US2391649A - Sugar refining - Google Patents

Description

Patented Dec. 25, 1945 SUGAR ammo Ralph W. Shai'or, New York, N. Y., assignor to The Dorr Company, a corporation of Delaware No Drawing. Application November 21, 1941, SerlalNo. 419,910

4 Claims. (on. 127-46) the raw sugar suspended impurities having ashyielding characteristics and especially colorimparting substances. So an object of this invention is to effect an increased yield of refined sugar per unit of raw sugar treated, and another object is to effect an improved quality of refined sugar that is substantially ash free.

In sugar refining, it is usually customary to make use of bleaching agents, followed by suspcnded-solids-separating steps, since the use of such agents ordinarily forms precipitates. Therefore, other objects of this invention are to reduce the quantity of bleaching and other related re-agents used and to eliminate certain costly operations necessitated by the use of bleaching agents.

A new process or" treating sugar-making juices has lately come into practice which comprises the removal of non-sugars or non-sucrose constituents by the use of organolites. An organolite is an ionic-exchanger granular material of organic nature. These are made use of by subjecting the juice sequentially to a bed of such organolite operating in the hydrogen cycle and another bed of such material operating in the hydroxyl cycle. The H-ion bed is a cation exchanger, while the OH-ion.bed is an anion exchanger. When exhausted or saturated with cations collected from the juice, the cation bed is regenerated with a strong mineral acid that discharges the collected cations from the bed and restores H-ions to the bed. The anion bed is regenerated with a strong base such as sodium hydroxide that discharges the collected anions from the bed and restores OH-ions to the bed. Besides removing ionic material from the juice, these beds also remove color-imparting constituents from the juice. Such organolite treatment is disclosed in patent application of F. N. Rawlings, Serial No. 376,717, filed January 31, 1941.

Another object of this invention, therefore, is to treat raw sugar produced by said organolite process with modified bleaching processes that meet the foregoing objects.

For an understanding of the environment of this invention, it may be stated that commercial raw sugar in being refined is usually treated by a method wherein the raw sugar is dissolved to produce a syrup, suspended solids are separated from the solution phase of such a syrup by filtration, the clarified syrup is then subjected to the action of an oxidizing bleaching or decolorizing agent, such as calcium hypochlorite, the resulting mixture is treated with an acid and a salt capable of adjusting the pH to a point optimum for bleaching efflciency and precipitating a large portion of the ash-forming constituents introduced as components of the bleaching reagents employed, the so-formed precipitate is separated from the bleached solution phase to produce a substantially clear syrup with a minimum of color, the oxidizing potentialities of any residual bleaching agent are neutralized, and finally refined sugar is crystallized from the treated syrup. The run-ofi syrup from the crystallization step is often used for washing, or amnating, the raw sugar to be refined, thus producing a washed raw sugar of higher purity.

By way of further explanation, it is obvious that when, as above outlined, the bleaching agent, calcium hypochlorite, is added to the syrup and the chlorine component thereof has affected the desired bleaching action, all components of said bleaching agent remain in the syrup as non-sugar impurities. This is undesirable because it reduces the amount of sugar which can be recovered in refined form from that syrup. Therefore, in past practice, it has been customary to employ a reagent, such as calcium acid phosphate, which will react with a portion of the bleaching agent components to form a precipitate, filter said precipitate from the syrup thereby eliminating a large portion of this undesired eifect.

The method herein set forth provides a means whereby the precipitation step of past practice may be eliminated.

So a further object of this invention is to modify the refining process to reduce the filtering operations to a minimum as well as to reduce the amount, of bleaching and other reagents used. A still further object is to make use of bleaching agents not heretofore usable. Also to make use of bleaching agents that produce no precipitate.

This invention may be said to revolve about a combination of certain chemical bleaching and certain ionic exchanger steps. One order of these gives on type of result, while another order gives a difierent result. One order can be used on one starting material, while another order can best be used on a different startin material. And, finally, depending upon the character desired of the end product, a different order may be used. By order is meant not only the sequence of bleaching and ionic exchanger treatment, but sequence of respective steps in each. Raw sugar referred to herein means raw sugar available in the sugar market today.

. A type of treatment is herein contemplated by this invention wherein the bleaching reagent is of a character that precipitation may be organolite treatment thus reducing the quantity part for the ash-precipitating reagents. The

syrup may have its pH adjusted with non-precipltating reagents such as HCl and NaOH to an optimum point for emcient bleaching with some non-precipitating hypochlorite bleaching reagent such as sodium hypochlorite or chlorine gas. Neutralization of residual hypochlorite or chlorinated products may be done with a, reducing reagent such as sodium hydrosuli'ite to leave the syrup free from strong oxidizing agents prior to subiecting the bleached syrup to sugar crystallizing operations. used on the syrup prior to its being bleached with bleaching reagents, or subsequent thereto or both. However, the raw sugar must be in the form of syrup before it is amenable to organolite treatment. Since thisis so, the process of this invention is usable on a syrup of melted raw sugar or a syrup of afllnated raw sugar (which means raw sugar mixed with run-off syrup from the crystallizer for thus raising the purity of the washed sugar).

