bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorptive Capacity in R&D Joint Ventures When Basic Research Is Costly
Authors: Frascatore Mark R.
Published: March 2007

``Absorptive capacity"  a firm's ability to assimilate information acquired from other firms  can depend on the amount of basic research it conducts. The optimal expenditures on basic research depend on its costs, and these expenditures in turn affect the amount of applied research a firm conducts to lower production costs. This paper shows that firms' expenditures on basic research can differ from the socially optimal levels, and the difference depends on the magnitude of the basic research costs and the amount of research collaboration between the firms. Policy responses that could bring firm behavior in line with that which is socially desirable are discussed as well.
Did the Death of Australian Inheritance Taxes Affect Deaths?
Authors: Gans Joshua S , Leigh Andrew
Published: March 2007

In 1979, Australia abolished federal inheritance taxes. Using daily deaths data, we show that approximately 50 deaths were shifted from the week before the abolition to the week after. This amounts to over half of those who would have been eligible to pay the tax. Although we cannot rule out the possibility that our results are driven by misreporting, our results imply that over the very short run, the death rate may be highly elastic with respect to the inheritance tax rate.
The Catastrophic Harm Precautionary Principle
Authors: Sunstein Cass R.
Published: March 2007

When catastrophic outcomes are possible, it makes sense to take precautions against the worst-case scenarios — the Catastrophic Harm Precautionary Principle. This principle is based on three foundations: an emphasis on people’s occasional failure to appreciate the expected value of truly catastrophic losses; a recognition that political actors may engage in unjustifiable delay when the costs of precautions would be incurred immediately and when the benefits would not be enjoyed until the distant future; and an understanding of the distinction between risk and uncertainty. The normative arguments are illustrated throughout with reference to the problem of climate change; other applications include avian flu, genetic modification of food, protection of endangered species, and terrorism.
Roles of Government in Compensating Disaster Victims
Authors: Sugarman Stephen D
Published: March 2007

First explored are the nature of disasters – societal and individual, natural and manmade – and the place of both tort law and private insurance in providing compensation for disaster victims. Following brief discussions of disaster prevention and the sorts of private and public harms that are caused by disasters, five possible roles of government with respect to individual victim compensation are examined: 1) Facilitating the Receipt of Private Compensation for the Consequences of a Disaster; 2) Assuring Insurance Availability for Disaster Victims When the Market Fails to Do So; 3) Providing Victim Compensation Either When Government Should Have Prevented the Disaster or When It Is the Sort of Disaster We Aspire to Have Government Prevent; 4) Providing Victim Compensation as an Alternative to Tort Recovery; and 5) Providing Victim Assistance to Overwhelmed Communities For Reasons of Altruism and National Solidarity. Finally, brief attention is given to the type and level of victim compensation that government might assure.
Wake of the Flood: Crime, Disaster, and the American Risk Imaginary after Katrina
Authors: Simon Jonathan S
Published: March 2007

When the city of New Orleans was flooded after Hurricane Katrina in August of 2005, coverage of the beleaguered city was soon dominated by horrifying tales of violent crime. These stories, carried in all the major media, and verified by top officials of the City, turned out to be completely false. The major emphasis on violent crime, however, had immediate and dire consequences. Rescuers and victims of the flood lost precious time hunkering down instead of rescuing themselves or others. Escapees from the city faced stigma and sometimes armed resistance to their seeking refuge. Politicians responsible for one of the worst failures of government in American history found crucial political traction by railing against lawlessness. Now a year later, the most significant long term consequences of this “false memory” of criminal violence in the wake of the flood, may be in shaping America’s “risk imaginary.” For a long time American personal and governmental attitudes toward risk were shaped by the work accident as a model of modern risk and insurance as an exemplary tool of risk governance. In recent decades, those models and the images, narratives, and discourses supporting them, have been replaced by ominous images of grave technological disasters and fearsome violent crimes. These new figures haunting our risk imaginary have undercut support for broad measures of social risk spreading and encouraged privatization, isolation, and heavy reliance on police and prisons as tools of government. Now, the false memory of post-Katrina violence may reinforce those tendencies by condensing the disaster and crime fears of recent decades into a memorable and racially coded image of terror.
Terrorism Insurance: Rethinking the Government's Role
Authors: Jaffee Dwight M , Russell Thomas
Published: March 2007

Following a major terrorist attack, private providers of terrorism insurance often cease providing this coverage. As a result, the governments in developed countries around the world now provide some form of support to their terrorism insurance markets. This paper considers several questions regarding the private market failure and the resulting government intervention: Why do private markets for terrorism insurance fail? Given the failure, what is the optimal form of government intervention? And, what would be the likely economic ramifications if a government chose not to intervene? The paper’s discussion of these questions focuses on the 9/11 attacks on the United States, and on the 2002 Terrorism Risk Insurance Act (TRIA) and its 2005 extension (TRIAE). The paper argues that government support for the terrorism insurance market should be priced based on the expected cost of the support provided. The paper also argues that such support should generally be temporary, with a sunset as the private market recovers. A specific proposal is that the government intervention take the form of loans to the affected insurance companies, similar to the manner that central banks provide loans to banks facing temporary liquidity crises.
Risk, Fairness, and the Geography of Disaster
Authors: Verchick Robert R.M.
Published: March 2007

