Approved and Available Graduate Research Projects
The need to convert biomass into fuels and chemicals was one of mankind's earliest drivers for chemical and biochemical research. To utilize wood fibers or other cellulosic materials, separation of hemicellulose and cellulose from lignin is very important. If the lignin, hemicellulose and cellulose can be effectively separated, the traditional industry can be dramatically changed, and many new products and new applications can be developed. Some direct impacts of separation of hemicellulose and cellulose from lignin on our current and future industries include:
- Improve pulping efficiency, reducing pulping energy, increase pulping yield
- Reduce bleaching coast and improve fiber quality
- Use hemicellulose as new biodegradable chemicals
- Improve fermentation efficiency and ethanol production in biofuel production
The kraft pulping process is the preeminent pulping technology in the U.S. , and the capital investment associated with this process requires that any changes in pulping and papermaking retain this key process. Despite the well-acknowledged advantages of kraft pulping (i.e., high-strength pulps, insensitivity to wood species; ease of recovering spent pulping chemicals/energy) it operates with several process limitations including relatively low pulping yields (approx. 40-45%). Although the loss of lignin is a favorable outcome during pulping, the loss of hemicelluloses is unfavorable.
Our recent research indicated that the combination of enzyme and NaOH-urea treatment can effectively dissolve hemicellulose and cellulose. Our results also indicated that, if the conditions are well controlled, the hemicellulose can be removed from wood chips but without affect cellulose and wood fibers properties. We also found that the wood fibers can fully dissolved by the treatment in >7% urea solution.
Partially removal hemicellulose from wood chips can loose the fibers in wood chips, which improves the pulping efficiency and energy consumption. Fully dissolve hemicellulose and cellulose can provide a novel method for feedstock treatment in biofuel generation. Beside the effectively producing wood fibers, our recent discover in dissolve wood fibers provides a possible new method for regeneration of cellulosic fibers. Comparing to the method used in rayon fiber production in which CS2 is used as cellulose dissolution agent, our new method does not generate toxic H2S. Furthermore, the dissolution of cellulose can be carried out at room temperature and the dissolution degree is controllable using our new method.
Our primary study indicated that the novel cellulosic dissolution method has many advantages than other methods, which provides great potentials for utilization of cellulose materials. The student who works on this program will focus on the fundamentals of the complex formation between urea-NaOH and cellulose. The effects of the cellulose structure, including crystallization degree and molecular weight will be studied in details.
Advisor: Jeff Empie
Effective and economical purge of chloride from the kraft liquor cycle has been for many pulp mills a longstanding problem with no practical solution. Adverse process impacts of chloride buildup include enhanced corrosion in recovery boilers, fouling of multiple effect evaporators and boiler tube surfaces in the recovery boiler, and depressed melting points of the inorganic salt mixture needed to protect the lower furnace walls of the recovery boiler. As mills close up their liquor cycles, the accumulation of chloride becomes even a bigger problem. Due to the high solubility of chloride in the aqueous liquor streams, its separation and removal have not found a practical, economical answer.
This work proposes a new alternative to purging chloride while not placing demands on other process equipment in the cycle. It will use the principle of electrochemical salt splitting with the addition of ammonia to produce ammonium salts useful as fertilizer, along with a sodium and potassium hydroxide solution which can be added to the white liquor or sent to the bleach plant if there is one. The separation is accomplished through the use of electrodialysis (ED) with ion selective membranes that efficiently generates these two separate product solutions.
A detailed material balance around the kraft liquor cycle has been made to identify the benefits and costs of the proposed technology. For a 1000 ton/day pulp mill, this technology shows a net benefit of $1.5 M/year, relative to the common practice of dumping electrostatic precipitator (ESP) saltcake. This is largely due to the commercial value of the ammonium salt stream, the reduced need for sodium makeup, the reduced causticizing/calcining load, and the elimination of a disposal fee. Also factored into this are the added purchase costs for ammonia, power, and sulfur makeup. Process operating benefits in extended times between recovery boiler water washes, reduced corrosion and scaling, and reduced calcining energy costs are expected, but not quantified.
The objective of this laboratory study is to establish the technical feasibility of using a salt splitting approach to the ESP catch featuring electrodialysis with ion selective membranes and ammonia injection. This work will feature the two-compartment ED unit previously used by IPST for solving the same chloride purge problem addressed here, but reconfigured to a three-compartment mode. [The former study was based on separating chloride from sulfate and carbonate.] The equipment is presently located in a laboratory of the School of Earth & Atmospheric Sciences. The faculty member in charge of the unit has indicated a willingness to make it available as his study is nearing completion.
Embedded Sensing in Packaging Using
Molecularly Imprinted Polymers
John Cairney (IPST & School of Biology, GT),
Boris Mizaikoff (School of Chemistry and Biochemistry, GT),
Roman Popil (IPST)
THIS PROJECT WILL CREATE FUNCTIONALIZED PAPER WITH MOLECULAR RECOGNITION CAPABILITIES NOT ATTAINABLE WITH ANY OF THE PHYSICO-CHEMICAL APPROACHES CURRENTLY BEING RESEARCHED IN THE USA, EUROPE OR ASIA.
We propose a body of work that will demonstrate that a Molecularly Imprinted Polymer (MIP) applied to the surface of paper products can confer sensory capabilities that permit environmental monitoring of specific chemical, biochemical or biological entities. We will construct a molecularly imprinted coating that will then be applied to the surface of corrugated cardboard and paper, and we will show that the coated paper product can reliably detect target molecules introduced into the environment. These experiments will simulate the detection of a spoilage product, toxin or pathogen by functionalized paper packaging. Such packaging would be of great benefit to the Food and Medical Packaging and Environmental Monitoring Industries and lead to the creation of new markets. Membranes can be constructed to detect changes in temperature, pH and humidity, however the advantage of the proposed MIP receptor technology over currently tested sensors embedded or applied to paper surfaces is that they can be designed to display exquisite molecular specificity. Further MIPs with different target selectivities can be combined into a single coating layer to produce a surface that simultaneously monitors and detects pH, humidity, enzymes and small molecules or pathogens of choice. The renowned robustness of biomimetic MIP receptors in contrast to their natural analogues such as antibodies results in functionalized surfaces that resist environmental extremes and maintain activity for several years.
