Process input and outputs

Major products

Petroleum products are usually grouped into three categories: light distillates (LPG, gasoline, naphtha), middle distillates (kerosene, diesel), heavy distillates and residuum (heavy fuel oil, lubricating oils, wax, asphalt). This classification is based on the way crude oil is distilled and separated into fractions (called distillates and residuum).

Liquefied petroleum gas (LPG)

Gasoline (also known as petrol)

Naphtha

Kerosene and related jet aircraft fuels

Diesel fuel

Fuel oils

Lubricating oils

Paraffin wax

Asphalt and tar

Petroleum coke

The proposed refinery process plant at the Olokola Free Trade Zone (OKFTZ) is designed to take in Nigerian crude oil stream, with the major supply coming from the Chevron Flow-station. The input and outputs are shown in the following schematic diagram.

7.0 Utility requirements

The following utility requirements are requisite for the refinery plant project. The basic utilities are:

Electricity:

Research shows that power generation in Nigeria is unstable and most times plunges below 1,500 MW of consumable electricity. This means that for a mega project like the Ondo State refinery project, it will be reasonable to make alternative provision for the supply of electricity to the plant. To this end, it is recommended that the residual or off-gas from the refinery plant should be used for power generation; for plant operations and for other support services to the plant.

In addition, the Ventech and Nigerian Staff living quarters and recreational facilities will be powered using the power generated from the refinery off-gas.

Water supply

The refinery plant management and operation personnel will need drinkable pipe borne water for drinking and domestic use. Our survey shows that the Free Trade Zone has no standard water supply system in place. It is therefore recommended that integrated water supply system should be put in place to cater for all the industrial and domestic water needs in the refinery plant industrial park.

Process chemicals

Refining of crude oil requires the addition of some chemicals for effective treatment of the raw crude before the refining process proper. It is therefore recommended that the basic infrastructures should be put in place to handle the bulk chemicals that will be used for refinery operations.

8.0 Manpower requirement

Ventech will work with OKFTZ Refinery in providing Management Training Seminars utilizing Associated Companies that train Fortune 500 Employees and Executives as well as screening local Nigerian Workers to ensure qualified candidates will be employed at the Refinery.

Construction Management:

The Construction Management Team will consist of U.S. Expatriates from Ventech Pasadena offices - Site Construction Manager, Foreign Expatriates, and when practical, Nigerian nationals. Since the goal is to provide a World-Class Refinery for Ondo State, the Refinery Company will employ qualified, experienced construction management personnel in key positions.

The Construction Management Team will consist of approximately the following positions and not everyone on the team will be on-site for the full duration of the Project:

Overall Refinery Construction Manager

Pipeline Construction Manager

Community Liaison Officer and/or Public Relations Officer

Personnel Administrator

Construction Leads

Civil, Mechanical (Equipment and Piping) and Structural

Instrumentation and Electrical and Tank Farm

Project Controls Technicians

Material Handling Personnel

Safety / First Aid Coordinator

QA/QC Coordinator / Inspector

Secretary / Office Manager

The Construction Manager will arrive on-site at Project Set-off. His top priority activities will include:

· Establish the field office and Setup the expatriate housing compound

· Arrange and expedite the geo-technical survey, site survey and water sampling activities

· Identify the construction lay down area

· Hire local field support staff

· Clear and secure the site

· The remainder of the Construction Management Team will be mobilized to the job site when required by the Project.

Ventech offers end-to-end processing solutions designed to take you from planning to production—fast. We are committed to providing you with high-quality solutions at the lowest possible price.

Labour:

Ventech will hire field labour directly from the available local labour pool. All required unskilled labour would be hired from the local economy. Skilled labour, when available, will also come from the local economy. Not more than 10 Expatriates will fill skilled labour needs that cannot be filled by locals. Ventech understands that it is very important to utilize local labour as much as possible and will try to limit the number of expatriate labourers employed.

9.0 Health and Safety Considerations:

Fire Prevention and Protection - Even though these are closed processes, heaters and exchangers in the atmospheric and vacuum distillation units could provide a source of ignition, and the potential for a fire exists should a leak or release occur.

Safety - An excursion in pressure, temperature, or liquid levels may occur if automatic control devices fail. Control of temperature, pressure, and reflux within operating parameters is needed to prevent thermal cracking within the distillation towers. Relief systems should be provided for overpressure and operations monitored to prevent crude from entering the reformer charge.

The sections of the process susceptible to corrosion include (but may not be limited to):

· Preheat exchanger (HCI and H2S),

· Preheat furnace and bottoms exchanger (H).

· Atmospheric tower and vacuum furnace (H2S, sulphur compounds, and organic acids),

· Vacuum tower (H2S and organic acids), and overhead (H2S, HCl, and water).

