Application of Rotary Valve in Refining and Chemical Plant Zhao Quanqing (Mobile Division of Jinxi Petrochemical Company, PetroChina Company Limited, Jinxi 125001, Liaoning, China) Abstract: The rotary valve is analyzed in adjustable range, tight shut-off, circulation capacity, Corrosion, no external leakage and other aspects of the characteristics of the rotary valve in the oil refining plant pointed out the application trend of Chinese herbal medicine. The use of rotary valves helps to increase the economics of long-cycle production runs of large refinery and petrochemical plants. Key words: rotary valve; adjustable range; tight shut-off; flow capacity; anti-cavitation CLC: TH862.7 Document code: B Article ID: 1007-7324 (2001) Components in the process of industrial production process has always played a very important role, the performance of the control valve directly affects the product yield and pass rate, or even normal production. With the development of process technology and control technology, the scale of refinery and petrochemical plants is becoming larger and larger and the volume of treatment is increasing. As a result, even small percentage of valve performance can be greatly enhanced. Based on this situation, the demand for control valves in large refinery and petrochemical plants is getting higher and higher, and the advantages of rotary valves themselves make the rotary valves more and more widely used than the traditional ones. A rotary valve features Valve is usually divided into straight-line program and rotary two categories. Straight-stroke valves allow or shut off the flow of fluid through a rectilinear moving part such as a ram. Straight-travel valve has globe valve, gate valve, diaphragm valve and so on. Rotary valves allow or shut off the flow through a rotating part. Rotating parts can rotate 90 º rotary valve called 1/4 rotary valve. Sometimes 1/4 rotary valve classification can be extended to less than 270º rotation angle of the valve. Rotary valve generally has the following characteristics. 1.1 Adjustable wide range of adjustable in the process industry is the most critical, large adjustable rotary valve to 150: 1 (VALTEK ball valve can be adjusted up to 300: 1, butterfly valve and cam valve can be flexed Adjustment range of 400: 1). The corresponding cut-off valve adjustable range of 30: 1, which means that the rotary valve can provide 5 times the cut-off valve wide adjustable range. For example, the maximum flow rate is 1000L / min, the shut-off valve can effectively reduce the flow rate to 30L / min, while the rotary valve can adjust the flow rate to less than 10L / min. The more accurate the key valve control flow, The better repeatability, which directly reduces the rate of product failure in the process industry. Two features of eccentric rotary valve to improve its adjustable range, the first is its orifice design, eccentricity is an effective 1/4 circle, eccentric spool V-shaped, while the traditional spool of the circle Shaped, when the eccentric rotary valve is closed, the small V shape allows for very precise control at low flow rates and for large flow rates it opens the valve almost to the same diameter as the pipe. The second is the implementation of the machine's travel rotary valve actuator with a certain stroke membrane and cylinder two, 1 "(1" = 25.4) globe valve stroke is about 3/4 "-7/8", while the rotation Valve stroke exceeds 2 ". For any other size valve, the greater the input stroke, the better control at the working end. High Adjustable Ratio Control Valve Provides the exact ratio required by the recipe, regardless of flow rate Size, and traditional virtues of linear or regulating valves no longer fit the task of rotating valves to reduce the cost of the control valve in the life cycle of the plant while increasing device performance. A wide range of rotary valves allows the user to increase the level of tight shut-off , Resulting in higher cost / benefit targets Metal seat with liner made of special material to extend valve life and improve valve performance Simple rotary design minimizes maintenance and reduces production Cost .1.2 Strictly cut off the linear valve stem is the stem out of the valve body, each cycle with a product, for the straight stroke design to avoid leakage is difficult, it Undesired products are introduced into the production system and can lead to larger plant-level external leaks Rotation The hard-to-spin rotary design essentially does not have this problem because it uses a low-hysteretic, high-thrust cylinder Actuators that provide more accurate and higher stability than other types of actuators and are capable of providing long-term, close-off metal seats 1.3 Flow Capability The flow capacity of a large, small, straight stroke is a fraction of the flow capacity of the pipeline , The ability to increase the flow capacity is to increase the size of the linear actuator, which is usually larger than the pipe size.The capacity of the rotary valve is about 2 to 3 times the same size of the linear actuator, the rotary valve can be used to increase the blending amount without changing The size of the feed line can greatly reduce the cost. For this reason, some rotary valves have been designed as flange connections instead of stop valves, and are equipped with connecting bolts, even more than the shut-off valves they replaced Cheaper.1.4 Anti-cavitation