Molecular Imprinting or Templating is a technique for creating synthetic receptor sites within a highly cross-linked polymer matrix. A Molecularly Imprinted Polymer (MIP) may possess three-dimensional cavities that resemble those of a particular catalytic enzyme and, by virtue of this, the MIP may bind substrate molecules with the avidity and fine discrimination characteristic of that enzyme resulting in biomimetic functionality.
Chemical stability studies using Molecularly Imprinted Polymers (MIPs) have demonstrated that these polymers retain >95% of their affinity for the imprinted molecule even after 24 h of exposure to autoclaving treatment, triethylamine, 10M HCl acid and 25% NH3. Heat treatment revealed that the polymers are thermally resilient and retain their chemical affinity, as the MIP did not degrade up to temperatures of 150 ◦C. (1,2)
WHY ARE MOLECULARLY IMPRINTED POLYMERS OF INTEREST FOR PAPER FUNCTIONALIZATION?
MIPs are highly sensitive and can, in principle, be created to detect any chosen molecule and are very robust. MIPs can be easily integrated into current manufacturing practices to produce paper packaging containing embedded sensors. Embedded sensors created via MIPs have the potential or creating new markets in packaging and of displacing plastic as a packaging material. The approach described here has not been employed previously and thus provides considerable potential for patentable product development
Hot Gas Cleanup & Conditioning for Liquid Fuel Production using Novel Membranes
W. J. Koros (CHBE)
This project addresses the pressing need, identified by DOE, for improved methods to economically clean up and recover hydrogen and carbon monoxide from synthesis gas reactors fed with biomass (1). Contaminants, including tars, particulates, alkali, ammonia chlorine and sulfur components must be removed from the thermo-chemical product stream created in typical syngas reactors fed with biomass. The extraordinary advantage offered by the membrane option is that all permeate streams will be naturally free of tars and particulates by virtue of passage through the molecularly selective membrane “filter”.
Membrane separation processes are well-known to offer theoretical advantages in energy efficiency relative to conventional thermally-driven counterparts, and an aggressive program is proposed here to enable benefiting from advantages that membrane processes offer. Currently, replacing energy-inefficient separation processes requires confronting both materials and processing challenges to more broadly extend benefits available from first generation large scale membranes. Despite their known theoretical advantages, even membranes for aqueous reverse osmosis applications have only recently become accepted as the preferred technology in that area (2).
As is always the case in practical situations, reducing the cost was a key factor in enabling the transformation for the aqueous separation case. Different types of materials and modules are needed to enable a similar large scale transformation in the gas separation area, and again such a transformation requires treatment of the challenge as an integrated specialty topic, which is the focus of this project.
While hydrogen separation units with excellent reliability records have proven valuable in petro-chemical applications (3-4), even these environments are less aggressive than those intended for the hot gas cleanup and conditioning cases that are the focus of the current work. Besides thermally robust polymers, we will also explore even more advanced membranes based on carbon molecular sieve materials. Such carbon molecular sieves will enable finer discrimination and higher use temperatures than polymers can provide.
PROJECT OBJECTIVE:
The objective of this project is to fully recycle the sodium sulfate salt cake from the recovery boiler’s electrostatic precipitator. The salt cake will be used to generate sodium (and some potassium) hydroxide (caustic soda) for use in the process. The on-site generation of caustic soda will (i) eliminate the need to purchase caustic soda, and (ii) close the ‘sodium cycle’ so that zero sodium waste is discharged from the plant.
In addition to closing the ‘sodium cycle’ by recycle of sodium (and potassium) as the hydroxide, caustic soda, we will also investigate the reuse of the sulfate ion. There are two potential ‘users’ of sulfates. The first use of sulfate is as sulfuric acid by off-site chemical manufacturers. The intention is to produce a sulfuric acid stream of adequate purity and concentration that it is useful to a chemical supplier. The sulfuric acid could then be recycled by off-plant organizations and not have to be sewered. Acid of reasonable purity maybe near cost-neutral, that is, taken by an outsider as a feed-stream with exchange of little or no money. In a later phase of this project, we will investigate the upgrading of sulfate to hydrosulfite or other forms of sulfur, which could be used in the pulp and paper process
PROJECT BACKGROUND:
Significant quantities of sodium sulfate are produced in the pulp and paper process which are discharged from the plant as waste (sewered). This discharge is a significant environmental concern, and results in the purchase of raw materials, such as caustic soda. For example, a recent analysis of one Georgia-Pacific plant showed 50 dry ton per day of salt cake from the recovery boiler’s electrostatic precipitator and 20 dry ton per day from the ClO2 plant. The salt cake from the electrostatic precipitator is the focus of this study, although the output of the ClO2 plant is just as relevant. The purity of the salt cake from the electrostatic precipitator is >90%. Purification of this salt cake during recycle of the sodium and sulfate products is important. The major sodium (cation) impurity is potassium, and the major sulfate (anion) impurities are carbonate and chloride.
We propose to use electrochemical methods for formation of the sodium product (caustic soda) and sulfate project (near term: sulfuric acid, long term: higher valence sulfur compounds).
APPROACH:
The approach taken in this proposal for the recycle of sodium/potassium sulfate salt cake draws from the existing chlor-alkali process. We propose to design and build a three-compartment recycle facility for producing ‘acceptable purity’ caustic soda and sulfuric acid.
We have recently described the supercritical water synthesis and deposition of iron oxide (a Fe2O3) nanoparticles in activated carbon and shown that we can obtain egg-shell as well as uniform distributions of the metal oxide in the pores of activated carbon by manipulating process variables such as temperature, pressure, precursor concentration, and immersion time. We are currently working to make advanced catalysts of iron oxide and activated carbon from peanut hulls. Preliminary work has demonstrated that the nanocomposite catalysts that we have made show approximately 20 % improvement in their ability to oxidize propanal, a VOC of interest in the rendering industry. However, we have not explored the use of different types of activated carbons (different pore sizes, surface areas, functionalized surfaces), nor have we explored any other transition metal oxide or the variation of particle size. The use of hydrogen to reduce the deposited metal oxide to the bare metal has also not been explored.
