New Technology Creates Minerals, Pigments From Deinking Residuals
Ginn, Michael W
Used at Augusta Newsprint, the Pyroflex system employs controlled thermal and chemical reactions to recover materials from deinking residuals and reduce landfilling
The recycling of wastepaper is one of the largest, most successful, and cost effective programs within the paper industry. Paper recycling continues to increase on a global basis and is a critical element within the sustainability initiatives adopted by the paper industry.
In the U.S., the recycling rate of all paper has increased to more than 50% and a new target of 55% has been adopted by the AF&PA. Each time a truckload of recycled paper is unloaded, there is an estimated one to two tons of high quality pigments delivered as well. In many cases the paper recycled is identical to the paper being manufactured.
During recycling, environmentally sensitive by-products are created. These are known as deinking residuals (DIR) and generically consist of 40%-60% water and soluble salts, 20%30% organics (wood, fibers, inks, oils, stickies, etc.), and minerals (kaolin, carbonates, titanium dioxide, talc, etc.)
There have been many studies and even committees formed to evaluate options for eliminating the negative environmental impact of these residuals. Many paper and mineral companies have pursued research programs that target the potential value of the minerals within the DIR. However, until recendy there had been no significant achievement in capturing the total value of these by-products.
Developed in June 2003, PYROFLEX technology is proving to be a sensible and cost effective DIR management system and pigment supply model.
Prior to 1970, there was very little paper recycling occurring in the U.S. and the linear “flow through” model (going from forest to landfill) was in full effect. During the 1970s, paper recycling emerged as a source of good fiber; deinking technology began to develop on a large scale.
From 1980-2002 significant developments began to shape the modern paper recycling system. These developments included curbside paper recovery systems, flotation deinking, and paper makers using 100% recycled fiber as a furnish. By 2002, paper recycling increased to more than 48%. Figure 1 illustrates a generic example of the paper recycling model prior to the Pyroflex technology.
In 2003, two milestones in recycling history were reached with more than 50% of US paper being recycled and the first Pyroflex plant being successfully commercialized. The AF&PA’s target of 55% by 2012 will increase the need for more comprehensive DIR management systems such as the Pyroflex pigment recovery system.
Within the new eco-economy, the global need for this technology is paramount. Over the next several decades the paper industry will continue to shift from the linear model to the reuse/recycle model. In this closed loop system, which emulates nature, recycling industries will largely replace extraction industries.1
Pyroflex Dynamics and the Value to Papermakers
The Pyroflex system is a series of controlled thermal and chemical reactions that selectively recover minerals and nanomaterials from a specific DIR. Nanomaterials are also controlled with respect to composition and size to optimize the heat transfer in the thermal reactors and mass transfer in the composite system. The minerals and nanomaterials recovered are custom designed for brightness, light scattering, and particle size. The engineered pigments are carbon-dioxide free and are considered carbonneutral for the eco-minded publishers.
Figure 2 illustrates the advance paper recycling model with the integration of the Pyroflex technology.
The 20% deinking residual stream is an excellent source for energy and minerals. The technology offers a combination of services and products while minimizing the negative effects of paper recycling. Figure 3 demonstrates the material balance reduction of the deinking residuals into the pigment.
The reduction process is a function of the moisture and ash content of the DIR. The material reduction generically ranges from a ratio of 2:1 up to a ratio of 7:1. The physical transformation of the DIR into custom designed and engineered pigments is shown in Figure 4. The product is white, has significant light scattering characteristics and is particle sized for functionality.
Cost reductions are the result of the mill integration process creating benefits from several groups of synergies including environmental, operational, energy, and brightness and opacity development using pigments.
Once the Pyroflex system’s integration is complete, mills could reduce cost by a minimum of $2 per .finished product ton up to $12 per finished product ton.
