Water treatment: striking a balance.
Solutions! for People, Processes, and Paper, the official magazine of TAPPI and PIMA, gave several industry experts a chance to offer their viewpoints on how mills can manage costs while managing their chemical programs. While their opinions sometimes differ, support is unanimous for the notion that water chemistry is a too-often neglected area of pulp and paper mill operations.
"I see every day how many paper mills neglect water treatment and management generally minimizes any capital budget related to water to unrealistic levels which are totally unrelated to the savings and advantages possible," said Len Dewhurst, director of sales, Asia region, ALGAS Fluid Technology Systems AS, Moss, Norway. "Efficient water treatment can save more in raw materials, chemicals and power and reduce operating costs than any budget committee could dream of or understand."
COST AND EFFECT
Higher prices for chemical feedstocks have led to major increases in water treatment chemical prices. Naturally, mills are concerned with managing the higher costs; but they need to be careful, our experts warned. Considering water chemistry's pervasive influence throughout the mill, the best strategies for mills that want to manage higher chemical costs are strategies that actually look beyond chemical cost.
George Totura, program manager, water management for Naperville, Illinois, USA-based Nalco, noted that many other cost increases, such as energy costs, have a much bigger impact in the mill. "Our clients are asking us to deliver more than just chemicals," he said. "They want us to take on a consultative role to support the efforts of their mill teams, helping them optimize resources such as water and energy. This often results in cost savings far above and beyond the cost of chemicals."
Jim Graham, water treatment specialist for papermaking technologies, Buckman Laboratories International, Memphis, Tennessee, agreed. "By some estimates, energy represents over 20% of the cost of manufacturing paper, while chemicals represent less than 5%," he said. "Managing a chemical treatment program includes accounting for factors that can directly affect costs. For example, the use of a mill water corrosion inhibitor program may increase as more water is recovered for reuse in the mill, but the increased cost may pale in comparison to the savings realized by the recovered BTU value of the water. Another example may be in the waste treatment area. Many problems can be eliminated by control of the key growth pressures in an activated sludge system. Proper attention can minimize the need for supplemental programs to address odor issues, filamentous bulking of the sludge and excessive TSS and foaming in the effluent."
Equipment design is another area that mills should explore. If water quality can be improved by mechanical means, the bottom line may benefit from a reduced need for treatment chemicals. "Examples include the use of membrane technology to further purify water and reduce the potential for deposition in boilers or membrane technology to remove otherwise troublesome species that might require treatment, and conversion from sodium-cycle softeners to demineralizers to produce boiler feedwater makeup," said Norris Johnston, applications team manager-water management technology, Hercules Pulp and Paper Division, Lacey's Spring, Alabama. "Another method might include changing chemical treatment programs to those that offer advantages with regard to system hydraulics, which can ultimately reduce the volume to be treated and therefore the chemical use."
Examples include the use of a more stable boiler water dispersant, for higher cycles and less boiler blowdown; or conversion to deposit control technology in recirculating cooling systems that tolerates higher dissolved solids, for less cooling tower blowdown, according to Johnston.
Careful monitoring can help mills minimize cost by minimizing chemical use. "There are many examples of mills that 'set it and forget it,' leading to both over- and under-treatment of the specialty chemical as the process changes," warned King. "Monitoring can be in the form of personal observation, off-line testing, or on-line monitoring." For instance, operators can observe clarifier and lagoon operation, and adjust chemical flow accordingly; lab work can include checking influent and effluent for flotation/settling rates, turbidity, charge, pH, conductivity, solids, sludge moisture, and color; and successful on-line testing includes turbidity, charge, pH, conductivity, color, through put flows, and solids content, King said.
Mills that are open to new ideas may be able to work with chemical suppliers to find innovative strategies for managing costs. "Most mills are already beginning to consider application costs, rather than chemical additive costs," said Roland Pelzer, PL Paper/head of sales Europe, for Degussa Water Chemicals, Krefeld, Germany. "Since suppliers do not have any more space in their price calculation, reduced costs will not come by changing suppliers but keeping the same chemical program--which is the demand rather often, if mills invite suppliers for their bid.
"Mill technicians need to be involved, and new ideas/programs need to be evaluated together," he continued. "This does not always mean that the chemistry has to be changed totally. In most cases the new idea will be just to apply new things that have been learned--for instance, changing dosing points or dosing order, or improving dosing technology, together with a modified chemistry. Even if the mill is satisfied with its current water treatment program, a survey should be repeated every two or three years."
