The Precipitant Online - November 1997 Edition

Optimizing Inhibitor Blends Using Computer Modeling,  NACE International, Paper 07061, Corrosion/2007

Anatomy of a Multifunctional Product, Association of Water Technologies, 2006.

Abstract: Multifunctional cooling water products address scale and corrosion control and include blends of inhibitors in “one drum”. Less than optimum ratios of inhibitors can result in product overfeed, increased costs, and in some cases, inhibitor induced fouling. This paper describes the use of computer modeling to optimize ratios of scale and corrosion inhibitors for different waters.

The Practical Application of Ion Association Model Saturation Indices to Commercial Water Treatment Problems, American Chemical Society, 1994

Abstract: Ion association models predict the equilibrium distribution of species for a cooling water, oil field brine, waste water, or other aqueous solution of commercial interest. Scale potential indices based upon the free ion concentrations estimated by ion association models have been used extensively in the past decade to predict scale problems in industrial cooling water systems. They have overcome many of the problems encountered with simple indices which do not account for ion pairing. This paper discusses the application of ion association model saturation level indices to predicting and resolving scale formation problems in cooling water systems, oil field brines, and for optimizing storage conditions for low level nuclear wastes.

Computerized Ion Association Model Profiles Complete Range of Cooling System Parameters, International Water Conference, 1991

Abstract: This paper describes the application of a microcomputer (PC) based software system to establishing operating parameter limits for open recirculating cooling systems. The software used evaluates recirculating water chemistry over the typical, user defined, operating range of concentration ratio, temperature, and pH to provide an in-depth, panoramic estimation of deposition potentials. The deposition potentials calculated for a cooling water are based upon the free concentration of reactants and account for common ion effects. The approach of profiling the entire operating range using an ion association model overcomes two criticisms of water chemistry evaluations and their applicability towards predicting scale problems in a system and comparing indices versus results between cooling systems.

Developing Scale Inhibitor Dosage Models, WaterTech 1992, NACE Europe 1992

Abstract: feeding the minimum effective inhibitor dosage can reduce operating costs for chemical treatment, minimize treatment chemical discharge to the environment, and in some cases, prevent under­feed of a scale inhibitor. Common sense indicates that the same scale inhibitor dosage is not required for all waters and systems. One size does not fit all. This paper discusses the parameters critical to developing an effective dosage modulation model for scale inhibitors from laboratory data, field data, or a combination of both. The paper draws upon the concept of induction time as a basis for the mathematical models used to develop predictive models from actual data. The models are based upon the concept that threshold effect inhibitors do not prevent scale formation, they only delay the inevitable. The models are in agreement with current theories and treat scale inhibitors as agents which extend the induction time before crystal formation and/or growth on existing active sites occurs in the case of calcium carbonate, and as dispersants which control particle size in the case of calcium phosphate.

Developing Corrosion Inhibitor Dosage Models, WaterTech 1992

Abstract: Few tools are available for direct use by the cooling system chemist for the prediction of corrosion rates in the presence and absence of corrosion inhibitors. The models which are available are used primarily by research laboratories and the water treatment service companies as a service to their customers. Models which predict the performance of a corrosion inhibitor versus inhibitor dosage can be used to establish the economics for treatment to a given corrosion rate target. At a minimum, such models could provide information on the relative treatment costs for achieving 1 mpy in a system, 2 mpy, 5 mpy or other targets.

The wide spread use of personal computers and the availability of PC based software have provided the cooling water chemist with a method for in-depth water chemistry evaluation, and for the application of statistical methods to modeling historical data bases of treatment results versus water chemistry, operating parameters, and treatment levels.

Model development requires a baseline method for predicting the untreated corrosion rate as well as models for predicting the corrosion rates in the presence of inhibitors.

A Multifunctional Additive For Deposit Control, Corrosion '96

Abstract: Laboratory studies were conducted to profile the performance of a new scale inhibitor and to compare its performance to commonly used inhibitors. A software package was used to optimize the experimental design and minimize the number of test required to develop a complete performance profile. This paper outlines the results of the study.

Modeling Scale Inhibitor Dosages For Oil field Operations, Corrosion '94

Abstract: Mathematical models for predicting the minimum effective dosage for scale inhibitors have been used successfully to optimize treatment levels in field applications. The models were developed in the format of minimum effective dosage as a function of water chemistry, temperature and time. This paper describes the use of laboratory and field data to develop the models.

A Comparison of Scale Potential Indices With Treatment Program Results in Ozonated Systems, Corrosion '93

Abstract: Ion association model saturation levels were calculated for ozonated cooling systems. This paper compares treatment program results, including deposits present, to indices calculated for calcium carbonate and other scale forming species typically encountered in cooling systems.

Predicting Calcium Oxalate Scale, Corrosion '2002

Abstract: Calcium oxalate scale is frequently encountered in the sugar refining and paper making processes. This paper outlines a simple index for the prediction of calcium oxalate scale. The development of a more refined index, based upon free ion concentrations, is also discussed.

Thirty Years of Ultra Low Dosage Scale Control, Corrosion '2003

Abstract: Utilities were confronted by a major cooling water treatment challenge in the 1970’s. Central station power generation units were built with man made lakes for condenser cooling in the previous decades. These lakes concentrated with time creating a calcium carbonate scale problem in the once through cooled surface condensers and auxiliary cooling systems. In some cases, the problem was further aggravated and accelerated by the addition of multiple power generation units to the lakes, well beyond the original design specifications.

Condenser scale caused increased back pressure in the turbines, increased heat rate, and in many cases, deration. Traditional once through cooling water scale treatment approaches could not economically control the scale. Cost for treatment using the one(1) to nine(9) mg/L dosage rates for polyphosphate based scale control agents common at the time for once through scale control, were higher than the cost of increased fuel consumption and lost production capability. This paper describes the evolution and history of an economical treatment approach for high volume utility once through cooling systems based upon polymers and phosphonates. The theoretical and practical application of dosage optimization models used to modulate the inhibitor dosages is discussed in detail. The system described, or derivatives of it, are commonly used today for high volume utility once through scale control.

Water Treatment Rules of Thumb, (Paper) Association of Water Technologies, 2003

Abstract: Water treatment chemists have used simple rules of thumb and indices since the early days of water treatment. The rules and indices are used to predict scale formation and in many cases, to determine the maximum concentration ratio for a tower’s operation, and the control pH. Indices and rules of thumb are a way to estimate scale prediction when more rigorous, and accurate, methods are not available or practical. The availability of high powered Pentium class calculation power, and ion association model software for water chemistry modeling and prediction, have made more precise calculations economical for even the smallest water treater.

This paper reviews common water treatment rules of thumb, their origin, and compares them to ion association model saturation indices. Such a comparison reveals the general applicability and limitations of rules of thumb and simple indices. Where applicable, Rules of thumb are presented as summarized in the Association of Water Technologies Technical Reference and Training Manual.

Water Treatment Rules of Thumb, (Slides) Association of Water Technologies, 2003

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