The work proposed here therefore attempts to examine some of these options. The work extends this approach to activated carbon from wood waste and to other transition metal oxides that may be better catalysts for VOC oxidation. The objectives of this work are to prepare oxidation catalysts by depositing nanoparticles of transition metal oxides in the pores of activated carbon obtained from wood waste. Novel features of the preparation method include the use of supercritical water to transport the catalyst precursor into the pores of hydrophobic activated carbon, and hence obtain a uniform distribution of the catalyst particles in the resulting nanocomposite. In subsequent work, we plan to test the activated carbon / nanoparticle catalysts for the removal of VOCs.
The project has potential impact in several areas of the IPST Strategic Vision, most notably in the area of the Forest Biorefinery. The development of catalysts from solid residuals (carbon) of biorefining represents a potential new high-value product from an underutilized resource, and is therefore of considerable economic significance in the development of the forest biorefinery.
In the manufacture of paper products, the strength properties vary from time to time. During times of low strength production, all the steps that can be taken to improve product strength – refining, running more slowly, increased control, etc – consume more energy and slow down the production or, in the worst cases, generate waste materials.
The goal of this project is to investigate and demonstrate the conversion of cellulose-containing process fines and short fibers into nano-cellulose fibers suitable to be added back either at the wet end or as a post-treatment additive to enhanced product strength.
Technical Task 1: Fines – Use fiber classification to obtain cellulose fines, characterize and then effectively demonstrate the suitability of process cellulose fines as a source of nano-fibers. Previous studies removing 4% to 6% pulp fines gave superior drying and sheet properties.
Technical Task 2: Nanofiber generation – we will generate cellulose-derived nano-fibers, from the above fines, or from fiber furnish if necessary, and characterize their fitness-for-use in the desired products. It is known that aggressive mechanical treatment will convert cellulose into micro-fibrillated cellulose. Industrial enzymes or other materials will be used to help with nanofiber development during the mechanical step of producing micro-fibrillated cellulose.
Technical Task 3: Product generation and testing – to fully define the product need to identify an additive suitable for application on a paper machine at wet end or size press, and to demonstrate the successful use of the additive and nano-fibers for an improved paper product.
We anticipate the benefits of lower costs based on paper strength development without slowing down the paper machine due to the use of nanofiber. Without use more refining, the process enhancement can make a superior product with lower energy use. By supporting this project, we can develop more defined economic impact.
Effects of NaOH/urea Pretreatment on Biological Hydrolysis of Lignocellulosic Materials in Biofuel Production
Pretreatment is an important step in biological cellulose conversion process. Cellulosic biomass must be pretreated to realize high yield which is extremely vital to commercial success in biological conversion operations. The goal of pretreatment is to disrupt the physical and chemical barriers posed by cell walls, as well as disrupt cellulose crystallinity so that hydrolytic enzymes can access the biomass macrostructure. As alluded to above (vide infra), these accessibility issues are the key hurdles to the commercial success of pretreatment technologies for cellulosic biomass to biofuel conversions. Pretreatment has been viewed as one of the most expensive processing steps in cellulosic biomass-to-fermentable sugars conversion with costs as high as $ 0.3/gallon ethanol produced. Pretreatment has a major influence on the cost of most other operations including size reduction operation prior to pretreatment and enzymatic hydrolysis after pretreatment. Pretreatment technologies that address penetration can reduce the use of expensive enzymes.
Our recent research indicates that the inexpensive combination of NaOH/urea can rapidly dissolve hemicelluloses from lignocellulosic materials at room temperature and atmosphere conditions. We also found that by partially removing hemicelluloses and cellulose, the wood chips were defibrated easily, and porous fibers and wood fiber particles were generated, which allow for hydrolytic enzymes to easily penetrate and hydrolyze the wood fibers, thus overcoming a key hurdle to the kinetics barrier of biological hydrolysis of lignocellulosics.
In this student research program, the student will focus on the fundamental understanding of the effect of pretreated wood chips on the enzymatic hydrolysis efficiency. The interaction between NaOH/urea and woodchips will be studied.
Engineering an Enzyme System for Wood Hemicellulose Extraction
Proposal for a MS/PhD Thesis Research
By Rachel Chen, School of Chemical and Biomolecular Engineering
This research proposal addresses pulp and paper industry’s need for a better utilization of the raw material. Currently, only 50% of the wood material is made into paper products, with the rest generating very little value for the industry. One strategy to address this issue is to extract hemicellulose before pulping and convert it into value-added products.
There are many ways that hemicellulose can be extracted from wood materials. However, the enzymatic approach has unique advantages in its selectivity such that only galactoglucomannan will be extracted and leave xylan behind. This is important, as xylan is essential for proper paper strength. In addition, the enzymatic approach avoids or minimizes the use of chemicals that may have detrimental effects on the environment or subsequent processes. Further, enzymatic extraction can be implemented under mild conditions (room temperature, neutral pH, and ambient pressure), generating saving on the capital and operational cost.
Previously, we discovered a microbe isolate (185) capable of producing a plethora of hemicellulases, particularly useful for this application. To develop an efficient enzyme system, a careful study of the enzymatic composition and ratio that give the best synergy of the multi-enzyme system is needed. This project aims to improve the efficiency and yield of enzymatic extraction by focusing on developing optimal enzyme formulations and understanding the synergy.
This project provides an excellent opportunity for a student to work in a multidisciplinary environment, learn, and apply knowledge and skills from wood chemistry, biology, chemical engineering, and biochemistry.
Fundamental Chemistry of Converting Lignin to Biodiesel
Proposal for a MS/PhD Thesis Research
By Art J. Ragauskas
School of Chemistry and Biochemistry
The conversion of wood into value-added materials is a primary goal of the forest-products industry. Kraft paper is manufactured by utilizing cellulose and a select fraction of wood hemicelluloses. Lignin, a primary bioresource is extracted from wood during kraft pulping and utilized for low-value chemicals or as a heating-fuel resource. Tremendous opportunities exist to enhance the overall efficiency of utilizing wood for paper and biofuels/chemical production by developing new chemistries for lignin. This program seeks to employ recent advances in ionic liquid chemistry to develop innovative oxidative lignin depolymerization chemistry that would facilitate it’s conversion to biodiesel precursors as well as for bioplastics.
Recent studies by Ragauskas et al., have demonstrated that select ionic liquids are uniquely suited to the dissolution and chemical functionalization of lignin. This program will examine the use of metal catalyzed oxidation chemistry treatments tailored at the depolymerization of lignin by oxidation of the benzylic functionality of lignin. Initial studies will establish the fundamental chemistry utilizing lignin model compounds. Once these studies are complete, the student will employ these catalytic systems with softwood lignin to demonstrate the potential of converting wood lignin to a biodiesel precursor. The products of these oxidative systems will be characterized employing advanced NMR and GPC techniques. The proposed program will be conducted in a multidisciplinary research environment in which the student will develop expertise in sustainable biomass/biofuels chemistry.
