Setting of steam control valve for horizontal thermosyphon reboiler
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The last edit to this post was made by sdkdzxl on 2017-11-23 at 22:14. In HG 20559-1993, \"Specifications for the Engineering Design of Process Systems in Chemical Plants – Part 3: Basic Unit Patterns for Piping and Instrumentation Diagrams\", on page 111, under the requirements for instrument control design of vertical thermosyphon reboilers, it is stated as follows: \"In a vertical tube bundle reboiler, when steam and condensate flow through the shell side, control valves can also be installed on the outlet pipes for steam and condensate. By adjusting the level of steam and condensate within the shell side of the reboiler (thereby regulating the effective heat transfer surface), it is possible to control the amount of heating steam and thus adjust the temperature of the reactor.” ” On page 113, under the requirements for the instrument control design of horizontal thermal siphon reboilers, it is stated as follows: “For horizontal tube-type reboilers (as well as vertical tube-type reboilers when steam and condensate flow in the tube side), the method of using control valves on the steam and condensate outlet pipes to regulate the heating capacity is not employed.” ” What are the reasons taken into consideration for the requirements of the latter? Is the regulation quality poor, resulting in water hammer easily? Seeking advice: On page 92, handshake also mentions the following: \"The shell-and-tube heat exchanger (and reboiler) shown in Figure 3.0.1 uses steam condensate as the controlled parameter; the effective heat transfer area is adjusted by a throttle valve on the condensate pipe, and it is generally not used in cases where steam and condensate flow through the tube side.\" ”
The last edit to this post was made by Watt Energy Saving on 2017-11-25 at 15:50. The factor affecting the heat output of a heat exchanger is given by Q=KA△T. If a control valve is installed on the steam side, that is, at the inlet of the heat exchanger, it is used to regulate the flow rate of steam, thereby controlling the steam pressure and thus controlling the temperature difference △T across the heat exchanger, and ultimately regulating the heat output； If the control valve is installed on the condensate side, that is, at the outlet of the heat exchanger, it is used to adjust the effective heat exchange area A, thereby controlling the heat output. The former is mainly used in situations where the load varies to some extent; its advantages include sensitive control, rapid heating and cooling, no accumulation of condensate water in the heat exchanger, and high efficiency in heat exchange. The disadvantage is that the steam control valve has a large diameter, there is pressure variation inside the heat exchanger, and low load levels make it difficult to discharge the condensate water. The latter is mainly used in applications where the load is relatively stable, the heat exchanger can withstand corrosion caused by condensate water, and the heat exchange tubes are short. The advantage is that the control valve has a small diameter, the pressure on the steam side of the heat exchanger remains constant, some of the latent heat of the steam can be utilized, resulting in a high heat utilization efficiency. The disadvantages are slow response, potential water accumulation in the heat exchanger, as well as the effects of corrosion and water hammer caused by this accumulation; the heat exchanger should be selected to handle 150% of the designed load. For example, the stable heating and cooling in a hotel is suitable for control on the condensate side, while the variable water used for bathing is suitable for control on the steam side.