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Therefore, in order to increase the use temperature and pressure of the plate heat exchanger and expand its use range, a variety of welded plate heat exchangers have been developed, manufactured and used at home and abroad. These welded plate heat exchangers have been increasingly used in the heating, cooling, condensation, evaporation and heat recovery processes in the chemical, petroleum, power, metallurgical and other fields. Welded plate heat exchangers are mainly divided into full-welded and semi-welded. This paper only introduces some all-welded welded plate heat exchangers and their applications. 1AlfaRex heat exchanger [ 2, 3 ]
The A lfaRex heat exchanger is an all-welded plate heat exchanger manufactured by AL FA 2LAVAL. Since it does not use elastic gaskets, it can be used at higher temperatures and pressures and can handle corrosive media. Design temperature - 50 ~ 350 ° C, design pressure 5117M Pa (750p sig), higher than the ordinary plate heat exchanger. Under a given heat transfer load, the installation cost is only 1/2 to 1/3 of the shell-and-tube heat exchanger, and the floor space is 1/4 to 1/7. The A lfaRex heat exchanger works in the same way as a conventional plate heat exchanger, with alternating channels for cooling, hot fluid flow, and a complete countercurrent flow pattern. The heat transfer capacity per unit area of ​​the heat exchanger is 20% higher than that of other cross-flow all-welded plate heat exchangers.
The A lfaRex heat exchanger is laser welded, and the heat input is only 25% of the ordinary welding method. Therefore, the welding heat affected zone and the residual stress are small, and the weld is superior to the ordinary weld. The A lfaRex heat exchanger is laser welded only in two directions of the plane of the plate; thus, when the temperature and pressure change, the bundle can expand and contact along the length. This flexibility of the bundle allows the AlfaRex heat exchanger to be used when the temperature and pressure change rapidly; in a typical three-way weld design, fatigue cracks typically occur. In addition to the bundle, the nozzles of the AlfaRex heat exchanger can be bent with changes in temperature and pressure.
The A lfaRex heat exchanger is highly resistant to fouling due to high shear stress due to turbulence in the flow path. Moreover, since the amount of retention is small, it is easy to clean in place. AL FA 2LAVAL recommends the use of filters to remove large particles or other foreign matter. In an application, it has been used continuously for 18 months without the need for cleaning.
The flow rate of the A lfaRex heat exchanger is up to 15114m 3 /m in ( 4000GPM ) and the heat exchange area is 27917m 2 (3000f t2). The sheet material is 316, 316L, T i, Ni and the like.
The A lfaRex heat exchanger can be used in various processes such as heating/cooling of corrosive media (such as organic solvents, hydrocarbons, etc.), batch reaction, heat recovery, hydrocarbon gas cooling, solvent recovery, and refrigeration. 2Compapla te heat exchanger [ 2 ]
The Compap late heat exchanger is a wide-pitch, all-welded plate heat exchanger manufactured by AL FA 2LAVAL. Free-flowing sheet technology for cooling or heating high-fluid fluids containing high percentages of solid particles, suspended solids or fibers, or for poor water quality cooling operations. The heat exchanger couples a series of corrugated sheets with recesses to form a bundle of sheets and forms a corrugated flow path through which the fouling fluid passes (the sheet spacing is 5 to 21 mm). Since there are no points of contact, the free flow channel allows the heat exchanger to process the fouling fluid without causing blockage. The heating or cooling fluid flows over the side of the plate with the recesses, creating a countercurrent or cocurrent flow. Compap late heat exchangers provide optimum inter-plate flow rates and pressure drops to reduce structural velocity. The end of the heat exchanger has two movable doors that can be used to flush the surface of the fouling fluid with water from either end of the bundle. The plate bundle is 100% welded, eliminating the problems associated with the use of gaskets and saving on maintenance costs.
