Advanced Process Control - Opportunities and Benefits

There has always been anecdotal opinion that advanced process control will save between 2 and 7% of operating costs. This is supported by several studies that have investigated the profitability of advanced control in process industries:

Warren Centre Project 1987 (University of NSW)

  • survey of Australian industry
  • savings of 1.5 to 6% of annual operating costs
  • potential for $750M pa. in Australia

Dupont Study 1991

  • search for the "best of the best" in process control
  • the best had auditable savings of 15 %
  • average savings were 7 % of operating costs pa.
  • estimated US$ 0.5 billion pa. savings in Dupont

ICI Benchmarking Study 1992

  • extrapolation of existing ICI experience
  • savings conservatively estimated at 7 %
  • ICI worldwide would benefit by A$ 1 billion pa.

ICI (now Orica) have achieved very significant returns from auditing their plants and implementing advanced controls. They have quoted worldwide savings of:

  • $ 28 million in 1993
  • $ 36 million in 1994.

They still have a long way to go, but are limited by the short supply of skilled control systems engineers.

The Paper Industry has recognised many of the benefits attributable to process control and has invested in the technology. Higher level controls on paper machines, such as grade change, throughput maximisation, adaptive target moisture control, etc. were purchased with Measurex, Valmet and ABB systems (and helped justify the expenditure), but are commonly not used effectively for various reasons.

Automatic grade change packages are essential as the industry moves to just-in-time and shorter production runs. The losses incurred during a grade change can be minimised by achieving stable operation faster by the use of more advanced control strategies. Effort needs to be invested to determine why higher level controls are not being used and to remove the obstacles preventing the benefits from being obtained.

The Distributed Control Systems (DCS) installed in mills are providing benefits due to better visibility of the process and controls, but the advanced features enabling "smart control" are under-utilised. This is due to a number of reasons, including lack of awareness of system capabilities, but mainly it is due to a lack of suitably qualified control engineers to identify the need and to implement more complex control strategies.

Examples of candidates for advanced control strategies are: refiner controls, co-generation, load shedding, steam header control, consistency control, chemical addition control, etc. A more complete list of opportunities is in the appendix. Audits should be conducted to identify these opportunities. This is an area promising very good returns for very little capital investment.

Advanced process control requires a specialist set of skills. Procex can provide those skills along with others developed over 20 years in the pulp and paper industry. Areas covered include:

  • Advanced Process Control
  • Multivariable Control
  • Mill Information Systems
  • On-line Cost Of Production Systems
  • Grade Registers
  • Quality Systems
  • Process Databases
  • Process Scheduling
  • On-line Operator Logs
  • On-line Documentation
  • Expert Systems

The ability to focus on both the IT and process control areas provides the opportunity to develop integrated systems for the information and control needs of pulp and paper mills.

Procex can provide the following services:

  1. Investigation of opportunities to improve manufacturing operations by the effective use of Information Technology, and advanced control and optimisation.
  2. Provision of decision support systems in areas such as production scheduling, quality and cost.
  3. Assistance with troubleshooting and rectifying of process control problems.
  4. Process control performance audits on a regular basis to ensure benefits continue to be achieved (control systems do degrade over time).

These services can add value to Continuous Improvement and Asset Management initiatives.

There are opportunities for good payback through the application of more advanced process control and optimisation of processes. Some of these are listed in the appendix. Implementing decision-support and advanced process control opportunities would be significant steps towards maximising the efficiency of your assets.

Many opportunities can be identified by auditing the performance of existing systems. Call Procex to discuss the opportunities.

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APPENDIX - Advanced Control and Optimisation Opportunities

Paper Machine
Grade change - reduced broke, increased production
Stock consistency control - reduced product variability
Refiner control - reduced energy cost, consistent freeness
Speed optimisation - increased output reduced fibre
CD controls - increased output, reduced fibre
Retention control - reduced chemical cost
Size addition - reduced chemical cost
Drainage aid addition - reduced energy cost, reduced chemical cost, increased output
Adaptive target moisture control - increased output, reduced fibre
Control of strength properties - reduced fibre, lower chemical and energy costs
Flocculation control - reduced variability, fewer web breaks, improved formation & strength
Pulping & Bleaching
Increased yield - lower wood, chemical and steam costs or increased output
Decreased residual - lower chemical cost, lower recovery cost
Washer control - lower chemical cost and losses, lower recovery cost
Consistent quality - better paper machine runnability
Dynamic scheduling - decreased shutdowns and lost production
Waste Paper Plant
Hydrapulper optimisation - increased output
Improved unit control - less downtime, less spillage
Recovery/Recausticisation
Evaporator control - consistent solids content, reduced gas firing
Evaporator boil-out scheduling - lower steam costs, greater throughput
Sootblowing optimisation - lower steam consumption, greater steam generation
Lime kiln optimisation - lower gas usage
Power Plant
co-generation - minimise electrical purchase
load shedding - minimise maximum demand charges
steam header control - lower energy costs
boiler/turbine optimisation - lower energy costs
excess oxygen control - lower energy costs

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