P a g e 49 | 126 3.Hydraulic power unit (HPU). 4. Chemical Injection for subsea wells ( CI & KHI & Methanol skids ). ➢ Apart from being used to prevent hydrate formation, chemical thermodynamic inhibitors such as MeOH or glycol can also be used to dissociate hydrate plugs. The major problem associated with using chemicals for remediation is to get the inhibitor to reach the blockage and ensure good contact between the two. In a typical subsea system, these inhibitors are usually injected either from the subsea end or through the host. Hence, chemical injection-based remediation is generally more suited for plugs that occur close to these injection points. Hydrate blockages in subsea trees, jumpers, manifolds, risers or close to the riser base will be more successful in being remediated through chemical injection compared to a hydrate blockage in the middle of a flowline. To overcome distance constraints, delivery of the chemical inhibitor through coiled tubing can be considered, although that option also has a finite reach. Some other factors to keep in mind while using inhibitors to dissociate hydrates include: o Density differences - both MeOH and MEG have been shown to be successful in dissociating hydrates, but MeOH, in general, can be lighter than the hydrocarbon liquid phase, whereas MEG is usually heavier. As such, these density differences should be noted while choosing the right inhibitor. For example, if a hydrate blockage in a wellbore or near the riser base is being remediated with a chemical inhibitor, MEG will have a much better chance at reaching the blockage due to its higher density. On the other hand, MeOH might just float on top of any oil phase present and not contact the blockage at all. This problem will obviously depend on the local geometry surrounding the blockage, but for vertical systems, MEG is usually the inhibitor of choice over MeOH when it comes to remediation. o Dilution - given both MeOH and MEG are miscible in water, any water phase present around the blockage will result in dilution of the inhibitor at the contact area. Moreover, dissociation of hydrate releases water, which will further dilute any injected inhibitor. In practice, multiple batches of inhibitor are often injected to counter the effect of continuous dilution because of dissociation.
P a g e 50 | 126 5. W/HC separator. 6. Water treatment unit & Disposal tanks. Turbines area TWO Gas turbines A & B. ( used mainly for compressing the feed gas as a preparation for its dew pointing in the LTS trains ) .they compress the feed gas from 24 bar to circa 70 bar. A gas turbine is a type of turbine that uses pressurized gas to spin it in order to generate electricity or provide kinetic energy to an airplane or jet. The process to do so is called the Brayton cycle. In all modern gas turbines, the pressurized gas is created by the burning of a fuel like natural gas, kerosene, propane or jet fuel. The heat generated by this fuel expands air which flows through the turbine to supply useful energy. Gas turbines are theoretically simple, and have three main parts: Compressor Air is sucked in from the left and input to the compressors. Rows of fan blades compress the gas. In some turbines, the pressure of the air can get to 30x the input pressure. Combustor The high pressure air flows into this area, which is where the fuel is introduced. The fuel gets injected constantly into this part in order for the energy through the turbine to be constant. TurbineThe turbine is connected to the compressor blades by a shaft, and they spin separately. The compressors connect to the turbine which is connected to an output shaft, and because the turbine spins separately, it can get up to tremendous speeds due to the
P a g e 51 | 126 hot gas flowing through it. This final shaft generates enormous amounts of horsepower, with large airplane turbines generating nearly 110000 hp. Process Area This area contains: 1-Gas separation trains for gas conditioning (LTS-1 & LTS-2 & LTS-3 and Hannover LTS). While there are different styles, the primary function of all separators is in the name. They are used to separate the elements that flow into them.As the gas, oil, and water enter the separator, they hit an inlet diverter and begin to separate. Because these elements have different specific gravities, the separation process will continue at a gradual pace as long as they sit in the vessel. ➢ Gas will rise to the top of the vessel ➢ Oil will settle in the middle ➢ Water will drop to the bottom The gas will flow to a mist extractor at the top of the separator and be pulled out of the vessel and out to a sales line or for combustion.When the oil and water reach a predetermined height, they will activate liquid level control system and dump valve.
P a g e 52 | 126 Depending on the pressure, this may be a Lever-Operated Mechanical Dump Valve or a pneumatic or electric High Pressure Control Valve. 2-Glycol regeneration system (GR units - Exhaust tank - Lean Tank).
P a g e 53 | 126 3-condensate stabilization (pre-heater - G/H Sep.- stabilizer-condensate tanks).
P a g e 54 | 126 4-Gas metering (Ha’py-ATOLL).
P a g e 55 | 126 WHX Area This area contains: 1. Gas Turbine C (added with West Harbour Expansion Project-WHX). 2. New LER ( for new equipment added ). 3. New GR unit ( GR-601 ). 4. Flare KO drums with their associated pumps ( LP Flare & Cold Flare & Wet Flare ). 5. Holding Basin ( open drain system ) Atoll condensate Area 1. Atoll W/HC separator. 2. Coalescer filter. 3. Booster pumps. 4. Delivery pumps. 5. Launching trap. Utility Area 1. Instrument & utility air system ( used for pneumatic control of valves & utility air used in the plant activities ).
P a g e 56 | 126 2. Fuel gas system ( used as our fuel source for our equipment's operation like turbines – GRs – Reboilers- Generators…etc ). 3. New fuel gas heaters ( LP heater – HP heater ). 4. Service water system. 5. Firefighting system ( for fire fighting systems ). 6. Nitrogen Package ( for Turbines for dry gas seal ). 7. Diesel system ( for fueling our equipment that utilizes diesel as its own fuel like Emergency diesel generators- 2 fire fighting diesel pumps ). Plant’s fluids cycles
P a g e 57 | 126 Our plant is mainly dealing with four kinds of fluids, each fluid goes through a specific processing cycle till reaches its target- our main cycles are as the following: ➢ Gas cycle. ➢ Condensate cycle. ➢ Glycol cycle. ➢ Water cycle. Gas cycle’s overview 1. Ha’py & Taurt fluids delivered from sea line routed directionally to Slug Catcher to separate gas from liquid. 2. The outlet gas from slug catcher routed to gas compressors ( A & B & C ) for compression. 3. The compressed gas routed to tube side of the Gas/Gas Exchangers and is cooled by means of the dew-pointed gas discharged from the LTS Separator flowing through the shell side of the Gas/Gas Exchangers.