The design pressure on the wide gap side of the Compap late heat exchanger is vacuum ~1.03M Pa (150p sig), and the design pressure on the plate side is vacuum ~1.1M Pa (165p sig). The design temperature is -28.9 to 232.2 ° C (- 20 to 450 u), the flow rate is 0 to 22.7 m 3 /m in (6000 GPM), and the surface area is 0 to 209 m 2 (2250 f t2). Standard plate material is 316L, carbon steel: special plate material is 304L, 317L, 254SMO. 3MAXCHANGER heat exchanger [ 4, 5 ]
The MAXCHAN GER welded plate heat exchanger is a patented heat exchanger (US Patent No.: U SP5469914, U SP 5487427). Produced by the company tra ter. The main feature of such a heat exchanger is that the inlet and outlet of the fluid passage are formed at the ends of the sheet; the ends of the sheet are triangular or V-shaped, extending the length of the opening along each V-shaped side. For each flow passage, the open end edge formed by one of the two sheets is bent and welded to the adjacent sheets to further enlarge the inlet and outlet. Pressure drop and pumping costs are greatly reduced due to the enlarged inlet and outlet of the runner between the plates.
The heat transfer of the MAXCHAN GER heat exchanger is basically the same as that of the plate and frame heat exchanger, but without the gasket. The heat exchanger is very compact, occupying only 30% to 50% of the space of the shell-and-tube heat exchanger. Due to the variable plate spacing and unique geometry, this heat exchanger has a high heat transfer coefficient ("U" value) and a low pressure drop.
The MAXCHAN GER heat exchangers feature an all-welded construction with a large number of raised recesses or sloping corrugations on each plate, providing a large number of pressure-resistant heat transfer contacts. This design enables the MAXCHAN GER heat exchanger to be used for high temperature and high pressure operation. The standard version of the heat exchanger, the maximum operating temperature is 260 ° C (500u), the standard working pressure is 1103M Pa (150p sig); the custom heat exchanger, the design pressure can reach 617M Pa (975p sig), the design temperature can reach 538 °C (1000u).
The MAXCHAN GER heat exchanger uses countercurrent flow and is close to temperatures up to 111°C (2u). It can be used for heat exchange of liquid 2 liquid, steam 2 liquid, gas 2 liquid, gas 2 gas and refrigerant (including ammonia).
The MAXCHAN GER heat exchanger is available in several models. The maximum heat exchange area of ​​a single heat exchanger is 4m 2 (44f t2). When a larger heat exchange area is required, multiple heat exchangers are often used in series, using a common inlet and outlet manifold.
The MAXCHAN GER heat exchanger has a variety of settings for the connection, providing great flexibility during installation. The materials used in the heat exchanger are T i, Hastelloy, Inconel, Monel and other materials. 4 "double plate" structure welded plate heat exchanger [ 6 ]
The "double-plate" structured welded plate heat exchanger is a welded plate heat exchanger invented by the company (see U.S. Patent No. 5,427,424). The heat exchanger consists of two sets of plates, the first set of plates being alternately arranged with the second set of plates in a stacked manner. Each plate pair has two plates with raised recesses to provide a gap between the two plates to form a fluid flow path and create turbulent flow of the flowing fluid. A height-changing recess can be used to reduce the pressure drop while still maintaining turbulence for good heat transfer. The sealed plate leaves a small gap between the opposing plates to allow for possible leakage of spillage to prevent one fluid from being contaminated by another.
The fluid inlet and outlet of each pair of plates are located on either side of the pair of ends. The inlets and outlets of the pair are enlarged to increase flow, reduce pressure drop and pumping costs. The inlet and outlet of each set of plates are connected to a header tank for input and extraction of fluid. Each header box is connected to a header.
