SRAPPA 2014 Moving Forward in the 21st Century 63rd Annual Conference Marshall University, Huntington, West Virginia
LaMotte Water Management and present
Energy Conservation Through the Removal of Bio-film The intent of this study is to demonstrate the impact of biofilm on water cooled condenser heat transfer surfaces in an electric driven chiller plant and the associated increase in electrical usage.
Green Technology by Zentox
The demonstration is a study of the use of Ozone as a stand alone treatment system to provide superior Bio-film control and resultant increase in heat transfer efficiency. The study will measure Fouling Factors and Bio-film on operational water chillers.
Process Description Tower water is recirculated from/to the tower sump in a bypass loop Tower water is dosed with Ozone in the recirculating loop Ozone is manufactured on site by feeding dry, oxygen rich gas to a plasma block Ozone generator Ozone gas is drawn into the bypass loop by negative presure via a venturi Ozone production is regulated by a feedback loop from an ORP sensor ORP set point is maintained by varying electrical charge in the Ozone generator Conductivity of the cooling water is controlled by a TDS/Conductivity monitor and bleed valve Conductivity set point is calculated to maintain Langelier Saturation Index and Phosphate Saturation Point
Process Description Monthly service requirements On site make-up water and tower water chemistry Clean ORP probe Test oxygen generator feed gas concentration Visually inspect cooling tower Check Approach Temperature Optical Bacteria and/or Corrosion Coupon Testing
Washington & Lee University Chiller Plant Study System Components Ozone Treatment Package Two 300 gpm circulation pumps Four Oxygen generators providing 36 LPM Two Plasma Block Ozone generators providing 120 gm/hr ORP controller for linier control of Ozone production pH Control Replace 66˚ Baume` Sulfuric Acid with CO2
Washington & Lee University Chiller Plant Study Facility 4 Electrically Driven Chillers 3 – 1,200 Ton Chillers 1 – 600 Ton Chiller 1 Flooded Sump, Field-erected, Ceramic Counter Flow Tower augmented by a dry sump Evapco cross-flow tower Water Supplied by City Water and 2 Auxiliary Wells Controlled with 2 level controls with well water always the primary source. City water designed to supliment when wells can not keep up with evaporation
Why use Fouling Factor? Our primary concern is Bio-film and it’s ability to foul and insulate condenser tubes. With measured and recorded Fouling Factor we get demonstrable, not theoretical, energy savings.
Fouled vs. Clean
Concept for Use of Fouling Factor The Fouling Factor is independent of loadings, demands and degree days. Less Bio-film on the tubes, lower Fouling Factor with measurable improvement on heat transfer and energy consumption.
The Fouling Factor Formula Used F (Fouling Factor) = 1/U – 1/Uc Where U is the Heat Transfer Coefficient and the Clean/New Heat Transfer Coefficient respectively. U = Q/(A x F x LMTD) is used to calculate the actual Heat Transfer Coefficient Where Q is the Condenser Load, A is the Condenser Heating Area, F is the Temperature Correction Factor, and LMTD is the Log Mean Temperature Difference.
Significance of Bio-Film to Energy Loss Old thinking: Bio-film was a concern. Current understanding: New data and studies indicate that Bio-film is the single biggest contributor to energy loss.
Power of Bio-Film Bio-film is almost 5 times more insulating that scale. Thermal Conductivity Calcium Carbonate 2.6 Calcium Phosphate 2.6 Calcium Sulfate 2.3 Iron Oxide 2.9 Bio-film 0.6
Porous Mixture of Organic and Inorganic Material
Ozone Bio-film’s Worst Enemy Biofilm Prevention and Removal Ozone Bio-film’s Worst Enemy
What is Ozone? 03 - an unstable form of oxygen with three atoms Powerful oxidizing biocide 500% more effective than chlorine Short life in evaporative cooling water (around 20 minutes) Environmentally Safe- breaks down to oxygen
Biofilm Prevention and Removal Keep system clean Mechanically- physical removal Chemically- micro-biocides, dispersants Reduce Food Filtration Oxidation Location of Equipment Process Leaks
Biological Control and Standards Chemically – must use dual biocide program to prevent development of immunity Standard – maintain growth below 10,000 CFU (Colony Forming Units per ml) Ozone – uses cold combustion to destroy cell wall and oxidize waste – impossible for bacteria to develop immunity Standard – maintain growth below 100 CFU
Data Collection Fouling Factor Bio-film Data collected prior to changeover to Ozone Data collected after changeover to Ozone Bio-film Readings collected with the use of a coupon and results from a 15 minute reaction – all readings in BMR, or Bio-Mass Reading Range – from <0.2 indicating no problem to >4.0 indicating severe Bio-fouling Average readings prior to changeover to Ozone Average readings after changeover to Ozone
Data Points, Calculations and Display The Chiller Plant maintains sensors on the Chillers installed to monitor all necessary data – system temperatures, lift, approach temperatures – necessary to calculate the FF. Since some of the necessary constants are considered proprietary by the Chiller manufacturer, they have built the calculation into their programming so that we can log FF for before and after comparison. The data collection software provides a readout of this calculated number on the Dashboard of the University’s monitoring programs, allowing University personnel to see the FF at any given time.
BioMass Readings - Biofilm Testing Washington & Lee University Chiller Plant Lexington, VA Before Ozone Treatment After Ozone Treatment Date BMR Coupon Location 12/27/2011 1.03 1 1/10/2012 0.71 2 1/24/2012 0.31 2/14/2012 2.27 3/8/2012 0.88 3/15/2012 0.47 4/18/2012 2.11 5/8/2012 2.08 6/4/2012 1.72 6/15/2012 1.36 7/13/2012 0.49 * * Acid over feed on day of sample - pH at 5.0. Removing this reading results in an average BMR of 1.38 7/25/2012 0.72 8/21/2012 1.26 9/12/2012 10/3/2012 *** *** Turned on Ozone system 10/13/2 10/22/2012 0.26 11/28/2012 0.19 12/11/2012 0.16 1/16/2013 0.17 3/12/2013 0.67 4/15/2013 0.28 5/1/2013 0.79 5/16/2013 1.31 5/29/2013 1.33 6/18/2013 4.02 ** **Allowed Bromine to run out 7/1/2013 7/16/2013 0.55 8/1/2013 0.85 8/13/2013 *** Turned on Ozone system 8/13/13 9/5/2013 9/17/2013 0.33 10/3/2013 0.41 10/23/2013 11/20/2013 1.16 Average Biofilm Reading Before Ozone 0.29 Average Biofilm Reading After Ozone 1.29 Average Biofilm Reading During Chemical Re-evaluation Average Biofilm Reading After Ozone Re-start
Program Results Electrical Savings of 3.58% Fouling Factor Improvement of 17% Over Chemical Program Significantly Higher Savings When Chiller Load Above 840 Tons (on a 1200 Ton Chiller) Bio-film Readings Significantly Reduced Corrosion Rates Maintained in the Excellent Range Eddy Current Test Results Identify No Impact Results of Test Backed by Excellent Copper Corrosion Results
Picture of W&L Dashboard
Chiller Tonnage vs Fouling Factor
Chiller Tonnage vs Fouling Factor
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