Biorefineries refer to the production of fuels and chemicals from biomass. One biorefinery option is to gasify biomass to produce a syngas rich in CO and H2. The syngas can be used a s starting material for synthesis of various products such as liquid transportation fuels, hydrogen, and chemicals. This project involves a study of gasification kinetics and species evolution during gasification of spent pulping liquors under pressurized condition. Spent pulping liquors are a residue generated during pulping process, and they are currently burnt for the fuel value. Gasification of the liquors and subsequent production of liquid fuels offer a potential of substituting over a hundred million barrels of oil annually in the US. In the project, spent liquor will be gasified in a pressurized laminar entrained-flow reactor, and the impact of temperature and gas concentrations on gasification rate will be measured. Spent liquor gasification is an alkali catalyzed reaction, and the rates have been found to obey Langmuir-Hinshelwood type kinetics, in which the inhibiting effect of product gases (CO and H2) is important. The aim of the work is to elucidate the role of the inhibiting gases.
We propose a novel method for obtaining valuable chemicals from renewable resources -- specifically upgrading waste hemicelluloses to high value-added chemicals. Our method uses novel, tunable, benign solvents such as very hot water and CO2-expanded liquids which have distinct advantages over alternative methods. These solvents incorporate self-neutralizing acids which avoids the strong acids, subsequent neutralization and salt disposal issues inherent to the use of strong acids. The concepts involving very hot water and CO2-expanded liquids are also better adapted to scale-up to the high throughput of a pulp mill, as compared to enzymatic methods, which are often slow and require enormous holding capacity. We propose a prepulping extraction of the wood chips with an alcohol-CO2 mixture, followed by depolymerization and dehydration in very hot water. Our initial target molecules will be levulinic acid, glucaric acid and their derivatives, though once the process has been demonstrated, it will be applicable to additional target molecules.
Wood chip extraction with alcohol-CO2 mixtures provides selective separation of the glucomannan hemicellulose fraction. The expansion of the extract by dissolved CO2 offers continuously tunable solvent properties allowing for a controllable fractionation process that is economically attractive. The hemicellulose extract would then be depolymerized and dehydrated by reaction in very hot water to make useful chemicals. Both of these media offer a benign acid environment by creating self-neutralizing acids. Further oxidation is facilitated by the use of CO2 with H2O2, which gives an efficient and reversible oxidant, peroxycarbonic acid for the conversion of low value carbohydrates to high value added products. In addition, such processes lead to facile separation and purification and are readily scalable.
Increased profitability would accrue from two sources: First the sale of value-added chemicals would far outweigh the heating value of the original renewable resource – glucomannan and some accompanying lignin. Second, the extraction of hemicelluloses from wood chips prior to kraft pulping would significantly improve pulping efficiency, as the polysaccharides contribute little to the heating value of black liquor, but do detrimentally increases the viscosity of black liquor solids. Preliminary design calculations for a 1000 Ton/day pulp mill show that the capital expenditures for such a facility would be close to $13 million, operating costs would be about $5 million/year, and net profit (before taxes) from sales of value-added chemicals would be above $9 million, for a return on investment in excess of 70%!
The ultimate goal of this proposal is to begin the establishment of the preeminent center for innovative forest biomass resources research, education, and information. The student will work with leading government, academic, industry, and social policy groups both in the US and in the international arena. Given the graduate student mentors associated with this proposal and the international associations already established with this proposed center, this goal will most certainly be achieved.
An important and still growing market segment in the pulp and paper industry is on pulp molding. In pulp molding, dry paper pulp is mixed with about 10 times of water, then pressurized into a mold, and finalized dried to form cellulose products. The major drawbacks of this process are: 1) large amount of shrinkage and thus poor dimensional accuracy, and 2) poor mechanical strength because of the lack of bonding between neighboring fibers in the cellulose product. These drawbacks are apparent in many commonly used pulp molded products, e.g. egg cartons, molded pulp trays for food, molded pulp backings for packaging, etc.
The objective of the proposed research is to develop new technology for more effective manufacturing of cellulose based products in terms of enhanced strength, dimensional accuracy and productivity. This will be accomplished by mixing shredded cellulose with a small amount of ionic liquid, a green solvent, to partially dissolve the cellulose particle at the surface and produce a highly viscous paste, and then extruding or injection molding the compound to the desired shape. The resulting “green” part will subsequently be coagulated in water to extract the ionic liquid and finally dried. It has been shown recently that, with an appropriate ionic liquid, 40% or more cellulose can be dissolved. Since in the proposed approach, only the surface of the cellulose particle needs to be dissolved, the usage of the solvent is greatly minimized. Hence, the solvent in the proposed material system works more like a binder. The use of a minimal amount of solvent is considered crucial in minimizing the shape change of the cellulose product during coagulation. Given the increasing interest in environmentally preferable systems and bio-renewable feed-stocks, the impact from the proposed research is far-reaching. Particularly, the success of the research could result in the more effective use of cellulose based natural materials in general and replacing synthetic polymers in numerical applications. The ability of directly using standard polymer processing equipment, rather than specialized pulp molding facility, is also a big plus.
The proposed research deals with cellulose based materials including paper pulp and recycled paper waste, and are thus closely relevant to the pulp and paper industry. A Ph.D. student majoring in Chemical Engineering will be working on the project. The specific tasks in the first year of research will be 1) mixing of cellulose particles with ionic liquids using a batch compounding unit, determination of the practically feasible amount of solvent in the system, and process study, 2) extrusion of the mixed compound into sheets, coagulation in water, and drying; and 3) mechanical and chemical characterization of the resulting cellulose sheet.
Dryer can and press roll contamination can create significant operating problems for the papermaker. The contamination generally has “sticky” components that result in picking and sticking of the paper web because of the adhesive nature of the contaminants. In addition to the detrimental effect on paper quality, the machine productivity is affected by increased web breaks and downtime for cleaning the rolls or cylinders. In the dryer section, the first section is typically also run at lower than maximum temperatures in an effort to decrease the rate of contaminant buildup, further reducing machine productivity. As the contaminants accumulate on the dryer surface, the heat transfer from the can to the sheet is decreased as well.