Where sour crudes are processed, severe corrosion can occur in furnace tubing and in both atmospheric and vacuum towers where metal temperatures exceed 450 degrees F. Wet H2S also will cause cracks in steel. When processing high-nitrogen crudes, nitrogen oxides can form in the flue gases of furnaces. Nitrogen oxides are corrosive to steel when cooled to low temperatures in the presence of water.

Chemicals are used to control corrosion by hydrochloric acid produced in distillation units. Ammonia may be injected into the overhead stream prior to initial condensation and/or an alkaline solution may be carefully injected into the hot crude-oil feed. If sufficient wash-water is not injected, deposits of ammonium chloride can form and cause serious corrosion. Crude feedstock may contain appreciable amounts of water in suspension, which can separate during start-up and, along with water remaining in the tower from steam purging, settle in the bottom of the tower. This water can be heated to the boiling point and create an instantaneous vaporization explosion upon contact with the oil in the unit.

Health- Atmospheric and vacuum distillations are closed processes and exposures are expected to be minimal. When sour (high-sulphur) crudes are processed, there is potential for exposure to hydrogen sulphide in the preheat exchanger and furnace, tower flash zone and overhead system, vacuum furnace and tower, and bottoms exchanger. Hydrogen chloride may be present in the preheat exchanger, tower top zones, and overheads.

Wastewater may contain water-soluble sulphides in high concentrations and other water-soluble compounds such as ammonia, chlorides, phenol, mercaptans, etc., depending upon the crude feedstock and the treatment chemicals.

Safe work practices and/or the use of appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as heat and noise, and during sampling, inspection: maintenance, and turnaround activities.

Solvent Extraction and Dewaxing - Solvent treating is a widely used method of refining lubricating oils as well as a host of other refinery stocks. Since distillation (fractionation) separates petroleum products into groups only by their boiling-point ranges, impurities may remain. These include organic compounds containing sulphur, nitrogen, and oxygen; inorganic salts and dissolved metals; and soluble salts that when present in the crude feedstock. In addition, kerosene and distillates may have trace amounts of aromatics and naphthenes, and lubricating oil base-stocks may contain wax.

Solvent refining processes including solvent extraction and solvent dewaxing usually remove these undesirables at intermediate refining stages or just before sending the product to storage.

Solvent Extraction - The purpose of solvent extraction is to prevent corrosion, protect catalyst in subsequent processes, and improve finished products by removing unsaturated, aromatic hydrocarbons from lubricant and grease stocks. The solvent extraction process separates aromatics, naphthenes, and impurities from the product stream by dissolving or precipitation. The feedstock is first dried and then treated using a continuous countercurrent solvent treatment operation. In one type of process, the feedstock is washed with a liquid in which the substances to be removed are more soluble than in the desired resultant product. In another process, selected solvents are added to cause impurities to precipitate out of the product. In the adsorption process, highly porous solid materials collect liquid molecules on their surfaces. The solvent is separated from the product stream by heating, evaporation, or fractionation, and residual trace amounts are subsequently removed from the raffinate by steam stripping or vacuum flashing. Electric precipitation may be used for separation of inorganic compounds. The solvent is then regenerated to be used again in the process.

The most widely used extraction solvents are phenol, furfural, and cresylic acid. Other solvents less frequently used are liquid sulphur dioxide, nitrobenzene, and dichloroethyl ether. The selection of specific processes and chemical agents depends on the nature of the feedstock being treated, the contaminants present, and the finished product requirements.

Solvent Dewaxing - Solvent dewaxing is used to remove wax from either distillate or residual basestocks at any stage in the refining process. There are several processes in use for solvent dewaxing, but all have the same general steps, which are: (1) mixing the feedstock with a solvent, (2) precipitating the wax from the mixture by chilling, and (3) recovering the solvent from the wax and dewaxed oil for recycling by distillation and steam stripping.

Usually two solvents are used: toluene, which dissolves the oil and maintains fluidity at low temperatures, and methyl ethyl ketone (MEK), which dissolves little wax at low temperatures and acts as a wax precipitating agent.

Other solvents that are sometimes used include benzene, methyl isobutyl ketone, propane, petroleum naphtha, ethylene dichloride, methylene chloride, and sulphur dioxide. In addition, there is a catalytic process used as an alternate to solvent dewaxing.

Health and Safety Considerations:

Fire Prevention and Protection - Solvent treatment is essentially a closed process and, although operating pressures are relatively low, the potential exists for fire from a leak or spill contacting a source of ignition such as the drier or extraction heater. In solvent dewaxing, disruption of the vacuum will create a potential fire hazard by allowing air to enter the unit.

Health: Because solvent extraction is a closed process, exposures are expected to be minimal under normal operating conditions. However, there is a potential for exposure to extraction solvents such as phenol, furfural, glycols, methyl ethyl ketone, amines, and other process chemicals. Safe work practices and or the use of appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat, and during repair, inspection, maintenance, and turnaround activities.

