Spiral plate heat exchanger is a new type of heat exchanger, heat transfer efficiency is good, high stability of operation, can work together. Spiral plate heat exchanger is a kind of high efficiency heat exchanger equipment, suitable for vapor-vapor, vapor-liquid, liquid-liquid heat transfer to liquid.
It is suitable for chemical, petroleum, solvent, medicine, food, light industry, textile, metallurgy, steel rolling, coking and other industries. According to the structure, it can be divided into non-detachable (Ⅰ) spiral plate and detachable (Ⅱ, Ⅲ) spiral plate heat exchangers. The current standard is JB/T4751-2003 Spiral Plate Heat Exchanger.
Performance of structure
1, the equipment is made of two rolls, forming two uniform spiral channels, two kinds of heat transfer medium can carry out full countercurrent flow, greatly enhance the heat transfer effect, even two small temperature difference medium, can achieve the ideal heat transfer effect. We have Titanium Tubing here.
Spiral plate heat exchanger
2, the nozzle on the shell adopts the tangential structure, the local resistance is small, because the curvature of the spiral channel is uniform, the liquid flow in the equipment without big turn, the total resistance is small, so it can improve the design flow rate to have a high heat transfer capacity.
3. The end face of spiral channel of type I non-detachable spiral plate heat exchanger is welded and sealed, so it has high sealing property.
Structural schematic diagram
4. The structure principle of type II detachable spiral plate heat exchanger is basically the same as that of non-detachable heat exchanger, but one of the channels can be disassembled and cleaned, especially suitable for heat exchange of viscous and precipitated liquid.
5. The structure principle of type III detachable spiral plate heat exchanger is basically the same as that of non-detachable heat exchanger, but its two channels can be disassembled and cleaned, with a wide range of application.
1. The nominal pressure PN of spiral plate heat exchanger is 0.6, 1, 1.6, 2.5Mpa (namely the original 6, 10, 16, 25kg/cm) (refers to the maximum working pressure of a single channel) test pressure is 1.25 times of the working pressure.
2 spiral plate heat exchanger and medium contact part of the material, carbon steel Q235A, Q235B, stainless steel acid port for SUS321, SUS304, 3161. Other materials can be selected according to user requirements.
3. Allowable operating temperature: carbon steel t=0-+350℃. Stainless steel acid steel t=-40-500℃. Temperature rise and pressure drop range according to the relevant provisions of the pressure vessel, the selection of this equipment, should be calculated through the appropriate process, so that the fluid in the equipment channel to reach the turbulent state. (Generally liquid flow rate 1m/Sec gas flow rate 10m/Sec). The equipment can be put down or stand, but only stand when used for vapor condensation; Used in caustic soda industry must undergo integral heat treatment to eliminate stress.
4. Selection of equipment, should be through the appropriate process calculation, so that the liquid in the equipment channel to reach the turbulent state (general liquid speed ≥0.5m/s; Gas ≥10m/s).
5. The equipment can be put down or upright, but only upright when used for steam condensation.
6. For caustic soda industry, integral heat treatment must be carried out to eliminate stress.
7. When the flow value difference between the two sides of the channel is large, unequal spacing channels can be used to optimize the process design.
Principle of blocking
Compared with the general tubular heat exchanger, spiral plate heat exchanger is not easy to plug, especially sediment, small shells and other suspended particle impurities are not easy to deposit in the spiral channel, mainly reflected in:
1. Because it is a single channel, the deposition of impurities in the channel will be raised to flush it out once the turnover flow is formed;
2. Because there is no dead Angle in the spiral channel, impurities are easy to be flushed out.
The characteristics of
1. High heat transfer efficiency (good performance)
It is generally believed that the heat transfer efficiency of spiral plate heat exchanger is 1-3 times that of tubular heat exchanger. There is no flow dead zone in the single channel of constant section, and the disturbance of the fixed distance column and the spiral channel reduces the critical Reynolds number of the fluid. The maximum heat transfer coefficient of the spiral plate heat exchanger can reach 3000W/ (㎡.k).
2. Effectively recover low temperature heat energy
The spiral plate heat exchanger is made of two sheets, which can recover waste heat and make full use of low temperature heat energy.
3. Strong operation reliability
The end face of the spiral channel of the non-detachable spiral plate heat exchanger is welded and sealed, so it has high sealing and ensures that the two working media are not mixed.
4, low resistance
The nozzle on the shell adopts tangential structure. Relatively low pressure loss, handle large capacity steam or gas; Self-cleaning ability, because the medium is spiral flow, dirt is not easy to deposit; Easy to clean, steam or lye can be used to wash, simple, suitable for installation of cleaning devices; Medium through a single channel, the allowed flow rate is higher than other heat exchangers.
5, can be used in combination with multiple sets
If a single device cannot meet the requirements, multiple devices can be used in combination, but the combination must comply with the following requirements: Parallel combination, series combination, device and channel spacing is the same. Hybrid combination: one channel in parallel, one channel in series.
