Good news: national and international sugar prices continue at high levels. More recently, ethanol prices increased, although their economic equivalence related to the financial result of sugar production decreased.

Bad news: ethanol production does not keep pace with domestic consumption and may result in lack of product. Then, once again, producers will be called “irresponsible and greedy sugar millers”. Even Lula referred to them as heroes, only to have changed the adjective shortly thereafter.

Manufacturers of more than one product, whose objective is profit, use ERP systems to determine which item is more profitable and to set the production mix. It is an illusion to believe mills do not follow such a rule and utopistic to think they will produce sugar or ethanol taking only market demands into consideration. They must produce what optimizes their profit in the short and medium terms.

Once juice portion is defined to meet the production mix requirement, one must recover as much of its sucrose as possible, exhausting molasses  in a technical and economically feasible way. In fact, since the “Proálcool” program implementation, molasses is not exhausted  due to the allegation that its sugars are recovered by conversion to ethanol, which is false.

But, in those days, we wore blinds and strategy consisted in producing maximum volumes of ethanol even suffering higher sugar losses, because prices stated by “IAA” were based on a certain “economic parity”. With deregulation, that parity disappeared and mills started to face the real world, the one of supply and demand.

Let us compare two typical mills, both processing 80% of the juice for sugar using  two massecuite boiling systems, but one being quite conventional (SJM of 72%) the other optimal (SJM of 86%). Such recovery figures  are the result of operating with molasses with purities of 60 and 45%, respectively. For each ton of sugarcane, the conventional mill will produce 74 kg of VHP sugar and 41 liters of ethanol, whereas the optimized alternative will produce 89 kg of sugar and 32 liters of ethanol.
 
An expressive increase of 20% in sugar  production and on the other hand, a significant 22% ethanol decrease. Considering recent prices, there is no doubt that an optimized mill will profit more than a conventional one, notwithstanding higher sugar production costs.

How does one move from a conventional mill to an optimized one? And how to reduce molasses' purity from 60 to 45%? Following the basics and in the right way: simply boiling massecuites A and B at very different purities and adequately separating rich and poor molasses, an easy task for centrifugals, even the older ones.

The key aspect is to obtain relevant purity drop between massecuites and their molasses. Mills refer to the equipment under the vacuum pan as a crystallizer, but few can actually proceed that way, because they use it only as a buffer tank for centrifugals. Crystallizer is a piece of equipment that allows sucrose crystallization continuation after pan drop, keeping it in a supersaturation state, by cooling means and retention time.

Hence, the name. Very few mills cool  the massecuite. One should emphasize that ideal cooling and retention time for B massecuite require considerable operational volume and sometimes this is not possible due to space limitations in crystallizer area. In such cases, the ideal is to install vertical crystallizers that occupy an area of less than 5.0 m in diameter.

Such equipment allows massecuite cooling from 70 to 45ºC, using cooled water. Sucrose crystallization in crystallizers will allow further molasses exhaustion. Each point in molasses purity results in the increase of almost 1% of sugar and a reduction of 0.8% of ethanol. Since there is no free lunch, massecuite cooling increases its viscosity, significantly reducing continuous centrifugals' load.

To bypass this inconvenience, it is necessary to heat it to up to 53ºC, quickly and efficiently, so as to not invalidate the work performed by crystallizers. This heating is done with tubular heaters, also vertical and fed by gravity from vertical crystallizer, disregarding pump usage. B massecuite thus handled will allow centrifugals to operate normally and under ideal conditions.

This is how it is done throughout the world in plants, where final molasses is exhausted to achieve purities below 30%. Finally, whenever there is a need for expansion in the boiling section, it is interesting to analyze the option to elaborate B massecuite  in a continuous pan, with many advantages over batch pans, whether by using colder vapor, crystals uniformity, vapor consumption without sudden variations, or with better molasses exhaustion.

In Brazil, more continuous pans with horizontal tubes  were installed than vertical ones, although the latter are more adequate to operate for longer periods. This advantage derives from the typical geometry of continuous pans, since in the vertical type massecuite circulates inside 4” diameter tubes, whereas in horizontal ones this occurs outside 1½” diameter tubes, with 12 to 15 m in length.

After all, there are continuous pans with vertical tube with technology that allow to use three types of vapor in the modules (V1, V2 or V3), being also possible to install an additional module for future expansion. Shakespeare eternalized Hamlet with his dilemma “to be or not to be”.

Depending on the market, this unmerciful and unforgiving king, our adapted Shakespearian dilemma, is the decision to produce sugar or ethanol. Decision that can only be made by the mill’s management. But, let us agree that whatever the portion of juice for sugar production is, one should handle it carefully and completely, extracting the maximum from it, adopting basic well-known procedures, correctly and rigorously implemented, to obtain the lowest costs and the highest profits.