This article examines risk and distributional fairness as they relate the Hurricane Katrina disaster and climate change. To be sure, these catastrophes are different. Katrina was regional, not global, and was fast-acting. Climate change is global, slow-moving and will come in multiple stages in a series of sudden and incremental changes throughout the world. Yet both present challenges for policy makers concerned with managing risk and protecting the most vulnerable members of society. The issues of risk management and social vulnerability are both tied to geography, an additional theme that helps shed light on the interconnection between the Katrina tragedy and climate change.

An overly narrow focus on cost-benefit studies kept the United States from adequately appreciating the destructive force of Gulf hurricanes and the vulnerability of its levees and land-use policies. This same attention to cost-benefit analysis is similarly distorting the threats that global warming now poses. A lack of attention to America's social safety net also insured that the destruction of Hurricane Katrina would place an enormously disproportionate burden on minorities, women, the poor, and other vulnerable groups. Today's predictions of climate disruption envision a similarly disproportionate burden on the world's poor, women, and people of color. Yet without aggressive efforts to strengthen the physical and economic infrastructures of developing countries, particularly those in Africa and southern Asia, the world's weakest (and least culpable) peoples will bear the brunt of global catastrophe.

This article argues that the same ideas now recommended for New Orleans—a more precautionary risk-management approach and a strengthening of the social safety net—are the same prescriptions for the international community as it faces the prospects of global warming. In keeping with the theme of geography, the article includes a series of thought-provoking, full-color maps to suggest that what we see is unavoidably linked to how we see it.
The 2.4% Solution: What Makes a Mandate?
Authors: Weiner Marc D , Pomper Gerald M
Published: March 2007

Despite that the popular vote margin in the 2004 presidential election was only 2.4%, George W. Bush claimed to have "earned political capital" and Republican National Chairman Ken Mehlman characterized the outcome as "a mandate." While it seems from the size of the electoral margin that such claims are overstated, we look "under the hood" of the election to see whether any particular policy issue  such as the war in Iraq, gay marriage, social security privatization, or any of the others  was sufficiently dominant to justify the characterization of the election as a mandate. We find that the election result sources overwhelmingly to predispositions in the voters' minds before the campaign, with pre-existing party identification the most important factor in both aggregate and individual analyses. Retrospective evaluations favored Kerry, and Bush gained little from his conduct of the war on terror. In its net effect, the campaign was largely a wash, although Bush was more favored on individual traits. Among the policy issues of the campaign, only taxation had a measurable effect, providing a small boost to Bush; the vaunted social issues of abortion and gay marriage were statistically insignificant. The election results suggest that the United States has developed a new national party system of stable and very close competition, but without presidential policy mandates.
Forecasting the 2006 National Elections to the U.S. House of Representatives
Authors: Campbell James E.
Published: March 2007

Drawing on several theories of congressional election change, this article presents a forecasting equation for seat change in U.S. House elections. The equation addresses the problem of the over time comparability of seat change when levels of competition at the congressional district level have declined dramatically, a decline that has substantially reduced the magnitude of net partisan seat change in recent decades. The equation is estimated using both on-year and midterm elections since 1944. It indicates that the 2006 midterm will likely be a good year for the Democrats. However, because of reduced levels of competition restricting the number of seats that are effectively "in play," Democratic Party gains are likely to be in the teens. Though Republicans may narrowly retain their control of the House, there is a very real possibility that Democrats will end the six election string of Republican House majorities.
Using the Generic Vote to Forecast the 2006 House and Senate Elections
Authors: Abramowitz Alan
Published: March 2007

This article describes a model for forecasting the outcomes of congressional elections based on national political conditions and candidate behavior. Pre-election Gallup Poll data on the generic vote and presidential approval are used to measure national political conditions and data on open seats and challenger quality are used to measure the behavior of congressional candidates. The model is tested with data on U.S. House elections between 1946 and 2004. A simpler model based only on national political conditions is tested with data on U.S. Senate elections from the same period. The results indicate that Democrats have a good chance to regain control of the House of Representatives in November. Democratic gains are also likely in the Senate but it will be difficult for Democrats to pick up the six seats that they need to take control of the upper chamber because only 15 of the 33 seats up for election in 2006 are currently held by Republicans.
Republicans and Golf, Democrats and Outkast: Or, Party Political Culture from the Top Down
Authors: Bernstein Jonathan , Bromley Rebecca E. , Meyer Krystle T.
Published: March 2007