The interaction between web adhesion to the contaminated cylinder surfaces and web properties, particularly cohesion, creates varying degrees of picking and sticking. The main objective of this study is to characterize the work of adhesion/separation in order to better understand the mechanisms behind web roll adhesion and picking/sticking. By recognizing what causes and fosters this phenomena, ways of preventing and reducing it, as well as optimum dryer and pressing operating strategies (if any) can be determined.
Prior work at IPST has shown that sheet moisture, sheet temperature, sheet consolidation, fiber type, surface temperature, surface moisture, dwell time, contaminant type, contaminant application method, contaminant chemical composition and the base metal all can influence the work of adhesion required to pull the web from the surface. The proposed research will investigate the phenomena controlling the separation process. Given the complexity of the problem, the investigation could focus in depth on only a few of these factors or could have a more broad focus.
A unique piece of equipment the Web Adhesion and Drying Simulator, a laboratory device that incorporates the ability to measure peel force under simulated dryer conditions is available for this research.
Fiber-Fiber Bond Structural Characteristics
Timothy Patterson
School of Mechanical Engineering
The primary structural elements of paper are the fibers and the fiber-fiber bonds. It is well accepted that the fibers provide the majority of the structural strength of the sheet and that the function of the bonds is to provide for even load distribution. Given this, relationship there is a tendency to focus solely on the fiber structural characteristics when considering sheet structural properties. However, the relative bonded area and the strength of the bonds play significant roles in the relationship between tear and tensile properties, the ultimate tensile strength and in the creep behavior of the sheet.
It is generally assumed that when two fibers are in close proximity during the drying process hydrogen bonds will form as the water is removed and the fibers will be bonded together. Fiber conformability and external forces pushing the fibers in to intimate contact play a role in the total area that is bonded and the relative strength of the bond, which is presumably dependent on the number of hydrogen bonds formed. High strength sheets are assumed to have a high percentage of bonded area and high strength bonds, this is usually inferred through density and light scattering measurements. Recent work has shown that bonding affects the short time duration deformation and the creep deformation behavior of paper in the same way. A sheet can attain a “fully efficient” structure in which there is an excess or redundancy in bonding resulting in a sheet with the least deformation under load for the fiber used. Attaining the “fully efficient” structure requires sufficient bond strength and bond area. While the goal is straightforward the process used to reach the goal is not well understood.
Primarily due to a lack of suitable investigative tools, there is relatively little known about the structural characteristics of the fiber-fiber bond. A potential and not previously applied tool is the Atomic Force Microscope (AFM). While topographical “images” of a surface can be obtained, a potentially more useful capability is that of measuring elastic constants and friction characteristics of the surface. This is done by manipulating the chemical and physical characteristics of the AFM probe tip and cantilever.
The student project would involve developing the required AFM techniques and investigating the characteristics of the fiber-fiber bonds. The new AFM environmental stage being acquired by IPST will allow measurements to be made at different sample temperatures. A key factor is to insure that the observed phenomena are not artifacts of the measurement technique. Additional experimental data would be obtained using SEM and physical testing.
An AFM is currently available at IPST and would be used for this work. All additional required equipment is “standard” equipment readily available at IPST-GT.
Pulse combustors have been proposed for at least two paper making related uses, fluidized bed heating in black liquor gasification and as a pulsed impingement device for paper drying. The benefits derived from the use of pulse combustors include significantly enhanced heat and mass transfer, increased fuel efficiency and reduced NOx emissions. The theoretical and experimental investigations of pulse combustion have concentrated on the desired combustion chamber and tailpipe geometries, quantifying heat and mass transfer rates, and attempting to explain the increased mass transfer rates.
How the air fuel mixture is delivered to the combustion chamber is generally ignored or treated by a trial and error method. In small scale applications a simply flapper valve is often used. The valve is a hinged mechanism which opens when the combustion chamber pressure is at a low point allowing air and fuel to enter and closes when the combustion chamber pressure is a high point during the combustion process. Another design, which is more applicable to an industrial implementation, is a rotary valve; two cylinders with cut outs, one is stationary and the other rotates. The air and fuel are admitted through the rotary valve when the open area line up. This approach has high reliability, but the mixing mechanics are not well understood. A third design utilizes an “aerodynamic” valve which has significantly increased resistance to reverse flow in comparison to forward flow. The advantage of this option is that is has no moving parts. The valve chosen has an impact on flow dynamics inside the combustion chamber, which directly affects the combustion process. Regardless of the valve arrangement the energy input into the system must adhere to the Rayleigh criteria which dictates the timing of the energy input relative to the pressure oscillations.
The proposed project is to investigate the parameters controlling the combustion process with the intent of developing an understanding which will lead to a combustor which produces the maximum possible pressure oscillations. High pressure oscillations are required if impingement drying is to be optimized. Modeling, along with experimental work will be used to develop a fundamental understanding of the parameters governing the mixing process. The work will then be used to develop an optimized design.
Pulse combustors have been proposed for at least two paper making related uses, fluidized bed heating in black liquor gasification and as a pulsed impingement device for paper drying. The benefits derived from the use of pulse combustors include significantly enhanced heat and mass transfer, increased fuel efficiency and reduced NOx emissions. In an impingement drying application there will be interactions between impingement jets. This has been well studied for the case of steady flow jets. The work has shown that there are optimum jet geometrical arrangements and separation distances from the impingement surface.
In the case of pulse combustor driven impingement the flow is not steady, the flow reverses direction producing toroidal vortices around the nozzle. The vortices propagate in the jet direction until impacting the impingement surface and then propagate outward from the jet centerline. This produces complex jet interactions. There has been no previous work investigating the interaction of reversing impingement jets. It is unlikely that the primarily empirical results obtained for steady flow jets can be applied.
The proposed work will employ both experimental and CFD modeling techniques. The experimental work will make use of small scale pulse combustors, measurement of heat flux at the impingement surface and infrared imagery. The CFD modeling will build on current single jet modeling work. The intent will be to develop an understanding which will lead to the identification of a nozzle arrangement which maximizes heat flux and drying.