The welded plate heat exchanger uses an all-welded construction; this structure is more compact, lighter, less expensive, operates at lower fluid volumes, and has higher operating pressure and operating performance and higher effectiveness. In addition, the heat exchanger is simple in construction, more robust and durable, and easy to manufacture and assemble. 5PLATULAR heat exchanger [ 7 ]
PLA TULAR heat exchanger is a series of all-welded plate heat exchangers produced by BARR IQUANDECHAN GEU RS. Can be used in a variety of industrial processes, especially in the chemical (heaters, coolers, condensers, reboilers, etc.), steel, paper, food and other industries. The PLA TULAR heat exchanger has excellent heat transfer performance and high heat transfer coefficient. In addition, its flow rate is high and it is very compact, reaching 200m 2/m 3 . In recent years, the design range of PLA TULAR heat exchangers has been expanded to focus on the treatment of suspensions, fiber-containing fluids and viscous fluids as well as fouling media. There are also specially designed heat exchangers for steam condensation and VOC recovery under reduced pressure.
PLA TULAR heat exchangers are available in a variety of flow regimes (countercurrent, cocurrent, crossflow) for heat exchange, condensation and evaporation between liquid 2 liquid, liquid 2 gas, gas 2 gas. Good versatility; all structural parameters such as height, length, width, and heat transfer runner spacing are optimized separately, allowing for different types of fluids, pressure drops, and temperatures. It is horizontal or vertical, easy to maintain and can be cleaned mechanically or chemically. PLA TULAR heat exchangers can be made from conventional stainless steel, UB6, INCONE EL, HA STELLO Y and Ti. The sheet is press-formed and has excellent mechanical properties and corrosion resistance. The sheets can be made by electropolishing when needed.
There are two main types of PLA TULAR heat exchangers: X and IJS. The X-type has no housing and generally has two types of channels: one with a recess and the other with a smooth one. The refractory fluid or the fiber-containing fluid and the cleaning fluid are respectively passed. When both streams are clean fluids, both channels can be corrugated to provide maximum efficiency. The IJS type of bundle is mounted in a housing. The IJS type is an all-welded, all-stainless steel heat exchanger with a pressure of 1.2M Pa (12bars) or 2M Pa (20bars), a service temperature of 200°C, a fluid volume of less than 100 liters, and a heat exchange area of ​​0.55. ~13.6m 2. 6BAVEX welded plate heat exchanger [ 1, 8 ]
The all-welded plate heat exchanger developed by BAV EX in Germany for high temperature and high pressure; Japan Chiyoda Company introduced this technology, called Chiyoda 2BAV EX plate heat exchanger. The heat exchanger of this structure is formed by stacking stainless steel pressed sheets having a thickness of 0.2 to 0.8 mm, a width of 360 mm, and a length of 6 m, and then welded by plasma or T IG welding. The heat exchanger can be used at a temperature of up to 1000 ° C under normal pressure and at a normal temperature of 610 to 810 M Pa. Compared with the multi-tube heat exchanger, the total heat transfer coefficient is 2 to 3 times higher, the pressure drop is only 1/2 to 1, the fouling coefficient is 1/10, and the weight is 1/4 to 1/2. The ground is 1/3 to 1/2. This all-welded plate heat exchanger has a maximum heat transfer area of ​​1900 m 2 , a maximum operating temperature of 720 ° C (heat transfer area of ​​290 m 2 ) and a maximum operating pressure of 4.5 M Pa. It is not only suitable for liquid 2 liquid, liquid 2 gas, gas 2 gas heat exchange, but also for phase change heat transfer of evaporation and condensation. 7SIGMAW IG heat exchanger [ 9 ]
The S IGMAW IG heat exchanger is produced by Schm idt2B ret ten. This series of welded plate heat exchangers has no gaskets and all parts in contact with the fluid are made entirely of stainless steel. The heat exchanger plates are optimized for corrugated construction for optimum heat transfer.
