US2442471A - System for handling massecuite - Google Patents

Description

June i948. E. ROBERTS SYSTEM FOR HANDLING MASSECUITE FiledV March 27, 1945 ATTORNEYS many charges.

Patented June l, 1948 SYSTEM FR HANDLING MASSECUITE Eugene Roberts, Hastings, N. Y., assigner to The Western States Machine Company, Hamilton, Ohio, a corporation of Utah Application March 27, 1943, serial No. 480,790

4 Claims. l

.This invention relates to installations for the treatment of sugar massecuite in sugar factories at the Stage of crystallization and crystal recovery, and particularly to improvements in methods and apparatus for handling pan boilings or strikes of massecuite between the vacuum pans where the massecuite is formed and centrifugal machines where the crystal recovery is carried fout.

White massecuites and similar free-purging sugar mixtures are centrifuged as soon as practicable after being prepared, but a batch of 1000 `to 3000 cubic feet usually is formed by each pan boiling, and it takes an hour or two to centrifuge :such a strike. The boiled strike usually is passed from the vacuum pan through a trough into an repen-top tank, called the mixen which holds vthe massecuite awaiting treatment and from which charges are drawn ff, as needed, through jloading gates on spouts at the tank bottom for treatment in underlying centrifugal machines.

Meanwhile another strike is boiled in the same vacuum pan,

It is desirable that every charge from each `'strike be centrifuged in the same way, and that :uniform sugar and syrup products of the best attainable qualities be produced from all of the The practices used heretofore,

however, fall short of this objective. In many linstallations some of the charges delivered from the mixer are more difficult to purge, wash and fdry in the centrifugals than others, and these :reduce operating efficiency and make the sugar :and syrup products non-uniform. Also, the imassecuite sometimes is difficult to load into a slowly rotating centrifugal basket and tends to r'form a sugar Wall too thick at the basket bottom, 'which delays operations and results in off-grade jproducts.

Troubles of these kinds are particularly noticeable in the treatment of higher purity l:or white massecuites, which, with the use of comparatively recent massecuite conditioning and centrifuging processes, are boiled at higher temperatures and to higher density than was the practice a few years ago.

The object of my p'resent invention is to provide new and useful improvements in the methvods and equipment used to handle strikes or runs of sugar massecuite which will overcome or greatply reduce those diiiiculties and non-uniformities still encountered with existing sugar house prac- .'tices and thus enable the sugar of each strike to albe recovered with optimum efficiency by the opteration of centrifugal machines.

TI have found that the troubles above-mentioned are largely attributable to the presence of false grain or smear in charges of massecuite as delivered from the mixer into the centrifugal machines, and that this false grain is the result, not of poor boiling operations in the vacuum pan but of chilling influences which affect portions of the massecuite between the time of dropping the strike from the pan and the completion of the centrifugal operations. High purity white massecuite, for example, can be boiled carefully to a density of to 90 Brix with line crystals of relatively uniform size substantially free from false grain, but as the massecuite passes from the pan into the mixer some of it is chilled by the ambient air, and when the mass enters the mixer a considerable amount of it is chilled by contact with the internal mixer parts. Further, as the centrifuging progresses, the massecuite undergoes rapid local heat losses to the airthrough the mixer Walls, from the surface of the mass and from continually exposed parts of the stirring mechanisms now generally used in the upper portion of the mixer to cooperate with heating and stirring means in the bottom and keep the mixer contents in circulation, .These chilling effects are especially noticeable under cold weather conditions. Though the general temperature changes they cause may be small, or may be nulliied by the action of massecuite heating means, they nevertheless cause smear formation and debase the purging qualities of any centrifugal charges containing the smear or false grain. When false grain has thus formed it is not affected by the action of massecuite stirring and heating means, but remains as an uncontrollable contaminant that is removed, if at all, only at the expense of excessive waste and costs in the centrifugal operations.

According to the present invention, I provide a new method and new apparatus for Carrying out the same that eliminate the formation of false grain and other obstructions to efcient sugar recovery by overcoming the chilling influences and other irregularities which heretofore have affected each strike after the boiling of the strike in the vacuum pan, and which I have found to be Vthe main cause of false grain formation and the resulting troubles described above.

