Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
`` ` 2~532~.
Field Of The Invention
This invention relates to a thermosetting resin and a method
¦ of utilizing such resin to bind particulate matter into strong and
water resistant agglomerates or shapes.
Background Of The Invention
The damage resulting from acid deposition on the land,
vegegation and surface waters downwind from coal-burning facilities
is a matter of increasing international concern. Although flue-gas
clean-up technology and limits on the sulfur content of coal have, to
some extent, ameliorated the rate of deterioration there is still a
priority need to further reduce acid-precursor emmissions,
particularly the oxides of sulfur.
' ~'
The most prevalent form of sulfur existing in coal
formations, ironpyrite, can be substantially reduced by grinding the
coal to liberate the mechanically-bound pyritic and mineral-ash
inclusions, and then separating the heavier particles of pyrite and
ash. This procedure permits the utilization of lessexpensivegrades
of coal with initially-higher levels of sulfur and is, therefore~
gaining wider industry recognition. To maximize the removal of
impurities, grinding often proceeds until the particle size has been
2~ reduced to where lO0 percent will pass through a No.20 (850 micron)
mesh screen and at least 50 percent will pass a No.200 (75 micron)
screen. Particulate in this general size range is designated as
ultrafine and, although much cleaner burning, its utilization
presents many new problems, not the least of which are transport~
3(1 handling and increased water retention. Formerly, a large portion of
fine coal - material inadvertantly pulverized to a size small enough
'' '~
,, ~
to pass a No.14 (1400 micron) screen - was largely discarded as
unmarketable.
Newer facilities can be designed around ormodiEied to accept
this form of fuel, but many older and less sophisticated types of
installations inherently cannot accommodate ultrafine, or even fine,
coal; stoker-fired industrial boilers are one such class. The
obvious remedy is the reconstitution or agglomeration of fines into
pellets or compacts of a size and shape compatible with existing
handling and combustion equipment. An efficient means of
reconstitution would also provide the economic incentive needed for
the reclamation oE the substantial quantities of fine coal previously
abandoned.
The reconstituted product must be very durable and resist
disintegration during handling, particularly after prolonged
weathering, and it must yield a minimum amount of ash and no noxious
substances as a result of combustion.
Industrial agglomeration methodology is a well defined art
that abounds with examples of technically efficacious systems for
binding a variety of fines into discrete shapes. The economic
realities of the current coal and energy markets~ however, have
effectively precluded the adoption of these techniques on a
commercial scale by the coal industry. Even those binder
formulations expressly developed for coal agglomeration are too
costly by industry standards of profitability. The manufacturing
methodology and equipment exist and are employed in other mineral
processing industries; conspicuously absent is a binding agent that
is at once functionally effective, simply prepared and processed, and
yet composed of virtually valueless ingredients.
~'
~0~32~L
Carbohydrate-rich dairy waste such as cheese whey would be
among the most promising raw materials, were it notfor theirpresumed
solubility when employed in an orthodox binder formula-tion. Only a
small fraction of the 40 million liquid tonsof whey produced annually
in North America is marketed as dried whole whey; the remainder does
not have a sizeable commercial use. Lack of an efficient and
acceptable means for disposing of this vast amount of material,
coupled with increasingly stringent environmental regulations, has
caused serious ecomonic dislocations within the U.S. dairy industry.
The burden of compliance with environmental standards has
been alleviated,to a modest extent, by the sequential derivation of
new food ingredients from whey. The ultrafiltration of whole whey
L5 yields a retentate product, whey protein concentrate (WPC), and a
liquid, whey permeate. The subsequent fractionation of whey
permeate yields crystalline lactose as a product and another liquid,
deproteinized lactose permeate (DLP). A residual liquid permeate
remains, therefore, whether only one or both saleable products are
withdrawn from whole whey. The permeate from either process is not
only as difficult to dispose of as the original whey, but it is only
partially reduced in volume; derivative products are primarily a
means for mitigation of disposal costs.
',
The invention disclosed herein describes the methodology
developed to transform not only whey and its permeates, but other milk
products as well, into a resin intermediate that is convertible
directly, or by design at some later time, into a thermoset and
insoluble particulate binder. The class of lactose and protein
containing milk derivatives employable as raw materials in this
invention includes not only the dairy wastes, whey, permeate and DLP,
~ .
i32~
but milk byproducts with established market values , e.g., skim milk
and WPC.
The physicochemical properties of milk byproducts, and
S derivatives such as whey, have been intensively studied, primarily
with a view toward either preventing product deterioration or
developing new food uses. As a consequence of this focus on food uses
the reactive nature of these materials under extreme treatment
conditions, as well as the properties of the resulting reaction
products, has largely been overlooked and their full potential as
chemical feedstocks neglected.
The solids content of whey is in the range of 6-7%, with
lactose and protein comprising approximately 70~ and 13~,
L5 respectively. Lactose is a disaccharide reducing sugar consisting
of one moiety each of D-glucose and D-galactose, occuring
predominantly in the pyranose ring form and joined by a glycosidic
linkage. Chemical reactions of lactose involve the glycosidic
linkage between rings, the hydroxyl groups, the -C-C bonds within the
rings and, of speoial importance to this invention, the hemiacetal
linkage between carbons 1 and 5 of the glucose moiety. This
` ~ hemiàcetal structure gives rise to an equilibrium between the two
anomers, alpha and beta, which differ in steric configuration of the
-OH and -El at glucose C-l.
