Industrial Sector

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Key Areas of Investigation

• ELECTRICAL ENERGY
  An audit of all electrical consumption from each substation was completed to obtain a clearer picture of electricity consumption. It was found that the power factor could be improved.
• BOILERS AND STEAM SYSTEM
  A comprehensive investigation touched on these aspects: steam flow rate equipment: continuous boiler control; flash steam-, wort kettle vapour-, and condensate recovery from the brew house: use of steam accumulator; and condensate recovery from the packaging hall.
• COMPRESSED AIR
  This is an expensive form of energy and it was important to determine the efficiency and application.
• REFRIGERATION
  Streamlining the energy usage would include rescheduling of refrigeration loads, compressor sequencing and control, as well as cooling towers.
• AIR CONDITIONING
  It was noticed that small single units, which are not efficient in energy use, are used rather than efficient centralised units.
• ENERGY MANAGEMENT
  It appeared that the timing of production schedules was made arbitrarily. With little or no effect on the final product, these schedules could be changed to make a significant reduction in utility consumption and eventually costs.

Having highlighted the potential saving in energy costs, the team proceeded to evaluate these key issues according to succinct evaluation criteria.

Evaluation Criteria

The following table identifies some of the key areas where energy saving could be achieved resulting from this work and selected examples of other SAB initiatives. Where possible, these include: a cost estimate (which was a 'high-end cost' where a range was considered), the projected benefit to the company (in money terms), duration of the proposed project (time frames), the estimated return on investment (months) as well as the category of action required.
Proposed action for the case studies evaluated in this program were categorised as follows:

• IMPROVED HOUSEKEEPING (1) Covered by maintenance budget or required changes in behaviour and/or schedules
• LOW-COST MODIFICATION (2)
• RETROFIT (3) Refers to a significant one-off invest ment which is expensive in relation to the value of existing equipment
• SUBSTANTIAL CHANGE INVOLVING SIGNIFICANT INVESTMENT (4) Similar to retrofit, costs may be substantial and it usually requires capital outlay on new equipment

	Costs	Return	Payback	Category
Improved power factor correction	R60 000	R120 000 pa	6 months	(3)
Refrigiration load management	R650 000	R650 000 pa	1 year	(1 & 4)
Spent grain removal Load management	Zero	R6 000 pa	Immediate	(1)
Rigorous program for Saving compressed air	R75 000	R150 000 pa	6 months	(1)
Rigorous program for Saving steam	R100 000	R200 000 pa	6 months	(1)
Boiler automation	R100 000	R132 000 pa	9 months	(3)
Use of waste biogas	R32 000	R52 000 pa	9 months	(2)
Efficient lighting upgrades	R165 000	R165 000 pa	1 year	(3)

*All costs indicated above are 'high cost' estimates. In most cases actual costs will be lower.There are of course many more.

Selected Results

After having completed the more detailed analysis, new energy saving opportunities, as well as those listed in the walk through, were identified. The table below highlights some of the main recommendations from this work, and some other key SAB energy and money saving programs.

Other Areas of Activity

• Electrode Boilers (CT) SAB in Newlands, Cape Town, have recently switched from using coal and oil fired boilers to electrode boilers. This change has resulted in a boiler efficiency improvement of close to 15%, and the reduction of thousands of tons of local pollutants, a sensitive and scenic area.(4)
• Monitoring and targeting SAB has a national monitoring targeting program fostering competition and comparison between plants.(1)

	Costs	Return	Payback	Category
Improved power factor correction	R60 000	R120 000 pa	6 months	(3)
Refrigiration load management	R650 000	R650 000 pa	1 year	(1 & 4)
Spent grain removal Load management	Zero	R6 000 pa	Immediate	(1)
Rigorous program for Saving compressed air	R75 000	R150 000 pa	6 months	(1)
Rigorous program for Saving steam	R100 000	R200 000 pa	6 months	(1)
Boiler automation	R100 000	R132 000 pa	9 months	(3)
Use of waste biogas	R32 000	R52 000 pa	9 months	(2)
Efficient lighting upgrades	R165 000	R165 000 pa	1 year	(3)

