Title of Invention

A METHOD OF INHIBITING DEPOSITION OF CALCIUM OXALATE SCALE IN AN AQUEOUS ALCOHOL FERMENTATION STREAM CONTAINING CALCIUM AND OXALATE IONS

Abstract The present invention discloses a method of inhibiting the precipitation and deposition of calcium oxalate scale in an aqueous alcohol fermentation stream containing calcium and oxalate ions, comprising adding to said alcohol fermentation stream about 0.1 to 100 ppm lignosulfonate compound having a molecular weight of at least about 50,000 and about 0.1 to 100 ppm of a phosphate compound.
Full Text 1A FIELD OF INVENTION
The present invention relates to a method of inhibiting the precipitation and deposition of calcium oxalate scale in an aqueous alcohol fermentation stream containing calcium and oxalate ions. BACKGROUND OF THE INVENTION
Most commercial water contains alkaline earth metal cations, such as calcium, magnesium, etc. and anions such as carbonate and oxalate. When combinations of these anions and cations are present in concentrations which exceed the solubility of their reaction products, precipitates form until their product solubility concentrations are no longer exceeded. For example, when the concentrations of calcium ion and oxalate ion exceed the solubility of the calcium oxalate reaction product, a solid phase of calcium oxalate will form as a precipitate.
Solubility product concentrations are exceeded for various reasons, such as evaporation of the water phase, change in pH, pressure or temperature, and the introduction of additional ions which can form insoluble compounds with the ions already present in the solution. As these reaction products precipitate on the surfaces of a water carrying system, they form scale. Scale prevents effective heat transfer, interferes

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with fluid flow, facilitates corrosive processes, and harbors bacteria. Scale is an expensive problem in many industrial water systems, causing delays and shutdowns for cleaning and removal.
Calcium oxalate is a common substituent of scale forming on the metallic surfaces of apparatuses used for thermal treatment of aqueous solutions and suspensions. It is known that calcium oxalate scale can be removed by washing pipes, tubes, or other metallic surfaces upon which calcium oxalate deposits have formed with dilute aqueous acid solutions, such as hydrochloric acid or nitric acid solutions. However, due to the limited solubility of calcium oxalate in these acids, repeated washings of extended durations are necessary. Thus, acid washing constitutes a costly and time-consuming operation. Acid washing also deteriorates equipment.
Corn derived ethanol is a predominately aqueous stream (80-90% water) which is typically produced by continuous fermentation in which glucose is converted by yeast or other microorganisms into ethanol. The fermentation feed streams (including starch or glucose, light steepwater, dilution water, and fermentation backset) contain varying concentrations of calcium and oxalate ions. It. is the combination of these streams and the temperature/pH conditions in fermentation that result in calcium oxalate precipitation in the process. These crystals coalesce and form deposits on equipment, which reduce production efficiency and capacity. Extended shutdowns are typically needed to physically remove these deposits.

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DETAILED DESCRIPTION OF THE INVENTION
We have found that calcium oxalate scale may be adequately controlled by adding to the desired aqueous system an effective amount of a high molecular weight lignosulfonate compound and a phosphate compound. High molecular weight lignosulfonates from the sulphite process (Ufoxane 2, molecular weight 55,800. hereinafter lignosulfonate A, and Ultrazine Na, molecular weight 63,600, hereinafter lignosulfonate B, both available from Lignotech) have been found to be especially effective for purposes of the present invention.
Accordingly, the present invention provides a method of inhibiting the precipitation and deposition of calcium oxalate scale in an aqueous alcohol fermentation stream containing calcium and oxalate ions, comprising adding to said alcohol fermentation stream about 0.1 to 100 ppm lignosulfonate compound having a molecular weight of at least about 50,000 and about 0.1 to 100 ppm of a phosphate compound

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In a preferred embodiment of the present invention, a combination of from, about 0.1 to about 100 ppm of lignosulfonate compound and a hexamelaphosphate, based on one million parts of the aqueous system, is added to the system in need of treatment.
By high molecular weight lignosulfonate, It is meant a molecular weight of at least about 50,000. A molecular weight range of from about 55,000.- 65,000 is preferred.
The following concentration ranges may be employed:
lignosulfonate 0.1-100 ppm, preferably 50 ppm. phosphate 0.1 -100 ppm, preferably 50 ppm.
The lignosulfonate compound noted above was also found to effectively disperse calcium oxalate crystals which precipitate in an aqueous ethanol solution in the corn-to-ethanol production process, as described below.