P a g e 58 | 126 4. The gas is then routed to H’apy & Taurt metering skids to meter fiscal standard dewpointed gas discharged from the Low Temperature Separation (LTS) Trains prior to being exported (UGDC – GASCO). Liquid Cycle (Condensate – waste water –glycol) Liquids are collected from slug catcher in the liquid gathering header/boot ( condensate - produced water ) from which they are transferred to the Water/HC Separator for further separation. The W/HC is a horizontal separator ( three phase type ) which separates liquids received from both the Ha’py and Taurt Slug-catchers , it routes the separated liquids to two different as the following : ➢ Produced Water is routed to produced water treatment unit and then to waste water disposal tanks A&B to be then disposed to waster water trucks. ➢ Condensate stream is routed to condensate preheater to start its condensate stabilization cycle.
P a g e 59 | 126 Condensate Cycle ⚫ The outlet condensate from W/H Sep. and LTS Trains, Gas Compression system and the Closed Drain System routed to the condensate pre-heater. ⚫ The Condensate Pre-heaters are two horizontally shell/tube heat exchangers which is used mainly to increase the temperature of the inlet feed which goes through the tube side ( condensate / glycol ) as a preparation for better separation at G/HC separator. ⚫ The function of the Glycol/HC Separator is to separate condensate from the water/glycol phase. ⚫ Hydrocarbon condensate recovered from natural gas may be shipped without further processing but is stabilized often for blending into the crude oil stream and thereby sold as crude oil. Stabilization process: ⚫ Stabilization of condensate streams can be accomplished through either flash vaporization or fractionation. ⚫ The condensate separated from Glycol/HC separator routed to stabilizer column (a 15 bubble cap tray column ) for stabilization process where stabilization of condensate in the stabilizer column and entrained gas discharged from the Glycol/HC Separator prevents vaporization during storage and export ⚫ The bubble caps are used to bring the rising vapors into direct contact with falling liquids within the stabilizer column to make the condensate travelling down strips
P a g e 60 | 126 out the heavier hydrocarbons from the gas stream travelling up, whilst the entrained gas, lighter components in the condensate are also stripped out. ⚫ The condensate is then routed to the shell side of the duty Condensate Pre-heater for heat exchanging with the new inlet feed at the tube side that enters the tube side of the preheater. ⚫ Stabilized condensate from the duty Condensate Pre-heater shell-side is routed to the Condensate Air Cooler where the temperature is decreased from 161 to 45°C, prior to being routed to the Condensate Storage Tanks for storage prior to being exported to Petrobel. Water Cycle ⚫ Water are collected from Water/HC Separator are routed to water treatment package. ⚫ The original operating concept of the Taurt Produced Water Treatment System was to receive and treat produced water from the Taurt Water/HC Separator and then routed to Water Disposal Tanks to get disposed to waste water trucks. Glycol Cycle
P a g e 61 | 126 ⚫ The rich glycol routed from LTS 1&2&3 to Glycol/HC separator to separate glycol from hydrocarbon. ⚫ After separation the rich glycol routed to travels downwards whilst coming into contact with four trays which aids the separation of gas entrained in the MEG stream. ⚫ Gas flashed off in the Degasser is routed to the Blowdown System – LP Flare. ⚫ Rich glycol flows by gravity from the Degasser to the Exhaust Glycol Tank. ⚫ The exhaust glycol tank feed to the tank is coming from the degasser and the outlet is routed to the suction of the exhaust glycol pumps to Glycol regeneration unit. ⚫ The function of the Glycol Regeneration Packages is to regenerate water laden (‘Rich’) MEG which was previously injected as ‘Lean’ (water free) MEG into the LTS Facilities Gas/Gas Exchangers. ⚫ The lean glycol from regeneration unit storage in lean tank to injection to LTS’s. Distribution control system (DCS) PROCESS CONTROL IMPORTANCE: ➢ Increase efficiency.
P a g e 62 | 126 ➢ Ensure Safety. ➢ Increase availability ➢ Reduce cost Control Theory Basics: To maintain a physical quantity, such as pressure, flow or temperature at a desired level during a technical process, this quantity can be controlled either by means of open loop control or closed loop control. Components of Control Loop: ⚫ Sensors ⚫ Converter ⚫ Transmitter ⚫ Signal ⚫ Indicator ⚫ Controller ⚫ Final Control element ⚫ Actuator Fire and gas system ⚫ West Harbour district is divided to nine zones with respect to fire and gas layout. ⚫ zone 1 is the admin building and H’apy substation working through addressable panel which connected to DCS system as indication only. ⚫ The plant zones started from 2 till 9 which is connected to ESD system used for monitor and automatic action. ⚫ CCTV and triple IR types used for fire detection. ⚫ Open path and point IR types used for gas leak detection.
P a g e 63 | 126 ⚫ Each zone has a local beacon and siren which also connected to DCS monitor station. Some equipment have its owned F&G detection and fighting : 1. The 3 gas generators A,B &C 2. The 2 diesel generators. 3. The 3 gas turbines. 4. Taurt LER. 5. WHX LER. 6. Control room. Fire Fighting System Why we need fire fighting system? 1. Protect personnel. 2. Control or extinguish fire and limit or protect fire escalation. 3. Reduce damage to facilities. 4. Reduce damage to the environment. The West Harbour Firewater System provides a dedicated firewater storage capacity for 130 minutes operation at a maximum distribution capacity of 210 m3/h. Fire protection equipment has been provided as detailed below: 1. Firewater Hydrants 2. Firewater Hose reels 3. Foam System and Water Cooling System 4. Fixed Locally Operated Fire Monitors 5. Fixed Remotely Operated Fire Monitors 6. Fixed Water Spray System 7. Water Mist Fire Suppression Systems 8. Gaseous Fire Suppression Systems
P a g e 64 | 126 9. Portable fire extinguishers The Firewater System comprises the following major components: 1. Firewater Storage Tanks (3 tanks). 2. Firewater Jockey Pumps (2 pumps). 3. Diesel-driven Firewater Pumps (2 pumps). 4. Foam Tank Blow Down system ⚫ Blow down system is one from the most critical facility in any gas plant as it is the last barrier in protection system for the plant. Blow down system provide plant with safe dispose for gases in emergency cases. ⚫ Blowdown systems facilitate the safe disposal to atmosphere of either hydrocarbon gas, or hydrocarbon gas and steam released from the individual West Harbour Gas Treatment Plant Process and Utility Systems. The four systems, being: 1- Continuous flare system 2- Wet flare system 3- Cold flare system 4- Cold vent system