Do political elite operatives differ by party affiliation? This article explores the extent to which political differences between the parties are reflected in cultural differences among elite party actors. Using interviews of political operatives published in the National Journal's daily newsletter, the Hotline, we look at differences between the parties on political questions such as political heroes and favorite television news show, and more purely cultural questions including favorite magazines and music. The data suggest that differences between the parties do persist on cultural issues, and that Democrats retain more internal differences than Republicans. We conclude by calling for more research into party culture.
Back to the Future: Ongoing Strife among Leftist Intellectuals
Authors: DiSalvo Daniel
Published: March 2007

This essay reviews two books: Todd Gitlin's Intellectuals and the Flag and Eric Lott's The Disappearing Liberal Intellectual. The views of Gitlin and Lott represent a broad and contrasting section of contemporary left-wing opinion. The conflict between them raises deep and unresolved questions about the Left's status in America. The ongoing strife among intellectuals on the left suggests that the Democratic Party has a long way to go before embracing a set of core principles that can unite the party, forge a new coalition, and provide a rationale for governing.
The Midterm: What Political Science Should Ask Now
Authors: Pitney John J.
Published: March 2007

The 2006 midterm has undercut some familiar assertions about contemporary electoral politics. Political analysts seem to have overstated Republican advantages in several areas: voter turnout, campaign finance, congressional apportionment, party unity, and social issues. The GOP's loss is the discipline's gain, as the election raises good questions for scholarly research.
Rocking the House: Competition and Turnout in the 2006 Midterm Election
Authors: McDonald Michael P.
Published: March 2007

Despite a national tide for the Democrats in the 2006 midterms that increased the number of competitive congressional races, national voter turnout rose only slightly. Consistent with previous findings, higher turnout in some states reflected increased competition in statewide races for Governor and U.S. Senate. Unexpected surprises, however, lurked among individual congressional races. Voter turnout in highly partisan and closely contested congressional races frequently exceeded turnout for the Senate or Governor's races, suggesting that partisan control over Congress motivated participation. But because there were few competitive races overall, particularly in the three most populous states, national turnout suffered. The 2006 midterm election does not signal a return to voter apathy as much as reflect an ailing electoral system, which requires reforms to increase the number competitive congressional seats to boost overall turnout.
Frustrated Ambitions: The George W. Bush Presidency and the 2006 Elections
Authors: Schier Steven E
Published: March 2007

The 2006 elections dealt a strong blow to the sizeable political and policy ambitions motivating the George W. Bush presidency. Bush's attempt to entrench a conservative political regime in national politics now faces its greatest peril. In particular, Bush's "political capital" is much reduced by Democratic control of the House and Senate. Bush's assertion of his formal powers will also receive greater challenge by Congress. It is now up to future GOP presidents to achieve Bush's extensive regime ambitions.
A Regional Analysis of the 2006 Midterms
Authors: Klinkner Philip A , Schaller Thomas F
Published: March 2007

For only the sixth time since 1900, control of both the House and Senate switched during a midterm cycle in the 2006 congressional elections. Although the magnitude of the changes was not as great as 1994, the results from 2006 more fully aligned the two parties' control of Congress with their presidential performance in the Electoral College. Democrats now dominate the Northeast in the same way Republicans dominate the South. For the first time in decades, Democrats will govern as a solidly non-Southern party. At the same time, Republicans face the challenge of overcoming the perils of regional over-representation and a drift to the right, as suggested by the recent comeback of Mississippi Senator Trent Lott. In coming cycles, election battles will focus most fiercely on the 20 competitive Midwest and Interior West states.
Big Deal: The 2006 Midterm Elections, the Progressive Project, and the Reagan-Bush Revolution
Authors: Menefee-Libey David
Published: March 2007

Were the 2006 midterm elections a Big Deal or No Big Deal? On the surface, the outcome seems ordinary: a setback for the president's party in his sixth year, and a return to divided government. Taking a longer view, these elections are historically important. Democratic victories interrupted the work of a sustained Republican "revolution" rolling back the bipartisan Progressive project of the 20th Century in regulation, public provision and civil rights.
A Theory of Action in Iraq: The Three State Partition and a "Mirror the Mix" Strategy
Authors: Demchak Chris
Published: March 2007

For the quagmire of Iraq, the three-state solution is a good one right now, and always has been the best choice. To recognize this inevitability, however, requires that the Bush Administration and its critics alike have an enduring and cohesive explanation for the emergence of the violent instability we see in Iraq. This essay suggests, first, a way to combine the basic elements of the three main streams of international relations in order to understand how individuals and groups may come to find violence acceptable and destroy civil society. Second, this theory of action helps explain why the circumstances particular to Iraq dictate a three-state future as the most powerful way to disrupt the underlying circumstances which fuel violence in Iraq.
Imperfect Competition and Strategic Trade Theory: Evidence for International Food and Agricultural Markets
Authors: Reimer Jeffrey J , Stiegert Kyle
Published: March 2007

