Crude and Vacuum Distillation (CDU/VDU)

CDU/VDU will process crude from storage and will provide feeds to the following units, accordingly to the block flow scheme: 

  • Full range naphtha as feed to the NHT
  • Kerosene as feed to DHT
  • Light atmospheric gas oil as feed to DHT
  • Heavy atmospheric gas oil as feed to DHT
  • Light vacuum gas oil as feed to DHT or as fuel oil cutter
  • Medium vacuum gas oil as fuel oil cutter
  • Heavy vacuum gas oil fuel oil cutter
  • Vacuum residue as feed to VIS
  • Vacuum residue as feed to bitumen production
  • Vacuum residue as fuel oil 

Crude from storage will be preheated in 4 stages and (including heat exchanger, de-salters and pre-flash drum) will pass through a fired heater to gain necessary heat for product separation in the atmospheric column. The primary objective of the ADU is to separate the crude boiling range cuts to meet the desired product specification. 

The full range of naphtha will be sent to NHT, the kerosene and atmospheric gas oil will be combined to feed the DHT, and the long residue will be fed to the VDU.

The aim of the VDU section is to fractionate the atmospheric residue under vacuum condition to produce vacuum gasoil and VR that will be processed in the downstream units. The column separates the long residual into light, medium and heavy vacuum gas oil and VR. 

The light vacuum gas oil will be fed to the DHT; VGO will be fed to storage to use as fuel oil.  VR will be fed to the BBU for the production of paving bitumen. However, a portion of VR will be fed to VIS. The BBU has been included in the refinery configuration since bitumen production for road construction. In addition, producing bitumen is more desirable if a permanent shutdown of the Homs refinery, currently the major bitumen supply source for this area of the country, is expected to occur shortly after the startup of the refinery.

Amine Regeneration Unit (ARU)

It's one of Auxiliary Units, ARU is designed for regenerating rich amine solution streams from DHT, VIS, SRU and CDU units. The regenerated amine solution is sent back to amine users. 

The purpose of this process is to regenerate mixed rich amine solution to lean amine solution with amine loading spec of 0.01 maximum. The ARU consists of following sections:  

  • Amine regenerator and circulation system: Include one regenerator column, which rich amine stripping takes place by indirect steam (re-boiling) and the produced lean amine solution will be circulated in the DHT, VIS, SRU and CDU units
  • Amine make-up / drain system
  • Lean amine filters

Sour Water Stripper Unit (SWS)

It's one of Auxiliary Units, SWS objective is to remove hydrogen sulfide and ammonia of the generated sour water in some process units CDU/VDU, NHT, DHT, SRU, and VIS. 

The inlet sour water streams from ORBL to this unit is at 2 barg. The capacity of SWS unit for design case is 62 Ton/hr. 

This unit is consisting of the following sections: 

  • Sour water surge drum
  • Sour water stripping
  • Stripped water cooling
  • Effluent neutralization
  • Washing out system


Light Ends Recovery Unit (LRU)

It's one of Auxiliary Units, LRU objective is processing two LPG feed streams which are un-stabilized LPG from NCR unit and un-stabilized sour LPG from NHT to produce liquid propane and butane as LPG components to be mixed in storage area as per market requirement. Un-stabilized LPG is already hydro-treated in naphtha block section, and there is no mercaptan among feedstock; hence no LPG treatment is required in refinery process scheme. H2S content with light components (methane and ethane) is separated from LPG feed in de-ethanizer overhead by optimizing number of trays and feed entering tray. 

 LPG unit comprising of two main sections: 

  • de-ethanizer section which separates light components like methane and ethane as well as hydrogen sulfides from LPG bottom product and produce sour off gas from de-ethanizer OVHD section
  • de-propanizer section which separates propane and butane streams coming from de- ethanizer bottom 

The capacity and source of LPG streams as LRU feed, is shown in the following table: 


Volume Flow (m3/hr.)

Mass Flow (kg/hr.)





Un-stabilized LPG feed from NCR





Un-stabilized Sour LPG feed from NHT





 The main products of the unit are as follows: 

  • Sour off gas: the sour off gas is produced in LRU will be sent to VIS for amine treating
  • Liquid propane: produced liquid propane in LRU will be sent to propane storage
  • Liquid butane: produced liquid butane in LRU will be sent to butane storage


Fuel Gas System (FUS)

It's one of Auxiliary Units, FUS gathers the off gas/sweet gas from different sources of the process facilities and supplies fuel gas for the requirement of various users in the refinery. FUS comprises the following subsystems: 

  • Natural gas section
  • Refinery fuel gas section (fuel gas mixing drum)
  • LPG vaporizer
  • LPG super-heater
  • Fuel gas distribution network 

Main natural gas pipeline from national grid will be routed to fuel gas system to provide directly the fuel demands for PGU, hydrogen production unit, start-up and shut down of SRU. Natural gas also will be the main source of fuel during plant initial start-up while no refinery off gas is available. 