P a g e 65 | 126 Types of plant shut down 1- Emergency shut down (ESD): Emergency depressurize for plant. All the gas plant shutdown valves (SDVs ) will close and all running compressors / gas turbines machines (GC) will shutdown and depressurize immediately for emergency cases ( FIRE ) . 2- Process shut down (PSD): In this type of shut down the inlet of plant shut down but the plant stays pressurized due to a process upset or problem ( GAS LEAKS ). How can we control in subsea? Equipment installed onshore to control and deliver communication , power , chemical and hydraulic to subsea wells: - Master control station (MCS). - Remote operator station (ROS). - Down hall pressure and temperature transmitter server ( DHPT). - Wet gas flow meter ( WGFM)
P a g e 66 | 126 - Solarton gas flow meter. - Uninterrupted power supply (UPS) ( for power support in case of power failure ) - Electrical power unit (EPU) - Hydraulic power unit (HPU) - Top side umbilical termination unit (TUTU) - Umbilical. MCS : ⚫ It is control commands for tree valves and HPU pumps also it can perform production shutdown. ⚫ Interface with DCS , WGFM ,DHPT and Solarton gas meter. ROS : ⚫ ROS doing same function of MCS it can control valves ,HPU pumps , …..etc DHPT : ⚫ It is submitted by Baker company and used to measure down hall pressure and temperature of the reservoir through two tools 1 and 2 . UPS : ⚫ It is provide continues power feed to subsea equipment without interruption for volt ,Hertz for two hrs only. EPU: ⚫ The main purpose of the EPU is to convert the incoming power supply and provide an adjustable power supply to suit the voltage, current and frequency requirements of the subsea control equipment . ⚫ The input voltage 380-400V with 50 Hz from UPS. ⚫ The EPU comprises two Topside Output Modules (TOM) for the Master Control Station (MCS) ⚫ Two Topside Output Module (TOM) for the Hydraulic Power Unit (HPU). ⚫ Four Subsea Output Modules (SOM) supplying the subsea equipment
P a g e 67 | 126 HPU : ⚫ The Hydraulic Power Unit is designed to provide the hydraulic power to operate the Production ( control Valves & chokes ) ⚫ The used hydraulic fluid is water based fluid CASTROL Transaqua HT 2. ⚫ It consists of two reservoirs Supply one to subsea system with capacity 2600 l and return reservoir with capacity 2800 l. ⚫ Two LP pumps one duty and one standby connected to supply tank to deliver hydraulic to subsea. ⚫ Circulation pump : used to fill the supply or return reservoir , Circulate the hydraulic control fluid from the supply reservoir to the return reservoir and vice versa and circulate the hydraulic control fluid within the supply or return reservoir. TUTU (Top side umbilical termination unit) : “ Umbilical : it is considered the meaning of connecting topside with subsea equipment. ⚫ The TUTU provides the hydraulic connection between umbilical and topside equipment. ⚫ The TUTU contains the electrical / FO junction boxes on a separate frame. ⚫ The TUTU contains the connections from the hydraulic supply lines, the chemical injection supply lines, the electrical power lines and the communication lines from the topside systems to the Production Control Umbilical.
P a g e 68 | 126 COMPANY PROFILE Misr Fertilizers Production Company, one of The Petroleum sector Companies and was established on July 1998. It added a factory for Water treatment. Its first name was Misr oil processing company, it is supposed to be established in Suez for petroleum refining but there were problems with the residents of the neighborhood and the governorate so this led to its move to Damietta, change its name and became for Urea industry. LOCATION It is inside Damietta General free zone. PRODUCTS Chemical Fertilizers such as Ammonia, Urea and Nitrogen. The company contains 3 labs: 1. Ammonia production unit 2. Urea production unit 3. Water treatment Ammonia production unit It is The Main source for Nitrogen Fertilizers and has many uses such as: • Fertilizers Production [Urea] to improve the production of agricultural land • Chemical Synthesis • Refrigeration • Pharmaceuticals • Fibers and Plastic nylon • Separate some precious metals
P a g e 69 | 126 Ammonia structure formula: It is aNitrogen atomfromair and three Hydrogen atoms derived mainly from natural gas, lighterthan air and dissolves in water. We can get Ammonia from the formula: N2 +3H2 =2NH3 But not as simple as we think, it is executed through six process: 1. Desulfurization: To purify the natural gas from impurities such as steam, Carbon dioxide, Hydrogen sulfide, Nitrogen, Argon Helium and Mercury by adding zinc oxide to hydrogen sulfide produces zinc sulfide and water. 2. Reforming Natural Gas: by super- heated steam at 770 Celsius in the presence of Nickel as catalyst produces H2, CO, CO2 this Mixture called synthesis gas. 3. Cooling the synthesis gas then passing air to it. The reactions are CO reacts with water producing H2, CO2 to increase the produced hydrogen that reacts with nitrogen to produce Ammonia. then we get rid of water by refrigeration condensation. 4. Removing CO2 by solving it in solution of di methyl ethanol amine. 5. Heating H2, N2 at 400 Celsius and 160 to 170 bars in presence of Fe as a catalyst we get Ammonia and unreacted gases we use them again. 6. Converting Ammonia from gaseous to liquid state by cooling Ammonia from 220 to 30 it is absorbed in Ammonia recovery. Natural gas Processing It is carried out through 3 processes: a) Natural gas compression and Desulphurization. This process is called gas purification because of the removal of poisonous gases. Natural gas which used in production synthesis gas contains compounds that are catalyst poisonous, reduces the catalyst lift and increases Sulphur is removed by two steps: 1. Hydrogenation: we mix Hydrogen with Natural gas so the Sulphur compounds will convert to hydrocarbons and hydrogen sulfide using Cobalt, Molybdenum as a catalyst 2. Adsorption; we use ZnO to adsorb H2S. Finally, Natural gasisfed to steam reforming section. b) Process Air Compressor: Air is drawn from atmosphere and compressed to 37 bars, then it heated to 450 Celsius, the steam is directed to Urea plant as a passivation air with pressure 1.5 bars. The compressor is driven by steam turbine which is powered by medium pressure steam. c) Reforming section: We can decrease the rate of methane out using Le chatelier principle by: • Higher steam to gas. • Higher temperature as the reaction is endothermic. • Lower pressure.