Thermal Cracking - Because the simple distillation of crude oil produces amounts and types of products that are not consistent with those required by the marketplace, subsequent refinery processes change the product mix by altering the molecular structure of the hydrocarbons. One of the ways of accomplishing this change is through cracking, a process that breaks or cracks the heavier, and higher boiling-point petroleum fractions into more valuable products such as gasoline, fuel oil, and gas oils. The two basic types of cracking are thermal cracking, using heat and pressure, and catalytic cracking.

The first thermal cracking process was developed around 1913. Distillate fuels and heavy oils were heated under pressure in large drums until they cracked into smaller molecules with better antiknock characteristics. However, this method produced large amounts of solid, unwanted coke. This early process has evolved into the following applications of thermal cracking: visbreaking, steam cracking, and coking.

Visbreaking Process- Visbreaking, a mild form of thermal cracking, significantly lowers the viscosity of heavy crude- oil residue without affecting the boiling point range. Residual from the atmospheric distillation tower is heated (800-950 degrees F) at atmospheric pressure and mildly cracked in a heater.

It is then quenched with cool gas oil to control overcracking and flashed in a distillation tower. Visbreaking is used to reduce the pour point of waxy residues and reduce the viscosity of residues used for blending with lighter fuel oils.

Middle distillates may also be produced, depending on product demand. The thermally cracked residue tar, which accumulates in the bottom of the fractionation tower, is vacuumed flashed in a stripper and the distillate recycled.

Coking Processes - Coking is a severe method of thermal cracking used to upgrade heavy residuals into lighter products or distillates. Coking produces straight-run gasoline (coker naphtha) and various middle -distillate fractions used as catalytic cracking feedstock. The process so completely reduces hydrogen that the residue is a form of carbon called coke. The two most common processes are delayed coking an, continuous (contact or fluid) coking. Three typical types of coke are obtained (sponge coke, honey corn coke, and needle coke) depending upon the reaction mechanism, time, temperature, and the crude feedstock.

Delayed Coking - In delayed coking the heated charge (typically residuum from atmospheric distillation towers) is transferred to large coke drums, which provide the long residence time needed to allow the cracking reactions to proceed to completion. Initially the heavy feedstock is fed to a furnace which heat: the residuum to high temperatures (900-950 degrees F) at low pressures (25-3Opsi) and is designed and controlled to prevent premature coking in the heater tubes. The mixture is passed from the heater to one or more coker drums where the hot material is held approximately 24 hours (delayed) at pressures of 25 75psi, until it cracks into lighter products. Vapours from the drums are returned to a fractionator when gas, naphtha, and gas oils are separated out. The heavier hydrocarbons produced in the fractionator and recycled through the furnace.

After the coke reaches a predetermined level in one drum, the flow is diverted to another drum to maintain continuous operation. The full drum is steamed to strip out un-cracked hydrocarbons, cooled by water injection, and de-coked by mechanical or hydraulic methods. The coke is mechanically removed by an auger rising from the bottom of the drum. Hydraulic decoking consists of fracturing the coke bed with high-pressure water ejected from a rotating cutter.

Continuous Coking - Continuous (contact or fluid) coking is a moving-bed process that operates at temperatures higher than delayed coking. In continuous coking, thermal cracking occurs by using heal transferred from hot, recycled coke particles to feedstock in a radial mixer, called a reactor, at a pressure of 50 psi. Gases and vapours are taken from the reactor, quenched to stop any further reaction, and fractionated.

The reacted coke enters a surge drum and is lifted to a feeder and classifier where the larger coke particle: are removed as product. The remaining coke is dropped into the pre-heater for recycling with feedstock Coking occurs both in the reactor and in the surge drum. The process is automatic in that there is; continuous flow of coke and feedstock.

Health and Safety Considerations:

Fire Protection and Prevention - Because thermal cracking is a closed process, the primary potential for fire is from leaks or releases of liquids, gases, or vapours reaching an ignition source such as a heater.

The potential for fire is present in coking operations due to vapour or product leaks. Should the kin temperatures get out of control, an exothermic reaction could occur within the coker.

Safety - In thermal cracking when sour erodes are processed, corrosion can occur where met. Temperatures are between 450 and 900 degrees F. above 900 degrees F coke forms a protective layer on the metal. The furnace, soaking drums, lower part of the tower, and high-temperature exchangers are usually subject to corrosion. Hydrogen sulphide corrosion in coking can also occur when temperatures are not properly controlled above 900 degrees F.

Continuous thermal changes can lead to bulging and cracking of coke drum shells. In coking, temperature control must often be held within a 10-20 degrees F range, as high temperatures will produce coke that is too hard to cut out of the drum. Conversely, temperatures that are too low will result in high asphaltic-content slurry. Water or steam injection may be used to prevent build-up of coke in delayed coker furnace tubes. Water must be completely drained from the coker, so as not to cause an explosion upon recharging with hot coke. Provisions for alternate means of egress from the working platform on top of coke drums are important in the event of an emergency.