The refinery fuel gas from various processing units are mixed in the fuel gas mixing drum and then distributed to the users through the distribution network. In the event of fuel gas header low pressure, natural gas from the header will be supplied to fuel gas system. If natural gas fails to adjust the desired pressure, then LPG will be used as back up for the fuel gas to supplement the make-up gas. LPG vaporizer is provided to evaporate liquid LPG which will be supplied from LPG product storage. LPG vaporizer evaporates liquid LPG to serve as fuel gas back up. 

The produced fuel gas from FUS will be distributed via interconnecting pipelines to supply required gaseous fuel to the consumers. The major fuel gas consumers of fuel gas in the refinery are: 

  • Gas turbines in power generation unit (GTG's)
  • Process fired heaters
  • Steam generation boilers
  • Blanketing (gaseous fuel only)

Caustic Dilution Unit

The objective of this unit is to supply caustic solutions for process and utility units. Caustic solution for the refinery is required for the following basis: 

Continuous basis: 

  • For DWS plant and WWT
  • For CDU 

Intermittent basis in regeneration: 

  • For NHT
  • For DHT
  • For NCR
  • For SRU 

The facility shall be designed to produce caustic solutions for process and utility unit’s requirements by receiving caustic liquor (lye) having 40% wt. concentration of caustic. The caustic dissolving facilities shall also be designed for dissolving caustic soda received in the form of flakes. The system shall comprise of following: 

  • Caustic dissolving facility for dissolving flakes to 40% wt. caustic solution
  • Storage facility for 40%wt, 10%wt and 5%wt caustic solutions
  • Pumping facilities for caustic transfer to various process and utility users

Raw and Service Water (RWS)

RWS consists of desalination section and service water storage and distribution. 

Desalinated water is designed to meet the requirements for feeding the users listed below: 

  • Caustic dilution unit
  • Demineralized water system
  • Potable water system
  • Cooling water system 

Service water is distributed and used mainly for cleaning and washing services, usually by hoses at the utility stations located throughout the plant, but also for keeping the desired water level on the hydraulic seals, on a continuous basis, where required. 

The source for the preparation of desalinated and service water is raw water from battery limit. Because raw water is pre-treated water, it will be considered as service water without any treatment. Desalinated water will be produced by RO package to reach the desired specification. 

RWS will include: 

  • Reverse osmosis desalination systems
  • Desalinated water storage and pumping
  • pre-treated raw water storage pool
  • pre-treated raw water chemical injection packages
  • Service water pumps
  • pre-treated raw water pumps

Potable Water (PWS)

Desalinated water is used as the feed for the PWS. The desalinated water is treated to potable standards in potable water package system. The desalinated water must be re-mineralized by the injection of calcium chloride (CaCl2) sodium chloride (NaCl), sodium carbonate (Na2CO3) and sodium hypochlorite (NaClO) to reach the appropriate standards for human consumption.

The potable water unit is shown as a package. Desalinated water is used for dilution of chemicals. The scope of this system mainly includes the following subsystem: 

  • Chemical injection packages
  • Potable water storage and transferring pumping
  • Activated carbon filter 

The details of unit capacity for potable water unit will be as follows: 

Based on 1200 people with an individual consumption of 250 lit/day, the total hourly mean consumption would be 12.5 m3/h rounded to 15 m3/h, to account for necessary additional uses. 

The normal consumption of potable water is then estimated to be 15 m3/h. For PWS, 2 times of the normal flow rate is considered for design flow rate.

Demineralized Water (DWS)

DW for the complex is required as make-up water for SGS and PDU and as such will be produced with BFW quality, so to be fed to the complex boilers after deaeration in BFW; demineralized water is also required as process water for additional uses as dilution, injection and washing. 

Demineralized water system comprising of DWS (mixed bed type), storage and pumping facilities will be provided to meet the total demand for the complex. Desalinated water from the desalination plant will be used as the feed for the DWS. 

DWS shall consist of mixed bed polishing columns, cationic and anionic resins loading and unloading facilities, and the required auxiliary equipment such as chemicals dosage & blower stations for the regeneration and for the effluent water neutralization. 

