NEWTONS MORE THAN JUST A GREAT SNACK THE KEY TO COMPARING MIXER TECHNOLOGIES

Transcription

1 November 18, 2014 NEWTONS MORE THAN JUST A GREAT SNACK THE KEY TO COMPARING MIXER TECHNOLOGIES BOB WIMMER AND ED KOBYLINSKI

2 November 18, 2014

3 November 18, 2014 MIXING GENERAL: BASIC ISSUES l Want rapid blending of MLSS of two or more streams to intermix suspended solids l Want dissipason of incoming kinesc energy l Want rapid mixing of soluble rbcod and nitrate l Want shear to expose inner floc and acsve microbes to rbcod and nitrate l High denitrificason rates only possible with high rbcod concentrasons

4 November 18, 2014 MIXING THEORY:TRADITIONAL l Pumping rate is a funcson of impeller speed and diameter l Q = Nq * RPM * Dia 3 l Nq = characterissc pumping value unique to type of impeller l RPM = impeller rotasng speed (revs/ minute) l Dia = impeller diameter in feet

5 November 18, 2014 MIXING THEORY: TRADITIONAL l Pumping power is a funcson of impeller speed cubed and diameter to the 5 th power l P = Np * spgr * RPM 3 * Dia 5 * 1.523*10 13 l Np = characterissc pumping value unique to type of impeller l RPM = impeller rotasng speed (revs/ minute) l Dia = impeller diameter in inches

6 November 18, 2014 OBJECTIVE l Input energy into tank and get liquid in moson with the least amount of electrical energy l Meet process objecsves without transferring excessive amounts of oxygen l Turnover of liquid will ssmulate oxygen transfer Do Not Want Surface Turbulence

7 SUMMARY OF FIELD TESTING AT ROGERS ARKANSAS November 18, 2014

8 FACILITIES Tested new 4.7 mgd rated treatment train Anaerobic zone divided into 3 cells in series Anoxic zone divided into 3 cells in series 5 Hp top entering mixers - axial flow down- pumping impellers

9 ANAEROBIC AND ANOXIC ZONE SCHEMATIC Flow back to aerobic zone Anoxic Cell 1 Cell 2 Cell 3 MLSS recycle from aerobic zone Influent plus RAS Cell 1 Cell 2 Cell 3 Anaerobic/ FermentaSon

10 ANAEROBIC ZONE Baffle wall submerged at above average flows Baffle Wall Submerged Port Baffle Wall Surface Port

11 ANOXIC ZONE Baffle Wall Gap from Surface to Floor

12 MIXING TESTS Mixers designed at 34 rpm Mixers were run at three different speeds 28 rpm 80% speed 16 rpm 50% speed 8 rpm 30% speed 69 inch diameter impeller- down pumping

13 TOP ENTERING MIXERS At 28 rpm there is liple surface turbulence Liple surface vortexing Vortexing transfers oxygen Surface DO less than 0.4 mg/l

14 ANOXIC ZONE CELL #2 SAMPLE LOCATIONS point #6 Submergence, sample ft below surface First Anoxic Zone 1 3 Cell #2 Cell #3 Point #2 Submergence, ft sample # ft below surface #6 #2 2 6 point #4 ft below surface 2 ft #4 point #3 ft below surface # #5 #1 8 6 Point #5 Submergence, Point #1 Submergence, sample # ft below surface sample # ft below surface

15 ANOXIC ZONE CELL #2 MLSS PROFILE Anoxic Cell #2-28 rpm 3,640 3, , , ,560 5 MLSS, mg/l 3, ,520 Largest Variation mg/l 3.35% variation 3,500 3,480 3,460 3, Depth, ft Location

16 ANOXIC ZONE CELL #2 MLSS PROFILE Anoxic Cell #2-16 rpm 3, , , MLSS, mg/l 3, ,400 Largest Variation mg/l 4.6% variation 3,350 3, Depth, ft Location

17 ANOXIC ZONE CELL #2 MLSS PROFILE Anoxic Cell #2-8 rpm 3, , , MLSS, mg/l 3, ,350 Largest Variation mg/l 5.52% variation 3,300 3, Depth, ft Location