A piece of paper starts off as a wet floc of fibers and the properties of the paper depends strongly on how the floc is formed in the first place. Sludge dewatering has similar issues; strong flocs dewater well, weak ones do not. Fibers carry a negative charge and floc formation is initiated by adding a positively charged polymer to a suspension of fibers. Much work has been done on examining the floc as it forms. We have taken the opposite approach: we use high speed photography followed by image analysis to look at fibers that remain in the suspension and their distribution. In other words, studying the floc does not provide an understanding of the make-up of the fibers in the floc. Studying what’s left in the suspension does.
We have recently found (to our surprise) that a suspension containing fibers of various fiber lengths flocs instantly, whereas a suspension consisting of just short or long fibers does not. Flocculation is a balance of the shear forces that operate on the floc and tend to defloc it and the attractive forces that keep the floc together. The project will seek to develop a fundamental understanding of floc formation as a function of fiber length and distribution under different shear conditions and polymer loads. The practical implications are enormous. Even a small reduction in polymer load will reduce costs to the industry by tens of millions of dollars. A paper sheet that is more uniform will be even more valuable. The project will require high speed photography, image analysis, and scanning electron microscopy. Field trials could be run at one of the companies listed below. The project will qualify the student for employment in the paper, chemical, mining, and environmental industries.
This project is linked to the IPST Environmental and Recycle programs, which are sponsored by Georgia-Pacific, Eka Chemical, Bowater, Stora Enso, Abitibi Consolidated and Buckman Labs. Additional support (travel & supplies) will be provided by Stora Enso.
Internally Delaminated Fiber: A New Material?
Sujit Banerjee
 We have recently shown that refining virgin fiber (providing mechanical stress) leads to internal delamination: i.e. to the exposure of new internal surface. Measurements with radioactive water have shown that these fibers can accommodate an unusually large quantity of water that we call confined water. The broad objective of this project is to understand the properties of confined water and to develop means of manipulating it. For example, if we could introduce certain polymers or nanoclay into the internal void before drying the fiber, then we might be able to tailor specific properties into the fiber. These might include enhanced water absorbency, better shock resistance, etc.
The project has two parts: fundamental and applied. The fundamental aspect of the project is to understand the mechanism of delamination. Does this occur with all types of fibers and what are the conditions that promote it? We will need to model the forces that lead to this delamination, possibly using micromechanics. We are able to quantify the water held inside the matrix using radioactive water, and we will measure how the amount and nature of this water changes with the nature of the substrate and with processing conditions. Once the fundamentals are established – at least at a first cut – we will define or develop uses for this material, especially for consumer products.
Support (travel & supplies) will be provided by Georgia-Pacific’s research center at Neenah, WI as authorized by Frank Murray, Vice President, R & D.
A piece of paper starts off as a wet floc of fibers and the properties of the paper depends strongly on how the floc is formed in the first place. Sludge dewatering has similar issues; strong flocs dewater well, weak ones do not. Fibers carry a negative charge and floc formation is initiated by adding a positively charged polymer to a suspension of fibers. Much work has been done on examining the floc as it forms. We have taken the opposite approach: we use high speed photography followed by image analysis to look at fibers that remain in the suspension and their distribution. In other words, studying the floc does not provide an understanding of the make-up of the fibers in the floc. Studying what’s left in the suspension does.
We have recently found (to our surprise) that a suspension containing fibers of various fiber lengths flocs instantly, whereas a suspension consisting of just short or long fibers does not. Flocculation is a balance of the shear forces that operate on the floc and tend to defloc it and the attractive forces that keep the floc together. The project will seek to develop a fundamental understanding of floc formation as a function of fiber length and distribution under different shear conditions and polymer loads. The practical implications are enormous. Even a small reduction in polymer load will reduce costs to the industry by tens of millions of dollars. A paper sheet that is more uniform will be even more valuable. The project will require high speed photography, image analysis, and scanning electron microscopy. Field trials could be run at one of the companies listed below. The project will qualify the student for employment in the paper, chemical, mining, and environmental industries.
This project is linked to the IPST Environmental and Recycle programs, which are sponsored by Georgia-Pacific, Eka Chemical, Bowater, Stora Enso, Abitibi Consolidated and Buckman Labs. Additional support (travel & supplies) will be provided by Stora Enso.
Calcium and other metals in wood are released during the pulping process when the wood structure is broken down. The downstream impact of these metals depends on the nature of the metal-organic bonds as well as the solution composition, pH and temperature. Work is needed to improve our understanding of these bonds to reduce the scaling in digesters and black liquor evaporators. This work could also have relevance to biofuel processing from wood.
Experiments will be carried out with model compounds to better understand the nature of the bonds followed by work with industrial solutions. This work will involve development of a strong background in thermodynamics and organic chemistry. Existing facilities include pilot digesters, bomb reactors for studying thermal deactivation of the Ca-organic bonds, a fouling test cell and a pilot falling film evaporator.
IPST, ChBE and Chem are partners in a on-going investigation of crystallization in the Na-CO3-SO4 system. Complete characterization of the burkeite solid solution region, including the solid solution range, ordering of carbonate/sulfate and the true symmetry of the material, should help clarify the distinct transition from a sulfate rich binary salt solution to a carbonate rich binary salt. The fundamental knowledge gained will be utilized in both the pulp and paper and nuclear waste industries.
Existing crystallization facilities for this research include: batch crystallizers, fouling test cells, and a pilot falling film evaporator. Instrumentation, includes a Lasentec® FBRM® particle size probe and PVMTM in-process video microscope, which allows real-time examination of particle shape and agglomeration during evaporative crystallization. Analysis of the crystalline solids will make use of powder x-ray diffraction equipment located on campus. Where necessary, diffraction equipment located at nations synchrotron x-ray and neutron scattering facilities will also be employed.
Conversion of available lignocellulosic biomass has the potential to replace more than 30% of the petroleum consumption in the U.S., meeting the U.S. government’s 2030 target (1). Biorefineries, in which biomass is converted to various energy products and materials will be designed and built to accomplish this (2,3,4). Research on conversion of biomass to power, fuels, and chemicals is needed to make them a reality.
The research projects offered here focus on conversion of woody biomass to liquid fuels or power via thermochemical conversion route, with clean syngas as the intermediate energy product.
This project focuses specifically on quantifying pyrolysis and gasification characteristics (kinetics, product distribution, tar, other contaminants) from various feedstock at both elevated pressure and atmospheric pressure of woody biomass.