P a g e 70 | 126 CO Conversion Unit This process has many uses: Reducing the CO Slip, Provide the highest yield of CO2 and Maximize the CO2 Production to be used in Urea plant. The Process explanation: The reaction is exothermic so if the temperature increases less CO is converted to overcome that we use two stage system with a suitable inter cooling stages so we use HT reactor and LT reactor. LT-shift reactor allows the reaction to be completed at a low inlet temperature limited by the dew point temperature “usually the inlet temperature is 15 Celsius greater than the dew point temperature’’.in this reactor we use a mixture of CUO, Al2O3 as a catalyst and ZnO to protect the catalyst from any poisons such as Sulphur and chloride, ZnO and alumina give strength to the catalyst. HT-shift reactor: we use a mixture of iron oxide with chromium oxide as a catalyst. Using steam has a major importance: As Increasing steam increasing the conversion of CO and decreasing steam decreasing the conversion of CO and without steam iron oxide will reduce to pure iron so the structure of the catalyst will be changed and weaker and iron react with CO producing iron carbide and this lead to carbon deposition on the catalyst. Major problems of HT, LT reactor: Poisoning of the catalyst so we loss the activation of the catalyst and causes sintering of the catalyst. Condensation ofthe steam asrapid evaporation to condensing steam leadsto decreasing the efficiency of the catalystso we add a layer of ceramic balls for protection of the condensation of water droplets. Methanol formation is a side reaction may be occurred in LT reactor and it effects the CO2 quality and contaminates the process condensate. We must remove any residual amount of CO and CO2 as they act as a catalyst poisons to the Ammonia Plant using Ni as a catalyst and this called “Methanation” CO2 Removal Unit Process fundamentals: After removing most of CO gas to CO2, the CO2 must be removed because its poisoning effect for the catalyst in Ammonia converter, also to use in producing Urea. This can be done by absorbing the CO2 in a solution of K2Co3. K2Co3 is converted to KHCo3, the carbonate can be removed by stripping the CO2 gas out of the solution, and then it can be used again to absorb more CO2. This process depends on Temperature and pressure Although the absorption process is favored by low temperature of the solution, we cannot reduce the solution temperature to a point lower than its crystallization as this will cause a plugging in the pipe and valves and the solution will lose its concentration. The solution leaving the absorber contains a large amount of CO2 gas and it has a high percentage of potassium carbonate. we must reduce the pressure to 3 bar as doing this
P a g e 71 | 126 increases the efficiency of removing CO2, we benefit from solution power in driving the solution pump so the solution enters to the top of the absorber tower where it contacts with rising stripping steam which will strip the CO2 gas out of the solution and the temperature must be high enough for the stripping process. Before using CO2 in Urea plant, we must: 1. cool the CO2 gas to 35 Celsius which leads to condensation of all the stripping steam flowing withgas steam. 2. Remove any H2 gas. 3. Control CO2 pressure in order to become suitable for use in Ureaplant. Urea production unit There are two types of reactions to produce urea in the company: Condensation reaction 2NH3 + CO2→ NH2COONH4 + Heat Dehydration reaction NH2COONH4→ NH2COONH2 + H2O - Heat In urea plant, there are 4 stages for producing urea: Synthesis stage, Recirculation stage, Evaporation stage and Granulation stage 1- Synthesis stage: In which condensation reaction between NH3 and CO2 takes place under 145 bars pressure in order to form ammonium carbamate inside high pressure carbamate condenser (H.P.C.C). After that carbamate molecule loses water molecule and turns into urea molecule inside the reactor. The synthesis pressure consists of four equipment working under high pressure about 145 bars: High pressure Carbamate condenser, Reactor, High pressure striper and High-pressure scrubber.
P a g e 72 | 126 High production Carbamate condenser: In which the first reaction between NH3 and CO2 both in gas phase takes place to form Ammonium carbamate. This reaction is exothermic so in order to happen and continue heat produced from the reaction should be withdrawn. Carbamate in the liquid and gas phases flow to the reactor. Heat is withdrawn by the production of low-pressure steam about 4 bars. The equipment is a heat exchanger (shell and tube). The reaction happens inside the tubes and steam is produced in the shell side. Reaction between NH3 and CO2 gases doesn’t happen in a complete form so a part of These gases should be left to go to the reactor in the gas phase to react inside it. Reactor: Reactor is a vertical cylindrical equipment. It contains a number of perforated sieve trays (11 trays) to allow gases to flow through Perforations and liquid to flow through the distance between the wall and the tray. The liquid and gas phases carbamate go into reactor bottom out of the H.P.C.C and the gases reaction takes place first for the production of urea. Urea goes out of the reactor with about 35% concentration heading to the stripper. The reacted gases from reactor and inert gases goes to the scrubber. High pressure striper: Urea solution outlet reactor with concentration of about 35% goes to the stripper top. The rest is carbamate so it should be restored and directed again to the H.P.C.C. At the same time urea solution is concentrated from 35% to 57%. The stripping process is achieved by the counter current flow of CO2 gas from its compressor and (urea + carbamate) solutions inside stripper tubes. Medium pressure steam (about 20 bars) is directed to the stripper shell side for the decomposition of carbamate and stripping it from urea solution using CO2. Decomposed and stripped gases out solution of urea goes out of the stripper top with the CO2 heading to the H.P.C.C. Urea solution comes out stripper bottom after it is concentrated to about 57% heading to recirculation stage with low pressure (about 4 bars) for completing urea concentration process. High pressure scrubber: The outlet reactor gases are washed by the means of low concentration carbamate solution From recirculation stage for the absorption of NH3 and CO2.
P a g e 73 | 126 2- Recirculation stage After urea solution flows out of the stripper with concentration of about 57% the solution is flashed from 140 bars to 4 bars by means of control valve heading to rectifying column. In which the urea solution temperature is raised to get rid of NH3 and CO2 and increase urea solution to about 72%. Separated gases out of the solution head from rectifying column to the low-pressure carbamate condenser (L.P.C.C). Desorption and Hydrolyzation Stage: The desorption idea is based on the stripping of NH3 gas from diluted solution of about 5% NH3-water using low pressure steam (about 4 bars). This process takes place in the desorber which consists of two vertical separated columns, the 1st one contains 15 sieve trays and the 2nd contains 22 sieve trays. After ammonia gas is separatedfromammoniawater itflows to the reflux condenserwhere itis condensed and recycled into process again. The operation of hydrolyser is the same as the reactor but reversed In which urea is hydrolyzed by means of 24 bars steam to its primary components NH3 andCO2. After that the outlet gases from the hydrolyser goes to the reflux condenser to be recycled into the process again.
