Detailed information on Process Applications, their personnel and project history can be found by clicking on the following link:

Transcription

1 The following presentation was made available by Process Applications, Inc. The presentation was developed for the operator s workshop at the International Ozone Association meeting at Lake Lanier, Georgia, USA in October of It was presented by Kerwin Rakness and Glenn Hunter of Process Applications. Process Applications is a preeminent international firm that specializes in facilitating the implementation of prioritized technical knowledge for the water and wastewater profession. The consultancy is led by Kerwin Rakness who is an established expert in the operation and maintenance of ozone systems for drinking water treatment. He is the author of the book Ozone in Drinking Water Treatment recently (2005) published by the American Water Works Association. Process Applications specializes in providing operation and management services aimed at obtaining cost effective, improved performance and additional capacity from existing water and wastewater facilities. Their experience has shown that expensive plant upgrades can be reduced in cost, can be delayed, or can sometimes be avoided. They believe that their services are timely given the reduced funding available for new plant construction, the increasing cost of capital modifications, and the everincreasing and more stringent regulations governing water and wastewater treatment practices. Services are offered to municipalities, special districts, industries, consulting engineers, state and federal agencies, and universities. A unique aspect of the Process Applications approach is the emphasis on facilitating the implementation of optimization approaches by their clients personnel. This approach requires empowerment of local personnel such that improvements are accomplished and sustained. Detailed information on Process Applications, their personnel and project history can be found by clicking on the following link:

2 Ozone Water Treatment Applications, Equipment, and Safety

3 Ozone is an Unstable Odorous Gas Ozone Oxygen Chlorine O 3 O 2 Cl 2 Unstable Odor Stable No odor Stable Odor

4 Oxygen + Electric Discharge Produces Ozone One electron splits one oxygen molecule into two oxygen ions. 1) e - + 2) + One oxygen ion combines with one oxygen molecule to form one ozone molecule. NOTE: Ozone is unstable.

5 Water Ozone Application Disinfection (Giardia, virus, Crypto) Reduce disinfection by-products Chlorinate after filters to reduce THM/HAA Oxidation benefits T&O and color Micro-flocculation Iron and manganese Solvents, pesticides, etc. Disinfection usually controls dose

6 Ozone performs its work over time and through oxidation reactions. Ozone is a Powerful Oxidant Taste and odor compounds are also oxidized by ozone. Final <-Time Raw

7 HO. Iron Ozone Oxidation Reactions Inorganics Manganese Hydrogen Sulfide Bromide Pathogens Bacteria Virus Giardia Cryptosporidium Organics Other Solvents HO. Pesticides - HO. Color Taste & Odor - HO. Some hydroxyl radicals (HO. ) form naturally. HO. formation is greater at elevated ph (>8.0 more OH - ) HO. formation is enhanced with hydrogen peroxide (PEROXONE).

8 Ozone is a Powerful Disinfectant Ozone requires much lower CT value than chlorine or chloramine. Ozone CT value = 1.43 mg-min/l Chlorine CT value = 112 mg-min/l Chloramine CT value = 1,850 mg-min/l CT value for 3-log Giardia cyst 10 o C and ph 7

9 Disinfection By-Products Chlorine Ozone Trihalomethanes (THM) Haloacetic Acids (HAA) Bromate Assimilable Organic Carbon (AOC)

10 Ozone DBP Considerations Biodegradable organics Ozonation increases AOC Chlorinate after filters Biological activity in filters consumes AOC Bromate Bromide must be present Bromate limit is 10 μg/l (annual average) Minimize ozone dose is first control option Other control options include Lowering ph Add pre-chlorine and ammonia or pre-chlorine dioxide

11 Pre-Ozone Application Pre-oxidation, disinfection, and T&O removal Ozone Rapid Mix/Floc/Sed Cl 2 May reduce chemical Cl dose and improve 2 Cl 2 filter performance. Clearwell Filtration NH 3 is optional NH 3 Cl 2 to allow biological filtration and minimize Delay chlorine addition formation of THM.

