OPTIDOSE 1000 Traceable Polymer A Tool for Maintaining Maximum Heat Transfer

Transcription

1 Technical Data Sheet OPTIDOSE 1000 Traceable Polymer A Tool for Maintaining Maximum Heat Transfer Description OPTIDOSE traceable polymer technology is a revolutionary method of tracking polymer levels in cooling water, boiler feedwater, and other aqueous systems that use polymer for scale inhibition. Developed by Dow, the system uses a "tagged" polymer that can be identified with a simple field test. The test measures the level of free polymer in the water so that the system operator knows exactly how much active polymer is available to combat scaling and corrosion. In addition, the test can be used as a tool to help determine the course of action to follow during upset conditions. OPTIDOSE 1000 polymer is a low-molecular-weight traceable polyacrylic acid. It helps prevent the deposition of calcium carbonate, calcium sulfate, barium sulfate, and other lowsolubility salts on heat exchanger surfaces. OPTIDOSE 1000, the tagged (traceable) version of ACUMER 1000 polymer, is an ideal choice for systems that need frequent monitoring because of the possibility of upset conditions. Advantages of OPTIDOSE 1000 Feature Service Company Benefit End User Benefit Tagged polymer technology Ability to monitor free polymer in system Ability to optimize polymer dosage Measure only free polymer level Tagged polymer performance equivalent to untagged version Simple, easy-to-perform field test Complies with U.S. FDA Food Additives Regulations for paper, paperboard and boiler applications Ongoing measurement of free polymer for a better understanding of system Early warning of fouling and corrosion before it occurs Minimize cost without risking failure Better control of key system parameter Direct fit into existing formulations using untagged ACUMER polymers Minimize time and expense of testing Wider spectrum of customers and applications Fewer calls required, saving customer s money Maintain clean heat transfer, maximize equipment life Less likelihood of loss of production due to failure Greater confidence in system capability Experience with ACUMER 1000 still relevant System operator can monitor polymer levels Technology available for use in food applications Page 1 of 9 OPTIDOSE 1000 Traceable Polymer 07/2012, Rev. 0

2 Maintaining Maximum Heat Transfer As a result of a series of tests run by Dow in the pilot cooling towers in Spring House, Pennsylvania (USA), some conclusions can be reached about the effect of OPTIDOSE 1000 polymer levels on heat transfer. A minimum free polymer level of approximately 8 ppm OPTIDOSE 1000 was required in the tested cooling water system (Zn-phosphate program, ph 7.7) to maintain maximum heat transfer and avoid fouling conditions that lead to loss of heat transfer efficiency. At free polymer levels of 6 ppm and below, fouling on heat transfer surfaces caused a definite drop in heat transfer. To assure a safety margin, 10 ppm free polymer was maintained as a minimum level. Figure 1 shows the heat transfer as a function of free polymer level. Attacking the Problem of ph Upset conditions are always a concern in the operation of a cooling system. One type of upset that has the potential to create major problems in heat transfer equipment is a ph excursion, where the ph suddenly drops drastically below normal operating parameters. There are a number of possible causes for such a decrease, e.g., an accidental discharge of acid into the cooling system or a ph-controller failure. A series of ph excursion tests using the Zn-phosphate program were run by Dow laboratories to determine the effect of ph problems on polymer levels and, ultimately, on heat transfer. The results show that use of the OPTIDOSE test kits during upset ph conditions can supply the system operator with valuable data that can indicate not only the course of action to be taken, but also quantitative values for correction of the problem. The tests also clearly demonstrate that the action taken during a ph excursion can substantially impact the amount of fouling that ultimately occurs. A Procedure for ph Upsets Using OPTIDOSE 1000 as a Tool to Determine Corrective Action Two pilot tests were run in systems that had been in use for some time and thus had some scale on the heat exchangers. The ph was intentionally lowered for 4 hours by the addition of acid (H 2SO 4) to the system. Steel coupons were also added to simulate a mild steel system (the pilot system has a copper heat transfer surface). Page 2 of 9 OPTIDOSE 1000 Traceable Polymer 07/2012, Rev. 0

