Save energy with vacuum system optimization in board and paper machines

Saving energy with vacuum systems

There is vast potential for energy savings in vacuum systems – more than 50% of all paper machines suffer from poor operating efficiency in their vacuum systems. The required modifications are often relatively small compared to the savings gained, and the payback time is short.

Most vacuum systems are not designed to operate in current operating conditions – they are highly over-dimensioned and consume too much energy. The increased demand for recycled fiber has a strong effect on fiber quality and therefore presents a challenge to vacuum system capacity requirements.

Many vacuum systems also use ineffective pumps. Valmet’s Vacuum System Optimization service reveals these inefficiencies and presents a plan to improve vacuum efficiency or replace the existing equipment.

Better efficiency, lower energy consumption

Vacuum System Optimization is a comprehensive solution for identifying and realizing significant energy savings in vacuum systems. The primary cause of efficiency losses in a paper machine vacuum system is control of the vacuum level, as efficiency losses can be high when the pump capacity does not match
the requirements of the paper machine. In these cases, the vacuum control logic needs to be updated. In a conventional liquid ring pump (LRP) system, the vacuum is controlled using bleed air, but similar losses can also occur in blower systems when there is a lot of variation in the air flow from the paper machine.

Valmet’s Vacuum Optimization provides:

  • Better efficiency
  • Reduced energy consumption
  • Immediate savings
  • Improved control
  • Increased stability


Vacuum system

Over

100 machines

screened so far

Cost savings with perforated Uhle Box Covers

Perforated Valmet Uhle Box Covers are an effective and straightforward solution for increasing dewatering and reducing energy consumption in the press section. There are two ways perforated covers can be applied: either by replacing the conventional Uhle Box Cover with a perforated one for increased dewatering, or by modifying the existing vacuum system to produce significant savings, and then replacing the cover.

Perforated Uhle Box Covers and the vacuum system study and modifications of Valmet’s Vacuum Optimization combine to facilitate considerable savings on production costs.

Customized on-site study and pre-engineering

Valmet’s vacuum system energy efficiency study begins with either a screening or a more thorough on-site study. The on-site study is used to create a two-phase action plan, with both phases taking a functional approach to optimizing energy consumption.

Rapid results can be obtained with relatively small changes such as optimizing the piping connections and running parameters, and installing new perforated covers. A more extensive approach is also presented that weighs the costs and benefits of long-term investments. As soon as a need for further action is identified, the engineering steps needed are initiated.

 

1. Screening (initial estimation of potential energy savings)

Benchmark

2. Pre-engineering and on-site study

Step 1: Immediate savings through optimized running parameters and Valmet Uhle Box Covers >> rapid payback

Step 2: Investments in new technology >> long-term plan and payback

Studies

3. Required engineering

   - Process engineering

   - Mechanical engineering

   - Automation engineering

Engineering

4. Installation and start-up

   - Typically 2-day shutdown

   - Fine tuning and measuring the energy savings achieved

Implementation

 

Vacuum System Optimization for energy savings

The vacuum system upgrade itself is usually carried out in two stages. The first stage involves modifying the vacuum controls and pump connections. The second stage, featuring new variable-speed drives, takes place later, as the operation of the vacuum system must be observed for at least two felt life cycles in order to estimate what additional energy savings potential exists. Alternatively, the second stage can employ blower technology to replace water ring pumps.

Vacuum System Optimization is suitable for all vacuum systems with LRP pumps and blowers, regardless of the machine supplier.