Overview of pollution from refineries


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Overview of pollution from refineries

  1. 1. Refineries Emit a Wide Variety of Pollutants
  2. 2. ► Criteria Air Pollutants (CAP) ► Sulfur dioxide SO2 ► Oxides of Nitrogen NOX ► Carbon Monoxide CO ► Particulate Matter (PM) ► Volatile Organic Compounds (VOC) ► Organic compounds that are photochemically reactive
  3. 3. ► Hazardous Air Pollutants (HAP) ► Carcinogenic HAP, including benzene, naphthalene,1,3-butadiene, Polycyclic aromatic hydrocarbons (PAH) ► Non-carcinogenic HAP, including Hydrogen Fluoride (HF) and Hydrogen Cyanide (HCN) ► Persistent bio-accumulative HAP, including mercury ► Other Pollutants ► Greenhouse Gases (GHG) ► Hydrogen Sulfide (H2S)
  4. 4. Properties of air pollutants 1-Particulate Matter 2-Nitrogen Oxides 3-Sulfur Oxides 4-Carbon monoxide (CO) 5-Ground-Level Ozone 6-Hydrocarbons
  5. 5. 1-Particulate Matter: Airborne particulate matter, which includes dust, dirt, soot, smoke, and liquid droplets emitted into the air, is small enough to be suspended in the Atmosphere. Airborne particulates may be a complex mixture of organic and inorganic substances.
  6. 6.  They can be characterized by their physical attributes,which influence their transport and deposition, and their chemical composition, which influences their effect on health.  The physical attributes of airborne particulates include mass concentration and size distribution.  Ambient levels of mass concentration are measured in micrograms per cubic meter (μg/m3).  Particulate matter (PM) exceeding 2.5 microns (μm is generally defined as coarse particles, while particles smaller than 2.5 microns (PM2.5) are called fine particles.
  7. 7. Sources of Particulates:  Some particulates come from natural sources such as evaporated sea spray, windborne pollen, dust, and volcanic or other geothermal eruptions. Particulates from natural sources tend to be coarse.  Almost all fine particulates are generated as a result of combustion processes, including the burning of fossil fuels for steam generation, heating and household cooking, agricultural field burning, diesel- fueled engine combustion, and various industrial processes.  The largest stationary sources of particulate emissions include fossil-fuel-based thermal power plants, metallurgical processes, and cement manufacturing.
  8. 8. 2- Nitrogen Oxides:  Nitrogen oxides (NOx) in the ambient air consist primarily of nitric oxide (NO) and nitrogen dioxide (NO2). These two forms of gaseous nitrogen oxides are significant pollutants of the lower atmosphere. Another form, nitrous oxide (N2O), is a greenhouse gas.  nitric oxide, a colorless, tasteless gas, is the predominant form of nitrogen oxide. Nitric oxide is readily converted to the much more harmful nitrogen dioxide by chemical reaction with ozone present in the atmosphere. Nitrogen dioxide is a yellowish-orange to reddish-brown gas with a pungent, irritating odor, and it is a strong oxidant. A portion of nitrogen dioxide in the atmosphere is converted to nitric acid (HNO3) and ammonium salts.
  9. 9. Major Sources:  Only about 10% of all NOx emissions come from anthropogenic sources (Godish 1991). The rest is produced naturally by anaerobic biological processes in soil and water, by lightning and volcanic activity, and by photochemical destruction of nitrogen compounds in the upper atmosphere. About 50% of emissions from anthropogenic sources comes from fossil-fuel- fired heat and electricity generating plants and slightly less from motor vehicles.
  10. 10.  Other sources include industrial boilers, incinerators, the manufacture of nitric acid and other nitrogenous chemicals, electric arc welding processes, the use of explosives in mining, and farm silos. Worldwide annual emissions of anthropogenic nitrogen oxides are estimated at approximately 50 million metric tons (World Resources Institute 1994). The United States generates about 20 million metric tons of nitrogen oxides per year, about 40% of which is emitted from mobile sources.
