PETROLEUM REFINERY ENGINEERING (CLL 794) DEPARTMENT OF CHEMICAL ENGINEERING, IITD
TUTORIAL SHEET - 8
HYDROCONVERSION
1. Find the catalyst volume needed for the desulphurization of VGO. The initial sulphur content is 2.3 wt% and the final sulphur content of the product is 0.1 wt%. The reaction rate constant (h-1) can be expressed as :
k = 2.47 x 1010 exp(-14,995/T)
The reaction conditions are T = 415 deg. C and P = 5.1 MPa. The order of the reaction was found to be n = 1.7. The feed flow rate is 167,500 kg/h and has a density of 910 kg/m3.
2. It is required to hydrotreat naphtha which has 1 wt% S and API = 50 . Find:
a) How much hydrogen is required to remove all the sulphur in the feed by empirical correlations.
b) How much of this hydrogen is used for chemical requirements.
c) If the mean average boiling point of this naphtha is 135 deg.F. Assuming that the naphthene and aromatic present in the naphtha are cyclohexane and benzene, respectively. Find the volume of hydrogen (SCFB) to convert all cyclohexane and benzene into hexane.
3. It is required to remove all S in a feed of atmospheric gas oil (AGO) by hydrotreating. The feed contains 2 wt% S and sulphur compounds distributed is as follows:
Compound / RSH / R2S / (RS)2 / Thiophene (C4H4S)Wt% / 45 / 25 / 20 / 10
The AGO has an API = 30. Calculate the chemical hydrogen requirement in SCFB.
4. Gas oil has an API of 30, and a sulphur content of 1.5 wt% is fed into a hydrotreater. It is required to carry out HDS at a severity of 90%. Calculate the hydrogen required and product API.
5. A heavy residue stream that contains mostly n-C30 (990 lb mol/h) and some amount of thiophene (10 lb mol/h) is prepared to enter an ARDS process to crack the heavy component n-C30 to more lighter components such as n-C20, n-C10 and n-C4. In addition, thiophenes should be completely removed. The feed stream is initially at 100 deg.F and 120 psia. This feed needs to be mixed with hydrogen stream (1250 lbmol/h) available at 150 deg.F and 200 psia. The mixed feed should be heated and compressed to 700 deg.F and 1500 psia before entering the reactor. The reactions are shown below:
1. C4H4S + 4H2àC4H10 +H2S Conversion100% (Conversion reactor type)
2. C30H62 +H2àC20H42 + C10H22 Conversion 70% (Conversion reactor type)
The reactor products are cooled to 200 deg.F before entering a gas-liquid separator, 300 lb mol/h of the hydrogen coming from this separator is recycled back with the feed. The rest is vented to the atmosphere. The liquid stream coming out from the separator is then expanded by a valve to reduce the pressure to 250 psia. This makes it ready to enter a distillation column in order to separate the extra hydrogen left with the hydrocarbons. A typical flowsheet of the ARDS process is shown below. Perform a material and energy balance for the ARDS process.