Thermic fluids

Working of all utilities such as air-drying plant, thermic fluid heating systems, packaged steam boilers, diesel generator sets for emergency power supply,... 

Use higher pressure/temperature steam or a heat transfer oil (thermic fluid) at higher temperature for heating provided the jacket and the reactor shell are able to withstand these conditions. Check suitability of high temperature for the reaction mass inside before hand. 

Temperature to be achieved in the process vessel. It may be noted that the thermic fluid will have to be at a temperature at least 20-30 °C above the required temperature for maintaining a reasonable driving force for the transfer of heat. (The heat transfer coefficient is lower than in the case of condensing steam since the heat is transferred from the liquid oil only.) Vapour pressures of thermic oils are on the higher side beyond 200 °C and this must be looked into carefiilly while heating the oil. 

MOC, wall thickness and diameter of coils/pipe used for thermic fluid. Only seamless pipes with tested quality for high-temperature and high-pressure service should be used. Test certificate for the pipes must be available. 

Instrumentation and control for thermic fluid temperature, air blower pressure, firing temperature of heating unit, flame stability, etc. must be included in the scope of supply of the vendor. Audiovisual alarms (hooter/sirenAvaming lamps) should be provided for drawing the operator s attention. 

The innovative process using liquid SO2 and liquid SO3 avoids elaborate chain of glasslined reactors with thermic fluid heating and vacuum distillation batch systems in Fig. 8.2. 

Figure 2. Stationary concentration (reactant) and temperature profiles inside and around a porous catalyst pellet during an exo thermic, heterogeneous catalytic fluid-solid reaction (a) without transport influence, (b) limited only by intraparticle diffusion, (0 limited by lntcrphase and intraparticle diffusion, (d) limited only by interphase diffusion (dense pellet)...

In industrial operation it is necessary, for economic reasons, to recover as much as possible the heat produced by exothermic reactions. One obvious way of doing this, mentioned earlier in Section 11.3, is to preheat the feed by means of the reacting fluid and/or the effluent. When the heat of reaction is sufficient to raise the temperature of the feed to such a value that the desired conversion is realized in the reactor without further addition of heat, the operation is called auto-thermic. Some of the most important industrial reactions like ammonia and methanol synthesis, SO2 oxidation, and phthalic anhydride synthesis, the water gas shift reaction can be carried out in an autothermic way. Coupling the reactor with a heat exchanger for the feed and the reacting fluid or the effluent leads to some special features that require detailed discussion. 

Chemical reactions in supercritical fluids (SCF) have been extensively studied during the past 30 years. Although many of these studies have been performed on a small scale (<60 mL), recent developments tend to attain the liter scale in order to gain engineering as well as chemical and physical information. To carry out chemical reactions on an industrial scale requires a detailed and comprehensive understanding of the energetics of exothermic reactions. The development of an intrinsically safe process requires data on kinetics, physicochemical properties, thermicity, and safety aspects [1],... 

This chapter will concentrate on monitoring techniques applied to polymerization reactions in supercritical fluids. Different available techniques will be discussed, ending with the coupling of analytical and calorimetric measurements. This kind of coupling could be one solution to the problem of simultaneous evaluation of physicochemical properties, kinetic data, and engineering information such as heat transfer and thermicity. 

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