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EXAMPLES
Two hindered settling tests were conducted in order to identify calcium oxalate dispersants, and then to evaluate the effect of pH on these dispersants.
The slurry synthesized for the tests contained 10% w/w calcium oxalate, 12% w/w ethanol and 2000 ppm phosphate. The high phosphate level was needed to match conditions in field process streams (1800 -2000 ppm). Note that despite this high concentration, field mineral deposits are composed entirely of calcium oxalate since, at a pH of 3.75, all phosphate exists as phosphoric acid and phosphate salt precipitation does not occur. However, such phosphate levels can affect the activity of dispersants by adsorbing onto the surface of the solids and either alter the surface cnarge or compete with the dispersant for. absorption sites.
Both tests involved adjusting the pH of the slurry to 3.75 and placing 50 ml aliquots of the slurry in 50 ml stoppered graduated cylinders. Treatment was added at a rate of 250 ppm active, the cylinders were stoppered, inverted and the contents allowed to settle. The height of the solids/liquid interface was recorded at regular intervals.
Additional steps for the second (pH dependency) test included measuring the pH of the slurries after the test was completed to determine if it was between 3.8 and 4.4. If the pH was outside this range, the pH of the treatment solution was adjusted to approximately 4.0 and the test repeated Experimental results are found in Tables I and II.

Table I Calcium Oxalate Batch Hindered Settling Tests 1
Conditions: 250 ppm Active Treatment 20 min. settling time 10%w/wCaC2O4 T = ambient pH = 3.75 2000 ppm phosphate
Height of Interface (mis)
Treatment t = 2 min t = 10 min t = 20 min
Control (avg. of 9 runs) 45.5 31.2 20.9
Lignosulfonates:
Polyfon(r) H2 50 45 37
Lignosulfonate A 50 43 37
Lignosulfonate B 50 42 34
1 pH not readjusted after addition of treatment
2 Kraft lignin, commercially available from Westvaco, molecular weight
7000

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Table II
Calcium Oxalate Batch Hindered Settling Tests1
Conditions: 250 ppm Active Treatment 20 min. settling time 10% w/wCaC2C4 T = ambient pH = 3.75 2000 ppm phosphate
Height of Interface (mis)
Treatment t = 2 min t = 10 min t = 20 min
Control (avg. of 17 runs) 45.5 31.2 20.1
Llgnosulfonates:
Polyfon H2 47 36 27
Lignosutfonate A 50 50 50
Lignosulfonate B 50 50 50
1 pH readjusted after addition of treatment
2 Kraft lignin, commercially available from Westvaco, molecular weight
7000
A treatment which yielded greater interface heights than the
control experiments was considered a calcium oxalate dispersant. The above tests indicated that the high molecular lignosulfonates effectively disperse calcium oxalate crystals independent of pH, whereas a low molecular weight Kraft lignosulfonate only exhibited calcium oxalate dispersant activity when the system pH was allowed to rise.

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Heat Exchanger Simulations
The chemical changes associated with fermentation of glucose to ethanol release heat energy in significant amounts per pound of alcohol produced. In order to reject this heat and control process temperatures, each fermentation vessel is typically fitted with a recirculation cooling loop. As the calcium oxalate fouls the equipment surfaces, the heat exchangers on these loops lose their ability to cool the process stream through both partial blockage to process flow and degradation of heat transfer efficiency.
In order to simulate cooler fouling, a once-through heat exchanger apparatus was designed. This apparatus consisted of a tube-in-tube heat exchanger with the process fluid passing inside the inner tube and cooling water passing through the outer tube. Two separate ethanol solutions were fed to the heat exchanger simultaneously, one of which contained 200 ppm of oxalate ion, with the other containing 40 ppm of calcium ion (concentrations are about twice those encountered in actual corn-to-ethanol processes). The exchanger was positioned for downflow service to avoid premature pluggage at the solution feed point inlet junction, which would prevent accumulation of deposits in the exchanger and mask the results of the anti-sealant testing.
The key parameter identifying the effect of the treatments is the hours on-line until pluggage. It was found that the calcium oxalate which formed as the two feed solutions passed through the apparatus would plate out on the inside of the inner tube, particularly around the discharge end of the inner tube. Eventually, the accumulation, at the discharge end of the tube totally blocked the flow of fluids. Testing demonstrated that

