Advances In Aeration Control MWEA Fall Process Seminar November 6, - PDF document

10/27/2013 Advances In Aeration Control MWEA Fall Process Seminar November 6, 2013 11:15 AM 11:15 AM East Lansing, MI Thomas E. Jenkins President JenTech Inc. Je JenTe nTech I h Inc. 6789 N. Elm Tree Road Milwaukee, WI 53217 414 ‐ 352 ‐ 5713 info@jentechinc.com 1 Advances in Aeration Control • Importance of Aeration Control • Advances in Aerators • Diffused Diffused • Mechanical • New Blower Technologies • Turbo • Screw Blowers • Advances in VFDs • Advances in VFDs • Improved Instrumentation & Control Strategies • DO Control Techniques • Feedforward Control 2 2 1

10/27/2013 Factors Driving Advances in Aeration Control • More Demanding Permit Requirements • More Complicated Processes • Higher Energy Costs • Increased Global Technology Transfer • Improved Instrumentation Hardware 3 3 Improved Control Means More Stable Processes • Process Performance Comes First! • Adapting Automatically to Upsets and Changes Can Improve Performance • Control Strategies Must Integrate Process Equipment Characteristics • Most Municipal WWTPs Operate at 1/3 of Design Capacity CONSIDER TAKING TANKS OUT OF SERVICE 4 4 2

10/27/2013 Energy Is A significant Concern, and Can Be Used To Justify Systems Aeration is the Most Significant Energy Use in a WWTP WWTP 34% Pumping and Other 55% HVAC 11% Aeration Most Utilities Offer $ Incentives for Reducing Energy Use 5 5 Energy Consump � on ≠ Energy Cost Rates vary with: • Time of Day • On ‐ peak, Off ‐ Peak • Day of Week • Size of Costumer • Demand (kW) and Consumption (kWh) The First Goal of an ECM (Energy Conservation Measure) is to Reduce Cost While Maintaining or Improving Process Performance 6 6 3

10/27/2013 Mechanical Aerators Variable Speed or On/Off Mechanical Aerators Power SAE 2.5 gth 2.0 4 0 4.0 bhp/ft. rotor leng 1.5 1.0 3.5 0.5 3.0 0.0 SAE lb/hp hr 30 50 70 90 2.5 2.0 rpm 1.5 SOTR 1.0 10 OTR lb/hr/ft rotor 0.5 5 0.0 0 length 30 40 50 60 70 80 90 30 50 70 90 rpm rpm 7 Diffused Aeration Coarse Bubble Changing to Fine Pore Diffusers Should Always Be Examined! 8 8 4

10/27/2013 New Aeration Technologies: • Mixing and Aeration Combined • Actually Re ‐ invention of Older Technology • Allows Separate Control of Oxygen Transfer and Mixing Energy • New Diffuser Geometries ff and Materials • Fouling Resistance • Improved OTE 9 9 Diffused Aeration Energy • Proportional to Submergence • Deeper is Better • Also Requires Higher Blower Power • Proportional to Air Flow per Diffuser • Flux Rate (1 to 10 SCFM/ft 2 Typical) • Lower is better • Proportional to Actual DO Concentration P ti l t A t l DO C t ti • Lower is Better • DO Control is Significant • Most Plants Are Too Conservative In DO Setpoint 10 10 5

10/27/2013 Diffused Aeration Blower Power Ratio (Compared to 2.0 ppm DO) 4.50 4.00  * Q C 2 . 0  er  actual 20 Nominal Power Multiplie 3.50  * Q C C  2 . 0 20 actual 3.00 2.50 2.00 1.50 1.00 0.50 0.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 Actual DO Concentration, ppm Based on 500' ASL, 55 °F, 9.9 ppm C sat Excess DO means significantly more aeration power. 11 11 Impact on Control Systems • Lower Air Flow Rates • Reduce Valve Sizes • Re ‐ Scale or Replace Flow Transmitters R S l R l Fl T itt • Mixing Limits • Impact on Blowers • Turndown May Become an Issue • Verify Pressure Capacity (More Submergence) • DO Control • Maximizes Savings Opportunity • Over ‐ Aeration More Common 12 12 6

10/27/2013 Aeration Blowers and Energy Efficiency Varies with Blower Type Range is 60% to 80% 13 13 Blower Considerations • Efficiency • Across Actual Load Spectrum • Control • Constant Pressure or Flow Based • Control and Protection Should Be Integrated • Turndown • Often More Important Than Efficiency f h ff • Turndown Limits Must Be Included In Control Strategy 14 14 7