The environmental service of the technology virtually eliminates any cost associated with landfilling DIR such as transportation and tipping fees, which continue to increase on a yearly basis. These cost reductions also include costs associated with burning including carbon dioxide emissions, inefficient burning and boiler wear, and landfllling of the ash.
Operational costs associated with the recycling of carry-over is reduced and in some cases eliminated. The carryover inherently supplies residual inks, discolored minerals, stickles, soluble salts, abrasive materials, and other detrital materials back into the recycled fiber system. Pyroflex provides for the optimization of the deinking process by allowing papermakers to optimize the fiber recovery process with emphasis on fiber brightness and purity. The papermaker can purge the deinking system by sending more carryover into the DIR stream from which the minerals are recovered, processed, and purified into valueadded pigments. The short fibers in the carryover are used as energy sources providing energy to the mill. The Pyroflex system provides the most economic and efficient option for recombining the fiber and mineral system for sheet opacity, brightness, strength, and COF. The value of this concept is increased as basis weight is reduced.
Energy synergies are optimized by the proprietary thermal processing technology of Pyroflex. Thermal processing parameters are maintained in the thermal reactors to provide conditioned ash to Pyroflex and discounted energy in the form of high/low pressure steam, hot gas, etc. to the host mill.
The pigments delivered to the mill do not have “non-value added” elements in the pricing structure such as delivery and mill receiving. In many cases, these costs add $25-$100 per ton to the delivered price structure. The inherent light scattering and brightness qualities are designed and customized for the specific end user. The pigments manufactured are very consistent in quality and are carbon dioxide free pigments.
Designed for Sustainability
The Pyroflex plants are located on-site, adjacent to, or in regional proximity to the recycling fiber or paper mill. A longterm contract is negotiated with terms relating to the environmental service, energy supply, and pigment supply to the mill(s). The processing flexibility simply allows for the waste to be pipelined in slurry form, pneumatically conveyed, or trucked to the Pyroflex plant. Once the mineral recovery and pigment design process is complete, the pigment is returned to the mill as a slurry or dry powder.
The business model maximizes a group of synergies that preserves the environment, reduces papermaking cost and enhances sustainability. There are two options for integrating the process: the independent option with no heat recovery; and, the integrated model where heat recovery is a component of the integration process (Figure 5).
Applications and Pigment Performance
One of the most significant breakthroughs attributed to the technology is the commercial application and design of the recovered pigments, minerals, and nanocomposites. The trademarked PYROTEX pigments are designed to maximize light scatter. This is achieved by chemically and thermally structuring the minerals and nanoparticles into efficient light scattering pigments. In most North American applications, the recovered mineral contains from 2% to 8% TiO^sub 2^ which creates additional opacity by virtue of its refractive index. Many of the Pyroflex products are carbon dioxide-free and provide a carbon-neutral option for papermakers targeting eco-minded publishers. Laboratory research, pilot trials, and mill trials have shown that Pyroflex products can provide value in a range of papermaking and coating applications including: newsprint; SC grades; directory grades; uncoated freesheet; board coating; LWC/ULWC coating; and, blend components with kaolin, GCC, PCC, etc.
Newsprint: The first commercial application of the technology was in the newsprint sector. One of the most desirable attributes of a pigment designed for newsprint is opacity. Many studies and evaluations comparing PCC, calcined kaolin, and GCC have repeatedly confirmed the improved overall optical and sheet properties when using Pyrotex pigments in newsprint applications (see sidebar below).
The introduction of four-color printing of newsprint, lower basis weights, and increased use of recycled fiber have placed demands on the filler’s performance. The most important filler properties are high light scattering and porosity. Light scatter is required for opacity and porosity is needed to prevent ink strike through.
Handsheet studies, as well as pilot and machine trials have shown that Pyrotex products provide excellent opacity, bulk and printing properties compared with other hydrous pigments and equivalent performance to commercially available calcined clays and PCC. Pyrotex is effective at low filler levels and can be run under acid or alkaline conditions. Figures 6 and 7 show data from handsheets.
