|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)
Dupont Study 1991
ICI Benchmarking Study 1992
ICI (now Orica) have achieved very significant returns from auditing their plants and implementing advanced controls. They have quoted worldwide savings of:
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:
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:
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.
APPENDIX - Advanced Control and Optimisation Opportunities
|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|
|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|
|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|