Shri Ramaswamy

Process modeling and analysis of pulp mill-based integrated biorefinery with hemicellulose pre-extraction for ethanol production: a comparative study.

Pulp and paper mills represent a major platform to use more effectively an abundant, renewable bio-resource - wood. Modification of the modern day pulp mills into integrated forest biorefineries (IFBR) presents an excellent opportunity to produce, in addition to valuable cellulose fiber, co-products including fuel grade ethanol and additional energy, thus resulting in increased revenue streams and profitability and potentially lower the greenhouse gas emissions. A process model to simulate the integrate forest biorefinery manufacturing pulp and other co-products has been developed. This model has been used to compare three integrated biorefinery scenarios: the conventional Kraft pulping process, the pulp mill-based IFBR with hemicelluloses extraction prior to pulping for ethanol production, and the pulp mill-based IFBR with both pre-extracted hemicelluloses and the short fiber for ethanol production. Based on a fixed feedstock throughput of 2000 dry Mg wood/day, results show that the pulp mill-based IFBR with both pre-extracted hemicelluloses and the short fiber cellulose converted to ethanol can produce 0.038 MM m(3) (10.04 MM gal) ethanol per year at a minimum ethanol selling price (MESP) of

Reaction Kinetics of the Hydrothermal Treatment of Lignin

491/m(3) (

Separation and Purification Technologies in Biorefineries

1.86/gal). The economic feasibility of IFBR can be further improved by using further improvements in the pre-extraction process, other biomass such as corn stover for producing ethanol, and taking advantage of the economies of scale.

Modeling Biomass Gasification Using Thermodynamic Equilibrium Approach

Lignins derived from abundant and renewable resources are nontoxic and extremely versatile in performance, qualities that have made them increasingly important in many industrial applications. We have shown recently that liquefaction of lignin extracted from aspen wood resulted in a 90% yield of liquid. In this paper, the hydrothermal treatment of five types of lignin and biomass residues was studied: Kraft pine lignin provided by MeadWestvaco, Kraft pine lignin from Sigma-Aldrich, organosolv lignin extracted from oat hull, the residues of mixed southern hardwoods, and switchgrass after hydrolysis. The yields were found dependent on the composition or structure of the raw materials, which may result from different pretreatment processes. We propose a kinetic model to describe the hydrothermal treatment of Kraft pine lignin and compare it with another model from the literature. The kinetic parameters of the presented model were estimated, including the reaction constants, the pre-exponential factor, and the activation energy of the Arrhenius equations. Results show that the presented model is well in agreement with the experiments.

Moisture Sorption, Transport, and Hydrolytic Degradation in Polylactide

Separation and purification processes play a critical role in biorefineries and their optimal selection, design and operation to maximise product yields and improve overall process efficiency. Separations and purifications are necessary for upstream processes as well as in maximising and improving product recovery in downstream processes. These processes account for a significant fraction of the total capital and operating costs and also are highly energy intensive. Consequently, a better understanding of separation and purification processes, current and possible alternative and novel advanced methods is essential for achieving the overall technoeconomic feasibility and commercial success of sustainable biorefineries.

Student Peer Teaching: An Innovative Approach to Instruction in Science and Engineering Education

In this paper, the thermodynamic equilibrium models for biomass gasification applicable to various gasifier types have been developed, with and without considering char. The equilibrium models were then modified closely matching the CH4 only or both CH4 and CO compositions from experimental data. It is shown that the modified model presented here based on thermodynamic equilibrium and taking into account local heat and mass considerations can be used to simulate the performance of a downdraft gasifier. The model can also be used to estimate the equilibrium composition of the syngas. Depending on the gasifier type and internal fluid flow, heat and mass transfer characteristics, with proper modification of the equilibrium model, a simple tool to simulate the operation and performance of varying types of biomass gasifier can be developed.

Transient moisture diffusion through paperboard materials

Management of moisture penetration and hydrolytic degradation of polylactide (PLA) is extremely important during the manufacturing, shipping, storage, and end-use of PLA products. Moisture transport, crystallization, and degradation, in PLA have been measured through a variety of experimental techniques including size-exclusion chromatography, differential scanning calorimetry, and X-ray diffraction. Quartz crystal microbalance and dynamic vapor sorption experiments have also been used to measure moisture sorption isotherms in PLA films with varying crystallinity. A surprising result is that, within the accuracy of the experiments, crystalline and amorphous PLA films exhibit identical sorption isotherms.

