Reactor evaporative

Perhaps the additional capacity might not be needed. If it is not needed then the size of the reactors, evaporator and stripper can be reduced. Keeping the original process capacity with parallel operation of the reactors would mean a tradeoff between the increased capital cost of two (smaller) reactors versus reduced capital cost of the evaporator and stripper. An economic comparison would be required to judge whether this would be beneficial. 

The full-scale reactor/evaporator had a total size of 7.6 cm x 10.2 cm x 5.1 cm and was composed of four monoliths of 5 cm2 cross-sectional area and four heat exchangers with 7.2 cm3 cross-sectional area. This device was claimed to evaporate... 

A schematic diagram of a prill tower is given in Fig. 7.7. Some details of an installation for fertilizer materials are listed in Table 1.2. Melt is provided to the prilling devices at the top of the tower from reactor/evaporator systems in the case of a fertilizer material such as ammonium nitrate or from a melt tank in the case of fusible materials such as petroleum wax and coal tar pitch. Melt droplets travel counter-current to cooling air and the solid prills are conveyed away from the bottom of the tower to appropriate downstream treatments such as cooling, clay treatment and storage. 

Heat transfer is an important consideration when the fluid motion in the vessel is in the laminar flow regime. It influences the design and operation of agitated process vessels such as reactors, evaporators, and crystallizers. For a review of working relationships, see Dream [76]. 

Figure 4.10 Scheme of the reactor/evaporator employed in the continuous-flow AQ preparation from BBA in the presence of hydrate H7PW12O42 catalyst. (From lesser, R., Di Serio, M., Ambrosio, M., and Santacesaria, Chem. Eng.., 90,195,2002. With permission.)... 

This chapter deals with equipment types that are of most interest to a process engineer tubular and plate exchangers condensers boilers and calandrias extended surface equipment mechanically aided heat-transfer devices and tubular chemical reactors. Evaporators are described in Chap. 16. Information on all types of heat-exchange equipment is given in engineering texts and handbooks.i -= °... 

Boilers are operated in many industries for generating steam required for process heating of reactors, evaporators, and distillation columns which may need steam at a pressure of 4-6 kg/cm only. However, the boilers are generally operated at 10-15 kg/cm or even higher pressures. Steam is also available from waste heat recovery boilers in many chemical industries at such pressures. 

The heat-storage and heat-release reactions occur at different pressure levels. The low-temperature side has a higher reaction equilibrium pressure. The CHP, as studied earlier, operates as a batch system with a heat-storing step followed by a heat-releasing step. For example, hydration and carbonation reactions can be used on the high-temperature (600 to 1200 K) side reactor. Evaporation and condensation of the reactant media are often used on the low-temperature (273 to 523 K) side reactor. 

A recent technology improvement, based on the concept of reactor-evaporator, affords higher productivities in the industrial production of DMC, making it easier to scale up to large capacity plants. 

Structural designs with safety margins and overload considerations should be done on basis of all equipment (reactors, evaporators) provided with all fittings and mountings in completely filled up condition, and with the agitators mnning at fiill speed. This gives an indication of vibratoiy load. Consider wind loads and loads due... 

As depicted in Scheme 2.4, the concept of the reactor-evaporator is adopted the catalyst is kept inside the reactor, from which the products are vaporized, largely taking advantage of the heat of reaction (AH = —74 kcal mol ), and are removed from the reaction system together with the excess gas leaving the reactor [120]. 

Figure 10-4 shows how the refrigerant system was changed. The reactor (evaporator) was revamped from stagnant boiling in the tubes to forced... 

These are processes or sections of processes, which can be assumed to be ideally mixed and consequently all state variables are only dependent on time and are independent of a certain location. Examples of these processes are ideally mixed reactors, evaporators and one-stage separators. These processes can be described by a combination of elementary balances ... 

The urea produced is normally either prilled or granulated. In some countries there is a market for Hquid urea—ammonium nitrate solutions (32% N). In this case, a partial-recycle stripping process is the best and cheapest system. The unconverted NH coming from the stripped urea solution and the reactor off-gas is neutralized with nitric acid. The ammonium nitrate solution formed and the urea solution from the stripper bottom are mixed, resulting in a 32—35 wt % solution. This system drastically reduces investment costs as evaporation, finishing (priQ or granulation), and wastewater treatment are not required. 

In the one-stage process (Fig. 2), ethylene, oxygen, and recycle gas are directed to a vertical reactor for contact with the catalyst solution under slight pressure. The water evaporated during the reaction absorbs the heat evolved, and make-up water is fed as necessary to maintain the desired catalyst concentration. The gases are water-scmbbed and the resulting acetaldehyde solution is fed to a distUlation column. The tad-gas from the scmbber is recycled to the reactor. Inert materials are eliminated from the recycle gas in a bleed-stream which flows to an auxdiary reactor for additional ethylene conversion. 

In production, anhydrous formaldehyde is continuously fed to a reactor containing well-agitated inert solvent, especially a hydrocarbon, in which monomer is sparingly soluble. Initiator, especially amine, and chain-transfer agent are also fed to the reactor (5,16,17). The reaction is quite exothermic and polymerisation temperature is maintained below 75°C (typically near 40°C) by evaporation of the solvent. Polymer is not soluble in the solvent and precipitates early in the reaction. 