12 Intermediate Ozone Application Disinfection, reduce ozone dose and T&O removal Rapid Mix/Floc/Sed Ozone Reduced ozone demand and slower ozone decay provide better conditions for Crypto disinfection. Clearwell Filtration Cl 2 NH 3 is optional NH 3 Cl 2 Also may improve filter performance.

13 Two-Stage Ozone Application Pre-oxidation, disinfection, reduce dose and T&O removal Pre-Ozone Rapid Mix/Floc/Sed Post-Sed-Ozone Cl 2 Usually for poorer quality waters Cl 2 Clearwell Filtration NH 3 is optional NH 3 Cl 2

14 Four Components of an Ozone System LOX Storage Vaporizer PRV Feed-Gas D Generating Power Supply Unit Flow Meter O 3 % wt M N 2 Filter Ozone Generator Contacting Water In Ozone Contactor Off Gas O 3 Destruct Water Out Blower M Flow Control Valve Flow Meter M

15 Ozone Feed-Gas Options Moisture Removal System Air Ambient Air Supply CRYO O 2 System PSA O 2 System O 2 O 2 Filter Ozone Generator VPSA O 2 System O 2 Purchased LOX O 2 LOX is currently the most common source of oxygen for ozone systems.

16 Ozone Equipment Has Been Simplified Earlier air-fed ozone systems Air Compressor Refrigerant Dryer Desiccant Dryer Ozone Generator Less equipment = Lower maintenance, capital cost, and operating cost Liquid Oxygen Storage & Ambient Vaporizers Ozone Generator Current oxygen-fed ozone systems

17 LOX Storage and Vaporization Ambient vaporizers LOX storage tanks

18 Oxygen Feed-Gas System Supplemental Nitrogen (Air) Feed System (1-5% of total gas flow) Air Compressor Desiccant Dryer 1%-5% nitrogen in feedgas improves generator efficiency by about 15% Air Receiver Coalescing Filter Particulate Filter F PRV Economizer M LOX Tank M FM O 2 D M Truck Fill M M Ambient Vaporizers To Ozone Generators M Pressure Regulating Valves Filters

19 Nitrogen-Feed Air System Flow measurement and control should be sized for 0.5% - 5.0% of total feed gas flow rate. Air compressor Filters Valves alternate desiccant dryer towers every few minutes (maintenance) Air storage tank

20 Oxygen Gas Filter, PRV, Purity and Dewpoint Monitor psig from vaporizers psig to generators Dewpoint monitor Filter Pressure regulating valves (might need two different sizes to obtain good pressure control over full gas flow range) Oxygen purity monitor

21 PSU cooling water Ozone Generator Cooling water OUT Power supply unit Ozone gas OUT Cooling water IN Oxygen gas IN

22 Ozone Contactor Ozone off-gas destruct Vertically baffled contactors Fine bubble diffusers Residual measurement & grab sampling

23 Bubble Diffuser Contactor FM M Vacuum & Pressure Relief To Off-Gas Destruct Quenching Chemical Ozone o o o o o o o o o o o o o o o o o o o o o o o o o o o o Sample Inlet (typical) Drain Access Door or Flange (typical)

24 Diffusers Rod Dome Gaskets Checking bubble pattern

25 Gasket Materials Hypalon Gortex Hypalon

26 Diffuser Issues Hypalon deteriorates quickly Viton is reported as better Gortex is reported best, but expensive If diffuser clogs quickly, consider less expensive gaskets and more frequent cleaning Reduced maintenance might justify more expensive Gortex gaskets

27 Contactor Access Air line for checking diffusers Top access Side access Consider water depth for checking diffuser bubble pattern

28 Ozone Residual Sampling Sample inlet inside contactor Texas tee Pumped from top of contactor Flow meter Analyzer/ transmitter Grab sample tap Probe & tee Flushing connectio n

29 Sampling Issues Minimize decay Gravity or pumped sample flow Length/diameter of sample line Sample flow rate Flexibility for adjusting sample locations within the contactor Provisions for grab sampling Close to probe, preferably downstream Use small (~1/8 ) dia. tubing and valve Number of analyzers

