January 16, 2018 at 9:33 pm #28015
Does anyone have any system to measures the drained water after reactors cooling for safe unheading operation.
Does anyone have any kind flowmeter in drain line to measure the drain water?
January 17, 2018 at 3:44 pm #28029
I have not heard of any flow meters in the drain line. This would be a difficult service to measure as coke fines could plug off any impulse lines and any restriction to provide pressure drop could cause the drain line to plug, which is a serious safety hazard.
I have seen neutron backscatter detectors mounted on the coke drum just above the cone. This device can discriminate between coke and water. It can be used to show water drained down to that point in the coke drum. I am also aware of sites that will put water back into the drum for a few minutes and then watch it drain out to prove that the drain line is not plugged.
What problem are you trying to solve? The use of slide valve technology, either DeltaValve or IMI Z&J, for the bottom and top unheading devices reduces the hazards associated with hot water draining out of a coke drum. These devices allow the operators to open the drum from a remote location and drain through the valve if the drain line is plugged. An appropriate exclusion zone should be set up before attempting to drain a coke drum through the bottom slide valve.
January 17, 2018 at 9:39 pm #28031
We are having an old Hahn & Clay system in which un-heading operation is very risky due to the residual water in the reactor like old manual system. So to ensure that all the residual water got drained from the reactor i was thinking of putting a ultra sonic flow meter (clamp on) in the drain line. Is it feasible?
January 19, 2018 at 1:26 am #28034
I think an ultrasonic flow meter is the only type that has a chance of working. I do think it will be a very challenging application and is more likely to generate erratic output. The drain line would have to have a seal loop in it to keep the section of line full of liquid or you will get a reflection off of the surface. With a liquid seal, the likelihood of the drain line plugging will be much greater. Keeping the drain line full of water will cause accelerated corrosion at the air-water interface. I think the probability of an ultrasonic flow meter working as you are hoping is very low.
If you are having trouble draining water out of the drum, try increasing the heater outlet temperature 1 or 2 degrees C during the coking phase to increase conversion.
January 19, 2018 at 9:47 pm #28040
Actually we facing problem due of improper draining of water after reactor cooling due to shot coke production. Shot coke holds the water inside the bed and in time of unheading sometimes gust water along with coke came out suddenly.
January 22, 2018 at 12:01 am #28041
It is common to have difficulty draining water out of a coke drum if there is unconverted oil in the drum. Raising the drum temperatures during the coking phase will help finish the conversion of hydrocarbons in the drum to coke and lighter hydrocarbons.
The initial steaming of the drum to the fractionator is also important. This phase of steaming is used to push the feed up through the coke bed up to the liquid layer at the top of the coke bed so that no partially converted feed is contained within the coke bed. This steaming is also used to transfer heat from the coke bed to the reaction mass that is still converting and still needs energy. Too much steam at this step will slow the reactions and allow pitch or tar to run back down into the coke bed. Not enough steam will fail to push all the feed out of the coke bed and into the liquid reaction layer.
If the initial steaming is not done properly, when the coke bed is steamed to the blow down system much of the partially converted feed can be stripped out of the drum if the steam rate is high enough for long enough. As much steam as possible should be used in the phase of the off-line cycle without causing carry over of coke fines into the blow down system. So, higher drum temperatures while coking, adequate steaming to the fractionator and to the blow down system should help with draining water out of the coke drum once the coke bed has been quenched.
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