The anomers aredistinguished by theirmelting-decomposition
points; alpha at 202C and beta at 252C. The two anomers also differ
in specific optical rotation and solubility, with the ratio of alpha
to beta, as well as the rate of mutarotation between the anomers,
affected significantly by changes in temperature or pH. Lactose is
known to be particularly sensitive to ammonia;anentire solution will
~O~i3~ ~
mutarotate to equilibrium spontaneously upon addition of a trace
amount of ammonia. The dynamic equilibrium between the anomers in
solution involves opening and closing of the hemiacetal ring of
glucose, and at any time a small amount of the free aldehyde is
S present. This small amount can unclergo the reactions typical of
glucose alde~hyde and, the entire amount of lactose in a system can ;
enter a reaction by being channeled through the aldehyde in this
manner. ~
~'
That portion of the original protein that remains in whey,
after the casein proteins of milk are coagulated to form cheese, is
fundamentally different from casein protein and is separately
classified as whey or serum protein. It is comprised mainly of ;~
globular proteins that, unlike casein proteins, can be unraveled or
L5 denatured by heat, or by p~adjustmentto a level below 4or above about
. Denaturation exposes numerous reactive amino acid residues, ~;~
including the e-aminO group of lysine. A small, but significant,
fraction of this whey protein survives in each permeate after the ~
removal of whey protein concentrate or a portion of the lactose. ; -
Commercially available dry forms of whey, whey permeate and
delactosed whey permeate contain whey serum protein on a specified
minimum weight percent basis of 12%, 2% and 5%, respectively, in
combination with at least 50% by weight lactose.
Although glucose-containing reducing sugars and lysine-
containing denaturable proteinsare found in numerous substances, the
physical state and condition in which theycoincidentlyoccurasdairy
wastes in such abundance makes them singularly advantageous raw
materials for this resin. Specifically, the minimum necessary
concentration of solid reactants are each present, to the virtual
exclusion of extraneous organics, in the requisite aqueous
.
32~
....
dispersion.
Characteristically, aqueous solutions of reducing sugars in
the presence of amino compounds undergo the early or colorless stage
of the Maillard reaction, which requires a low order of energy for
initiation and exhibits autocatalytic qualities once it has started.
In the text, Dairy Chemistry and Physics, published by John Wiley &
Sons, N.Y~, 1984, the authors, Walstra and Jenness, state in item
12., page 165, "Maillard reactions occur at any temperature but
proceed much more rapidly at higher ones", and on page 177, section
10.4.1., Chemistry of Maillard Reactions, they further comment that
l'The primary reaction in Maillard browning is condensation of an amino
compound with the carbonyl group of a sugar in the open chain form,
presumably to form a Schiff base although such a compound is not
isolatable. Il This initial condensation is accompanied by the
formation of water.
The initial reaction product undergoes an Amadori
rearrangement with the formation of a N-substituted l-amino-l-deoxy-
2-ketose, these are colorless compounds, which when heated, proceed
in a series of reactions that lead eventually to the formation of
polymers called melanoidins. Typically brown compounds of variable
structure and solubility, melanoidins have unsaturated heterocyclic
rings which account for their florescence. From studies of
simplified aqueous sugar-protein systems, melanoidins have been
shown to contain significant amounts of a glucose-ammonia component
and are strongly bound to protein.
The decomposition of lactose in the earliest stage of the
Maillard reaction is base-catalyzed by amino compounds, with the
permanent loss of lysine from these compounds a measurable index of
2~ 3~
lactose reactivity. AS the Maillard reaction proceeds galactose has
been shown to accumulate while glucose does not, indicating that
glucose is the moiety of lactose that reacts predominantly with
lysine. The extent of decomposition is governed by the buffer
capacity of the medium and the pH, with strong buffering slowing the
shift to acid conditions. The basicitydecreasesdramatically if the
dispersion is heated as the reaction progresses. The production of
organic acids, mainly formic, increases rapidly during the reaction
(in the presence of oxygen at temperatures above 100C) and the
resultant drop in pH from above 6 to 5 or below arrests the reaction.
The routine Maillard reaction in milk products is, therefore, self-
inhibiting and ceases after a light to moderate browning of the
product.
L5 It is known from nutritional studies that many chemical
reactions thatoccur in sugars only at high temperatures take place at
much lower temperatures once they have reacted with amino acids.
This characteristic, however,has notbeen heretofore exploited under
conditions of an ammonia-induced alkaline pH to produce industrially
use~ul materials from sugar-protein containing dispersions.
In accordance with the practice of this invention, ammonia
added to such a system at the outset is believed to behave initially as
a basic catalyst, promoting protein denaturation and increasing the
reactivity of the amino acid residues and the rearrangement and
fragmentation of lactose. Later, at elevated temperatures, the
ammoniated system is believed to counteract acid formation and
promote the formation of melanoidins. Many aspects of the Maillard
reaction sequence in milk derived products are incompletely defined,
including the possible catalytic role of the numerous salts that
become increasingly concentrated as derivative products are
~ 0~32~ 71458-8~
~,
.' .
sequentially withdrawn.
