PLANT PROCESSES-Chlorophyll a correspondingly low chlorophyll content and requires more processing chemicals to remove undesirable plant materials. Shipment and storage of alfalfa must be carefully controlled as damp meal will mold, rendering it unfit either for extraction of chlorophyll or use as a livestock feed after processing. Susceptibility of carotene to oxidation by peroxidase and other enzymes limits the time meal may be stored prior to processing. Studies conducted by the United States Department of Agriculture indicate that up to 70% of the carotene present in dehydrated alfalfa meal may be lost during 5 months of storage in a nonrefrigerated warehouse (5). To prevent this carotene loss, American Chlorophyll normally does not stock meal longer than one month mior to extraction. and when possible maintains an even clos& buying schedule: Extracted meal may be stored indefinitely if moisture content is 7.0% or less. However when atmospheric conditions increase moisture content about 10 to 12% extracted meal cannot be stored safely longer than 3 or 4 weeks. An enclosed warehouse containing 4000 square feet of floor space provides storage for about 180 tons of alfalfa meal, either raw or extracted in varying proportions. Burlap bags containing 100 pounds of raw meal are unloaded from freight cars or trucks onto conveyors which carry them into the warehouse where they are removed and stacked by hand. The extractor battery consists of eight vertical cylindrical mild steel vessels of 1500-gallon capacity and two of 2000-gallon capacity, The two large vessels were installed during accelerated plant expansion. Differences in size of extractors does not affect processing. Solvent circulation lines permit operation of the battery as a series flow batch diffusion unit of four extractors or operation of any number of extractors in parallel flow Normally, a 24-hour schedule utilizes four vessels operating as a unit in series flow. The six other off-stream extractors are in various stages of cleanout and recharging. Each extractor requires about 2 hours for charging, is on stream for a 3-hour period, and goes off stream 5 hours for steam scavenging of solvent followed by cleanout. AE a newly charged extractor comes on stream the fourth extractor in the unit goes off. Lean solvent blend enters the extractor that has been on stream longest, then passes through the next to the last one charged, and finally through the latest extractor placed on stream. A solvent blend of 80 to 90% heaane with acetone thus contacts the meal in three extractors by series flow. Centrifugal pumps circulate the solvent blend a t 30 to 35 gallons per minute. Extract rich in chlorophyll and carotene goes from the last extractor charged through one of t n o leaf filters ($8)to the extract surge tank. To ensure a uniform chlorophyll concentration in the extract, a freshly charged extractor is filled with extract from the surge tank prior to placing it on stream. In normal series batch diffusion operations, 1500 gallons of extract and about 6000 gallons of hexane-acetone blend solvent contact the two-ton meal charge in each extractor. At Lake Worth about 90% of the recoverable chlorophyll and carotenoids are stripped from the meal during the first hour of extraction. Extractors remain on stream the additional 2 hours to strip the last 10% of these products because of the large amount of labor and time required for off-stream operations. Circulation pumps withdraw over two thirds of the extract from the meal in a vessel going off-stream. Scavenging steam, admitted a t the top of the extractor, forces remaining solvent from the meal cake to the solvent blend tank. Last traces of solvent and steam are condensed, and the solvent is recovered by gravity separation. When market conditions warrant, the Lake Worth plant may go on a curtailed operating schedule, producing 50 to 75 pounds of chlorophyll in an 8- or 10-hour day. At such times the extraction battery on stream consists of three 1500-gallon vessels each containing a 2-ton charge of alfalfa meal. After each vessel is charged it is almost filled with 1300 gallons of hexane-acetone solvent blend. Centrifugal pumps recirculate solvent through each extractor for one hour. +4rich extract is drawn off, and blend solvent is circulated through the three extractors in parallel flow for an additional 2 hours. When scheduling permits, the first extract containing about 0.65% chlorophyll by weight, as November 1954
Potassium hydroxide i s thoroughly blended with methanol in 2 mix tanks to mointain carefully controlled solution for saponification of chlorophyll extract
Outdoor construction o f extractor battery permits low cost construction and minimizes flre and explosion hazards from solvent leaks
Magnesium chlorophyllin i s converted to more stable copper form b y acidification and reaction with copper sulfate in mild steel tank battery
INDUSTRIAL AND ENGINEERING CHEMISTRY
2265
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT
Open stainless steel kettles are used for flrst chlorophyllin flnishing steps, saponification, and water washing, ensuring removal of water-soluble impurities
