1,720,969 research outputs found
Hot Water Extraction and Subsequent Kraft Pulping of Pine Wood Chips
Get PDFThis research investigated the effects of pre-extraction time, temperature, and pH on the rate and quantity of sugars recovered from Loblolly pine wood chips and the impact this treatment has on pulp kappa number and yield. Composition analysis of raw chips, extracted chips, pulp, and hydrolyzate were performed to assess the hemicellulose extraction efficiency and subsequent loss during kraft pulping of Loblolly pine. A pseudo kinetic model of prehydrolysis extraction was developed from the hydrolyzate sugar concentration data.
Preliminary experiments demonstrated the potential for influencing pulp properties and sugar recovery in hydrolyzate through on-line control of prehydrolysis pH, reaction temperature, and time. A second set of experiments examined these factors and added a presoak period to the design matrix. A third set of experiments used a best case of pre-extraction conditions to test five potential pulping additives.
It was concluded that the extraction rate for all sugars was increased with either increasing temperature from 140 to 170°C or decreasing pH from 4.5 to 3.0. The hydrolysis was selective for hemicellulose as opposed to cellulose by using temperature at 140°C. Both pH and temperature also impacted the degradation rate of sugars in solution. The 24 hour presoak at 25°C with various pH levels had no measurable effect on hydrolysis rate or pulp yield.
The additives tested in this research: anthraquinone, acetaldehyde, ethanolamine, lithium aluminium hydride, and hydroxylamine, were not successful in recovering pulp yield from extracted chips to that of a standard kraft cook with the conditions tested. More work could be justified with hydroxylamine or to test the use of anthraquinone in conjunction with hydroxylamine or another successful additive.
A pseudokinetic model of the extraction was calculated using an activation energy of 27 kcal/mole for hemicellulose hydrolysis and a term for the acid concentration. This modified H-factor model described the sugar extraction data except when significant degradation of sugars was observed. The data for chip weight loss and pulp yield also fit a smooth curve when plotted against the modified H-factor
Kinetic Investigation and modeling of cellulase enzyme using Non-crystalline cellulose and Cello-oligosaccharides
Get PDFEnzymatic hydrolysis of Cellulose depends on many factors; physical properties of substrate (composition, crystallinity, degree of polymerization etc.), enzyme synergy (origin, composition etc.), mass transfer (substrate adsorption, bulk and pore diffusion etc.) and intrinsic kinetics. Most of these effects occur concurrently, therefore cannot be distinguished from each other. Accurate assessment of intrinsic kinetics requires pure form of cellulosic substrates unhindered by mass transfer resistances, or physical factors of substrate. Non-crystalline cellulose (NCC) and Cello-oligosaccharides (COS) are the products of our laboratory which were used as substrates to study the enzymes. The most notable difference seen in this study is that the activity measured by initial rates against NCC is two orders of magnitude higher than that against crystalline cellulose. Since removal of physical barrier primarily increases the hydrolysis by Endo-glucanase, a significant amount of cello-oligosaccharides and cellobiose was seen to accumulate in hydrolysis of NCC. Cellobiose gradually disappeared whereas cello-oligosaccharides remained constant throughout the enzymatic hydrolysis. The actions of Endo-Glucanases and Exo-Glucanases during the synergism were much more easily distinguished when NCC was used as the substrate. From the experiments conducted on COS, it became apparent that Exo-glucanases cannot act on the soluble substrates. On the other hand, ß-glucosidase acts on the cellobiose as well as the cello-oligosaccharides. To find the inhibitory effects, hydrolysis intermediates and products (NCC, cello-oligosaccharides, cellobiose and glucose) are externally supplied at the initial stages of hydrolysis. The time course data on cellulose, COS, cellobiose, and glucose were taken and incorporated into a comprehensive kinetic model that accounts for inhibitory effects of reaction intermediates and products (cello-oligosaccharides, cellobiose and glucose) to determine the kinetic parameters. The model has shown a good agreement with experimental data
Application of Near Infrared Spectroscopy to Pulp Yield and Kappa Number Estimation
Get PDFThis thesis presents an investigation into near infrared (NIR) spectroscopy as a technique for determining pulp yield and kappa number for kraft pulp and black liquor samples. It is believed that proper spectra collection and preprocessing techniques combined with a linear regression analysis can produce models that accurately predict pulp yield and kappa number. Currently, no instrument exists for estimating these values simultaneously. Methods for estimating yield and kappa number consist of lengthy lab based wet chemistry techniques. NIR reflectance spectroscopy has the potential of providing a single, relatively simple instrument solution for both of these measurements. NIR transmission spectroscopy of the black liquor may provide further information and process control capability. The ability to predict yield and kappa number is a valuable process control technology for use in kraft mills.
