Industrial equilibria

This law was first stated, in a more complex form, in 1884 by Henri Le CMtelier (1850-1936), a French chemist who had studied a variety of industrial equilibria, including those involved in the production of iron in the blast furnace. The statement is commonly referred to as Le Ch telier s principle. 

Cracking experiments have been performed using the microriser, an industrial equilibrium catalyst, and a commercially available hydrowax feedstock. This feedstock was selected for its low aromatics content, low Conradson Carbon Residue (CCR), and very low sulfur or metal concentrations. The characteristics of the feedstock are given in table 2. 

McGuire, T.W. and R. Staelin, An Industry Equilibrium Analysis Of Downstream Vertical Integration, Marketing Science, 2,2 (1983), 161-191. 

As stated earlier, two-phase liquid-vapor equilibrium is the predominant problem in industrial equilibrium calculations. To incorporate equations of state, Eq. (1) is often expanded and rewritten as ... 

An understanding of equilibrium is important in the chemical industry. Equilibrium reactions are involved in some of the stages in the large-scale production of ammonia, sulfuric acid and many other chemicals. 

G.M. Grossman, and E. Helpman. Integration versus Outsourcing in industry equilibrium. The Quarterly Journal of Economics 117 (1), 2002, 85-120. 

A catalyst is a material that accelerates a reaction rate towards thennodynamic equilibrium conversion without itself being consumed in the reaction. Reactions occur on catalysts at particular sites, called active sites , which may have different electronic and geometric structures than neighbouring sites. Catalytic reactions are at the heart of many chemical industries, and account for a large fraction of worldwide chemical production. Research into fiindamental aspects of catalytic reactions has a strong economic motivating factor a better understanding of the catalytic process... 

Most chemically reacting systems tliat we encounter are not tliennodynamically controlled since reactions are often carried out under non-equilibrium conditions where flows of matter or energy prevent tire system from relaxing to equilibrium. Almost all biochemical reactions in living systems are of tliis type as are industrial processes carried out in open chemical reactors. In addition, tire transient dynamics of closed systems may occur on long time scales and resemble tire sustained behaviour of systems in non-equilibrium conditions. A reacting system may behave in unusual ways tliere may be more tlian one stable steady state, tire system may oscillate, sometimes witli a complicated pattern of oscillations, or even show chaotic variations of chemical concentrations. 

Although the left to right reaction is exothermic, hence giving a better equilibrium yield of sulphur trioxide at low temperatures, the reaction is carried out industrially at about 670-720 K. Furthermore, a better yield would be obtained at high pressure, but extra cost of plant does not apparently justify this. Thus the conditions are based on economic rather than theoretical grounds (cf Haber process). 

K. Lucas, Phase Equilibrium and Fluid Properties in the Chemical Industry, Dechema, Erankfurt, 1980. 

At low-to-moderate pressure ranges typical of most industrial apphcatious, the fundamental composition relationship between the vapor and hquid phases in equilibrium can be expressed as a function of the total... 

It was shown that most effective sorbents for concentration of heavy metals in water were silica-polyalumomethylsiloxane and its modified forms possessing increased capacity and the improved kinetic characteristics (solution equilibrium was attained within 5-10 min. for Pb(II) and Cd(II), 2-3 hours for Cu(II) and Zn(II), respectively). It was established that at joint presence of heavy metals in solutions over interval of concentrations 0,05-0,3 g/dm, possible at industrial accident and terrorist acts, the extraction of heavy metals by organoalumosiloxanes and their fonus modified by Cu(II) in water solutions accounted for 98,6-100 %. 

These two reactions, which have been in industrial use for many decades, have equilibrium constants (Table 4.2) where it can be seen that the equilibrium... 

At the time Meijering published his research, Larry Kaufman was working for his doctorate at MIT with a charismatic steel metallurgist. Professor Morris Cohen, and they undertook some simple equilibrium calculations directed at practical problems of the steel industry. From the end of the 1950s, Kaufman directed his... 

The various types of reaetors employed in the proeessing of fluids in the ehemieal proeess industries (CPI) were reviewed in Chapter 4. Design equations were also derived (Chapters 5 and 6) for ideal reaetors, namely the eontinuous flow stirred tank reaetor (CFSTR), bateh, and plug flow under isothermal and non-isothermal eonditions, whieh established equilibrium eonversions for reversible reaetions and optimum temperature progressions of industrial reaetions. 