The complexity of Maillard reactions and the multi-
tude of products yielded is illustrated in the work reported
by Aldo Ferretti et al in the Journal of Agricultural Chemi-
stry, Vol 18, 1970, and Vol 19, 1971, wherein the 80 vola-
tile compounds that were isolated and identified from model
lactose-casein browning systems that had been conditioned
for eight days at 80C are enumerated.
. ~ :
Summary of the Invention
.
A first aspect of the invention provides a method
,
of preparing a thermosettable resin intermediate for binding -
agglomerated particulate matter into useful products which -
comprises adjusting the pH of an aqueous dispersion of a
glucose-containing reducing sugar and a denaturable lysine- ;;
containing protein to a pH level between 7 and 14 by addlng
an ammoniating agent to said dispersion to obtain a resin
intermediate prior to admixing with the particulate matter.
A second aspect of the invention provides as a
composition of matter an aqueous dispersion of a thermo-
settable resin intermediate prepared in accordance with the
method.
A third aspect of the invention provides a process
of preparing agglomerated products from particulate matter
and a thermosettable resin comprising the steps of:
a) admixing to said particulate matter an aqueous dis-
persion of a thermosettable resin intermediate prepared in -~
accordance with the method described above to form a thick
and viscid admixture, ~ ~
, ...
- 8 - ~
3;;~
71458 8
!i b) shaping said admix-ture into formed green agglomerates
by employing a suitable means for agglomerate forming, and
c) drying said formed green agglomerates to fix said
particulate matter in coherent and strong shaped products.
A fourth aspect of the invention provides an ~
agglomerated product prepared by the process mentioned im- ~ ¦
mediately above. The agglomerated product may be an artifi-
cial fuel in which the particulate material is coal fines.
A fifth aspect of the invention provides a thermo-
setting resin composition prepared by adjusting the pH of a ~ -
dispersion of a glucose-containing reducing sugar and a de-
naturable lysine-containing protein with an amount of ammonia
sufficient to raise the pH level to between 7 and 14 to ob-
taln a resin intermediate and then heating said intermediate `~ I
to a temperature in the range of 190C to ~60C until said
resin intermediate polymerizes into a thermoset resin. ` ~
,::.' ' ,. :'. ' '
.,.';- ':', .~:, ,':'
.: ., ,, ., ,~
,. . . .
.: :
- 8a -
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The elaborate physical changes and chemical reactions that
accompany the ammoniation of a lactose-protein dispersion, i.e., the
predisposition of lactose to spontaneous mutarotation, the
denaturation of the whey proteins, and the resulting condensation of
S the newly accessible amino acid compounds with a constantly
replenishable supply of glucose aldehydes~ produce a stable resin
intermediate. The intermediate thus prepared shows evidence of
having undergone the early stage(s) of the Maillard reaction and is in
a condition to proceed, when sufficiently heated, along an optimized
advanced stage Maillard reaction pathway to a terminal polymeric
compound that is infusible, insoluble and black.
An insoluble polymer is not produced from a dispersion that
has been alkalized with a base material other than ammonia, or iE
either the lactose or the protein is not present in the dispersion.
The specificity of ammonia in combination with lactose and the
protein compounds, together with its ability to participate in the
formation of the melanoidins, is apparently fundamental to this high
temperature, resin forming, Maillard reaction. The term ammonia as
used herein is intended to include not only ammonium hydroxide as
cited in the examples below, but the other common forms of the
compdund: anhydrous ammonia and ammonia gas.
When used as an ingredient in a resin intermediate dispersion
no distinction as to origin is necessary between sweet and acid whey,
or as to the physical form of the derivative raw materials; liquids,
concentrates and dry powders that are the standard product forms in
the milk processing industry all perform equally well and, when
adjusted for water and whey protein content, are considered
interchangeable. The shelf-life of the liquid forms of the resin
intermediate is extended indefinitely if the dairy raw material is
32~
pastuerized prior to ammoniation, or the liquid intermediate is
stored at a temperature of 5C or below. A dry reconstitutable powder
form of the intermediate can be obtained from the aqueous dispersion
by conventional water removal means such as spray-drying or
5 evaporation.
The fully polymerized intermediate has been found to be
useful as a durable and insoluble binder for sand, mineral ores, metal
powders and other finely divided materials, in addition to coal fines.
Prior Art
: ,''.;,
The effectiveness of the disclosed thermosetting resin as a
binder of agglomerated particulate matter is an intrinsic property of
15 the combination of lactose and whey protein in aqueous dispersion when
it is ammoniated to an alkaline pH and then heated to an elevated
temperature; it does not require special crosslinking additives or a
cooperative chemical reaction with the material being bonded.
Indeed, the resin intermediate disclosed will completely polymerize
20 in the absence of any additional material to a black and insoluble
solid under the application of sufficient heat. It is, therefore,
readi'ly distinguished from compositions that utilize carbohydrates
in combination with such special additives, or wherein the material to
be bound participates in a reaction with the carbohydrates.
In the Gibbons U.S. Patents Nos. 4,085,075 & 4,085,076 and
Viswanathan et al U.S. Patent No. 4,524,164 the resin binder
formulations, in addition to a sugar or starch ingredient,
incorporate a urea, phenol, formaldehde or like polyfunctional
30 crosslinking additive to contribute to the desired properties of
strength and water resistance in a bonded or molded lignoce]lulose
2~ 32~.