compared with a 0.4% extract from a series flow batch diffusion, will be finished as oil-soluble chlorophyll. Oil-soluble materials finished from the rich extract provide a uniformly high purity product. Lean extracts may be finished more economically through the eeveral processing and finishing steps required for chlorophyllins. A cycloidal gear pump forces extract from all extraction units through one of two leaf filters ( $ E ) to rpmove meal fines before extract enters the surge tank. TO further ensure that no meal passes into chlorophyll or chlorophyllin finishing steps, the 4000gallon cylindrical surge tank is elevated about 10 inches a t the discharge end. Operators make frequent inspections of sight glasses to detect possible presence of any meal fines. Cleanout of meal from evtractors consumes valuable time and labor, especially during continuous operations. Meal sets up into i~ hard, fibrous cake in the extractors, requiring a crew of four men 2 hours to empty the vessel. When market demands justify continuous production, time delays are directly costly Labor costs themselves also become an important factor. After digging cake out of vessels, large chunks of meal are broken mith axes and transferred to a hammer mill ( 8 E ) by a screw conveyor. -4pneumatic conveyor system ( 8 E )carries the ground meal from the hammer mill to the ivarehouse where it is recovered in a cyclone collector. Meal may be bagged in 85pound bags directly or may first be mixed with molasses and pelletized ( 8 E ) . Bags of extract,ed meal are ditched, tagged with proper anaiysie, and stacked t o await sale as livest,ock feed. Saponification, Coppering, and Finishing Produce Water-Soluble Chlorophyllins
Mixing batches of dry chlorophyllin in this double-cone blender yields a product that meets strict consumer speciflcotions
The hexane-acetone solvent blend extracts contain not only chlorophyll, carotene, and xanthophyll but also the undesired plant materials-Faxes, oils, steroids, and Epoidq. The first purification step in the processing of chlorophyllins (Figure 1) consists of saponifying the chlorophyll by contacting the extract with a methanolic-potassium hydroxide solution. This solution is about one half saturated or 15 t o 25% potassium hydroxide by weight. bIethanolic-potassium hydroxide accomplishes virtually complete saponification of chloropliyll and retards formation of an emulsion with plant matter Chlorophyll is thereby converted t o a water-soluble form called sodium-potassium magnesium chlorophyllin in trade terminology. Actually the chlorophyllin produced is predominantly the tripotassium salt, however a very small percentage of sodium ion picked u p in the processing opeiation originally gave rise to the nomenclature now used by the trade. The following reaction occurs:
",C.iH
From these nozzles at top of spray dryer tower a chiorcphyllin fog quickly becomes potassium capper chlorophyllin powder-Lake Worth's main product
2266
",C.C"
I phytyl group and a methyl group are rcplaced with potassium, and the carbocyclic ring is opened! yielding phytol and methanol. The water-soluble chlorophyllin may then be separated from carotenoids and other unsaponified plant matter by water washing and gravity settling. Potassium hydroxide and methanol are mixed in two 750gallon vertical mixing tanks and injected into the extract feed line just ahead of the saponification tank. Extract and metha-
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
Vol. 46, No. 11
PLANT PROCESSES-Chlorophyll nolic-potassium hydroxide come into intimate contact in the vertical saponification mixer. The mixture enters tangentially near the bottom of a 250-gallon vertical mixer. Five propellers, driven from a central shaft by a 3-hp. explosionproof motor mounted atop the tank, move the liquor upward through the mixer around four side-wall baffles. Effluent from the saponification mixer consists of an intimately mixed two phase system. Hexane contains the bulk of the carotenoids, waxes, and unsaponified plant matter; chlorophyllins are carried by the acetone-methanol-water phase. Flow rate of t'he mixture passing through the saponification tank is governed by colorimetric assay of chlorophyll in the extract. Samples are taken every half hour; resu1t)s are made available to the operator within 5 minutes. Mixed effluent from the saponification step is pumped to the first, of three settlers. Each of these vert,ical cylindrical tanks has a capacity of 1600 gallons. About 90% of the potassium magnesium chlorophyllin solution settles as the bottom layer in the first settler. At 4hour int,ervals, this solution is drawn off and pumped to thc 2500-gallon chlorophyllin surge t,ank. The top hexane lager passes on to the second settler for water washing to separatx the remaining 10% of chlorophyllin. Operators draw off the bottom chlorophyllin layer from the second settler da,ily. The yellow hexane top layer containing carotenoids passes through the third settler, which serves only as a check on the efficiency of the saponification step. I n normal operations the sight glass on the third settler will contain yellow hexane. However, if saponification of chlorophyll has not been complete, the glass may contain a green solution. Should green solution appear, the saponification process is shut, down, and troubles are determined and corrected prior to further processing. -2 centrifugal pump nioves carotenoid extract from the third settler to the .iMH)-gallon yellow hexane surge tank. A vertical long tube natural circulation evaporator ( I E ) ,fed from this surge tank, recovers hexane a.nd concentrates carotenoid extract for carotene and xant,hophyll finishing steps. To ensure removal of all carotenoids from the chlorophyllin phase, the solut,ion from the chlorophyllin surge tank is washed batchwise with a 90 t,o 95% hexane-acetone blend in a 3300gallon mild steel tank. Volume of the batch washed depends on the concentration of chlorophyllin; a typical charge containing 3% chlorophyllin by n-eight would be about 4150 pounds or 500 gallons of solution. Following 30 minutes of washing with agitation, steam is introduced directly into the vessel raising the temperature of the washed mixture to about 104" F., the optimum temperat'ure for separating the carotenoid phase from the chlorophyllin. Hexane containing carotenoids is then drawn off the top and sent to yellow hexane surge. Chlorophyllin solution goes to a steam-jacketed still for complete removal of solvent,. Hexane is recovered, some as an azeotrope with acetone or methanol, and returned to solvent storage tanks. DisMlation must be controlled carefully as the chlorophyllin solut'ion foams highly when hexane has been removed. At first appearance of foam the operator cuts off steam, and the chlorophyllin solution is pumped to an acidification vessel.
