Hydrodesulfurization reactor

Flow diagram of the process for hydrogen and distillate fuel production from residual oil using iron oxides and steam. 1 = Cracking reactor, 2 = distillation column, 3 = hydrogen generator, and 4 = hydrodesulfurization reactor. 

The temperature in the hydrodesulfurization reactor is often considered to be the primary means by which the process is controlled. For example, at stabilized... 

In the same manner as in hydrocracking (Dolbear, 1997), hydrogen is added at intermediate points in hydrodesulfurization reactors. This is important for control of reactor temperatures. The mechanical devices in the reactor, called reactor internals, which accomplish this step are very important to successful processes. If redistribution is not efficient, some areas of the catalyst bed will have more contact with the feedstock. This can lead to three levels of problems ... 

This difficulty arises because the size and operating conditions of a large-scale reactor normally differ significantly from that of a pilot-scale column. Commercial hydrodesulfurization reactors are of size up to 20 by 30 ft. and may be operated at up to 70 atmospheres and 400°C. In contrast, pilot-scale hydrodynamic data are obtained from columns of a few inches, or less, in diameter and several feet in height, at near atmospheric pressure and room temperature. 

The dynamic liquid holdup haL can be obtained from the mean residence time, liquid flow QL, and the reactor volume V as haL = tmQ JV. This approach for correlating the performances of pilot-scale hydrodesulfurization reactors was evaluated by Murphree et al.,31 Cecil et al.,s and Ross.40 It should be noted that the efficiency 0 is very sensitive to the percentage conversion at high conversion levels, where a small change in 0 can significantly change the level of conversion. 

Dynamics of Commercial Adiabatic Reactors with an Aging Catalyst (Commercial Hydrodesulfurization Reactor with Quench Fluids )... 

Ross73 points out that at the same temperature and pressure a commercial hydrodesulfurization reactor gives poorer performance (i.e., less conversion of... 

The temperature in the hydrodesulfurization reactor is often considered to be the primary means by which the process is controlled. For example, at stabilized reactor conditions, a rise of 10°C (18°F) in the reaction temperature will substantially increase, and may even double, the reaction rate. Generally, an increase in the temperature (from 360°C to 380°C, i.e., from 680°F to 715°F) will increase the conversion slightly or for a fixed conversion of about 90% enable the quantity of catalyst necessary for the process to be halved. 

Figure 14. The Intensity Function for the Nonvolatile Tracer in Hydrodesulfurization Reactors A and B.

In case plugging and/pr fouling is a problem, trickle flow clearly has a disadvantage over slurry reactors. A well known phenomenon is the pressure drop built-up during operation of a trickle flow hydrodesulfurization reactor limiting the operating period. Similar problems do not occur in slurry reactors. 

Shah, Y.T., Mhaskar, R.D., Paraskos, J.A. 1976. Optimum quench location for a hydrodesulfurization reactor with time varying catalyst activity. Ind. Eng. Chem. Process Des. Dev. 15(3) 400-406. 

---