A thorough process audit of current conditions can help mills assure optimum polymer selection, chemical addition points, and process control technology, said Irenee Philippe, director of technology, Ciba Specialty Chemicals, Suffolk, Virginia, USA. "Polyacrylamides are a major chemical component for clarification and sludge dewatering in paper mill water treatment applications. Propylene, an oil-based derivative, is a key building block for these polymers and a good benchmark for price indexing." Philippe also suggested that a fixed cost treatment program (figured, for instance, on the cost per unit of treated process effluent) is another novel strategy to consider.
A SMOOTH TRANSITION
Cost pressures are only one catalyst that can lead to a mill's decision to change water treatment programs. Whether the mills' prime motivator is cost, quality, or new mechanical requirements, any change to a treatment program requires forethought and care during transition. Some situations may require only minor adjustments; others, major overhaul. Either way, proper planning in concert with the chemical supplier is the surest way to success, say our experts.
"Risk can be minimized when transitioning to a new water treatment program through careful supplier selection, development of a clear transition plan with agreeable and achievable goals, and a well thought out contingency plan for managing the unexpected," said Ciba's Philippe "Successful transition plans balance the risks and benefits. For example, to offset the higher prices associated with oil-based raw materials, energy, and transportation costs, a commonly used, low risk tactic is to transition from oil/water liquid emulsions to 100% active dry polymers. This transition offers the added benefit of reduced volatile organic compounds."
According to Hercules' Johnston, the onsite water treatment consultant should be willing and able to prescribe a transition process that minimizes risk while accomplishing the transition in a timely manner. "Chemistry changes may be either subtle or significant; whatever the circumstances, the experienced water treatment professional can guide mill personnel through a seamless, transparent transition in almost every situation," he said.
According to Degussa's Roland Pelzer, suppliers know that their business depends on their ability to ensure smooth transitions. "Twenty-four-hour support by supplier application experts is offered for the first days in a lot of cases," he said. "On the other hand, program changes may be applied preferably after planned shut downs. Important quality and environmental parameters have to fixed, agreed upon and monitored before, during and after the transition." Pelzer said the first weeks offer the best potential for further improvement.
"Before initiating the transition process, the 'new program' conditions that must be met and all safety training and operational procedures should be agreed upon," Johnston added. "This ensures that all personnel are well informed and can respond to change in the appropriate manner. The use of a Gannt chart or other project management tool is very helpful to manage all of the details, to give visibility to the change status, and to manage communications."
Especially if it can mean the elimination of chemicals, water treatment program changes needn't be restrictively complicated, said Dewhurst of ALGAS. "It can of course mean that there will be the need to change piping, for example, in the case where better treatment produces water that can replace fresh water on showers or pump sealing water; however, this would be a very positive change that produces savings. In some cases it would be less expensive to replace the chemical-dependent equipment with mechanical, and have a one-step rather than two-step system."
If a mill and the supplier determine that change is necessary, they should make sure that every affected process stream is covered by the transition plan. Kasy King recommended that if primary, secondary, and tertiary treatment systems are involved, transitions should be spread over the three treatment areas separately, instead of all at once.
"Proper planning and transition coverage will help minimize the risk of effluent stream upsets and permit violations," he said. "Suppliers should work closely with the pulp and paper mills to inform them of the plans, so that spills and upsets are at a minimum. As mentioned above, process testing and monitoring is critical to the success of the transition to the new technology."
"There are some applications where chemical treatments are readily interchangeable," said Nalco's George Totura. "For example, one sulfite-based oxygen scavenger is pretty much the same as the next. Much more care is required in treatments that have a broader impact around the mill."
An example of this involved a mill hoping to save money by changing its influent clarification program from an organic polymer to an alum-based program. "Alum is a proven technology that has been used for years, but in this situation there were very costly ramifications to this change," Totura said. "As a starter, the sulfate anion that is the counterbalancing anion to the positively charged [Al.sup.+3] species in the molecule caused an immediate decrease in anion demineralizer unit performance. With caustic costs being what they are, this more than overcame the 'apparent' savings in using alum."
Totura said that, in addition, the engineering team that surveyed this mill found several other unit operations in the mill where alum-based floc or aluminum-based deposits were impeding heat and mass transfer. "And all of the data were available on the mill's control systems!" he said. "If the mill had continued on this path, they would have spent several million dollars for an apparent savings of less than US$ 100,000."