This project will be part of a larger program titled Biorefineries: Fuels, Chemicals, and Power from Lignocellulosic Biomass.
References
- Perlack, R.D. et al., Biomass as Feedstock for a Bioenergy and Bioproducts Industry: the Technical Feasibility of a Billion-Ton Annual Supply. Report nos. DOE/GO-102005-2135 and ORNL/TM-2005/66; prepared by Oak Ridge National Laboratory, Oak Ridge, TN. feedstockreview.ornl.gov/pdf/billion_ton_vision.pdf
- Ragauskas, A.J. et al., The Path Forward for Biofuels and Biomaterials, Science, vol. 311, p. 484-489 (Jan 27, 2006).
- Ragauskas, A.J. et al., From Wood to Fuels: Integrating Biofuel and Pulp Production, Industrial Biotechnology, 2(1):55-65 (Spring, 2006).
- Kamm, B., Kamm, M. Principles of biorefineries. Appl Microbiol Biotechnol (2004) 64: 137–145.
Conversion of available lignocellulosic biomass has the potential to replace more than 30% of the petroleum consumption in the U.S., meeting the U.S. government’s 2030 target (1). Biorefineries, in which biomass is converted to various energy products and materials will be designed and built to accomplish this (2,3,4). Research on conversion of biomass to power, fuels, and chemicals is needed to make them a reality.
The research projects offered here focus on conversion of woody biomass to liquid fuels or power via thermochemical conversion route, with clean syngas as the intermediate energy product.
This project focuses specifically on the development of hot gas cleanup and conditioning technologies to remove efficiently tar, alkali metals, sulfur, halides, and other contaminants.
This project will be part of a larger program titled Biorefineries: Fuels, Chemicals, and Power from Lignocellulosic Biomass.
References
- Perlack, R.D. et al., Biomass as Feedstock for a Bioenergy and Bioproducts Industry: the Technical Feasibility of a Billion-Ton Annual Supply. Report nos. DOE/GO-102005-2135 and ORNL/TM-2005/66; prepared by Oak Ridge National Laboratory, Oak Ridge, TN. feedstockreview.ornl.gov/pdf/billion_ton_vision.pdf
- Ragauskas, A.J. et al., The Path Forward for Biofuels and Biomaterials, Science, vol. 311, p. 484-489 (Jan 27, 2006).
- Ragauskas, A.J. et al., From Wood to Fuels: Integrating Biofuel and Pulp Production, Industrial Biotechnology, 2(1):55-65 (Spring, 2006).
- Kamm, B., Kamm, M. Principles of biorefineries. Appl Microbiol Biotechnol (2004) 64: 137–145.
Conversion of available lignocellulosic biomass has the potential to replace more than 30% of the petroleum consumption in the U.S., meeting the U.S. government’s 2030 target (1). Biorefineries, in which biomass is converted to various energy products and materials will be designed and built to accomplish this (2,3,4). Research on conversion of biomass to power, fuels, and chemicals is needed to make them a reality.
The research projects offered here focus on conversion of woody biomass to liquid fuels or power via thermochemical conversion route, with clean syngas as the intermediate energy product.
This project focuses specifically on the design and simulation of integrated biorefineries with lignocellulosic feedstock.
This project will be part of a larger program titled Biorefineries: Fuels, Chemicals, and Power from Lignocellulosic Biomass.
References
- Perlack, R.D. et al., Biomass as Feedstock for a Bioenergy and Bioproducts Industry: the Technical Feasibility of a Billion-Ton Annual Supply. Report nos. DOE/GO-102005-2135 and ORNL/TM-2005/66; prepared by Oak Ridge National Laboratory, Oak Ridge, TN. feedstockreview.ornl.gov/pdf/billion_ton_vision.pdf
- Ragauskas, A.J. et al., The Path Forward for Biofuels and Biomaterials, Science, vol. 311, p. 484-489 (Jan 27, 2006).
- Ragauskas, A.J. et al., From Wood to Fuels: Integrating Biofuel and Pulp Production, Industrial Biotechnology, 2(1):55-65 (Spring, 2006).
- Kamm, B., Kamm, M. Principles of biorefineries. Appl Microbiol Biotechnol (2004) 64: 137–145.
Stress Assisted Corrosion (SAC) in Carbon Steel Boiler Tubes
Preet M. Singh
School of Materials Science and Engineering
Corrosion fatigue (CF) or stress assisted corrosion (SAC) of carbon steel tubes from waterside in recovery and utility boilers is a major problem in the pulp and paper industry. Stress assisted corrosion in boiler tubes can not be easily detected as it starts from the inside of the tube. Radiography is typically used detect these cracks but it is not only expensive but is also not always possible, especially in areas with physical constraints. Still it is very important to know or be able to predict the crack depth to assess tube failure risks. Initial work at IPST @ GaTech has shown that a significant number of failed boiler tubes have inner decarburized layer with large grain size. This layer may extend to almost third of tube thickness. It is hypnotized that large grained carbon steel layer with lower yield strength may help with earlier crack initiation and higher growth rate compared to normal pearlitic microstructure. Indications from failure analysis and field experience are that the corrosion fatigue cracks in boiler tubes do not grow continuously. However to predict remaining life of boiler tubes and to avoid unexpected water leaks in kraft recovery boiler s to avoid explosions, it is important to understand and quantify the role of microstructure and other operational parameters on crack initiation and growth rate. This project will involve experimental work as well as development of a model to predict crack initiation and growth under different scenarios.
Preet M. Singh
School of Materials Science and Engineering
There is an imminent need to find alternative and renewable fuels to meet constantly increasing energy demand and decreasing petroleum reserves. One of the proposed methods to produce bio-fuel is through pre-extraction of hemicelluloses from wood chips before the pulping process. In the process a number of naturally occurring extractives will also be removed from the wood. Recent study has shown that some of these extractives may affect corrosion of carbon steel in resulting black liquor carbon steel equipment. Main objective of this project is to systematically identify naturally acting activators and inhibitors and evaluate the effect of different extraction schemes on corrosivity of black liquors from extracted softwood and hardwood chips. Student will look at the mechanisms by which different organic extractives in selected hardwoods and softwoods will affect black liquor corrosivity. Work will involve in-situ analysis of films by coupling electrochemical testing with Raman spectroscopy to identify the mechanisms by which organics interact with the metal surface at different applied potentials.
