Wet end chemistry: doing more with less.
To help our readers get more for less, we asked the wet end experts to weigh in on how effective chemical use can help them reduce costs, improve efficiency, and meet environmental targets. Sweet!
CREATIVE COST CAPPING
When mills feel pressure to keep costs low, they pass that pressure to suppliers--who are generally quite willing to help discover ways to cap chemicals and process costs through more effective use of their products. For instance, as "cost per ton" contracts have become more popular, chemical suppliers are taking a hard look at the economics of product delivery, said George S. Thomas, product specialist, papermaking technologies for Buckman Laboratories, Memphis, Tennessee. "Suppliers now focus on supply chain management: choosing the most economical containers (returnable bins, disposable bins or bulk), delivery patterns, and shipment quantities. Suppliers are also paying more attention to product composition and the mill problems they are trying to treat.
"The days of using only a few products to treat everything are behind us," he pointed out. "For example, pitch and stickies used to be lumped together and treated with identical products. Suppliers now know that they are chemically different and can best be controlled with specific products whose composition is carefully designed to take into account the specific chemistry. This results in more efficient use of the products and better performance of the treatment program."
Paying attention to the details of proper chemical use can pay big dividends. "As I discussed in a recent Solutions! article, proper storage, make-down, and feed procedures ensures the longest chemical life and efficiency, thus reducing the cost of chemicals," said Kasy King, Papermaking Process Consulting, LLC. "The use of the optimum addition points and sequence insures the largest impact of all the chemicals for the lowest usage rate/cost. Finding a way to measure the chemical's efficiency insures the ability to titrate the chemical's use to either its minimum or maximum use rate for the desired end use." According to King, possible process savings mills can expect by following this advice include fewer sheet breaks, fewer deposits, reduced wash-ups, minimized process variation, and higher quality product.
"To reduce costs, an important step is to identify the synergies, both positive and negative, between the functional paper chemicals that typically provide a physically measured paper property such as brightness, and the process wet end chemicals such as cationic polymers often applied to control wet end charge for ensuring machine runnability," said Steve Tremont, director of business operations, Ciba Specialty Chemicals, Suffolk, Virginia, USA. "For example, a regional market demand change may initially increase wet end chemical costs from higher fluorescent whitening agents (FWAs). Optimization and cost reduction can then be achieved by measuring the wet end charge impact of the higher dosages of anionic FWAs and understanding that neutralizing the extra charge with cationic polyamine or polydadmac polymers can lead to a negative synergy by quenching the whiteners. In this case, communication between knowledgeable chemical vendors and the machine operating personnel is critical to avoid supplier finger pointing."
Shekar Shetty, vice president research and development, Nalco Company, Naperville, Illinois, USA, noted that process dynamics are affected by pulp, water quality and other variables. "By using a mechanical, operational and chemical approach, mills and their suppliers can work together to reduce the amount of chemicals being used. This requires understanding the process better using tests, sensors and know-how. The best solution may include equipment, better feed points and/or better products. This often results in the reduction of chemical costs, reduced process variability and improved on machine efficiency."
Proper application of an effective process chemical can cut overall chemical costs by eliminating additional "band-aid" chemicals and by increasing production, added Darren Swales, applications group manager, Kemira Chemicals Inc., Kennesaw, Georgia. "Functional chemicals, on the other hand, impart a needed quality to the finished product such as wet strength, water resistance, etc. The key to reducing costs with these products is utilizing them properly and using the most effective product in the class.
"It is crucial for both the mill and supplier to be aware that performance and final, overall cost should be the focus, not individual chemical costs. For example, often the application of two or more various chemistries that work synergistically together will have a lower overall cost, and provide the mill with improved efficiencies," said Swales.
"Of greater importance than cost is focusing on adding value," added Paul Fish, market support manager, Eka Chemicals, Marietta, Georgia, USA. "Value comes from in-depth understanding of each paper machine, and pinpointing the desired properties of the sheet to meet the customer's demands.
High performance chemistry--such as silica nanoparticle systems for improved retention and drainage, combined with anionic trash collectors--can minimize or eliminate the need for a wide range of utility chemicals. In addition, high performance chemistry can provide a means for reducing fiber content, or allowing for the switch to lower priced fiber, accomplished by raising filler content," Fish said. "Also, advanced wet end nanoparticle systems can lower energy costs, because of faster, more controlled dewatering. Thoughtful application of high performance chemistry contributes to evolving existing grades to higher levels, and to creating entirely new grades."
IMPROVING PROCESS EFFICIENCY
While an effective wet end chemical program has a profound effect on process efficiency, papermakers still seek ways to get the same process benefits using less chemical product. Again, the concept of "value" is where papermakers should focus, according to the experts. Assuming that operations is using the chemicals under optimum conditions (chemical storage, handling, and feed costs are at the lowest possible levels), "it then becomes preferred to look at an additive's value to the entire system instead of just focusing on its costs," said King. "Value is composed of the chemical's cost, its impact to process efficiency, and its contribution to paper quality."
The maximum value, he explains, might even include a higher chemical cost, if this helps the mill achieve the best results in quality or efficiency. "Looking at the value equation is much easier if the operating unit can measure and react to the chemical and its contribution to the process." King added.
Shekar Shetty of Nalco agrees. "To help papermakers improve process efficiency while using less chemicals, we first conduct a paper machine audit to ensure that the proper equipment is in place, the feed points are optimized and the most effective chemicals are being used at a minimal level to accomplish the goals of the mill," said Shetty. Suppliers can also uses automation and continuous monitoring to better predict the need for chemicals. "This ensures that there is always enough, but never more chemical than necessary to maintain process efficiency.
The Scale Rate Monitor, a proprietary scale monitoring device, is a good example. It measures the calcium carbonate or calcium oxalate scaling potential of bleach plant process waters in as little as 15-30 minutes. Shorter term monitoring tools give mills the opportunity to 'dial in' the results they require, with only the amount of chemistry being applied that is needed, which is hard to do in any other way with these highly variable processes. As a result, the mill is able to keep scale deposition to a minimum and improve process efficiency while using less chemicals," he said.
Choosing the best chemistry really means choosing the right combination of chemical approaches. For instance, "combining microparticle and micropolymer technology to 'decouple' retention and drainage can lower the overall wet end cost/ton by 'locking' fiber, fillers and functional paper chemicals into the sheet whereby the whitewater systems are cleaner, the tendency for deposits is minimized, and sheet quality improves," said Ciba's Steve Tremont. "Once the right chemistry is chosen, on-line wet end control technologies are now available for optimizing chemical usages, sometimes up to a 20% decrease, by reducing the tendency for machine operators to overfeed certain additives when getting through a shift. An overall benefit analysis of any wet end control strategy is critical to determine if the chemical savings and improved process efficiency is worth the cost of the initial installation and continued service of the on-line process control system."
To best manage process and machine efficiency, papermakers must balance both mechanical and chemical attributes, noted Brine Ranson, global segment manager-printing & writing, Hercules Pulp and Paper Division, Wilmington, Delaware, USA. "This is especially important as equipment exceeds its original design capacity. New process chemistries are available for controlling deposits, improving defoaming capabilities, and allowing the entire operation to run at the lowest possible overall cost. For example, microbiological control technology allows papermakers to operate a cleaner machine, which can increase the time between clean-ups and boilouts; reduce off-quality paper, to improve process efficiency; and reduces the number of biocides and cleaning chemicals that mills must handle. Products are also available that allow the machine operator to improve operating efficiency at the lowest possible chemical use.
"In addition, a number of new functional chemistries are now available that allow the papermaker to achieve maximum contribution towards retention, drainage, strength, and brightness without jeopardizing optimal mechanical operation," Ranson said.
The "do more with less" mentality finds its true home in the environmental arena, where chemical use in the mill is often the pressure point for customers, environmentalists, and government regulators. "The environmental impact of chemicals depends upon several factors: the actual makeup of the chemical, the degree of substantivity to the fiber, and the final history of the process water," said Ron Richmond, marketing group leader for Kemira Chemicals. "To as high a degree as possible, chemical manufacturers are making pulp and paper chemicals as environmentally friendly as they can. The goal is to use the minimum quantity of chemical needed to get the job done. Proper application points and effective dosing equipment are crucial to this effort."
All specialty and commodity chemicals affect the environment, said King, in farreaching and varied ways. "Chemicals impact the total organics in the effluent stream, volatile organics in the air, solids content to the discharge stream, turbidity/color to the discharge, BOD/COD levels, human contact issues, water consumption, energy use, and more. As discussed, the chemicals need to be added efficiently and effectively to promote the minimum level of chemical discharge to the environment, in addition, chemicals must always be handled in ways that do not endanger the operator's health and safety.
