IL37301A - Process and apparatus for the continuous manufacture of cooked starch pastes - Google Patents

Description

Process and apparatus for the continuous manufacture of cooked starch pastes RUBIN Willi Groag This relates to the continuous manufacture of cooked starch pastes for industrial purposes such for the sizing of paper or textile and the and in particular to the in situ manufacture of such The terra situ means the preparation of the starch paste at the place where it is to be used This is a modern since on the one liquid starch pastes lose their desired and on the other the manufacture of pastes and their subsequent drying for shipping is too In situ manufactured pastes need not be stocked but can at once be and the user can prepare at any time just the amount of paste required for immediate For the sake of reference will be made hereafter to in situ manufacture only but it is to be understood that the pastes manufactured by the process according to the invention can be stored and if for example Patents and According to a known starch paste is manufactured in situ by a continuous process in which an aqueous slurry of native starch is fed under pressure to a steam injection heater in which a temperature from is the heated mixture is and the cooking in a pressure converting zone at substantially the same and the converted starch paste is fed into a vessel at atmospheric While this process constitutes a progress over those conventional processes in which enzymes or chemical agents have been used for the degradation of the its results are still not In the viscosity of the starch pastes so prepared is it varies within wide limits without change of the process the pastes are lumpy and tend to retrograde and to The present invention aims at providing a process for the manufacture of cooked starch which also proceeds by cooking and subsequen flashing but produces improved According to the an aqueous starch continuously slurry is under pressure to a steam injection heater where a temperature in the range from is and the paste discharged the heater is to flashing in three successive stages by lowering the pressure first to a superatmospheric pressure somewhat below the pressure in the thereafter to a still lower superatmospheric and finally to atmospheric a pressure of at least 11 atmospheres gauge is maintained in the pressure in the first flashing stage may then be about 9 to 10 atmospheres and that at the second flashing stage about to 8 atmospheres The pressure prevailing in the heater is determined by both the temperature of the steam and the feeding pressure of the starch slurry and it can be regulated by controlling either or bot of the temperature of the paste being formed at the first flashing about the same or very li htl lower than that in the steam At the second 20 to At the last flashing the temperature need no longer be The preferred starting material for the process according to this invention is native cereal or potato but a starch may also be It seems that what happens in the course of the first and second flashing stages is granules the explosive evaporation of water within the starch granules whereby the grains are thoroughly Starch pastes produced by this process are immediately ready for possess a stable viscosity which depends on the concentration of the starch in the paste for a given can be varied in a controlled manner by variation of the process the pastes are highly homogeneous and neither gel nor It is an especial advantage of these starch pastes that even with a high content their viscosity is low and they are liquid and for at concentrations of to as required in the paper or 10 to as required by the textile viscosities 50 to 55 and 100 to 115 The process parameters determining the properties of the starch and in particular the are mainly the temperature and pressure in the steam the pressures at the first and second flashing stages and the retention the time between the entry of a given portion of paste into the steam heater and its flashing at atmospheric Higher temperatures and higher pressures in the steam heater make for lower viscosities and vice are of the order of 3 to 10 The retention is regulated by the rate of passage of the paste being formed through the e starch concentration of the final starch paste is determined by that of the initial starch It has been found that the amount of water lost as steam by flashing approximately equal to the of steaa in the process so that the contents in the final paste are approximately the same as in the initial By a preferred optional feature of the mineral adjuncts which conventionally added to pastes in the process of this added to the initial starch slurry and accompany the starch throughou the cooking It has been found that in this way the adjuncts are more uniformly distributed through the paste and remain so without Such adjuncts fo china clay or the The invention also provides an apparatus for carrying out the process aforesaid which comprises in combinatio a steam injection means for positively feeding starch slurry to the steam a first expansion chamber for the first flashing a second expansion in series with the for the second flashing and a flashing chamber for the third flashing the first expansion chamber is designed as jacketed tube preferably comprising a plurality of parallel tube sections of equal width connected in series by bends disposed at their starch paste being formed The second expansion may for in the form of a jacketed cylindrical vessel whose diameter is much wider than that of the single tubes of the first expansion In the meandering tubes of the first expansion chamber the flow of the paste being proceeds with so much friction that with a correctly calculated diameter and length of the tubes the desired pressure gradient between the heater and first expansion chamber adjusts In the second expansion chamber the pressure is apt to drop too It advisable to downstream of the second expansion a back pressure a throttle valve by whose manual or automatic operatio the flow of paste from the