:
product. The above Viswanathan process additionally specifies a
preferred acidic pH level of from 3 up to 7.
Those carbohydrate containing resin binders prepared in
accordance with Stofko U.S. Patent Nos. 4,107,379 & 4,183,997 and
Viswanathan et al U.S. Patent No. 4,692,478, rather than including a
crosslinking additive, are all in acidic aqueous solution (pH 2 to 5)
when they are combined at high temperature (140 - 225C)and pressure
with the lignocellulosics. These are the classic conditions
required for initiating the mild acid-catalyzed hydrolysis of
cellulosics which is known to yield, among other reaction products,
pentose and hexose sugars, furfural and hydroxy-methyl-furfural,
together with organic acids such as formic and acetic. These latter
acid products augment the cellulose hydrolysis and degradation
reactions, thereby producing additional furan compounds that bond
with the ligneous structure at newly exposed sites. This type of
auto-catalyzed hydrolysis of lignocellulosics is also the underlying
reaction evident in the Stofko U.S.Patent No. 4,357,1~4 wherein
pressurized live steam is utilized to induce organic acid production
and carbohydrate degradation leading to pressurized sugar-furan-
lignin bonding.
Resins that rely for their effectiveness, even in part, on
hydrolysis or other conjunctive reactions with the material to be
bonded are inherently inferior as binders of non-reactantsubstances,
e.g. coal fines, sand or mineral ores.
Each of the above cited patents includes, as a necessary
ingredient, a sugar, a starch or a mixture thereof; none require that
for functionality the carbohydrate be present specifically in
combination with a protein. This combination of constituents is
~ ,. ,~,.
32~
indispensable to the instant invention and is one of its most
conclusively distinguishing features.
;:
In the article Utilization of Whey/Lactose as an Industrial
Binder, published in the Journal of Food Chemistry, Vol.27, No.4,
1979, Arthur Ferretti and James V. Chambers presented the results of
binder development work demonstrating the suitablility oE whey and
lactose as alternative and economic substitutes for molasses, the
preferred carbohydrate in C.W. Humphrey's U.S. Patents Nos.
10 3,567,811, 3,765,920 & 3,857,715. These patents, as well as the
work reported in the referenced article, do not have as an objective a
finished product wherein weather resistance and durability are
properties specifically imparted by the carbohydrate binder. The
Eunction of the binder ineach instance is to impartgreen or temporary
lS strength during an interim period of handling, drying or, as in the
case of portland cement products, natural hydration. Products
prepared by the methods of the first two patents in the series, iron
ore pellets and bloated fly ash aggregate, require post-drying
induration at drastically high temperatures (1000-~C) before they
acquire a permanent ceramic or oxide type interparticle bond. Until
this bonding is effected, the particulate matter is merely held
together by the carmelized carbohydrate and is immediately soluble in
water. Substitution of whey in these processes does not utilize to
advantage the potential contribution of the protein constituent and,
therefore, provides no additional benefit, other than economic.
Representative of recentinnovations in the art of coal fines
reconstitution is W.W. Wen's U.S.Patent No. 4,615,712 which utilizes
a humic acid based binder in an agglomeration process that is
functionally analogous to the technique disclosed herein. Because
of this similarity in the mechanics of agglomerate formation and
12
`. 2~0~;32~
treatment, the binder preparation and curing procedure of Wen is an
appropriate example with which to compare the merits of the resin
binder that is the subject of this invention.
To prepare the Wen binder, which is characterized as an
aqueous solution of the humates extracted from oxidized carbonaceous
material, very low rank coal is pulverized and oxidized by chemicalor
heatmeans (unless it occurs ina naturally oxidized state), extracted
by alkaline solution at an elevated temperature and then separated
from the undissolved residue. Subsequent to agglomeration by
conventional means, the product must be cured for about 2 hours at
160C before the humate binder provides the minimum necessary impact
strength and water resistance.
By contrast~ preparation of the intermediate form of the
composition of the present invention requires only the adjustment of
the water content of the dispersion of dairy waste solids and then
ammoniation of thatdispersion to the appropriate level of pH prior to
agglomeration. Polymerization of the resin intermediate is effected
by drying the agglomerate to remove virtually all free moisture and
then heating it to about 190C for the short interval needed to obtain
a durable and water resistant product. There are no protracted high
temperature chemical reactions involved in preparation of the resin
intermediate or undesireable residual materials, and process time is
minimized by a short and straightforward drying and curing procedure.
''`,'",
The Preferred Embodiment -
Powdered whey permeate is utilized in this descriptlon as
representative of that class of milk-based derivatives that all
13
200~
contain lactose and whey serum protein. Permea-te is a nominal
representative of the materials in the class as it contains, on
average, the smallestweightpercentage of whey protein solids and is,
therefore the least effective. To realize a given concentration of
protein (as ina binder formulation) permeate solids are required in a
commensurately larger quantity than any other material of the class.
A widely employed agglomeration technique that is especially
well suited to exhibiting the advantages of this resin involves
balling dispersion-wetted coal Eines on a rotating inclined disc.