Strategic trade theory offers a way of conceptualizing and testing for strategic government interventions in imperfectly competitive international markets. This survey critically assesses recent empirical evidence, with a focus on food and agricultural markets. One finding is that while many international markets are characterized by oligopoly, price-cost markups tend to be small, and the potential gains from intervention are modest at best. In turn, empirical work has turned up few examples in which government intervention has been optimal in a strategic trade sense. Nonetheless, governments are found to frequently intervene on behalf of domestic firms and play a major role in shaping the nature of international competition. Suggestions for future research are made.
Contract Selectivity, Food Safety, and Traceability
Authors: Starbird S. Andrew , Amanor-Boadu Vincent
Published: March 2007

Contracts are an increasingly common method for coordinating exchange in the food industry. Contracts often include specifications for product attributes including food safety. One of the goals of explicit safety specifications is to discourage or deter suppliers who would deliver unsafe food. In this article, we use a principal-agent model in the context of adverse selection to examine how contracts that include traceability can be used to select against producers who cannot meet a processor's safety specifications. We find that the motivation to select against unsafe producers depends on the magnitude of the failure costs and the proportion of the failure costs allocated to producers. We also identify the conditions under which the processor selects against unsafe producers regardless of traceability. Our results are important to regulators and negotiators who want to support safe producers and deter unsafe producers.
Proving Anti-Competitive Conduct in the U.S. Courtroom: Economic Issues with the Courts' Opinions in Pickett v. Tyson Fresh Meats, Inc.
Authors: Taylor C. Robert
Published: March 2007

Four articles have been published in this Journal about the historic cattle trial, Pickett v Tyson Fresh Meats, Inc., in which Plaintiff cattlemen alleged that Tyson/IBPthe buyerused captive (contracted) supplies of cattle to manipulate the cash market in violation of the 1921 Packers & Stockyards Act (PSA). The first article gave a Trial's eye view by David Domina who served as co-lead counsel representing Plaintiff cattlemen. Domina's article led to a published comment by Thomas Green who was the lead attorney representing Tyson during the Trial phase of lengthy legal proceedings. Green alleged that Domina's article was "littered with rank speculation and baseless opinion." Domina countered that "proof is not litter, and evidence is not rank speculation" and that Green's commentary was "abusive." The adversarial exchange between Domina and Green was followed by another advocacy article in which William Rosales maintained that Pickett "represents an opportunity for the judiciary to reform the meatpacking industry  (and) awaken the (PSA's) intended power to dethrone the economic kings of the meatpacking industry."After a five week Trial in Federal Court, the Jury found Tyson/IBP guilty on all counts and assessed actual damages of $1.28 billion over 2/1994 -10/2002. Justice for Plaintiff cattlemen was short, as the Trial Judge set aside the Jury's verdicta rare but not unprecedented legal actionand entered summary judgment for Tyson. The Eleventh Appellate Court subsequently sided with the Trial Judge. On March 24, 2006, the United States Supreme Court denied without comment Plaintiff's Petition to rehear the case, thus ending legal activities in Pickett v Tyson and effectively killing similar legal action pending against two other major beef packers, Excel (Cargill) and Swift (ConAgra).This article emphasizes three significant and troubling legal and economic issues from the historic litigation: (1) the Courts' narrow and extreme interpretation of the antitrust rule-of-reason; (2) the Courts' endorsement of a "meeting the competition" defense, and (3) whether the Courts inserted themselves above the Jury as fact-finders in the case, contrary to the 7th Amendment to the U.S. Constitution that establishes the Jury as the only fact-finder in civil litigation.In essence Pickett was filed under the Packers and Stockyards Act, tried under Sherman and Clayton antitrust law, and overturned, in part, under the Robinson-Patman Act.
Measuring the Degree of Retail Competition in U.S. Cheese Markets
Authors: Arnade Carlos , Gopinath Munisamy , Pick Daniel
Published: March 2007

The objective of this article is to measure the degree of competition among retail stores to sell a specific brand of a product. For this purpose, we estimate brand-specific demand equations along with first order conditions from stores' profit maximization. In stores' profit maximization, we account for three sources of conjectural variation: within a store but across brands, across stores for the same brand, and across stores for other brands. Data on U.S. retail store price and sales data on cheese products from ACNielsen Homescan database are used in our empirical analysis. A set of indices representing concentration of purchases across brands within each store and across stores for each brand are used to estimate conjectural elasticities. Results show the existence of price markups suggesting imperfectly competitive behavior in retail cheese markets.
Treatment of Resorcinol and Phenol Bearing Waste Water by Simultaneous Adsorption Biodegradation (SAB): Optimization of Process Parameters
Authors: Mondal Prasenjit , Balomajumder Chandrajit
Published: March 2007