second expansion chamber can be so regulated that the desired pressure is maintained in the second expansion apparatus of be fitted with conventional accessories for leading and manually or the rate of flow of the starch slurry feed and of the steam as well as the pressures and temperatures in the various parts of the An apparatus according to the invention is diagrammatieally illustrated in the accompanying apparatus here illustrated comprises a slurrying tank 1 with water feed conduit staroh feeder 3 and mixer The tank is equipped with a indicater electrode connected to an optical signal At a level below the tank 1 feed tank 7 is is connected to tank 1 by a conduit conduit includes a and falls between feeler electrodes in order to renew sto supply of slurry to the tank A second solenoid valve with feeler electrodes is associated to tank 7 for the initial filling of the tank with water to the level of electrode or for flushing the tank at the end o a tank 7 is provided with a strainer 15 for retaining any coarse impurities carried by the feed of starc and with a mixer tank is connected to a steam injection heater 17 by a conduit 18 which includes a positive pump valve 20 and a regulating A recycle conduit 22 with valve 23 leads from the conduit 18 to the tank and a drain 24 with valve 25 is branched off from the conduit 18 for the evacuation o wash A pressure gauge 26 is fitted on the conduit The steaia injection heater 17 of a conventional conical rl It is fed with steaa through a feed pipe 27 includes a valve a regulating valve 29 and an automatic pressure regulator conduit 18 opens into the heater 17 at such an angle that the starch slurry feed impinges on the jet of steam substantiall at a right angle whereby the starch particles are subjected to In the heater the starch feed and steam mingle into uniform and this discharged through the narrow end of the heater into a pipe 31 which includes a regulating valve 32 and thermometer leads to the first expansion She supply of to the heater can thus be set to a predetermined pressure by the regulator and in addition be regulated means of the valve mainly in accordance with the indications read on the thermometer At the time the feed of starch slurry can be regulated by means of the valve and rate of discharge heater can be adjusted by means of valve he first expansion chamber includes a bundle of parallel tubes 34 of equal interconnected in series by bends a jacket with thermometer jacket is connected to a steam supply pipe 38 as may be branched off from the steam pipe with valve and to a drain pipe 40 with valve The second expansion chamber is a cylindrical vessel 42 enclosed in a jacket 43 which has a steam inlet 44 with valve and a drain 46 with condense trap The vessel 42 has a conical Outlet 42a where a thermometer 48 and pressure gauge 49 are The downstream end of the last tube 34 is connected to the upstream end of vessel 42 by a conduit 50 with valve and as illustrated the conduit 50 ends within the vessel 42 in a like distributor whose perforations are turned towards the head end of vessel so that the starch paste emerges in the form of a spray in direction opposite to the general direction of flow of the paste through the It has been found that this arrangement avoids the formation of dead near the walls of the vessel especially at the head where deposits of starch would otherwise be apt to The diameter of the vessel 42 is advantageously about 8 to 10 times the diameter of a tube 34 of the first exansion Shis sudden transition from a narrower to about 10 to about atmospheres A throttle valve disposed in the which is connected to the narrow end of the conical outlet 42a of the vessel enables the desired pressure to be maintained within the vessel The operation of the valve 53 may be manual or The conduit 54 leads the starch paste from vessel 42 to an upright conical vessel the where atmospheric pressure and the paste thus undergoes the third flashing The flashing chamber has at its top a steam vent 56 and is connected at its bottom to a discharge pipe 57 through which the stareh now ready for flows off into a collecting vessel The process to the invention can be carried for as follows Example 1 Starch and kaolin were slurried in so much that each liter of slurry contained 60 g of starch as dr and 30 g of The slurry was pumped continuously by a positive displacement pump under a pressure of 1 atmospheres into the steam injection heater to which steam was initially admitted under 11 atmospheres The further feed of steam was then so regulated as to maintain in the heater a temperature of The retention time was regulated to 5 the pressure in the expansion chamber was 10 atmospheres and in the second expansion chamber 6 atmospheres The starch paste thus produced had a viscosity of 55 When under otherwise equal conditions the retention time was lowered to 3 the viscosity of the was Example 2 The process was carried out as described Example 1 but the starch concentration in the initial slurry was per With a retention time of minutes the viscosity of the final paste s 110 5 retention time it was 80 and at 10 minutes it was ft The process was carried out as described in Bxample but the starch was diluted with water to content of whereby the viscosity values became the same as those of the paste produced in accordance with Bxample Cooking at higher concentration of the starch slurry has the advantage that higher t can be on th othe the process is slightly difficult to Example process was carried out as described Example except that in the heater a temperature of and a pressure above 12 atmospheres gauge were With retention times of and 10 minutes the viscosities of the products were 55 50 cp and 45 Bxample process was carried out as described in Example 1 but the pressure in the second expansion chamber was regulated to atmospheres in one and to 8 atmospheres in a second The viscosities of the pastes thus produced were slightly higher in the first run than they were in Example and slightly lower than in Bxample 1 in the insufficientOCRQuality