Experimental pelletizing trials on a laboratory scale rotating disc
are particularly useful in defining the binder and process parameters
as results are directly translateable to large capacity industrial
equipmentO rrhe disc pelletizing procedure that yields superior
quality spherical balls agglomerated from an admixture of ultrafine
coal and a dispersion of the resin intermediate can be divided, for
illustration, into three distinct operations:
1. preparation of the ammoniated aqueous binderdispersion;
2. admixing the dispersion with coal fines and forming
green balls on a laboratory disc pelletizer; and
3. drying and induration of the balls.
1. BINDER PREPARATION
,
Dry permeate powder typically contains between two and ten ;
percent whey protein solids, and it is the quantity of this reactant
that governs the eventual strength of the interparticle bonds, and
ultimately the physical properties of the pellet.
Lactose, in excess of the stoichemetric quantity needed to
combine with the whey protein in the Maillard reaction, progressively
14
32~.
decomposes to ash during curing. In terms of this reaction, lactose
is always present in permeate (and all the materials of the class) in
superabundance (typically 50 - 95~ of the solids) and, therefore no
special precautions are necessary regarding its quantification.
Close control over moisture content is critical to effective
disc pelletizing. When the moisture content is insufficient all the
coal surfaces are not wetted, capillarity is not created and air
inclusions result. Excessive moisture will coat the external ball
surface and neutralize the capillary forces, thereby reducing pellet
green strength by more than fifty percent. Engineering reference
data indicates an appropriate moisture range of 20.8 - 22.1~ for disc
balling of coal fines that all pass a No. 48 (300 microns x 0) mesh
sieve.
- ::
1 5 ~; :',.
Subsequent to curing residual polymerized resin, in the form
of interparticle bridges, provides pellet hardness and compressive ;-``
strength. The magnitude of these features and, to some extent,
pellet integrity after water immersion is a direct function of the
quantity of whey protein in the resin dispersion.
~ .:, ,,
For dry permeate containing about four percent whey protein
solids by weight, an appropriate proportion of water to permeate is
centered around a ratio of 5:1, or about seventeen percent by weight
permeate solids.
In accordance with the method of the invention, such a
dispersion (for example 20 grams of dry permeate mixed with 100 grams
of water) must be conditioned to a state of readiness as a partially
polymerized resin intermediate, before it is useful as a
thermosetting binder. This is readily accomplished by ammoniation
.:
2~;i3~1.
'~
of the dispersion to a pH level of at least 8Ø In the example cited
immediately above, very little bufferiny was noted near neutrality
and only about 4 grams of twenty-six percent ammonium hydroxide were
required. If the particulate material to be agglomera-ted is highly
acidic, as may be the case with coals that still contain considerable
pyrite, it may be necessary to raise the pH of the dispersion
considerably above 8.0 to 11.0 or even higher to counteract this
acidity.
Numerous fundamental changes occur in the character of the
dispersion as a result of this single step of ammoniation:
. .
a. lactose mutarotation is accelerated and the resulting
dynamic equilibrium provides the replenishable supply of
glucose aldehydes needed for sustaining the Maillard
reaction with the ~-amino of lysine;
b. the globular proteins and peptides undergo pH
denaturation - the tertiary and secondary structures are
unfolded and uncoiled and the reactive side chains,
particularly the ~-amino groups of lysine, are exposed and
become available for reaction with the aldehyde of lactose;
c. the alkaline pH provides an environment conducive to
initiating the base-catalyzed Maillard reaction (and
subsequent production of formic acid is inhibited);
d. supplemental nitrogen is available for the melanoidin
~5 for~ation reaction that is characteristic of advanced stage
Maillard reactions; and
e. dispersity (solubility) increases and the mixture
appears less opaque and viscous as the pH is increased above
the isoelectric point of the whey serum proteins (4-5.5).
2. COAL ADMIXING AND PELLET FORMATION
16
3~
Mixtures composed of the subject binder dispersion and Coal
Fines II (Table 2) that had been screened to discrete ranges of
particle sizes were run on a laboratory-scale (18 inch diame-ter) disc
pelletizer. These preliminary trials established parameters of
equipment operation and a relationship between moisture, binder
solids content, viscosity and particle size. Predictably, the
moisture content required to achieve the capillary state of mobile
liquid force binding increased as the average particle size
decreased.
'.': `;'''
Successful agglomeration of ultrafine coal,
recovered, desulfurized and deslimed after years in a slurry pond, was
considered a worst-case test and its accomplishment the realization
oE one oE the invention's principal objectives. The laboratory
proced~lre Eor agglomerating this type of recovered ultra~ine coal was
comprised of~
a. admiYing to one kilogram of oven dried ultrafine coal an
amount of binder dispersion estimated to be slightly below
the optimum needed for balling - in this instance 30û grams of
binder dispersion provides a very viscous consistancy. This
1~ 3 kg admixture contained 19.4% (254 gms) water and 3.5% (46
gms) permeate solids;
b. readjusting the pH with ammonium hydroxide, if
necessary, to a range of at least 8.0 - 9.0; and
c. introducing this admixture to the disc pelletizer, along
with an intermittant spray of binder dispersion, until
nucleation and particulate coalescence proceeds to where
spherical balls of about 1.5cm predominate on the disc.
31)
An overall material balance of several batches made in this
17
'''`"`''''~
;~ 3Z~.
manner provided approximate green pellet compositional data:
moisture content = 20.2~; permeate solids = 3~%. Greenstrength was
more than adequate in-this example, with green balls averaging more
than 10 drops of 30 cm before any breakage.
