containing acidic gases.

Further, the presence of the buffer ring prevents the resin lining of the tube plate and the bundle portion from coming into direct contact with each other, so that it does not wear out or peel off, and the generation of vibration noise can be reduced. Further, since the resin-lined tube and tube plate are simply iron-bonded via a buffer IJ ring, manufacturing is simple. In addition, when the steam gas heater of this specific example is installed in a boiler exhaust gas removal device to heat 1000 mm/h of gas extracted from the absorption outlet duct through the bypass, the results of operation for 6 months under the following conditions are as follows: It was confirmed that there was no damage to the bundle, tube plate, or resin lining of the tube, and there was no problem in practical use.

Gas inlet temperature: 50℃ Outlet temperature: 8000Using steam pressure
9k9'G gas pressure
In addition, the vibration noise, which has been a problem with conventional steam gas heaters, was also very small.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional explanatory view showing the structure of a main part of a steam gas heater which is an example of the present invention, and FIG. 2 is a view showing a buffer ring, where A is a plan view and B is a central vertical cross-sectional view. In the drawings, 1 is a high temperature steam header, 2 is a low temperature steam header, 3 is a tube, 4 and 6 are resin linings, 5 is a tube plate, 7 is a bundle, and 8 is a buffer ring. Diagram of blinds*2

Claims (1)

[Claims] 1. A tube that is piped inside the shell through which the fluid to be heated flows is fixed to the header, and a corrosion-resistant resin lining is formed on the outer peripheral surface of the tube, and a corrosion-resistant resin lining is formed on the surface that comes into contact with the heated fluid. A heat exchanger characterized in that a tube plate and a bundle are fitted into the tube with a buffer ring interposed therebetween.