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

According to experimental results for parallel airflow over

According to experimental results for parallel airflow over a uniform temperature, heated vertical plate, the effect of free convection on the heat transfer convection coefficient will be 5% when GrL/Re2L = 0.08. Conside ...

A well is producing from a saturated oilreservoir with an

A well is producing from a saturated oilreservoir with an average reservoir pressureof 3000 psig. Stabilized flow test dataindicates that the well is capable of producing400 STB/day at a bottom-holeflowing pressure of 25 ...

A draw an arbitrary closed contour on figure 711 and show

(a) Draw an arbitrary closed contour on Figure 7.11 and show that it yields zero net flow of current. (b) Suppose a capacitor is inserted into the circuit instead of any of the resistors and the current is switched on. D ...

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 ...

The total capital investiment for a chemical plantis 1

The total capital investiment for a chemical plantis $1 million, and the working capital is $100,000. if the plant can produce an average of 8000kg of fixed product per dayduring 365-day per year, what selling price in d ...

Because of shortage of copper it was decided to make the

Because of shortage of copper, it was decided to make the fuse in Example 7.4 out of iron (not a very good idea because of corrosion). If the same dimensions, including the width calculated in Example 7.4a are used and t ...

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 ...

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 ...

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 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 ...

  • 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

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

Describe what you learned about the impact of economic

Describe what you learned about the impact of economic, social, and demographic trends affecting the US labor environmen