Headworks International Inc.

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1 Headworks International Inc.

2 Fall th PERF Meeting: WASTE MANAGEMENT AND DISPOSAL Refinery Wastewater Treatment by MBBR and IFAS Reactors for Refractory COD Somnath Basu Headworks International

3 Contents Introduction Desalter Operating Principle Refinery Wastewater Treatment Opportunity Crudes and their Impacts Methodology for Process Monitoring and Control Opportunity Crudes on Wastewater Treatment Case Studies Remedial Measures Conclusion Acknowledgement

4 Introduction Opportunity crudes are newer types of crudes that have not been traditionally processed in the past These are available in the market in abundance and at discounted rates compared to benchmark prices But these are difficult to process because of their special characteristics Desalters and wastewater treatment systems play a critical role in overcoming many of challenges Refiners have tried blending these crudes with traditional ones to balance their properties, but: Sometimes the crudes are not compatible May lead to formation of solid or semi-solid asphalt materials that precipitate in desalters

5 Desalter Operating Principle Crudes contain many impurities that can impede the refining process Desalters are the first equipment to handle and process crudes It makes intimate contact between crude and water by thorough mixing to: Transfer inorganic salts and solids from crude to water as brine stream as much as possible Separate crude and water in two layers

6 Desalter in Petroleum Refinery Crude is preheated ( o C) and mixed with wash water (5 8% v/v) Passed through a mixing valve and static mixer In desalter, oil and water separate in top and bottom layers with an emulsion layer (rag layer) in between Thick emulsion layer indicates poor oil-water separation Large concentration of water in oil phase and oil in water phase Excessive water in desalted crude causes high energy consumption in heating and pumping, and potential corrosion by dissolved salts Excessive oil under-carry in brine leads to large oil and grease (O&G) and large COD loads to wastewater treatment

7 Typical Refinery Wastewater Treatment

8 Wastewater Treatment Desalter brine mixed with other wastewater sources in an equalization tank Wastewater fed to API separators for primary oilwater separation and suspended solids removal Dissolved (or induced) air or gas separator for secondary separation Biological treatment removes O&G and COD Clarifiers remove biomass from treated wastewater Tertiary filtration, if needed, to meet discharge requirements

9 Opportunity Crudes and their Impacts Opportunity crudes disturb desalter operations due to constituents that refineries are not typically designed to process Some examples of opportunity crudes: Heavy crudes from Canadian Rockies Doba crude from West Africa Light tight oil (LTO) from North American shale plays Characteristics of concern: API gravity Viscosity Naphthenic acids content Metals concentrations, especially Ca and Fe Filterable solids (FS) Amines content

10 Western Canada Crudes Typically heavy crudes with API Gravity of Have high viscosity, which causes challenges for refiners: Demand high energy in piping transportation Cause poor mixing leading to reduced salt removal from crude Emulsion formation in desalter leading to poor oil-water separation Have high filterable solids (FS) Difficult to separate in desalter because of their fine size Grow the rag layer inside desalter leading to poor oil-water separation High concentration of sulfur compounds Health and safety risks High corrosivity High Total Acid No. (TAN) High concentration of naphthenic acids cause corrosion of metals Not sufficiently broken down by biological treatment

11 Doba and other West African Crudes Heavy Crude with API Gravity of 21 Also have high TAN Have high metals content Causes high potential for scaling and deposition in wastewater treatment equipment when carried over with brine Large excess of calcium that can poison FCC catalysts if carried over with desalted crude Contribute to high conductivity of crudes leading to poor oil-water separation in desalter Stabilizes the desalter emulsion layer preventing oil and water in the rag layer to break loose

12 Light Tight Oil (LTO) LTOs are crudes derived from hydrofracturing of shale formations Hydrofracturing and horizontal drilling have changed the global supply and demand over the last few years US is the largest producer of LTO grade crudes (Source: US Energy Information Administration, 2015) (Source: US Energy Information Administration, 2013) Rank Country Shale Oil Proven Reserves, billion bbl 1 Russia 75 2 United States 58 3 China 32 4 Argentina 27 5 Libya 26 6 Australia 18 7 Venezuela 13 8 Mexico 13 9 Pakistan 9 10 Canada 9 Total Global Recoverable Shale Oil Reserves = 345 billion bbl

