Waste Treatment PDF

Waste Treatment During drilling and production activities, many wastes were generated that must be treated. The purpose of waste treatment is to lower the potential hazards associated with a waste by reducing its toxicity...

Waste Treatment During drilling and production activities, many wastes were generated that must be treated. The purpose of waste treatment is to lower the potential hazards associated with a waste by reducing its toxicity, minimizing its volume and altering its state so that it is suitable for a particular disposal option. Waste Treatment Methods Treatment of Water Treatment of Treatment of Treatment of Water Solids air emissions  Treatment of Water Removal of Removal of Removal of Removal of suspended dissolved suspended dissolved Neutralization HCs HCs solids solids Move to slide 1  Removal of suspended HCs Gravity Gas Chemical Biological Separation Flotation Coagulants Processes Heater Filtration Electric Filed Filtration Treaters Coalescence Separation Move to slide 2  Removal of dissolved HCs Adsorption Biological Ultraviolet Process Irradiation Oxidation Volatilization Precipitation Move to slide 2  Removal of Suspended Solids Gravity Separation Filtration Coagulation Move to slide 2  Removal of dissolved solids Ion Reverse Evaporation/ Biological Precipitation Exchange Osmosis Distillation Processes Move to slide 2  Treatment of Solids Removal of Removal of HCs Solidification Water Move to slide 1  Removal of Water Percolation Mechanical Evaporation Methods Move to slide 7  Removal of HCs Washing Biological Process Adsorption Solvent Extraction Heating Distillation/ Filtration Pyrolysis Incineration Move to slide 7  Treatment of Air Emissions Sulphur Nitrogen Hydrocarbons Particulates Oxides Oxides Move to slide 1  Removal of Water Phase Suspended HCs Oil droplet Suspensions of oil droplets in water (emulsion) can be difficult to separate because they can be stabilize by the interfacial energy between the oil Surfactant droplets and the continuous water phase. Emulsion is a form of mixture of two immiscible liquids in that one liquid is dispersed as fine droplets in the other. Interface between fine droplets and base liquid in emulsion is usually very activated and unstable. Therefore, the state of emulsion is unstable. The droplets in the emulsion easily get together forming larger droplets, and finally, two separated liquid phases are formed. To prevent such deterioration of the emulsion, a surfactant (emulsifier) having both hydrophilic and lipophilic characteristics is added in the liquids. The emulsifier added in the emulsion presents on the interface of the two liquid phases and stabilizes the droplets. (i) Gravity Separation Fig. Horizontal 3-phase separator  (i) Gravity Separation Basic Design Principles: Primary separation section – The primary separation section is situated at the inlet to the vessel and is designed to separate the fluids from any entrained gas. Secondary separation – The secondary separation section is designed to facilitate the separation of the liquid constituents into light and heavy phases according to their specific gravity. Typically oil comprises the light phase and water the heavy phase. Coalescing section – The coalescing section includes a vapour coalescer or mist extractor to remove liquid droplets from the gas. A wire mesh eliminator is often used for this purpose.  The first step in the removal of hydrocarbons from water is normally gravity separation. Through properly selected separator tanks with skimmers, most free oil and unstable oil emulsions can be separated from the water. Gravity separation is usually the simplest and most economical way to remove large quantities of free oil from water. The first stage of gravity separation is to pass the water through large tanks to allow the phases to separate. These tanks are commonly called free water knockouts, wash tanks, settling tanks, or gun barrels. The effectiveness of these tanks depends on droplet size and how long the water is in the tank.  Plate Separator : ✓Plate separators can be used to improve the separation of oil and water. These separators consists of a series of closely spaced parallel plates that allow oil droplets to adhere to the plates, coalesce and migrate along them. The closely spaced plates reduce the settling distance required to separate the oil droplets from the water. Plate separators are mechanically simple and require little maintenance. They are relatively large and are not effective for very small oil droplets. Plate separators can Fig. Parallel plate separator reduce oil concentrations to 2-25 mg/L, with an average of 15 mg/L and can remove oil droplets down to about 20-30 micrometer in diameter.  Hydrocarbon outlet Hydroclones: Inlet Swirl section Taper section Tail section Fig. Schematic of hydroclone Water outlet  Hydrocyclones can be used to further separate oil and water. A high velocity stream is injected tangentially into the conically-shaped Hydrocyclones, creating a vortex. The radial acceleration created in the hydroclone can be several orders of magnitude greater than that of gravity, and forces the more dense water to outer edge of the hydroclone and the less dense oil to the centre. The oil is then produced out of the one end of the hydroclone and the water out of the other. The effectiveness of hydroclones in separating oil and water depends on a large number of parameters, including oil droplet size, oil/water density difference, inlet water velocity, solution gas, solids and system geometry. Depending on the conditions, hydroclones can reduce oil concentrations to 10 ppm, but 30 ppm is more common average. Hydroclones for separating oil and water are limited to cases where the inlet pressure is sufficient to drive the flow. For low pressure operations, the fluid may need to be pumped into the hydroclone.  