processes Throttling in the industry can cause significant cavitation, which can damage the pipe and create unacceptable Noise level, but also can cause disturbance to the measurement system, resulting in unclear or unsafe readings. The rotary valve has a strong design, which greatly reduces the valve failure caused by the water hammer phenomenon. At the same time, the valve core can absorb some excess energy , Significantly reducing cavitation and related problems.1.5 No external leaks Standard rotary valves are designed to leak 100 times more than standard shut-off valves and the movement of the stem of the shut-off valve pulls the dust out of the sand Into the valve to damage the graphite packing in the rotary valve stem only for rotary motion, so as not to damage the packing, to avoid external leakage .6 Maintenance costs and spare parts Metal seat rotary valve than the valve spare parts to be less It is usually easier to maintain it. 2 Types of Rotary Valves 2 .1 Classification by Type Rotary Valves There are 3 types of butterfly valves, butterfly valves, ball valves and plunger valves. Butterfly valve is through the baffle or blade to the shaft as the center rotation angle to control the flow direction. The baffle or blade looks a bit like a butterfly. Butterfly valve can cut off or adjust the role of slurry or with suspended solids for the fluid. Ball valve spool is a spherical body with a round hole, when the valve is open position allows the flow of fluid, the spherical body rotated 90 º cut off the logistics. Ball valve can play the role of cut off regulation, its pressure drop is small, suitable for viscous and corrosive fluids, slurry cryogenic fluid. Ball valve can also be used for high temperature, high pressure fluid. Plunger valve spool is the middle of the cone-shaped or cylindrical plunger with a hole, when the plunger hole and the flow of reconciliation fluid can pass, when the plunger is rotated 90 ° in any direction when the flow path is cut off. Plunger valves are commonly used for on / off control. 2.2 According to the operation classification Rotary valve in accordance with the operation mode has the following types: manual valve, automatic valve and control valve. The manual rotary valve is operated by hand and is operated by manual actuators such as the rear lever, gears, rear wheels, etc., including a part that can be rotated by 90º. The actuator opens and closes the valve by operating the valve stem and flow control element. Automatic rotary valve includes an automatic actuator, the use of external energy to automatically control or remote control valve switch. Automatic valves should generally be used in the following situations: Large valves (eg valves larger than 8 "(1" = 25.4 mm)), valves that are difficult to operate manually, or valves that are operated in a toxic or other harsh environment Most valves that operate in emergency situations require valves that must be closed quickly; valves that fit all flow paths in a batch process, most of which can be operated by electric and pneumatic actuators. The rotary control valve can be operated at a specific opening. Such valves include an actuator that can generate a corresponding rotation angle depending on the size of the electrical signal. Butterfly valves are commonly used in low pressure large diameter, less stringent requirements for leakage control. Rotary control valve is a control valve, the control valve also includes some straight-stroke valve such as globe valve, gate valve, diaphragm valve. Automatic rotary cut-off valve is not a control valve because it can only be limited to on and off. 3 Rotary Valve Trends in Application 3.1 Automatic Valves Replacing Manual Valves Has Been a Trend in Industrial Applications As the automation of refinery and petrochemical plants worldwide increases, the demand for automatic and regulated rotary valves continues to grow, while demand for manual valves is reduced . Valve application technology development in the future should focus on the valve actuator and positioner to facilitate the work of the valve can be connected to a personal computer, PLC, DCS. Such as the use of digital positioner by increasing the accuracy of the control valve to improve valve control performance, the successful application of If the ND800 digital positioner for rotary control valve, you can make the process variable range of 50%, and then through the control Valve Features Valve Positioner Electronic features are matched to further improve control performance. Typical applications such as HART Browser Field Browser software. Compared with the shut-off valve, the control valve is more suitable for continuous production process. Through the adjustment function, the control valve can change the size of the flow according to the input parameters to keep the set value unchanged. In many cases, both shut-off valves and control valves are required, as in refineries, 1/4 turn shut-off valves are used as safety shut-off valves. A control valve is usually used with two shut-off valves, which act to isolate and shut off the flow of fluid when disassembly control is at a premium. The electric actuator will gradually replace the pneumatic actuator because the electric actuator does not require installation and maintenance of the gas supply lines and compressors and can be more closely connected to the positioner and can avoid the conversion of prizes to gas signals. The other development direction of the rotary valve is to improve the performance of the valve by improving the design of the valve seat and the material of the valve seat to reduce the external leakage of the valve. Smart valves with control and positioning will make the market more and more widespread as manufacturers reduce costs and manufacturing needs increase productivity. 