18 MIXING POWER TURNDOWN At 100% speed (34 rpm) mixers draw 5 Hp At 80% speed (28 rpm) mixers draw 2.8 Hp At 50% speed (16 rpm) mixers draw 0.5 Hp At 30% speed (8 rpm) mixers draw 0.1 Hp Mixer liquid pumping is proporsonal to rpm 80% speed = 80% pumping capacity

19 MIXING PERFORMANCE November 18, 2014 RPM gpm Hp Draw Hp/ Kft 3 Turnovers/ minute 28 31, , ,

20 November 18, 2014 TEST DESIGN PROCEDURE l Set desired turnovers in mixing zone to get direct pumping rate 0.2 turnovers/ minute l Size top entering mixer for direct pumping l Set RPM maximum at 15 l Want impeller diameter to fall within range of minimum of 25% of narrowest tank width and not more than 40% of tank narrowest width l Basin Volume 19,490 r 3

21 November 18, 2014 TEST DESIGN CONTINUED l Direct Pumping Rate = 3,899 r 3 / min = 29,170 gpm l Top entering Mixer Design l RPM = 12 l Impeller Dia = 7.5 r l Pumping Rate = 29,730 gpm l Power Draw = 0.82 Hp or 0.04 Hp/ Kr 3 l Submersible Mixer SelecSon l Pumping Rate = 13,160 gpm each use 2 units l Power Draw = 12.8 Hp each (25.6 Hp Total) or 1.3 Hp/ Kr 3

22 November 18, 2014 TEST DESIGN CONTINUED l Conclusion Submersible Mixer Claims for Induced Pumping must be correct! l We know we have installasons at less than 1.3 Hp/ Kr 3 l Submersible mixer manufacturers have been claiming that our power inputs values are too high at Hp/ Kr 3

23 November 18, 2014 DIRECT PUMPING VERSUS INDUCED PUMPING l FricSon occurs and a fast moving liquid will drag along the slower moving liquid. Net result is bulk liquid movement l Need to view mixer as a pump imparsng energy into the tank l Top entering mixers pump water at a low velocity relasve to the bulk flow in the tank l Submersible mixers generate a high velocity jet relasve to the bulk flow in the tank l We have been trying to measure mixing by power input not power transferred to the liquid phase

24 November 18, 2014 DIRECT PUMPING VERSUS INDUCED PUMPING l The energy imparted to liquid can be expressed as kinesc energy. l Liquid energy can be described through Momentum

25 November 18, 2014 MOMENTUM l Momentum is defined as a measure of the moson of a body equal to the product of its mass and velocity l Momentum is a measure of the energy contained by mass that is in moson and through fricson that energy can be imparted to other fluid mass l So for the purposes of mixing, momentum imparted into the system will gradually induce other liquid into moson and liquid in moson will keep solids in suspension

26 November 18, 2014 MOMENTUM CALCULATION l RPM = 12 l Top entering Mixer Design l Impeller Dia = 7.5 r = r 2 area l Pumping Rate; Expressed as volume flow per second and mass flow per second = 29,730 gpm = 3,974 r 3 / min = r 3 / sec = 247,948 lb/ min = 4,132.5 lb/ sec l Velocity = r 3 / sec/ r 2 = 1.5 r/ sec

27 November 18, 2014 MOMENTUM CALCULATION l Momentum = 4,132.5 lb/ sec * 1.5 r/ sec = 6,199 r lb/ sec 2 l Momentum is energy input into system and becomes the reference point for comparison between mixer types.

28 November 18, 2014 MOMENTUM CALCULATION l Using data from Flygt calculate momentum from each mixer. Mixer impellers have different pitch resulsng different power draw and volume of liquid pumped.