3. DRYING AND CURING
The physical properties of dried agglomerates, especially
weather resistance and strength, are in large measure dependent upon
the e~tent of the heat treatment applied to the green balls. As the
final temperature to which the agglomerates are subjected is
increased ball strength and solubility in water changes over three
distinct ranges:
a. the initial stage extends up to a temperature of about
170C; products cured below this temperature rapidly
disintegrate upon immersion in water;
b. products dried and cured in the transition stage, from
about 170C to about 185C, will slowly leach a dark brown
substance when immersed and thereafter exhibit a loss in
strength; and
i c. the final temperature stage begins at about 190C, with
products heated to, or above, this point assuming an
increasingly coral-hard, abrasive and totally insoluble
character.
Agglomerated balls may be dried by any convenient means that
does not remove moisture at a rate so rapid as to cause heat-checking
or cracks in the agglomerate structure. Heating in the range of 120-
170C, after ball drying is complete, drives the reaction to nearcompletion. Aftercooling, the balls will be strong and hard butwill
18
~o~s~
readily and completely dissolve in ~ater and color it a dark brown. i
When the temperature range is increased to 170C - 180C, the
pellets will not subsequently dissolve when immersed in water, but
will color the water to a lesser degree and take on an eroded surface ;~
texture. Hardnessand strength are degraded by prolonged immersion. ~i
Balls heated directly, or even reheated, to a temperature in ;
the range of 190 - 250C become extremely hard, irridescent,
resistant to abrasion and completely insoluble, exhibiting no
leaching or loss of strength after extended periods of water
immersion.
The gradual improvement instrength and weather resistance of ` ~`
lS the fully dried balls during heating in the transition and final
temperature ranges is accompanied by a weight loss that is equivalent ~-
to approximately 1/3 to 1/2 of the oriqinal binder dispersion solids
weight. This weight loss by gaseous emission indicates extensive i
chemical activity during the terminal, thermosetting phase, of the ;~
Maillard reaction. Both the thermal decomposition of unreacted or
surplus organic constituents of the binder solids and the
! crosslinking and condensation reactions that are believed to produce
insolubility are likely ccntributors to these emissions.
EXAMPLES
, -,.
The order of presentation of the Examples depicts the
sequence in which particularly significant experiments were
performed. Progressively, the results and observations revealed the
novel properties of this specific combination of materials and
treatments; first asan insoluble particulate binder, thenas a strong
19 " ,;','',~'
3;~
and black thermoset resin, and finally as a stable thermosettable
resin intermediate. The description of the materials utilized are
listed in Table 2 at the conclusion of the Examples.
EXAMPLE 1
Unsatisfactory Comparative Results
The methods of C.W. Humphrey disclosed in U.S. Patent No. 3,567,811
were utilized as general procedures in further investigation of the
use oE whey and its derivatives as replacements for molasses in the
preparation of binders for the agglomeration of coal fines. A
standardized dispersion of whey permeate was employed as a basic
starting binder formulation in trials of variations of the ~lumphrey
technique, as well as for the preparation of binder formulations used
ls in ensuing examples. This standard dispersion was prepared bymixing
ten parts of water by weight with two parts of dry permeate.
Agglomerates of iron ore and other materials prepared by the
Humphrey method, regardless of the carbohydrate employed in the
formulation, require a specific secondary treatment to obtain the
desired durability and water resistance, e.g., extreme high
! temperature or hydration. When subjected to temperatures in excess
of 200C, the carbohydrate in the binder of coal agglomerates
carmelizes and then decomposes, leaving dissociated particles.
Agglomerates dried or cured at lower temperatures readilydissolve in
water. As the ability toendure all weather storage and handling is a
requisite of a commercially acceptable artificial fuel, coal
agglomerates prepared by this method were examples of unacceptable
results.
During one such unsuccessful trial the pH of an admixture of
Z(~ 3Z~ ! ~
;' '
the standard whey permeate dispersion with pyrite-containing coal
fines (Coal I), was observed to fall steadily over 2 hours from an
initial level of 6+ to below 4. Disintegration failure of extrudates
earlier prepared from this admixture was attributed to degradation of
5 the carbohydrate ir- the binder caused by sulfuric acid leached by the
coal's pyritic inclusions.
EXAMPLE 2
Pyrite ~eutralization
1 0
To counteract the drop in pH level previously observed, the pH
of damp Coal-I Eines was adjusted to about 11 witll ammonlum hydroxide
prior to drying the fines and then admixing with the binder
dispersion. A suficient amount of the standard binder dispersion
15 was added to the ammoniated and dried fines to obtain a final total
solids to water ratio of approximately 5~
' ' ~
A firm and void-free 20 mm diameter column oE this admixture
was extruded on a laboratory extruder, cut to 3 cm lengths, and then
20 slowly dried and heated over a period of about 40 minutes to a
temperature of about 175C.
,
After cooling, the samples were found -to be hard and strong ;
and, following a 24-hour immersion, somewhat water-resis-tant. ~
25Although the soak-water in the immediate vicinity of individual ;
specimens was distinctly discolored dark brown, the samples did not
readily disintegrate and retained a considerable degree of integrity.
,.' .,.:'
The pH of the unused coal admixture was measured several hours
30 after mixing and, as in the previous example, the pH had dropped
several units, from about 11 to well below 8, indicating a continued
21
2~053~1
leaching of acid.