30 Valves for Ozone Gas Service Butterfly, ball, or plug valves may be used for on/off service or isolation Considerations for critical gas flow control locations such as the contactor gas inlet, include: V-port ball valve Butterfly valve Precision actuator Precision control valve such as V-port ball valve Function of control valves and flow meters under minimum gas flow conditions

31 Quenching Ozone Residual Eliminate ozone residual remaining at contactor outlet (safety consideration) Might be necessary for crypto disinfection Might not be necessary for Giardia or virus disinfection Calcium thiosulfate Sodium bisulfite Hydrogen peroxide Metering pumps Storage tank

32 Ozone Generator Components Oxygen IN Cooling water OUT SS tube, (ground electrode) Dielectrics Generator Shell Power Gas & electron flow in gap Cooling water IN Ozone (& oxygen) OUT

33 The Ozone Generator Controls the 6,000-20,000 volts 60 5,500 hertz ( % wt ) Electric Discharge Glass or Ceramic Dielectric O 2 O O O 2 e e O 2 O -- O - 2 O e - 2 O3 Stainless Steel Tube Cooling Water Ground Electrode O 2 ~98 % wt O 2 e - e - e - O -- e - Stainless Steel Lining (1-14 % wt ) ~10 % wt O 3 ( mm) ~0.5 mm Gap

34 Multiple-Tube Ozone Generator Cooling Water Out ~0.5 mm gap Cooling Water In From Metropolitan Water District Flow of electrons across gap causes corona

35 Dielectrics Wedeco Ozonia Fuji Trailigaz

36 Ozone Generator Cleaning Cleaning is more frequent when dried air is used for feed-gas Nitric acid forms when moisture is present in operating generator

37 Power Supply Unit Transformers Rectifier Inverter Cooling system

38 Generator Process Diagram Cooling Water Return FM Oxyge n FM M Ozone Generator M O 3 Ozone & Oxygen M Cooling Water Supply M kw Power Supply Unit Cooling Water Return

39 Ozone Generator Increase Power to Increase Production 127 kw 10,000 lb/day Oxygen (84 scfm) Ozone Generator 8% wt Ozone 800 lb/day Ozone 9,200 lb/day Oxygen 194 kw 10,000 lb/day Oxygen (84 scfm) Ozone Generator 10% wt Ozone 1,000 lb/day Ozone 9,000 lb/day Oxygen

40 Ozone Generator Efficiency Example Unit Cost of Ozone ($/l Based on energy price of $0.07/kWh and LOX price of $60 $/ton Ozone Concentration (%wt) Optimum range Design Condition: 10% wt, 1000 lb/day, 4.2 kwh/lb, 175 kw 12% wt, 800 lb/day, 5.2 kwh/lb, 175 kw Specific Energy (kwh/lb Generator SE LOX Use Ozone Concentration (%wt) lbs Oxygen / lb Ozon 8% wt, 1200 lb/day, 3.5 kwh/lb, 175 kw 5% wt, 1400 lb/day, 3.0 kwh/lb, 175 kw

41 Closed Loop Cooling Water? Better corrosion control More equipment O&M Closed loop pumps Open loop pumps Heat exchangers Owner and designer should evaluate need for closed loop cooling Heat exchangers Closed loop pumps

42 Sidestream Ozone Injection P FM Gas flow control valve M Fail-close Shut-off Valve Liquid M Trap High Pressure Switch P s P Multiple Fail-Safe Protection From Generator Flooding! M Heater To Atmosphere From Ozone Generators Consider turndown conditions when sizing sidestream pumps P FM P Check Valve P P Destruct Sidestream Pump Venturi Injector Mixing-enhancement nozzles Pipeline or other contactor Water Flow

43 Reaction/degas Sidestream Ozone Injection Eductor/static mixer Ozone Gas (vacuum) Liquid trap shutoff Pneumatic valve High pressure switch Check valve Destruct unit Sidestream pumps

44 Contactor Options With SSI Vertically baffled deep contactor is not necessary with SSI Horizontal baffled shallow contactor Pipeline contactor Shallow horizontal baffled Underground pipeline

45 Off-Gas System Vacuum & pressure relief Off-gas O 3 Vacuum control loop to blower VFD or control valve Heater To atmosphere M % wt PIT M 120ºF Vent-gas O 3 Demister 90ºF ppm v o o o o o o o o o o o o o o o o o o o o o o o o o o Drain Catalyst bed Blower M