Tweaking--or overhauling--its chemical treatment program is not the only way a mill can lower total treatment costs. Certain combinations of mechanical and chemical treatment can help. "In most cases, the process engineering of water treatment chemicals is underestimated," said Pelzer. "Optimization of polymer feeding technology may result in savings of more then 30%. Of course mechanical devices like wires and suction units in a paper machine, flotation units, or sludge dewatering machines have a fairly high impact on the result of the liquid/solid separation process; hence, they influence the chemical treatment costs of those applications." Because mechanical treatment improvements require capital investment, their cost must be balanced against the costs of the chemical additive treatment.
"There are certain applications where a mechanical solution is superior to a chemical solution. By the same measure, there are times when an operational solution is the best approach," said Buckman's Jim Graham. "The difference between a program that relies exclusively on chemistry compared to one that uses the best combination of chemistry, mechanics, and operations can be dramatic. For example, sludge dewatering is as much dependent on the ability of the press to successfully separate water from solids, and on the ability of the operator to be properly trained to take advantage of the system mechanics, as it is on the dewatering chemistry itself. It is not unusual to achieve reductions of 20-30% in the chemical usage for this type of application if the best combination of the three components are optimized."
According to Philippe of Ciba Specialty Chemicals, mills must first identify the strengths, weaknesses, and potential synergies of mechanical versus chemical treatment programs. "The balance between mechanical and chemical interaction potential must be understood and optimized for the specific application being considered. Essential to lowering treatment costs is the right choice of mechanical units, the proper sequencing of these units in the operation, and the selection of the lowest risk--highest benefit chemical treatment program.
"A good example of effectively combining mechanical and chemical treatment is a novel, cost effective, membrane filtration technology that--when used in conjunction with chemical coagulants--allows water treatment plants to meet the recently reduced EPA arsenic standard," he added.
Len Dewhurst of ALGAS shared a few other examples:
* Polishing after an existing dissolved air flotation (DAF) unit (using a microfilter, for example), producing a super clear water quality;
* Polishing the cloudy or clear water from a disc filter where chemicals are being added to try to improve water quality
* Pre-treatment in primary effluent where there is the possibility to use equipment without chemicals, thereby producing a water discharge lower in solids subsequently requiring less chemical addition, if needed at all.
"In many cases, chemical dependent programs can appear to be less expensive than mechanical programs--but the installation and necessary control systems, the resultant performance, and the cost of chemicals do in fact make them more expensive in a very short operating time," he said.
Mills should be wary of any chemical supplier that meets every problem by suggesting the addition of a new or different chemical. The potential synergies between mechanical, operational and chemical variables are too important to ignore.
"I had some experience with this while troubleshooting a problem with the copper concentration in the condensate coming from a pulp dryer system," said Totura of Nalco. "If I had simply recommended more chemicals, we would have missed so many other important considerations in how the system was performing. Understanding the flow rates and temperatures that the unit was designed to work under established the mechanical considerations. The mill had increased production, but flow rates were still in an acceptable range where erosion/corrosion would not be expected. Part of the operational component was how the desuperheater system was regulating steam temperature, and the role this had in copper wastage. There was also a chemical component to the solution, but this was certainly not the only improvement that brought about the desired result. Understanding the interaction of the mechanical, operational and chemical variables is what real problem solving is about."
ABOUT THE AUTHOR
Jan Bottiglieri is senior editor of Solutions! magazine and editor of TAPPI JOURNAL. Contact her by email at firstname.lastname@example.org or by phone at +1 847 466 3891.
JAN BOTTIGLIERI, SENIOR EDITOR
IN THIS ARTICLE YOU WILL LEARN:
* Strategies for managing higher chemical costs.
* Tips for smoother transitions when changing water treatment programs.
* How mechanical, operational, and chemical systems can work together to control costs.
* "New technology in water treatment," by Alan Rooks, Solutions! February 2004. To access this article, type in the following product code in the search field on www.tappi.org: 04FEBSO31. Or call TAPPI Member Connection at 1 800 332-8686 (US); 1 800 446-9431 (Canada); +1 770 446 1400 (International).
* "How mill closure affects additives and paper quality," by Alan Rooks, Solutions! February 2005. Product Code: 05FEBSO21.
* "2005 Engineering, Pulping and Environmental Conference Proceedings CD-ROM," available through TAPPI Press. Product Code EPECD-05.
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|Publication:||Solutions - for People, Processes and Paper|
|Date:||Feb 1, 2006|
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