A progressive cavity pump with low shear has been found to be an effective way to increase the fluid pressure without shearing the oil into smaller drop sizes. The drop size is a critical parameter in the effectiveness of hydroclones in separating oil from water. A progressing cavity pump is a positive displacement pump employing a rotor and stator assembly to create temporary chambers to draw fluid into, which 'progress' through the pump resulting in the fluid being expelled through the discharge port. The rotor is a helical-shaped worm component which rotates within the stator. The stator is made from a flexible material and has one more 'worm thread' than the rotor. This allows for the both the rotation of the stator and the provision of a shifting space which forms the progressing cavity necessary for the fluid. A progressing cavity pump excels when handling highly viscous fluids (shear sensitive fluids) which are required to be moved long distances (discharge pressure up to 48 bar). They are commonly found in waste water applications for moving viscous slurry and sludge containing softer-type solids. A related way to enhance gravity separation is through a decanter centrifuge. In this device, the produced water enters the spinning centrifuge, where oil is separated from the water because of its lower density. Centrifuges differ from hydroclones in that the spinning is mechanically driven in a centrifuge, while it is induced by the inlet velocity of the water in a hydroclone. A centrifuge can also have internal plates to enhance separation, making it a spinning plate separator. Centrifuges can remove oil droplets down to about 2 micrometers in diameter. (ii) Heater Treaters  Oil and water can also be separated by heating the mixture. The higher temperature lowers the fluid viscosity of the mixture and alters the interfacial tension between the phases, allowing the oil and water to separate faster. 𝝁 Mobility of droplets Settling rate of droplets Rupture the film on droplets Droplet collision & favours coalescence due to expansion of droplets Difference in densities & further chances of water settling.  (iii) Gas flotation Fig. Hydraulic-type induced gas flotation unit Fig. Mechanical-type induced gas flotation unit  If gas bubbles are passed through an emulsion of oil-in-water, the oil droplets will attach to the bubbles and be carried to the top of the mixture where they can be easily removed. Air bubbles are normally pumped through the water, although the expansion of dissolved air is also used. Gas flotation is often added by the addition of chemical coagulants. Carbon dioxide has also been used as the flotation gas. Gas flotation, however, can create a foam that is difficult to break. Gas flotation system can reduce oil concentrations to 15-100 mg/L, with a typical average of 40 mg/L. Coagulation is a chemical process that involves neutralization of charge whereas flocculation is a physical process and doesn't involve neutralization of charge.  (iv) Filtration Filtered Water Out (Permeate) Support Membrane Emulsion Out Emulsion In (Waste) (Feed) Filtered Water Out (Permeate) Fig. Schematic of microfiltration capillary tube ✓ One way to remove oil droplets from water is to pass the water through water- wet filters or membranes. These filter media use capillary pressure to trap oil and prevent it from passing out of the filter. ✓ Advanced filtration processes include cross flow membranes such as microfiltration and ultrafiltration. ✓ These processes consists of a hydrophilic microfiltration membrane that passes water (and dissolved material), but not oil droplets. The shape of the filter is typically a small diameter capillary tube that the emulsion flows through. The emulsion leaving the tube without passing through the filter can be recycled through the filter a number of times to further concentrate the emulsion for other types of treatment or disposal. ✓ Microfiltration processes are usually ineffective for hydrocarbon removal, however because the filters and membranes foul easily by oil and have short useful lifetimes.  (v)Filtration Coalescence ❖Another type of filtration is to pass the water through oil wet filters. The oil droplets attach to the filter matrix and coalesce into larger ones. When the filter medium has become saturated, larger oil drops will flow out of the filter, either by continued injection or back washing. These larger droplets can be more easily removed from the water by subsequent gravity separation. Sand, gravel or glass fibre are common media used for this process. Coalescing media fibre Oil droplets  (vi) Chemical Coagulants The removal of small, suspended oil droplets can be added by adding chemicals that coagulate and flocculate the droplets. These chemicals typically overcome the electrostatic repulsion charges on the individual droplets, allowing them to coagulate into larger drops. These larger drops can then be more efficiently removed with gravity separation equipment. Common chemicals used include lime, alum and polyelectrolytes. The use of dithiocarbamate has also been reported. Ultrasound Oil Sands Process- affected Water  (vii) Electric Field Separation ✓ Another way to separate oil from water is by