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certain treatments had a pronounced effect on the length of time that the apparatus remained operating until the exchanger plugged. The results of these tests are found in Table III.
Table III
Calcium Oxalate Inhibition Studies Heat Exchanger Experiments
Treatment Time to Plug. Hours (avq.)
25ppmSHMP 44
10ppmSHMP 57
5ppmSHMP 18
10 ppm Lignosulfonate A 7
5 ppm SHMP + 5 ppm Lignosulfonate A 23
5 ppm SHMP +5 ppm Lignosulfonate B 17
10 ppm SHMP + 5 ppm Lignosulfonate B 39
10 ppm SHMP + 10 ppm Lignosulfonate A 86
SHMP; Sodium hexametaphosphate
The above tests show the superior results achieved by combining individual components. A particularly preferred embodiment of the present invention (10 ppm SHMP + 10 ppm Lignosulfonate A) was found to be especially effective.
While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of the invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover alt such obvious forms and modifications which are within the true spirit and scope of the present invention.

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WE CLAIM:
1. A method of inhibiting the precipitation and deposition
of calcium oxalate scale in an aqueous alcohol fermentation
stream containing calcium and oxalate ions, comprising adding
to said alcohol fermentation stream about 0.1 to 100 ppm
lignosulfonate compound having a molecular weight of at least
about 50,000 and about 0.1 to 100 ppm of a phosphate compound
2. The method as claimed in claim 1, wherein the molecular
weight of said lignosulfonate compound is from 55,000 to
65,000.
3. A method as claimed in any of the preceding claims
wherein said phosphate compound is sodium hexametaphosphate.
4. A method of inhibiting the precipitation and deposition
of calcium oxalate scale in an aqueous alcohol fermentation
stream containing calcium and oxalate ions, substantially as
herein described, particularly with reference to the
foregoing examples.


Dated this 22nd day of January 1998.

(S. CHAKRABORTY) of D.P.AHUJA & CO APPLICANTS' AGENT
The present invention discloses a method of inhibiting the precipitation and deposition of calcium oxalate scale in an aqueous alcohol fermentation stream containing calcium and oxalate ions, comprising adding to said alcohol fermentation stream about 0.1 to 100 ppm lignosulfonate compound having a molecular weight of at least about 50,000 and about 0.1 to 100 ppm of a phosphate compound.

Documents:

00114-cal-1998-abstract.pdf

00114-cal-1998-assignment.pdf

00114-cal-1998-claims.pdf

00114-cal-1998-correspondence.pdf

00114-cal-1998-description(complete).pdf

00114-cal-1998-form-1.pdf

00114-cal-1998-form-2.pdf

00114-cal-1998-form-3.pdf

00114-cal-1998-form-5.pdf

00114-cal-1998-pa.pdf

00114-cal-1998-priority document.pdf

114-cal-1998-granted-abstract.pdf

114-cal-1998-granted-assignment.pdf

114-cal-1998-granted-claims.pdf

114-cal-1998-granted-correspondence.pdf

114-cal-1998-granted-description (complete).pdf

114-cal-1998-granted-examination report.pdf

114-cal-1998-granted-form 1.pdf

114-cal-1998-granted-form 2.pdf

114-cal-1998-granted-form 3.pdf

114-cal-1998-granted-form 5.pdf

114-cal-1998-granted-letter patent.pdf

114-cal-1998-granted-pa.pdf

114-cal-1998-granted-reply to examination report.pdf

114-cal-1998-granted-specification.pdf

114-cal-1998-granted-translated copy of priority document.pdf


Patent Number 194894
Indian Patent Application Number 114/CAL/1998
PG Journal Number 30/2009
Publication Date 24-Jul-2009
Grant Date 02-Sep-2005
Date of Filing 22-Jan-1998
Name of Patentee BETZDEARBORN INC
Applicant Address 4636,SOMERTON ROAD,TREVOSE,PA
Inventors:
# Inventor's Name Inventor's Address
1 WILLIAM J PALARDY 12 BRINKER DRIVE,CHALFONT,PA 18914
2 NANCY A DIANGELO 523 LACEBARK STREET, FEASTERVILLE, PA 19053
PCT International Classification Number C02F 5/14
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 08/801,272 1997-02-18 U.S.A.