Maximize yield and minimize energy use

Process improvement objectives for the toner industry are influenced by many factors. In the traditional dry air jet grinding process, these include air flow, pressure, rotor speeds, pulverizer and classifier settings, and purge flows.

Malvern on-line particle size analysis has a role throughout the manufacturing process:

• Real-time particle size analysis can be used to adjust mill parameters, reducing the purge required at the start-up of each production run
• Locating the sampling points at strategic positions in the process contributes to the detection of process problems that give rise to out of specification product
• Real-time size data allow optimization and yield improvement of both mill and classifier lines by modeling and empirical correlation with other process parameters
• Enables real-time yield estimation, especially when multiple analyzers each monitor the performance of specific unit operations

Optimization methods include:

One-shot optimization

• Mill set up and hardware improvements
  Clients have told of respecifying classifier motors, optimizing nozzles on mills and optimizing purge air flows, following data taken from Malvern Process Systems analyzers
  
  

• Process understanding
  Although much process savings have come from simple data analysis from the in-process analyzers, Nexpress have used a systematic data mining approach to improve their process.
  
  

  	Case study - NexPress data mining - download a paper (requires free login)

  
  

Real time optimization

• Transient
  Start up and shut down savings are easily achievable with realtime knowledge of the particle size.
  
  
  
• Steady-state
  With real-time knowledge of the particle size at the exit of each unit operation, it is possible to keep the product within specification whilst varying mill/classification parameters to find the optimal values for each process parameter. This can be used to reduce unnecessary overgrinding, and allow automatic process control. By using more than one analyzer, realtime yield estimation is then possible.
  
  
  
• Non steady state
  Malvern Process Systems analyzers unique real-time sizing capabilities enable the detection of process upsets within seconds of their occurrence. Monitoring at multiple locations also helps to pinpoint the location of the problem, whether it is mill, classifier, or additive blending. Once the root cause has been determined, corrections can be applied in a timely manner. In contrast, an off-line measurement takes around 20 minutes resulting in a significant delay before any corrective action can be attempted.