applying an electric field (voltage) to the water to electrostatically remove the oil. ✓ These fields can be applied through either a direct or an alternating current. Oil droplets in an oil-in-water emulsion have a negative surface charge that can be manipulated to felicitate their removal. ✓ When the direct current is applied to the water containing such an emulsion, the oil will migrate towards the positive electrode. The migration velocity of the drops in many systems is in the order of 1 mm/min, which requires separators using very narrowly spaced parallel plates. This process, however, can only be used with saline water. ✓ When an alternating current is applied, the droplets may flocculate if a metal hydroxide is present. This process is known as alternating current electrocoagulation. In this process, a metal hydroxide is added to the water and an alternating current is used to overcome the electrostatic repulsion charges on the particles, when the electrostatic repulsion charges have been neutralized, the particles can flocculate and be more easily separated from the water by other methods. Iron and aluminium hydroxide have been successfully used.  (viii) Biological Process Biological process rely on bacterial degradation of hydrocarbons. They have limited application in the removal of free hydrocarbons from most waste water stream in the petroleum industry because they are too slow and are not appropriate for high oil concentrations. Large quantities of free oil can limit mass transfer of oxygen and nutrients to bacterial colonies that degrade the hydrocarbons. Biodegradation is the naturally-occurring breakdown of materials by microorganisms such as bacteria and fungi or other biological activity.  Bacteria, Archaea, Fungi &Algae Microorganism Nitrogen, Phosphorous, Oxygen, Nitrate & Sulphates HC Biodegradation Environmental Hydrocarbon conditions properties Removal of dissolved HCs (i) Adsorption  Adsorption PHYSICAL ADSORPTION CHEMISORPTIONS 1. The forces operating in these are The forces operating in these cases are weak vander Waal’s forces. similar to those of a chemical bond. 2. The heat of adsorption are low i.e. The heat of adsorption are high i.e. about 20 – 40 kJ mol-1 about 40 – 400 kJ mol-1 3. No compound formation takes place in Surface compounds are formed. these cases. 4. The process is reversible i.e. desorption The process is irreversible. Efforts to of the gas occurs by increasing the free the adsorbed gas give some temperature or decreasing the pressure. definite compound. 5. It does not require any activation It requires any activation energy. energy.  PHYSICAL ADSORPTION CHEMISORPTIONS This type of adsorption first increases with 6. This type of adsorption decreases with increase of temperature. The effect is called increase of temperature. activated adsorption. It is specific in nature and occurs only 7. It is not specific in nature i.e. all gases when there is some possibility of are adsorbed on all solids to some extent. compound formation between the gas being adsorbed and the solid adsorbent. 8. The amount of the gas adsorbed is related to the ease of liquefaction of the There is no such correlation exists. gas. 9. It forms multimolecular layer. It forms unimolecular layer. ✓ An effective way to remove low levels of dissolved hydrocarbons is to adsorb it onto a solid medium. The most widely used medium is activated carbon. ✓ The pH and the temperature of the system impacts the effectiveness of activated carbon on removing different hydrocarbon compounds. ✓ All free oil must be removed prior to the use of activated carbon to prevent the oil from clogging the carbon. In some cases coal may be used as an adsorption media. ✓ Natural and synthetic resin have also been developed that have proven effective in removing dissolved hydrocarbons from water. Activated carbon: Activated carbon is a form of carbon that is activated by a carefully controlled oxidation process to develop a porous carbon structure. The imperfect structure results in a high degree of porosity and over a broad range of pore sizes, from visible cracks and crevices to gaps and voids of molecular dimensions. The specified structure of carbon gives it a very large surface area which allows the carbon to adsorb a wide range of compounds. Activated carbon has the highest volume of adsorbing porosity of any material available to mankind. 5 gms of activated carbon = surface area of a football field Powder Activated Carbon (PAC): pulverised carbon with a size predominantly less than 0.180 mm (US Mesh 80). These are mainly used in liquid phase applications and for flue gas treatment. Granular Activated Carbon (GAC): irregular shaped particles with sizes ranging from 0.2 to 5 mm. This type is used in both liquid and gas phase applications. Extruded Activated Carbon (EAC): extruded and cylindrical shaped with diameters from 0.8 to 5 mm. These are mainly used for gas phase applications because of their low pressure drop, high mechanical strength and low dust content. Micropores ( < 2 nm diameter) Mesopores (2-50 nm diameter) Macropores (> 50 nm diameter)  (ii) Volatilization VOCs (Volatile Organic Compounds): High vapor pressure, low to medium water solubility, low molecular weight. ❖ Volatilization can be defined as the loss of liquid chemicals into the atmosphere as a vapor. In other words, volatilization is the combined effect of "vaporization" and "diffusion"; liquid-phase chemical changes into vapor-phase by vaporization and vapor-phase chemical moves into atmosphere by diffusion. Volatilization rates of organic chemicals from non-adsorbing surface are directly proportional to their relative vapor pressures. ❖Volatilization moves pollutants into the vapor phase and depends mostly onto the intermolecular forces holding a liquid together and the temperature; a substance volatilize when its thermal energy is high enough to overcome attractive forces within the substance. At the liquid-air interface, volatilization transfers volatile contaminants from water surfaces into the atmosphere. It is the most important for compounds with high vapor pressure.  