SECTION 1: WOODYARD 1. Your pulp mill is experiencing quality and production problems which have been traced to the debarker. As the process te2/4 ian in the mill explain what recommendations you would make to the operating staff in order to improve the efficiency of the debarker. (5) 2. The quality of chips produced in the woodyard has a major influence on pulp quality. Give a detailed discussion on chipper operation under the following headings: a) Optimum chip size (3) b) Chipper set up (7) c) Chip storage (4) [19] SECTION 2: MECHANICAL PULPING 5 1. Draw a labeled graph showing the effects of stone sharpness on PGW quality, power consumption and throughput. (5) 2. Explain the term "pitless grinding". (2) ( 3. What are the operating parameters of the steaming vessel in the TMP process. (3) 4. Discuss the effects of consistency during TMP refining. (7) 5. Explain how freeness is controlled in the TMP process. (2) 6. What are the approximate CSF values in the pressurized refiner and the atmospheric refiner? (2) [21] SECTION 3: CLEANING, SCREENING AND REFINING 1. Centrifugal cleaning systems are an essential component in pulp and papermaking systems. Draw a labeled diagram of a three stage cleaning system. Your drawing must show the direction of all flows in the system. (5) 2. List and discuss the design and operating variables of the centrifugal cleaner. (8) 2 Pulp and Paper Technology 1 - 2012 Main Examination 3. Explain what changes you can make to the pressure screen in order to improve its efficiency (4) 4. A simple cleaner has a feed stream consisting of 97% fibre and 3% debris. The cleaner reject rate is 30%. What is the compositions expected in the accepts and rejects streams? The cleaner operating curve is attached. (7) 5. The development of fibres which happens in the refiner has a direct influence on paper strength properties, so it is important to understand the technology of refining. Explain what is meant by the following terms: (3) a) Specific Refining Energy b) Cutting edge length c) Specific edge load 6. How do the following plate design properties affect Refiner performance: a) CEL b) Bar width c) Groove width d) Groove depth e) Bar angle (5) [38]