What are the characteristics of DCS operation for distillation column heat sources heated by heat transfer oil and steam?
Thread Content
In chemical production, the reboiler of distillation towers is generally heated using heat transfer oil or steam. What are the characteristics of its operation?
Heat transfer oil provides relatively more stable heating, but it is energy-intensive. Steam, as a heat source, sees temperature fluctuations due to weather conditions, especially during rainy or snowy weather. In the two distillation units I’ve worked with before, both heat transfer oil and steam were used; yet heat transfer oil offered more stable heating in terms of reboiler performance. Nevertheless, it’s important to conduct regular inspections outdoors to prevent leaks, as exposure to the outside environment can have effects on heat transfer oil (depending on its composition)
There is no difference in DCS operation; it simply involves controlling the flow rate of steam or heat transfer oil based on the temperature inside the tower or the liquid level at the bottom of the tower. As a heat source, steam should be used whenever possible. I’d like to hear from other sailors when it’s appropriate to use heat transfer oil as a heat source for distillation towers
The characteristic of heat transfer oil is its high temperature, but such high temperatures are not required for ordinary distillation. In terms of heat enthalpy, steam is higher! It is easier to meet the requirements for heat transfer with a small temperature difference.
I think heat transfer oil is more stable and less affected by external factors, whereas heating with steam is unstable and highly susceptible to external influences.
As you said, heating with heat transfer oil provides greater stability, as well as more stable control of each tower. Steam offers relatively poorer stability; the choice of heat source is likely determined by the properties of the materials in each tower and the required level of operational precision.
The convenience of using heat transfer oil is evident for us; in winter, when the room temperature drops to between -20 and -30°C, we only need to operate the reboiler valve to shut down the system. With steam, however, it’s necessary to purge the system after shutdown, and the endpoints are prone to freezing； Heat transfer oil causes less corrosion to equipment compared to steam ； The cost of heat transfer oil is higher than that of steam (including the boiler) ； It has a higher fire hazard than steam
Heat transfer oil offers relatively stable control, but it is expensive. The steam is not very stable, but the price is relatively low. It mainly depends on the requirements and stability of your process temperature
On the DCS, it seems there’s no difference on the surface, but in reality, heating with heat transfer oil is much more stable than heating with steam