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 todays 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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