| A laboratory sheet former using the twin-wire concept has been designed and constructed. It is capable of simulating a wide range of industrial papermaking conditions and can generate a pressure profile very close to that of an industrial machine. The machine has three components: the headbox section, the drainage section and the sheet pick-up section. All three sections are activated and brought up to operating speeds independently, with the headbox flow being diverted back into a reservoir. Once all systems are running at their operating conditions, the headbox flow is diverted to form a jet and steady-state sheet forming occurs for a certain period. The sheet and seven white water streams are collected during operation.;The system is currently able to simulate the papermaking process up to the beginning of the vacuum drainage section; the sheet which it creates has a consistency in the vicinity of 11%. Mass balances of better than 95% have been achieved for both water and fibre. The magnitude of the pressure profiles generated has been measured or calculated. Continuing work will bring the sheet consistency into the 15% to 20% range; once this is attained, an efficient tool to optimize wet-end chemistry will be available. |