Claims (11)

CLAIMS continuous

1. A process for the/manufacture, preferably in situ, of a ready-for-use cooked starch parte, wherein an aqueous starch slurry is continuously fed under pressure to a steam injection heater where a temperature in the range from 175-200°C is maintained, and the paste discharged from the heater is subjected to flashing in three successive stages by lowering the pressure first to a superatmospheric pressure somewhat below the pressure in the heater, thereafter to a still lower superatmospheric pressure, and finally to atmospheric pressure.

2. A process according to Claim 1, wherein a pressure of at least 11 atmospheres gauge is maintained in the heater, of about 9 to 10 atmospheres gauge at the first flashing stage, and of about 6 to 8 atmospheres at the second flashing stage.

3. A process according to Claims 1 or 2, wherein the temperature of the paste being formed is, at the first flashing stage, about the same as, or very slightly lower than, that in the steam heater, and at the second flashing chamber the temperature is by about 20 to 30°C lower than at the first flashing stage.

4. A process according to Claims 1, 2 or 3» wherein native cereal or root starch is used as a starting material.

5. A process according to any one of Claims 1 to 4, wherein such mineral adjuncts, e.g. kaolin, china clay or the like, as the final starch paste is intended to contain, are admixed to the starch slurry used as a starting material.

6. A process for the continuous manufacture, preferably in situ, of a ready-for-use cooked starch paste, substantially

7. An apparatus for carrying out the process according to any one of Claims 1 to 6, comprising in combination: a steam injection heater; means for positively feeding starch slurry to the steam heater; a first expansion chamber for the first flashing stage; a second expansion chamber, in series with the former, for the second flashing stage; and a flashing chamber for the third flashing stage.

8. An apparatus according to Claim 7, wherein the first expansion chamber is designed as a jacketed tube system, preferably comprising a plurality of parallel tube sections of equal width connected in series by bends disposed at their ends, and the bundle of tube is disposed within a j cke designed for the circulation of a heating medium, e.g. steam.

9. An apparatus according to Claim 7 or 8, wherein the second expansion chamber is designed as a jacketed cylindrical vessel, preferably with conicaloutlet , and its diameter is much wider, e.g. 8 to 10 times, than the diameter of any one of the tubes of the first expansion chamber.

10. An apparatus according to Claim 9, wherein a conduit, connecting the discharge end of the first expansion chamber with the head end of the second expansion chamber, ends within the latter in a shower-head like distributor whose apertures are directed baek against the general direction of flow of the paste through the apparatus.

11. An apparatus for carrying out the process according to any one of Claims 1 to 6, substantially as described herein and illustrated in the drawing. For the Applic PARTNERS