The organolite treatment of syrup to be made use of in the practice of this invention has to do with beds that make use of granular ion exchange material that is of organic nature and is of that type now newly called organolites in distinction from the inorganic base exchangers heretofore known as zeolites. In extracting nonsugars and especially dissolved salts from sugar solutions or syrup. two main types of ion-exchange beds are used. One that is called the cation exchanger bed is characterized by its use of ionic exchanger material that operates on the hydrogen-ion cycle and is adapted to collect from the juice positively charged ions (called cations) represented generally by calcium, magnesium, sodium and potassium. That is, as syrup is supplied to the cation exchanger bed (or cell that contains the bed) so as to pass through it and out therefrom, cations'of dissolved salts of the juice exchange themselves for hydrogen ions of the exchanger until the exchanger bed becomes depleted of its exchange capacity and is so saturated with cations that it ceases substantially to exercise further exchange activity. Thereupon the cation bed must be regenerated by contact with a regenerant in the form of an ionized strong acid such as hydrochloric or sulphuric acids. During regeneration, the reverse equilibrium process takes place in the exchanger, namely, the cation taken up by the exchanger with hydrogen ions of the acid regenerant so that the cations flow from the bed until the bed is completely recharged with hydrogen ions.

Syrup that passes from the cation bed has had its impurity content of cations substantially removed and replaced by a molar equivalent of hydrogen ions, but it yet contains sulphates, chlorides and other such negative ionic impurities. So the juice substantially rid of its positive ionic or cation impurities that have been left behind. is contacted with an anion exchanger bed or cell that operates in the hydroxyl cycle. In passing The organolite treatment may be the bed until the anion bed becomes saturated with sulphates, chlorides and the like anions. Thereupon the saturated anion bed must be regenerated by contact with some ionized hydroxide or carbonate, especially sodium hydroxide or carbonate. During regeneration the reverse equilibrium process takes place, namely, the residual chloride and sulphate anions in the bed exchange with hydroxyl ions of the basic regenerant so that the collected negative ions or anions flow from the bed until the anion bed is recharged with hydroxyl ions. In passing through the anion bed. the syrup is substantially rid of its negative or acid-forming anions since they have been left in the exchanger. Thus, the basic or positive ions of the syrup are removed from it while passing through a cation exchanger bed and the negative or acid-forming ions are removed from it while passing through a subsequent anion exchanger bed. In other words, the cations of the salts are replaced by H-ions (in the hydrogen-ion cycle) while the anions of the salts are replaced by OH-ions (in the hydroxyl-ion cycle), with the net result that the salts are replaced with HOH (or H2O), that is the molar equivalent in pure and evaporable water. Other substanceaare also removed from the juice by this particular treatment. that surprisingly are non-ionic, such as colorimparting constituents and colloids.

These exchanger operating cycles (namely the hydrogen-ion cycle of the cation exchanger and 5 the hydroxyl-ion cycle of the anion exchanger) can be described in chemical nomenclature, and for the sake of simplicity and illustration, the removal of potassium chloride among other salts from the syrup will be taken as an example. The

a organic resinous cation exchanger o organolite is assumed to have taken up H-ion in the course of its previous regeneration. Upon contacting the syrup with the exchanger, the latter will exchange its H-ion for the potassium cation of the salt and form hydrochloric acid (HCl) according to the following equilibrium: Let :2: represent the organic structure or framework of the cation exchanger. Then:

(A) E+K++CP XK- l-H++Cl- The syrup according to Equation A is being acidified because of its reaction with the cation This represents that the exchanger is again ready for contacting with syrup, while the potassium compound is in the spent regeneration liquor. Other acids, such as H2804, I-INO: may be used instead of HCl for regeneration of the cation exchanger with corresponding results.

By contact of the syrup with the organic resinous anion exchanger or organolite containing replaceable hydroxyl groups, the anion of the acid (HCl) present in the syrup according to Equation i assume A istaken up by the exchanger in exchange for the OH-group, and the following equilibrium established: Let Y represent the organic structure or framework' of the anion exchanger. Then:

According to Equation C the juice is being deacidified as it is being freed from the acid that had previously formed in the cation exchanger according toEquation A. In this way the cation. as well as the anion of the salt constituting the impurity, are removed from the syrup and re-' It will be understood that instead of HCl, another suitable strong acid, for instance, H1804. may be used as a regenerant for the cation exchanger. In that instance sulfuric acid will reform as syrup is being treated by the cation exchanger. I

In the course of a complete operating cycle each of these exchangers, if exhausted, is to have the residual syrup therein displaced from the exchanger bed with wash water, and if deposits have collected on the exchanger granules they are to be washed out, before the exchanger i sub- ,iected to contact with the regenerant solution. Again, if regeneration is completed, the residual regenerant is to be displaced and washed out from the exchanger with water, before the exchanger is'again contacted with the syrup. In this way undesirable reactions in the exchanger bed can be avoided and the exchanger be kept in regular cyclic operation with substantially undiminished efllciency.