Health:

The potential exists for exposure to hazardous gases such as hydrogen sulphide and carbon monoxide, and trace poly nuclear aromatics (PNAs) associated with coking operations. When coke is moved as slurry, oxygen depletion may occur within confined spaces such as storage silos, since wet carbon will adsorb oxygen. Wastewater may be highly alkaline and contain oil, sulphides, ammonia, and/ or phenol.

The potential exists in the coking process for exposure to burns when handling hot coke or in the event of a steam line leak, or from steam, hot water, hot coke, or hot slurry that may be expelled when opening cokers.

Safe work practices and/ or the use of appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as heat and noise, and during process sampling, inspection, maintenance, and turnaround activities.

Acid, Caustic, or Clay treating - Sulphuric acid is the most commonly used acid treating process. Sulphuric acid treating results in partial or complete removal of unsaturated hydrocarbons, sulphur, nitrogen, and oxygen compounds, and resinous and asphaltic compounds. It is used to improve the odor, color, stability, carbon residue, and other properties of the oil. Clay/lime treatment of acid-refined oil removes traces of asphaltic materials and other compounds improving product colour, odour, and stability.

Caustic treating with sodium (or potassium) hydroxide is used to improve odour and colour by removing organic acids (naphthenic acids, phenols) and sulphur compounds (H2S) by a caustic wash. By combining caustic soda solution with various solubility promoters (e.g., methyl alcohol and cresols), up to 99% of all as well as oxygen and nitrogen compounds can be dissolved from petroleum fractions.

Drying and Sweetening - Feedstock from various refinery units are sent to gas treating plants where butanes and butenes are removed for use as alkylation feedstock, heavier components are sent to gasoline blending, propane is recovered for LPG, and propylene is removed for use in petrochemicals. Some mercaptans are removed by water-soluble chemicals that react with the mercaptans. Caustic liquid (sodium hydroxide), amine compounds (diethanolamine) or fixed- bed catalyst sweetening also may b( used. Drying is accomplished by the use of water absorption or adsorption agents to remove water from the products. Some processes simultaneously dry and sweeten by adsorption on molecular sieves.

Sulphur Recovery - Sulphur recovery converts hydrogen sulphide in sour gases and hydrocarbon streams tr elemental sulphur. The most widely used recovery system is the Claus process, which uses both thermal and catalytic-conversion reactions. A typical process produces elemental sulphur by burning hydrogen sulphide under controlled conditions. Knockout pots are used to remove water and hydrocarbons from feed gas streams. The gases are then exposed to a catalyst to recover additional sulphur. Sulphur vapour from burning and conversion is condensed and recovered.

Hydrogen Sulphide Scrubbing - Hydrogen sulphide scrubbing is a common treating process in which the hydrocarbon feedstock is first scrubbed to prevent catalyst poisoning. Depending on the feedstock and the nature of contaminants, desulfurization methods vary from ambient temperature-activated charcoal absorption to high-temperature catalytic hydrogenation followed by zinc oxide treating.

Health and Safety Considerations:

Fire Protection and Prevention - The potential exists for fire from a leak or release of feedstock c product. Sweetening processes use air or oxygen. If excess oxygen enters these processes, it is possible a fire to occur in the settler due to the generation of static electricity, which acts as the ignition source.

Health:

Because these are closed processes, exposures are expected to be minimal under normal operating conditions. There is a potential for exposure to hydrogen sulphide, caustic (sodium hydroxide), spent caustic, spent catalyst (Merox), catalyst dust and sweetening agents (sodium carbonate and sodium bicarbonate).

Safe work practices and/ or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat, and during process sampling, inspection, maintenance, and turnaround activities.

Health and Safety Considerations:

Blending - Blending is the physical mixture of a number of different liquid hydrocarbons to produce a finished product with certain desired characteristics. Products can be blended in-line through a manifold system, or batch blended in tanks and vessels. In-line blending of gasoline, distillates, jet fuel, and kerosene is accomplished by injecting proportionate amounts of each component into the main stream where turbulence promotes thorough mixing. Additives including octane enhancers, metal deactivators, anti-oxidants, anti-knock agents, gum and rust inhibitors, detergents, etc. are added during and/ or after blending to provide specific properties not inherent in hydrocarbons.

Health and Safety Considerations:

Fire Prevention and Protection - Ignition sources in the area need to be controlled in the event of a leak or release.

Health - Safe work practices and/ or appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as noise and heat; when handling additives; and during inspection, maintenance, and turnaround activities.

Other Refinery Operations:

Heat Exchangers, Coolers, and Process Heaters Heating Operations - Process heaters and heat exchangers preheat feedstock in distillation towers and in refinery processes to reaction temperatures. Heat exchangers use either steam or hot hydrocarbon transferred from some other section of the process for heat input. The heaters are usually designed for specific process operations, and most are of cylindrical vertical or box-type designs.