In the present paper the observations on the simultaneous adsorption biodegradation (SAB) of resorcinol and phenol from two separate synthetic wastewater samples have been reported. For SAB, immobilization of Pseudomonas putida MTCC 1194 on granular activated carbon (GAC) has been done. The optimum process parameters like adsorbent dose, particle size of GAC, and pH have been determined experimentally by calculating percentage removal. The optimum process parameters have also been verified by the theoretical model of Weber and Morris (1963). Under the experimental conditions at 28 degrees Celsius the optimum process parameters are noted as adsorbent dose = 10 g/l, GAC particle size = 2- 4 mm and pH = 6.24. The isotherm studies of these processes have been done. Adsorption studies have also been done separately for both the compounds for comparing the efficiency of SAB over adsorption.
Technical Re-Conversion of an MTBE Plant to Produce ETBE
Authors: Martínez Medina Isela Jazmín , Montiel-Maldonado Celestino
Published: March 2007

The technical re-conversion of MTBE process to produce ETBE was studied, using a non-equilibrium model in catalytic distillation with an UNIFAC method at steady state. The simulation was carried out in Aspen Plus, analyzing the possibility of using the actual installations of the MTBE plant as it works, to produce ETBE. The study is focused on the reactive and the catalytic distillation sections, which rule the process behavior. The analysis of azeotrope conditions revealed that the ethanol-to-isobutene molar feed ratio is the main factor affecting the equilibrium, by modifying the separation between the ETBE product and the butylenes in the catalytic column. The indirect effect of increasing the operating pressure in the reaction equilibrium, by changing the phase equilibrium temperatures increasing them also, as well as by modifying the ethanol-isobutene feed ratio at the reactive zones at a higher value, are the variables that limit the equilibrium. Consequently, a high isobutene conversion is attained. Finally, doing a comparison between the two processes, it can be confirmed that the ETBE can be produced in the same installations, obtaining an isobutene conversion of 98 weight % and an ETBE product with an overall composition of 98 weight %.
Esterification of Palmitic Acid with Iso-Propanol in a Catalytic Distillation Column: Modeling and Simulation Studies
Authors: Chin Sim Yee , Mohamed Abdul Rahman , Ahmad Abdul Latif , Bhatia Subhash
Published: March 2007

Fatty acid esters are currently produced in batch processes. The production of fatty acid esters in a catalytic distillation column is a promising alternative to the conventional sequential process. In the present study, a steady state equilibrium model was developed for the production of iso-propyl palmitate in a catalytic distillation column catalyzed by zinc acetate supported on functionalized silica gel. The model incorporated reaction kinetics and vapor-liquid non-idealities into the MESH (Material balance, Equilibrium relationship, Summation equation and Heat balance) equations. The model was solved with the numerical method coupled with the relaxation method. To ensure the applicability and reliability of the proposed model, it was validated by comparing the simulated results of a similar endothermic fatty acid esterification (decanoic acid with methanol) in a catalytic distillation column, with the published simulation results and the pilot plant data from the literature. The model was capable of predicting the performance of a catalytic distillation column for an endothermic fatty acid esterification.To ensure the most effective reactive distillation process for the esterification of palmitic acid with iso-propanol, several key design parameters such as reactant ratio, column pressure, number of equilibrium stages, catalyst weight and reflux ratio were investigated by sensitivity analysis. The results showed that the operation at maximum possible pressure is beneficial for this process due to the endothermicity of the reaction. It was found that the reactant ratio of 1.3-1.7 was sufficient to give high palmitic acid conversion without affecting the iso-propyl palmitate purity. It was observed that low reflux ratios resulted in higher conversion of palmitic acid. However, the number of rectifying and stripping stages was of minor importance for the performance of the overall process. The simulation results could serve as the basis of designing a pilot-scale catalytic distillation unit.
Study and Improvement of the Regeneration of Metallic Oxides Used as Oxygen Carriers for a New Combustion Process
Authors: Roux Sebastien , Bensakhria Ammar , Antonini Gerard
Published: March 2007

A new combustion process called chemical-looping combustion, has been suggested as an energetically efficient method for separation and capture of the carbon dioxide, generated by the combustion of fossil's fuels. This process consists of a reversible combustion, based on successive fuel oxidation via the reduction of metallic oxide followed by its regeneration by air oxidation. The generated products are: the reduced oxygen carrier, which is regenerated in a second reactor by air and recycled, and a flue gas, mainly composed of CO2 and H2O, which could be separated by condensation.In chemical-looping combustion process, it is important that the metallic oxide, used as an oxygen carrier, has a high reactivity with the fuel and good regeneration ability. It should have also good mechanical characteristics, in order to avoid its attrition and agglomeration during the successive cyclic reactions.In this work, the reactivity study of various oxygen carriers was carried out, during ten successive oxidation and reduction cycles, using a thermal gravimetrical analysis apparatus. From the results obtained, two types of oxygen carriers were identified: very reactive oxygen carriers, with a decreasing of their reactivity during the successive cycles of reduction and oxidation, and oxygen carriers with low and constant reactivity during the successive cycles.In order to improve the capacity of regeneration of the reactive oxygen carrier, several mixtures were prepared by adding stable and non-reactive metallic oxide, which acts as binder or doping agent by the mechanical properties of the mixed oxygen carrier improvement.The results obtained showed that, for all mixtures prepared and tested, the addition of binders to the reactive metallic oxides improve their regeneration ability. The best results, concerning the reactivity and the regeneration performances, were obtained with Fe2O3 mixed with CaO, TiO2 or MgO, followed by NiO mixed with CaO or TiO2 and finally CuO mixed with TiO2 or MgO.
Effects of Design and Operating Parameters on Hydrodynamics of Circulating Bubble Columns with Open Channel Gas Separators
Authors: Al-Masry Waheed A
Published: March 2007

