When the atmospheric and vacuum distillation unit is operating at reduced capacity, is steam injected into the furnace tubes?
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In a atmospheric and vacuum distillation unit, is steam injected into the heater tubes when it is operating at a reduced capacity? At what level below the processing load does steam injection begin? Is it related to the size of the device? Is it related to the outlet temperature of the heating furnace? The two small units I’ve seen did not adopt steam injection measures even when the load was at 70%. What are the harms?
When the processing volume is low, the combustion flow rate of the burner can be reduced
In a vacuum distillation unit, when it is operating at reduced capacity, steam cannot be supplied to the heating furnace tubes; the focus is on keeping the outlet temperature of the heating furnace within acceptable limits, by reducing the intensity of the fire, and shutting down several burners if necessary. If the temperature at the outlet of the heating furnace exceeds the limit, coking may occur; in such cases, an appropriate amount of steam can be injected.
Atmospheric pressure furnaces do not require steam injection. In reduced-pressure furnaces, when the processing volume is low, the flow rate inside the furnace tubes decreases, which makes it necessary to inject steam appropriately in order to increase the flow rate of the medium within the pipes; it is only important to control the amount of steam injected.
It has never been injected, nor is there a steam injection process. The minimum processing volume is around 50%; strict control is exercised over the flow rate at the furnace branches, as well as over the flame shape and furnace temperature. It’s not a big problem
The appropriate internal flow rate for atmospheric and vacuum heating furnaces is 980–1500 kg/m2•s. The processing capacity at the minimum flow rate can be calculated based on the diameter of the furnace tubes. Atmospheric furnaces do not require gas injection, but vacuum furnaces need gas injection when the flow rate is low, in order to increase the flow rate and prevent coking of the furnace tubes.
Without steam injection, coking at the bottom of the furnace tubes is not yet very severe
I would like to ask: regarding an internal flow velocity of 980–1500 kg/m2•s in this pipe, are there any standards or design manuals that address this?
There is no need to inject steam into the regular furnace; for the furnace in reduced operation mode, steam injection can be increased slightly to raise the flow rate and prevent coking
There is no need to inject steam into the regular furnace, as the processing volume is high; it should be fine. Accordingly, the two steam injection lines of the reduced-capacity furnace can be slightly opened to increase the flow rate and prevent coking；