The major portion of heat provided to process units comes from fired heaters fuelled by refinery or natural gas, distillate, and residual oils. Fired heaters are found on crude and reformer pre-heaters, coker heaters, and large-column reboilers.

Cooling Operations - Heat also may be removed from some processes by air and water exchangers, fin fans, gas and liquid coolers, and overhead condensers, or by transferring heat to other systems. The basic mechanical vapour compression refrigeration system, which may serve one or more process units, includes an evaporator, compressor, condenser, controls, and piping. Common coolants are water, alcohol/water mixtures, or various glycol solutions.

Health and Safety Considerations:

Fire Protection and Prevention - A means of providing adequate draft or steam purging is required to reduce the chance of explosions when lighting fires in heater furnaces. Specific start-up and emergency procedures are required for each type of unit. If fire impinges on fin fans, failure could occur due to overheating. If flammable product escapes from a heat exchanger or cooler due to a leak, fire could occur.

Safety - Care must be taken to ensure that all pressure is removed from heater tubes before removing header or fitting plugs. Consideration should be given to providing for pressure relief in heat-exchanger piping systems in the event they are blocked off while full of liquid. If controls fail, variations of temperature and pressure could occur on either side of the heat exchanger.

If heat exchanger tubes fail and process pressure is greater than heater pressure, product could enter the heater with downstream consequences. If the process pressure is less than heater pressure, the heater stream could enter into the process fluid. If loss of circulation occurs in liquid or gas coolers, increased product temperature could affect downstream operations and require pressure relief.

Health:

Because these are closed systems, exposures under normal operating conditions are expected to be minimal. Depending on the fuel, process operation, and unit design, there is a potential for exposure to hydrogen sulphide, carbon monoxide, hydrocarbons, steam boiler feed-water sludge, and water-treatment chemicals.

Skin contact should be avoided with boiler blow-down, which may contain phenolic compounds. Safe work practices and! or appropriate personal protective equipment against hazards may be needed during process maintenance, inspection, and turnaround activities and for protection from radiant heat, superheated steam, hot hydrocarbon, and noise exposures.

Steam Generation:

Heater and Boiler Operations - Steam is generated in main generation plants, and or at various process units using heat from flue gas or other sources. Heaters (furnaces) include burners and a combustion air system, the boiler enclosure in which heat transfer takes place, a draft or pressure system to remove flue gas from the furnace, soot blowers, and compressed -air systems that seal openings to prevent the escape of flue gas. Boilers consist of a number of tubes that carry the water-steam mixture through the furnace for maximum heat transfer. These tubes run between steam-distribution drums at the top of the boiler and water-collecting drums at the bottom of the boiler. Steam flows from the steam drum to the super-heater before entering the steam distribution system.

Heater Fuel - Heaters may use anyone or combination of fuels including refinery gas, natural gas, fuel oil, and powdered coal. Refinery off-gas is collected from process units and combined with natural gas and LPG in a fuel-gas balance drum. The balance drum provides constant system pressure, fairly stable.

Btu-content fuel, and automatic separation of suspended liquids in gas vapours, and it prevents carryover of large slugs of condensate into the distribution system. Fuel oil is typically a mix of refinery crude oil with straight-run and cracked residues and other products. The fuel-oil system delivers fuel to process unit heaters and steam generators at required temperatures and pressures. The fuel oil is heated to pumping temperature, sucked through a coarse suction strainer, pumped to a temperature-control heater, and then pumped through a fine-mesh strainer before being burned.

In one example of process-unit heat generation, carbon monoxide boilers recover heat in catalytic cracking units as carbon monoxide in flue gas is burned to complete combustion. In other processes, waste-heat recovery units use heat from the flue gas to make steam.

Steam Distribution - The distribution system consists of valves, fittings, piping, and connections suitable for the pressure of the steam transported. Steam leaves the boilers at the highest pressure required by the process units or electrical generation. The steam pressure is then reduced in turbines that drive process pumps and compressors. Most steam used in the refinery is condensed to water in various types of heat exchangers.

The condensate is reused as boiler feedwater or discharged to wastewater treatment. When refiner; steam is also used to drive steam turbine generators to produce electricity, the steam must be produced a much higher pressure than required for process steam. Steam typically is generated by heaters (furnaces and boilers combined in one unit.

Feedwater - Feedwater supply is an important part of steam generation. There must always be as many pounds of water entering the system as there are pounds of steam leaving it. Water used in steam generation must be free of contaminants including minerals and dissolved impurities that can damage the system or affect its operation. Suspended materials such as silt, sewage, and oil, which form scale ant sludge, must be coagulated or filtered out of the water.

Dissolved gases, particularly carbon dioxide and oxygen, cause boiler corrosion and are removed by deaeration and treatment. Dissolved mineral including metallic salts, calcium, carbonates, etc., that cause scale, corrosion, and turbine blade deposit are treated with lime or soda ash to precipitate them from the water.

