Determination of coking rate in coking process

I heard that the rate of coke formation in the coke tower is not the actual real-time rate; rather, it is a calculated value based on the distance between the first two neutron level detectors. The rate is adjusted each time a neutron level detector is reached. I’m not entirely sure about this – I hope someone with more knowledge can clarify it for me

It is calculated based on the different times it takes for the foam layer and the coke to reach the neutron level gauge, as the neutron level gauge cannot measure velocity.

By continuously measuring the H and C density of the material in specific areas of the coke tower, the neutron level gauge determines the dynamic distribution pattern of all types of material present in the tower (oil-gas, foam, coke, or water). With the help of the signal indicating when oil injection begins at the bottom of the tower, it provides real-time readings of the rising height of the foam layer and the coke layer

The neutron level gauge determines the dynamic distribution of the material state within the tower – whether it is oil and gas, foam, coke, or water – by continuously measuring the H and C densities of the material in specific areas of the coke tower. With the help of the signal indicating when oil injection starts at the bottom of the tower, it provides real-time readings of the heights of the foam layer and the coke layer. The value obtained in this way should represent the height of the coke layer. On everyone’s DCS screens, there should also be a display showing the rate of coke formation (the instantaneous value of the coke layer height). For example, if the heights of the coke layer and the foam layer have not yet reached the second level threshold, the neutron level gauge cannot determine the amount of feed being supplied at that time. So how is this value for the coke layer height determined? In other words, if the feed rate is increased at that moment, wouldn’t the rate of coke formation also increase?