A corrosion-resistant hot and humid gas heat exchanger

Abstract

This invention provides a corrosion-resistant humid gas heat exchanger, comprising a high-temperature heat exchanger and a low-temperature heat exchanger. Humid gas passes sequentially through the high-temperature and low-temperature heat exchangers. Both the high-temperature and low-temperature heat exchangers include upper and lower tube sheets and heat exchange tubes disposed between the tube sheets. A cold source flows through the heat exchange tubes, and the humid gas laterally washes over the heat exchange tubes for heat exchange. The key feature is that the corrosion resistance of the heat exchange tubes in the low-temperature heat exchanger increases progressively along the airflow direction. By enhancing the corrosion resistance of the downstream heat exchange tubes, this invention improves overall corrosion resistance, further reduces costs, and extends service life.

Description

Technical Field

[0001] The invention relates to a heat exchanger dedicated to hot and humid gas, and mainly relates to the technical field of heat and water recovery from hot and humid air. Background Art

[0002] Heat exchange equipment is widely used in chemical industry, oil refining, power, food, light industry, atomic energy, pharmaceutical, machinery and many other industrial sectors. In chemical enterprises, the investment in heat exchange equipment accounts for about 10% to 20% of the total investment; in oil refining enterprises, it accounts for about 35% to 40% of the total investment. Affected by the global energy crisis, in order to reduce energy consumption, along with the rapid increase in demand for heat exchangers in industrial production, the performance requirements for heat exchangers are also getting higher and higher.

[0003] In recent years, although compact and efficient heat exchange equipment has been applied in some fields, such as corrugated plate heat exchangers, plate-fin heat exchangers, spiral plate heat exchangers, etc., shell and tube heat exchangers still occupy a dominant position in heat exchange equipment. Its high reliability and wide adaptability are irreplaceable by other efficient heat exchangers. Many processes have the characteristics of high temperature, high pressure, high vacuum, high corrosion, etc., and shell and tube heat exchangers have the advantages of wide range of material selection, convenient cleaning of heat exchange surface, strong adaptability, large processing capacity, high temperature resistance, high pressure resistance, etc., so shell and tube heat exchangers are still widely used in chemical industry, oil refining, petrochemical industry, pharmaceutical industry, nuclear power and many other industries.

[0004] Currently, the research on shell and tube heat exchangers is basically focused on heat exchange, but there is no relevant research on heat exchange of humid hot gas and water recovery. Therefore, the present invention improves the existing heat exchanger so that it can recover water while performing heat exchange. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a humid hot gas heat exchanger, which can recover water in the humid hot gas while exchanging heat.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A corrosion-resistant hot and humid gas heat exchanger, the heat exchanger comprising a high-temperature heat exchanger and a low-temperature heat exchanger, the hot and humid gas passes through the high-temperature heat exchanger and the low-temperature heat exchanger successively, the high-temperature heat exchanger and the low-temperature heat exchanger both comprising upper and lower tube sheets and heat exchange tubes arranged between the tube sheets, the heat exchange tubes flow through a cold source, and the hot and humid gas laterally flushes the heat exchange tubes for heat exchange; it is characterized in that, along the flow direction of air, the corrosion resistance of the heat exchange tubes of the low-temperature heat exchanger becomes better and better.

[0008] As an improvement, the corrosion resistance of the heat exchange tubes of the low-temperature heat exchanger is getting better and better along the air flow direction.

[0009] As an improvement, the lower tube plate of the low-temperature heat exchanger is a water tank structure, which is open on the top and closed on the other sides. The lower surface of the water tank structure is provided with tube holes for the heat exchange tubes to pass through, and the lower surface of the water tank structure is provided with a drainage pipe.

[0010] As an improvement, the drainage pipe in the low-temperature heat exchanger passes through the lower header from the lower surface of the tube plate and comes out from the lower surface of the lower header.

[0011] As an improvement, when condensed water is detected in the high-temperature heat exchanger, the number of cold sources entering the heat exchange tube is reduced, while the number of humid hot air entering the high-temperature heat exchanger is increased. By increasing the number of heat sources and reducing the number of cold sources, the condensed water evaporates and enters the low-temperature heat exchanger.

[0012] As an improvement, the formation of condensed water can be detected by infrared means.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1. The present invention can increase the overall corrosion resistance by increasing the corrosion resistance of the downstream heat exchange tubes, further reduce costs and increase service life.

[0015] 2. The present invention divides the heat exchanger into two parts, namely the high-temperature heat exchanger and the low-temperature heat exchanger. The heat exchanger can be used to output cold sources of different temperatures to meet different needs. At the same time, the heat exchange and water recovery can be separated, so that the high-temperature part is concentrated for heat exchange, and the low-temperature part performs low-temperature heat exchange while recycling water, inputs a low-temperature heat source, ensures sufficient recovery of heat and water, and improves the efficiency of heat exchange and water recovery.