Re-circulated cooling water must also be treated for hydrocarbons and other contaminants. Depending on the characteristics of raw boiler feedwater, some or all of the following six stages of treatment will be applicable:

Clarification, Sedimentation and Filtration

Ion exchange, Deaeration and Internal treatment

Health and Safety Considerations:

Fire Protection and Prevention - The most potentially hazardous operation in steam generation is heater startup. A flammable mixture of gas and air can build up as a result of loss of flame at one or more burners during light off. Each type of unit requires specific startup and emergency procedures including purging before light off and in the event of misfire or loss of burner flame.

Safety - If feedwater runs low and boilers are dry, the tubes will overheat and fail. Conversely, excess water will be carried over into the steam distribution system and damage the turbines. Feedwater must be free of contaminants that could affect operations. Boilers should have continuous or intermittent blow-down systems to remove water from steam drums and limit buildup of scale on turbine blades and super heater tubes.

Care must be taken not to overheat the super heater during startup and shutdown. Alternate fuel sources should be provided in the event of loss of gas due to refinery unit shutdown or emergency. Knockout pots provided at process units remove liquids from fuel gas before burning.

Health:

Safe work practices and/or appropriate personal protective equipment may be needed for potential exposures to feedwater chemicals, steam, hot water, radiant heat, and noise, and during process sampling, inspection, maintenance, and turnaround activities.

Pressure-Relief and Flare Systems:

Pressure -Relief Systems - Pressure-relief systems control vapours and liquids that are released by pressure-relieving devices and blow-downs. Pressure relief is an automatic, planned release when operating pressure reaches a predetermined level, Blow -down normally refers to the intentional release of material, such as blow- downs from process unit startups, furnace blow-downs, shutdowns, and emergencies. Vapour depressuring is the rapid removal of vapours from pressure vessels in case of fire. This may be accomplished by the use of a rupture disc, usually set at a higher pressure than the relief valve.

Safety Relief Valve Operations - Safety relief valves, used for air, steam, and gas as well as for vapour and liquid, allow the valve to open in proportion to the increase in pressure over the normal operating pressure.

Safety valves designed primarily to release high volumes of steam usually pop open to full capacity. The overpressure needed to open liquid- relief valves where large- volume discharge is not required increases as the valve lifts due to increased spring resistance. Pilot-operated safety relief valves, with up to six times the capacity of normal relief valves, are used where tighter sealing and larger volume discharges are required. Non volatile liquids are usually pumped to oil-water separation and recovery systems, and volatile liquids are sent to units operating at a lower pressure.

Flare Systems - A typical closed pressure release and flare system includes relief valves and lines from process units for collection of discharges, knockout drums to separate vapours and liquids, seals, and/or purge gas for flashback protection, and a flare and igniters system which combusts vapours when discharging directly to the atmosphere is not permitted. Steam may be injected into the flare tip to reduce visible smoke.

Pressure Relief Health and Safety Considerations:

Fire Protection and Prevention - Vapours and gases must not discharge where sources of ignition could be present.

Safety - Liquids should not be discharged directly to a vapour disposal system. Flare knockout drums and flares need to be large enough to handle emergency blow-downs. Drums should be provided with relief in the event of over pressure.

Pressure relief valves must be provided where the potential exists for overpressure in refinery processes due to the following causes:

Loss of cooling water, which may greatly reduce pressure in condensers and increase the pressure in the process unit.

Loss of reflux volume, which may cause a pressure drop in condensers and a pressure rise in distillation towers because the quantity of reflux affects the volume of vapours leaving the distillation tower.

Failure of automatic controls, closed outlets, heat exchanger failure, etc.

Internal explosion, chemical reaction, thermal expansion, or accumulated gases.

Maintenance is important because valves are required to function properly. The most common operating problems are listed below.

Failure to open at set pressure, because of plugging of the valve inlet or outlet, or because corrosion prevents proper operation of the disc holder and guides.

Failure to reseat after popping open due to fouling, corrosion, or deposits on the seat or moving parts, or because solids in the gas stream have cut the valve disc.

Chattering and premature opening, because operating pressure is too close to the set point

Health:

Safe work practices and/ or appropriate personal protective equipment may be needed to protect against hazards during inspection, maintenance, and turnaround activities.

Wastewater Treatment - Wastewater treatment is used for process, runoff, and sewerage water prior to discharge or recycling. Wastewater typically contains hydrocarbons, dissolved materials, suspended solids, phenols, ammonia, sulphides, and other compounds. Wastewater includes condensed steam, stripping water, spent caustic solutions, cooling tower and boiler blow-down, wash water, alkaline and acid waste neutralization water, and other process-associated water.