3 A Procedure for ph Upsets Using OPTIDOSE 1000 as a Tool to Determine Corrective Action (Cont d) A Better Way to React The first observation noted was that the acid conditions caused a small increase in polymer level and a large increase in the level of Fe +3 ions in the water, indicating rapid corrosion of equipment. The initial impulse of an operator might be to correct the ph immediately in order to minimize corrosion of the metal components of the cooling system. However, adding base to the acidic water causes formation of particles that consume free polymer. If the polymer level drops too low, scaling and a long-term loss of heat transfer efficiency will probably occur. In pilot test #1, while the system was still at low ph, a sample was taken for laboratory evaluation using the OPTIDOSE test kit. This allowed the operator to run a quick series of tests to guide the corrective actions needed. Specifically, these tests can determine the slug of polymer that should be added before ph adjustment to stop the free polymer from dropping below maintenance levels. This procedure can help prevent scaling of the system. A sample of the low-ph cooling water was treated in the laboratory by raising the ph to 7.7 and heating at 60 C to simulate the elevated temperature and dynamic conditions in the pilot system. The free polymer level was measured and found to be about 2 ppm, a loss of 10 ppm. Thus a slug of at least 10 ppm active polymer is required to assure that the free polymer will not drop below a predetermined minimum of 10 ppm. To allow a 50% safety margin, a slug of 15 ppm should be added. This conclusion was verified in a repeat bench test, where a 15 ppm polymer slug was added to a fresh sample before adjusting the ph to 7.7. The result showed that the free polymer level stayed above 10 ppm after the ph adjustment. Using the bench test data as a guide, a 15 ppm polymer slug was added to the pilot system before raising the ph back to the normal operating level. The free polymer decreased after the addition of the base, but only back to approximately the maintenance level, as predicted by the bench tests. Because the free polymer did not go below the required level, scale did not form, and heat transfer was maintained at about 100%. The turbidity of the water increased, but there was enough polymer present to disperse the solids and prevent deposition on the heat transfer surface. The results of pilot test #1 are shown in graphical format in Figure 2a. A Wrong Way to React The bench tests predict a low polymer level if a polymer slug is not added before readjustment to normal ph. Scaling and a decrease in heat transfer efficiency may result from inadequate polymer. This scenario was verified in pilot test #2. After 4 hours, NaOH was added to bring the system back to normal operating ph as quickly as possible, but no polymer slug was added. After this was done, the polymer level rapidly declined to less than the minimum required amount. Heat transfer in the system dropped off and stabilized at approximately 86% of initial heat transfer. The system also became turbid, and the low polymer level was apparently inadequate to prevent deposition. The results of pilot test #2 are illustrated in Figure 2b. Page 3 of 9 OPTIDOSE 1000 Traceable Polymer 07/2012, Rev. 0

4 A Wrong Way to React (Cont d) Summary of Procedure to Recover From a ph Excursion Measure free polymer level in a sample of low ph cooling water. Add base to the sample to raise the ph back to proper operating level. Filter and remeasure free polymer level. Subtract to find the ppm of polymer lost. Slug feed to the cooling tower the ppm lost plus 50%. Add base to the cooling tower to raise the ph back to proper operating level. Page 4 of 9 OPTIDOSE 1000 Traceable Polymer 07/2012, Rev. 0