For this duty it is proposed to install nos. (2) columns of ion exchanging mixed Beds, with associated facilities, (1 line will be operating + (1) line in regeneration/standby), to be supplied as package unit. Demineralized water package vendor shall confirm the proposed configuration (number of mixed bed ion exchangers). 

Each line will be sized for a net capacity of 116 m3/hr., corresponding to a DWS net total outflow of 2800 m3/day of demineralized water. 

Hydraulic sizing and provision shall be kept to operate all of the (2) chains at the same time, in case this need may arise. 

The system (nos. 2 MB’s in operation) will be able to be operated continuously with net output of 232 m3/h.

Boiler Feed Water (BFW)

BFW for the complex mostly is required for generation of steam in SGS and steam generation for heat recovery purpose in BBU, DHT, NCR, VIS and SRU. Also BFW is needed to de-superheat steam lines inside process units. BFW system shall consist of:

  • Deaerator is fed with polished condensate from condensate treatment unit and LP steam from distribution header; demineralized water is fed as make-up
  • Chemical injection packages (oxygen scavenger and corrosion inhibitor)
  • Steam turbine driven BFW pumps are normally in operation; electric motor driven pumps are provided as spare during steam turbine driver in maintenance

There are two levels of boiler feed waters in the total plant: 

  • HP at 67 barg and 125 °C. This level is mainly used for HP steam generation in the boilers and it is also used for de-superheating in the main high-to-MP let-down stations.
  • MP at 30 barg and 125 °C. This level is for LP steam generation in the boilers in process units and it is also used for de-superheating in the main high-to-low pressure let-down stations. 

Users of BFW are mainly the boilers inside SGS and PGU; Steam is also produced in some process units of the refinery, therefore requiring HP or MP BFW. Small amounts of MP and HP BFW are requested from refinery complex for steam de-superheating. For this duty it is proposed to install one deaerator. Deaerator will be sized for a net capacity of 247 m3/hr., corresponding to a BFW net total outflow of 5928 m3/day of BFW.

Cooling Water (CWS)

CWS is a closed circulation system used for cooling task in all refinery including process, utility, offsite and tank area. 

The CWS mainly consists of (not limited to): 

  • Multi cell cooling tower
  • Chemical dosing packages
  • Cooling water circulation pumps
  • Associated underground cooling water supply/ return lines
  • Side stream filters

All cooling water unit is included in package and consists of following sections. 

  • Cooling tower
  • Cooling water circulation pumps
  • Side stream filter
  • Chemical dosing package 

Maximum CW consumption of process units is 4,366.189 m3/hr. and maximum normal flow of CW for the refinery including 10% design margin is 5,368.868 m3/hr.

Steam Generation (SGS)

The function of SGS is to supply steam to all consumers within the plant. For this purpose, HP boilers are installed. HP boiler feed water for SGS comes from BFW. 

HP steam is generated via high pressure boilers according to 2+1 arrangement (two parallel boilers in operation plus one hot stand-by) with supply pressure and temperature of 45 barg and 400°C. Capacity of each boiler is 55 Ton/hr. 

There are three levels of steam in the plant for normal operation. Conditions at producer’s battery limits are as follows: 

  • HP at 45 barg and 400 °C
  • MP at 16 barg and 260 °C
  • LP at 5 barg and 180 °C 

HP steam is generated in boilers. In normal operation, HP steam is converted to MP level followed by de-superheating and then part of MP steam is converted to LP level in the second stage. The remaining HP and MP steams are directly sent to MP and HP steam headers.

Power Generation Unit (PGU)

The function of PGU is simultaneous production of electricity and recovering flue gas heat to produce HP steam by HRSG system. This unit supplies power to all consumers within the refinery. For this purpose, GTG are installed. Gas turbines are normally fed with natural gas, coming from FUS) In case of shortage/unavailability of natural gas, gas turbines are fed with a dedicated untreated and commercial diesel system consisting of tanks and pumping station. Moreover, two connections to national power grid are provided as backup. 

Overall power output of the PGU is the sum of several contributions: process users, non-process users, common facilities.