The exhaustion or saturation of a fresh exchanger bed with the solution flowing downtreat the more the cation'cxchang'erhed at temperature not in excess of 35' C. and it and 15 C. as a practical minimum temperature."

Forpracticing this invention, various orders and combinations of treatment steps will be described in the following examples, each complete and independent of the other:

r. The objective of the following combination resides in the avoidance of a precipitate being yielded in the syrup during the bleaching operation to the end that the bleached syrup may be treated fora second time by the exchanger process to eliminate the-ionizable materials intro-- duced into the syrup-by the addition of the bleaching agents both primary and secondary' This process is set forth in the following example:

The method of refining raw' sugar of substantially'96" or higher purity which comprises all!- nating raw sugar with a syrup having a purity lower than that of the sugar and having been 1 produced during a previous operation of this wardly therethrough proceeds in continuous fashion from the top to the bottom of the exchanger body. Hence there exists, approximately speaking, a dividing line or relatively narrow zone of transition between the upper exhausted or saturated portion of the exchanger body and the lower non-exhausted 0r non-saturated portion of that body. This dividing line or zone keeps shifting downwardly through the exchanger body as the continuously-through-fiowing solution leaves an increasing exhausted exchanger portion behind as it advances through a correspondingly decreasing portion of non-exhausted or still-ac tive exchanger. However, as the dividing line is not necessarily a sharp one, there will be noticed a slowing-down of the exchange intensity as the break through point of the exchanger is being The su ar solution or process, for the purpose of increasing the-purity of the sugar; melting the ai'finated sugar to produce an afllnated-sugarsyrum separating suspended solids from the solution phase of the afilnated-sugar syrup if there be present an amount suflicient to interfere with the subsequent operations; then subjecting the substan-. tially clear afllnated-sugar syrup at temperatures such as to avoid substantial inversion of sucrose to the action of an ionic-exchanger'material operating in the hydrogen cycle to remove cations and to the action of an ionic exchanger material operating in the hydroxyl cycle to remove anions from the syrup for the purposes of purifying and partially decolorizing the syrup to produce a substantially ion-free syr p; then treating the ion-free syrup with a reagent such as HCl suitable for adjusting the pH of the syrup to the optimum point of efficient bleaching with- ,out the formation of a precipitate and also with I the mixture, all to produce a bleached syrup;

then neutralizing under influence of mechanical agitation, the oxidizing potentialities of any hypochlorite and chlorinated products which may then remain in the bleached syrup with a suitable reagent so as to produce a syrup free from strong oxidizing agents; subjecting the bleached syrup to the action of said two types of ionic exchangers for a second time to remove the ions introduced during these final bleaching steps to produce a highly purified, ion-free, colorless syrup; subjecting the colorless syrup to crystallization by concentration procedure to produce successive crops of-crystals of refined sugar until such operations produce a syrup of such color and low purity unsuited to further production of such crystals; and returning said low-purity syrup to the afiination step of 'a subsequent operation to the process. 1

This method should result in a high yield of the highest quality of refined sugar that is totally ash-free and of the best color obtainable from a given raw sugar. The quantity of required bleaching agents is reduced to a minimum. By using bleaching agents which produce no pre-' cipitate, costly and tedious filtering operations are reduced to a minimum.

II. The following method has for its objective the elimination of the tedious filtration steps necessitated by using the precipitatable reagents employed in preceding method (see Example V).

The method of refining raw sugar of 96' or 1 higher purity which had been produced from melting the sugar to produce a substantially ion-1 free syrup, treating under the influence of mechanical agitation and preferably at temperatures between 25 and 50 C. such ion-free syrup with a reagent suitable for adjusting the pH of the syrup to the optimum point for efilcient bleaching without the formation of a precipitate, and with an aqueous solution of a non-precipitating hypochlorite suitable'for removing the coloring matter therein both without the introduction into the mixture of a precipitate; neutralizing the oxidizing characteristics of the excess hypochlorite and chlorinated products with a suitable reducing reagent so as to minimize their action during subsequent operations; separating suspended solids from the solution phase of said decolorized syrup if an amount be present sufilcient to interfere with subsequent operations; subjecting the substantially clear decolorized syrup at temperatures such as to avoid substantial inversion of sucrose to the action of an ionic-exchanger material operating in the hydrogen cycle to remove cations and t0 the action of an ionic exchanger material operating in the I hydroxyl cycle to remove anions from said syrup for the purposes of purifying same to produce a substantially colorless, ion-free syrup; and subiecting said colorless ion-free syrup tocrystallization by concentration procedure to produce successive crops of crystals of reflned sugar until such operations produce a syrup of such color and low purity unsuited to further production of such crystals.