13 Light Tight Oil (LTO) LTOs are light crudes with high API Gravity of >42 Refiners blend LTOs with heavier crudes to balance properties, but they are not always compatible Challenges of LTO crudes: Incompatible with certain heavy crudes, leading to precipitation of asphaltenes High filterable solids Entrained H 2 S that requires addition of amines for handling and transportation High concentration of paraffin wax leading to fouling of equipment at low temperatures

14 Effects of Opportunity Crudes Low API Gravity: difficult handling, processing, and transportation High Acidity: high COD and affects microbiological population High Metals Concentration: Calcium and iron are present both in particulate and dissolved forms High Sulfur: Corrosion potential, health and safety risks High Filterable Solids (FS): clogging equipment, reduction of active volume of desalters, and promoting stabilization of rag layers High Amines Concentration: part amines partition with water phase and leave with brine to wastewater, create high COD and nitrification loads Target Light Crudes Heavy Crudes Salt Removal Efficiency, > 90 in a single stage, > 95 > 90 in a single stage, > 95 % in a double stage desalter in a double stage desalter Salt in Desalted Crude, ptb < 2 < 2 Water carryover in < 0.3 < 0.7 Desalted Crude, % (v/v) Oil Under Carry in Brine, ppm < 200 < 1000

15 Methodology for Process Monitoring and Control API Gravity of crudes measured by hydrometer (ASTM Method D1298) Filterable solids measured by filtration through filter of 0.45µm (ASTM Method D4807) Water in oil determined by colorimetric titration (ASTM Method D4928) Chloride in crude measured by Potentiometric titration (ASTM Method D6470) Chloride in water measured by Ion Specific Electrode Oil in water analyzed by ASTM Method D3921 TAN determined by titration to neutralize sample with standard KOH solution, and expressed as mg of KOH/g of crude Portable Electric Desalters (PED) are benchtop units that simulate operation of desalter to demonstrate salt removal potential, oil-water separation, and emulsion formation of a given crude For wastewater treatment, parameters monitored for API Separator and DAF are O&G and TSS For biotreatment, parameters monitored are O&G, TSS, BOD, COD, and reactor basin MLSS and MLVSS

16 Effects of Processing Opportunity Crudes on Wastewater Treatment The effects of the contaminants resulting from processing opportunity crudes are shown in three Case Studies The studies cover a wide range of refinery locations, and crude sources and types

17 Case 1 US gulf coast refinery that processes a heavy sour crude of 21.5 API Gravity and 3.4% sulfur content Effluent requirements are routinely met, with effective tertiary filters However, foaming was severe and clarifiers became non-functional on occasions Foam sample indicated sludge bulking due to proliferation of Nocardia Filamentous bacterial population that floats creating a thick layer of foam on surfaces of aeration tanks and secondary clarifiers (photomicrograph of S. Pineformis Nocardia after 1000 x illumination of Gram Stained sample) Possible reasons for growth: High concentration of oil Excessively high solids retention time (SRT) in aeration basins

18 Case 2 North American refinery processing LTO from North Dakota Free oil escaped wastewater treatment on an occasion and appeared as a sheen of oil on the surface of receiving water Review of operations data indicated excessive oil carried over with brine Due to the desalter failing to separate oil from water There was a high concentration of FS, which settled down in desalter and treatment plant equipment This caused reduction of active volumes and HRT of all process equipment, leading to escape of oil with treated effluent A new desalter system was installed to handle situation

19 Case 3 Refinery in the Far East using Arab Light Sweet crude They blended with medium heavy sour crude with 28 API Gravity and 2.4% sulfur content Salt removal by desalter dropped from 80% to 50% Removed the heavy crude from the blend and restored original salt removal efficiency

