30.-Reduction of water and steam consumption in cooking operations in the sugar industry (Part 1: Definition of operations)

Written by: Felipe Enrique Cieza Espinoza

The use of condensed water in the cooking operations in the sugar industry is carried out in the cooking of the cooked mass, which is crystallization of sucrose into a solid crystal called sugar. This cooking is carried out in equipment with an expansion chamber, a heating system and exposed to vacuum, called vacuum pans.

The condensed water comes from the condensed steam in the calenders of the evaporators in the sugarcane juice concentration stage in the multiple effect evaporation system. The condensed water is used in the different stages of the cooking operation. In the same way, the use of steam in the different stages of the cooking operation is shown below:

_ Thermal cleaning of the vacuum pan after unloading the mass to the crystallizer.

_ Loading and washing the crystal for granulation.

_ Loading and washing the sucrose source in liquid state.

_ Development of the size of the sugar crystal.

_ Drying of the cooked mass.

_ Discharge of the cooked mass to the crystallizer.

1.-Use of water in the cooking stages. - The water is used in cooking in the following:

_ To dilute substances that interfere with the adherence of liquid sucrose on the surface of the sugar crystal.

_ To hydrolyze the dough against any shortage of sucrose in liquid state due to an unforeseen failure and the dough does not dry out or burn due to the effect of heat.

1.1.-Water used to dilute substances that interfere with the adherence of liquid sucrose on the surface of the sugar crystal. -

To produce sugar the principle of the operation is the adherence of sucrose in liquid state on the surface of a crystal of sucrose in solid state. For which you need a source of sucrose in solid state (granulation crystal, magma B or magma C; depending on the cooking stage to be developed) and another source of sucrose in liquid state (granulation honey, syrup, honey A or honey B; depending on the stage of cooking to be developed).

1.1.1.-Dilution of crystals of smaller than average size. - Crystals smaller than the average crystal forming in a certain stage of cooking either A, B or C. The smaller crystals will gain sucrose that must go to the desired size and when centrifuged as they are smaller than the diameter of the pores of the centrifuge cloth will pass to the honeys, contributing to the increase in losses and therefore reducing the retention efficiencies from the exhaustion of cooked masses.

Condensed water is used to dilute the small crystals. Which for the evapo-crystallization of sucrose is necessary to evaporate.

1.1.1.1.-Possible sources of contributions of smaller crystals. - Smaller crystals come from three sources: broken centrifuge cloths, crystallized sugar at the bottom of honey storage tanks, and from using sugar crystals for granulation with high coefficients of variation.

1.1.2.-Dilution of gums present in the liquid sugary material. - The gums (dextrans) adhere to the surface of the sugar crystal and prevent the sucrose from being deposited in a liquid state, not allowing the crystal to grow.

1.1.2.1.-Possible sources of rubber contributions. - The gums (dextrans) come from the microbiological degradation of sucrose by the bacteria Leuconostoc Mesenteroides.

2.-Use of steam in the cooking stages. - Steam is used in the cooking stage in the following:

_ Thermal cleaning of the remnant of dough that remains adhered to the internal surface of the can under vacuum after unloading the dough.

_ Development of the size of the sugar crystal.

_ Drying of the cooked mass.

2.1.-Steam used in the thermal cleaning of the expansion chamber of the vacuum pan. - After unloading the cooked mass, it is the mixture of the solid crystal of the size of 0.3 mm, 0.5 mm or 0.85 mm as corresponds to the mass either C, B or A respectively and the honey in liquid state.

Internally, the pan in the expansion chamber has a pipe that injects steam directly to dilute the dough adhering to the internal surface and to carry out the next load of another batch of cooked dough. The steam pressure used will be different in each sugar factory, which can range from 125 psig, 75 psig, 50 psig, 20 psig, among other pressures. The steam injection time will also be different, generally it is in the range of 3 to 15 minutes.

2.2.-Steam used in the development of the crystal. - I will make a very brief explanation. The steam serves to keep the water present in the crystals for granulation, as in the sources of sucrose in liquid state, evaporating during cooking. The temperature governed by the contribution of steam to the calender of the vacuum pan directly infers on the viscosity of the sugar solution allowing the adherence of sucrose in liquid state on a solid glass until obtaining a final desired size as mentioned in item 2.1 .

2.3.-Steam used in drying the cooked dough. - After reaching the desired size described in item 2.1, the dough requires a solids concentration of 97%, 95% and 93% for cooked doughs C, B and A. To maximize the adherence of liquid sucrose on the crystals.

I hope this information has been useful to you. Awaiting your comments.

Greetings

Felipe Cieza