Reboiler heat transfer medium flow control issue
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I’m seeking advice from experts: In a reboiler, liquid gas requires some heat to be added in order to vaporize the lighter gas components. We use gaseous ammonia from a compressor; however, after heat exchange, this gaseous ammonia liquefies, which takes up some of the heat exchange surface area. How can the amount of gaseous ammonia fed into the reboiler be controlled? Can it be precisely controlled using the vapor temperature and pressure in the distillation column? Is there a device that can control the flow rate of liquid ammonia leaving the reboiler in order to regulate the amount of liquid ammonia inside the reboiler? Thank you all
Can a flow meter be used to control the flow rate in order to achieve the goal?
Your ultimate goal is the temperature TIC of the distillation column; gaseous ammonia acts as a \"heating agent,\" just like steam does when it condenses and releases heat. 1. If the reboiler calculations take into account the area occupied by accumulated liquid (for condensate subcooling design), then the valve is placed at the condensate outlet, with the TIC directly controlling the valve. For safety reasons, a level indicator LIC is used; the TIC can operate in series with the LIC, or the LIC can override the TIC. The function of the LIC is to prevent the liquid level from dropping to zero. This control adjusts the heat exchange area; the inlet ammonia flow is not controlled. 2. If the reboiler calculation does not take into account the accumulated liquid volume (theoretical saturated condensate), you can choose a TIC to control the inlet ammonia control valve, or you can add an ammonia flow FIC as a secondary loop to the TIC in order to counteract disturbances caused by ammonia pressure. The LIC/LV should also be set up to prevent the liquid level from dropping to zero; however, in this case the control range of the LIC is very narrow (similar to that of a steam trap). This control method regulates the inlet ammonia level, while the heat exchange area remains fully open (without fluid accumulation). The control scheme should be considered simultaneously when calculating the reboiler. Either the TIC controls the inlet or it controls the heat exchange area; it cannot control both at the same time. As for flow rate, it is not a direct control mechanism – the opening degree of the valve \"cooperates\" with the flow rate required by the TIC, meaning that flow rate is a passively controlled parameter.