EXAMPLE 3
Adjustment of Binder Dispersion pH
The sample preparation procedure of Example 2 was repeated,
except that for this trial the pHof the standard binderdispersion was
adjusted with ammonium hydroxide to a level of about 10 prior to
admixing with dried, but untreated, Coal-II fines, and the heating
cycle was extended to one hour by adding a twenty minute interval at
190C
The cooled specimens dlsplayed ~urther improvement in
physical properties; they were stronger, extremely hard, showed no
signs o deterioration after a 24-hour water immersion and,
significantly, the soak-watershowed very little discoloration. The
pH o the unused admixture appeared stable over time at about 7Ø
EXAMPLE 4
Reactive Properties of Coal
1 Example 3 was repeated except that dried, very-fine, white
'` t` silica-sand was substituted for coal fines. As the extruded samples
were heated they rapidly changed color from an off-white to brown as
25 the temperature reached 100-120C, and then to a very dar]c brown at
about 160C. At this temperature several specimens were removed from
the batch being heated and examined separately, with the remainder
allowed to complete the heat cycle.
The key observations from this example were: the color of the
binder filling the intersticies of the white sand changed from an off-
22
2S~0S~
white to almost-black well below the decomposition temperature of
alpha lactose (202C); although they were as strong and hard as fully-
cured coal agglomerate (Example 3), the samples removed at 160 were
soluble, unless reheated to above 190; and, coal appeared to play no
identifiable chemical role in the binder polymerization reaction.
In all other respects there appeared to be no appreciable
difference between the specimens formed of coal in Example 3 and the
specimens made from sand. The much desired property of insolubility
appeared to be notonly pH, but temperature dependent and the reaction
imparting it was identified as a variation of the Maillard browning
effect.
EXAMPLE 5
Comparitive Reactions of Alkaline Reagents
Separate portions oE the standard dispersion were treated
with aqueous solutions oE potassium hydroxide, sodium hydroxide and
ammonium hydroxide to raise the pH of each to at least 8Ø A small
quantity oE each treated dispersion (barely suEEicient to coat the
bottom) was placed in separate foil lab dishes. As a comparative
specimen a fourth dish contained an unammoniated sample of the
standard dispersion.
: ' '
The four samples were simultaneously oven-dried and then
observed as they were slowly heated to 200C. Except for the sample
treated with ammonium hydroxide, all mixtures behaved in a somewhat
similar manner, slowly coloring to tan and then to a dark-brown
bubbling mass, before finally decomposing to a soft, gray-black,
water-soluble char.
23
`,
- 2g~1D53~1.
The ammoniated specimen darkened earlier and more rapidly,
produced gases Erom small bubbling pores and then became a jet-black,
shiny and opaque material that evenly coated the dish bottomO Upon
cooling the waEer-like material released easily from the dish and,
after a 24 hour immersion, retained its stiff, some-what brittle
character, and left no color or residue in soak-water.
These three alkaline reagents were subsequentlyincorporated
in analogous dispersions of skim milk, whey and lactose and observed
while undergoing similar heat conditioning. Except for pure
lactose, the results obtained closely paralled those observed with
permeate; the ammoniated sample survived in each instance as a black,
insoluble polymeric ma-terial and the other materials decomposed.
., .
All samples composed ofpure lactose remained clear solutions
until they simply crystallize(l, carmelized, outgassecl and Einally
began to decompose.
EXAMPLE 6
Temperature Parameters Of Milk & Byproduct Reactivity
Six liquid dispersions were prepared by mixing ten parts of
water with two parts of the dry solids of each of the following: skim
milk, whey, WPC, permeate, lactose and DLP. A small quantity of each
dispersion was placed in a separate aluminum dish as a reference
standard. The remainder of each dispersion was adjusted with
ammonium hydroxide to a pH level of at least 8Ø
Three aluminum dish samples of each ammoniated dispersion,
together with samples of the reference dispersion of each material,
were dried and slowly heated to 160C. After ten minutes at this
24
3~
temperature, one of each ammoniated sample was removed for
inspection. The same procedure (removing one of each type of `
ammoniated sample)was followed after 10 minutes at 185C, and then 10
minutes at 250C. (The behavior of all lactose samples was similar to ;
that noted in Example 5: no reaction until melting-decomposition.
Its further evaluation was, therefore, discontinued.) The 160C
samples all readily dissolved in and discolored water, and all were
black, with the exception oE the standard samples, which were dark-
brown. ~
~';''`'`''`
At 185C the reference samples had all decomposed to ash, but
the five ammoniated materials remaining under evaluation were hard ~`
and black, and substantially insoluble in water, although they
softened somewhat and slightly discolored the water over time. The
specimens conditioned to 250C were all harcl, jet-blaclc, insoluble
and unchanged after water immersion, although the WPC had expanded to
a rigid, but crushable, foam. The remaining four materials (skim
milk, whey, permeate and DLP~ exhibited a wide variety of surface
characteristics ranging from a shiny and iridescentgloss (skimmilk)
to a flat black (DLP).
These results demonstrate that aqueous dispersions oE milk
solids that contain both lactose and protein, and have beenammoniated
to a pH of about 8, will form a partially polymerized, but soluble,
intermediate compound when dried and heated at temperatures below
185C. This intermediate polymerizes to a substantially insoluble
material at temperatures above 190C, and becomes totally insoluble,
hard and inEusible at temperatures in the region of 200-250C.
