Transfer line reactors

If the solid particles can be maintained in the fluidised state without problems of agglomeration or attrition, the fluidised bed reactor Fig. 1.45c is likely to be preferred. For short contact times at high temperatures the dilute phase transfer line reactor (Fig. 3.37[Pg.187]

The Kellogg premess has been successful for its dilute-phase transfer-line reactor in Sasol s South African plant. The void fraction in the reaction zone is more than 95%, and the superficial gas velocity ranges from 3 to 12 m/sec (G2). Careful consideration is thus necessary in applying FCB... 

Slurry approach use if the carbon usage is <180 kg/day. Mix and suspend powdered adsorbent and then filter exit line. Often uses up to three stages of countercurrent contacting. Used for continuous bleaching of edible oils. Batch process is simple, flexible, and easy to change feedstocks. Continuous operation offers better protection against oxidation, provides shorter holdup, and has the potential of heat recovery. Bleach time 25 min. A related topic is transfer line reactor (Section 16.11.6.9). 

Moving bed Use if > 20 L/s. Related topic transfer line reactor, Section 6.7. Fluidized bed Use if slimes or fine particles in feed. Use superficial velocities of 8 to 14 L/m s. Feed contacts bed for 30 min or 0.8 BV/h. Related topics include reactors. Section 6.30, and drying. Section 5.6. 

See transported slurry, transfer line reactors Section 6.7. 

A selective thermionic specific detector (TSD) was developed by Albert (107) but it is more commonly referred to as a nitrogen-phosphorous detector (NPD). It is basically an alkali FID. Figure 13.36 compares the TSD and the microcoulometric detector. More resolution is obtained through the TSD with elimination of the mixing in the transfer line, reactor tube, and titration cell of the... 

While plug flow is an idealization, fluid flow through long pipes, gas flow through packed beds under certain conditions, and some transfer line reactors may be regarded as plug flow systems as a reasonable approximation. 

In this section we shall present a brief description of gas-solid contacting in kilns, moving beds, cyclones, and transfer line reactors. A substantial number of gas-solid reactions are carried out in equipment of this type, such as ironmaking in the blast furnace (moving bed), the manufacture of cement (kilns), and certain direct reduction processes of iron oxide (kilns or moving beds). 

Corrosion of reactors used for functionalization and ia pipes and valves along transferlines for sulfuric acid is a problem that results ia maintenance shutdowns. Sufficient agitation is needed to keep the resia beads fluidized duting sulfonation. As for copolymer kettles, transfer lines should be sufficiently large to allow reasonably rapid transfer of Hquids and resia slurries. 

Hydroxyhydroquinone and pyrogaHol can be used for lining reactors for vinyl chloride suspension polymerization to prevent formation of polymer deposits on the reactor walls (98). Hydroxyhydroquinone and certain of its derivatives are useful as auxiUary developers for silver haUde emulsions in photographic material their action is based on the dye diffusion-transfer process. The transferred picture has good contrast and stain-free highlights (99). 5-Acylhydroxyhydroquinones are useful as stabilizer components for poly(alkylene oxide)s (100). 

Economy of time and resources dictate using the smallest sized faciHty possible to assure that projected larger scale performance is within tolerable levels of risk and uncertainty. Minimum sizes of such laboratory and pilot units often are set by operabiHty factors not directly involving internal reactor features. These include feed and product transfer line diameters, inventory control in feed and product separation systems, and preheat and temperature maintenance requirements. Most of these extraneous factors favor large units. Large industrial plants can be operated with high service factors for years, whereas it is not unusual for pilot units to operate at sustained conditions for only days or even hours. 

Thus the ECCU always operates in complete heat balance at any desired hydrocarbon feed rate and reactor temperature this heat balance is achieved in units such as the one shown in Eigure 1 by varying the catalyst circulation rate. Catalyst flow is controlled by a sHde valve located in the catalyst transfer line from the regenerator to the reactor and in the catalyst return line from the reactor to the regenerator. In some older style units of the Exxon Model IV-type, where catalyst flow is controlled by pressure balance between the reactor and regenerator, the heat-balance control is more often achieved by changing the temperature of the hydrocarbon feed entering the riser. 