Samples of pulp with yield and kappa number ranges typical of mills were generated from the batch kraft digestion of softwood chips and liquor of varying EA. NIR spectra of the samples were collected using little or no sample pretreatment. The idea was to analyze the samples under conditions similar to a non-idealized mill environment. Different prototype NIR spectrometers were used covering a major portion of the NIR spectrum. Correlations between the pulp yield, kappa number, NIR reflectance data of the pulp and NIR transmission data of the black liquor have been developed. These lab based calibrations were used to predict kappa number and yield values for lab generated pulp samples. The calibration models were also able to accurately predict kappa values for unknown mill pulp samples
Optimization of Ethanol Production from Concentrated Substrate
Get PDFThis research optimizes ethanol production from high concentrations of cellulosic substrates in order to produce ethanol economically from renewable resources. This study identifies and quantifies the factors that influence ethanol yield on high solids biomass slurries during saccharification followed by fermentation (SFF) processes leading to development of a computational fluid dynamics (CFD) model. This model describes slurry rheology in terms of measurable parameters and slurry/biomass characteristics as these parameters undergo transformation during the SFF process.
To obtain five percent (v/v) ethanol production needed for an economically viable industrial-scale ethanol distillation, high carbonate concentration is required. High carbonate concentration can be achieved only with high initial cellulose concentration combined with a favorable conversion yield of cellulose into soluble sugars.
Many researchers have reported repeatedly that solid concentrations above 10 percent resulted in poor ethanol yield due to inefficient mass transfer and to the different operating temperatures required for enzymatic hydrolysis and fermentation.
To develop data for a full scale design, ethanol fermentation of concentrated Solka Floc is evaluated in a three-liter bioreactor. The effects of mixing are evaluated using computational fluid dynamics (CFD) simulations of the three-liter reactor
A Framework For Optimal Polygeneration Product Allocation
No full textPolygeneration facilities, such as the integrated biorefinery, have the opportunity to provide a strong, self-dependent, sustainable alternative for the production of bulk and fine chemicals, e.g. polymers, fiber composites and pharmaceuticals as well as energy, liquid fuels and hydrogen. Although most of the fundamental processing steps involved in these polygeneration facilities are well-known, there is a need for a methodology capable of evaluating the integrated processes in order to identify the optimal set of products and the best route for producing them. The complexity of the product allocation problem for such processing facilities demands a process systems engineering approach utilizing process integration and mathematical optimization techniques to ensure a targeted approach and serve as an interface between simulation work and experimental efforts. The objective of this work is to assist potential and existing polygeneration facilities in evaluating the profitability of different possible production routes and product portfolios while maximizing stakeholder value through global optimization of the supply chain. To meet these ends, a mathematical optimization based framework is being developed, which enables the inclusion of profitability measures and other techno-economic metrics along with process insights obtained from experimental as well as modeling and simulation studies
Sequestration of Co2 by Chemically Reactive Aqueous K2co3 in High Efficiency Adsorbents Using Microfibrous Media Entrapped Support Particulates
Get PDFThis work is mainly focused on developing a new adsorptive material and regenerable system for CO2 removal to supply CO2-free gas stream for low temperature and low CO2 concentration applications, such as Alkaline Fuel Cells, Metal-Air batteries, and portable air-purifying respirators. A novel microfibrous media has been introduced for CO2 filtration from wet gas streams at room temperature. The microfibrous media was prepared by uniformly dispersing activated carbon particulates in the nickel fiber matrix via wet layer paper-making/sintering processes. The use of microfibrous media in a composite bed maximizes the breakthrough capacity per unit volume and promotes high accessibility. The microfibrous media synergically combines the high contacting efficiency of the microfibrous matrix and the small internal mass transfer resistance of the small particulates. The capacity of the microfibrous media can be reversibly
recovered. The incorporation of microfibrous media to the Sodalime was observed. The result shows 120% improvement in the breakthrough capacity compared with the packed bed of the Sodalime with the same volume. This approach can be applied to miniaturize the reactor size, reduce thermal mass, and enhance the process intensification
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Nanoparticles and Nanofibers Production Using Supercritical Carbon Dioxide
Get PDFThis dissertation deals with the production of nanostructured organic, inorganic and biopolymer materials using supercritical carbon dioxide. Over the past decade, supercritical fluids (SCFs) have emerged for particle formation due to SCFs adjustable solubility and significantly high diffusivity. Various methods have been developed, which can be classified into two basic processes: (a) rapid expansion of supercritical solutions (RESS) for processing CO2-soluble materials, (b) and supercritical antisolvent (SAS) for processing CO2-insoluble materials. In this work, further developments in both the methods have been made to overcome the existing challenges and to achieve new nanostructures.
