TUbe-cooled reactor

As discussed above, several different types of ammonia converters are available. These types include axial quench converters (e.g., standard Kellogg reactors), tube cooled converters (e.g., TVA and Synetix designs), axial-radii designs (e.g., Ammonia Casale retrofit) and Kellogg s horizontal design. Typical operating data for different types of ammonia converters are shown in Table 6.4204. 

Catalytic methanation processes include (/) fixed or fluidized catalyst-bed reactors where temperature rise is controlled by heat exchange or by direct cooling using product gas recycle (2) through wall-cooled reactor where temperature is controlled by heat removal through the walls of catalyst-filled tubes (J) tube-wall reactors where a nickel—aluminum alloy is flame-sprayed and treated to form a Raney-nickel catalyst bonded to the reactor tube heat-exchange surface and (4) slurry or Hquid-phase (oil) methanation. 

Tube-Cooled Converter. The tube-cooled converter functions as an interchanger, consisting of a tube-filled vessel with catalyst on the shell side (Fig. 7c). The combined synthesis and recycle gas enters the bottom of the reactor tubes, where it is heated by the reaction taking place in the surrounding catalyst bed. The gas turns at the top of the tubes and passes down through the catalyst bed. The principal advantage of this converter is in... 

The Snamprogetti process utilizes a tubular isothermal reactor (tubes filled with catalyst) for the first reactor with cooling water on the shell side to control temperature. The Huls process uses either an adiabatic or isothermal reactor for the first reactor. 

On the other hand, this type of cooling permits the study of increasing or decreasing temperature profiles in the jacket and their influence on the inner temperature profile, reactor performance, and stability. For this type of study a reactor tube is needed that is large enough to accommodate an inner thermowell holding a multiple thermocouple assembly. 

Platinum and rhodium-platinum and iridium-platinum alloys are frequently employed to line and sheath autoclaves, reactor vessels and tubes, and a wide range of equipment. Linings are generally 0-13 mm to 0- 38 mm thick, and for certain applications co-extruded platinum-lined Inconel or other metal reactor or cooling tubes are fabricated. In such cases the platinum is bonded to the base metal, but in all other instances platinum linings are of the loose type. 

An exception to the above are fatty acid methyl esters, which, due to the reaction mechanism involving molecular rearrangements with excess S03, have to be sulfonated at a slightly higher mole ratio of S03 to methyl esters (namely, 1.15-1.20/L). Outside the reaction tubes, in the reactor jacket, cooling water is circulated to control the liquid-film temperature and removing the reaction heat. 

In the manufacture of aniline by the hydrogenation of nitrobenzene, the off-gases from the reactor are cooled and the products and unreacted nitrobenzene condensed in a shell and tube exchanger. A typical composition of the condensate is, kmol/h aniline 950, cyclo-hexylamine 10, water 1920, nitrobenzene 40. The gases enter the condenser at 230 °C and leave at 50 °C. The cooling water enters the tubes at 20 °C and leaves at 50 °C. Suggest suitable materials of construction for the shell and the tubes. 

The most common type of commercial pyrolysis equipment is the direct fired tubular heater in which the reacting material flows through several tubes connected in series. The tubes receive thermal energy by being immersed in an oil or gas furnace. The pyrolysis products are cooled rapidly after leaving the furnace and enter the separation train. Constraints on materials of construction limit the maximum temperature of the tubes to 1500 °F. Thus the effluent from the tubes should be restricted to temperatures of 1475 °F or less. You may presume that all reactor tubes and return bends are exposed to a thermal flux of 10,000 BTU/... 

Figure 11.6 Examples of methanol synthesis converters (a) tube-cooled, low-pressure reactor A nozzles for charging and inspecting catalyst B outer wall of reactor as a pressure vessel C thin-walled cooling tubes D port for catalyst discharge by gravity (b) quench-cooled, low-pressure reactor, A,B,D, as in (a) C ICI lozenge quench distributors (Twigg, 1996, pp. 450, 449 reproduced with permission from Catalyst Handbook, ed. M.V. Twigg, Manson Publishing Company, London, 1996.)...

A final mode of heat transfer in tubular reactors is the feed-cooled reactor, where the hot products from the reactor are cooled by the feed before it enters the reactor. As shown in Figure S-22, the cold feed in the jacket is preheated by the reaction in the inner tube or a heat exchanger is used for this purpose before the reactor. Temperature profiles for feed cooling are shown in Figure 5-22. 

The process in question involved the reaction of two materials, A and B, to produce a product C. The reaction was noncatalytic, homogeneous, and in the gas phase. It took place in a tubular reactor which could not be considered either adiabatic or isothermal. The reactor was divided into four sections, the first three of which were cooled while the fourth was adiabatic. Coking of the reactor tube introduced a time variant in the system, requiring adjustment of operating conditions and eventual shutdown for cleaning. 

Film cooling of rocket motors, turbine blades, reactor tubes, etc. (T17, K18, Y3). 

If flow is cocurrent the lower sign is used if countercurrent the upper sign is used. Since the mass flowrate of the cooling fluid is based upon the cross-sectional area of the reactor tube the ratio G Ip Gq SpC(= H is a measure of the capacities of the two streams to exchange heat. In terms of the limitations imposed by the onedimensional model, the system is fully described by equations 3.9S and 3.96 together with the mass balance equation ... 

Catalyst batches were activated under two different activation conditions H2/CO (with 3% Ar) = 2.6 3.87 xmol/s (FT synthesis reaction mixture with H2/CO = 0.7) for 2 h at (1) 523 K and (2) 543 K. These conditions are based on temperatures and gases used by PETC to activate these catalysts for testing prior to a large scale pilot plant run. After activation, reactions were carried out over the catalyst samples in the same reactor tube at 523 K with H2/CO = 0.7 and a total gas flow rate of 6.47 pmol/s (with Ar as internal standard) at a pressure of 83.8 kPa (normal atmospheric pressure in Albuquerque). Two sets of samples were made, one for each of the two activation conditions. Each set consisted of three samples after activation, activation followed by FT reaction for 10 h, and activation followed by FT reaction for 45 h. In the case of the activation at 523 K, the first 2 h of the run were considered the activation step. Therefore, the activation in this case was at 523 K. For activation at 543 K, the catalyst bed was cooled to 523 K in the syngas mixture of activation. 

Since the cooling jacket has cocurrent flow, the model consists of the set of four coupled initial value differential equations (7.5) to (7.8). Note that the first three DEs (7.5) to (7.7) contain the variable catalyst effectiveness factor rj. Thus there are other equations to be solved at each point along the length 0 < / < Lt of the reactor tube, namely the equations for the catalyst pellet s effectiveness factor rj. 

There is a jacket outside the reaction vessel for heat exchanging, which enables one to cool or heat the process mixture inside the reactor. When cooling the mixture, cold water or another cooling medium enters the jacket through the lower inlet tube (8) at the bottom and flows out through the upper outlet tube (9), while for heating the... 

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