Sugar – starch – and carbohydrates – Processes – Carbohydrate manufacture and refining
Patent
1993-06-09
1996-02-20
Lieberman, Paul
Sugar, starch, and carbohydrates
Processes
Carbohydrate manufacture and refining
127 5, 127 65, C13D 112, C08B 3000
Patent
active
054925673
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and an apparatus for continuous heating of powdered starch. More specifically, the invention concerns a method and an apparatus for continuous preheating without simultaneous drying of powdered starch, used in the making of modified starch.
Starch is widely used as starting material in the making of modified starch by reaction with different reagents. Generally, powdered starch is first prepared from a raw material, such as cereal starch from maize, wheat, barley, rye, sorghum and rice, or root starch from potato, tapioca and arrowroot. The powdered starch is then modified by reaction with different reagents which may be gaseous, solid or, preferably, liquid. An example of starch modification is the making of cationic starch, used inter alia in the paper industry, by reacting powdered starch with a cationising reagent, e.g. 1-chlorine-2-hydroxypropyl trimethyl ammonium chloride.
To make the modification reaction proceed at a reasonable rate, the starch must have a temperature of about 30.degree.-45.degree. C., preferably about 35.degree.-40.degree. C. The starting material in the form of starch is, as a rule, kept in a silo where it is stored at ambient temperature, i.e. about 5.degree.-30.degree. C., and has a moisture content of about 19-21% by weight, preferably about 19.5-20.5% by weight. This means that the powdered starch normally has to be preheated before it is mixed with the modification reagent preparatory to the modification reaction. Preheating was formerly carried out with simultaneous drying of the powdered starch, since the modification reagent normally is a diluted aqueous solution. Drying was carried out in such a manner that the quantity of water dried up essentially corresponded to the quantity supplied with the reagent solution.
However, the introduction of new highly concentrated modification reagents has, on the whole, obviated the need for drying the powdered starch, and instead one wishes to preheat the powdered starch without any simultaneous drying. At the same time, rising energy prices and an increased environmental consciousness have led to demands for maximum utilisation of energy and elimination of discharges in the processes, i.e. that the processes be closed. Further, it is desirable that the process be continuous, contrary to prior-art batchwise processes.
The present invention aims at meeting these demands and providing a method and an apparatus for continuous heating of powdered starch, in which the starch is heated without drying, such that its moisture content is kept substantially constant.
The invention thus provides a method for continuous heating of powdered starch, which is characterised in that The powdered starch is fed through an inlet opening into a conduit where it is mixed with a hot air flow which heats the powdered starch and conveys it in the conduit, and that the powdered starch, when having reached the requisite temperature, is separated from the air, whereupon the separated air, after removal of any excess air, is reheated and recycled to the inlet opening of the conduit to form a substantially closed circuit.
The invention further provides an apparatus for continuous heating of powdered starch, which is characterised in that it comprises a substantially closed circuit which includes an inlet opening for powdered starch in a conduit for conveying powdered starch by means of a hot air flow; a device for separating the powdered starch from the air; a fan for feeding the air; optionally, a closable exhaust pipe for excess air; and a device for heating the air.
Further distinctive features and advantages of the invention appear from the following description and the appended claims.
According to the invention, the powdered starch is heated in a closed circuit with circulating hot air which heats the powdered starch to the desired temperature and at the same time pneumatically conveys the starch from its inlet in the circuit to its outlet.
In one embodiment of the invention, the powdered starch is fed into and out o
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Hailey Patricia L.
Lieberman Paul
Sveriges Starkelseproducenter Forening UPA
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