Novel Wood Pulp Composites
Rosario A. Gerhardt
School of Materials Science and Engineering
Wood pulp, whose main component is cellulose, is a dielectric. However, it is well known that addition of conducting fillers can render any insulator conducting. This occurs via a phenomenon known as percolation. Therefore, controlled addition of nanosized conductive fillers has the potential to result in the development of an inexpensive method for the fabrication of “conducting” paper. Such paper may be useful in applications that require the flexibility of paper but can carry an electrical current when desired. These include electromagnetic shielding covers, electrodes, displays, etc.
Wood is an anisotropic substance as depicted in the images below. The distribution of voids is different along the different growth directions: longitudinal, transverse and tangential. Thus, the dielectric properties are expected to depend on the volume fraction of voids and their size, shape and distribution. Previous research by this investigator has shown that the dielectric response of different woods is a function of the wood microstructure.1
  
It is proposed here to first evaluate the structure and properties of various grades of paper in order to identify the most ideal wood pulp microstructure for the introduction of the inorganic conducting fillers. The plan is then to develop the desired architecture that will permit the fabrication of paper that would have different properties along the length of the paper versus that through the thickness of the paper.
1K.J. Duchow and R.A. Gerhardt, "Dielectric Characterization of Wood and Wood Infiltrated with Ceramic Precursors," Mat.Sc.& Eng. C4, 125-131(1996).
Surface modification of porous membranes for lateral flow applications
Prof. Rina Tannenbaum
MSE
Microporous nitrocellulose (NC) membranes were one of the first synthetic membranes and have enjoyed a successful history as a filtration medium for the better part of a century. One inherent characteristic of nitrocellulose membranes is a remarkably high binding capacity for ionically charged and highly polar molecules. In most filtration applications, the binding characteristics of nitrocellulose are unfavorable and have proved rather prohibitive to the proliferation nitrocellulose as a filtration media. To date, the main application of nitrocellulose membranes is in the specialized field of immunoassay technology. Nitrocellulose membranes comprise the dominant media in what has become a multibillion dollar market encompassing medical, environmental, and clinical industries.
The considerable advancement of immunoassay technology has been driven by the investment of extensive capital, resources, and talent in research and development; however, such efforts have been focused solely in the areas of assay chemistry and mechanics. In contrast, little effort has been paid to improving the science or performance of immunoassay membrane materials. Today, modern nitrocellulose membranes are manufactured with virtually the same casting process technology developed almost 100 years ago. In this process, solutions of nitrocellulose in a mixed ether-alcohol solvent are cast into films on a stainless steel belt. Membrane pore structures are formed by the evaporation of the volatile solvents. As it turns out, cast microporous nitrocellulose membranes are far from the ideal substrate material for immunoassays. Wide variability in physical structure derived from the evaporative casting process used to fabricate the membranes and fundamental chemical properties of nitrocellulose adversely affect immunoassay performance and repeatability.
In this project we will apply our extensive experience with surface modifications by constructing an adsorbed self-assembled multi-layer comprised of alternating-charge polyelectrolytes and polymer-polyelectrolyte block copolymers in the pores of the nitrocellulose. This will allow us to modulate the surface properties of the nitrocellulose according to a pre-determined requirement, and moreover, regulate the hydrophilicity (or hydrophobicity) of the surface and adjust it for lateral flow and other separation processes. Specifically, we will concentrate on the relationships between surface structure and the ability to bind proteins from a wicking solution. By studying the impact of pH and ionic strength on protein adsorption, we will attempt to characterize the role and nature of the electrostatic interactions involved in the adsorption process to better understand how these interactions are influenced by the charge and structure of the immobilized, self-assembled polyelectrolyte complex multilayers at modified membrane surfaces. Clearly, this approach can also be extended to other membrane material, such as cellulose, cellophane and synthetic membranes such as sintered polyethylene.
The control of particle dispersion in biodegradable nanocomposites
Prof. Rina Tannenbaum
MSE
One of the current focus areas within the field of nanotechnology is the design and synthesis of polymer nanocomposites (PNC), which represent an attractive new class of materials. Depending on the type of nanoparticles used, the physical properties of the resulting PNC may be superior to those of the pure polymer. To extend the range of applications for PNCs and tap into their full potential, new challenges in composite processing must first be overcome. Specifically, the control of the chemical and surface properties of the nanoparticles is essential for achieving a proper distribution of the particulate phase throughout the polymer matrix without introducing defects in the interphase is a requirement for optimizing the properties of PNCs. Uniform dispersion of the particulate phase is especially important for those PNCs in which the formation of a percolating network of nanoparticles is necessary for achieving desired mechanical, electrical or thermal properties. Conversely, inhomogeneities in particle size and particle dispersion reduce the mechanical properties of the composite and negate the unique advantages of PNCs.
Therefore, the problem to be addressed in this proposed work is the development of a method to better solubilize, disperse and stabilize the particulate phase in the polymer matrix during the fabrication of biodegradable PNCs. Since high particle surface area translates to high surface energy and low thermodynamic stability, there is a strong tendency for the nanoparticles to agglomerate so the surface energy of that phase can be reduced. Therefore, an integral step in achieving nanoparticle dispersion is demonstrating an effective means of neutralizing the agglomeration tendency. We would like to pursue a novel strategy, a “nano” version of the classical reaction injection molding (RIM) technique, in which the formation of the nanoparticles (such as metal oxides clusters) will occur “in-situ” in a solvent consisting of a low molecular-weight polymer precursor, followed by the “locking in place” of the fine homogeneous dispersion during matrix consolidation (polymerization) of the solvent. In reactive molding, polymerization of the entire polymer matrix takes place directly in the mold. Since the viscosity of a system of monomers or low molecular weight pre-polymers is inherently low, this is conducive to fine mixing of particulate and monomer phases, and no additional solvents need to be added to lower system viscosity. By selecting monomers which are able to solubilize the nanoparticles as they are formed, it should be possible to achieve an excellent particle distribution in the final PNC.
In view of the increasing emphasis on developing and promoting biobased products, there is also a need to identify reactive molding components that can be derived from natural resources, such as cellulose starch or silk fibroin as the matrix materials. The reaction chemistry of systems of this type needs to be characterized, with an emphasis on curing and molding behavior. In addition, the physical properties of the consolidated PNCs must be fully characterized.
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