Instructions for Use
1. During equipment installation, engineers and technicians who are familiar with the system process should be asked for guidance, and the installation process plan should be determined according to this manual, product quality certificate and system process characteristics. In the installation, it should be considered to use the trend of the pipeline to absorb thermal expansion as far as possible, and the installation should be horizontal and positive, without additional stress, so as to avoid adverse effects on the equipment. The pipe connection should make the two flow flow completely countercurrent state to improve the heat transfer effect.
2. The pipe system should be cleaned before installation, and there should be no mud, sand, sundries, etc. left in it; Check whether the heat exchanger is damaged during transportation and whether there are large sundries falling into the pipe mouth.
3. After the installation of the equipment, the equipment and system should be hydraulically tested.
4. After the hydraulic test is completed, the equipment should be insulated.
5. Circulation must be softened or dosed. (According to the low-pressure boiler water quality standard GB1576-96), due to improper water treatment caused by scaling, chemical cleaning can be used to remove scale.
In the production process, because the tube plate of spiral tubeplate heat exchanger by water erosion, cavitation and micro chemical medium corrosion, tube plate weld often leakage, resulting in the mixing of water and chemical materials, production process temperature is difficult to control, resulting in the generation of other products, seriously affect product quality, reduce product grade. After the weld leakage of condenser tube plate, enterprises usually use the traditional repair welding method to repair, the internal stress of tube plate is easy to produce, and it is difficult to eliminate, resulting in leakage of other heat exchanger. Enterprises through pressure, inspection of equipment repair, repeated repair welding, experiment, 2 to 4 people need several days to complete the repair, after several months of use, the tube plate weld corrosion again. Bring to the enterprise manpower, material resources, financial waste, production costs increase. Through the corrosion resistance and scour resistance of the Fushi blue polymer composite material, through the protection of the new heat exchanger in advance, it not only effectively control the weld and sand hole problems existing in the new heat exchanger, but also avoid the use of chemical corrosion of the heat exchanger metal surface and welding points, in the future regular maintenance, can also apply Fushi blue polymer composite material to protect the bare metal; Even if there is leakage after use, it can be repaired in time by Fusblue technology, so as to avoid the impact of long-term surfacing maintenance on production. It is because of this fine management that the probability of heat exchanger leakage problem is greatly reduced, which not only reduces the equipment purchase cost of heat exchanger, but also ensures product quality and production time, and improves the competitiveness of products.
Treatment of leakage
The spiral plate heat exchanger is composed of two closed and independent spiral channels. It is difficult to determine the leak point of the series if there is a series leak in the channel. In order to accurately detect the leak point, the method of drilling is adopted. When drilling, the drilling position should be fixed at one end of the heat exchanger on the same spiral channel, and for the cross-shaped arrangement, in the drilling should also try to ensure that the iron filings do not fall into the heat exchanger, in order to make its channel smooth.
Filling with water to suppress leaks
Never drilled a channel, with the pressure pump to heat exchanger water, and form a certain pressure, then the heat exchanger string leakage position will channeled water, flow to another channel (drilled through the hole channel), and from the leak point of the nearest layer of drilling down the water,(then the heat exchanger drilled through the hole one end should be placed downward), through the dripping water position, can be determined in the first layer Internal leakage, then the heat exchanger the same layer of the undrilled side of the head cut a section as the observation hole, from the observation hole can accurately determine the specific string leakage point.
Repair of internal leakage
1, digging holes: after determining the position of the leak point, from the outermost layer of the heat exchanger corresponding to the leak point, began to cut holes, the order is from the outside, has been cut to the layer of the leak point. The hole cut out should be oval, and the size of the outer layer is large, gradually smaller, generally each layer of the hole size difference of 40mm, such as the leakage point is deep, the hole cut out in the outer layer should be larger.
2, slag removal: after cutting holes, we should carefully clean the oxidized slag left on each layer of plate. This is the key in welding the filling plate and each layer of spiral plate. We can use small hand grinding wheel cleaning the oxidized slag on the chisel and dressing mold.
3, matching repair plate: in order to ensure the quality of repair, from the heat exchanger cut off each layer of sheet material, no longer used, re matching repair plate, the other matching repair plate to use the same material and plate thickness with the heat exchanger spiral plate, the surrounding should be bigger than the heat exchanger each layer cut out of the hole 15mm? 20mm, and also oval, and made of each layer of the heat exchanger spiral plate arc consistent with the arc.
4, welding leakage point and repair plate:
1) When welding the leak point, it is necessary to carefully check whether the leak point is a crack or a sand hole. If necessary, the leak can be cleaned by hand grinding wheel and the groove can be ground to ensure the welding quality.
2) J422 electrode is used in welding repair, the diameter of electrode is 3.2mm, and the current is controlled between 100-120A . The leakage point is welded first, and then each layer of repair plate is welded layer by layer from inside out.
3) The elliptical repair plate is welded closely on the inner arc surface of the heat exchanger. Its purpose is to “facilitate operation and ensure welding quality”.