I prevent cooling shocks and attendant false grain formation in the massecuite after it leaves conveying each boiled strike directly from the pan into such heated mixer; and I prevent localized chilling in the massecuite held in the mixer awaiting centrifugal treatment, and keep the entire contents of the mixer uniformly subject to such slow heat exchanges as may be allowed or causedto take place during the centrifuging, by "covering the mixer structure so as to keep its contents completely enclosed against the access of outside air and insulating the structure, over substantially all its external or heatradiant surfaces, against chilling heat Vlosses from the mixer contents to the ambient air. In addi tion, I preferably drop each strike 'directly from the pan into the preheated 'mixer tank through a downcomer which joins or seals together the two units and excludes the outside air from any chilling contact with the flowing massecuite. Thus, the mixer is made as an attachment or auxiliary to the vacuum pan, and the temperature andheat exchange conditionsr throughout the mass in the mixer are established and maintained in a definite predetermined relationship to the condition of the same mass as it was prepared in the pan. l 4 y The heating of the mixer interior to condition it for receiving a strike may be carried out in various ways. Asuitable procedure is to steam the mixer interior. In a suitable embodiment of apparatus for that purpose I provide one or more steam pipes which open to the linside of` the mixer structure, and where the mixer tank is equipped with conventional types of loading spouts a steam pipe preferably is extended through each loading spout Wall. In such Van embodiment steam is introduced into the mixer for a -few minutes after the completion ofgthe centrifuging of one strike and just Vbefore `the-dropping of the next strike Ainto ithe-mixer, 'and the steaming is continued until the mixer interior has been heated at least toabout the nal boiling temperature used in the ivacuumfpan.

When thepreheated condition ofthe vmixer is thus established by steaming,-severalimportant results and advantages may be obtained. The most Yimportant isfthe elimination of cooling shocks and false grain formation inkthe massecuite 4received for centrifugal treatment. VA11'- other is that the 'steaming emoves'such sugary material as 4may adhere "to internal walls orn parts of the mixer'after the centrifugin'g'of a strike, by renderingthe adhering -material fluid-through the combined action ofheatand condensation. The resulting fluid material maybe drawn off through the-loading-gates 'in the course of the steaming, at'a -very substantial saving of grain melt or dilution heretofore caused bylthe Washing down of mixer parts with water between strikes. A third functionis that the steaming exerts a sterilizi'ng'eifect on allofthe internal mixed parts 'and thus relieves the problem of bacterial contamination.

Toalter an existing'fa-ctory installation 'pursuant hereto, the'usual mixer tank is tted with a cover completelyenclosing its interior with the exception ofanop'ening through which to admit massecuite vinto the tank, and thisopening issurrounde'd by a v'dovvncomer directly"con necting and sealing the rmixer structure withthe bottom of an overlyingvacuumpan. The heatradiant' surfaces of' the' mixer structure' jare suitably insulated against:substantiallossesff heat therethroughffromthe massecuite, such as #by overlay/ing; the mixer side, "endl and b'ottom'walls and also the covenwithlayers *ofy heat-insulating sheet material, or by forming the walls as jackets to hold a suitable insulating or heated fluid.v When a steaming operation is to be used for preheating, one or more steam pipes are extended through the mixer Walls, preferably with a pipe at the lower side of each loading spout. In addition, the mixer is provided with suitable stirring and heating means to maintain the massecuite awaiting centrifugal treatment in continuous circulation and regulate the temperature of the successive charges delivered to the adjacent centrifugal machines. These means, for example, may

` disclosed in United States Pat- '20,556, 2,086,951, 2,128,873 and be ofthe types ents# Nos. Re. 2,206,237. n I

I also have found it advantageous to construct the mixer itself se as to prevent any substantial dormant portions or pockets of massecuite from existing Yin the mixer. When using conventional structures some of the massecuite lies relatively dormant in parts of the mixer, such as in the spouts extending between 4the tank proper Aand the 1oading gates, and 4also in the lower corners of the tank in many fcases. Under these conditions 'the vsugar crystals in `a -hot massecuite of high purity tend to segregate lor s-ettle from lthe syrup, andthe resulting non-uniform crystal and syrup distribution causes trouble in 'the loading of the centrifugal machines. I may overcome this trouble, for example, by making the loading spouts exceedingly short with their loading gates disposed closely adjacent to the bottom ofthe tank proper, s'o ythat a continuous forced 'circulation'ofheatedmassecuite Ais-maintained by-heatingand stirring means in 'the Atank bottom, substantially up tothe inside faces of the loading gates. If needed, I valso provide fillets in 'the cornersofthe'tank'to prese'nt'curve'd or streamlined I inside v'surfaces Tfor 'eflici'ent massecuite 4circulation. All'massecuite inthe mixer thus vmay be kept ineffectiveiforced c'ir'culation'and subject uniformly to anyfphysicalichanges'that may occur or be caused to take place. Tosecure lthe same effect in conventional 'mixer insi',alla'tions having long igoosenecks or loading spouts, l modilied forms of --construction'may be used, such as disclosed in 'my cor-'pending lapplication, -Serial No. 480,789, filedt of f even date 'herewith fnoWPatent No. 411,138.