The company's newly produced S IGMAW IG welded plate heat exchangers are available in ST 30 and ST 40 models with larger volumetric flow rates (up to 450 m 3 / h) and heat exchange areas (up to 75 m 2 ) for comparison High load. The take-over size is DN 150. The advantages of the S IGMAW IG series all-welded plate heat exchanger are: no gasket and compact structure, safe to use. With T IG welding and optimized welding equipment, the product has a high quality. The heat transfer performance is improved due to the optimization of the sheet corrugation. All parts in contact with the media are free of fillers. Use special materials for hazardous media such as HA STELLO Y, 904L. The operating temperature is high, up to 250 ° C (480u), the operating pressure is higher, up to 2.5M Pa (25bar) or more. The operating cycle is long and requires no maintenance. 8COMPABLOC heat exchanger [ 10 ]
The COM PABLOC welded plate heat exchanger is produced by V ICARB and is a compact, efficient and patented heat exchanger. This heat exchanger is assembled from welded bundles, steel frames and panels, and is a tetrahedral structure.
The plate bundle is made of precision pressing and automatic welding. The column lining is made of resistance welding. The “core†of the heat exchanger consists of welded corrugated plate bundle, column lining and top and bottom cover lining. The bolt connection frame consists of four columns and top. The bottom cover and 4 panels with connectors.
The slab and lining materials are 316L, T i, T i2Pd, Hastelloy C2276, C222, B22, A vesta254SMO, Inco loy825, Nickel 200, Monel, Ta. The panel gasket materials are V ITEX, glass reinforced PTFE, GRA FO IL, flexible graphite and the like.
COM PABLOC welded plate heat exchanger has the following main features: 1) There are no gaskets between the plates, which improves the use temperature and pressure; 2) Special corrugation is used to make the heat transfer performance of COM 2PABLOC welded plate heat exchangers Conventional gasketed plate heat exchangers are equivalent; 3) bolted design, easy to disassemble, easy to clean, repair or replace; 4) COM 2PABLOC welded plate heat exchangers are designed, manufactured and tested in accordance with A SM E specification Sect Ion?, D iv. 1; 5) using a cross-flow arrangement to produce overall countercurrent heat transfer performance; 6) using an adjustable and movable baffle, making the pressure drop suitable for heat transfer performance requirements; 7) It is very compact and therefore has a small footprint and requires minimal installation and maintenance space. A 297.3m 2 (3200f t2 ) COM PABLOC welded plate heat exchanger occupies only 9.29m 2 (100f t2).
The COM PABLOC welded plate heat exchanger uses a pressure of 312M Pa (450p sig) and a temperature of 315°C (600u). There are a variety of specifications, including the CP75 series, the maximum number of plates up to 500, the heat transfer surface area of ​​319.5m 2 .
Since the COM PABLOC welded plate heat exchanger has good heat transfer performance and high use temperature and pressure, it is very economical to replace the shell-and-tube heat exchanger used in the corresponding temperature range with this heat exchanger. Used in oil and gas processing industry, it can be used as crude oil cooler, overhead condenser, etc.; it can also be used in many other industrial processes. 9PACKINOX heat exchanger [ 11, 15 ]
The PACK INOX heat exchanger is a large plate heat exchanger of all welded structure produced by PACK INOX of France. The heat exchanger is mainly composed of a heat transfer plate bundle and a pressure vessel casing. The bundle is sealed in the pressure vessel casing, and all heat transfer processes are carried out in the bundle, using a pure countercurrent operation. An expansion joint is provided between the hotter stainless steel sheet bundle and the relatively cooler pressure vessel housing to compensate for the difference in thermal expansion therebetween. The liquid feed is ejected through the orifice of the spray bar, and the circulating gas from the bottom of the vessel is thoroughly mixed with the liquid ejected from the spray bar through a specially designed venturi and evenly distributed on the bundle. The pressure vessel is pressurized with circulating gas to reduce the pressure difference on both sides of the bundle and protect the bundle. The PACK INOX heat exchanger is installed vertically.
