Autumn Semester 20110-11 Department of Paper Technology, IITR, Saharanpur Campus

PP-435 Paper Mill Calculations TUTORIAL Drying of Paper – Steam & Condensate Systems

1. Discuss the importance of efficient condensate removal from the drying cylinders.

2. How does the behaviour of condensate accumulating in a drying cylinder change with change in machine speed?

3. What factors influence rimming speed of a dryer?

Ans: The approximate value of rimming speed of dryer is given by 33.0)/30260( ctDu −=

Where u = rimming speed, m/min Tc = condensate film thickness, mm D = roll diameter, m

4. What are the functions of blow-through steam?

5. Discuss the working principle of siphons used for condensate removal from dryers. Describe different types of siphon constructions. Compare stationary siphons with rotary siphons.

6. Describe the cascade system of piping flash and blow-through steam in paper machine dryers.

7. Describe the thermo-compression systems of piping flash and blow through steam in paper machine dryers.

8. Tabulate typical steam pressures used in drying of different grades of paper.

9. What is ‘sloshing’ in dryers?

10. Discuss practical difficulties in increasing steam temperature in paper dryers.

11. Determine the pressure drop in a rotary siphon due to centrifugal force in a machine operating at 600 m/min.