In the modern unit design, the main vessel elevations and catalyst transfer lines are typically set to achieve optimum pressure differentials because the process favors high regenerator pressure, to enhance power recovery from the flue gas and coke-burning kinetics, and low reactor pressure to enhance product yields and selectivities. 

Many accidents occur because process materials flow in the wrong direction. Eor example, ethylene oxide and ammonia were reacted to make ethanolamine. Some ammonia flowed from the reactor in the opposite direction, along the ethylene oxide transfer line into the ethylene oxide tank, past several non-return valves and a positive displacement pump. It got past the pump through the relief valve, which discharged into the pump suction line. The ammonia reacted with 30m of ethylene oxide in the tank, which ruptured violently. The released ethylene oxide vapor exploded causing damage and destruction over a wide area [5]. A hazard and operability study might have disclosed the fact that reverse flow could occur. 

Hinkle, R. E. and J. Friedman, Controlling Heat Transfer Systems for Glass-Lined Reactors, Chem. Eng, p. 101, Jan. 30, (1978). 

A low reactor temperature may not fully vaporize the feed unvaporized feed droplets will aggregate to form coke around the feed nozzles on the reactor walls and/or the transfer line. A long residence time in the reactor and transfer line also accelerate coke buildup. 

Minimize heat losses from the reactor plenum and the transfer line. Heat loss will cause condensation of heavy components of the reaction products. Insulate as much of the system as possible when insulating flanges, verify that the studs are adequate for the higher temperature. 

Table I provides an overview of general reactor designs used with PS and HIPS processes on the basis of reactor function. The polymer concentrations characterizing the mass polymerizations are approximate there could be some overlapping of agitator types with solids level beyond that shown in the tcd>le. Polymer concentration limits on HIPS will be lower because of increased viscosity. There are also additional applications. Tubular reactors, for example, in effect, often exist as the transfer lines between reactors and in external circulating loops associated with continuous reactors.

It is well known that during liquefaction there is always some amount of material which appears as insoluble, residual solids (65,71). These materials are composed of mixtures of coal-related minerals, unreacted (or partially reacted) macerals and a diverse range of solids that are formed during processing. Practical experience obtained in liquefaction pilot plant operations has frequently shown that these materials are not completely eluted out of reaction vessels. Thus, there is a net accumulation of solids within vessels and fluid transfer lines in the form of agglomerated masses and wall deposits. These materials are often referred to as reactor solids. It is important to understand the phenomena involved in reactor solids retention for several reasons. Firstly, they can be detrimental to the successful operation of a plant because extensive accumulation can lead to reduced conversion, enhanced abrasion rates, poor heat transfer and, in severe cases, reactor plugging. Secondly, some retention of minerals, especially pyrrhotites, may be desirable because of their potential catalytic activity. 

Ethylmagnesium bromide was prepared as usual on a large scale in one reactor, and then transferred by nitrogen pressimsation to another. The glass transfer line had not been completely dried the ethane evolved on contact of the Grignard reagent with moisture overpressurised the line and it burst. 

The unconverted reactants and the reaction products leaving the reactor were sent first to a hot vessel heated at 110°C for the collection of the waxes, followed by a second cold vessel cooled at 0°C for the separation of liquid aqueous and organic products. All the transfer lines between the reactor and the hot trap were kept at 150°C to prevent the solidification of the waxes and the condensation of gasoline and diesel range hydrocarbon products outside of the proper traps. 

In some applications, additional components acting as reactors for specific chemical pretreatment are incorporated within the flow manifold. Typical examples are ion-exchange microcolumns for preconcentration of the analyte or removal of interferences and redox reactors, which are used either to convert the analyte into a more suitable oxidation state or to produce online an unstable reagent. Typical examples of online pretreatment are given in Table 2. Apart from these sophisticated reactors, a simple and frequently used reactor is a delay coil (see also Fig. 4), which may be formed by knitting a segment of the transfer line. This coil allows slow CL reactions to proceed extensively and enter into the flow cell at the time required for maximum radiation. The position of the reactors within the manifold is either before or after the injection port depending on the application. 

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