Exam Paper: Process Plant Equipment (MECH 8017) for BSc (Hons) in Process Plant Tech, Exams of Process Engineering

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CORK INSTITUTE OF TECHNOLOGY

INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ

Autumn Examinations 2010

Module Title: Process Plant Equipment

Module Code: MECH 8017

School: Mechanical and Process Engineering

Programme Title: Bachelor of Science (Honours) in Process Plant Technology – Award

Programme Code: EPPTE_8_Y

External Examiner(s): Mr. N. Kingston, Mr. J. Phelan Internal Examiner(s): Dr. Francis Murphy

Instructions: Answer THREE Questions

Duration: Two Hours

Sitting: Autumn 2010

Requirements for this examination:

Graph paper and Mathematical Tables to be provided

Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.

Q1. A process for the sulfonation of phenol requires the use of a 13.6 m^3 storage vessel. Corrosion data indicate that only a few corrosion resistant alloys will be suitable for construction of this vessel. Vessel Type Installed Cost Corrosion Rate Nickel Clad €100,000 0.5 mm/year Monel Clad €115,000 0.25 mm/year Hastelloy B €200,000 0.11 mm/year The life of the storage vessel is calculated by dividing the corrosion allowance of 3 mm by the estimated corrosion rate. The equipment is to have a salvage value of 10 percent of its original cost at the end of its useful life. The time value of money is to be taken into account by use of an interest rate of 10 percent. Determine which material of construction would be used with appropriate justification for selection. (34 Marks)

Q2. (a) Many fine materials (coal, starch, sugar, rubber, plastics, certain metals, pharmaceuticals, etc.) can explode once they are dispersed in air as a cloud. Describe the inerting method of preventing the formation of explosible dust clouds. (14 marks) (b) Three explosible materials are being mixed in a vessel. Calculate the number of purges to achieve the required concentration in the mixer (3 bar nitrogen is available) assuming a mixing efficiency of 0.5 (Assume 50% by volume of the dust feed is air). (20 marks)

DATA:

Vessel volume = 5 m^3 , Design pressure = 2.0 bar, Yield pressure = 5.0 bar. Recommended LOC safety margin = 2% Material Bulk Density (kg m-^3 ) Feed Rate (kg hr-^1 ) LOC % V/V A 400 600 10. B 500 500 15. C 625 450 5.

FORMULAE:

SYMBOLS:

Cn  O 2 concentration after^ n purges;^ C 1 (^)  O 2 concentration initially; P 1  Lower purge pressure (abs); P 2 upper purge pressure (abs) n ^ Number of purge cycles;^ K mixing efficiency. LOC = limiting oxygen concentration; V = volume.

Q3. (a) Describe with sketches where necessary, the gravity conveyor (air-slide) in which fluidised solid particles flow under the influence of gravity. (14 marks) (b) Design a gravity conveyor for conveying 30 t/h of alumina particles with a particle density of 1300 kg/m^3 and a mean particle diameter of 60 μm, over a distance of 20 m. (20 marks)

DATA:

Width (b) of Conveyor (mm) Conveyor Capacity (m^3 /h) 100 15 200 55 300 125 400 280 500 560 600 730 750 1000 900 1500



n 

ln

Cn

C 1













ln

P 1

P 2













K













Voidage at minimum fluidisation (



 mf ) = 0.4 Particle density (



 p ) = 1300 kg/m^3

Air density (



) = 1.2 kg/m^3 Air viscosity (



) = 1.78(10-5) kg/m/s

Particle sphericity (



) = 0.8 Particle volume-surface mean diameter (



d ) = 60 μm Recommended height of fluidised bed (Z) = 0.12 m FORMULAE: Minimum fluidisation velocity for Reynolds Number less than 20:



 mf   mf

3

150(1 mf )

(  p ) g

 ( dv^ )

2

Operating fluidisation velocity =



1.5  mf

Reynolds Number at minimum fluidisation:



Re mf  mf ^  d^ 

Pressure drop across the bed:



 pbed  g  B Z

Bulk density of solid:



 B  (1 mf )  p

Air requirement;



Q^ Ý  bL

Q4. Determine the reinforcement requirements for a 300 mm diameter opening in a cylindrical pressure vessel 1 m diameter subjected to an internal pressure of 5 MPa. The shell and nozzle allowable stress is 120 MPa. The shell and nozzle thickness are 25 mm and 32 mm, respectively. The reinforcement scheme is shown in Figure (Question 4) and may require extra reinforcement of thickness tp. (34 marks) FORMULAE: (based on the ASME design philosophy)

The minimum required shell thickness is given by: trs  (^) S  PR 0.6 sP

Reinforcement limit parallel to shell surface is the larger of ts+tn+0.5d or d. Reinforcement limit normal to the shell surface is the smaller of 2.5ts or 2.5tn

SYMBOLS:

P = Design Pressure Rs = Shell Radius S = Allowable Stress d = opening diameter

Figure (Question 4):