Evaporation/condensation reactors

Evaporation/condensation reactors involve evaporating a solid, such as a metal, and then mixing it with a cool gas to induce condensation as an aerosol of metal particles. 

Most of the terephthalic acid is produced with a catalyst system developed by Scientific Design. It was purchased by Amoco and Mitsui and is referred to as the Amoco Oxidation. The solvent is acetic acid. Compressed air is used as the source for oxygen. The catalyst dissolved in acetic acid and the two reactants are continuously fed into the reactor. The temperature is around 200 °C and the pressure is approximately 25 bar. The reaction is very exothermic (1280 klrnoT1, calculation from data in Stull et al [16] often a much higher, erroneous value is cited). This heat of reaction is removed by evaporation/condensation of acetic acid and can be used in the solvent distillation/purification part of the plant. A scrubber washes the vent gases... 

Nuclear reactors Flash evaporators Condensers Distillation columns Absorption columns... 

Vaporizer and condenser pressures Distillation pressures Distillation reflux ratios Evaporator pressures Number of evaporator stages Reactor conversion Recycle flowrates... 

Aerosol Reactors Commercial and Pilot Scale 332 Flame Reactors 332 Pyrolysis Reactors 334 Electron-Beam Dry Scrithhirif 335 Evaporation-Condensation Generators 336 The Collision-Coalescence Mechanism of Primary Particle Formation 338... 

Major industrial uses of tantalum include the production of electrical components (mainly capacitors), superalloys, tantalum carbide, and in the chemical industry (Cunningham 2000). Its physical properties make tantalum an important component of superalloys (produced by combination with cobalt, iron, nickel, and titanium) commonly used in the aerospace industry. In the chemical industry, tantalum s corrosion resistance is taken advantage of in the production of heat exchangers, evaporators, condensers, pumps, and liners for reactors and tanks (Cunningham 2000). The recycling of industrial and obsolete tantalum-containing scrap represents approximately 20% of the total tantalum consumption in the US (Cunningham 2000). 

Reactions do not necessarily proceed uniformly, and uneven rates of reaction can lead to poor product quality and increased byproducts. Some intensified reactor types overcome the lack of uniformity of performance by careful design, but larger reactor vessels are inhwently non-isothermal. This can be overcome by attempting to move heat from those most exothermic parts of the reaction to areas where the reaction is less fast. The heat pipe (see Chapter 11) is a passive heat transfer device that can be used to implanent this in a reactor. Sometimes called a super thermal conductor , the heat pipe uses an evaporation-condensation cycle to transfer heat over a distance with minimal temperature drop. The fluid in the pipe is selected to suit the reactor operating temperature liquid metals may be used for high temperature reactions (at 600 C to 1000 C plus), for instance. 

EVAPORATOR HEATER REACTOR COOLER COOLERS CONDENSER... 

The UCB collection and refining technology (owned by BP Chemicals (122,153—155)) also depends on partial condensation of maleic anhydride and scmbbing with water to recover the maleic anhydride present in the reaction off-gas. The UCB process departs significantly from the Scientific Design process when the maleic acid is dehydrated to maleic anhydride. In the UCB process the water in the maleic acid solution is evaporated to concentrate the acid solution. The concentrated acid solution and condensed cmde maleic anhydride is converted to maleic anhydride by a thermal process in a specially designed reactor. The resulting cmde maleic anhydride is then purified by distillation. 

The low molar ratio of the final UF-resin is adjusted by the addition of the so-called second urea, which might also be added in several steps [16-18]. Particular care and know-how are needed during this acid condensation step in order to produce resins of good performance, especially at the very low molar ratios usually in use today in the production of particleboard and MDF. This last reaction step generally also includes the vacuum distillation of the resin solution to the usual 63-66% solid content syrup in which form the resin is delivered. The distillation is performed in the manufacturing reactor itself or in a thin layer evaporator. Industrial preparation procedures are usually proprietary and are described in the literature in only a few cases [17-19]. 

Most condensation polymers have negligible heats of reaction. See Table 13.2. Heat must be supplied to evaporate by-products such as water or ethylene glycol. An external heat exchanger is the best method for heating large reactors. Flashing the recycle stream as it enters the vessel also aids in devolatilization. 

Condensed mode operation. To avoid accumulation of liquid in the reactor the dew point of the gas must be kept above reactor temperature. When operating in condensed mode, higher-boiling components in the recirculating gas are allowed to condense in the heat exchanger, and this liquid is fed back to the reactor where it evaporates. 

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