"Retention and drainage aids also have a role to play in the consumption of water and in the energy used to produce a ton of good paper," King advised. "By applying the retention/drainage technologies in the best possible ways, retention and drainage can be optimized resulting in lower solids discharges, reduced water consumption, and minimum energy use per ton of good paper produced. Using less water and energy is vital to cost savings, while carrying materials out of the process with the paper is much better tan treating them at the effluent treatment plant."
Eka's Mark Zempel, market manager-retention, agreed. "When fiber, filler and additives are retained in the sheet with nanoparticle technology, they reduce the environmental costs associated with wastewater treatment and landfill of ash-laden waste. In addition, when stickies are cleverly trapped in the sheet, they become part of the end product, not an environmental disposal problem. Plus, as the cost of energy keeps going up, gaining a drying bonus from advanced retention chemistry adds up. Reduced energy consumption is an environmental gain."
For mills facing environmental pressures, retention and drainage programs are just part of the arsenal. As papermakers demand products that are safer and environmentally friendly, chemical suppliers have developed a variety of answers, said Buckman's George Thomas, "Suppliers have addressed environmental concerns in several ways, including the following:
* Many suppliers have converted the surfactants used in their products to non-alkyl phenol ethoxylate alternatives. Some suppliers have APE-free alternatives for their entire product line.
* Suppliers have taken significant steps to eliminate materials listed on the SARA 313 list from their products.
* Some suppliers have introduced more products into their product lines deemed 'safe to handle' and not regulated by the DOT. 'Safe acid' products are good examples.
* Some suppliers have marketed neutral boilouts such as enzyme based starch system boilouts which are safe to use and do not pH shock the mill's waste treatment system.
"Suppliers will continue to improve the safety and environmental profile of their products and services," Thomas said. He predicts that suppliers will:
* Continue to replace petroleum-derived chemicals with agriculturally-sourced products, including enzymes.
* Reduce/eliminate Volatile Organic Carbons (VOCs) from their products.
* Continue the trend of low toxicity and non-toxic microbiological control.
* Continue to develop neutral boilouts and cleaners.
Fiber management programs are another example of how suppliers can help mills reduce chemical use, noted Nalco's Shekar Shetty. "They improve fiber yield in the pulping process resulting in a higher percentage of usable fiber from wood chips. They allow production of better-quality pulp through less-harsh cooking of wood chips, which decreases the use of bleaching chemicals to reach target brightness, improves pulp yield and reduces waste. Management of fiber resources is critical to the quality and efficiency of papermaking, especially as environmental issues become more prevalent and manufacturers look for alternative sources of fiber."
Brine Ranson of Hercules offered more examples of ongoing supplier efforts in the environmental arena. "Product reformulation is constantly underway in our laboratories to upgrade products that may contain VOCs or APEs. Waste water treatment solutions insure that water returning to waterways is in compliance and sludge conditioning treatments insure that sludge can be safely landfilled or burned," he said. "Other technologies include cleaner wet strength resins and biodegradable debonders/softeners which provide a cleaner, safer environment. Reworking wet strength broke can be done with a more environmentally friendly (chlorine-free) technology. A non-mineral oil based pulp mill defoamer is delivering favorable results and is not only less hazardous to the environment but is a great way to curb the impact of rising oil prices without sacrificing performance. Chemical suppliers are working to help papermakers improve environmental impact at nearly every touchpoint in the mill," Ranson said.
IN THIS ARTICLE, YOU WILL LEARN:
* How effective chemical use can help reduce costs.
* How effective chemical use can aid process efficiency.
* How chemical suppliers are helping mills handle environmental pressures.
* "How cost pressures are changing wet end chemistry," by Jan Bottiglieri, Solutions! June 2005. To access this article, enter the following Product Code in the search field on www.tappi.org: 05JUNSO34. Or call TAPPI Member Connection at 1 800 332-8686 (US); 1 800 446-9431 (Canada); +1 770 446 1400 (International).
* Principles of Wet End Chemistry, by W. Scott, available through TAPPI Press. Product Code: 0101R241.
* "Optimization through storage, handling and feed," by Kasy King. Solutions! May 2005. Product Code: 05MAYSO31.
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|Publication:||Solutions - for People, Processes and Paper|
|Date:||Nov 1, 2005|
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