3.2. Trends in place of straight-stroke valves Rotary valves offer many advantages over straight-stroke valves (see Section 1 of this paper) because rotary valves can replace straight-stroke valves such as gate valves in many cases. Especially with the implementation of the Clean Air Act (CAA) amendment, it is becoming more and more necessary to prevent leakage outside the valve. The CAA Amendment proposed in 1990 included 189 Volatile Sources of Air Pollution (VHAPS), of which 150 are volatile organic compounds (VOCS). The latest CAA Amendment, adopted in April 1997, includes a quality improvement program in addition to the leak detection and repair (LDAR) program of the previous version. The CAA Amendments add to the investment made by chemical companies, refineries and other valve manufacturers that use straight-stroke valves to prevent leaks outside the valve. The CAA Amendment and its resulting control leakage have prompted manufacturers of manual valves, automatic valves, and control valves to adopt new techniques to design their valves to reduce external leakage of the valves. In general, the use of rotary valves is an effective measure to reduce external leakage, which means that rotary valves have a tendency to replace programmed valves. According to the WMA (Valve Manufacturer Association) market share, this trend is also illustrated: According to the data provided by the VMA, the volume of ball valves, industrial butterfly valves and plunger valves shipped in the United States in 1996 (VMA records ball valves , Industrial Butterfly Valves and Plunger Valves. In addition to this, the VMA tracks automatic valves as a separate category. Instead of recording the individual sales of quarter-turn adjustments, VMA classified them as automatic valves This type is provided by VMA for data on the shipments of US suppliers, including exports but including imports. This amount includes 1.04 billion U.S. dollars, including manual valves and automatic valves, but does not include regulating valves. Ball valves accounted for the largest percentage, accounting for 54.2% of the total, industrial butterfly valves accounting for 26.2%, and the remaining 19.6% for the plunger valves (see Table 1). Table 1 United States 1996 Manual and Automatic Ball Valves, Industrial Butterfly Valves and Plunger Valves Ship Type Percentage Sales,% Ball Valves 565.5 54.2 Industrial Butterfly Valves 273.0 26.2 Plunger Valves 204.0 19.6 4 Rotary Valve Applications 4 .1 In Refining Plant reconcile the application of the system For the reconciliation system in the refinery, in order to improve the quality of reconciliation, often require a variety of oil involved in the reconciliation must be accurately and quickly injected and cut off, which often require the use of a higher cut-off control valve, In order to provide accurate fluid blending regardless of the flow rate of each flow path. Conventional linear or globe valves are no longer suitable for this application. Rotary valves offer the advantages of the above-described advantages, resulting in higher cost performance in such applications. To the user's long-term operation to bring greater benefits. 4.2 Application in Intermittent Operation Rotary shut-off valves are widely used in the batch process industry, especially in the chemical industry (such as synthetic rubber and synthetic plastics), fine chemicals, food, beverage, pulp and paper, and pharmaceutical A wide range of applications. During the batch process, it is often necessary to add a certain amount of material to the vessel or reactor. This is the typical case of rotary shut-off valves, which can be opened and kept at the required flow and then shut down. 1/4 (0 ~ 90º Stroke) Swing shut-off valve also has advantages over straight-stroke valve such as gate valve and large angle valve switch. 5 Conclusions With the integration and enlargement of refinery and petrochemical plants, the requirements for precision and adaptability of instrumentation and control systems are becoming more and more stringent in the production process of refinery and petrochemical plants. The performance of the control valve as a component of the control system is controlled by The impact of quality on the economic benefits of petrochemical plants is growing. Whether it is to expand the scale of production in the future or to improve the quality of control, require us to use the control valve not only to consider a one-time investment in the construction period, but also pay more attention to the operating costs of the production period. With the rotating valve features increasingly recognized and accepted by the people, it will surely get more and more widely used in large-scale refining and petrochemical plant. Economic Efficiency of Long Period Production and Operation of Large Refining and Chemical Plant. Type Sales Percentage,% Ball Valves 565.5 54.2 Industrial Butterfly Valves 273.0 26.2 Plunger Valves 204.0 19.6
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