With a normal consumption of bleaching reagents, a maximum yield of highest grade ashfree refined sugar will be obtained.

The bleaching or decolorizing agent should be used in a quantity depending upon the quantity of color constituents present and the degree of decolorization desired, of from one-eighth to one pound of active chlorine per thousand pounds of sugar melted. The syrup should be treated with the bleaching agent while preferably at room temperatures or between 25 and 50 C. and also under the influence of mechanical agitation. Agitation should also be used when the reducing agent is added to the syrup. The reducing or neutralizing agent that also should be non-precipitating, is preferably sodium hydrosulfite. Where the acid and salt is mentioned, monocalcium phosphate is preferred. And when a non-precipitating pI-I-adjusting agent is mentioned, hydrochloric acid or sodium hydroxide is preferred, as the case may be. When used, the temperature of the juice should be between substantia1ly'25 and 50 C. If filtration or defecationis made use of to remove precipitates from the syrup, it should be done with the temperature of the syrup not in excess of 70 C. And finally, the cation stage of the organolite treatment should preferably be carried out as heretofore explained, with the syrup at a temperature of substantially or less (down to say 15 C.) to discourage any substantially great inversion of sucrose of the syrup to glucose and the like inverts.

Exchangers of the type contemplated for use in connection with the present invention, are

substantially stable in the presence of acids and alkalis. g

The organic cation or base exchangers and organic acid or anion exchangers which may be used in this process include a variety of both.

Among the cation exchangers which may be used are:

1. Cation exchangers produced by the treatment of humic compounds with sulfur com-.

pounds which introduce acid sulfur groups into the humic substance so treated, such as treating lignite with concentrated sulfuric acid or equivalent. Materials of this class which have been stabilized by special treatment to prevent color throwing arealso applicable.

2. Cation exchangers produced by treating materials containing aromatic phenols. such as tannins, with sulfuric acid, petroleum acid sludge fuming sulfuric acid or equivalent agent which causes both the condensation of phenolic material and the introduction of acid sulfur groups to the condensed material.

3. Cation exchangers produced by the condensation of aromatic phenols with an aldehyde with or without the aid of catalysts.

4. Cation exchangers produced by the condensation of aromatic phenols with an aldehyde and with or without the aid of catalysts and into which acid sulfur groups have been introduced prior to, simultaneous with or subsequent to condensation.

5. The cation exchanger produced by the Resinous Products Co. of Philadelphia, under the name or identification of Amberlite IR. 1.

6. Cation exchanger of organic resinous nature as exemplified in the U. S patent to Holmes, No. 2,191,853, where the exchanger is described as a synthetic resin of the polyhydric phenol formaldehyde type which is sulphited to a degree such that its sulphur content is not less than 2.4%.

A variety of organic anion exchangers which may be used comprises:

1. Anion exchangers produced by the condensation of an aromatic amine with an aldehyde.

2. Anion exchangers produced by the condensation of a mixture of an aromatic amine and a mono or disaccharlde with an aldehyde.

3. Anion exchangers in which the active constituent is a basic dyestuif, such as the aniline blacks, which are insoluble in water and in aqueous acids and alkalls.

4. The anion exchanger produced by the Resinous Products Co. of Philadelphia, under the name or identification of Amberllte IRA.

5. Anion exchanger of organic resinous nature as exemplified in the U. S.'patent to Adams and Holmes, No. 2,151,883, describing the exchanger asan insoluble resinlike product .obtained by the reaction of formaldehyde with an aromatic amine.

I claim:

1. The process of refining raw sugar which comprises treating syrup of raw sugar with a hypochlorite bleaching agent of the non-precipitable kind whereby ash-forming ions are introduced in thesyrup, and subjecting the syrup to the action of a cation exchanger material operating in the hydrogen cycle and then to the action of an anion exchanger material operating in the hydroxyl cycle whereby said ash-forming ions are removed from the syrup.

2. The process according to claim 1, with the addition that in conjunction with the. bleaching treatment the syrup is treated with a pH adjust- 7; ing agent sufficient to establish optimum bleaching conditions, and then treated with a reducing substance to react with and thus offset the oxidizing effect of any excess of the bleaching agent; said exchange treatment being effective to remove from the syrup ionic matter introduced by said pH adjusting agent and said neutralizing agent.

3. The process according to claim 1, with the addition that the syrup after the bleaching treatment is treated with a substance to react with 10