P a g e 74 | 126 3- Evaporation stage In the evaporation stage urea solution is concentrated from about 72% to 96% on two stages. The process takes place in tow equipment pre-evaporator and evaporator. The evaporator is shell and tube where urea solution flows into tubes and steam used for evaporation is in the shell side. Evaporation process takes place at 100°c in the pre-evaporator and 132°c in the evaporator and under vacuum about 0.3 bar abs and the process happens under these circumstances to reduce urea hydrolysis and biuret formation. 4- Granulation Stage Urea fertilizer granules are produced through the injection of 96% concentration urea melt into the granulator on a bed of urea fine granules inside it. The basic idea is to fluidize the fertilizer with air and it can be briefed as follows: First urea solution is concentrated through evaporators and transformed from liquid to - melt with 96% concentration. Urea melt is injected on a bed of urea fine granules where the melt is pushed with pressurized air called atomization air through small nozzles, urea melt sprays out the nozzles to accumulate on the fine granules of the bed where urea granules are shaped in the desired size. Urea formaldehyde (UF) is added to the urea melt before injection, this material helps in
P a g e 75 | 126 the granulation process and prevents crystallization of the product. Urea granules go out of granulator and through the 1st and final cooler they reach about 45°c and head to bagging unit. WATER TREATMENT Reverse osmosis (RO) Water purification technology that uses a partially permeable membrane to remove ions, molecules and larger particles from drinking water. In reverse osmosis: An applied pressure is used to overcome osmotic pressure, a colligative property, that is driven by chemical potential differences of the solvent, A thermodynamic parameter. Chemical potential of a species: The energy that can be absorbed or released due to a change of the particle number of Osmotic pressure: The minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane. The result:
P a g e 76 | 126 That the solutes retained on the pressurized side of the membrane and the Pure solvent is allowed to pass to the other side. To be “selective”, this membrane should not allow large molecules or ions through the pores (holes) but should allow smaller components of the solution (such as solvent molecules, i.e., water, H2 O) to pass freely. In the normal osmosis process: The solvent naturally moves from an area of low solute concentration; high water potential, through a membrane, to an area of high solute concentration; low water potential. Phase one Feed RO unit: Raw water; Pretreated, with 260 m3/hr go to Gravel filter with 260 m3/hr Feed RO water; the start point of Waster RO unit, then holding tank; Permeate, with 240 m3/hr, cooling tower and then Demine with 1000 m3/hr. Waste RO unit: Feed RO water go to Neutralization tank; Concentrated water 20 m3/hr, then MMF; Multimedia filter + UF; Ultra filtration unit, with 100 m3/hr, then Waste RO unit with 100 m3/hr, then reject tank with 10 m3/hr;the start point of Phase two. Phase Two After reaching Reject tank with 10 m3 /hr, it go to Multi flow system and then MMF+ Activate carbon filter and Filter press unit. After reaching Filter press unit, it go to Solid water. After reaching Multi flow system, it go to Brine RO unit, then Evaporator; reject with 3 m3 /hr and cooling tower with 6 m3 /hr. After reaching evaporator, it go to cooling tower and Evaporator pends, then Solid water.
P a g e 77 | 126 LOCATION 36 KM Alexandria/Cairo Desert Road El-Amereya – El-Nahda Territory – Alexandria, EGYPT. GENERAL DESIGN VALUES Plant Capacity: It produces 460,000 MT/Y polymer grade ethylene. Operating Hours: 8000 operating hours per year Feed: Ethane/Propane PRODUCTS: • High purity hydrogen • Hydrogen &methane rich off gas (Fuel and export) • C3 and heavier hydrocarbons(fuel) • Pyrolysis gasoline UNITS
P a g e 78 | 126 HOT SECTION It’s used to remove mercury from the feed. It’s one operation with single bed that’s not regenerated. The maximum temperature for the bed is 82 °c. there is one stand by. Amine system removes CO2 and H2S from incoming feed by using Diglycolamine as a solvent. Then the heated rich solventis regenerated in the stripper byusing steam and then the acid gases removed from water to incinerator. Treated fresh C2/C3 feed saturated with water, backup feed and ethane recycle are preheated with quench water in the ethane feed preheater to a temperature of 60c then the feed enters the heater and mixed with dilution steam. In it the feed is thermally cracked to produce more valuable productslike ethylene. The products enter primary TLE (transfer line exchangers) to stop cracking reaction, recover heat from heater effluent and generate SHP (super high pressure) steam then they enter secondary TLE to recover additional heat and preheat ethane feed. Quench tower is used to cool charge gas to 41 c by transferring heat to quench water for process users, condense dilution steam as process water and separate pyrolysis gasoline. They generate dilution steam to cracking heaters from process water by removing acid gases, volatile and heavy hydrocarbon from it
P a g e 79 | 126 COLD SECTION ` It consists of 4 stage centrifugal compressor. Compressor is driven by super high pressure steam turbine. It removes acid gases from charge gas by direct contact with circulating caustic (NaOH)then the charge gas enter 4th stage of CGC (charge gas compressor) Charge gas dryer removes moisture from charge gas down to < 1 mol ppm by absorbing the water into synthetic zeolites called molecular sieve. The removal of moisture is necessary to prevent the formation of ice and hydrates. There is one dryer on stream while the other is being regenerated in a cyclic operation. Dryer effluent wash tower removes such components (mainly benzene) from dryer effluent which could freeze. It maintains the required amount of methane at the bottoms to meet the correct methane specification in ethylene product.
P a g e 80 | 126 It consists of a series of heat exchangers which condenses dried charge gas (methane and heavier hydrocarbons) which is the feed to demethanizer and produces a H2 rich stream about 90 mol% purity. It separates methane from charge gas fed to it at 4 intermediate temperatures and the bottom is fed to deethanizer. Bottom product <500 WT ppm methane and net overhead product <1 mol% ethylene. It fractionates the ethylene rich demethanizer bottoms into: Overhead- mixed C2 stream (<0.1 mol% C3 ) Bottom- C3 and heavier (<0.14 mol% C2 ) Acetylene is impurity in ethylene product so it’s converted to ethylene; desirable, and ethane; undesirable, by hydrogenating the deethanizer net overhead stream. This reaction is exothermic. Acetylene converter is regenerated by using a mixture of steam, air, H2 and heated ethane recycle. C2 green oil KO drum receives the vapor product from acetylene converter and scrubs it from green oil which is a polymer formed inside the acetylene converter and can plug the trays. Vapor product is mixed with a C2 stream. Then Ethylene dryer dries the vapor effluent from the drum to prevent hydrate formation. There is one bed and the regeneration is manual. Dryer is bypassed during regeneration. It fractionates the deethanizer overhead stream from acetylene dryer: Overhead: (H2 -methane -ethylene recycle) Side draw: ethylene product from tray (99.95 min WT %) Bottom: ethane and it is recycled The 8 trays between the reflux and product draw achieve a large reduction in methane, CO and H2.