29 November 18, 2014 FLYGT MIXER DATA Model Hp Nq Np RPM Dia, ft ft 3 /min 1,240 1,401 1, lb/ sec 1,290 1,457 1, Area, ft ft/ sec Ft lb/ sec 2 9,395 11,984 13,394 6,379

30 November 18, 2014 FLYGT MIXERS Model 4640 RPM 860 Impeller Dia Power draw Pumping rate 1.2 ft 3.2 Hp 4,840 gpm Impeller angle 9 Momentum 6,379 ft lb/ sec 2 Power per unit volume = 0.16 Hp/ Kr 3

31 November 18, 2014 FLYGT MIXERS l The 0.16 Hp/Kr3 power input is a liple low based upon our current experience but is in a range that Flygt claims is more correct for mixing

32 November 18, 2014 MIXING COMPARISON: CASE 2 l Let s look at a equivalent mixer sizing for to 80% speed condisons at Rogers l 80% speed equaled a turnover rate of 0.32 turnovers/ min l Oren fall in between mixer sizes for Flygt

33 November 18, 2014 TOP ENTERING MIXER CALCULATION Basin Volume 19,493 ft 3 Turnover/ min 0.28 Pumping rate 5,458 ft 3 / min RPM 12 Impeller Dia 100 inches Pumping Rate 40,781 gpm Power draw 1.4 Hp Impeller area ft 2 Velocity 1.67 ft/ sec Momentum 9,443 ft lb/ sec 2 Power per Unit volume = 0.07 Hp/ Kr 3

34 November 18, 2014 FLYGT MIXERS Model 4660 RPM 580 Impeller Dia Power draw Pumping rate 1.9 ft 6.5 Hp 9,280 gpm Impeller angle 3 Momentum 9,395 ft lb/ sec 2 Power per unit volume = 0.33 Hp/ Kr 3

35 MOMENTUM CONVERSION TO THRUST Divide momentum by the gravitasonal constant lbm r/ sec 2 This converts momentum to lb force or lbf 1 Newton = lbf Divide lbf value by to get Newtons

36 TARGET THRUST VALUES Target Momentum for lower intensity = 6,199 r lb/ sec 2 = 875 Newtons Target Momentum for higher intensity = 9,443 r lb/ sec 2 = 1,306 Newtons SI momentum units = Thrust Kg meter/ sec 2 = Newtons

37 MIXING COMPARISON LOWER INTENSITY Units Top Entering Flygt Aqua DDM Wilo/ EMU Impeller, ft RPM , Hp gpm 29,730 4,840 3,557 19,989 ft lb/ sec2 6,199 6,379 5,434 6,517 Thrust, Newtons November 18, 2014

38 MIXING COMPARISON HIGHER INTENSITY Units Top Entering Flygt Aqua DDM Wilo/ EMU Impeller, ft RPM , Hp gpm 40,780 9,280 4,520 9,360 ft lb/ sec2 9,440 9,395 8,760 8,931 Thrust, Newtons 1,306 1,299 1,211 1,250 November 18, 2014

39 Black & Veatch Holding Company All Rights Reserved. The Black & Veatch name and logo are registered trademarks of Black & Veatch Holding Company.

40 CONCLUSIONS Thrust/ Momentum is proper way to compare mixers on equal foosng except for INVENT For INVENT compare direct flow with axial down pumping mixers

41 MIXING COMPARISON Aqua DDM appears out of line but based upon basin volume the right momentum/ Thrust value falls in between the 3 and 5 hp units and between the 5 and 7.5 Hp units This will be true of all units. Proper size can fall in between two standard sizes. November 18, 2014

42 COLLECTION SYSTEM ISSUES MLSS Return Flow Slot in Wall Top to Floor Deniter gate MLSS Recycle Influent Overflow RAS 3 Anaerobic Cells in series Overflow Underflow November 18, 2014

43 AQUA AEROBICS Model 3 Hp 5 Hp 20 Hp 75 Hp Hp Nq Np RPM 1,200 1, Dia, ft ft 3 /min ,575 3,914 lb/ sec ,637 4,070 Area, ft ft/ sec ft lb/ sec 2 5,434 8,760 28,937 88,191 November 18, 2014

44 AQUA AEROBICS: CASE 1 CONDITIONS We want to match a 6,200 r lb/ sec 2 momentum value Momentum falls between the 3 Hp and 5 Hp Aqua DDM units Assume we use the 3 Hp DDM unit Hp/ Kr 3 = or 18.5 Hp/ MG lower power per volume than Aqua Recommends They recommend 30 Hp/ MG for MLSS applicasons November 18, 2014

45 November 18, 2014 MIXER DESIGN COMPARISON l Next comparison is using the same example based upon Rogers but using the Aqua Aerobics DDM floasng mixer l It is a down pumping mixer l Fixed speed unit with Hp sizes varying from Nominal 3 Hp (2.7 Hp draw) to 75 Hp (67.5 Hp draw)

