SugarCost

Cost Control for the sugar industry
D H Mallalieu and Associates Ltd.

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Production - Factory Operations
 
Summary
• The effect of high fibre in cane
• The effect of pol% in cane
• Sugar Production
• Steam Balance
• Production Cost Estimates
• Avoided Costs
• Other Factory Operations Reviewed

Summary; A review of factory operations will differ for the two operating conditions:
• For a factory with an annexed co generator and/or ethanol production plant
• A factory dedicated to the manufacture of raw or refined sugar only

The reporting of cogeneration performance and ethanol plant productivity are dealt with separately. However, both these have a common requirement; the factory steam utilization.

For a factory producing ethanol and co generating power for export, a steam consumption rate in excess of 850 lb steam per ton cane ground is not acceptable and it will be advisable to carry out a steam utilization review to attempt to reduce this consumption. On the other hand, a factory limited to sugar production will not be faced with this requirement. In this case, with uninterrupted milling, handling of surplus bagasse may be a major expense. In the past this mitigated against improving steam economy, but with today’s energy costs this should be looked at differently

See section on Heat Balance following

The Effect of High Fibre % in Cane; As in the case of factory steam consumption, fibre in cane becomes more or less important depending on the configuration of the factory.

For the factory limited to sugar production, the effect of high fibre on mill extraction is known, and will be evident from the milling reports. The impact on milling capacity is also well known, this becomes very obvious when the factory is grinding burnt cane. For green cane the surplus bagasse handling now becomes a concern, and although not reported in the literature, grinding excessive fibre must result in increased roller wear.

However, when co generating power for export this situation is completely reversed. The co generating models completed for this program all show a dramatic increase in steam production with increased fibre in cane. To the extent that trash collected in the fields is now considered as supplementary fuel.

It follows that if cogeneration is proposed, and the cane supply is as a result being changed from burnt to green cane, to increase fibre, the new operating conditions must be reviewed. These include the reduction in extraction and capacity noted previously, increased steam consumption to the mills, possible increase in maceration and potential capacity problems with the evaporators. In short, a feasibility study and steam balance may be warranted.

It is possible to detrash the cane before milling to avoid the situation outlined above, but this may lead to different problems

The Effect of Pol% in Cane; The harvesting program outlined earlier is intended to deliver fresh cut cane to the factory avoiding deterioration in cane quality. But it is known that the pol% in cane will vary during the crop, usually with a profile from low at the start of crop, rising to a high at mid crop and then decreasing; the weather having a significant effect.

However sugar production is dependant on the sucrose in cane, and a significant reduction will seriously affect the profitability of the operation. It may occur that the fall in pol late in crop could make continued milling uneconomic, but the cane has to be cut.

The commercial version of SugarCost shows the effect of varying Pol in cane on profitability.

Sugar Production; the estimated weekly production is compared with the actual production in the table below. The working Demo gives a full development of this table.


 

Steam Balance; A data sheet has been finalised for the preparation of a complete heat balance if required. This sheet is in two sections; a physical description of the plant and operating records for each system. The level of detail will permit an evaluation of the evaporator and vapour extraction if of benefit. Juice heater performance and the economic level of maceration can be derived from the data collected.

This list is on an Excel spreadsheet and a copy will be issued with the program Demo.


Production Cost Estimates; Factory Staffing Sheets and lists of consumables have been prepared. These sheets include the following:
• Factory staffing in crop and out of crop
• Consumables during crop
• Maintenance staffing out of crop
• Maintenance materials and factory spares
• Services
These lists are on Excel spreadsheets, and will be included with the SugarCost Demo.


Avoided Costs; It will be necessary to estimate any costs that should be avoided in any co generation studies. In particular these costs will relate to the existing O&M costs for the boiler plant, bagasse handling, ash disposal, and any other costs that can be identified as costs avoided by the replacement steam plant.

In the unlikely event that the existing plant is used, these costs will not be considered avoidable.

Other factory operations reviewed include

• Weekend shut down costs
• Lost time reports and operating Capacity Factor
• Sugar and molasses storage and shipment
• Overtime working
• Handling of mud, furnace ash, and surplus bagasse when necessary.
• Monitoring of effluent and operation of treatment facilities where applicable for high BOD and COD.
• Visual monitoring and rating of flue gases for particle emissions
• Out of crop maintenance, procurement of major items
• Materials and chemicals usage during crop
• Safety, fire protection etc
• Security of services, water etc.
• Fuel supply; diesel for onsite power generation during shutdown, and any requirement for start up.
• Performance audits.
• Cost ratios


 

     
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