Hydrodynamics of two external loop circulating bubble columns with open channel gas separators were investigated experimentally. The effects of three operating parameters and one design parameter on hydrodynamics were investigated experimentally in two external loop circulating bubble columns with open channel gas separators. The operating parameters were superficial gas velocity in the riser, UGR, gas-liquid dispersion property, and efficiency of gas separation, TVR. The design parameter was the scale-up factor of the riser to downcomer cross-sectional area AD/AR. The gas-liquid dispersion property was varied by using various concentrations of additives like antifoam, alcohols, and wettable suspended solids. All experiments were conducted using compressed air and tap water from the university main supply system. Time-dependent hydrodynamics variation related to air-water quality was minimized by using consistent air-water samples in order to satisfy experimental reproducibility. The results show that for any gas-liquid-additive system, there is an optimum volume of the liquid in the gas separator, TVRO, that gives the minimum gas recirculation in the downcomer. At any AD/AR and TVR, the effects of antifoam and suspended solids were found to reduce the gas holdup, while the alcohols were found to increase gas holdup. At TVRO, the efficiency of the gas separator was improved significantly by increasing the scale-up factor, AD/AR. Liquid circulation was increased in the antifoam system, but reduced in the presence of wettable suspended solids. The best design and operating conditions were found at scale-up factor AD/AR=0.5 and volume ratio TVR>20% for all the additives investigated.
Kinetics and Modelling of Bulk and Solution Diallyl Terephthalate Polymerization
Authors: Hace Iztok
Published: March 2007

Free radical polymerization kinetics of diallyl terephthalate (DAT) in solution was investigated with two different peroxide initiators: dicyclohexyl peroxydicarbonate (CHPC) and benzoyl peroxide (BPO) in temperature range from 50°C to 110°C, where ortho-xylene was used as a solvent. Conversion points were measured using Fourier Transform Infrared (FTIR) measurements. Previously developed kinetic model for bulk DAT polymerization, was extended to solution DAT polymerization. The ratio of solvent chain - transfer rate constants to propagation rate constants of the polymerization system were found between 1.25 10-4 to 1.68 10-4 for various reaction conditions. They were obtained using the calculated initial polymerization rates and the number average molecular weight measurements made by GPC. The effect of different solvent fractions and initiator concentrations on the diffusion limitations were investigated. Only two kinetic parameters, kpd0 and ktd0 were obtained by fitting the kinetic model onto measured conversions for various reaction conditions at 0.2, 0.5 and 0.8 solvent fractions. Thus obtained kpd0 and ktd0 kinetic parameters were extrapolated to zero solvent fractions and from obtained values of kinetic parameters the conversion points for bulk DAT polymerization were calculated and compared to measured conversion points.
Synthesis of SiO2 Nanoparticles in RF Plasma Reactors: Effect of Feed Rate and Quench Gas Injection
Authors: Mostajeran Goortani Behnam , Mendoza Norma , Proulx Pierre
Published: March 2007

Nanoparticles of SiO2 have been produced in an inductively coupled thermal plasma reactor. The resulting nanoparticles were characterized based on their morphology and size distribution. Scanning electron microscopy, nitrogen absorption (BET method), laser diffractometry and X-ray diffraction techniques were used to characterize and to measure the equivalent diameter (D(1,0), D(3,2) and D(4,3)) of the resulting nanopowders. The computational fluid dynamics (CFD) software FluentTM 6.1 with the Fine Particle Model (FPMTM) was used to simulate the whole synthesis process. The nanoparticles of SiO2 produced at the exit (filter) and on the reactor wall had primary particles diameter between 10-300 nm while the aggregates were of much larger size, between 1 and 4 micrometers. The simulation predictions were used to gain more insight into the experimental results.
Optimal Control Trajectories for a Batch Polymerisation Reactor
Authors: Ekpo Emmanuel E , Mujtaba Iqbal M
Published: March 2007