46 WILO/ EMU MIXER DATA Mixer Impeller Dia, inches RPM Flow, gpm Power, Hp Thrust, Newtons TR , ,180 TR , ,250 TR , ,140 TR , November 18, 2014

47 WILO/ EMU MIXERS Target Momentum for lower intensity = 6,199 r lb/ sec 2 Target Momentum for higher intensity = 9,443 r lb/ sec 2 I did not give WILO the target momentum values. Was looking for their recommendasons. November 18, 2014

48 WILO/ EMU MIXERS LOWER INTENSITY TARGET = 6,199 FT LB/ SEC 2 Model TR215 RPM 31 Impeller Dia ft Power draw 1.34 Hp (0.07 Hp/ Kft 3 ) Pumping rate 19,989 gpm Momentum 6,517 ft lb/ sec 2 Thrust 900 Newtons November 18, 2014

49 WILO/ EMU MIXERS HIGHER INTENSITY TARGET = 9,443 FT LB/ SEC 2 Model TR60 RPM 366 Impeller Dia ft Power draw 5.23 Hp (0.27 Hp/ Kft 3 ) Pumping rate 9,360 gpm Momentum 8,931 ft lb/ sec 2 Thrust 1,250 Newtons November 18, 2014

50 AQUA AEROBICS: CASE 2 CONDITIONS We want to match a 9,440 r lb/ sec 2 momentum value Momentum falls between the 5 Hp and 7.5 Hp Aqua DDM units Assume we use the 5 Hp DDM unit = 8,760 r lb/ sec 2 momentum value Hp/ Kr 3 = or 30.8 Hp/ MG Aqua recommends 30 Hp/ MG for MLSS applicasons November 18, 2014

51 AQUA AEROBICS Aqua bases their claims for mixing based upon operason of about 1,000 SBR systems using an anoxic fill cycle While we do not have direct confirmason of their SBR performance, they are similar mixing demands November 18, 2014

52 NITRATE AND SOLUBLE COD PROFILE Nitrate and Soluble COD Profile 2/16/2009 Concentration, mg/l NO3-N COD AN Eff MLR AX1 Eff AX2 Eff AX3 Eff Final Eff Location November 18, 2014

53 NITRATE AND BIODEGRADABLE SOLUBLE COD PROFILE Nitrate and Biodegradable Soluble COD Profile 2/16/2009 Concentration, mg/l NO3-N COD AN Eff MLR AN Eff+MLR AX1 Eff AX2 Eff AX3 Eff Final Eff Location November 18, 2014

54 NITRATE REMOVAL Soluble COD consumed in first Anoxic Cell DenitrificaSon in Cells #2 and #3 is driven by endogenous oxygen demand It rained the night before tessng began Incoming carbon affected by fermentason in the sewer high sewer flow strips off slime Mixing versus denitrificason rate was inconclusive because of insufficient carbon November 18, 2014

55 WILO/ EMU MIXERS Wilo was in for a presentason and I gave them the same tank volume used in the previous examples and asked for their mixing recommendasons Basin Volume 19,490 r 3 They responded with 4 different mixer sizings but provided impeller diameter, RPM, direct pumping and power data on each mixer selecson November 18, 2014

56 INVENT MIXERS Just received sizing informason for St Cloud Data include pumping rate, dia impeller, RPM and power draw Calculated Np and Nq values for two different INVENT impeller sizes November 18, 2014

57 THRUST Per meesng with Flygt Momentum = Thrust The momentum generated by the mixer pumping the fluid can be measured by the thrust (force) generated by the mixer on the mixer mounsng November 18, 2014

58 INVENT MIXERS Impeller Dia, ft RPM Hp gpm Np Nq Thrust, Newtons , , , ,729 November 18, 2014

59 COMPARISON TO AXIAL FLOW MIXER MATCHED FLOWRATES LOW INTENSITY Imp Dia, ft RPM Hp gpm Thrust, Newtons Invent , Axial , November 18, 2014