Pyrotex is a structured pigment that increases light scatter and improves opacity in newsprint. The high porosity prevents ink strike through. It offers sheet brightness advantages over PCC because of alkaline darkening associated with PCC.
The use of PCC prevents the papermaker from running under acid conditions and forcing the change to neutral or alkaline conditions. At neutral conditions alkaline darkening occurs, pulp brightness decreases and bacterial activity increases. Additional filler has to be added to overcome this brightness drop. Pitch formation can increase at neutral conditions because there is an increase in the extraction of fatty substances as pH rises.
Pyrotex is efficient at low filler levels and provides improvements in brightness, opacity and printability in newsprint. Pyrotex has proven to give excellent machine runnability and performance on commercial paper machines.
SC paper: Typical fillers for SC papers are coarse platey particles that allow high filler levels to be achieved without detracting from strength properties. These fillers also offer sheet smoothness and high sheet gloss but are not designed for optimal light scattering.
Light scattering can be achieved by using a structured pigment, such as Pyrotex that can improve both brightness and opacity simultaneously. Structured pigments are effective for scattering light but will cause fiber debonding and loss of paper strength. The use of structured pigments also affects surface properties such as sheet gloss, smoothness and porosity.
Using blends of platey fillers with structured fillers provides a compromise. The platey filler will generate high sheet gloss and smoothness while the structured pigment will provide bulk and light scatter.
Pilot machine, paper machine and printing trials were run in Europe using a standard recipe for SC grades that are produced commercially. The control pigment system was 75% kaolin and 25% PCC. Pyrotex replaced the PCC with levels increasing from 25% to 50%, 75% and 100 % of the total filler. Figures 8-10 provide data from the pilot machine trials.
Overall, Pyrotex improves sheet brightness and opacity when replacing hydrous kaolin. Sheet gloss was lower with the structured pigment and porosity was higher. It could replace PCC and maintain sheet properties.
Based on these results a paper machine trial was run comparing a blend of 67% kaolin and 33% PCC with 67% kaolin and 33% Pyrotex.
The Pyrotex/kaolin blend was run on a commercial-scale paper machine with no problems in wet end stability or runnability (Table 1).
The trial yielded acceptable results for the customer. A blend of kaolin and PYROTEX allows the SC producer to optimize optical properties and maintain gloss and smoothness.
Due to the flexibility of pigment design and structure, modifications can be made to Pyrotex to increase gloss by producing a finer particle size. This will allow the papermaker to use more Pyrotex and less platey kaolin. It can be engineered to meet the customer’s demands for brightness and opacity as well as for smoothness and gloss. Pyrotex is offered in a range of chemistries that are dependent on the DIR composition as well as the end use of the recovered minerals.
Preserve the Environment, Reduce Costs
The industry is facing competitive and environmental pressures. Increases in costs, reductions in demand, and the global paper structure and pricing of paper all formulate the challenges ahead. Incorporating Pyroflex technology within a corporate eco-strategy could improve the bottom line. In the national innovation initiative’s interim report titled “Innovate America”, Wayne Clough connects novelty with utility in the following quote “Innovation requires not only that we first discover new knowledge and invent new technology, but also that we are first to develop new ideas and ways to put the knowledge and technology to work to solve problems and create opportunities.”2
Pyroflex technology provides an opportunity for the papermaker to take advantage of the principals as described by Clough while preserving the environment and reducing cost.
1. LR. Brown, “Eco-Economy”, First Edition. W.W. Norton & Company, Copyright 2001 by Earth Policy Institute.
2. “Innovate America, Thriving in a World of Challenge and Change”, National Innovation Initiative Interim Report by Council on Competitiveness, July 7, 2004
MICHAEL W. GIMM is research director, PYROFLEX, Atlanta, Ga.
Copyright Paperloop, Inc. May 2005
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