P a g e 81 | 126 Ethylene and Ethane Ethylene storage system stores ethylene and supplies downstream plant during unscheduled shutdown of ethylene plant. The Vaporizer superheats liquid ethylene by methanol for export to downstream plant. During plantshutdown, BOG; boil off gas, isrouted to ethylene storage BOG package. Ethane storage system stores ethane as back up feed to the plant. This isn’t a continuous operation. • Ethylene Refrigeration; It’s provided at 3 nominal temperature levels (-101 °c,-79 °c,61°c). • Ethylene product is used as refrigerant. The refrigeration is supplied by vaporizing the ethylene at pressures corresponding to the indicated temperatures. • Propane Refrigeration; It’s provided by 4 nominal temperature levels (-37 °c,-21° c, 4 °c,18°c) Deethanizer bottomsstored in butadiene surge drum are introduced to depropanizer where the propane, propylene &propyne are separated from depropanizer overhead and routed to OSBL LPGunit. Depropanizer bottom is sent to debutanizer where the C4 fraction as an overhead distillate is separated from C5 and heavier. The liquid mixed C4 feed stock from debutanizer is sent to feed vaporization drum where it’s circulated through 2 sets of thermosiphon heat exchanger.
P a g e 82 | 126 Main Washer and Rectifier/After washer Column System This system separates the vaporized mixed C4 feed into crude 1, 3-butadiene product and a raffinate; butanes and butanes, via a 2-step extractive distillation process. The solvent used is NMP; N-methyl pyrrolidone. The rich solvent is pumped to the solvent heater which preheats it to further enhance flashing of gases when the solvent enters the degasser where the pressure is decreased. Aside stream of C4 acetylenes is withdrawn from the middle of the degasser as they are more soluble in NMP than 1, 3-butadiene so the concentration of them are maximum in the middle. The overhead product from degasser is cooled in the cooling column by a stream of water/solvent then it is compressed in the recycle gas compressor and recycled as stripping gas to the bottom of the rectifier/after washer column. The water/solvent mixture from the bottom of cooling column is recycled after it’s cooled by feed vaporizer and solvent cooler. The bottom product from the degasser is the lean solvent and it’s cooled then recycled.
P a g e 83 | 126 Nitrogen Distillation (Product Purification) The crude 1, 3-butadiene is pumped from the after washer accumulator to the butadiene column where it’s distilled as a liquid side draw (tray 12) to the required productspecification. Product inhibitor, tertiary butyle catechol; TBC, diluted by a slip stream from the butadiene column accumulator is sprayed into the butadiene column condenser to reduce the propensity for polymerformation. TBC is also added to the product that’s sent to the storage. UTILITIES • SHP steam • HP steam • MP steam • Superheated LP steam It flows from cooling tower cells to the first pass heat exchanger where it’s heated approximately 5°c to 37°c. Then it’s collected and redistributed and heated up to 42°c. Finally, it’s returned to cooling tower. The fuel generated are: methane off gas, PSA off gas, H2 off gas and C3 and heavier. They consumed in: Cracking heater burners, HP steam boiler and Incinerators. It’s used as an inert gas from nitrogen package for purging and blanketing. Both are distributed from OSBL. UW is used for various hose stations (cleaning site, equipment,…) automatic water & filling of pump casings. Potable water is used for eye washer,safety showers and supplied to site operator shelter )S.O.S( for operator use.
P a g e 84 | 126 ZLD (Zero Liquid Discharge) No waste water discharge, reuse of the rejected water inside process again. 1. Tomeet strict environmental discharge guidelines 2. Tosatisfy critical water need in future 3. Sustainability - Filtration: Brine effluent is fed to the filter - Evaporation The product from the filter enters brine concentrator (BC) or falling film evaporator which has dual stage distributor trays. This process uses seeded slurry method that means allowing CaSO4 & SiO2 to crystallize on the seeds and stay in suspension instead of building upon the evaporator heat transfer surface (scaling). Startup seed quantity: 3,000 kg (equivalent to 6.9%WT).
P a g e 85 | 126 Crystallization BC blowdown is circulated at high velocity through FCHX to prevent scales formation and maintain high heat transfer coefficient. Then the brine enters the flash vessel where the pressure is lower than in FCHX so the vapor flash from the brine. The vapor flashed pass over mist eliminator to remove suspended droplets and then to the crystallizer condenser to exchange heat with cooling water and become distillate.
P a g e 86 | 126 Dewatering: 1. Belt Filter press 2. The Filtration Cycle 3. The Drying Cycle 4. The Discharge Cycle • Steam • Mist Eliminator • Pre-Heaters • Deaerator • Hydro cyclone • Anti-scale to HERO Reject Preheater • Anti-scale to Regen Waste Preheater • Caustic (NaOH) to BC Feed Equalization Tank • Caustic to Crystallizer Recirc Pump Suction • Anti-foam to Evaporator and Crystallizer Recirculation Pump Suctions
P a g e 87 | 126 ABOUT THE COMPANY Alexandria Mineral Oils Co. (AMOC) is an Egypt-based company that operates in the Petroleum industry. The Company specializes in the production of essential mineral oils, paraffin wax and its derivatives. Its manufacturing facilities are spread over 500,000 square meters in Alexandria. 1-The Lube and Special Oils complex, which manufactures neutral oils, paraffin waxes, soft/slack waxes and aromatics. 2- The Maximization of Gas Oil complex, which manufactures gas oil, naphtha and liquid petroleum gas (LPG) for local consumption, waxy distillates, heavy residue and black oil for blending with exported fuel oil, and biological sulfur. The company also operates four laboratories, and performs chemicalanalysis. Topped Crude from Atmospheric Distillation from Alexandria Petroleum Company and Amriya • Paraffinwax • Synthetic oil • BASE OIL SN-150 • Fuel Oil • Spindle oil • TRANSFORMER OIL • Gas Oil with 150 PPM Sulphur and decreased pour point (0°C). • Treated Naphtha. • Sweet Liquefied Petroleum Gas (LPG).
P a g e 88 | 126 UNIT 100 (SOLAR SECTION) - Vacuum distillation is a method of distillation where by the pressure above the liquid mixture to be distilled is reduced to less than its vapor pressure (usually less than atmospheric pressure) causing evaporation of the most volatile liquid(s) (those with the lowest boiling points). This distillation method works on the principle that boiling occurs when the vapor pressure of a liquid exceeds the ambient pressure. Vacuum is created by ejector and condenser. • Ejector is a static device which decrease the area so-according to continuity equation - velocity increases so -Bernoulli equation- pressure drop is created. It creates 25% Of the vacuum. • Condenser is a device which convert the vapor to liquid by decreasing temperature so vapors disappear and create high pressure drop. Vacuum distillation is done in a packed tower. The design capacity of the unit is about 1.250.000 MT/Y of Atmospheric Residue, producing: 1. Light and heavy vacuum gas oil. 2. Spindle oil (C25 –C30), (mixture of vacuum gas oil & light wax which use as lubricant in textiles). 3. Light wax distillate (C30 –C35). 4. Medium wax distillate (C35 –C40). 5. Heavy wax distillate (C40 –C50). 76.. Vacuum residue and black oil (C50+), (use in electric transformer unit).