5 Results and Conclusions Table 1 shows the results of the bench testing. Data from a cooling water sample taken before the ph excursion are included for comparison. Table 1 Bench Test Results (with and without 15 ppm OPTIDOSE 1000 slug) Before Excursion During Excursion After Excursion ph (both tests) 7.8 ~4 7.7 Fe, ppm (both tests) Free polymer level, ppm (Polymer slug added during excursion) Free polymer level, ppm (Polymer slug added during excursion) 12 Before slug 15 After slug Table 2 contains a summary of observations and conclusions from the pilot and bench tests. Table 2 Observation and Conclusions ph Excursion Observation Increase in Fe +3 ions in cooling water Initial increase in free polymer level Rapid decrease in free polymer level after ph adjusted up Turbidity of water after return to ph 7.7 Conclusion Corrosion is occurring rapidly due to the low ph. The acidity of the water causes some of the scale already in the system to dissolve, releasing some bound polymer to free. The precipitated solids from neutralization immediately bind up free polymer. Precipitated solids adsorbed and suspended by free polymer. This can be treated by increasing blowdown to improve turbidity. Properties A series of bench tests has been performed by Dow laboratories on OPTIDOSE 1000 to assure that it is the equivalent in performance to its untagged counterpart, ACUMER Figure 3 shows kaolin dispersancy of ACUMER 1000 (untagged) and OPTIDOSE 1000 (tagged), as well as several other products. It is clear that ACUMER 1000 and OPTIDOSE 1000 are indistinguishable from each other. These two products are also more effective in performance than higher molecular weight paa polymer (ACUMER 1100), phosphinopolycarboxylic acids, and commercially used HEDP. CaCO 3 inhibition is shown in Figure 4. Again, ACUMER and OPTIDOSE 1000 polymers perform equivalently to each other, and approximately equivalently to HEDP and phosphinopolycarboxylic acid. They outperform ACUMER 2000 copolymer and ACUMER 1100, a higher molecular weight polyacrylic acid. Figures 5 and 6 show the adsorption of OPTIDOSE 1000 on kaolin and CaCO 3. It should be noted that while adsorption increases rapidly at low concentrations of polymer, it tends to plateau in the range of about 3 ppm. As above, the tagged and untagged versions (OPTIDOSE and ACUMER 1000) perform approximately equally. Page 5 of 9 OPTIDOSE 1000 Traceable Polymer 07/2012, Rev. 0

6 Properties (Cont d) Page 6 of 9 OPTIDOSE 1000 Traceable Polymer 07/2012, Rev. 0

7 Properties (Cont d) Typical physical properties of OPTIDOSE 1000 are shown in Table 3. Table 3 Typical Physical Properties These properties are typical but do not constitute specifications Appearance Total solids, % Active solids, % 44 Clear solution ph Molecular Weight* Weight Average, Mw 2000 Number Average, Mn 1425 Density, lbs./gal. at 25 C (g/cc) 10.3 (1.2) Brookfield Viscosity, cps. at 25 C Lbs (Kg) NaOH (50%) to Neutralize 1 lb. (kg) of as-is product *Measured by aqueous GPC and reported as acid form FDA Clearance OPTIDOSE 1000 polymer complies with the U.S. Food and Drug Administration (FDA) Food Additives regulations indicated below provided that the final formulation meets the extractive limitations and other conditions prescribed by the regulation. Regulation Number Title of Application OPTIDOSE Boiler-water additives X a Adhesives X Components of paper, paperboard in contact with aqueous and fatty food Components of paper, paperboard in contact with dry food X a Only if converted to sodium salt. b Only if converted as a sodium salt as: 1. a pigment dispersant in coatings at a level not to exceed 0.25% by weight of the pigment. 2. a thickening agent for natural rubber coatings, provided it is used at a level not to exceed 2% by weight of the total coating solids. X b Page 7 of 9 OPTIDOSE 1000 Traceable Polymer 07/2012, Rev. 0