Chemical reactions obey the rules of chemical kinetics (see Chapter 2) and chemical thermodynamics, if they occur slowly and do not exhibit a significant heat of reaction in the homogeneous system (microkinetics). Thermodynamics, as reviewed in Chapter 3, has an essential role in the scale-up of reactors. It shows the form that rate equations must take in the limiting case where a reaction has attained equilibrium. Consistency is required thermodynamically before a rate equation achieves success over tlie entire range of conversion. Generally, chemical reactions do not depend on the theory of similarity rules. However, most industrial reactions occur under heterogeneous systems (e.g., liquid/solid, gas/solid, liquid/gas, and liquid/liquid), thereby generating enormous heat of reaction. Therefore, mass and heat transfer processes (macrokinetics) that are scale-dependent often accompany the chemical reaction. The path of such chemical reactions will be... 

Many equilibrium calculations are accomplished using tlie plrase equilibrium constant K,. Tliis constant has been referred to in industry as a coiiiponential split factor, since it provides the ratio of the mole fractions of a component in two equilibrium pluises. The defining equation is... 

By contrast with the elusive though isolable HOF, the history of HOCl goes back over two centuries to the earliest experiments of C. W. Scheele with CI2 in 1774 (p. 792), and the bleaching and sterilizing action of hypochlorites have long been used both industrially and domestically. HOCl, HOBr and HOI are all highly reactive, relatively unstable compounds that are known primarily in aqueous solutions. The most convenient preparation of such solutions is by perturbing the hydrolytic disproportionation equilibrium (p. 856) ... 

The production of ammonia is of historical interest because it represents the first important application of thermodynamics to an industrial process. Considering the synthesis reaction of ammonia from its elements, the calculated reaction heat (AH) and free energy change (AG) at room temperature are approximately -46 and -16.5 KJ/mol, respectively. Although the calculated equilibrium constant = 3.6 X 108 at room temperature is substantially high, no reaction occurs under these conditions, and the rate is practically zero. The ammonia synthesis reaction could be represented as follows ... 

Rainfall, besides wetting the metal surface, can be beneficial in leaching otherwise deleterious soluble species and this can result in marked decreases in corrosion rate . A recent survey of rainfall analyses for Europe has shown that, with the exception of the UK, the acidity and sulphate content of rainfall markedly increased in the period 1956 to 1966, pH values having fallen by 0 05 to 0-10 units per ann. The exception of the UK may be due to anti-pollution measures introduced in this period. However, even in the UK a pH of 4 is not uncommon for rainfall in industrial areas. The significance of electrolyte solution pH will be discussed in the context of corrosion mechanisms. The remaining cases of electrolyte formation are those in which it exists in equilibrium with air at a relative humidity below 100%. 

The obvious method of reducing corrosion in fused salts is to choose a system in which either the metal can come to equilibrium with the melt, or else truly protective passivity can be attained. In most cases in industry neither of these alternatives is used. In fact, fused salt baths are usually operated in air atmosphere, and the problem is the prevention of excessive corrosion. This can be done in two ways, (a) by reducing rates of ingress of oxidising species (mainly O2 and H2O) from the atmosphere, and rates of their diffusion in the melts, and (b) by keeping the oxidising power (redox potential) of the melt low by making periodic additions to the bath. 

Can we predict the optimum conditions for a high yield of NH3 Should the system be allowed to attain equilibrium at a low or a high temperature Application of Le Chatelier s Principle suggests that the lower the temperature the more the equilibrium state will favor the production of NHS. Should we use a low or a high pressure The production of NH3 represents a decrease in total moles present from 4 to 2. Again Le Chatelier s Principle suggests use of pressure to increase concentration. But what about practicality At low temperatures reaction rates are slow. Therefore a compromise is necessary. Low temperature is required for a desirable equilibrium state and high temperature is necessary for a satisfactory rate. The compromise used industrially involves an intermediate temperature around 500°C and even then the success of the... 

For some industrial operations an antimony electrode is used to measure hydrogen-ion concentrations. The electrode consists of a rod of antimony which invariably has a coating of oxide, and placed in an aqueous solution the equilibrium... 

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