20 Remedial Measures for Desalters Control formation of emulsion and growth of resulting rag layer by: Characterization of crude to evaluate potential for emulsion formation due to presence of compounds Select correct type and dosage of demulsifying chemicals to break emulsion using prior bench scale tests by Portable Electrostatic Desalter (PED) unit. Follow standard operation procedures for desalter by monitoring its operation Closely monitor oil-water interface and presence of rag layers Determine and maintain mudwashing frequency for high FS crudes Acids are effective in treating amines, but create a corrosive environment in desalter Demulsifiers will not give best performance of desalter if proper operation procedures are not followed

21 Remedial Measures for Wastewater Treatment: MBBR and IFAS Some opportunity crudes contain large quantities of naphthenic acids which leave as refractory COD MBBR has superior BOD and COD removal rates to activated sludge

22 Wastewater Treatment Technologies Suspended Growth Activated Sludge Attached Growth Batch Continuous Dynamic Fixed Film Static Fixed Film Sequencing Batch Reactors (SBR) Conventional Activated sludge MLE nutrient removal Bardenpho process Membrane Bioreactors (MBR) Integrated Fixed-Film Activated Sludge (IFAS) Rotating Biological Contactors (RBC) Moving Bed Biofilm Reactors (MBBR) Trickling Filters Rope Media Biological active filters (BAF)

23 IFAS vs. MBBR IFAS (Integrated Fixed Film Activated Sludge) Includes Return Activated Sludge (RAS) Fixed film & Suspended growth MBBR (Moving Bed Bioreactor) No RAS - Once through process Fixed film Only Return Activated Sludge Waste Activated Sludge Waste Sludge

24 IFAS and MBBR Benefits Site constraints or restriction Resiliency to peak flows and loads Easy retrofit of existing CAS installations Resilient to peak flows and shock loads Attached growth biomass is resistant to toxic and shock loads Effective in degrading more refractory COD than can be obtained by traditional biological treatment processes Biomass are less vulnerable to bulking and foaming

25 Biofilm Carriers (Media)

26 Biological Growth on Media Mixing energy controls the biological thickness BOD Nitrifiers

27 Retention Screens/Sieves

28 Screen Arrangement (Typical)

29 Advanced Oxidation Processes (AOP) Biological oxidation of organic wastes involving enzymatic catalysis are most cost effective These processes not suitable when the reactants are toxic to the biomass or recalcitrant to biotreatment Advanced chemical oxidation covers a group of technologies that depend on high energy hydroxyl radicals (OH*) to facilitate breakdown of recalcitrant chemicals

30 Advanced Chemical Oxidation Processes Standard Oxidation Potentials of Various Oxidants Oxidizing Agent Fluorine 3.03 Hydroxyl Radicals (OH * ) 2.80 Singlet Oxygen 2.42 Ozone 2.07 Persulfate Ions (S 2 O 8 2- ) 2.01 Hydrogen Peroxide 1.78 Permanganate Ions 1.68 Chlorine 1.36 Bromine 1.09 E o (Volts)

31 UV-Peroxide Treatment UV-Peroxide treatment is one of the commonly used AOPs UV radiation induces in-situ generation of OH* radicals from hydrogen peroxide, as: H 2 O 2 + hν 2 OH* This is a photocatalytic reaction Hydroxyl radicals participate in the chain propagation and termination reactions The same amount of hydrogen peroxide generates double the number of hydroxyl radicals AOP may be needed to achieve stringent effluent COD limits after biotreatment as a polishing step Prior bench/pilot scale tests are essential

32 Conclusions Opportunity crudes provide refiners opportunities for margin enhancement However, these crudes present difficult challenges for processing due to their special characteristics Desalters are important in ensuring that contaminants are effectively removed Poor desalter performance can lead to: Corrosion of refining process equipment Catalyst poisoning Poor performance of wastewater treatment, potentially leading to discharge permit violations Challenges of opportunity crudes can be overcome by: Close monitoring and control of desalters Proper chemical dosing program in the desalter Enhancement of biological treatment performance by MBBR Routine sampling and analysis Consider AOP on a case by case basis

33 11000 Brittmoore Park Dr. Houston, TX Phone: Fax: