Boiler Water Treatment Principles and Practice Volume I Boiler Basics and Steam- Water Chemistry Volume I1 Treatments, Program Design, and Management Colin Frayne CHEMICAL PUBLISHING CO. INC. New York, N.Y ©2002 by Colin Frayne Library of Congress Cataloging-in-Publication Data Frayne, Colin. Boiler water treatment : principles and practice / Colin Frayne. p. cm. Includes bibliographical references and index. ISBN 0-8206-0371-6 1. Feed-water purification. 2. Boilers—Water supply. I. Title. TJ379.F73 2002 621.Γ94—dc21 2002073523 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the publisher and copyright owner. Printed in the United States of America INTRODUCTION: THE FUNCTION OF BOILER WATER TREATMENT AND ITS MARKETING Boilers are heat-transfer devices, wherein water, in the form of either liquid water or gaseous steam, is commonly employed as a medium for the transport of heat to some distant point of use. Although other heat- transfer mediums are sometimes utilized, water is particularly suitable because of its relative abundance, low cost, and high heat capacity. It is generally the medium of choice in most boiler applications, whether for domestic, commercial, institutional, or industrial purposes. However, a boiler can only carry out its primary functions of trans­ ferring heat to water and (in steam generators) separating steam under pressure from water most efficiently if the quality of the various types of water used (such as makeup water, feedwater, and boiler water) are effectively and continuously controlled. The difficulty in this quality control process is that water is a "universal solvent," and as a result, all sources of water contain various natural concentrations of dissolved minerals and gases in addition to suspended solids and biological mat­ ter. The relative amounts of each of these impurities tend to vary con­ siderably with geographic location and season. This phenomenon results in countless permutations of water type and quality around the world, each potentially available as a source of makeup supply to boil­ er plant systems, evaporators, and other forms of water heating and steam generating devices. In many industrial applications, the negative impact of these natural impurities may be further compounded by the presence of small concentrations of process contaminants. The effect of these various impurities or contaminants is to hinder the heat-transfer and steam generation processes, to adversely affect the xvii xviii Boiler Water Treatment: Principles and Practice quality and purity of steam, and to act as primary instigators in the cor­ rosion and wastage of boiler plant system materials of construction. A wide variety of chemical reactions and physical mechanisms can and will take place, including the deposition of various crystalline and noncrys­ talline scales on the waterside of heat-transfer surfaces, the formation of sludges, metal corrosion, and carryover of contaminants into the steam. The function of boiler water treatment, therefore, is to control the waterside chemistry of boiler plant systems within certain agreed and relevant parameters and specifications. As these adverse processes are by no means limited to the boiler itself, in practice, boiler water treat­ ment also includes pre-boiler and post-boiler functions and further requires that all the various types of water utilized are controlled through a comprehensive treatment and proactive management program. Clearly, the lack of or the use of an inappropriate boiler water treat­ ment program creates significant operational difficulties and impacts the economics of the entire process, from start to finish. With regard to the marketing of boiler water treatment programs and services, in the preface to this book I suggested that, although boiler plant can be classified in several different ways, there are from my perspective, only two groups of boiler plant owner/operator to be addressed. 1. The first group consists almost exclusively of the large utility organ­ izations that operate electrical power generation facilities. 2. The second group consists of all the other types of boiler facilities and is clearly a very large and extremely diverse group, utilizing boiler plant ranging from very small steam producers to very large ones and including many that also produce some electricity togeth­ er with process steam. From a water treatment technical and marketing viewpoint, there is, in fact, a fundamental distinction between these two groups, as dis­ cussed below. Utility power generation group: This group of boiler operators typically possess boiler plant installations of complex water-tube con­ figuration, often producing steam in excess of 1,500 to 2,000 psig and increasingly, up to double this pressure. They tolerate only very high- purity makeup (MU) water, use very little chemical treatments, and what they do use is generally of a commodity nature. Internationally, this group has within its ranks an army of experi­ enced chemists and engineers plus a seemingly almost unlimited source of research and development information. Much of this information is Introduction: The Function of Boiler Water Treatment xix tightly held within the international utility power generation communi­ ty and if available in book or other hard-copy form is generally prohib­ itively expensive for outsiders to purchase. The fundamental reason for the commitment of this group to attaining the highest purity of feedwater (FW) and the most exactingly controlled internal boiler waterside conditions is the nature of the primary product made available for sale. This group generates electricity, on which all developed and developing nations critically depend for their economic and social well-being. The production of steam is merely an intermedi­ ate, but the quality and quantities of steam produced has a direct bearing on total electricity output, generation efficiency, operational and mainte­ nance costs, and ultimately the price paid by the consumer. Heating, process steam, and cogeneration group: As a contrast to the utility power generation group, operators of all the other types of boiler plant typically have installations producing steam (or hot water) at very much lower pressures. In fact, most facilities operate boilers somewhere within the range of only 5 to 125 psig, although larger process plants and cogenerators may reach pressures of up to 1,500 psig. Because of the diversity of this group, there is no global standardi­ zation with regard to makeup (MU) water, FW quality, or boiler water (BW) chemistry control, irrespective of boiler design, pressure rating, or ultimate steam purpose. True, there are various national standards and boiler manufacturer association recommendations, and while these guides are extremely useful, they seldom universally agree on any given parameter or protocol. In mitigation, they cannot hope to provide answers to the myriad of problems and specific circumstances that develop. Rather, they should be viewed as a starting point for control purposes. What is clear is that it is seldom that MU water or FW quality (i.e., the lack of contaminants) used by this second group ever reaches the incredible standards demanded and produced by the first group. Indeed, it is not at all uncommon to find lower-pressure boiler installations with MU water and FW both inadequately treated and simply inappropriate to the facilities needs. Low standards of water treatment and waterside chemistry are gen­ erally caused by a combination of bad advice and lack of operator moti­ vation or resources, and provide an initiator for the onset of downstream waterside operational problems. However, despite these apparent water treatment imperfections, most operators somehow still manage to function and produce steam of an acceptable quality and quantity, year after year! XX Boiler Water Treatment: Principles and Practice This second group also, in fact, contains many electricity producers, the so-called cogenerators or combined-cycle plant operators. While there is no apparent clear-cut distinction between these facilities and the large utilities, in practice, the cogenerators tend not to operate at such high pressures (although the generation of power economically usually requires at least 650 psig). Also, although the demands for good quality FW treatment and steam purity in this group is high, it tends not to reach such extremes of sophistication as demanded by the utility group. It can be seen that the first group demands the highest possible qual­ ity of steam purity and steam generation operating control and water­ side chemistry is "knife-edge" technology. Consequently, from a water treatment products and services marketing viewpoint, this group offers the minimum of opportunities as a potential source of revenue. Even where an opportunity exists, perhaps for the supply of a special poly­ meric dispersant or an esoteric oxygen scavenger, the service company may often discover that because of the bureaucratic and accreditation systems to be worked through, the gain may not be worth the effort. Looking further at the second group, although many of the larger, non-utility operators around the world retain a resident water services chemist or trained technician, there is a marked tendency for all own­ ers or operators, whether large or small, to work in conjunction with a water treatment service company. There is also a common purpose to use branded BW treatment chemical products rather than commodities. Thus, a good source of potential revenue for products and services exists in the multitude of smaller boiler-houses to be found operating around the globe. It is here that practical advice is most often needed concerning the suitability and correct application of chemical treat­ ments, the regular interpretation of analytical results obtained, and the strategies to be employed to maximize efficiency and reduce costs. Marketing to this second group is typically based on selling some form of services-based annual contract, using the customers boiler plant operating capacity or potential for steam production as a guide for determining base requirements and for pricing purposes. Hot water heating and LP steam systems are relatively easy to treat, given: • Customer acceptance of the need for treatment (which is not always forthcoming). • An appropriate water treatment program (which is not always pro­ vided, often due to cost issues). Introduction: The Function of Boiler Water Treatment xxi • Some customer/vendor cooperation (which, thankfully, is usually the case). In contrast, the treatment of industrial steam generation plants is usually more difficult. There is a need to conform to a good working standard and to produce quality waterside conditions for a long period of time without serious upsets, as the systems are always very dynam­ ic and operating conditions can continually vary. This is especially the case with those facilities whose manufacturing operations may employ some form of on-off cycle or up-down batching process, rather than a steady-state, continuous production stream. With the smallest heating boilers or low volume/low pressure steam producers, water treatment service companies tend to promote easy-to- understand programs, typically based on only one or two multiple- component, blended chemical products (multiblends or one-drum treatments), or increasingly, the novel crystalline solid concentrates (solid water treatment). These customers often have only very limited, water-related, in-house technical skills, and multiblend product pro­ grams will seem attractive because they are relatively easy to apply. However, the blending process makes it notoriously difficult to control individual component reserves in the boiler and generally adds consid­ erably to the overall program costs. Thus, programs based on multiblends are relatively expensive to use compared with programs based on the use of separate products that are matched to the potential for particular problems identified in a boiler plant. Nevertheless, they remain commonplace for the smallest boiler houses, but as the organizational size of the customer and its volume of daily steam production increases, so the trend for individual chemical treatments on the site tends to predominate. Often, more sophisticated chemical feed and control arrangements are also employed. Traditionally, customers employ water treatment service companies simply as external contractors to assist in the maintenance of clean and efficient waterside surfaces in their various heating, steam generating, cooling, and certain industrial process systems. The customers benefit from genuine improvements in operating efficiency, reductions in main­ tenance time, and replacement component costs. In addition, where industrial processes are involved they often profit from an "added-value," due to an improved product quality or reduction in manufacturing cost. In this external contractor role, water treatment companies providing technical application