A variety of methods can be used to volatilize VOCs, one of them is Air Stripping. In this process, air and water are passed through a containment vessel in counter current flow where VOCs evaporate into the air. After the contaminated water enters the column, it flows down the column and through the packing counter current to the air stream. The packing serves to increase the amount of contact between the two streams, and enhances the stripping as a result. After leaving the column the air is either distributed into the atmosphere, or is collected for purification. Fig. Packed tower Air Stripper  The removal of VOCs can be enhanced by heating the air or by using steam, because higher temperatures increase their vapor pressure. Volatilization can also be enhanced by pulling a vacuum on the water, lowering the total system pressure. One limitations to volatilization is that it transfers the VOCs from water to a vapor phase, yielding a contaminated vapor stream that must then be handled. If air is used, the oxygen will dissolve into the water, enhancing any biological degradation of dissolved hydrocarbons remaining in solution.  (iii) Biological Process ✓ Biological treatment can be used to remove low levels of dissolved hydrocarbons from wastewater streams. ✓ Biological treatments consists of mixing oxygen and nutrients with the water in a tank. The bacteria then degrade the organic compounds. ✓ This process is widely used in municipal water treatment plants, but may be too slow for oil field applications. Because the high salinity of produced water inhibits biological growth, biological treatment will not be effective in most cases. ✓ Another limiting factor is the lack of dissolved oxygen for bacteria. Although oxygen could be added, it would significantly increase the corrosion rate of the equipment.  (iv) Precipitation The solubility of many organic molecules decreases as pH decreases. By lowering the pH, some organic materials can be precipitated. Precipitation, however, will not remove all dissolved hydrocarbons and will acidify the water. (v) Ultraviolet Irradiation In this process, high-energy, short-wavelength photons are used to break the chemical bonds of dissolved hydrocarbons. When combined with heating to high temperatures, e.g., by solar collection panels, virtually complete destruction of hazardous hydrocarbon molecules in water has been observed. This method may have potential for treating some hazardous chemicals, but is probably too expensive for treating oilfield waters.  (vi) Oxidation Dissolved hydrocarbons can also be destroyed through oxidation. Ozone, peroxide, chlorine or permanganate have been tested. To be effective, however, oxidation normally must be conducted at high temperature or with ultraviolet irradiation. Oxidation is not practical for most oilfield applications.  Removal of suspended solids During many drilling and production activities, solids will be suspended in water that must be removed prior to water disposal. These solids include cuttings generated during drilling and sand & clay particles produced during oil production. (i) Gravity Separation The simplest way to separate the larger solid particles is to use gravitational settling. Fluids can be discharged into pits or tanks, where the solids settle to the bottom. Gravitational settling, however is not effective for very small particles. The use of settling pits may also be limited by environmental regulations and the potential for future liability. Centrifuges can be used for enhanced gravitational separation.  (ii) Filtration Another way to remove suspended solids is to filter the water. The water passes through the filter, while the solids are retained. The resulting filter cakes may be non-hazardous and could be disposed of like pit bottom sludge. (iii) Coagulation ✓ An effective way to enhance the separation of suspended particles is to coagulate (flocculate) the particles into larger agglomerations. The larger agglomerations can then be separated more easily by gravitational settling, configuration, or filtration. ✓ One successful way to coagulate suspended solids is to add chemicals that overcome to electrostatic repulsive charges on the solids to allow them to flocculate. ✓ Chemicals that can be used include calcium chloride, ferric chloride, or aluminium potassium sulphate. ✓ A high molecular weight polyacrylamide polymer has been found to be effective to flocculate solids in water based drilling muds, and a non-ionic polyethylene oxide with a high molecular weight non-ionic polyacrylamide polymer has been found to be affective for oil- based muds. ✓ Suspended solids can also be flocculated with alternating current electrocoagulation. In this process, a metal hydroxide is added to the water and an alternating current is used to overcome the electrostatic repulsion charges on the particles. Iron and aluminium hydroxide have been successfully used.  Removal of Dissolved Solids Most waste water also contains dissolved solids, particularly salt, hardness ions (calcium and magnesium), and heavy metals. (i) Ion Exchange Ion exchange (water softening) is an effective way to remove hardness ions from water. In most cases, the hardness ions (calcium and magnesium) are replaced with sodium ions. The removal of hardness ions is necessary for many processes because these ions readily precipitate and form a hard scale that can foul equipment. In some cases, the water can simply be passed through a bed of clay particles. The cation exchange capacity of most clays is very high, which allows them to trap and retain relatively high concentrations of dissolved metals. Activated alumina filtration is also an effective ion exchange media for metals like lead, mercury and silver.  Ion exchange resins (substrates) Strong acid resins (using sulfonic acid) Weak acid resins (using carboxylic acid) Strong acid resins can be generated simply Weak acid resins, however, must be by flushing with a concentrated solution generated by flushing with a strong acid like of sodium chloride. hydrochloric or sulfuric and then neutralizing with sodium hydroxide (ii) Precipitation Many dissolved solids precipitate from water to form scale as the temperature, pressure and/or chemistry changes. The most widely used system for precipitation is to add lime (Ca(OH)2) or sodium hydroxide (NaOH) to increase the pH of the water. At high pHs, dissolved solids, including heavy metals, tend to precipitate as a hydroxide sludge. Lime plus sodium carbonate can also be used to enhance the precipitation of calcium carbonate. Precipitation of Metal Hydroxide as a function of pH Metal pH Al3+ 4.1 Cd2+ 6.7 Co2+ 6.9 Cr3+ 5.3 Cu2+ 5.3 Fe2+ 5.5 Fe3+ 2.0 Hg2+ 7.3 Mn2+ 8.5 Ni2+ 6.7 Pb2+ 6.0 Zn2+ 6.7  (iii) Reverse Osmosis A process by which a solvent passes through a porous membrane in the direction opposite to that for natural osmosis when subjected to a hydrostatic pressure greater than the osmotic pressure. The most common way to totally remove all dissolved solids from water is through filtration process like reverse osmosis. Reverse osmosis is commonly used to provide drinking water from sea water in desalination plants. During reverse osmosis saline water is pumped through a very small pore filter. The water molecules pass through the filter, but the larger dissolved solids molecules do not. ✓Fouling is the most difficult problem to overcome when using reverse osmosis on oilfield brines. ✓Pre-treatment of the water prior to entering the reverse osmosis facility is required. ✓Because of its high cost, reverse osmosis is most commonly used to provide a supply of pure water in arid areas, rather than as a treatment method for waste water. ✓However, in areas where high quality water is scarce, reverse osmosis can be used to treat produced water.  (iv) Evaporation/Distillation ✓ Another way to obtain potable water from water impurities is to evaporate and condensed the water. ✓ Like reverse osmosis , this process is primarily used to provide a stream of pure water, not to treat a stream of wastewater. ✓ Like reverse osmosis, this process concentrates the wastes, which results in a smaller waste volume that ultimately must be disposed. ✓ This process is also very expensive. (v) Biological Process ✓ Although biological processes cannot destroy dissolved solids, they can alter their chemical form. ✓ For example , biological process can alter the availability of heavy metals for uptake by plants, as well as the ability of metals to leach through the soil. ✓ Bacterial remediation has also been successfully used to remove sulphides from produced water.  Neutralization ❖Many aqueous wastes in the petroleum industry are either acidic or alkaline. These wastes often must be treated to neutralize their activity before reuse or disposal. ❖ In many cases, the simplest treatment method is to mix these types of wastes for mutual neutralization. ❖Because mixing may result in an exothermic reaction, it must be done with care to minimize any safety hazards.  Treatment of Solids During drilling and production activities, a substantial volume of contaminated cuttings, soil and produced solids are generated. The most common treatment method is to separate the solids from any contaminating water and hydrocarbons.  Removal of Water (i) Evaporation ✓ The simplest way to dewater solid wastes in arid climates is to put them in open pits or on concrete pads and allow the free water to evaporate. Evaporation is a common way to remove water from reserve pits following drilling, although changes in regulations may now require a more rapid dewatering than evaporation allows. ✓ In most cases, no special attempt has been made to limit leaching of metals or hydrocarbons from reserve pits or evaporation ponds. ✓ If leaching is a problem, the pit can be constructed with an impermeable liner and a leachate collection system with monitoring wells and enhanced evaporation features.  (ii) Percolation ✓ In some arid areas where the water table is very deep, aqueous wastes can be placed in percolation pond. ✓ These ponds have permeable sides and bottoms, allowing the water to percolate into the surrounding soil, leaving the solids at the bottom of the pond. ✓ The use of these ponds is highly restricted, however because they allow dissolved solids in the water to spread into the surrounding soil.  (iii) Mechanical Methods ✓ In many cases, evaporation is too slow to remove water from solid wastes. A number of mechanical methods are available to dewater solids. ✓ Preliminary separation of free liquids from the solids should be made with shale shaker, settling ponds and Hydrocyclones. ✓ To further reduce the free water content of sludges, more advanced (and expensive) technologies can be used. These technologies include high-pressure filter presses, centrifuges and vacuum filtering. Fig. Rotary Vacuum-drum filter  Removal of Hydrocarbons (i) Washing One of the least expensive ways to remove most of the hydrocarbons from solid is to wash them. The solid can be entrained in a fluidized bed of upward flowing, high velocity water. This stream agitates the solids and opens the pore system to release the oil. The efficiency of this process can be enhanced by adding a surfactant (soap) to the water to lower the interfacial tension holding the oil to the solids. Water Solid Water Solid Solid Particle Water Distributor  (ii) Adsorption ✓ Another relatively low-cost method of removing some of the hydrocarbons containing solids is to mix the soil with a material that is strongly oil-wet like coal or activated carbon. ✓ A suspension of contaminated soil and the carbon can be tumbled in water at elevated temperatures to allow the oil to be absorbed by the carbon. ✓ The oily carbon is then separated from the water and clean sand by flotation. ✓ The oily carbon can then be burned in conventional coal-fired power plants or buried in an approved facility.  (iii) Heating Heating cuttings contaminated with hydrocarbons can help separate the hydrocarbons from the solids, particularly when being washed in water. This procedure is similar to using heat to break emulsion and separate hydrocarbons and water. (iv) Distillation/ Pyrolysis A liquid is boiled and the vapors progress through the apparatus until they reach the Thermochemical decomposition of condenser where they are cooled and organic material at elevated temperatures reliquify. Liquids are separated based upon in the absence of oxygen. their differences in boiling point. A more expensive method for removing light and intermediate weight hydrocarbon compounds is to distill them from the solids in a retort furnace. The solid/ hydrocarbon mixture is heated to vaporize the light and medium molecular weight hydrocarbons and water. The gases are removed from the high-temperature chamber by either a nitrogen or steam sweep. After the vapors are subsequently cooled and condensed, the oil is separated from the water. The oil can be reused and the solids and water sent to an appropriate disposal facility. To maximize the separation of liquids and solids, the heating can be done in a rotating drum with hammers to crush the solids while rotating.  Limitations of Distillation systems: ✓ Hydrocarbon vapors at high temperature are a fire hazard. ✓ Corrosion problems increase significantly at high temperatures. ✓ Air pollutants are emitted. ✓ If heavy hydrocarbon components are present, they will not be distilled and will form a heavy residual tar on the solids. For example, distillation may remove only about 65% of the heavy polynuclear aromatics. ✓ Distillation is the high energy costs of heating the materials to a sufficiently high temperature. An operating temperature of about 800℉ may be required for effective distillation of heavy ends. An operating temperature of 473℉, however, has proven to be effective in lowering the hydrocarbon level of cuttings to 10 g/kg. If the distillation temperatures are high enough, the hydrocarbon molecules will be broken by pyrolysis, forming coke. This would solidify the remaining HCs, preventing their migration upon disposal of the waste.  (v) Incineration Another way to remove HCs from solids is to burn the mixture in an incinerator. Incinerators are specially designed burner that can burn the relatively small volume of combustible materials found in oily solids. Following combustion, the resulting ash, including any salts and heavy metals, is solidified to prevent leaching of any hazardous residue. Incineration typically removes over 99% of the hydrocarbons in the soil.  Limitations of Incinerators: ✓They emit air pollutants, particularly metal compounds like barium, cadmium, chromium, copper, lead, mercury, nickel, vanadium and zinc. ✓Incineration destroys hydrocarbon wastes, but merely changes the chemical form of heavy metal wastes. ✓Because of the air pollutants emitted, all incinerators require permits. ✓Another limitation to incineration is that a secondary fuel is required because the heat content of the hydrocarbon in many petroleum solid wastes is insufficient for combustion, particularly when a high volume of non-combustible material is present e.g., the solids. ✓The need for secondary fuel increases as the cost of operations. Although incineration is expensive, it has low future liability.  (vi) Solvent Extraction Solvent Extraction processes can also be used to separate hydrocarbons from solids. In this processes, a solvent with a low boiling point is mixed with the oily solids to wash the oil from the solids and dilute what remain trapped. The solvent is then separated from the hydrocarbons and solids by low-temperature distillation and reused. Solvent extraction is routinely used in the petroleum industry for extracting fluids from core during core analysis. Like distillation, solvent extraction is expensive. Solvent extraction is more effective in sandy soils containing little clay. A more exotic solvent extraction processes uses critical or super-critical fluids. In this process the cuttings are placed in a pressure chamber with a fluid near its critical point. Commonly used fluids include carbon dioxide, propane, ethane and butane. The pressure is increased until the fluid passes above its critical point and becomes a liquid. The liquid is then used as a solvent to wash the oil from the solids. After the liquid mixture is separated from the solids, the pressure is lowered. With the lower pressure, the supercritical fluid reverts to a gaseous state, leaving the extracted hydrocarbons behind. The gas is then recycled. The process is expensive, but eliminates many of the problems associated with high- temperature thermal processes. Triple Point: The triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium. It is that temperature and pressure at which the sublimation curve, fusion curve and the vaporisation curve meet. For example, the triple point of mercury occurs at a temperature of −38.8 °C (−37.9°F) and a pressure of 0.2 mPa. Super Critical fluids: Any substance is characterized by a critical point which is obtained at specific conditions of pressure and temperature. When a compound is subjected to a pressure and a temperature higher than its critical Critical Point: critical point (or critical state) is point, the fluid is said to be "supercritical". the end point of a phase equilibrium curve. The In the supercritical region, the fluid exhibits particular most prominent example is the liquid-vapor properties and has an intermediate behavior between that critical point, the end point of the pressure- of a liquid and a gas. In particular, supercritical fluids temperature curve that designates conditions under (SCFs) possess liquid-like densities, gas-like viscosities, which a liquid and its vapor can coexist. At higher and diffusivity intermediate to that of a liquid and a gas. temperatures, the gas cannot be liquefied by The fluid is said "supercritical" when it is heated above pressure alone. At the critical point, defined by a its critical temperature and compressed above its critical critical temperature Tc and a critical pressure pc, pressure phase boundaries vanish.  (vii) Biological Process Most hydrocarbons encountered in the upstream petroleum industry can be biological converted to carbon dioxide and water by microbes like bacteria and fungi. During biological degradation, the hydrocarbon are eaten as by the bacteria. This biological degradation can be enhanced by providing the optimum conditions for microbe growth. The deliberate enhancement of biological degradation is called bioremediation. The effectiveness and speed of bioremediation in degrading hydrocarbons depends on a variety of environmental conditions, including temperature, salinity, pH, hydrocarbon type, heavy metal concentration, soil texture, moisture content, and hydrocarbon concentration. Because of this, the chemical composition of the hydrocarbon, the type and level of background microorganism, and the nutrient level at the site must be determined and the environmental conditions controlled for optimum degradation. In most cases, the appropriate bacteria are already present in the environment and their populations can be increased just by adding nutrients. In some cases, naturally occurring bacteria have been artificially cultured and then released in greater numbers to accelerate biodegradation of the hydrocarbons, but the effectiveness of this augmentation is uncertain. The most significant limitation for many bioremediation applications is a lack of nutrients for bacterial growth. These nutrients, e.g., nitrogen, phosphorus, and some trace elements, can be added by way of fertilizer. Oxygen is also needed for bioremediation to convert the hydrocarbons to carbon dioxide and water. Anaerobic biological degradation (without oxygen) also occurs, but is much slower and less efficient than aerobic degradation. Oxygen is normally provided by ensuring that the pore system within the solids is sufficiently open for air to allow through it. One way to enhance the pore system is by adding inert bulking agents like wood chips, bark, sawdust, tires and shredded vegetation to increase the mixture porosity. The use of inert bulking agents is called composting bioremediation. In most cases, water is also needed because it is the medium in which the bacteria live. Bacterial growth normally occurs at water/ hydrocarbon interfaces. For optimum degradation, the water content of the solids must be balanced. If not enough water is present, bacterial growth will be inhibited. If too much water is present, the access of oxygen and nutrients to the bacteria will be limited, again inhibiting bacterial growth. Paraffins are the most susceptible to microbial attack, followed by isoparaffin and aromatics. The polycyclic aromatic hydrocarbons (PAHs) are the most difficult to biodegrade.  (viii) Filtration If the hydrocarbon content of the solids is high, some of the free hydrocarbons can be separated from the solids by mechanical filtration. Filtration, however, is not effective for reducing hydrocarbon concentrations to low levels. Solidification One way to treat contaminated solids is to solidify the mixture so that the contaminants become part of the solid. Solidification reduces pollutant mobility and improve handling characteristics.  