EXAMPLE 7
Agglomerate Strength vs Binder Solids Content
;~053~
Spherical agglomerates properly prepared from particulate-
liquid mixtures by rotating disc pelletizing inherently contain a
nearly optimum amount of moisture. In this condition balls or
pellets naturally develop strong interparticle forces, or green
strength, through internal liquid capillary suction. Within limits,
a thermosetting binding agent added to the mixture enhances not only
cohesion and weather resistance but several other important physical
properties oE the cured agglo~nerate. ;
Information indicative oE the extent oE physical stength
enhancement attainable by increasing the solids concentration of the
binder dispersion was obtained by the destuctive testing of
individual groups of disc pelletized balls agglomerated with binders
containing graduated solids-to-water ratios. The test results in
Table 1 are Eor groups of ten, 1.5 cm balls, prepared Erom recovered
ultrafine Coal III that all initally contained about 20.~ percent
moisture and were dried and then heated to about 250C.
26 ~;
z(~53~
:
:
TABLE 1
~gglomerate Physical Properties
Dry Permeate To Water Ratio
Property ______ _ _ _ __ _ _ ~;
(Standard)
0.5:5 1:5 1.5:52:5
Green Strength 14 20 21 25
(Ave. 30cm Drops)
Impact Resistance 3.6 38 46 50
(Ave. 45cm Drops)
Abrasion Resistance82.9 96.1 98.099.1
(100~ , minus the
weight loss)
Compressive Stength0.7 2.9 3.73.1
(Kilograms)
~,
,
Test Conditions Summary:
Green Strength Drop Test - Uncured balls were dropped
repeatedly ~rom a height of 30 cm onto a steel plate to determine the
averaye number of drops the balls of each admixture withstand before
breaking. -~
Impact Resistance Drop Test - The same procedure as in the ~
above testexcept that cured balls weredropped from a height of 45 cm. ~ ;
Abrasion Resistance Test - Approximately 100 grams oE cured
balls of each group were rotated in a 6 inch diameter, 10 mesh, screen
cylinder at one revolution per minute for three minutes and the welght
percentage of the dislodged particulate deducted from 100% (the
original weight).
Compressive Strength Test - The average value at which ;
failure occurs when individual balls of each group were subjected to a
slowly increasing compressive load.
-
20~1153~
TABLE 2
Materials Utilized In Examples
Dalry Products & Waste Byproducts Typical Dry Solids Content:
DescriptionProtein Lactose Specification
~common name)(Wt.~) (Wto%)
Skim Milk _ _ __ __
(Milk)35 typ. 52 typ. Consumer Grade
Whole Whey
(Whey) 12 min. 75 max. FDA 21CFR 184.1979
Whey Protein
Concentrate
(WPC) 34 min. 52 min. FDA 21CFR 184.1979c
10 Whey Permeate
(Permeate) 4.5 typ. 93 typ Manufacturer's Spec.
Lactose
(Milk Sugar~ 0.15 max. 99.3 min. FDA 21CFR 168.122
Delactosed
Permeate (DLP) 5.8 typ. 74 typ. ~lanufacturer's Spec.
____ . _ . _ ___ __ _ __ _ _ _ _ __ _
Particulate Materials:
_ _ . . _ _ _ . ~ . . _ _ _ .
Descriptlon Origin Mesh Size Remarks
(common name)
Coal I Carbondale(Ill.) -No. 35 x 0 High sulfur & ash
(Raw Slurry) Group recovered fines
Coal II Pittsburg -No. 50 x 0 Newly minedr
20 (Fines) No. 8 Seam cleaned & reground
Coal III Pittsburg -No. 100 (100~) Recovered & ~ ;~
(Ultrafines) No. 8 Seam -No. 325 (50%) deslimed; slurry
, pond
Silica Sand California -No. 60 x 0 Finest washed
(Sand) Quarry crystal grade
~5
SUMMARY -~
Disclosed herein is a method that was specifically developed
to convert aqueous dispersions of lactose and whey serum protein into
a thermosettable resin intermediate that can subsequently be
transformed by the application of heat into an infusible and insoluble
resin. A principal objective of the invention is the beneficial ~-~
utilization of waste dairy products such as whey and its derivative ~-
~;"~.
28 ~ ~
. :.
Z~ S3Z9~ ~
products.
,~,
This new composi-tion is apparently the productoEan extended
or terrnlnal Eorm oE the Maillard reaction induced by the intense
heating of a dispersion oE a glucose-containing reducing sugar and a
denaturable lysine containing protein after alkalization with
ammonia. It is well known that numerous reducing sugars and other
forms of protein combine when heated to exhibit the browning
manifestations of the Maillard reaction. It is within the intent of
-the disclosure, therefore, to point out that other sources of glucose
sugars, e.g., cellulose and starch, in combination with other
proteinaceous materials, such as soy flour, are expected (or
potential) substitute ingredients in the preparation oE this or
analogous intermediates and resins.
While certain preferred embodiments and examples o~ the
invention have been specifically disclosed, it should be understood
that the invention is not limited thereto as many variations will be
readily apparent to those skilled in the art and the invention is to be
given its broadest possible interpretation within the terms of the
following claims.
29