P a g e 89 | 126 MIDDLE DISTILLATE DEWAXING UNIT“MDDU” The feed is a blend of Vacuum Gas Oil, Spindle Oil and Light Waxy Distillates. It is exothermic reaction. The design capacity of the unit is 600.000 MT/Y. Process Description: The feed is received by a tank then pumped to a heat exchanger where the feed is heated by the effluent from the reactor then it is heated by a natural draft furnace the reactor function isto: 1. Strip Sulfur, Nitrogen and Oxygen 2. Break long chain hydrocarbon 3. Saturate the broken chains by Hydrogen The effluent then is sent to the heat exchanger and cooled by the feed. Then it is sent to a hot high- pressure separator to separate the mixture from the reactor. The LPG and naphtha are produced as top products where solar is produced as a bottom product. Solar is then sent to a stripper and by using super-heated steam solar as a product is produced from the bottom and LPG and naphtha as a top product. LPG and naphtha are sent to cold high-pressure separator to separate hydrogen sulfide and hydrogen -as a top product-from LPG and naphtha as-a bottom product- LPG and naphtha from cold and hot high-pressure Separator are collected then sent to a de-butanizer to separate LPG as a top product and naphtha as a bottom product. Naphtha is then sent to be distilled. The top product is sent to storage and the bottom product is mixed with gas oil. The products of MDDU are by products, such as: 1. Gas Oil with 150 PPM Sulphur and decreased pour point (0°C). 2. Treated Naphtha from NH3 & H2S & O2. 3. Sweet Liquefied Petroleum Gas (LPG). UNIT 200 (MEK-DEWAXING) MEK: stands for Methyl Ethyl Ketone The aim of this unit: Separate oil from wax. Temperature = -14°c Solvent: 65% MEK & 35% Toluene
P a g e 90 | 126 The Mechanism of the unit: First stage: adjust ratio of solid to liquid by mixture solvent of MEK & Toluene. MEK dissolve wax and prevent dissolve wax in toluene & Toluene dissolve oil. Ratio of oil/ wax > 75% • BASE OIL • Fuel Oil • Spindle oil • TRANSFORMER OIL • Synthetic oil • PARAFFIN WAX After separating aromatics oil and wax are separated by crystallization in a shellers which cool the mixture and produce wax crystals then by adding solvent and filtration oil is separated fromwax. Feed is sent to the shellers which has12 tubes-by a double pump each tube has a shell, the first 3 tubes contain a cooling substance to cool the feed to-15c for the crystallization then to send it to the filter it must be heated to110c In the first stage toluene and MEK are added as solvents, toluene dissolve oil and wax and settle the wax. Then the second and third stages is to confirm the separation Then wax is separated in to hard and soft wax, the soft wax is sent to the mazut and the hard and medium wax is sent to the unit 400 and the oil to the unit 300 for hydro-finishing. The main purpose of hydro-finishing is to improve the pour point. The secondary purposes are to improve viscosity index and color. UNITS 300 & 400 (HYDROGENATION) Afterthe process ofseparating oilsfrom waxes,the feed entersthe heat exchangerfor pre-heating and to raise the temperature gradually, and then receiving it on filter for purification from solid impurities. The feed enters the unit by Rotary pump, Hydrogen is mixed with the feed by the compressors. The feed entersthe furnace then the reactor(actually two reactors) which hydrogen is consumed through the reactions. Hydrogen saturates the hydrocarbon and separates impurities as following: 1. Sulfur as hydrogen sulfide 2. Oxygen as water 3. Nitrogen as ammonia
P a g e 91 | 126 HYDROGENATION OFWAX (400) It’s the unit for treatment of different types of wax: 1. Medium hard wax 2. heavy hard wax 1- First stage is thefeed: The feed will be received on heat exchanger to rise its temperature gradually then it will go to feed filter to purify it from solid impurities before entering feed vessel. The feed will enter the unit by rotary pump then be mixed with H2. Heat exchanger will complete the raise in temperature. The feed will enter an electric heater. Then the mixture will enter the reactor that consume the H2 during the reaction. Then mixture will be cooled by heat exchanger to control the inlet temperature of second reactor. Then the mixture will be cooled to separating temperature. Then it will start in refining from impurities (cleaning process) 2- Secondstage is refining (impurities separation) This process will be done in 3 stages: 1- First (high press & high temp) Gases will be evolved and burned in the flare 2- Second (extraction tower – low temp) Inject extraction steam to remove any suspended gases from the surface of wax molecules 3- Third (Drying tower) To prevent water condensation in the extraction tower. UNIT 550 Removes H2S gaseous streams (Acid and sour gases) by absorption in a mild alkaline solution and the oxidation of the absorbed sulfide to eliminated sulfur by naturally occurring micro-organisms. The unit protects the environment from acid gas pollution.
P a g e 92 | 126 The Mechanism of the unit: First stage: adjust ratio of solid to liquid by mixture solvent of MEK & Toluene. MEK dissolve wax and prevent dissolve wax in toluene & Toluene dissolve oil. Ratio of oil/ wax > 75% • BASE OIL • Fuel Oil • Spindle oil • TRANSFORMER OIL • Synthetic oil • PARAFFIN WAX After separating aromatics oil and wax are separated by crystallization in a shellers which cool the mixture and produce wax crystals then by adding solvent and filtration oil is separated fromwax. Feed is sent to the shellers which has12 tubes-by a double pump each tube has a shell, the first 3 tubes contain a cooling substance to cool the feed to-15c for the crystallization then to send it to the filter it must be heated to110c In the first stage toluene and MEK are added as solvents, toluene dissolve oil and wax and settle the wax. Then the second and third stages is to confirm the separation Then wax is separated in to hard and soft wax, the soft wax is sent to the mazut and the hard and medium wax is sent to the unit 400 and the oil to the unit 300 for hydro-finishing. The main purpose of hydro-finishing is to improve the pour point. The secondary purposes are to improve viscosity index and color. UNITS 300 & 400 (HYDROGENATION) Afterthe process ofseparating oilsfrom waxes,the feed entersthe heat exchangerfor pre-heating and to raise the temperature gradually, and then receiving it on filter for purification from solid impurities. The feed enters the unit by Rotary pump, Hydrogen is mixed with the feed by the compressors. The feed entersthe furnace then the reactor(actually two reactors) which hydrogen is consumed through the reactions. Hydrogen saturates the hydrocarbon and separates impurities as following: 1. Sulfur as hydrogen sulfide 2. Oxygen as water 3. Nitrogen as ammonia
P a g e 93 | 126 HYDROGENATION OFWAX (400) It’s the unit for treatment of different types of wax: 3. Medium hard wax 4. heavy hard wax 1.First stage is thefeed: The feed will be received on heat exchanger to rise its temperature gradually then it will go to feed filter to purify it from solid impurities before entering feed vessel. The feed will enter the unit by rotary pump then be mixed with H2. Heat exchanger will complete the raise in temperature. The feed will enter an electric heater. Then the mixture will enter the reactor that consume the H2 during the reaction. Then mixture will be cooled by heat exchanger to control the inlet temperature of second reactor. Then the mixture will be cooled to separating temperature. Then it will start in refining from impurities (cleaning process) 2.Second stage is refining (impurities separation) This process will be done in 3 stages: • First (high press & high temp) Gases will be evolved and burned in the flare • Second (extraction tower – low temp) Inject extraction steam to remove any suspended gases from the surface of wax molecules • Third (Drying tower) To prevent water condensation in the extraction tower. UNIT 550 Removes H2S gaseous streams (Acid and sour gases) by absorption in a mild alkaline solution and the oxidation of the absorbed sulfide to eliminated sulfur by naturally occurring micro-organisms. The unit protects the environment from acid gas pollution.
