Estimation of temperature transients for biomass pretreatment in tubular batch reactors and impact on xylan hydrolysis kinetics

A combined heat transfer/kinetic model was developed to quantify temperature variations in small tubular batch reactors and estimate the effect of deviations from isothermal operation on the kinetics of biomass pretreatment. Assuming that heat transfer was dominated by conduction in the radial direction, a classic parabolic time-dependent partial differential equation was applied to describe the temperature in the system and dedimensionalized to provide a single solution for application to all situations. A dimensionless expression for the reaction kinetics for xylan hydrolysis was then developed, and a single parameter expressed as the dimensionless ratio of the first-order rate constant times the tube radius squared divided by the thermal diffusivity was found to control the reaction rate. Three different characterizations of the deviation between the concentration profile predicted for isothermal xylan hydrolysis and that based on the transient temperature were directly related to this dimensionless rate constant parameter for both catalyzed and uncatalyzed hydrolysis kinetics. These results were then used to project the relationship between deviations in yield from isothermal results and the tube radius and reaction time.     

Alternative fuels from biomass and their impact on carbon dioxide accumulation

Applied Biochemistry and Biotechnology - A number of transportation fuels can be produced from renewable resources. The major fractions of lignocellulosic biomass, cellulose and hemicellulose, can...     

Methodology for evaluating the economics of biologically producing chemicals and materials from alternative feedstocks

Applied Biochemistry and Biotechnology - A wide range of chemicals and materials can be produced from renewable feedstocks through bioconversions. An iterative, progressively detailed technology...     

Introduction to the Proceedings of the Twelfth Symposium on Biotechnology for Fuels and Chemicals

Applied Biochemistry and Biotechnology -     

Predicted effects of mineral neutralization and bisulfate formation on hydrogen ion concentration for dilute sulfuric acid pretreatment

Dilute acid and water only hemicellulose hydrolysis are being examined as part of a multiin stitutional cooperative effort to evaluate the performance of leading cellulosic biomass pretreatment technologies on a common basis. Cellulosic biomass, such as agricultural residues and forest wastes, canhave a significant mineral content. It has been shown that these minerals neutralize some of the acid during dilute acid pretreatment, reducing its effectiveness, and the higher solids loadings desired to minimize costs will require increased acid use to compensate. However, for sulfuric acid in particular, an equilibrium shift to formation of bisulfate during neutralization can further reduce hydrogen ion concentrations and compound the effect of neutralization. Because the equilibrium shift has a more pronounced effect at lower acid concentrations, additional acid is needed to compensate. Coupled with the effect of temperature on acid dissociation, these effects increase acid requirements to achieve a particular reaction rate unless minerals are removed prior to hydrolysis.     

A comparison of the photoelectron spectrum and crystal orbital calculations of polyethylene

The experimentally observed photoelectron spectrum of C₃₆H₇₄ is compared with theoretical calculations based on crystal orbital theory at vario     

Queueing with Cyclic Arrival Distributions and Variable Service Facilities: A Simulation Approach

This paper develops a near optimal policy for opening a second counter in a quick-service restaurant when n persons are in the first line, given that the arrival process is cyclic rather than purely stationary. A simulation was written in GPSS which permitted the use of different arrival generators during different time segments of the simulated day. Results indicate that as n is varied, waiting time and utilization levels exhibit an S-shaped curve between the pure 1 facility and the 2 facility cases. Results also indicate that a cyclic arrival process greatly increases (relative to the case of exponential arrivals) mean waiting time, facility utilization, and the range of n. Finding the optimal (least cost) value of n is illustrated for cases in which costs of customer waiting time can be meaningfully imputed.     

Introduction to session 2

Applied Biochemistry and Biotechnology -     

Introduction to the Proceedings of the Sixteenth Symposium on Biotechnology for Fuels and Chemicals

Applied Biochemistry and Biotechnology -