46 Off-Gas Destruct Unit Heater Catalyst bed Off-gas from contactor Blower

47 Off-Gas Moisture Removal Particulate moisture collects in the demister and drips back into the contactor Drains at low points allow removal of condensed moisture in the off-gas piping and protect the destruct catalyst

48 Off-Gas & Vent-Gas Monitors Off-Gas Ozone Concentration (from contactor, % wt ) is used to calculate transfer efficiency Off-gas sample Discharge to atmosphere Ozone destruct Off-gas monitor Vacuum pump Vent-Gas Ozone Concentration (after destruct, PPM v )

49 Vacuum/Pressure Relief Valve Vacuum/pressure relief valve is for structural protection of contactor Two sets of weights in the valve set the vacuum and pressure limits at about 2-5 inches water column

50 Ozone Safety Advantages Ozone is not stored in bulk on-site Catastrophic large-scale release is not likely because generator shutdown eliminates supply of ozone Ozone is not explosive or flammable No reported fatalities due to ozone exposure

51 Important Concepts Regarding Ozone Safety Automatic warning - You can smell ozone before it will harm you! Effects of ozone exposure are a function of time and concentration First aid Low level exposure - get fresh air High level exposure - seek medical attention Fix leaks when they occur

52 Effects of Ozone Exposure Condition Detectable odor TLV-TWA 8-hr limit Headache, shortness of breath TLV-STEL 15-min limit Chest pain, dry cough, lung irritation, severe fatigue Immediately dangerous to life & health Expected to be fatal Ozone Concentration 0.01 to 0.04 ppm v 0.10 ppm v >0.10 ppm v 0.30 ppm v ppm v (1-2 hrs) 10.0 ppm v 50 ppm v (30 min) Data from Ozone Manual of Standard Practice, Workers Compensation Board of British Columbia, 1992

53 Reactions to Ozone Exposure Irritant to eyes, throat, nose, upper respiratory tract, and lungs Headaches, nausea, wheezing, or coughing Pulmonary edema (fluid build-up in lungs) No evidence that ozone exposure will cause cancer or harm the unborn Check with your doctor if you have special respiratory or heart conditions

54 Pressure & Vacuum Relief Vent-Gas Ozone Ventilation Blower <0.10 ppm v 3400 ppm v Off-Gas Destruct Off-Gas Ozone 0.5%wt Ambient Ozone 0.10 ppm v 10%wt 68,100 ppm v Ambient Oxygen Ozone Generator M O 2 Oxygen Supply Ozone Diffusers (TYP)

55 Ambient Ozone Monitor Audible, visual, and SCADA alarms Initial alarm at 0.1 PPMv Generator shut down at 0.3 PPMv Sample inlet near floor level

56 Ambient Ozone Monitor Readings at Plant C Ozone generator shutdown Typical reading Believe the readings. Your nose may become acclimated!

57 Leak Sources and Detection Flanges and valve stems Another option? Portable leak detector Threaded fittings Potassium iodide

58 Ozone Safety Information Ozone MSDS sheet Compressed Gas Association , CGA P-34, Safe Handling of Ozone-Containing Mixtures Including the Installation and Operation of Ozone-Generating Equipment Workers Compensation Board of British Columbia , BK-47 Ozone, A Manual of Standard Practice

59 Combustion Triangle Fuel Source (almost anything) Ignition Source (almost anything) Oxygen

60 Oxygen-Rich Atmosphere Oxygen content in air is 21% vol Oxygen-rich atmosphere is>23% vol A small ignition or heat source with any fuel source may cause reaction ranging from slow combustion to violent explosion Review safety and training materials from CGA or supplier

61 Oxygen Safety Information Oxygen MSDS sheet Compressed Gas Association , CGA G-4, Oxygen CGA G-4.1 Cleaning Equipment for Oxygen Service CGA P-12, Safe Handling of Cryogenic Liquids CGA P-39, Oxygen-Rich Atmospheres CGA AV-1, AV-8, Videos