  11. 11. Effects on Ecosystems:  Nitrogen oxides are precursors of both acid precipitation and ozone, each of which is blamed for injury to plants.  While nitric acid is responsible for only a smaller part of hydrogen ion (H+) concentration in wet and dry acid depositions, the contribution of nitrogen oxide emissions to acid deposition could be more significant.  It is nitrogen oxide that absorbs sunlight, initiating the photochemical processes that produce nitric acid.
  12. 12.  Approximately 90–95% of the nitrogen oxides emitted from power plants is nitric oxide; this slowly converts to nitrogen dioxide in the presence of ozone.  The extent and severity of the damage attributable to acid depositions is difficult to estimate, since impacts vary according to soil type, plant species, atmospheric conditions, insect populations, and other factors that are not well understood.
  13. 13. 3-Sulfur Oxides:  Sulfur oxides (SOx) are compounds of sulfur and oxygen molecules. Sulfur dioxide (SO2) is the predominant form found in the lower atmosphere. It is a colorless gas that can be detected by taste and smell in the range of 1,000 to 3,000 micrograms per cubic meter (μg/m3). At concentrations of 10,000 μg/m3, it has a pungent, unpleasant odor.
  14. 14.  Sulfur dioxide dissolves readily in water present in the atmosphere to form sulfurous acid (H2SO3). About Sulfur trioxide (SO3), another oxide of sulfur, is either emitted directly into the atmosphere or produced from sulfur dioxide and is rapidly converted to sulfuric acid (H2SO4).
  15. 15. Major Sources:  Most sulfur dioxide is produced by burning fuels containing sulfur or by roasting metal sulfide ores, although there are natural sources of sulfur dioxide (accounting for 35–-65% of total sulfur dioxide emissions) such as volcanoes. Thermal power plants burning high-sulfur coal or heating oil are generally the main sources of anthropogenic sulfur dioxide emissions worldwide, followed by industrial boilers and nonferrous metal smelters.  Emissions from domestic coal burning and from vehicles can also contribute to high local ambient concentrations of sulfur dioxide.
  16. 16. 4-Carbon monoxide (CO):  A colorless, odorless, poisonous gas produced by incomplete fossil fuel combustion.  Carbon monoxide interferes with the blood’s ability to carry oxygen from the lungs to the body’s organs and tissues. When inhaled, it readily binds to hemoglobin in the bloodstream to form carboxy hemoglobin (COHb) Hemoglobin , in fact ,has a much greater affinity for carbon monoxide than it does for oxygen , so even small amount of CO an seriously reduce the carrying less oxygen , brain function is affected and heat rate increases in an attempt to offset the oxygen deficit.
  17. 17. 5-Ground-Level Ozone:  Ozone (O3) is a colorless, reactive oxidant gas that is a major constituent of atmospheric smog.  Ground level ozone is formed in the air by the photochemical reaction of sunlight and nitrogen oxides (NOx), facilitated by a variety of volatile organic compounds (VOCs), which are photochemically reactive hydrocarbons.  Ozone may be formed by the reaction of NOx and VOCs under the influence of sunlight hundreds of kilometers from the source of emissions.  Ozone concentrations are influenced by the intensity of solar radiation, the absolute concentrations of NOx and VOCs, and the ratio of NOx and VOCs.
  18. 18. Health Impacts of Exposure:  The main health concern of exposure to ambient ground-level ozone is its effect on the respiratory system, especially on lung function several factors influence these health impacts, including the concentrations of ground-level ozone in the atmosphere, the duration of exposure and average volume of air breathed per minute.  Most of the evidence on the health impacts of ground-level ozone comes from animal studies and controlled clinical studies of humans focusing on short-term acute exposure.
  19. 19.  Clinical studies have documented an association between short-term exposure to ground-level ozone at concentrations of 200– 500 μg/m3 and mild temporary eye and respiratory irritation as indicated by symptoms such as cough, throat dryness, eye and chest discomfort, thoracic pain, and headache.
  20. 20. 6-hydrocarbons
  21. 21. Air Pollution In Refinery Processes
  22. 22.  Sources of environmental pollution from the petroleum industry:  Air emissions from the petroleum industry can be classified as combustion emissions, fugitive emissions, emissions from storage and handling of petroleum liquids and secondary emissions.  Combustion emissions are produced with the onsite burning of fuels usually for energy production and transmission purposes.
  23. 23.  Flaring is a specific source of combustion emissions in the petroleum industry.  Fugitive emissions (equipment leak emissions) are released through leaking valves, pumps, or other process devices.  Storage and handling emissions are contributed from the storage of natural gas and crude oil, as well as their intermediate and finished derivatives.  The water systems of a production or processing site (tanks, ponds, sewer system drains, etc...) are the main source of secondary emissions.
  24. 24. Sources and control of hydrocarbon emissions  The primary sources of hydrocarbon emissions are leaks from piping system components, evaporation from product loading, losses from atmospheric storage tanks and evaporation from wastewater  collection and treatment. The relative emission quantities from these sources might appear as provided in Table 2.
  25. 25. The Petroleum Refinery Sector(IN USA) ► 150 domestic refineries ► 17 MMbbls/day crude throughput, ~20% of world crude production ► Refineries have hundreds of emission points ► Second largest industrial source of GHGs
  30. 30. Refinery Process Units
  31. 31. Crude Desalting: ► Contaminants in crude oil can cause corrosion of equipment and processing problems ► Crude oil is washed with water ► Water is separated and now contains contaminants ► Largest source of wastewater at the refinery ► Largest source of benzene in wastewater ► Air emissions ► Benzene, VOC, other air toxics ► Control Technology: Steam stripper/Bio-treatment
  32. 32. Catalytic Reforming: ► Converts naphtha-boiling range molecules into higher octane reformate ► Produces hydrogen as a byproduct that can be used in Hydro-treaters or the hydrocracker Uses catalysts that can be regenerated ► Air emissions ► CAP (CO, Nox), HAP (benzene, toluene, xylene, naphthalene),VOC, dioxins ► Control Technology: Scrubber
  33. 33. Fluid Catalytic Cracking ► Upgrades heavier fractions into lighter, more valuable products ► Feed stocks ► Gas oils (from vacuum & atmospheric distillation, Coker) ► Vacuum tower bottoms ► Uses a fluidized catalyst to contact the feedstock at high temperature and moderate pressure to vaporize long chain molecules and break them into shorter molecules ► Largest source of emissions of SO2, NOx, CO, PM, and metals at the refinery ► Air emissions ► CAP (SO2, NOx, CO, PM), HAP (metals, ammonia), VOC ► Control Technology: Scrubber, ESP
  34. 34. Sulfur Recovery: H2S removal and recovery using an amine treating unit and the Claus process ► Air emissions ► CAP (SO2, NOx, CO), HAP (carbonyl sulfide, carbon disulfide) ► Control Technology: Scrubber
  35. 35. Thermal Processing: ► Converts heavy fractions into lighter products ► Types ► Delayed coking ► Fluid coking (no emissions) ► Vis-breaking (no emissions) ► Flexi-coking (no emissions) ► Air emissions ► Delayed coking unit emits CAP (SO2, NOx, PM), HAP (metals), VOC ► Control Technology: Flares
  36. 36.  Delayed Coking Unit
  37. 37. ► Heavy residues are thermally cracked in a furnace with multiple parallel passes (semi-batch process), which cracks the heavy, long chain hydrocarbon molecules into gas oil and petroleum coke ► Air emissions ► Steam vents ► Coke drill ► Coke pit
  38. 38. Refinery Process Unit Controls
  39. 39. Flares: ► Combustion control device used to burn waste gases in both normal and process upset conditions
  40. 40. Scrubbers ► Removal of material from the gas phase to the liquid phase ► SO2 removal from stack gases ► removal of organics from vent gases
  41. 41. Steam Strippers ► A distillation process whereby gases and other unwanted organics are removed from water ► Benzene removal from wastewater ► removal of other organics from water
  42. 42. Electrostatic Precipitators (ESP) ► PM control device that uses an induced electrostatic charge to remove small particles from gases (similar to static electricity)