developments for the water and waste industry Presentation by Chemineer low energy mixing Neil Cathie, Sales Manager, EMEAA BHR WWM Open Day

Transcription

1 BHR WWM Open Day Presentation by Chemineer low energy mixing developments for the water and waste industry Neil Cathie, Sales Manager, EMEAA

2 Contents Introduction to Chemineer What we do Low energy and low lifetime cost mixing in water and waste water treatment processes

3 Introduction to Chemineer We are part of Robbins & Myers Inc. Technical sales and manufacturing locations in Derby UK, Dayton and N Andover USA and Suzhou, China. The company was founded in 1952 in the USA and the UK manufacturing started in Agitators, static mixers, high shear rotor stator mixers, spares, service and installation. We provide both process and mechanical warranties. ISO 9001 certified for design, manufacture, testing and sales, Module H of the PED (CE marking), ATEX certified agitators including Zone 0.

4 Introduction to Chemineer Research & Validation Our own corporate research facilities since 1952 with DPIV, LIF,LDA, and pilot scale facilities. Members of BHR s FMP and WWM mixing research consortia for many years. Independent third party validation of static mixer and agitator design performance at both BHR and elsewhere.

5 What we do Research, validate,develop, design, manufacture,test, install and support advanced mixing equipment. Reliability & technology in mixing

6 What we do Static mixers each application is a compromise between pressure loss, mixture quality required and location where required, length, risk of fouling, complexity of injection system. 300mm dia. 1 m/s Delta P, mm of water Mixing length to CoV = 0.05 Tab style m KMS m HEV/WVM m Note mixing length, not mixer length!

7 Agitators are used mainly in Flash mixing for ph or coagulant chemical Flocculation Anoxic/anaerobic Zones Sludge mixing Lifetime cost is and must be a key design parameter for water Utilities.

8 Main Objective : to obtain the maximum flow possible at the least energy input whilst achieving process objectives at minimum lifetime cost. Key process design relationships we have to solve: Power draw P is proportional to N 3 x D 5 Pumping capacity Q is proportional to N x D 3 where :- P = Power [watts] Q = Pumping rate [m 3 /min] N = Speed [rpm] D = impeller diameter [m]

9 Example of a 75 M 3 tank power vs level of agitation rpm '56 rpm 84 rpm 100 rpm Absorbed Power Kw Pumping capacity - m3/min m3/s

10 Two areas where BHR WWM has helped us : Anoxic zone agitator design Sludge mixer design

11 Summary of WWM research into Anoxic Mixer design. BHR objectives in blue, Chemineer experience in red 1. No Oxygenation into the mixed liquor from the surface (surface velocities <0.5 m/s and no visible vortices achieves this) 2. Flow pattern in the tank should approach plug flow (RTD corresponding to 2 tanks in series). (Complete mixed tank using ChemScale of achieves this) 3. T10 (blend time) greater than one tenth of average retention time (easy with 1-3 W/m3 from Lithium tracers tests). 4. Liquor velocity of >0.1 m/s across 90% of the base of zone to minimise deposition. (Practically we can easily achieve m/s over 90% of the bottom with a typical design at 1-3 W/m3) 5. Short-circuiting of less than 5% across the tank (important that inlet and outlets are designed to be alternating up and over and at opposite ends, but easy with blend time <10% of RT). 6. Design verified by CFD modelling

12 Anoxic zone agitator design CFD (top image)equal energy distribution to all corners, highest flow velocities at the bottom to prevent solids deposition. (bottom image) difficult geometry tank with 8:1 L/W ratio but still good flow to all of the bottom.

13 Anoxic zone agitator design : Practical example of agitator in anoxic zone. We now have around 300 installed at UU, Severn Trent, Southern Water sites, plus many overseas. Major sites Minworth, Wanlip, Loughborough, Bolton, Ashton under- Lyne.

14 Energy consumption as per earlier graph, use slow speed, high torque designs with the biggest impellers possible. Variable speed for fine trimming of speed. Long term ragging/fouling - use high shaft Fs (shaft hydraulic load factors), high gearbox service factors, don t load motor too close to its limits. Programmed reverse rotation. Use drywell output shaft gearboxes to avoid need to replace gearbox lip seals, i.e. avoid any gearbox maintenance at all if possible. Anoxic zones life time cost minimisation Dynamic Agitators in water and waste water

15 Anoxic zones - the gearbox oil sealing system. Dry well oil seal, as pictured. No wearing parts, no seal maintenance. A gearbox with lip seals will cost 10-20% less but have a life of 2-3 years before seal replacement. Payback time for dry well output shaft is around 18 months over a 20 year equipment lifetime.

16 Sludge mixer design TR185 has long been know to be inadequate when it comes to the design of sludge pumping systems. The WWM generated sludge database allows us to access rheology data that is critical to the successful design of agitators.

17 Sludge mixer design The data we now have from BHR allows us to use our existing design tools with reasonable reliability. Predicting possible cavern sizes and locations and blend times is now possible.

18 Thank you for listening