The bundle is made of hundreds of corrugated stainless steel sheets by explosion molding, layer by layer and integral welding on both sides. The special herringbone ripple on the plate makes the PACK INOX heat exchanger an efficient static mixer that provides optimum heat transfer for two-phase flow. The corrugated tops of the mutually intersecting corrugations form contact points for withstanding the pressure difference of the heat transfer medium of the cold and heat flow, and the fluid is in a turbulent state throughout the heat exchange process, and can maintain high heat transfer efficiency. The plate is formed by underwater explosion molding, which has the advantages of accurate forming, high quality and low cost. The surface of the explosion-formed sheet is smooth and the thickness of the wall is uniform. At the same time, because the shock wave of the explosion has the effect of eliminating residual stress, the strain hardening degree of the sheet is small, and only a low level of residual stress is maintained, thereby maintaining the corrosion resistance of the sheet. The length of the plate can reach 15m, and the single piece area is generally above 10m 2 [ 11, 13 ]. The welding of the bundle is automatically welded by T IG (Tungsten Inert Gas Shielded Arc Welding).
The bundle material of the PACK INOX heat exchanger includes various types of austenitic stainless steel, Ti and high corrosion resistant 6Mo austenitic stainless steel. Pressure vessels are typically fabricated from low alloy steel or other materials. Expansion joints are manufactured from Inconel, Inco loy or other materials.
The single heat exchange area of ​​the PACK INOX heat exchanger is 1000m 2 to 16000m 2 or more. A PACK INOX heat exchanger can replace several vertical shell and tube heat exchangers (according to a PACK I2NOX company, it can replace up to 12 vertical shell and tube heat exchangers depending on the application). The typical design temperature is 300-550 ° C, the highest design temperature has reached 650 ° C (1200u); can withstand a large temperature difference between the feed and the effluent. The pressure drop is 0.035 to 0.15 M Pa (0.35 to 1.5 bar, depending on the operation). The fluid pressure can be very high and the design limits are the same as the pressure vessel housing. The heat exchangers listed in the company's reference list have a design pressure of 0.3 to 12 MPa (3 to 120 bar) and a differential pressure of 4 M Pa (40 bar) [11].
The PACK INOX heat exchanger is a welded plate heat exchanger with high heat transfer efficiency and very compact structure (high surface area to volume ratio). The pressure drop is significantly lower than that of the vertical shell and tube heat exchanger, thus reducing the process furnace, recycle gas compressor and refrigeration load. The size of the furnace, compressor and cooler can be reduced, saving investment. Thanks to its compact size and light weight, the PACK INOX heat exchanger saves space and construction and installation costs. Due to the high heat recovery rate of the PACK INOX heat exchanger, the bottleneck of the process unit compressor can be solved by reducing the pressure drop without changing the existing furnace and circulating gas compressor. In one application, a PACK INOX heat exchanger is used to increase the production capacity of the hydrodesulfurization unit by 50%. Due to the high heat exchange efficiency, the work load of the process furnace, the cooler and the compressor can be reduced, energy and fuel consumption are saved, thereby saving operating costs. In addition, PACK INOX heat exchangers are characterized by high reliability and durability, ease of maintenance and operational safety.
Since the first PACK INOX heat exchanger was put into use in the catalytic reforming unit of the Dongs refinery in Elf Petroleum, France in 1982, there have been many sets of catalytic reforming units (new or rebuilt) using PACK INOX heat exchange in the world. The device is mainly used for preheating the feed of the catalytic reformer. In recent years, its application has expanded to the fields of hydrotreating (HDT) and hydrodesulfurization (HDS) for use as feed heat exchangers. For example, in the refinery of Jinling Petrochemical Company of China and the catalytic reforming unit of the Chevron El Segundo refinery in the United States, and the application in the naphtha hydrotreating unit of the Belgian refinery, good results have been achieved [12] , 15]. For example, after application in the refinery refinery of Jinling Petrochemical Company, the pressure drop of the welded plate heat exchanger is significantly lower than that of the vertical shell-and-tube heat exchanger, which not only reduces the reaction pressure of reforming, but also reduces the reforming cycle. The compression ratio of the compressor. The energy recovery rate of the welded plate heat exchanger is obviously higher than that of the vertical heat exchanger, which can recover more heat and save energy and increase efficiency. The heating furnace saves fuel gas 0.311t per hour, saving fuel gas by one year. The economic benefit is 970,000 yuan. When a welded plate heat exchanger is used, the heat exchange temperature of the reaction effluent is reduced to 103 ° C, which is 12.1 ° C lower than that of the vertical shell-and-tube heat exchanger, thereby reducing the load on the air cooler, which also reaches to some extent. The effect of energy saving and efficiency. In addition, the reforming raw material 2 effluent heat exchanger used as the reforming unit originally required several vertical heat exchangers, and now only one PACK INOX welded plate heat exchanger can be used [12].