[0016] 3. The present invention changes the distribution density of the downstream cooling pipes, so that the overall water distribution is uniform, avoiding the situation where some of the cooling pipes are dry and some are too much, thereby ensuring the service life of the pipes and sufficient condensation and recovery of water. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the moist hot gas heat exchanger of the present invention.

[0018] Figure 2 It is a schematic structural diagram of the high temperature heat exchanger of the present invention.

[0019] Figure 3 It is a schematic structural diagram of the low-temperature heat exchanger of the present invention.

[0020] Figure 4It is a structural schematic diagram of the lower tube sheet of the low-temperature heat exchanger of the present invention. DETAILED DESCRIPTION

[0021] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] like Figure 1-3 As shown, a humid hot gas heat exchanger comprises a high temperature heat exchanger 1 and a low temperature heat exchanger 2, and the humid hot gas passes through the high temperature heat exchanger 1 and the low temperature heat exchanger 2 in sequence. Figure 2 As shown, the high temperature heat exchanger includes an upper tube sheet 11 and a lower tube sheet 12 and a heat exchange tube 13 arranged between the upper and lower tube sheets. The heat exchange tube flows through the cold source, and the hot and humid gas flushes the heat exchange tube 13 horizontally to exchange heat with the cold source in the heat exchange tube; Figure 3 As shown, the low-temperature heat exchanger 2 includes an upper tube sheet 21, a lower tube sheet 22 and a heat exchange tube 23 arranged between the upper and lower tube sheets. The heat exchange tube 23 flows through a cold source, and the humid hot gas horizontally flushes the heat exchange tube 23 to exchange heat with the cold source in the heat exchange tube.

[0024] like Figure 3-4 As shown, the lower tube plate 22 of the low-temperature heat exchanger 2 is a water tank structure, which includes a bottom plate and a vertical plate 27 extending upward from the edge of the bottom plate. The top of the water tank structure is open and the other surfaces are closed. The bottom plate of the water tank structure is provided with tube holes for the heat exchange tubes to pass through, and the lower surface of the water tank structure is provided with a drainage pipe 26.

[0025] The present invention divides the heat exchanger into two parts, namely the high-temperature part heat exchanger and the low-temperature part heat exchanger, and can use the heat exchanger to output cold sources of different temperatures to meet different needs. At the same time, the heat exchange and water recovery can be separated, so that the high-temperature part is concentrated for heat exchange, and the low-temperature part performs low-temperature heat exchange while recovering water, inputs a low-temperature heat source, ensures sufficient recovery of heat and water, and improves the efficiency of heat exchange and water recovery.

[0026] Preferably, the cold source in the heat exchange tube 13 and the heat exchange tube 23 is the same fluid. The fluid enters the heat exchange tube 13 and the heat exchange tube 23 respectively through the flow splitting mechanism.

[0027] Preferably, the cold sources in the heat exchange tube 13 and the heat exchange tube 23 are different fluids. By heating different fluids, different heat exchange requirements can be met.

[0028] Preferably, the upper and lower tube sheets of the high-temperature heat exchanger and the low-temperature heat exchanger are both rectangular.

[0029] As an improvement, Figure 2 As shown, the high temperature heat exchanger includes an upper header 14 and a lower header 15, which are connected to upper and lower tube sheets, or the upper and lower tube sheets respectively constitute the lower and upper surfaces of the upper header 14 and the lower header 15, for diverting and converging the cold source.

[0030] As an improvement, Figure 3 As shown, the low-temperature heat exchanger includes an upper header 24 and a lower header 25, which are connected to upper and lower tube sheets, or the upper tube sheet forms the lower surface of the upper header 24, and the bottom plate of the lower tube sheet forms the upper surface of the lower header 25, which is used to divide and merge the cold source.

[0031] As a preference, Figure 3 As shown, the drainage pipe in the low-temperature heat exchanger passes through the lower header from the lower surface of the tube plate and comes out from the lower surface of the lower header.

[0032] As an improvement, the hot and humid gas flows in a horizontal flow channel, and the heat exchange tubes are vertically arranged in the horizontal flow channel.

[0033] As an improvement, a temperature sensor is provided at the gas outlet of the high-temperature heat exchanger to detect the gas temperature at the outlet. The detected gas temperature is used to control the cold source flow entering the heat exchange tube of the high-temperature heat exchanger. If the detected temperature of the high-temperature heat exchanger outlet gas is lower than the set value, the controller controls to reduce the cold source flow entering the heat exchange tube of the high-temperature heat exchanger. If the detected temperature of the high-temperature heat exchanger gas is higher than the set value, the controller controls to increase the cold source flow entering the heat exchange tube of the high-temperature heat exchanger.

[0034] By means of automatic control, the gas temperature outputted by the high temperature heat exchanger is kept above the dew point to avoid the formation of water condensation. Preferably, the temperature setting value is 5-8 degrees Celsius higher than the dew point temperature of the gas.