Nitrogen System (NUS)

NUS generates nitrogen from ambient air and supplies for the requirement of various users in the refinery. The nitrogen system comprises the following subsystems: 

  • Compression of feed air
  • Purification of feed air
  • Nitrogen production
  • Liquid nitrogen storage and vaporization 

The ambient air is filtrated by the air filter, then compressed to operating pressure by the air compressor. The compressed air is cooled by the refrigerator and sent to molecular sieve towers where carbon dioxide and moisture contained in the air are removed. The purified air is cooled down in the air exchanger to near its liquefaction temperature by heat exchange with outgoing product gas flowing in a counter- current to the incoming air. The cooled air is then sent to the lower part of a nitrogen rectification column, where the air is separated into pure gaseous nitrogen at the top and liquid rich in oxygen at the bottom. Pure produced gaseous nitrogen is delivered to the refinery network. A portion of gaseous nitrogen is liquefied in a nitrogen condenser located on the top of the nitrogen column by heat exchange with evaporating rich liquid and fall back to the nitrogen column as reflux. The liquid nitrogen is stored to the nitrogen storage tank and will be vaporized in the liquid nitrogen vaporizer by steam, according to the refinery demand. 

NUS capacity shall be 1,200 Nm3/hr., including 1000 Nm3/hr. of gas and 200 Nm3/hr. of liquid nitrogen equivalent simultaneously.

Plant and Instrument Air (PIA)

PIA generates compressed air and supplies for the requirement of various users in the refinery. This system comprises the following subsystems: 

  • Four main air compressors (2 running + 2 standby)
  • Four after coolers and wet air water separators (2 running + 2 standby)
  • Instrument air dryer with pre-filters and after-filters (2 × 100%)
  • Plant air dryer with pre-filters and after-filters (2 × 100%)
  • HP air compressors with after coolers (2 × 100%)
  • LP instrument air receiver (2 × 100%)
  • HP instrument air receiver (1 × 100%) 

Total air compressor capacity is 5,824 Nm3/hr., which demand of each instrument and plant air is presented in the following table: 

Air Demand



Total Instrument (dry basis)



Total Instrument (wet basis)


Total Plant (dry basis)


Total Plant (wet basis)


Waste Water Treatment (WWT)

Various liquid effluents, which require suitable treatment consist of two major categories, process unit effluents and sanitary effluents. 

Process Units Effluents: 

The facilities including different process units and utilities along with offsite facilities including storage tanks generate various liquid effluents, which require suitable treatment before its disposal. 

Sanitary Effluents: 

The process facilities outlined above will require operators, maintenance crews, office support stuff, laboratory facilities, and such personal which will generate sanitary effluents requiring treatment before disposal. 

After biological treatment of sanitary effluents, the treated effluent will be disposed to irrigation channel. 

A maximum population of approximately 1200 persons is considered for design estimations. 

The waste water treatment unit of the refinery is consisting of the following sewers: 

  • Oily water sewer (OSW)
  • Contaminated rain water sewer (CRW)
  • Spent caustic treatment (CAU)
  • Non oily water sewer (NSW)
  • Chemical treatment (CSW)
  • Sanitary treatment 

Main facilities for removal of oil, sulfides, phenols are Tilted Plate Interceptor (TPI) oil separator, Dissolved Air Floatation (DAF) unit, odorous control package along with equalization tanks. Grit is removed by centrifugal or gravity settlement.

Minimizing the production of sludge is done using Hydrogen Peroxide (H2O2) treatment facilities which remove sulfides and sulfites. 

Adjustment of PH is done using Sulfuric Acid (H2SO4) and caustic dosing systems. Biological treatment is done using two stage aerobic systems. Sand filters removes suspended solids remained after biological treatment. Bacteria carried over from the biological treatment will be killed by disinfection. 

Non-biodegradable COD is removed by granular activated carbon filtration. All sludge produced during treatment are thickened and dewatered for disposal. 

Condensate Gathering 

Steam is being used in the complex as process steam, motive fluid for steam turbine drivers, heating steam etc. Steam condensate will consequently result from the steam re-boilers, condensing steam drivers etc. Steam condensate from all units is collected into CRS and monitored for quality, before feeding to de-oiling system or dumping. 

Recovered condensate shall be treated at condensate gathering unit before being sent to de-aerators, at the BFW and boilers at SGS. For this purpose, three main headers are sent to condensate package LP, clean LP, HP and HP condensates. 

Considering that nearly no oil content is allowed for water feeding steam generation boilers, a de-oiling package must be provided to separate excess hydrocarbons. Inside the de-oiling package, a carbon active filter is provided. 

Condensates collected in storage tank (CST) is transferred to condensate polishing section consist of mixed bed for continuous treatment of the recovered condensate (due to possible contamination) in order to reach polished quality specification. Mixed bed will be regenerated by caustic and acid solutions. Regeneration of mixed bed could also be done by backwash with polished condensate. Produced saline water due to regeneration of mixed bed is sent to neutralize basin located in DWS. 

