Electricity + Control February 2016

ENERGY + ENVIROFICIENCY: FOCUS ON VALVES + ACTUATORS

Splitting a compressed air ring Energy efficiency opportunities

Rudi Joubert, Johann van Rensburg, Ruaan Pelzer, North West University; Consultants to HVAC International and TEMM International

The purpose of this study was to implement an energy efficient strategy on a compressed air ring of a South African gold mine.

S ustainable energy supply in South Africa requires ongoing new and innovative methods to ensure that production ac- tivities are maintained and that energy is conserved. South African gold mines are among the largest electricity consumers in the country [1]. The focus of the study was to reduce the electrical energy consumption of air compressors supplying compressed air to large compressed air rings at these mines. A typical mining compressed air system consists of air com- pressors, a pipe network and air consumers. These air consumers, or end users, include rock drills, loading boxes, pneumatic valve actuators and refuge chambers. Figure 1 shows the typical layout of a compressed air ring.

600

30

500

25

400

20

300

15

200

10

Flow in kg/s

Pressure in kPa

100

5

0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time in hours

Typicalpressure requirement

Typicalflow requirement

Figure 2: Typical shaft consumption.

Gold plant

Compressor house

Figure 3 shows the typical compressed air system pressure and air flow supply of the gold plant before implementation of this energy saving project.

Shaft

Control valve

Control valve

Control valve

Control valve

600

500

Shaft

Compressor house

Shaft

400

300

200

Flow in kg/s

Pressure in kPa

Figure 1: Typical layout of a compressed air ring.

100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

The air consumption, pressure requirement and time of use of the consumers also differ. Figure 2 shows the typical pressure and air flow consumption of a shaft. There are clearly defined periods of high and low consumption throughout the day. This is a result of the various combinations of pneumatic equipment in use. For example, rock drills are mostly used in the drilling shift, requiring high pres- sure and high air flow.

Time in hours

Typicalpressure requirement

Typicalflow requirement

Figure 3: Typical plant consumption.

The plant requires a constant high pressure for the pnumatic in- strumentation thoughout the day. Constant air flow is also required

Electricity+Control February ‘16

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