Addition of acid reduces the pH of the solution stepwise to 1.5. After agitation, the acidified mixture stands until the acidcopper chlorophyllin rises to the top of the vessel as a t,hick mke. This cake carries varying quantities of coagulated waxes, sterols, and other undesired mat'ter. Low solubility of the copper-acid chlorophyllin in either a hexane-acetone solvent or in water permits removal of oil- and water-soluble impurities by washing. Acid water discharged from the bottom of the acidification vessels goes to a waste sump, from which it is fed into the plant's 80,000-gallon-per-hour condenser water discharge, thus preventing pollution of the Palm Beach Canal adjacent to the plant site. A wash of 90 to 95% hexane-acetone removes the waxes, sterols, and other oil-soluble impurities from the cake. Agitation continues for 30 minutes after addit#ion of solvent. Following removal of oil-soluble matter, the copper-acid chlorophyllin precipitates during a 4-hour settling period. Solvent is then drawn off the top and pumped to the green hexane surge tanlc for hexane recovery by a vertical long tube natural circulation evaporator ( I E ) . Solvent washings may be repeated to ensure purity. Chlor.ophyllins produced from a good grade of alfalfa normally need only one washing; however, those from poorer grades (150,000.units of vitamin A or less per pound) may require two or three washings to remove all undesired plant mat,ter. Khen the precipitate reaches a purity exceeding SO'%, it is pumped to a 1000-gallon jacketed still for evaporation of t.raceE of solvent, prior to finishing. Chlorophyllin slurry from the still goes to a 250-gallon st'ainless steel steam jacketed kettle in the finishing room. Kater washing removes traces of water-soluble impurities from the insoluble copper-acid chlorophyllin. After a few minutcs of mixing, agitation is stopped and the chlorophyllin floc flouts to the top; water is drawn off and washing is repeated three or four times, During washings the slurry becomes nearly neutral. To reconvert the chlorophyllin into its water-soluble form, the slurry is saponified with a solution of potassium hydroxide. Concentration of chlorophyllin in solution determines the amount of potassium hydroxide required to complete saponification. During the following saponification, pH of the chlorophyllin solution increases to about 11.5:
KOH
+iE
Cr
~ O Q K
bo&
Filtration of the saponified chlorophyllin solution through a centrifuge (6E)removes trace quantities of plant waxes. The operator adjusts concentration of the filtrate to 10 t o 15% solids by dilution with water. Potassium-copper chlorophyllin solution is then pumped to a 250-gallon stainless steel holding tank in the spray dryer building. Clarified aqueous solutions of
Naturally occurring magnesium chlorophylls or potassium magnesium chlorophyllins do not possess the high tinctorial strength and light stability desired in commercial derivatives. Substitution of other metals for the magnesium atom in the chlorophyllin molecule takes place in the acidification and comering H.C.CH _ _ - vessels by tjhe two step reaction. --f By carefully controlled acidification, two hydrogen atoms replace the magncsium; reaction with copper sulfate solution introduces the copper atom into the center of the chlorophyllin molecule. The solution in the acidification vessel is assayed for chlorophyllin content and then diluted with water. Agitation during addition of copper sulfate solution mixes the charge thoroughly. Pyior to addition of acid, the mixture has a pH of about 10. Acidification is carried out using 37.574 hydroCOOK chloric acid diluted with about an equal volume POTASSIUM-MAGNESIUM CHLOROPHYLLIN of water.
November 1954
CQOH
COOH
ACID CHLOROPHYLLIN
I N D U S T R I AL AND E N G I N E E R I N G C H E M I S T R Y
ACIO-COPPER CHLOROPHYLLIN
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