Currently, in the refining, petrochemical, and gas processing industries, PACK INOX heat exchangers have been used in more than a dozen different processes for use as a combined feed 2 effluent heat exchanger. For example: 1) Catalytic reforming process (including semi-regenerated catalytic reforming and continuous catalytic reforming), which can be used to build or rebuild plants; 2) xylene isomerization process; 3) toluene disproportionation process; 4) pyrolysis gasoline plus Hydrogen process; 5) paraffin dehydrogenation process; 6) gas oil hydrodesulfurization and naphtha hydrotreating. Used in hydrodesulfurization processes, it can also be used as a heat exchanger at the bottom of the stripper; this heat exchanger is different from the standard PACK INOX heat exchanger, eliminating the need for pressure vessels, expansion joints and intermediate bundles. Water injection system for medium operating temperatures and pressures; 7) M TBE unit for cooling reactor effluent. At this point, the PACK INOX heat exchanger was modified to make it a multi-stream reactor effluent cooler. It includes four streams: reactor effluent, cooler separator tank liquid, cooler separator tank gas and propane refrigerant; 8) EB dehydrogenation to styrene monomer; 9) methanol synthesis; 10) gas desulfurization. In addition, the PACK INOX heat exchanger can also be used as a propane 2 propylene condenser, an amine solution heat exchanger, and for processes such as gas processing, seawater cooling, and gas preheating. It is worth noting that in order to adapt to different processes, the PACK INOX heat exchanger of the standard structure is often modified to give some improvements [11].
The above-mentioned German DEG company, Swedish SW EP company, American F lat P lat company, API heat transfer company, Australia MUL 2T ISTACK and other companies also produce a variety of other welded plate heat exchangers [16]. In addition to all-welded plate heat exchangers, there are many types of semi-welded plate heat exchangers (such as semi-welded plate heat exchangers manufactured by AL FA 2LAVAL). There are also some production plants in China that produce welded plate heat exchangers; there are also some patented welded plate heat exchangers, such as the welded plate heat exchangers described in Chinese patents ZL 91202623 and ZL 95230391. In the renovation of old equipment and the construction of new installations, the promotion of the use of various types of welded plate heat exchangers can achieve the purpose of energy saving and consumption, and achieve obvious economic benefits. With the development of welded plate heat exchanger structure and advancement of manufacturing technology, as well as the need for energy saving and material saving, the application of welded plate heat exchangers in petrochemical industry will be more and more extensive.
The plate heat exchanger is a highly efficient compact heat exchanger. Due to its high heat transfer coefficient, small pressure loss, compact structure, convenient maintenance, etc., and with the improvement of structure and the improvement of large-scale manufacturing technology, it has been more and more widely used; in addition to high temperature, high pressure and special media. In addition to the conditions, the use of plate heat exchangers instead of shell-and-tube heat exchangers can achieve significant results. However, the general bulk type plate heat exchanger (detachable plate heat exchanger), due to its own structural limitations, the use pressure does not exceed 215M Pa, the use temperature does not exceed 250 ° C [1], in addition to the presence of fluids and seals The compatibility of the gasket.