Improving 13 bar compressed air network at Sioen spinning part of Energy plan

The modification of the 7 bar compressed air network at our Spinning mill, directly provides an answer to the appeal of the UN set in goals 7, 12 and 9.

Two compressed air networks serve the spinning unit

Two compressed air networks serve the spinning unit. One at 7 bar, the other at 13 bar. This case is about the 13 bar network used both in the spinning application.

Problem definition: efficiency

In the event of a yarn break, production must be restarted. To do this, the vacuum required for restarting is obtained by means of a venturi, that is a short piece of narrow tube between wider sections for measuring flow rate or exerting suction. To do this, the 13 bar compressed air network is necessary.

An operator manually puts this venturi into operation. A break can be intentional (machine cleaning) or unintentional. A 160 KW compressor deserts this network at 13 bars. This compressor maintains the network pressure at 13 bars. Buffer tanks (two of 5 000 Lt and one of 10 000 Lt) have been installed on this network, as well as an additional compressor in order to limit the start/stop of the compressors.

The practice of the venturi operator therefore influences the efficiency of this 13 bar network, both in terms of costs and compressor use.

A visual alarm is triggered when the pressure drops below 13 bar. The operator must then ensure that no new venturi is started (e.g. during machine cleaning) and remedy the fault immediately.

Sioen has installed a SCADA system (abbreviation of Supervisory Control and Data Acquisition) to provide statistical data on the installation (number of breakages, duration and incidences).

Actions to improve process and energy efficiency

We’ve taken a number of actions to improve both operations and energy efficiency:

  • Pressure sensor near the venturi (or on buffer tanks) rather than at the compressors.
  • Logo box: in the event of a wire break, reduce the AC pressure to the minimum necessary for proper operation. When all breaks are repaired (venturis closed), raise the pressure to high values ( +/- maximum of the compressor) to avoid start/stop as much as possible. The Logo box also controls the second compressor (backup).
  • Migrate the operator alert system from a pressure alert to a use alert: red alert for new venturi opening when the maximum amount of open venturi is reached.
  • Periodic evaluation of the compressed air consumption by the operators based on measurements.
  • Installation of a small compressor to increase the operating hours.

Impact

The result of the measures taken have an impact on all levels, both financially and ecologically:

Impact

Electricity 43 000 kWh energy savings
Emissions 21 595 kgCO₂ reduction
Investments 50 518 EUR