The 'foregoing and -other' objects, "features and advantages 'of my vinvention `will become :more apparent from the vfollowing description .of 'an illustrative er'nloodlrnent thereof when considered in Tconne'c'tion `with' 'the Vv'aecernpanying drawings, wherein Figure 1 isafront elevation, '-partlyin section, showing diagrammatically 1 one form fof fa sugar recovery installation lembodying my invention;

fFigure 2 is "an fend elevation, fpa'rtly Tin -sectionf taken substantially-alongline2-2 'ofi-Figure 1; and

Figure 3f is anenlarged fragmentary cross section through `anlupper 'corner Tof vthe lmixeratank showing f illustrative details of construction.

In the drawings I have fmu'strated a sugar recovery station vofia -typeidesi'gned for thef handling an'd treatment lof 'White or 'other freepurging massecuitethatis tobeidropped' directly froma vacuum-pan r11 into-1a mixer-'Bi and! tobe held'byV the inxer ina desiredx physical condition during vthe :processi-ng "of the massecuite charge by lcharge in' underlying sugar centrifugals C. The mixer structre includes"anelongatedtarik body 2 which is usuallyUishapedlimcross-section; togetherY with'a" plurality` of" loading 'gates 4 5, of any desired construction which are connected with the bottom of the tank through very short spouts 6 so that the inside faces of the loading gates are closely adjacent to the zone of action of rotary heating and stirring means lil disposed lengthwise in the bottom .of the tank. rIhe means ii, as shown, comprise spiral coils l2 mounted on a rotary shaft lli, together with provisions (not shown) for circulating hot water or other suitable heating fluid at a regulated temperature through the rotating coils, as disclosed, for example, in the aforesaid Patent Re. 20,556.

Above these heating and stirring coils are rotary stirring means l which also extend substantially the full length of the tank in its up-f per portion and coact with the means l to keep the main body of massecuite held in the tank in continuous circulation. The stirring means It comprise paddles or blades il mounted on radial arms i8 for rotation with a shaft i9, which may be driven from a source (not shown) common to the heating and stirring means l0. The depicted arrangement of heating and stirring devices is similar to that disclosed in my afore. said Patent 2,127,873.

The mixer tank 2, as shown, is fitted with a cover 2i) which extends across the entire top of the tank and may be provided, if desired, with hinged doors, such as shown at 2i and 22, permitting access to the interior of the tank. An opening 2d in this cover affords passage for the entrance of massacuite into the mixer when a strike is dropped, in the usual manner, from the vacuum pan A at the completion of a pan boiling. Opening 2t, however, is surrounded by a downcomer 25, shown diagrammatically in Figures l and 2 and of any desired construction,- which connects and seals the mixer structure directly with the bottom of the vacuum pan so that a strike being dropped from the pan passesI as quickly as practicable into the mixer and is excluded altogether from contact by the ambient air.

The heat-radiant end, side and bottom Walls of the tank 2 and the cover 20 are all formed with one or more layers of heat-insulating material, or with other suitable heat-insulating means, to prevent objectionable losses of heat from the mixer interior both before and during the processing of a strike. An illustrative manner of insulation is depicted in Figure 3. The wall of tank 2, for example, is overlaid by asbestos-magnesia blocks Sil, which may be fastened to the wall by means of anchors 3| and wire netting 32 overlying the blocks. The netting in turn may be coated with one( or more layers of insulating plaster, such as indicated at 33. The cover also might be so constructed, but is shown as comprising one or more layers 35 of wooden board coated on the outside with an asphaltic paint or the like, at 36, and over-A laid on the underside by one or more layers of a suitable insulating board, such as asbestos board 31. With this or other equivalent heat insulation and with the cover 2G completely enclosing the mixer against the access of outside air, a structure is obtained which undergoes heat losses only at an exceedingly slow rate, so that the interior of the mixer can be kept heated in readiness to receive a strike of massecuite from the panV A, such as by the means described below, andso that cooling of massecuite in the mixer cannot take place at a rate suflicient to chill local portions of the massecuite and cause objectionable false grain to form.

At the lower portion of the mixer one or more steam pipes are provided which extend through the mixer wall so as to introduce steam to the interior when desired. As shown, pipes 40 open intothe bottom of the mixer at the opposite end Walls and the center of the tank, and similar pipes 40a open into the bottoms of the spouts 6 (Figure 2). By these or equivalent means a large volume of steam may be admitted into the mixer at the end of the centrifuging of a strike, With the results of pre-heating the interior in readiness to receive the next strike and of removing any sugar crusts remaining on the mixer walls or the stirrer parts from the previous strike, as described hereinabove. In the course of thesteaming the loading gates i may be held partly open so that the fluid material, produced from such crusts by the steaming will drain out of the spouts 6 for such further disposal as may be desired to recover its sugar content.

With the improvements herein set forth I am able to achieve several important advantages and savings in sugar factory practices: r

The massecuite temperature can be regulated very closely without trouble from local cooling, local overheating, or the formation of false grain.