4) In order to make the oval repair plate smoothly installed into the heat exchanger, a piece of round steel can be welded on the repair plate, and then the oval repair plate can be removed after spot welding.
5) Short round steel supports are also welded between each layer of repairing plates (mainly to increase the mutual stiffness of oval repairing plates). The number of short round steel supports welded on each layer of the repairing plate depends on the size of the repairing plate. Generally, 23 short round steel supports are welded on the outer layers of the larger repairing plate and 1 or 2 short round steel supports are welded on the inner layer of the repairing plate.
6) The outermost steel plate is δ12mm thick, so the original cut steel plate can be directly installed in the original position, alignment welding can be done.
7) In the welding should be done, after welding each layer of oval repair plate, should carefully check the welding position, if there is a trachoma to repair welding, to ensure the welding quality of each layer.
Test the pressure and block the borehole
After the internal leakage point and the repair plate are welded, the pressure water pump is used to fill the passage through the hole at the end and form 0.5? Pressure 1.0MPa, and maintain a certain time, there should be no pressure relief phenomenon. Plug the drilled holes: Drill the short round steel section with the same diameter, plug and weld the drilled holes and observe the holes, and then perform a hydraulic pressure test on the channel. The pressure is 0.51.0MPa, and no leakage should occur. The pressure test process should be noted :1) before cutting holes in the heat exchanger, the chemical substances remaining in the heat exchanger should be blown by steam, so as to avoid combustion and safety accidents during gas cutting. 2) Before repairing the heat exchanger, it should be confirmed whether the corrosion is serious and decide whether it is necessary to repair.
Corrosion protection technology
1. Electrochemical protection law
Electrochemical protection is divided into cathodic protection and anode protection. Cathodic protection is the use of external DC power supply, make the metal surface of the anode into the cathode and be protected. This method consumes a lot of electricity, costs a lot and uses very little. Anode protection law is to connect the protected equipment to the anode of the external power supply, so that the metal surface passivation film, so as to achieve protection. The cost of carbon steel spiral plate heat exchanger is low, but the corrosion resistance is poor. The sacrificial anode protection technology can improve the service life of spiral plate heat exchanger, but the protection effect of this technology is limited to the limited length of the pipe entrance, and it is difficult to realize cathodic protection deep inside the pipe, so the application of sacrificial anode protection in spiral plate heat exchanger is greatly limited.
2. Corrosion-resistant materials
The use of corrosion resistant materials (such as binye stainless steel, Hasloy, titanium, titanium alloy, copper, etc.), these materials have strong corrosion resistance, can improve the service life of spiral plate heat exchanger, but these high corrosion resistance materials are expensive, high manufacturing cost, one-time input cost is large, enterprises generally difficult to accept, difficult to promote.
3. Anti-corrosion coating method
On the metal surface, through a certain coating method, covered with a layer of corrosion resistant coating protective layer, to avoid the direct contact between the metal surface and the corrosive medium. This technology method is the most economical and effective, initially used to prevent the corrosion of gas medium, the paint used is mostly organic polymer mixture solution. People gradually to anti – oil and anti – solvent coating, high temperature coating, heavy anti – corrosion coating and special environment coating direction development.
4. Method of adding corrosion inhibitor
In corrosive medium, add a small amount of certain substances, and these substances can make the corrosion of metal greatly reduced, or even stop, this kind of substance is called corrosion inhibitor. The addition of corrosion inhibitor should not affect the production process and product quality as the principle.
The phenomenon and mechanism of metal erosion are complex and involve a wide range. According to the reaction mechanism, metal erosion can be divided into chemical erosion and electrochemical erosion. Electrochemical erosion caused by electrochemical interaction between metal surface and electrolyte solution is the most common and common erosion. Electrochemical erosion usually occurs in the form of stress erosion, pitting corrosion (small hole erosion), crevice erosion and other local erosion.
The main purpose of erosion and protection is to increase production and save.
Advantages and Disadvantages
Advantages: The helical plate heat exchanger has a compact structure and a large heat transfer surface per unit volume. For example, the heat transfer surface of the helical plate heat exchanger with a diameter of ￠1500mm and a height of 1200mm can reach 130m2. The fluid flow rate in the spiral plate is higher, and the fluid flows along the spiral direction, the stagnant layer is thin, so the heat transfer coefficient is large, the heat transfer efficiency is high. In addition, because of the high velocity, the dirt is not easy to stay.
Disadvantages: spiral plate heat exchanger requires high welding quality, maintenance is more difficult. Large weight, poor rigidity, screw plate heat exchanger transport and installation should pay special attention to.
The production practice has proved that the spiral plate heat exchanger is not easy to plug compared with the general tubular heat exchanger, especially the suspended particle impurities such as sediment and small shells are not easy to deposit in the spiral channel. One is because it is a single channel, the deposition of impurities in the channel will be raised to wash it off once the turnover flow is formed, and the other is because there is no dead Angle in the spiral channel, impurities are easy to be flushed out.