60 COMPARISON TO AXIAL FLOW MIXER MATCHED FLOWRATES HIGHER INTENSITY Imp Dia, ft RPM Hp gpm Thrust, Newtons Invent ,723 1,302 Axial ,781 1,306 November 18, 2014

61 ANOXIC ZONE CELL #1 SAMPLE LOCATIONS Anaerobic Cell #3 Flow to Anoxic Cell #1 Cell #1 First Anoxic Zone MLSS Recycle Flow From Ditch thru deniter gate November 18, 2014

62 ANOXIC ZONE CELL #1 MLSS PROFILE Anoxic Cell #1 Mixer Speed 28 rpm 3,500 3, ,400 5 MLSS, mg/l 3, Largest VariaSon mg/l 3.65% variason 3,300 3,250 3, Depth, ft Location November 18, 2014

63 ANOXIC ZONE CELL #1 MLSS PROFILE Anoxic Cell #1-16 rpm 3,550 3,500 3,450 3, MLSS, mg/l 3,350 3, Largest VariaSon mg/l 8.63% variason 3,250 3,200 3,150 3, Depth, ft Location November 18, 2014

64 M November 18, 2014 l Anoxic Cell #2 Mixer at 8 rpm. NoSce MLSS floc size and some clear liquid zones Anoxic Cell #3 Mixer at 16 rpm. More uniform floc at surface

65 Anoxic Cell #2 Mixer at 8 rpm. NoSce MLSS floc size and some clear liquid zones November 18, 2014

66 Anoxic Cell #1 Mixer at 28 rpm. NoSce MLSS floc size and some clear liquid zones November 18, 2014

67 Anoxic Cell #2 Mixer at 8 rpm. NoSce MLSS floc size and some clear liquid zones November 18, 2014

68 COMPARISON TO AXIAL FLOW MIXER Thrust calculason very much influenced by assumpson of radial flow area Area of flow is not as straight forward as for Axial downpumpers I first assumed a 1 r width of flow off of the radial end of the impeller. Velocity was higher than axial flow so thrust was higher. Increased width of flow Sll thrust matched and got a 2.5 to 3 r band between the two units November 18, 2014

69 COMPARISON TO AXIAL FLOW MIXER - CONCLUSIONS Match direct flow pumping rate Hp sizing is in the same range and much lower than other mixers Must seple flow area issue to be able to compare on a thrust basis November 18, 2014

70 November 18, 2014 MIXER DESIGN COMPARISON l At 80% mixer speed based on the Rogers data, the comparison between the top entering mixer, Flygt mixer, Aqua DDM mixer and Wilo mixer looks reasonable. l The key is to set the right reference point for level of mixing for the calculason of the pumping rate from the top entering mixer.

71 November 18, 2014 MIXER DESIGN COMPARISON l Top entering mixer design should always use a large impeller turning at not more than 15 RPM. l This approach produces a low power consumpson design l Opportunity for mixing energy to impact denitrificason rate requires a facility with plenty of excess carbon.

72 November 18, 2014 MIXER DESIGN COMPARISON l This approach will level the playing field for the various mixer types. l Invent is radial pumping versus axial pumping and unsl we get field data on the area of flow off the edge of the impeller we should compare it to the axial pumpers based upon direct flow.

73 November 18, 2014 MIXER DESIGN UNKNOWNS l The issue of shear and floc size reducson is ssll up in the air. l For floc shearing rather than mix the whole zone at a higher energy input should we focus agitason in a small area and rip the floc apart? l Is VFA/ BOD uptake/ absorpson fast enough to allow a shear zone to be effecsve?

74 November 18, 2014 MIXER DESIGN RESEARCH l SSll need to look for opportunity or do this in lab, to explore mixing energy versus denitrificason rate. l Keep rbcod constant and nitrate constant and vary mixing energy l Use same mixing energies and vary starsng rbcod to see which has bigger impact Carbon or energy

75 ANOXIC ZONE CELL #1 TOUGHEST MIXING APPLICATION Surface entry from Anaerobic Zone Cell #3 MLSS recycle up to 4 Smes influent full depth Both flows are opposing Anaerobic Influent MLSS Recycle November 18, 2014

76 DENITER GATE Gate controls MLSS recycle 3 r wide channel, 18 r deep Ditch flow to aerator MLSS Recycle November 18, 2014