8 Suggestions for Field Evaluations of OPTIDOSE 1000 In rare instances, recirculating water containing no OPTIDOSE might give a false positive test result. To assure accurate strip test results, the following procedure should be followed before beginning treatment with OPTIDOSE ) Before adding OPTIDOSE 1000, obtain a sample of the recirculating water and use the strip test to ensure that no false positives occur. 2) Add a known amount of OPTIDOSE 1000 to a portion of the sample. Use the test kit to measure the polymer level. If the level is lower than the amount added, the water has a polymer demand, probably from particulate matter. Polymer demand may indicate that the existing program is not being fed at a high enough level to prevent fouling. 3) If there is a polymer demand, filter a fresh portion of the sample and repeat step 2 to demonstrate that solids in the water are causing the demand. For a complete set of field protocols, contact your local Dow technical representative. Test Conditions Pilot Cooling Tower Makeup water ppm Ca, 50 ppm Mg, 100 ppm M-Alkalinity (all as CaCO 3) Cycles of concentration Formulation feed - 5 ppm phosphate, 2 ppm zinc, 8 ppm Optidose 1000, 3 ppm tolyltriazole ph 7.7 Heat Exchanger F (54 C) Cooling tower F (43 C) Kaolin Dispersancy 1000 ppm Hydrite UF kaolin 200 ppm Ca (as CaCO 3) ph hour settling time/room temperature Measure turbidity of top 20 ml of 100 ml sample Calcium Carbonate Inhibition 632 ppm Ca, 316 ppm Mg, 632 ppm M-Alkalinity (all as CaCO 3) ph F (54 C)/20 hours Filter through 0.22 micron filter Measure Ca in filtrate Kaolin Adsorption 1000 ppm Hydrite UF kaolin 150 ppm Ca, 100 ppm Mg, 125 ppm M-Alkalinity (all as CaCO 3) ph hour 15 minute contact time/room temperature Calcium Carbonate Adsorption 2000 ppm precipitated CaCO ppm Ca, 100 ppm Mg, 125 ppm M-Alkalinity (all as CaCO 3) ph hour 15 minute contact time/room temperature Page 8 of 9 OPTIDOSE 1000 Traceable Polymer 07/2012, Rev. 0

9 Handling Precautions Storage Disposal Considerations Before using this product, consult the Material Safety Data Sheet (MSDS)/Safety Data Sheet (SDS) for details on product hazards, recommended handling precautions and product storage. Store products in tightly closed original containers at temperatures recommended on the product label. Dispose in accordance with all local, state (provincial) and federal regulations. Empty containers may contain hazardous residues. This material and its container must be disposed in a safe and legal manner. It is the user's responsibility to verify that treatment and disposal procedures comply with local, state (provincial) and federal regulations. Contact your Dow Technical Representative for more information. Product Stewardship Customer Notice Dow has a fundamental concern for all who make, distribute, and use its products, and for the environment in which we live. This concern is the basis for our product stewardship philosophy by which we assess the safety, health, and environmental information on our products and then take appropriate steps to protect employee and public health and our environment. The success of our product stewardship program rests with each and every individual involved with Dow products - from the initial concept and research, to manufacture, use, sale, disposal, and recycle of each product. Dow strongly encourages its customers to review both their manufacturing processes and their applications of Dow products from the standpoint of human health and environmental quality to ensure that Dow products are not used in ways for which they are not intended or tested. Dow personnel are available to answer your questions and to provide reasonable technical support. Dow product literature, including safety data sheets, should be consulted prior to use of Dow products. Current safety data sheets are available from Dow. Contact: North America: Latin America: (+55) Europe: (+800) (Toll) Asia-Pacific: (+800) (Toll) NOTICE: No freedom from infringement of any patent owned by Dow or others is to be inferred. Because use conditions and applicable laws may differ from one location to another and may change with time, Customer is responsible for determining whether products and the information in this document are appropriate for Customer's use and for ensuring that Customer's workplace and disposal practices are in compliance with applicable laws and other government enactments. The product shown in this literature may not be available for sale and/or available in all geographies where Dow is represented. The claims made may not have been approved for use in all countries. Dow assumes no obligation or liability for the information in this document. References to Dow or the Company mean the Dow legal entity selling the products to Customer unless otherwise expressly noted. NO WARRANTIES ARE GIVEN; ALL IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED. Page 9 of 9 OPTIDOSE 1000 Traceable Polymer 07/2012, Rev. 0