Produced polished condensate shall be stored at polished condensate storage tank (PCST) and sent to de-aerators located in BFW. 

As a preliminary attempt for calculating condensate unit capacity, it is assumed to have a capacity of 125 T/hr. which will be finalized later. Based on 8 hours of condensate collection, condensate storage tank in the package must have a working capacity of 1000 m3.

Fire Water Systems (FWS)

FWS as the primary means of fire extinguishing and fire control shall be given higher level of attention and its reliability and adequacy shall be considered as primary importance. 

For such reason, the fire water system unit shall be comprised of dedicated fire water storage tanks and set of pumping units to deliver sufficient amount of water with proper condition all over the plant. 

Since the river of Orento is considered as the main source of water for plant utility consumption, in order to avoid use of distinct intakes for fire water supply, a portion of water treated within RWS shall be considered for both fire water storage tank replenishments of and its make-up for case of minor consumptions. 

Water for firefighting shall be provided by an independent main fire ring fed by the fire pumps and normally cross connected to the Refinery cooling water system. A dedicated water storage system shall be provided for firewater applications. 

FWS comprises the following subsystems: 

  • Fire water jockey pumps
  • Fire water main pumps (one electrical and two diesel engines)
  • Fire water storage tanks (two tanks) 

Fixed installations will be provided in order to replenish the engine daily tanks automatically so they can be kept full (at least at two-thirds of tank) for time of demand. 

Precise dosage of corrosion inhibitor and biocide shall be injected at suitable pits on fire water tank filling lines and on the test lines considered for pumps weekly run test performance. 

This system is capable to provide 1,629 T/hr. of firewater continuously for about (6) hours.

Flushing Oil System (FOS)

The function of FOS is to supply flushing oil to the following units: 

  • BBU
  • VIS (6100 kg/h)
  • CDU (6215 kg/hr.)
  • Storage area 

Flushing oil is used for where high pour point materials are handled: 

  • Flushing of equipment (pumps, heat exchanges, filters and process lines) which are in congealing service for taking them for maintenance and any other works
  • Purging of the instruments which are in congealing service to avoid clogging of their leads/sensing probes
  • Start-up of some process units 

Design requirements for this unit are as following: 

  • During normal operation flushing oil header in BBU, CDU, VIS units and storage area is supplied by atmospheric gasoil header, while during pressure reduction in Atmospheric gasoil header branched from CDU/VDU, diesel product from flushing oil storage tank is pumped to header through pump (flushing oil transfer pump) as backup.
  • During start up and shutdown, diesel product from flushing oil storage tank is pumped through pump to serves as flushing oil for all units.
  • Flushing oil storage has a working capacity of 120 m3 for (8) hours of storage.

Flushing oil unit is located inside CDU/VDU battery limit.

Flare and Blowdown System (FBS)

FBS consists of the following flare headers to cover the relieving loads from the various sources in the refinery: 

  • Hydrocarbon flare header
  • Acid flare header 

The hydrocarbon relief gases from the sources contain non-hydrogen sulfide rich gases are transferred to the flare knock out drum via hydrocarbon flare header to separate the entrained liquids from the vapor. The liquid collected in the fare knock out drum is transferred to the slop tank by the flare knock out drum pumps. The outlet gas is sent to the flare stack which is equipped with a water seal located at the bottom of the stack. LP steam is injected to the water seal to avoid the freezing during freezing condition.

The acid flare header is intended to dispose hydrogen sulfide rich gases. The relieved acid gases from the various sources are transferred to the acid gas knock out drum via the acid flare header to separate the entrained liquid from the vapor. The separated acidic liquid is discharged to the common sour water feed surge drum. The outlet gases go to the acid flare stack, which is combined to the hydrocarbon flare stack extended to top of the hydrocarbon flare stack in one structure. 

The flare system consists of the following subsystems to receive and dispose the relieving loads from the various sources in the refinery: 

  • Flare network and headers
  • Flare knock out drums and pumps
  • Flare stacks (hydrocarbon flare stacks A/B & acid flare stack) and ignition package 

The refinery flare network will be consisting of the following flare headers: 

  • Hydrocarbon flare header
  • Acid gas flare 

HC flare system handles all hydrocarbon relief, with low H2S content, from the following units: 

  • VIS
  • DHT
  • BBU
  • NHT
  • NCR
  • LRU
  • FUS
  • Product storage 

Acid gas flare system handles all the relief with high H2S content from following units: 

  • VIS
  • DHT
  • NHT
  • SWS
  • SRU
  • ARU