Pre-treatment Operations - Pre-treatment is the separation of hydrocarbons and solids from wastewater. API separators, interceptor plates, and settling ponds remove suspended hydrocarbons, oily sludge, and solids by gravity separation, skimming, and filtration. Some oil-in-water emulsions must be heated first to assist in separating the oil and the water. Gravity separation depends on the specific gravity differences between water and immiscible oil globules, which allows free oil to be skimmed off the surface of the wastewater.

Acidic wastewater is neutralized using ammonia, lime, or soda ash. Alkaline wastewater is treated with sulphuric acid, hydrochloric acid, carbon dioxide-rich flue gas, or sulphur.

Secondary Treatment Operations - After pre-treatment, suspended solids are removed by sedimentation or air flotation. Wastewater with low levels of solids may be screened or filtered. Flocculation agents are sometimes added to help separation. Secondary treatment processes biologically degrade and oxidize soluble organic matter by the use of activated sludge, un-aerated or aerated lagoons, trickling filter methods, or anaerobic treatments.

Materials with high adsorption characteristics are used in fixed-bed filters or added to the wastewater to form slurry which is removed by sedimentation or filtration. Additional treatment methods are used tc remove oils and chemicals from wastewater. Stripping is used on wastewater containing sulphides and/or ammonia, and solvent extraction is used to remove phenols.

Tertiary Treatment Operations - Tertiary treatments remove specific pollutants to meet regulatory discharge requirements.

These treatments include chlorination, ozonation, ion exchange, reverse osmosis, activated carbon adsorption, etc. Compressed oxygen is diffused into wastewater streams to oxidize certain chemicals or to satisfy regulatory oxygen-content requirements. Wastewater that is to be recycled may require cooling to remove heat and/ or oxidation by spraying or air stripping to remove any remaining phenols, nitrates, and ammonia.

Health and Safety Considerations:

Fire Protection and Prevention - The potential for fire exists if vapours from wastewater containing hydrocarbons reach a source of ignition during treatment.

Health:

Safe work practices and/or appropriate personal protective equipment may be needed for exposures to (chemicals and waste products during process sampling, inspection, maintenance, and turn-around activities as well as to noise, gases, and heat.

Cooling Towers - Cooling towers remove heat from process water by evaporation and latent heat translate between hot water and air. The two types of towers are cross flow and counter flow. Cross flow towel introduce the airflow at right angles to the water flow throughout the structure. In counter flow cooling towers, hot process water is pumped to the uppermost plenum and allowed to fall through the tower.

Air enters at the tower bottom and flows upward against the water. When the fans or blowers are at tl air inlet, the air is considered to be forced draft. Induced draft is when the fans are at the air outlet.

Cooling Water - Re-circulated cooling water must be treated to remove impurities and dissolved hydrocarbons. Because the water is saturated with oxygen from being cooled with air, the chances for corrosion are increased. One means of corrosion prevention is the addition of a material to the cooling water that forms a protective film on pipes and other metal surfaces.

Health and Safety Considerations:

Fire Prevention and Protection - When cooling water is contaminated by hydrocarbons, flammable vapours can be evaporated into the discharge air. If a source of ignition is present, or if lightning occurs, a fire may start.

A potential fire hazard also exists where there are relatively dry areas in induced-draft cooling towers of combustible construction.

Safety - Loss of power to cooling tower fans or water pumps could have serious consequences in the operation of the refinery. Impurities in cooling water can corrode and foul pipes and heat exchangers, scale from dissolved salts can deposit on pipes, and wooden cooling towers can be damaged by microorganisms.

Health:

Cooling-tower water can be contaminated by process materials and by-products including sulphur dioxide, hydrogen sulphide, and carbon dioxide, with resultant exposures. Safe work practices and/ or appropriate personal protective equipment may be needed during process sampling, inspection, maintenance, and turnaround activities; and for exposure to hazards such as those related to noise, water-treatment chemicals, and hydrogen sulphide when wastewater is treated in conjunction with cooling towers.

Electric Power - Refineries may receive electricity from outside sources or produce their own power with generators driven by steam turbines or gas engines. Electrical substations receive power from the utility or power plant for distribution throughout the facility. They are usually located in non classified areas away from sources of vapour or cooling-tower water spray. Transformers, circuit breakers, and feed-circuit switches are usually located in substations. Substations feed power to distribution stations within the process unit areas.

Distribution stations can be located in classified areas, providing that classification requirements are met. Distribution stations usually have a liquid-filled transformer and an oil-filled or air-break disconnect device.

Health and Safety Considerations:

Fire Protection and Prevention - Generators that are not properly classified and are located too close to process units may be a source of ignition should a spill or release occurs.

Safety - Normal electrical safety precautions including dry footing, high-voltage warning signs, and guarding must be taken to protect against electrocution. Lockout/tagout and other appropriate safe work practices must be established to prevent energization while work is being performed on high-voltage electrical equipment.

Health:

Safe work practices and/or the use of appropriate personal protective equipment may be needed for exposures to noise, for exposure to hazards during inspection and maintenance activities, and when working around transformers and switches that may contain a dielectric fluid which requires special handling precautions.