Each strike dropped from the pan may be held throughout almost exactly at the final pan temperature and consistency, yet if desired the temperature of the massecuite may be allowed or caused to fall gradually a few degrees, without; trouble from cooling shocks or smear, so as to, cause a substantial and uniform growth or accretion of existing sugar crystals.

The presence of false grain in centrifugal charges is substantially eliminated, provided only that the massecuite has been properly boiled in the vacuum pan.

The formation of crusts on the internal mixer parts is almostrentirely eliminated, whereas this continued to be a substantial source of crystal loss in prior practice. The practice of washing the crusts away with large quantities of water at the end of each strike and the costs and compli` cations attending that practice are substantially eliminated.

The elimination of false grain and the improved control over the purgng qualities of centrifugal charges permit more uniform and better centrifugal operations, with lowered Wash water, requirements and with increased yield due both to the reduced washing and to accretions of crystals in the mixer while awaiting treatment.

The temperature of water circulated through the heating coils to maintain a desired purging condition may be substantially lowered, at a save ing of heat and elimination of grain melt formerly caused in some cases by excessive water temperatures.

A further aspect of practical merit is that the improved system reduces the temperature of the air around the mixer and the centrifugal machines and thus contributes materially to the comfort of centrifugal operators, especially under warm or hot weather conditions.

It will be apparent to those skilled in the art that my invention may be embodied in various forms of apparatus without restriction to the details of construction set forth hereinabove, and I therefore desire that the invention be accorded a scope commensurate with its contributions to the art, as intended to be set forth in the ap pended claims.

I claim:

1. The method of handling 'strikes of purity sugar massecuite to be processedir'r centrifugal machines Y'which comprises dropping ali boiled strike directly from the vaciiil p ht' a mixer tank pre-heated throu'gloit-it's interior' toat least approximately the' tempeateofthe boiled' strike, keeping the interior of the mixe'i completely enclosed against accessfo'f ambient air' and protecting thev mixer against any substantialrate ofheat lossA to the ambient air from air'f' its contents dunne the centrifdig of the strike; and at the end of4 the' centrifu'gin'g introducing steam into the mixer to reheat' its interior toV at least the final' pan boiling temperature" lsfo dropping the next strike.-

2. The method of handlingl strikes' of- Iiifipirity sugar masseouite to be processed centri'fii-A gal machines which comprises dropping eachboledstrike directly from the vacuum pan into a preeheate'd mixer, keeping the interior of the-A mixer completely enclosed' against access' of amlbient air and protecting the mixer against any substantial rate of heat loss to' the: ambientair from any of its contents diiuring th'- centrifug'ii'g of the strike, at the endofthe centiflig'ing introducing steam into themixer tol reheatl its in: ter'ior at least to about the iinal panV boilngf'te'niperature before dropping the next strike, and in the' course of the steaming draining from the mixer a fluid mixture of' crystals and syrup's' formed' by the steaming from sugary material adhering to' internal mixer'paits.

3f. In a massee'uite treating instauati-ori'f-of niet purity massecuite susceptiblet'o false" grain for?" mation, comprising a vacuum prr anda tank therebelow to receive and liold'` stik'e'sv of'mas's'ecuite delivered successivelyv from the"V pan for direct centrifugal treatment, means incliidng a" cover over the top of the tank com'pletielgftoV enclose' the tank contents', an enclosedVv downcomer connecting and"l sealing the pani bottomH wim 'said temi tp etntey astrike from the par; intthe tank through opening in said cover, means formed with thev Wallys of the tank to pr`e' vent chilling heat" lossesv frommasscuite held in the tank, and at least one steam pipe opening into the` tank to introduce steam thereinto be-v tween the endpofeentrifuging of 'one strike and tnefrec'ept'ion of another;

4. A." mixer to' receive and hold high piltv sugar masseeuite susceptible to false grain for: mation while the massecuite is drawn off charge by' chargeA` for centrifugal treatment, comprising an elongated tank having loading spout's atth'e bottom Withl gates at their en'ds t'o d'elivr charges of massecuite into adjacent centrifuga mac'l'iines;aJ cover closing the topV of the tank ex cept fdr an opening 'enclosed bye'. dwncomer through' Which' to receive mase'c'uite i'e'aiyfor treatment, heat-insulating sheet i'atrial aiie'd totiie'wans' of said tank and spout's and also' to' said' evr, and' means to introduce steam in t the` mein-uitg aste'affjf pipe extending through; the wall of each loa'dingspo'ut.

EUGENE ROBERTS.

REFERENCES CITED 'Phefollowing referencesI are' of record in the le'of this: patent:

uNfTDl STA-ras` PAir'tiii'rs1

Images