This procedure may result in a concentration of cumene hydroperoxide of 9—12% in the first reactor, 15—20% in the second, 24—29% in the third, and 32—39% in the fourth. Yields of cumene hydroperoxide may be in the range of 90—95% (18). The total residence time in each reactor is likely to be in the range of 3—6 h. The product is then concentrated by evaporation to 75—85% cumene hydroperoxide. The hydroperoxide is cleaved under acid conditions with agitation in a vessel at 60—100°C. A large number of nonoxidising inorganic acids are usehil for this reaction, eg, sulfur dioxide (19). 

If a linear mbber is used as a feedstock for the mass process (85), the mbber becomes insoluble in the mixture of monomers and SAN polymer which is formed in the reactors, and discrete mbber particles are formed. This is referred to as phase inversion since the continuous phase shifts from mbber to SAN. Grafting of some of the SAN onto the mbber particles occurs as in the emulsion process. Typically, the mass-produced mbber particles are larger (0.5 to 5 llm) than those of emulsion-based ABS (0.1 to 1 llm) and contain much larger internal occlusions of SAN polymer. The reaction recipe can include polymerization initiators, chain-transfer agents, and other additives. Diluents are sometimes used to reduce the viscosity of the monomer and polymer mixture to faciUtate processing at high conversion. The product from the reactor system is devolatilized to remove the unreacted monomers and is then pelletized. Equipment used for devolatilization includes single- and twin-screw extmders, and flash and thin film evaporators. Unreacted monomers are recovered for recycle to the reactors to improve the process yield. 

Fig. 3. Typical nitric acid oxidation process. A, reactor B, optional cleanup reactor C, bleacher D, NO absorber E, concentrating stUl F, crude crystallizer G, centrifuge or filter H, refined crystallizer I, centrifuge or filter , dryer K, purge evaporator L, purge crystallizer M, centrifuge or filter N,...

The reactor effluent, containing 1—2% hydrazine, ammonia, sodium chloride, and water, is preheated and sent to the ammonia recovery system, which consists of two columns. In the first column, ammonia goes overhead under pressure and recycles to the anhydrous ammonia storage tank. In the second column, some water and final traces of ammonia are removed overhead. The bottoms from this column, consisting of water, sodium chloride, and hydrazine, are sent to an evaporating crystallizer where sodium chloride (and the slight excess of sodium hydroxide) is removed from the system as a soHd. Vapors from the crystallizer flow to the hydrate column where water is removed overhead. The bottom stream from this column is close to the hydrazine—water azeotrope composition. Standard materials of constmction may be used for handling chlorine, caustic, and sodium hypochlorite. For all surfaces in contact with hydrazine, however, the preferred material of constmction is 304 L stainless steel. 

Molecular beam epitaxy (MBE) is a radically different growth process which utilizes a very high vacuum growth chamber and sources which are evaporated from controlled ovens (15,16). This technique is well suited to growing thin multilayer stmctures as a result of very low growth rates and the abihty to abmpdy switch source materials in the reactor chamber. The former has impeded the use of MBE for the growth of high volume LEDs. 

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. 

Similar to IFP s Dimersol process, the Alphabutol process uses a Ziegler-Natta type soluble catalyst based on a titanium complex, with triethyl aluminum as a co-catalyst. This soluble catalyst system avoids the isomerization of 1-butene to 2-butene and thus eliminates the need for removing the isomers from the 1-butene. The process is composed of four sections reaction, co-catalyst injection, catalyst removal, and distillation. Reaction takes place at 50—55°C and 2.4—2.8 MPa (350—400 psig) for 5—6 h. The catalyst is continuously fed to the reactor ethylene conversion is about 80—85% per pass with a selectivity to 1-butene of 93%. The catalyst is removed by vaporizing Hquid withdrawn from the reactor in two steps classical exchanger and thin-film evaporator. The purity of the butene produced with this technology is 99.90%. IFP has Hcensed this technology in areas where there is no local supply of 1-butene from other sources, such as Saudi Arabia and the Far East. 

The electrolyte feed to the cells is pretreated to remove impurities, and/or additives are added to the feed to improve cell performance (94). The cell hquor leaving the cell is evaporated, crystallised, and centrifuged to remove soHd sodium perchlorate. The clarified cell Hquor can undergo reaction in a double metathesis reactor to produce NH CIO, KCIO or other desired perchlorates. 

Ammonia, hydrochloric acid, and sodium perchlorate are mixed and the reaction mixture crystallised in a vacuum-cooled crystalliser. Ammonium perchlorate crystals are centrifuged, reslurried, recentrifuged, and then dried and blended for shipment. Mother Hquor is evaporated to precipitate sodium chloride and the depleted mother Hquor is recycled to the reactor. The AP product made by this method is 99% pure and meets the specifications for propeUant-grade ammonium perchlorate. The impurities are ammonium chloride, sodium perchlorate, ammonium chlorate, and water insolubles. 

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