Adding materials to absorb free liquids Two types of solidification have been used: Adding materials to chemically bind and encapsulate the contaminants Absorbents are typically used to dewater reserves pits in area where the evaporation rate is low. Materials that have been added to the pits to absorb free water include straw, dirt, fly ash, clays, kiln dust and polymer. The best solidification methods, however, are those that chemically bind the contaminants. These methods are based primarily on Portland cement, calcium silicate, or alumina-silicate reactions. These materials unlike fly ash or kiln dust, can reduce the leachability of toxic heavy metals, asbestos, oils and salts. The mobility of metals from such solidification can be reduced by 80-90%, while that of organics can be reduced by 60-99%.  Treatment of Air Emissions The vapour space in production tanks: These vapors can be collected and treated with vapor S recovery systems. O Casing gas from thermal enhanced oil recovery (i) Hydrocarbons U operations: These gases can be collected in a separate gathering system and treated by adsorption. R Exhaust of Internal Combustion Engines: C Unfortunately, there is little that can be done to treat these emissions other than to operate the E engines within their design specifications. S  Fugitive emissions arising from leaking valves and fittings: Because these emissions are generally too spread out to be collected, their release must be prevented by replacing and repairing the leaking equipment. S O U Emissions from remediation projects of hydrocarbon contaminated sites (volatile HCs): These HCs can be collected by passing the emissions through a bed of activated carbon R or adsorptive polymer. Alternatively, the vapors can be bubbled through water, where the HCs become dissolved. Although the dissolution process can be effective in C lowering HC air emissions, the subsequently contaminated water must then be treated and disposed. For some projects, catalytic oxidation may be used as low temperature E alternative to incineration of volatile HCs. S  (ii) Sulphur oxides Sulphur oxides are generated from the combustion of fuels contain in sulphur. Although these emissions can be treated to remove the sulphur, the emission of sulphur can also be reduced or eliminated by use of low-sulphur fuel. A variety of scrubber systems are available to remove sulphur from air emissions. SO2 Scrubbers: SO2 scrubber system is the informal name of flue gas desulfurization (FGD) technology, which removes, or ‘scrubs’ SO2 emission from the exhaust of coal-fired power plants. A scrubber works by spraying a wet slurry of lime stone into a large chamber where the calcium in the lime stone reacts with the SO2 in the flue gas. Some scrubbers may use other chemicals such as lime or magnesium oxide to react with the SO2 in the flue gas.  Once sulphur is burned and produces SO2, the exhaust gas passes through the scrubber where a spray mixture of lime stone and water reacts with the SO2. The reaction enables the SO2 to be removed before its released into the atmosphere. CaCO3 CaO + CO2 (g) 𝟏 CaO + SO2 (g) + O2 (g) CaSO4 𝟐 Used in manufacturing of wallboard & cement Synthetic As a soil amendment in agriculture Gypsum Construction applications Duke’s Energy’s newer scrubbers are typically designed to remove 95% or more of the SO2 from the exhaust gas. The white plume that comes out of the stack is water vapor.  (iii) Nitrogen Oxides Nitrogen oxides are generated from high-temperature combustion and from the combustion of fuels containing nitrogen (crude oil). Unfortunately, these emissions are difficult to treat and may require specially designed equipment. Equipment to minimize the emission of nitrogen oxide in combustion gases include low NOx burners, flue gas circulators, selective catalytic reduction devices, and selective noncatalytic systems. The amount of nitrogen oxides emitted can also be lowered by reducing the amount of oxygen in the combustion process. Unfortunately lowering oxygen in the combustion process increases the amount of partially burned hydrocarbons created. The impact of nitrogen oxide from fixed installations, such as natural gas compressor stations can be minimized by stack height, location and orientation with respect to other structures. (iv) Particulates Many combustion operations emit partially burned hydrocarbon particulates from incomplete combustion. These particulates, such as soot can be removed by passing the flue gas through a scrubber, where the particulates become entrained in the water.  Bharat stage emission standards Bharat stage emission standards (BSES) are emission standards instituted by the Government of India to regulate the output of air pollutants from compression ignition engines and Spark-ignition engines equipment, including motor vehicles. The standards and the timeline for implementation are set by the Central Pollution Control Board under the Ministry of Environment, Forest and Climate Change. Indian emission standards (4-wheeled vehicles) Standard Reference Year Region India 2000 Euro 1 2000 Nationwide NCR, Mumbai, 2001 Kolkata, Chennai Bharat Stage II Euro 2 2003 NCR, 13 Cities 2005 Nationwide 2005-04 NCR, 13 Cities Bharat Stage III Euro 3 2010 Nationwide 2010 NCR, 13 Cities† Bharat Stage IV Euro 4 2017 Nationwide Bharat Stage V Euro 5 (To be skipped) Bharat Stage VI Euro 6 2018 Delhi 2019 NCR 2020 Nationwide  Difference Between BS4 (BSIV) and BS6 (BSVI) Fuel Type Pollutant Gases BS6 (BSVI) BS4 (BSIV) Nitrogen Oxide (NOx) Maximum 60 mg/km 80 mg/km Petrol Passenger Permissible Limit Vehicle Particulate Matter 4.5mg/km - (PM) Limit Nitrogen Oxide (NOx) Maximum 80 mg/km 250 mg/km Diesel Passenger Permissible Limit Vehicle Particulate Matter 4.5 mg/km 25 mg/km (PM) Limit HC + NOx 170mg/km Indian Diesel Specification BSII BSIII BSIV BSV BSVI Sulphur 500 350 50 10 10 content (mg/kg)