Ask Question, Ask an Expert

+1-415-315-9853

info@mywordsolution.com

Ask Chemical Engineering Expert

Film Mass Transport:

problem: Sulfur trioxide (SO3) is manufactured by the gas-phase oxidation of SO2 over a platinum catalyst:

SO2 + 1/2 O2 → SO3

The catalyst is a non-porous extrudate with the platinum deposited on the outside surface. The following data have been measured for the particle rate of reaction as a function of SO2 concentration in the bulk gas at 450 °C

2430_film maas transport.jpg

The following data apply to this problem:

? B (void fraction) = 0.43
Catalyst = 1/8 x 1/8 inch (diameter x length) extrudates (Pt on surface only)
At (specific external surface area of catalyst) = 5.12 ft2/lb
DSO2/air = 1.1 ft2/h
μ air = 0.09 lb/hr-ft
ρair = 0.0304 lb/ft3

Without calculating anything, what can you tell about the importance of film mass transport on this reaction? describe briefly.

problem: describe why mass transfer resistance reduces the global rate more at higher temperature than at lower temperature.  Assume no heat transfer resistances are present.

problem: A gas-phase catalytic reaction is taking place in a Packed Bed Reactor (PBR). The system is isothermal but film mass transfer resistances are important.

a) Would increasing the turbulence in the gas phase increase or decrease the global rate?

b) If the system is not isothermal and the reaction is exothermic would increasing the turbulence increase or decrease the global rate?

problem: Experimental global rate data for the oxidation of SO2 over a non-porous platinum catalyst are given in the table below for two levels of conversion of SO2.  Estimate the importance of film mass transport from these data by calculating the concentration difference (for SO2) between the bulk gas and the catalyst surface.

DATA:

a) Packed-bed reactor (PBR); catalyst consists of 1/8 x 1/8-inch (radius x length) tablets
b) Packing void fraction (εB) = 0.36
c) Superficial mass velocity (G) = 147 lb/hr-ft2
d) Pressure = 790 mm Hg; Temperature (assume isothermal) = 480 °C
e) Bulk gas concentration: 6.42 mol% SO2 and 93.58 mol% air
f) Specific external surface area of catalyst (am) = 5.12 ft2/lb

1718_film maas transport_2.jpg

rp = particle rate of reaction (rate per unit external surface area of catalyst)

problem: Cumene (C) is catalytically cracked to manufacture benzene (B) and propylene (P). The following non-stoichiometric equation illustrates the chemistry:

C → B + P

Typical operating conditions for this reaction are a temperature and total pressure of 362 °C and 1.0 atm. respectively.  A measurement of the global rate of reaction was made in the laboratory, resulting in the following value for the rate of disappearance of cumene:

rp = 76.5 kmol/m2 – h

From the data supplied, is there any evidence of either heat or mass transfer limitations for this reaction? Be as quantitative as possible in your explanation.

Assumptions:

The catalyst particle is non-porous. All thermo physical properties (density, viscosity, thermal conductivity, etc.) of the bulk gas and gas in the film can be assumed to be constant.

Data:

Average MW of gas = 34.37 kg/kmol
Gas density = 0.66 kg/m3
Gas viscosity = 0.094 kg/m – h
Gas thermal conductivity = 0.037 kcal/m – h - °C
Gas heat capacity = 33.0 kcal/kg – °C
G (mass velocity) = 56,470 kg/m2 – h
at = am = 45 m2/kg cat (specific external surface area of catalyst)
εB (bed void fraction) = 0.5
dp (catalyst particle diameter, equivalent sphere) = 0.1 cm
ΔHr (heat of reaction) = +41,816 kcal/kmol (endothermic)
Ea (activation energy for reaction) = 40 kcal/gmol
ρB (catalyst bulk density) = 5x105 g/m3
Sc (Schmidt number) = 1.483

Chemical Engineering, Engineering

  • Category:- Chemical Engineering
  • Reference No.:- M9305

Have any Question? 


Related Questions in Chemical Engineering

An electric motor under steady load draws 97 amperes at 110

an electric motor under steady load draws 9.7 amperes at 110 volts,dellivering 0.93Kw of mechanical energy.what is the rate of heat transfer from motor ,in Kw?

Question 1 a give three examples for each of natural free

Question 1. (a) Give three examples for each of natural (free) convection and forced convection which occur in industrial processes. (b) The Grashof number and the Reynolds number appear in most correlations of experimen ...

A solar collector design consists of an inner tube enclosed

A solar collector design consists of an inner tube enclosed concentrically in an outer tube that is transparent to solar radiation. The tubes are thin walled with inner and outer diameters of 0.10 and 0.15 m, respectivel ...

Current and charge in a battery consider a car battery

Current and charge in a battery. Consider a car battery rated at 100 A· h. This battery can supply a current of 100 A for an hour. (a) How much charge can the battery supply? (b) What must be the area of a parallel plate ...

An experiment involves heating a very small sphere that is

An experiment involves heating a very small sphere that is suspended by a fine string in air with a laser beam in order to induce the highest sphere temperature possible. After inspecting Equation 9.64, a research assist ...

Application convection current the solar wind is a stream

Application: Convection current. The solar wind is a stream of mostly protons emitted by the Sun as part of its normal reaction. The particles move at about 500 km/s and, at the Earth orbit, the particle density is about ...

A potential flow source having an intensity of 10m2s placed

A potential flow source having an intensity of 10m2/s, placed in the point of Cartesian coordinates (1;0), and a sink having identical intensity, placed in the point (-1;0), are combined with a uniform flow at 25 m/s, in ...

A horizontal 100-mm-diameter pipe passing hot oil is to be

A horizontal 100-mm-diameter pipe passing hot oil is to be used in the design of an industrial water heater. Based on a typical water draw rate, the velocity over the pipe is 0.5 m/s. The hot oil maintains the outer surf ...

Application capacitor with space charge between plates the

Application: Capacitor with space charge between plates. The parallel plate capacitor in Figure 6.41 is given. In addition to the data in Problem 6.1, there is also a charge density everywhere inside the material such th ...

Potential difference and resistance a conducting sphere of

Potential difference and resistance. A conducting sphere of radius a, with conductivity u is cut into two hemispheres. Then, each hemisphere is trimmed so that it has a flat surface on top and the two sections are connec ...

  • 4,153,160 Questions Asked
  • 13,132 Experts
  • 2,558,936 Questions Answered

Ask Experts for help!!

Looking for Assignment Help?

Start excelling in your Courses, Get help with Assignment

Write us your full requirement for evaluation and you will receive response within 20 minutes turnaround time.

Ask Now Help with Problems, Get a Best Answer

WalMart Identification of theory and critical discussion

Drawing on the prescribed text and/or relevant academic literature, produce a paper which discusses the nature of group

Section onea in an atwood machine suppose two objects of

SECTION ONE (a) In an Atwood Machine, suppose two objects of unequal mass are hung vertically over a frictionless

Part 1you work in hr for a company that operates a factory

Part 1: You work in HR for a company that operates a factory manufacturing fiberglass. There are several hundred empl

Details on advanced accounting paperthis paper is intended

DETAILS ON ADVANCED ACCOUNTING PAPER This paper is intended for students to apply the theoretical knowledge around ac

Create a provider database and related reports and queries

Create a provider database and related reports and queries to capture contact information for potential PC component pro