Cooling isothermal

Reformed gas is cooled to the shift inlet temperature of 250°C by generating steam (4). The CO shift reaction takes place in a single stage in the tube-cooled isothermal shift reactor (5), where process steam is generated from condensate. No process condensate effluent from the LAC plant is generated, thus eliminating a condensate treatment system. 

Figure A2.1.11. Magnetic cooling isothermal magnetization at 4 K followed by adiabatic demagnetization to...

Problem 6.1 A flow process produces work using water as the working medium. The process is as follows steam of quality 50% at 1 bar is compressed adiabatically to 20 bar is heated isothermally by absorbing 3500 kJ/kg of heat is expanded adiabatically to an unspecified final pressure and is finally cooled isothermally until the steam returns to its initial state (steam of quality 50% at 1 bar). It is further reported that 53% of the heat added during the heating step is rejected ciuring the cooling step. What is your evaluation of this process ... 

An ideal gas is cooled isothermally (at constant temperature). The internal energy of an ideal gas remains constant during an isothermal change. If is —76 J, what are At/ and w ... 

Tube-cooled isothermal Catalyst loaded into or around tubes. Temperature rise controlled by suitable cooling medium not perfectly isothermal. 

Isothermal polymerizations are carried out in thin films so that heat removal is efficient. In a typical isothermal polymerization, aqueous acrylamide is sparged with nitrogen for 1 h at 25°C and EDTA (C2QH2 N20g) is then added to complex the copper inhibitor. Polymerization can then be initiated as above with the ammonium persulfate—sodium bisulfite redox couple. The batch temperature is allowed to rise slowly to 40°C and is then cooled to maintain the temperature at 40°C. The polymerization is complete after several hours, at which time additional sodium bisulfite is added to reduce residual acrylamide. 

Heat Transfer. One of the reasons fluidized beds have wide appHcation is the excellent heat-transfer characteristics. Particles entering a fluidized bed rapidly reach the bed temperature, and particles within the bed are isothermal in almost all commercial situations. Gas entering the bed reaches the bed temperature quickly. In addition, heat transfer to surfaces for heating and cooling is excellent. 

Heat pipes are used to perform several important heat-transfer roles ia the chemical and closely aUied iadustries. Examples iaclude heat recovery, the isothermaliziag of processes, and spot cooling ia the mol ding of plastics. In its simplest form the heat pipe possesses the property of extremely high thermal conductance, often several hundred times that of metals. As a result, the heat pipe can produce nearly isothermal conditions making an almost ideal heat-transfer element. In another form the heat pipe can provide positive, rapid, and precise control of temperature under conditions that vary with respect to time. 

Stmctures that form as a function of temperature and time on cooling for a steel of a given composition are usually represented graphically by continuous-cooling and isothermal-transformation diagrams. Another constituent that sometimes forms at temperatures below that for peadite is bainite, which consists of ferrite and Fe C, but in a less well-defined arrangement than peadite. There is not sufficient temperature and time for carbon atoms to diffuse long distances, and a rather poody defined acicular or feathery stmcture results. 

In a typical isothermal process, 70% hydrogen peroxide is added to 98% sulfuric acid, and subjected to rapid stirring and efficient cooling, so that the temperature does not rise to above 15°C. If equimolar quantities of reactants are used, the product contains 42% H2SO and 10% H2O2. Although the reaction may seem simple, many of its features are critically important and it should only be attempted foUowiag advice from speciaUsts. 

Maintenance of isothermal conditions requires special care. Temperature differences should be minimised and heat-transfer coefficients and surface areas maximized. Electric heaters, steam jackets, or molten salt baths are often used for such purposes. Separate heating or cooling circuits and controls are used with inlet and oudet lines to minimize end effects. Pressure or thermal transients can result in longer Hved transients in the individual catalyst pellets, because concentration and temperature gradients within catalyst pores adjust slowly. 

Based on differences in melting points and Hquid-phase solubilities four modes of operation possible drown-out, isothermal evaporation, adiabatic evaporation, and cooling (choice depends on stream characteristics). 

Order of preference adiabatic evaporation > isothermal evaporation > cooling >drown-out. 

In austempering the article is quenched to the desired temperature in the lower bainite region, usually in molten salt, and kept at this temperature until transformation is complete (Fig. 22). Usually, the piece is held twice as long as the period indicated by the isothermal transformation diagram. The article may then be quenched or air-cooled to room temperature after transformation is complete, and may be tempered to lower hardness if desired. 

The Snamprogetti process utilizes a tubular isothermal reactor (tubes filled with catalyst) for the first reactor with cooling water on the shell side to control temperature. The Huls process uses either an adiabatic or isothermal reactor for the first reactor. 

For practical reasons, the blast furnace hearth is divided into two principal zones the bottom and the sidewalls. Each of these zones exhibits unique problems and wear mechanisms. The largest refractory mass is contained within the hearth bottom. The outside diameters of these bottoms can exceed 16 or 17 m and their depth is dependent on whether underhearth cooling is utilized. When cooling is not employed, this refractory depth usually is determined by mathematical models these predict a stabilization isotherm location which defines the limit of dissolution of the carbon by iron. Often, this depth exceeds 3 m of carbon. However, because the stabilization isotherm location is also a function of furnace diameter, often times thermal equiHbrium caimot be achieved without some form of underhearth cooling. 

Cooling-in-Tank or Jacketed Vessel Isothermal Cooling Medium... 

Tanks cool, contents partially freeze, and solids drop to bottom or rise to top. This case requires a two-step calculation. The first step is handled as in case 1. The second step is calculated by assuming an isothermal system at the freezing point. It is possible, given time and a sufficiently low ambient temperature, for tank contents to freeze solid. 

To reduce the work of compression in this cycle a two-stage or dualpressure process may be usedwhereby the pressure is reduced by two successive isenthalpic expansions. Since the isothermal work of compression is approximately proportional to the logarithm of the pressure ratio, and the Joule-Tnomson cooling is roughly proportional to... 

Ammonia (aqueous) [7664-41-7] M 17.0 + H2O, d 0.90 (satd, 27% w/v, 14.3 N), pK 9.25. Obtained metal-free by saturating distilled water, in a cooling bath, with ammonia (from tank) gas. Alternatively, can use isothermal distn by placing a dish of cone aq ammonia and a dish of pure water in an empty desiccator and leaving for several days. AMMONIA (gas, liquid or aq soln) is very irritating and should not be inhaled in large volumes as it can lead to olfactory paralysis (temporary and partially permanent). 

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