Gas and Air Compressors - Both reciprocating and centrifugal compressors are used throughout the refinery for gas and compressed air. Air compressor systems include compressors, coolers, air receivers air dryers, controls, and distribution piping. Blowers are used to provide air to certain processes.

Health and Safety Considerations:

Fire Protection and Prevention - Air compressors should be located so that the suction does not take in flammable vapours or corrosive gases. There is a potential for fire should a leak occur in gas compressors.

Safety - Knockout drums are needed to prevent liquid surges from entering gas compressors. If gases are contaminated with solid materials, strainers are needed.

Failure of automatic compressor controls will affect processes. If maximum pressure could potentially be greater than compressor or process-equipment design pressure, pressure relief should be provided.

Guarding is needed for exposed moving parts on compressors. Compressor buildings should be properly electrically classified, and provisions should be made for proper ventilation.

Where plant air is used to back up instrument air, interconnections must be upstream of the instrument air drying system to prevent contamination of instruments with moisture. Alternate sources of instrument air supply, such as use of nitrogen, may be needed in the event of power outages or compressor failure.

Health:

Safe work practices and/or appropriate personal protective equipment may be needed for exposure to hazards such as noise and during inspection and maintenance activities. The use of appropriate safeguards must be considered so that plant and instrument air is not used for breathing or pressuring potable water systems.

Turbines - Turbines are usually gas-or steam-powered and are typically used to drive pumps, compressors, blowers, and other refinery process equipment. Steam enters turbines at high temperatures and pressures, expands across and drives rotating blades while directed by fixed blades.

Health and Safety Considerations:

Safety - Steam turbines used for exhaust operating under vacuum should have safety relief valves on the discharge side, both for protection and to maintain steam in the event of vacuum failure. Where maximum operating pressure could be greater than design pressure, steam turbines should be provided with relief devices. Consideration should be given to providing governors and over-speed control devices on turbines.

Health:

Safe work practices and/or appropriate personal protective equipment may be needed for noise, steam and heat exposures, and during inspection and maintenance activities.

Pumps, Piping and Valves - Centrifugal and positive-displacement (i.e., reciprocating) pumps are used to move hydrocarbons, process water, firewater, and wastewater through piping within the refinery. Pumps are driven by electric motors, steam turbines, or internal combustion engines. The pump type, capacity, and construction materials depend on the service for which it is used.

Process and utility piping distribute hydrocarbons, steam, water, and other products throughout the facility. Their size and construction depend on the type of service, pressure, temperature, and nature of the products. Vent, drain, and sample connections are provided on piping, as well as provisions for blanking.

Different types of valves are used depending on their operating purpose. These include gate valves, bypass valves, globe and ball valves, plug valves, block and bleed valves, and check valves. Valves can be manually or automatically operated.

Fire Protection and Prevention - The potential for fire exists should hydrocarbon pumps, valves, or lines develop leaks that could allow vapours to reach sources of ignition. Remote sensors, control valves, fire valves, and isolation valves should be used to limit the release of hydrocarbons at pump suction lines in the event of leakage and/ or fire.

Safety - Depending on the product and service, backflow prevention from the discharge line may be needed. The failure of automatic pump controls could cause a deviation in process pressure and temperature. Pumps operated with reduced or no flow can overheat and rupture. Pressure relief in the discharge piping should be provided where pumps can be over-pressured. Provisions may be made for pipeline expansion, movement, and temperature changes to avoid rupture. Valves and instruments that require servicing or other work should be accessible at grade level or from an operating platform. Operating vent and drain connections should be provided with double-block valves, a block valve and plug, or blind flange for protection against releases.

Health - Safe work practices and/or appropriate personal protective equipment may be needed for exposure to hazards such as those related to liquids and vapours when opening or draining pumps, valves, and/ or lines, and during product sampling, inspection, and maintenance activities.

Tank Storage - Atmospheric storage tanks and pressure storage tanks are used throughout the refinery for storage of crudes, intermediate hydrocarbons (during the process), and finished products. Tanks are also provided for firewater, process and treatment water, acids, additives, and other chemicals. The type, construction, capacity and location of tanks depend on their use and materials stored.

Fire Prevention and Protection - The potential for fire exists should hydrocarbon storage tanks be overfilled or develop leaks that allow vapours to escape and reach sources of ignition. Remote sensors, control valves, isolation valves, and fire valves may be provided at tanks for pump-out or closure in the event of a fire in the tank, or in the tank dike or storage area.

Safety- Tanks may be provided with automatic overflow control and alarm systems, or manual gauging and checking procedures may be established to control overfills.

Health - Safe work practices and/or appropriate personal protective equipment may be needed for exposure to hazards related to product sampling, manual gauging, inspection, and maintenance activities including confined-space entry where applicable.

Date: 2015-01-29; view: 831