Chitin nanofibers are potentially of use in many biomedical and pharmaceutical applications. But, due to highly crystalline nature, it is very difficult to convert into a
nanofibrous form. In this work, a SAS method is used to produce chitin nanofibers of average diameter 84 nm using hexafluoroisopropanol as solvent while preserving the molecular structure of the processed chitin.
Using SAS with enhanced mass transfer, hydrocortisone nanoparticles were produced. A sonicating horn at 20 kHz frequency was used to enhance the mass transfer between solvent-antisolvent and to avoid agglomeration of nanoparticles. Particles as small as 180 nm are obtained using this method and the size was easily controlled using the ultrasound intensity.
The SAS process was further extended by including a chemical reaction. A new supercritical fluid based method, SAS-R was developed to form silica coating onto gold nanoparticles. Here supercritical CO2 is utilized both as an antisolvent and as a reactant. Silica-coated gold particles of 30-300 nm size were obtained with the coating thickness of as low as 20 nm. Pressure can be used to control coating thickness. Such particles are of interest in producing optical switches and biosensors.
In the conventional RESS process, a supercritical solution is rapidly expanded through a nozzle to precipitate the solute as microparticles. The modeling of RESS has shown that the precipitated particles at the nozzle tip are of the order of 5-25 nm in size. However, for most solutes, the final particles experimentally obtained are in the order of 800-3000 nm in size, due to growth by coagulation in the expansion chamber. Another difficulty is that most pharmaceutical compounds have poor solubility in supercritical carbon dioxide. In this work, both challenges are addressed by utilizing a cosolvent that is solid at the nozzle exit conditions. The solid cosolvent (SC) enhances the solubility and provides barrier for coagulation in the expansion chamber. The solid cosolvent is later remove from the solute particles by lyophilization (sublimation). The new process is termed as RESS-SC. A suitable solid cosolvent is menthol which is solid below 35 oC (typical nozzle exit temperature is 5-30 oC) and can be easily sublimed. RESS-SC concept is demonstrated by producing nanoparticles of griseofulvin, 2-aminobenzoic acid, phenytoin, and acetazolamide. A significant increase in the solubility and reduction in the particle size is observed in all four cases
Bioconversion of Lignocellulosic Material into Ethanol: Pretreatment, Enzymatic Hydrolysis, and Ethanol Fermentation
Get PDFFour different novel processes, ammonia recycle percolation (ARP), low-liquid ARP, two-stage (hot water-ARP) percolation, and soaking in aqueous ammonia (SAA) at room/moderate temperature, were investigated for pretreatment of lignocellulosic material (corn stover). These pretreatment methods were aimed at improving enzymatic hydrolysis and increasing the fermentability of the biomass.
The ARP process feeds aqueous ammonia into a flow-through reactor at high temperatures and high pressures. This method is highly effective in delignifying biomass, reducing the lignin content by 70?85%. FTIR (Fourier transform infrared spectroscopy) and lignin staining results verify the lignin removal by ARP process. The SEM (scanning electron microscope) pictures indicate that the biomass structure is deformed and its fibers are exposed by the pretreatment. ARP pretreatment increases the crystallinity index as the amorphous portion of biomass is removed. The crystalline structure of the biomass cellulose, however, is not changed by the ARP treatment.
Low-liquid ammonia treatment method reduced the liquid throughput to the level of 3.3 mL of liquid per gram of corn stover, leading to a shorter residence time and lower energy requirements. A high degree of delignification is not necessary to attain high enzymatic digestibility or high ethanol yield. An ethanol yield of 85% of the theoretical maximum was achieved using the low-liquid ARP treatment with SSF (simultaneous saccharification and fermentation) process.
The two-stage process combines the hot water and ARP treatments, using a flow-through (percolation) reactor. The first stage hot water processing removes hemicellulose and the second stage ARP performs the delignification. A high fractionation of the biomass was achieved using the two-stage treatment; resulting in 92–95% xylan hydrolysis and xylose yield of 83–86% with 75–81% lignin removal. The solid residue after two-stage treatment contained 78–85% cellulose.
A simpler alternative pretreatment process was also investigated. In this process, corn stover was soaked in 30% aqueous ammonia for 10 days at room temperature (SAA at room temperature) or in 15% for 12 hours at 60?C (SAA at moderate temperature), with no agitation under atmospheric pressure in a closed vessel. This process retains 85% of the xylan and removed 55–67% of the lignin. The treated corn stover was fermented to ethanol by the simultaneous saccharification and co-fermentation process using a recombinant E.coli. This organism utilized both glucan and xylan in the biomass, producing ethanol yield of 77.0–77.3% based on total glucan and xylan, and an ethanol concentration of 19.2–19.8 g/L . The advantage of this method is that the process is simple and yet provides high fermentability. The ethanol yield based on glucan alone was 113–116%, a clear indication that most of xylan is converted to ethanol during the SSCF
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