Reactor cylindrical adiabatic

Figure 1.3.2 gives another perspective for scale-down to recycle reactor studies. In this actual case, after preliminary studies in a recycle reactor, a 5-stage adiabatic reactor was envisioned (Betty 1979.) Scaling down the proposed commercial reactor, a 3 diameter tube was designed with elaborate temperature compensation (heating and insulation) for pilot-plant studies (Betty 1968, 1969.) Small squares in the proposed reactor represent side views of cylindrical catalyst cutouts for the recycle reactor... 

Here n represents the direction normal to the wall, x, is a convective heat transfer coefficient, is the temperature of the wall, and 7], is the fluid temperature in the immediate vicinity of the wall. The right-hand side of Eq. 7.2.d-1 would be zero for an adiabatic reactor. Equation 7.2.C-2 then becomes, when averaged over cylindrical geometry, with diameter d. 

The linear stability analysis of the longitudinally propagating fronts in the cylindrical adiabatic reactors with one overall reaction predicted that the expected frontal mode for the given reactive medium and diameter of reactor is governed by the Zeldovich number ... 

An adiabatic reactor consists of a cylindrical vessel with elliptical heads, with an inside diameter of 6.5 ft (78 in.) and a tangent-to-tangent length of 40 ft (480 in.). Gas enters the reactor at a pressure of 484 psia and 800°F. Exit conditions are 482 psia and 850°F. The vessel will be oriented in a horizontal position. Estimate the vessel thickness in inches, weight in pounds, and purchase cost in dollars for a CE cost index of 400. The vessel contains no internals and the gas is non-corrosive. The barometric pressure at the plant site is 14 psia. 

SJi. The initial startup of an adiabatic, gas-phase packed tubular reactor makes a good example of how a distributed system can be lumped into a series of CSTRs in order to study the dynamic response. The reactor is a cylindrical vessel (3 feet ID by 20 feet long) packed with a metal packing. The packing occupies 5 percent of the total volume, provides 50 ft of area per of total volume, weighs 400 ib yft and has a heat capacity of 0.1 Btu/lb °F. The heat transfer coefficient between the packing and the gas is 10 Btu/h It "F. 

Reforming in the CRG process occurs adiabatically at 450-550 C at pressures up to about 600 psig (41 atmospheres). The reactor is a vertical cylindrical pressure vessel containing a bed of the special high-nickel catalyst which is supported on a grid or on inert ceramic halls. The gas flow is downwards through the bed and distributors are provided at inlet and outlet. A layer of ceramic balls on top of the bed prevents disturbance of the catalyst by the entering gas. 

Adiabatic fixed-bed reactors constitute the oldest fixed-bed reactor configuration. In the simplest case they consist of a cylindrical jacket in which the catalyst is loosely packed on a screen support and is traversed in the axial direction (Fig. 9A). To avoid catalyst abrasion by partial fluidization, random catalyst packings arc always traversed from top to bottom. If fixed-beds composed of monolith catalyst sections are used, the flow direction is arbitrary. 

Ethylene feed and catalyst solution enter the bottom of the cylindrical reactor where the reaction proceeds at 125-130 C (255-265 °F) and 8-9 atm. (100-115 psig). The reactor contains internal distributors to insure good vapor-liquid distribution. Ethylene conversion is 96.7< 7o and selectivity to acetaldehyde is 9B.2 o. Even though there is a high exothermic heat of reaction, the reactor temperature is nearly isothermal because of the large quantity of catalyst solution circulated to the reactor. The reactor effluent is flashed adiabatically. Acetaldehyde product, unreacted ethylene, and flashed steam constitute the overhead vapor from the flash drum, and the catalyst solution is pumped from the bottom. 

Consider a cylindrical tower filled with a solid-supported catalyst. The feed is liquid and flows upward through the reactor. The reactor operates adiabatically. The geometric variables are reactor diameter D [L] reactor length L [L], which is the height of the catalyst mass and solid-supported catalyst pellet or extrudate diameter Jp [L]. The material variables are fluid viscosity /x [L MT ], fluid density p [L M], fluid—solid heat capacity Cp [L MT 0 ], fluid—solid heat conductivity k [LMT 0 ], and molecular diffusivity Z>Difr [L T ]. The process variables are... 

Reactors most commonly used in the process consist of cylindrical vessels containing the catalyst in an adiabatic fixed bed with a maximum depth of about 10 ft. The bed depth-to-diameter ratio is normally less than 1 1. In cases where the concentration of acetylene in the feed gas is sufficiently high to cause an excessive temperature increase during the conversion operation, isothermal tubular reactors are used, with the catalyst inside the tube and a coolant on the outside. 

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