Crude charge

The asphaltic residuum from atmospheric distillation amounts to roughly one-third (U.S. average) of the crude charged. This material is sent to vacuum stills, which recover additional heavy gas oil and deasphalting feedstock from the bottoms residue. 

The control scheme shown in Fig. 17.4 is certainly quite common. But is it the best Figure 17.5 is a copy of the crude charge system in a now-defunct refinery in Port Arthur, Texas. I saw it in operation many years ago. It worked fine. The required flow of crude directly controls the governor. The turbine speed is then always at its optimum. The AP across the process-control valve is always zero, because there is no process-control valve. This design is a direct descendant of the original method of controlling the steam flow to pumps. The steam inlet valve was opened by the operator, so that the desired discharge flow was produced. 

To improve the yield, we can increase the initial crude charge to 117 gm of crude per liter of solvent so that it has approximate 100 gm of desired compound. The yield of this approach will increase to its maximum yield as... 

First comes the question of the crude charge distribution within the molecule, which largely determines the nature of its interaction with radiation. Then there comes the quantum theory of molecular emission and absorption, and finally the electromagnetic theory of radiation itself. 

A sudden drop in furnace feed temperature is commonly caused by a slug of bottoms sediment and water (BSJ crude supply system has been cleaned. The silt and waxy dirt were flushed down the crude line to the refinery. A floating suction in the refinery s crude charge tank minimizes the effects of these incidents. 

If a reasonable overall comparison of pounds of feeds and products ( 5%) cannot be calculated, the validity of the test is compromised. A table showing a component balance should be made. Present these data in mol/hr and B/D. For example, on an alkylation unit it is important to determine if the moles of isobutane consumed equal the moles of alkylate produced. On a crude unit one might hope that all the barrels of pentane in the crude charge can be accounted for in the products. A sample component material balance is shown in Table 27-1. 

Increased vaporization of the lighter crude through the preheat exchanger train and furnace increases pressure drop, which reduces the capacity of the crude charge pump. 

The control scheme shown in Fig. 24.4 is certainly quite common. But is it the best Figure 24.5 is a copy of the crude charge system in a now-defunct refinery in Port Arthur, Texas. 1 saw it in operation many years ago. It worked fine. The required flow of crude directly controls the governor. 

Since the reduced crude charge to a vacuum tower has already been partially processed in the atmospheric tower, some basic information about the whole crude and its fractions has been developed and should be available at this point. However, it is necessary to develop feed flash data from the reduced crude apart from that previously calculated during the design of the atmospheric section. 

This is illustrated by operation of the desalter, which is usually the first processing unit in the refinery proper. Its function is to reduce the content of bottom sediment and water (BS W) from the crude charge to the crude still. Water (generally brine) causes corrosion in units down-stream of the desalter as a result of decomposition of chlorides to hydrochloric acid at the elevated processing temperatures. Addition of alkali to the desalter reduces hydrolysis of calcium and magnesium chlorides and consequently results in less hydrochloric acid being formed in the crude still overheads, etc. 

I last saw this problem at a 100,000 BSD flashed crude charge pump in Corpus Christi, Texas. It looked like the pump was cavitating. The pump discharge pressure was erratically low. The flow was also swinging. The control valve position was erratic. I checked the motor driver amps, which were also erratic. All observations indicated cavitation. 

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