P a g e 94 | 126 WAXES POURING AND PACKAGINIG Aftertreatment, Heavy and medium wax enterthe filter in liquid state then enterthe filter to remove the impurities then cooled to solidify. UTILITIES Like steam Generation, Instrument air, WWT and cooling towers STEAM GENERATION (BOILERS) Boilers are two main types: 1- Fire tube boiler In which hot gases pass from a fire through one or (many) more tubes running through a sealed container of water. The heat of the gases is transferred through the walls of the tubes by thermal conduction, heating the water and ultimately creating steam. Not used very much in industry as it’s limited in Q and P, presence of welding act as “weakness point “, not carry over high P and high T. 2- Water tube boiler In such kind of boiler where the water is heated inside tubes and the hot gasses surround them. This type has larger heating surface can be achieved by using more numbers of water tubes, also the movement of water is much faster than that of fire tube boiler, hence rate of heat transfer is high which results into higher efficiency.
P a g e 95 | 126 Main product here (in AMOC) is the steam “super-heated steam “, treatment of industrial waste in the company there 3 reboilers: Capacity = 6 ton /hr per reboiler There are three types of boilers and depends on the type of steam: - 1- Super-Heated “P=14.2 kg/cm2, T=270oc” 2- Saturated Steam “P=4 kg/cm2, T=200oc” 3- Saturated Liquid “P=4 kg/cm2, T=150oc” In the cooling tower the warm cooling water return from the process is cooled down by heat transfer to atmosphere. The cooled water is collected in the cold-water basin which is arranged beneath the cooling tower. From the cold-water basin, the water flows into the pump suction basin located alongside the cooling tower. Cooling water Pumps which feed the water back to process are installed in the pump suction basin. The heat of the water is partially removed by direct heating of the cooling air, but mainly by evaporation of part of the hot water. The performance of a cooling tower is characterized by the closeness to which the re-cooled water temperature approaches the cooling limit. Hot water is coming at the inlet of the tower and pumped up to the header. The header contains nozzles and sprinklers which is used to spray water, and it will increase the surface area of water. After that, water comes to PVC filling; it used to reduce the speed of water. At the top the cooling tower, fans are used to lift air from bottom to the top. Because of slow speed and more contact area of water, it makes a good connection between air and hot water. The process will reduce the temperature of water by evaporation process and cooled water is collected at the bottom of the cooling tower in the basin, and this cooled water is used again in the process.
P a g e 96 | 126 TYPES OF COOLINGTOWERS In this type of cooling tower, fan is not used for circulating air but here, by enclosing the heated air in the chimney and it will create pressure difference between heated air and surrounding air. Because of this pressure difference air enters in to the cooling tower. It requires large hyperbolic tower, so capital cost is high but operating cost is low because of absence of electrical fan. Issame as natural draught cooling tower, only difference isthat here fan is mounted on the cooling tower. Induced draft implies an inlet fan placed on top of the cooling tower and the creation of low pressure. Forced draft means an exhaust fan placed at the base of the cooling tower which then causes overpressure.
P a g e 97 | 126 STORAGE TANKS AMOC has about 120 complete and integrated storage tanks; they handle feed, intermediate and final products with different capacities and according to the international standards. The total storage capacity of all tanks is 200,000 MT. All the tanks are provided with a complete automatic fire fighting system and an international automatic system ENRAF for data recording during operation such as volume, temperature of the petroleum products inside these tanks. Most of storage tanks are insulated for energy conservation and some are provided with Nitrogen blanket to avoid any changes of solvents or petroleum products specifications inside these tanks. These tanks can have different sizes, ranging from 2 to 60 m diameter or more. They are generally installed inside containment basins in order to contain spills in case of rupture of the tank. For more flexibility in operation all tanks are connected by each other through complete pipe-lines net. 1. Fixed-roof tanks 2. Internal floating rooftanks 3. External floating rooftanks 4. Domed external floating roof tanks 5. Horizontal tanks 6. Pressure tanks 7. Variable vapor space tanks 8. LNG (Liquefied Natural Gas) tanks The first four tank types are cylindrical in shape with the axis oriented perpendicular to the sub grade. These tanks are almost exclusively above ground. Horizontal tanks can be used above and below ground. Pressure tanks often are horizontally oriented and spherically shaped to maintain structural integrity at high pressures. They are located above ground. Variable vapor space tanks can be cylindrical orspherical in shape.
P a g e 98 | 126 HYDROGEN PRODUCTIONWAYS 1. De-hydrogenation. 2. Hydro-cracking. 3. Steam methane reforming. Natural gas is sent to knock-out drum to separate impurities then sulfur is removed. Which is done in a reformer by mixing steam with methane in the presence of a catalyst by applying heat and pressure. The catalyst consists of 2 stages, at the first stage all compounds are broken to get C1 then at the next stage hydrogen is stripped. Water is separated by a separator, CO is converted into CO2 as CO2 is not poisoning the catalyst. After the reformer hydrogen is sent to (Pressure Swing Adsorption) PSA -with a purity of 76%- which contain a catalyst and molecular sieve to get a purity of 99.99%. It is produced by the atmospheric air. Compressed air is cooled by ammonia then sent to TSA (Temperature swing adsorption) then water is separated then Co2 and impurities are separated then oxygen and nitrogen are cooled until conversion into liquid then they are separated by distillation. PSA is a technique of gas separation where at low temperature adsorption occurs and at high temperature desorption occur and the TSA is the vice versa.