and problem solving services are required to pos­ sess some general design component and process operating knowledge xxii Boiler Water Treatment: Principles and Practice of all the very many different types of industrial water systems to be found. In addition, they must possess specific and relevant water treat­ ment technical knowledge, together with the practical experience of anticipating and solving water-related problems. Thus, the service companies that can best utilize their "storehouses" of knowledge and provide the necessary customer technical support and practical field skills also tend to gain a good reputation. Ultimately, they generate profit from their solid asset-base of people and knowledge. It is a fact of life that the cost of providing water treatment services increases with the size and complexity of boiler plant. This cost may be recovered with larger boiler plants by the higher volumes of chemical treatments sold, as often the chemical selling prices will include an allowance for all the anticipated (and expensive) technical service time requirements. For smaller chemical volume consumers, especially those with little in the way of in-house BW treatment technical skills, the overall pro­ gram costs can be relatively high. This typically is due to the dispropor­ tionately high requirement for on-site technical service time (including the travel time to and from a customer's site) compared to the volumes of chemical treatment sold. Travel and on-site time is expensive. Typically, the cost of labor and technical service is two to three times the cost of the chemical raw materials used to provide treatments. As a result of the high costs of technical services, most water treat­ ment vendors employ a variety of methods that allows them to charge an economic rate for the programs they sell. They will negotiate a price with the customer based on providing the most suitable balance of on-site service time and chemical/equipment requirements, that anticipates and resolves problems, meets the customers needs, and relieves his or her "pain." Traditionally, a common solution to the problem of matching rela­ tively higher levels of technical support with lower chemical volumes for these smaller customers has been via a one- to three-year, fully inclu­ sive product and services contract. Such a contract will specify the fre­ quency of service visits to be made to the customer's site and the type of work to be carried out. It will also, perhaps, limit the maximum vol­ umes of chemical treatments to be supplied during the contract lifetime, or perhaps designate the amount of chemicals required based on treat­ ing a certain annual volume of boiler FW. Contracts may include for the provision of chemical feed and control equipment and for the supply of labor for boiler cleaning, chemical addition, and drum removal services (drumless delivery). Product and services contract prices may some- Introduction: The Function of Boiler Water Treatment xxiii times be specified as a cost-per-unit of steam produced (i.e., so many cents per 1,000 lb. of steam) or a cost-per-unit of production. Under these conditions, the customer will receive a demonstrable benefit and, provided the on-site time and the volume of chemicals shipped are adequately controlled, the Service Company will derive a satisfactory profit. Nevertheless, and irrespective of the particular mechanisms of pay­ ment for program services rendered, profit and a win-win situation will only arise for both parties if the work performed is managed compe­ tently and in a spirit of mutual cooperation. Thus, if a field representative believes that the task is completed when the testing of water samples is performed and a service report is issued, or if the representative's interpretation of results is poor, prob­ lems will undoubtedly develop. Also, if he or she fails to adequately review the "bigger picture" rather than merely individual results, the problems will magnify and the contract will ultimately be lost. Similarly, if the customer refuses to be involved, at least to some degree, in the ongoing water treatment program or fails to take the advice and undertake necessary actions designed to control the pro­ gram and the boiler system efficiency, the program will again ultimate­ ly fail and the contract will be lost. Today, the traditional view of boiler water treatment (and water treatment in general) is changing. The marketplace is indicating that water treatment is merely part of a more comprehensive technical sup­ port and management services industry for various water, wastewater, and manufacturing process systems. Increasingly, water treatment is widening in scope to support global market demands. It is becoming an outsourcing services business for managing all forms of water, energy, utility, and environmental needs. Even without the current outsourcing trends, it has always been dif­ ficult for service companies to find sufficient numbers of well-trained, experienced, and motivated field representatives. This is because the range of water treatment problems and potential solutions are very wide and the business involves the marketing of many different types of chemicals and equipment, coupled with consulting work and inno­ vative trouble shooting. In the water treatment industry, the first line of service providers has always been the vendor's technical sales representatives, who, for the most part, are chemists, engineers, microbiologists, or similarly trained people. The field representatives typically rely on a combination of their primary disciplines and a depth of water treatment problem-solving xxiv Boiler Water Treatment: Principles and Practice experience to overcome technical and operational problems and also add value to their customers operations. But in today's global economy, the sheer permutation of available niche services, the growing demands for both outsourcing of non-core utility functions, and economic fine-tun­ ing, requires that water treaters now commonly have to additionally act as managers and administrators of their customers entire water system facilities. Today, water treatment companies sell environmental reassurance and technology-based utility support services, not chemicals or equip­ ment. Boiler water treatment is now an energy management function. And while the business and practice of this industry may be well over 100 years old, it remains a vitally important function and is a cornerstone of the global industrial services market.