Recommendations

• POWER FACTOR CORRECTION
  Existing power factor correction equipment could be upgraded to a power factor of greater than 0.97 to achieve a saving of approximately R120 000 per annum.
• COMPRESSORS
  Suggestions included: a riqorous leak detection and repair program, shifting compressed air loads (such as for the removal of spent grains) and investigating the most efficient compressor loading.
• REFRIGERATION
  The SAB plant at Prospecton had moved some of the load to off peak tariff times at night and this practice should be continued. Additionally, it may be possible to produce some, or all of the chilled liquor at night, and to store it for daytime use. Large quantities could be partially cooled or small quantities could be completely cooled. This would require a short optimisation exercise to determine the best practice with a projected desired payback.
• BOILER PLANT OPERATION AND STEAM USAGE
  Installing an in-situ oxygen probe at the ID fan outlet for real-time monitoring would help optimise combustion air to fuel ratios. A digital gauge for stoker speed measurement should be used and all measuring equipment calibrated.

A further energy saving is possible using biogas. Biogas produced in the purification plant could be piped to the boiler plant and introduced directly to the combustion chamber at the forced draft fan inlet. This should be viewed as an interim measure due to its short payback. The process could result in quicker (more energy and cost efficient) start-ups and, due to the large storage of biogas, help meet 'spikes' in steam demand. Approximately one km of HDPP pipe feeding the gas to the boilers, with the right pressure regulation, would act as a 'gas storage vessel'.
There is scope for a rigorous steam leak and trap repair program. This is ongoing at SAB and could be further encouraged via an energy management team.

ENERGY MANAGEMENT TEAM

TO ACHIEVE THE DESIRED RESULTS, THESE KEY ISSUES HAD TO BE ADDRESSED

• ENERGY MONITORING AND TARGETING
  (M&T). Prospecton currently has a well run utilities department and the minor adjustments required would not pose any difficulty. SAB has a national energy monitoring scheme, which allows different plants to 'compete' and be compared. Generic suggestions, for M & T as well as the topics that follow, are outlined in more detail in the 'How to' booklet of the 3E program.
• RESPONSIBILITY AND ACCOUNTABILITY
  (The following is a common theme in plants audited.) Due to the desegregated nature of 'utilities' consumption, not one particular division assumes responsibility for planning and cost effective utilisation. Significant savings can be achieved by introducing basic constraints to these various consuming sectors. These should be cost driven with final accountability resting with the accounts department and management. Incorporating a summary to an existing regular report could facilitate this. This would also provide a forum for recommendations and innovation.
• CHARGING USERS FOR CONSUMPTION
  This is recommended to improve maintenance and curtail wastage.
• REWARDING INITIATIVES AND PROVIDING INCENTIVES FOR STAFF
  'Energy efficiency' often requires engineers 'go the extra mile', as it is not yet accepted practice in South Africa. This might be adjusted by rewarding initiatives and creating incentives to motivate staff.

Bottom Line

INVESTMENT VS ANTICIPATED PERIOD OF PAYBACK

ALL MEASURES:

• The total investment required for the execution of all the above listed projects was R 1.18 million.
• The total annual energy earning for the above is: R1.37 million per annum
• This represents a saving of 8% of the total energy consumption
• The overall payback is approximately ten months

MAINTENENCE & LOW COST MEASURES:

• The total investment required for the execution of all the above listed maintenance and low-cost (category (1) & ((2))projects was R175 000
• The total annual energy earning for this is: R258 000 pa
• The payback for these measures (class 1 & 2) was about six months

ENVIRONMENTAL CONSIDERATIONS

• The adoption of all of the efficiency measures will result in a saving of 1 600 tons of coal pa with an associated reduction in emissions.