In this paper we report a novel four-step process for the production of jet and diesel fuel range alkanes from hemicellulose extracts derived from northeastern hardwood trees. The extract is representative of a byproduct that could be produced by wood-processing industries such as biomass boilers or pulp mills in the northeastern U.S. The hemicellulose extract tested in this study contained mainly xylose oligomers (21.2 g/l xylose after the acid hydrolysis) as well as 0.31 g/l glucose, 0.91 g/l arabinose, 0.2 g/l lactic acid, 2.39 g/l acetic acid, 0.31 g/l formic acid, and other minor products. The first step in this process is an acid-catalyzed biphasic dehydration to produce furfural in yields up to 87%. The furfural is extracted from the aqueous solution into a tetrahydrofuran (THF) phase which is then fed into an aldol condensation step. The furfural-acetone-furfural (F-Ac-F) dimer is produced in this step by reaction of furfural with acetone in yields up to 96% for the F-Ac-F dimer. The F-Ac-F dimer is then subject to a low-temperature hydrogenation to form the hydrogenated dimer (H-FAF) at 110-130 • C and 800 psig with a 5 wt% Ru/C catalyst. Finally the H-FAF undergoes hydrodeoxygenation to make jet and diesel fuel range alkanes, primarily C 13 and C 12 , in yields up to 91%. The theoretical yield for this process is 0.61 kg of alkane per kg of dry xylose derived from the hemicellulose extract. Experimentally we were able to obtain 76% of the theoretical yield for the overall process. We estimate that jet and diesel fuel range alkanes can be produced from between $2.06/gal to $4.39/gal depending on the feed xylose concentration, the size of the biorefinery, and the overall yield. Sensitivity analysis shows that the prices of raw materials, the organic-to-aqueous mass ratio in the biphasic dehydration, and the feed xylose concentration in the hemicellulose extract significantly affect the product cost.
A simulation procedure for predicting the dynamic behavior of a deep bed filter over the entire practicable range of filter operation is developed. The method is based on synthesizing available quantitative results relating to filtration, and to porous media flows, within an overall framework which views the process to consist of two principal stages dominated by appropriate limiting deposition modes. Evaluation of the results through comparison with available data indicates, to the extent the nature of these types of data permits, that the method is surprisingly effective and even capable of predicting on satisfactorily quantitative basis some intricate details of observed filter behavior. CHI SCOPEThis work is concerned with the development of a simulation procedure capable of predicting the dynamic behavior of a deep bed filter over the broadest practicable range of the pertinent variables involved, including, in particular, the value of the specific deposit. The method presented here was developed by assimilating available quantitative results relating to porous media flows, and to filtration, in the context of a conceptual framework which views the process, and its progressive evolution, to consist of two consecutive stages, each dominated by an appropriate limiting deposition mode. This picture of the process is supportable on the basis of observed filter behavior and does, moreover, provide the means for integrating results based on the two main collector types (the spherical and the constricted tube models) into the overall simulation scheme. The method we present incorporates the transformation, first suggested by Herzig et al. (1970), which reduces the governing conservation equations into a set of ordinary differential equations, thereby leading to considerable savings in computational effort. CONCLUSIONS AND SIGNIFICANCEDeep bed filtration is a subject which has, in recent years, developed a rich and varied literature. Despite the dramatic progress in our understanding which this has produced, a comprehensive method capable of predicting the dynamic behavior of a filter over its entire operational span has remained out of reach. No doubt the uncertainties surrounding some aspects of the nature of the deposition process, particularly the critical ones relating to the nature of the distribution of the deposited matter within the media and its evolution with progressive deposition, have stood as the main impediments obstructing progress towards such a general predictive scheme. In this work this problem is resolved by postulating an overall picture of the filtration process which views it to consist of two consecutive stages: a first stage dominated by deposition according to a smooth coating mode and assumed to endure until the specific deposit attains a prescribed transition value, followed by a second stage corresponding to transition to deposition by the constriction clogging mode. This picture of the process, though somewhat idealized, is in the main consistent with observed filter behavior.However...
Subjecting charged colloidal particles to a compressional sound wave gives rise to a periodic polarization of the ionic atmosphere surrounding the particles. This periodic polarization causes each particle to act as a vibrating dipole resulting in an alternating voltage, termed the colloid vibration potential (CVP), between any two points in space separated by a phase distance other than an integral multiple of the wavelength and normal to the propagation direction. The present work shows that the CVP is analogous in many respects to the Dorn effect (sedimentation potential) and reflects the same intrinsic phenomena where double-layer relaxation is the dominant process. Both Smoluchowski's theory of the Dorn effect and Enderby's treatment of a charged particle in a sound field are reviewed. Expressions are presented showing the relationship of the CVP to the f potential for dilute colloids. It is also shown how the theory can be extended to particle concentrations as high as 50% by volume using the Levine et al. cell model theory. An apparatus for making electrokinetic measurements using continuous wave ultrasonics is described in detail Data are presented comparing mobilities obtained from CVP measurements and microelectrophoresis. Data are also shown for the dependence of the CVP on particle concentration and compared to predictions based on the proposed modifications using the cell model theory. Also included are data showing the versatility and advantages of acoustical electroki * Author to whom all correspondence should be addressed.
A general correlation for the prediction of the initial collection efficiency of HEMANT PENDSE and CHI TlEN granular filter beds is proposed. The correlation is based on the results obtained from trajectory calculation and the comparison between the numerical results and available experimental data. The correlation includes all the pertinent dimensionless groups and agrees with reported data within experimental accuracy.The performance of a filter can be described by its overall collection efficiency, E, defined as where tin and c,ff are the particle concentrations of the influent and effluent streams respectively.Although the overall collection efficiency, E, provides a direct indication of particulate removal capability, it is not a fundamental quantity which can be readily correlated with operating variables.
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