Moisture Diffusion Inside Paper Materials in the Hygroscopic Range and Characteristics of Diffusivity Parameters

This paper reports the results of a pilot-study in a senior paper science and engineering class, of an innovative instructional method designed to foster student problem-solving and in-depth learning of material, namely, student peer teaching. We review related literature focusing on active learning methods in science and engineering education, describe the method of student peer teaching used in this pilot-study, present the evaluation method and results, and discuss implications for further development of this method of instruction. Results suggest that students were able to effectively teach significant curricular content. In addition, the method of student peer teaching served important purposes in helping students develop in-depth understanding and expertise in the issues related to their teaching session, as well as teaching and presentation skills which will be useful in their professional practice. However, students expressed concern that, while achieving in-depth learning of the content of their teaching session, they tended to focus on the content area of their teaching session at the expense of other content areas and may not have learned as well from other students as from the Professor. We recommend a modified structure for student peer teaching which incorporates cooperative learning methods; increased Professor involvement in class sessions, in the role of the mentor; and modifications in performance evaluation methods to ensure ongoing student monitoring of progress and self-assessment. The method of student peer teaching, in science and engineering education, combined with cooperative learning methods, is viewed as a major extension of cooperative learning methods, used in the service of preparation for professional careers.

Biorefinery co-products : phytochemicals, primary metabolites and value-added biomass processing

Abstract The performance of many products such as those made of containerboard or other paperboards is sensitive to moisture. Transient moisture profiles result in heterogeneities in mechanical properties and can often lead to catastrophic failure. Viewed as a composite porous medium the system comprises hygroscopic fibers and void spaces both of which are continuous. Furthermore, both phases conduct moisture by diffusion and for typical paperboards diffusion through the fiber matrix predominates at high moisture contents whereas vapor phase diffusion through the void space is dominant at lower values. Depending upon the external and initial conditions, competition between these two pathways and local sorption interplay and produce interesting effects, which can have significant impact on the mechanical performance of the composite medium. In order to delineate the different effects that can occur, we used a mathematical model for unsteady state diffusion to analyze the case of transient moisture transport through a paperboard exposed to differential humidity conditions on either side. Diffusion is assumed to occur along the thickness direction in the void space and in the fiber space. Local uptake of moisture is represented by the linear driving force approximation. A numerical solution of the mathematical model is sought. The dominant path for moisture transport can undergo a change from the fibers to the void spaces under large humidity differentials. A fiber conduction layer whose thickness develops with time and reaches a constant value at steady state is found. This raises the possibility of moisture response, which could depend on the direction of diffusion for significantly heterogeneous media. Another interesting feature is the development of minima in the moisture flux versus time curves, which are sensitive to the diffusion and local sorption parameters. Tracking such minima can provide a good method to tune the model parameters based on experimental flux data. The role of the interfacial region between the layers can affect the overall resistance and alter moisture content profiles significantly. Since similar ‘two-equation’ models have been proposed for other transport processes such as heat and momentum transfer, these results can have wider applicability. In particular, steady and unsteady profiles and fluxes can be exploited to yield information about the local and global transport coefficients for the heterogeneous medium under consideration.

Process Modeling of Comprehensive Integrated Forest Biorefinery—An Integrated Approach

Abstract Some current models for moisture diffusion in paper in the hygroscopic range are analyzed. In general, two types of diffusion models can be recognized. Models of the first type treat paper as a homogeneous medium with moisture flux that is proportional to the gradient in moisture content. Although useful in some instances this approach fails frequently because it homogenizes the internal dynamics and relaxation processes occurring within the paper material. Recent studies have shown that a subtler approach which treats paper as a composite of fibers and void spaces is more successful at describing moisture transport dynamics. A review of these studies along with a generalization of this approach to three dimensions is considered here. The parameters appearing in such models can be identified with the physical processes of diffusion through the void space and through the fiber matrix. Diffusivities in these individual phases are supplemented by a local kinetic coefficient representing moisture flux interchange between the void and fiber phases. When the local moisture exchange coefficient takes on large values, the fibers and the void spaces are at local equilibrium with no net exchange of moisture. Under such conditions, the model reduces to the simpler Fickian diffusion model with nonlinear moisture diffusivity equivalent to earlier models.