Weekly Topic 4.4, Issue 21: Selection of Reboiler Types and Control Methods

The methanol distillation reboiler in our company uses a method of controlling the condensation of steam at the rear of the reboiler; this inevitably reduces the length of the heat exchanger tubes, and thus reduces the heat exchange area. This results in an increased design margin for the heat exchanger (reboiler). Although liquid steam condensate can also be used for heat exchange, it is feared that the efficiency of heat transfer will not be as good as when steam condenses directly on the heat exchange tubes

The methanol distillation reboiler in our company uses the method of regulating the condensate from the steam entering the reboiler; it works well, with no occurrences of liquid slugging, and the control is quite stable. The condensate from the pressure column reboiler is then sent to the pre-column reboiler for heat recovery.

This post was last edited by zgj2405 on 2011-4-5 at 13:35. I. Types: Upright: Thermosiphonic type, forced circulation type. Horizontal: Thermosiphonic type, forced circulation type, kettle-type reboiler, built-in reboiler. II. Control methods: One method involves using control valves to regulate the amount of steam entering the reboiler; a trap is installed at the condensate outlet； Another approach is to use a stop valve at the steam inlet, with the condensate outlet controlled by a control valve! The control valve is located at the front and is used to regulate the amount of steam; since the steam pressure fluctuates greatly, it is easy to adjust. The control valve is located at the back; it regulates the temperature by adjusting the heat exchange area inside the reboiler. This allows for fine-tuning, and the control is more stable compared to when it is done at the front

Types of reboilers: Vertical, thermosiphonic, forced-circulation; Horizontal, thermosiphonic, forced-circulation. Pot-type reboilers, built-in reboilers. Control methods: 1) Adjusting steam flow – this is the most direct method of control, as it allows for regulation of the heat input and thus the amount of evaporation. 2) Adjusting the amount of steam condensate: To prevent backflow of steam condensate and loss of effective heat exchange area in the boiler, the amount of steam condensate is adjusted. When the height of the steam condensate exceeds the designed range, more steam condensate is discharged; the increased steam heating area boosts the evaporation rate. This type of regulation is commonly used in boilers with low heat loads and low evaporation rates

Format: Vertical and horizontal; heat siphon type, forced circulation. Control method: The most direct way of regulation, by controlling the heat added (via a conversion gas or steam reboiler) to control the amount of evaporation.

The reboiler shows that a vertical configuration provides better heat exchange effects than a horizontal one. It is advantageous to use condensate instead of the incoming hot medium in a reboiler. Generally, reboilers are equipped with level gauges; just ensure proper control, and there will be no issues

Our company uses a thermosyphon reboiler; the amount of conversion gas entering the reboiler is controlled through the control valves on the main and auxiliary lines, thereby regulating the temperature at the bottom of the tower. This approach also helps to cool the conversion gas. It is important to monitor the changes in the temperature and pressure of the conversion gas, as these parameters are easy to adjust. Pay attention to the pressure of the converted gas during startup and shutdown to prevent damage to the reboiler

The thermosyphonic reboilers used for distillation in our company work fairly well; steam and condensate flow are regulated using control valves. For purification purposes, control valves are used to adjust the steam volume, and there are significant fluctuations in this flow. This is closely related to the stability of the company’s steam distribution network. Relatively speaking, regulating the condensate flow is more stable, but still, manual operation by our staff is required – either there are problems with the flow meters or with the valves. Thank you all for your hard work

What happens to the water output when a steam trap is used for condensate?

Ensure proper temperature rise, reduce steam waste, and avoid water hammer. . Heat recovery from hot water reuse?