Reactor walls

In this accident, the steam was isolated from the reactor containing the unfinished batch and the agitator was switched ofiF. The steam used to heat the reactor was the exhaust from a steam turbine at 190 C but which rose to about 300°C when the plant was shutdown. The reactor walls below the liquid level fell to the same temperature as the liquid, around 160°C. The reactor walls above the liquid level remained hotter because of the high-temperature steam at shutdown (but now isolated). Heat then passed by conduction and radiation from the walls to the top layer of the stagnant liquid, which became hot enough for a runaway reaction to start (see Fig. 9.3). Once started in the upper layer, the reaction then propagated throughout the reactor. If the steam had been cooler, say, 180 C, the runaway could not have occurred. ... 

Purely aqueous polymerization systems give copolymers that are not wetted by the reaction medium. The products agglomerate and plug valves, nozzles, and tubing, and adhere to stirrer blades, thermocouples, or reactor walls. These problems do not occur in organic media or mixtures of these with water. 

Ultrafast pyrolysis in the vortex reactor is capable of pyrolyzing biomass at high heat-transfer rates on the reactor wall by ablation and has been... 

In the heating and cracking phase, preheated hydrocarbons leaving the atomizer are intimately contacted with the steam-preheated oxygen mixture. The atomized hydrocarbon is heated and vaporized by back radiation from the flame front and the reactor walls. Some cracking to carbon, methane, and hydrocarbon radicals occurs during this brief phase. 

One of the most efficient implementations of the slurry process was developed by Phillips Petroleum Company in 1961 (Eig. 5). Nearly one-third of all HDPE produced in the 1990s is by this process. The reactor consists of a folded loop with four long (- 50 m) vertical mns of a pipe (0.5—1.0 m dia) coimected by short horizontal lengths (around 5 m) (58—60). The entire length of the loop is jacketed for cooling. A slurry of HDPE and catalyst particles in a light solvent (isobutane or isopentane) circulates by a pump at a velocity of 5—12 m/s. This rapid circulation ensures a turbulent flow, removes the heat of polymeriza tion, and prevents polymer deposition on the reactor walls. 

Typically, reactors require some type of catalyst. Reactors with catalyst can be of the fixed-bed style for fiuid-bed types. Fixed-bed reactors are the most common. The feed often enters the reactor at an elevated temperature and pressure. The reaction mixtures are often corrosive to carbon steel and require some type of stainless steel alloy or an alloy liner for protection. If the vessel wall is less than 6 mm, the vessel is constmcted of all alloy if alloy is provided. Thicker reactor walls can be fabricated with a stainless overlay over a carbon steel or other lower alloy base steel at less cost than an all-alloy wall constmction. 

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). 

Multiple zones for outer reactor wall, one for inner wall. 

Meccaniche Modeme (Busto Arsizo, Italy) acquired rights to the original AUied Chemical Company s concentric SO sulfonation unit (272). Table 10 shows comparative data on AUied s U.S. design, and that for Meccaniche Modem s concentric design, indicating equivalency. This unit has a substantial space between reactor walls, hence it requires a 6 m length to complete reaction. The process has been scaled up to 4.0 t/h capacity. 

The Stratford Engineering Company s (Kansas City, Missouri) continuous SO organic mist sulfonation uses a high speed atomizing rotor to horizontally disperse the organic feedstock stream impinging on the reactor walls in the presence of SO gas to effect sulfonation of petroleum feedstocks (290). 

EPM and EPDM mbbers are produced in continuous processes. Most widely used are solution processes, in which the polymer produced is in the dissolved state in a hydrocarbon solvent (eg, hexane). These processes can be grouped into those in which the reactor is completely filled with the Hquid phase, and those in which the reactor contents consist pardy of gas and pardy of a Hquid phase. In the first case the heat of reaction, ca 2500 kJ (598 kcal)/kg EPDM, is removed by means of cooling systems, either external cooling of the reactor wall or deep-cooling of the reactor feed. In the second case the evaporation heat from unreacted monomers also removes most of the heat of reaction. In other processes using Hquid propylene as a dispersing agent, the polymer is present in the reactor as a suspension. In this case the heat of polymerisation is removed mainly by monomer evaporation. 

Hot spot develops in reaction medium. Temperature excursion outside the safe operating envelope, possibly resulting in a runaway reaction or decomposition. Potential mechanical failure of reactor wall. 

To accelerate the polymerization process, some water-soluble salts of heavy metals (Fe, Co, Ni, Pb) are added to the reaction system (0.01-1% with respect to the monomer mass). These additions facilitate the reaction heat removal and allow the reaction to be carried out at lower temperatures. To reduce the coagulate formation and deposits of polymers on the reactor walls, the additions of water-soluble salts (borates, phosphates, and silicates of alkali metals) are introduced into the reaction mixture. The residual monomer content in the emulsion can be decreased by hydrogenizing the double bond in the presence of catalysts (Raney Ni, and salts of Ru, Co, Fe, Pd, Pt, Ir, Ro, and Co on alumina). The same purpose can be achieved by adding amidase to the emulsion. 

For this reason, operation around atmospheric pressures is typical. Space velocity should he high to avoid the reaction of ammonia with oxygen on the reactor walls, which produces nitrogen and water, and results in lower conversions. The concentration of ammonia must he kept helow the inflammahility limit of the feed gas mixture to avoid explosion. Optimum nitric acid production was found to he obtained at approximately 900°C and atmospheric pressure. 

Nearly every cat cracker experiences some degree of coking/fouling. Coke has been found on the reactor walls, dome, cyclones, overhead vapor line, and the slurry bottoms pumparound circuit. Coking and fouling always occur, but they become a problem when they impact throughput or efficiency. 

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. 

Creation of the correct shear conditions. High shear rate may be harmful to the organism and disrupt the cell wall low shear may also be undesirable because of unwanted flocculation and aggregation of the cells, or even growth of bacteria on the reactor wall and stirrer. 

The remaining reactors are of similar design as shown in Fig. 22. These are bottom fed, completely filled vessels. There is a central upward pumping screw surrounded by a draft tube through which coolant circulates. The reactant syrup descends in the annular space between the draft tube and the jacketed reactor wall. In this annular space is a circular rank of manifolded vertical tubes with circulating coolant... 

In which 100 cc could be polymerized. We used a pressure gage, rated from 0 to 140 pounds per square Inch. There were 3 type J thermocouples - one In the center of the solution, one In the reactor wall, and the third near the heater outside the reactor. The experiments were conducted In a high pressure bay and observed on closed circuit television. The Initial polymer concentrations of the test reactants were either 0 or 15 or 30 percent by weight. An electric heater controlled the ambient temperature of the nitrogen - purged reactor, and supplied heat to Initiate the reaction. 

In Phase II (see Figure 3) we used a 2900-cc pressure vessel, with a 2000-cc glass liner in which 1000 cc of solution could be polymerized. This was a 10-fold Increase over Phase I. We used a pressure gauge similar to Phase I. There were 5 type J thermocouples. Of these, there were k thermocouples within the reactor as compared to only 1 In Phase I. Two were In the solution within the glass liner, one was between the glass liner and reactor wall, and the... 

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