This paper focuses on the determination of optimum control trajectories for the operation of a batch polymerisation reactor. Operating policies needed to achieve pre-specified properties in minimum time are obtained. Two models dealing with the polymerisation of styrene using AIBN as initiator in a batch reactor are considered. The first model (Model I), taken from the literature, is derived from the first principles of the polymerisation system while the other (Model II) is more rigorous involving both mass and energy balances to simulate a batch polymerisation reactor operation.A dynamic optimisation problem incorporating Model I is formulated and solved to find the optimal temperature trajectory and initial initiator concentrations that will yield desired levels of monomer conversion and number average molecular weight in minimum time. The total batch time is divided into a finite number of intervals and piecewise constant reactor temperature is assumed in each interval. The reaction temperature and the length of each interval are optimised using Control Vector Parameterisation technique. Significant savings in batch time are obtained when these results are compared with those available in the literature obtained using the Pontryagin's Maximum Principle.Incorporating Model II, a second dynamic optimisation problem is formulated and solved where the coolant flow rates and lengths of the intervals are optimised to minimise the batch time and yield desired levels of monomer conversion and number average chain length. With examples, the results show that although both optimisation problems result in similar product qualities, the optimal operations are significantly different. Batch time is significantly higher for the second optimisation problem. gPROMS modelling software was used to build the process model and perform the dynamic optimisation.
Solid Phase Hydrodynamics of Three-Phase Fluidized Bed Reactors -- A Convective/Dispersive Phenomena
Authors: Lefebvre Sylvain , Chaouki Jamal , Guy Christophe
Published: March 2007

The objective of this work was to investigate the relative contribution of the convective and dispersive mixing mechanisms to the overall solid phase mixing mechanism for three-phase fluidized bed reactors. Noninvasive Radioactive Particle Tracking (RPT) data were obtained at various operating conditions, reactor diameters and particle systems. The structural wake model was updated and consists of three sub-phases: the particle wake and downflow-emulsion phase following the convective mixing mechanism and the vortex-emulsion phase following the dispersive mixing mechanism.The particle velocity mean and STD increased with the superficial liquid and gas velocity as well as the reactor diameter for each particle phase. Therefore, the extent of mixing increased under these operating parameters. The particle phase's holdup and a new Mixing Mechanism Indicator (MMI), however, exhibited a much more complex trend. For the larger reactor (Dc = 0.292 m), the convective mixing mechanism dominated and at low superficial liquid velocity the contribution of the convective mixing mechanism increased with superficial gas velocity. This trend, however, was reversed when the superficial liquid velocity increased. For the smaller reactor (Dc = 0.10 m), the random movement of the solid dominated. Therefore, the extent of mixing and the mixing mechanism did not follow the same trend. The CFD and the mixing model have to follow both those hydrodynamic properties.Relations to estimate mean and STD particle velocity distribution as well as particle phase holdup were developed. Solid in the established region mainly followed the convective mixing mechanism. Random movement of the solid was mostly observed at the top of the bed, but it was also present in the established region and at the bed bottom. The volume of each region depended on the operating conditions, reactor diameter and particle system. Furthermore, the particle wake expulsion frequency range was similar to the wake shedding frequency found in literature. It is, thus, possible to assume that wake shedding was mainly responsible for the solid exchange between particle phases.
A Study of the Heating Section of a Gas Heated Steam Reformer
Authors: Wesenberg Margrete H. , Ströhle Jochen , Svendsen Hallvard F
Published: March 2007

A gas heated steam reformer (GHR) which converts natural gas to synthesis gas for methanol or Fischer-Tropsch purposes has been modelled for steady state conditions. The model is in two dimensions and is made up of a fixed bed reactor model, representing one of the reactor tubes in the GHR, and an annulus model, representing the annular space on the shell side of the GHR where hot, fully converted syngas emits heat to the reactor tube. The annulus model is described and evaluated in this article. This is a plug flow model which involves heat transfer in radial direction caused by radiation and by turbulence. The gas radiation is modelled by the use of the discrete ordinates method and the effect on heat transfer from turbulence is modelled as an effective radial thermal conductivity. Both heat transfer mechanisms vary with the radial position. An additional annulus model, made in the commercial CFD code FLUENT and based on the k-? turbulence model and the discrete ordinates radiation model, is used to estimate effective radial thermal conductivities. These were implemented in the annulus model of the GHR model. The reactor and the annulus models were combined and linked by the wall temperature profile and the heat flux profile on the outer reactor tube wall. The simulation results were used to study the heat flux and temperature profiles along the reactor length and the radial temperature profiles in the annulus.
Reactor Model for the Underground Coal Gasification (UCG) Channel
Authors: Khadse Anil N. , Qayyumi Mohammed , Mahajani Sanjay M. , Aghalayam Preeti
Published: March 2007

Underground Coal Gasification (UCG) is the process of in-situ conversion of coal into combustible products (syngas) which can be used either as fuel or as a chemical feedstock. In this study, the gasification channel is viewed as a one-dimensional packed bed reactor. The packed bed reactor model is solved incorporating chemical reactions and mass transfer effects. A pseudo-transient model is simulated for temperature and composition profiles of the gas and solid phases. The movements of the pyrolysis and the reaction front are obtained. The model results are in qualitative agreement with literature. The effects of various operating parameters are studied in detail. Steam/O2 ratio, inlet O2 and total pressure determine the solid temperature profile and hence the outlet gas composition. The simulations are performed for two sets of kinetics parameters. The solid temperature profile and outlet gas compositions change significantly with a change in kinetics parameters. The main motivation behind this study is to provide a theoretical base for understanding the critical aspects of UCG and to provide a tool which coupled with experiments will help in determining the commercial feasibility of the UCG process.
Analysis of a Membrane Reactor: Influence of Membrane Characteristics and Operating Conditions
Authors: Tanna Nikunj P , Mayadevi S.
Published: March 2007