[0035] As an improvement, when condensed water is detected in the high-temperature heat exchanger, the number of cold sources entering the heat exchange tube is reduced, while the number of humid hot air entering the high-temperature heat exchanger is increased. By increasing the number of heat sources and reducing the number of cold sources, the condensed water evaporates and enters the low-temperature heat exchanger.

[0036] As an improvement, the formation of condensed water can be detected by infrared means.

[0037] As an improvement, the heat exchange tube distribution density of the low-temperature heat exchanger is increasing along the flow direction of the gas. The present invention changes the distribution density of the heat exchange tubes of the low-temperature heat exchanger, so that the water distribution is uniform as a whole, avoiding the distribution of water on the heat exchange tubes being dry or too much, thereby ensuring the service life of the heat exchange tubes and sufficient condensation and recovery of water.

[0038] As an improvement, along the flow direction of the gas, the heat exchange tubes of the low-temperature heat exchanger are distributed at a higher and higher density. The above arrangement can further ensure uniform distribution of condensed water.

[0039] The density of the heat exchange tubes of the low-temperature heat exchanger changes according to the following rules:

[0040] The total length of the heat exchange tube in the gas flow direction is L, and the density at the most downstream position is M 下 , the distribution density M at a distance l from the most downstream position is as follows: M = b*M 下 +c*M 下 *((Ll) / L) a ,

[0041] 1.079 <a<1.111,0.996<b+c<1.012,0.828<b<0.833。

[0042] As l / L increases, a gradually increases.

[0043] 1.089 <a<1.095,b+c=1,0.830<b<0.831。

[0044] The above optimization formula is obtained through a large number of experiments and numerical simulations, which can achieve the most optimized distribution of heat exchange tubes, and can optimize the service life of the tubes and the sufficient condensation and recovery of water, thus better meeting the needs of the invention of this application.

[0045] As an improvement, the corrosion resistance of the heat exchange tubes of the low-temperature heat exchanger is getting better and better along the air flow direction. The main reason is that the downstream temperature is low, which may lead to excessive distribution of cooling water. Therefore, by increasing the corrosion resistance of the downstream heat exchange tubes, the overall corrosion resistance can be increased, further reducing costs and increasing service life.

[0046] By separating the high-temperature heat exchange tube from the low-temperature heat exchange tube, the heat exchange tubes of the high-temperature heat exchanger and the low-temperature heat exchanger can be replaced separately. For example, the corrosion performance of the low-temperature heat exchanger leads to a short cooling tube life, so the replacement frequency is high. By separating the high-temperature and low-temperature, the overall replacement is avoided and the efficiency is improved.

[0047] Although the present invention has been disclosed as above with preferred embodiments, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, so the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A corrosion-resistant hot and humid gas heat exchanger, the heat exchanger comprising a high-temperature heat exchanger and a low-temperature heat exchanger, the hot and humid gas passes through the high-temperature heat exchanger and the low-temperature heat exchanger successively, the high-temperature heat exchanger and the low-temperature heat exchanger both comprising upper and lower tube sheets and heat exchange tubes arranged between the tube sheets, the heat exchange tubes flow through a cold source, and the hot and humid gas horizontally flushes the heat exchange tubes for heat exchange; characterized in that, The lower tube plate of the low-temperature heat exchanger is a water tank structure, which is open on the top and closed on the other sides. The lower surface of the water tank structure is provided with tube holes for the heat exchange tubes to pass through, and the lower surface of the water tank structure is provided with a drainage pipe; the humid hot gas flows in the horizontal flow channel, and the heat exchange tubes are vertically arranged in the horizontal flow channel; along the flow direction of the gas, the distribution density of the heat exchange tubes of the low-temperature heat exchanger is increasing; along the flow direction of the gas, the distribution density of the heat exchange tubes of the low-temperature heat exchanger is increasing; along the flow direction of the humid hot gas, the corrosion resistance of the heat exchange tubes of the low-temperature heat exchanger is getting better and better.

2. The heat exchanger according to claim 1, characterized in that Along the flow direction of the hot and humid gas, the corrosion resistance of the heat exchange tubes of the low-temperature heat exchanger is getting better and better.

3. The heat exchanger according to claim 1, characterized in that The drainage pipe in the low-temperature heat exchanger passes through the lower header from the lower surface of the tube sheet and comes out from the lower surface of the lower header.

4. The heat exchanger according to claim 1, characterized in that When condensed water is detected in the high-temperature heat exchanger, the number of cold sources entering the heat exchange tube is reduced, while the number of humid hot air entering the high-temperature heat exchanger is increased; by increasing the number of heat sources and reducing the number of cold sources, the condensed water evaporates and enters the low-temperature heat exchanger.

5. The heat exchanger according to claim 4, characterized in that The formation of condensation is detected by infrared means.

Images