10/27/2013 Example Turbo Blower Characteristics System Curve 15 15 Example Screw Blower Characteristics Typical Screw Blower Performance at Constant Speed 55 °F T i 14.4 p i 40.0 68.0% 35.0 67.0% fficiency 30.0 66.0% kW 25.0 65.0% SCFM/k Adiabatic Ef 20.0 64.0% SCFM/kW 15.0 63.0% Wire to Air Efficiency 10.0 62.0% 5.0 61.0% 0.0 60.0% 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 psig Discharge 16 16 8

10/27/2013 Blower Control Considerations • Blower Control Usually Included In Packages • Screw Blowers • Typically More Turndown • Control Simpler • Turbo Blowers • Often More Efficient and Lower Cost (CHANGING) • Turndown Limits Must Be Included In Control d l d d l Strategy – Surge Is a Concern 17 17 VFD Applications Have Changed • VFDs Are More Reliable And Less Costly • Many Utilities Offer “Automatic” VFD Incentives • Can Be Applied to ALL Types of Blowers • Proper Selection and Engineering is Required • Medium Voltage (> 600 Volts) Now Cost Effective • Increased Competition, Lower Prices • Typically Greater Than 750 hp 18 18 9

10/27/2013 Payback on Medium Voltage Drives Can Be Good Exisitng Guide Vane Control Cumulative Operating Cost New 2000 hp motor, 2000 hp VFD $14,000,000 umulative Energy $12,000,000 $10,000,000 $8,000,000 $6,000,000 Capital + Cu $4,000,000 $2,000,000 $- 0 5 10 15 20 Years of Operation 19 19 DO Control Can Be Very Cost Effective • Will Save 25% Or More Compared to Manual • Matches Air Supply To Demand • Usually Improves Process Stability ll S bili • DO Is An Indirect Indicator of Process Performance • Low Capital Cost May Make Payback Shorter Than Other Changes • Control Complexity Should Be Matched to System • Total Blower Air Flow Only o a o e o O y • Individual Basin Flow Control • Separate Grid DO and Flow Control Within Basins • New Strategies Improve Efficiency • Most ‐ Open ‐ Valve • Direct Flow Control Eliminates Pressure Control 20 20 10

10/27/2013 Most ‐ Open ‐ Valve Control • MOST ‐ Open ‐ Valve (MOV) Control is NOT Necessary for DO Control or Blower Control • Technique for Minimizing System Pressure by Keeping at Least One Basin Valve at Max Position at All Times • Older Systems Work By Adjusting Pressure Setpoint • Newer Strategies Work Directly With Flow Control 21 21 Pressure Control • If Constant Pressure Is Maintained Changes in One Valve Won’t Affect Other Basin’s Air Flows • If Pressure Setpoint is Too High Power Is Wasted Typical Centrifugal Blower & System Curves 10.0 9.0 re, psig 8.0 Pressure Setpoint Pressure Setpoint Pressu 7.0 6.0 Wasted Power 5.0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Flow, SCFM 22 22 11

10/27/2013 Direct Flow Control • Is Simpler and More Stable • Typically Reduces Blower Power 5% to 10% 23 23 New Analytic Instruments for Control • Optical DO Probes Replacing Membrane Types • Multi ‐ Channel and Remote Transmitters • New Nutrient Analysis Instruments • Chiefly for Nutrients – Nitrification/Denitrification • Many Still Maintenance Intensive • Most Ammonia Control Strategies Used In Conjunction with DO Control Conjunction with DO Control • New Feedforward Controls Based on Measuring Process Demand 24 24 12

10/27/2013 Offgas Based Feed Forward Control • Determines Air Demand By Measuring OUR and OTE • More Stable and Precise 25 25 Use Simple Payback To Calculate Cost Effectiveness • Process Requirements Come First! • Use Present Worth for Longer Time Periods • Implementation for Energy Conservation Should Be Justified By Best Payback     EquipmentC ost    Payback , years     AnnualSavi ngs 26 26 13

10/27/2013 Aeration and Energy Over Life of Equipment: Energy Cost is more Significant than Equipment, Installation, or Maintenance Costs 27 27 Questions? http://www.wiley.com/WileyCDA/WileyTitle/productCd ‐ 1118389980.html 28 28 14