Modeling of an esterification reaction in a batch pervaporation membrane reactor (PVMR), and an analysis of the PVMR performance under different reaction conditions for different membrane characteristics are presented. Esterification of ethyl alcohol with acetic acid was considered as the model reaction. The PVMR performance for this reaction could be represented by a 2-step series model. The PVMR performance was similar to that of the batch reactor when both the reactors were in the kinetic regime. However, the performance of the PVMR was superior to that of the batch reactor when both were in the intermediate/equilibrium regime of the reaction. In these regions, the PVMR performance was influenced/limited by the membrane flux and selectivity. The analysis showed that the membrane flux affected the PVMR performance in the intermediate region and the membrane selectivity affected the performance in the equilibrium regime. Further, the limitations introduced by a low-flux membrane could be overcome by appropriate selection of the membrane area and that due to poor selectivity could be compensated to a certain extent by adjusting the feed ratio.
Micro-Kinetic Study of Reduction of NO on Pt Group Catalysts
Authors: Mantri Dinesh B , Aghalayam Preeti
Published: March 2007

Catalytic reduction using CO has significant potential for the control of NOx using Pt group catalysts as CO is already present in the exhausts and Pt group catalysts have high durability in the presence of SO2 and H2O. Different reaction mechanisms are given in the literature for this reaction based on NO dissociation, -NCO formation and so on, but the exact reaction mechanism capable of capturing experimentally observed features is as yet unavailable. To determine the kinetics and reaction mechanism, we propose here an elementary reaction mechanism based on NO dissociation applicable to Pt group catalysts and simulated with CHEMKIN 4.0.2 using single and multiple PSR (Perfectly Stirred Reactor) model. The activation energies of the elementary steps are found from the Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) method. Excellent agreement between literature experiments and our simulation results are observed for the NO-CO reaction on Pt and Rh catalysts and for the NO-CO-O2 reaction on Ir catalyst. The effect of temperature on the NO reduction activity is captured well by the model. Additionally the simulations can also point towards importance of particular reactions, selectivity to N2, effects of surface coverage, effects of residence time and catalytic surface area on NO reduction.
Modeling of Pervaporation Reactor for Benzyl Alcohol Acetylation
Authors: Wasewar Kailas L.
Published: March 2007

The pervaporation reactor is, specifically, the new technology for reaction and separation. It is rather difficult to predict the market potential of processes newly introduced on the market. However, in comparing investment costs, environmental aspects of pervaporation systems with those of conventional processes, it can be said that pervaporation reactor will play an important role in the chemical industry for new installations as well as for rehabilitation of existing plants. Techno-economic studies are showing that pervaporation reactors have good market potential. There are many examples where pervaporation reactors can reduce product costs by an important margin. The most common reaction system studied for the application of pervaporation is an esterification reaction between an alcohol and an acid in the presence of a highly acidic catalyst (e.g., concentrated sulfuric acid). In the present paper, modified/improved model for pervaporation reactor for benzyl alcohol acetylation is presented. The parametric sensitivity is studied for the performance of pervaporation reactor. The use of pervaporation coupled to the esterification reaction increases the conversion considerably. The modified model allows the evaluations of the reaction time necessary to achieve a given conversion. The model makes it possible to determine the membrane surface area / operating time ratio for a given conversion. The present model can be extended for the other esterification reactions in pervaporation reactors.
Kinetics of the Hydrogenation of Sunflower Oil over Alumina Supported Palladium Catalyst
Authors: Fernández María B. , Tonetto Gabriela M , Crapiste Guillermo , Damiani Daniel E
Published: March 2007

The present work studies the sunflower oil hydrogenation on supported palladium catalysts, by analyzing the surface kinetics and the mass transfer limitations of products and reactants. Initially, a simplified model was studied. This model took into account only the consecutive hydrogenation of linoleic acid (diene), to reach the production of oleic (monoene) and stearic (saturated) acids. Using the adjusted values of the kinetic constants and the activation energies of the hydrogenation obtained with this model, a new scheme was investigated considering the geometric isomerization reactions (cis-trans). The diene hydrogenation constant was larger than that of the monoene. This fact confirms the higher reaction rate of the diene hydrogenation in comparison with that of the monoene. With respect to the isomerization rates, these have an activation energy superior to that of the monoene hydrogenation, and slightly superior to the diene hydrogenation activation energy. This fact verifies the influence of temperature on the formation of trans-isomers.