Naphtha Hydrotreater (NHT)

Naphtha hydro-treating technology is designed for upgrading a blend of straight run naphtha from CDU/VDU and visbreaker naphtha from VIS, as well as stabilization of hydro-treated wild naphtha from DHT. This unit consists of the following sections: 

  • Reaction section
  • Naphtha stabilization section
  • Naphtha splitting section 

The purpose of this process is to produce treated naphtha with a maximum 1 wt. ppm content of organic sulfur component and denitrification to maximum 0.5 wt. ppm to feed the reforming unit or other downstream unit. 

In this process naphtha is routed to reaction section from CDU and VIS. Hydro-refining and hydrogenation reactions take place in this section. Un-stabilized naphtha from reaction section is mixed with wild naphtha. To increase LPG recovery from stabilization section, off gas from stabilization section is mixed with the latter and send to re-contactor drum. Treated naphtha is sent to splitter section. Treated light naphtha is routed to gasoline pool and treated heavy naphtha is sent to NCR. NHT needs hydrogen to start while NCR needs treated heavy naphtha.

Feed to the naphtha hydro-treating unit consists of: 

  • 16,240 BPSD straight run naphtha from CDU or storage tank
  • 907 / 1,099 (SOR/EOR) BPSD hydro-treated wild naphtha from DHT
  • 757 BPSD visbreaker naphtha from VIS

Naphtha Catalytic Reformer (NCR)

NCR is considered to treat heavy naphtha stream from NHT. This unit contains reactor section (include 3 reactors in series) and fractionation section (naphtha stabilizer or debutanizer) which gasoline with high octane number is produced. Produced hydrogen in this unit is used in NHT, DHT and SRU.

Heavy hydro-treated naphtha stream to the NCR consist 10,532 / 10,699 (SOR/EOR) BPSD which comes from heavy NHT.

Treated heavy naphtha from NHT is mixed with H2 rich gas stream and routed to reaction section. Reactor effluent is sent to product separation section, in which effluent is cooled and un-stabilized reformate is separated from H2 rich gas. A stream of H2 rich gas is mixed with feed and the remained is mixed with un-stabilized reformates in order to increase H2 purity of H2 rich gas which is separated from un-stabilized reformates in re-contacting. H2 rich gas from re-contacting drum is routed to NHT, DHT and SRU.

Un-stabilized reformate is sent to stabilization section, in which un-stabilized LPG is separated from reformate and off gas from stabilization section is sent to fuel gas header.

 Regarding the effect that pressure decreasing, increases reformate yield and RON, the reaction section of NCR operates at low pressure in comparison to similar units. However, pressure reduction increases coke deposition on catalyst and it is compensated with increasing H2/HC ratio.

Diesel Hydrotreater (DHT)

Duty of the DHT is to upgrade a blend of straight-run kerosene, straight-run gasoil, light vacuum gasoil and visbreaker gasoil into kerosene and diesel products having sulfur content less than 10 ppm. The unit will be installed to remove sulfur (all type of sulfur) from straight run gas oil and gas oil of visbreaker at existence of hydrogen with hydrocracking reaction.

DHT is designed to process the streams presented the following table: 





21,310 / 21,310


Visbreaker Gasoil




2,800/2,800 kg/hr.



88/260 kg/hr.


 The main objectives of the unit are the followings: 

  • Maximize the diesel production with a sulfur content <10 ppm wt.
  • Minimize the kerosene production
  • Minimize the production of naphtha and light-ends

 The main products of the unit are the followings: 

  • The light-ends produced in the diesel hydrotreater will be amine washed inside the DHT battery limit. The extra sweet light-ends (fuel gas) will be sent to the fuel gas header and much of them will circulate as H2 recycle gas in DHT
  • The naphtha produced in the diesel hydrotreater will be sent to the NHT to increase the RON of its heavy portion through NCR
  • The kerosene will be sent to storage
  • The diesel will be sent to the diesel pool
  • Diesel and/or kerosene could be sent to fuel oil for matching the sulfur content

 The hydrogen to the DHT is supplied continuously from the two following sources: 

  • Naphtha catalytic reformer
  • H2 production package


Sulfur Recovery (SRU)

SRU in Alfruqlus refinery is designed to recover sulfur from acid/sour gases from Amine regeneration & Sour Water Stripper Units.

The feed to the sulfur recovery unit is as below: - Acid gas from ARU with flow rate 2.58 Ton/hr. (1,774 Nm3/h at temperature 60oC and pressure 0.95 barg) - Sour gas from SWS with flow rate 0.36 Ton/hr. (351 Nm3/h at temperature 82oC and pressure 0.85 barg).

SRU consists of the below sections: - Clau Feasibility s section (1 train) - Tail Gas Treatment (TGT) section - Sulfur product degassing and storage tank section - Incineration section SRU consists of one Claus trainand one TGT section. The design capacity shall be 58 T/D. The feedstock of the Claus train consists of acid gas from ARU and sour gas from SWS. The Claus section consists of a thermal stage, in which H 2S is partially burnt with air, followed by two conventional Claus reactors; the liquid sulfur produced is treated in the liquid sulfur degassing section for the removal of polysulfides and H 2S. The tail gas coming from Claus section is sent to the TGT section, where all components containing sulfur are reduced or hydrolyzed to H 2S. Removal of H2S contained in the tail gas is achieved by an MDEA solution in the TGT absorber; the rich amine will be sent to ARU for regeneration. Sweet off-gas from TGT absorber is sent to a thermal incinerator to convert the residual sulfur compounds of sweet Tail Gas to SO2 before released to the atmosphere via a stack.

Bitumen Blowing (BBU)

Scope of the BBU is to harden part of the VR coming from the CDU/VDU, modifying its penetration and softening point in order to make it suitable to be sold as road bitumen. The BBU will be designed to process 1,636 T/D of VR in 2 parallel bitumen blowing reactors. The basis of bitumen blowing process is the oxidation of VR with air. The process involves passing compressed air through the feedstock in a reactor at elevated temperatures to change physical properties of the feed to produce different grades of bitumen. This objective will be achieved through complex reactions including dehydrogenation of the feed resulting in oxidation and poly-condensation reactions. The reaction, increase the molecular weight of asphaltenes already present in the process feed, and forming additional asphaltenes from maltenes phase. Therefore, the blowing process alters the chemistry and balance of feed components to desired bitumen characteristics. Bitumen blowing process scheme consists of the followings sections:

- Reaction section with air blowing

- Off gas scrubbing

- Incinerator

Visbreaker (VIS)

he Visbreaker (VIS) unit objective is to process a part of the vacuum residue from the Crude -Vacuum Distillation unit with the following purposes:

- Maximize the production of distillates, in particular VIS Gasoil.

- Minimize the production of Fuel oil. The main products of the unit are as follows: 

  • Sweet gas: The sour gas produced in the VIS unit will be mixed by sour gases from LRU (unit 115), NHT (unit 112) and DHT (unit 116) units, and after treating with Amine solution inside the VIS unit battery limit, produced sweet gas will be sent to fuel gas system.
  • VIS Naphtha: Unstabilized Naphtha which is produced in VIS unit will be directly sent to the NHT unit or to storage in case of the NHT unit is not in operation.
  • VIS Gasoil: The produced VIS Gasoil from VIS unit will be normally sent to DHT unit or to storage when the DHT unit is not operating. VIS gasoil may be used for fuel oil production after treating in DHT unit.  VIS Tar: Residue of VIS unit as a main product of VIS unit will be sent to Fuel oil blending system.