Note: Descriptions are shown in the official language in which they were submitted.
~L~13Z~i
_ELD OF THF. INVENTION
The present invention relates to synthetic fire-
logs, and more particularly to synthetic firelogs made
without wax, or with a reduced wax content.
BACKGROUND OF THE INVENTIO_
Conventional synthetic fireplace logs generally
contain up to about 65% by weight of oil refinery slack
waxes which are physically admixed with finely divided wood
particles and extruded into the desired log-like shape.
However, with reserves of crude mineral oil dwindling, ener-
gy conservation is becoming increasingly important, and the
prices of oil-derived products are rapidly increasing. Syn-
thetic firelogs, although generally quite fuel-efficient,
are increasing in price. Moreover, with more important end
uses for the waxes available, such as conversion to gasoline
or plastic monomers, it is unlikely that sufficient slack
waxes of adequate quality will be available for use by the
synthetic log industry in the future. Some of the "waxes"
now available are in fact more in the nature of refinery
slops, and are quite unsuitable for conventional methods of
synthetic firelog manufacture.
-; SUMMARY OF THE INVENTION
- It has now been found that synthetic firelogs may
be manufactured using materials other than slack waxes if
such materials can be treated to give the logs manufactured
therefrom the desired properties.
According to the invention, a synthetic firelog
comprises a log-shaped extruded mass of a material of suffi-
cient dimensional stability to hold its shape at normal room
, 30 temperatures,
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and carbonizable on combustion to provide a porous skeleton
wh:Lch will substantially maintain the configuration of the
log, the material comprising a mixture of 25~ to 70~ by
weight of particles of solid cambustible material, the
balance consisting essentially of a combustible solid bin-
der, the binder consisting of at least about 15% by weight
of the log of at least one normally liquid combustible by-
product, and a further component interacting with said
liquid combustible by-product to solidify the latter and
form said binder, the combustibility of the extruded mass
being such as to provide a safe but aesthetically acceptable
rate of burning under firegrate conditions from the time the
log is fully alight until substantial consumption of the
volatilizable content of the log.
By by-products are meant secondary or waste pro-
ducts resulting from a process of making some other product,
and mixtures of such products.
In one form of the invention, the solid combus-
tible material includes preferably about 35%-40% by weight
of a particulate cellulosic material which carbonizes to
form the skeieton. Enough cellulosic material may be
present to form during burning a porous carbonized skelton
which substantially maintains the shape and dimensions of
; the log. The formation of such a skeleton may also be
achieved or assisted by the formation of coke on combustion
of the liquid combustible waste product, or by an alterna-
tive or additional further component which either carbo-
nizes to ...................................................
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form a suitclblc skeleton, and/or itself provides such a skeleton.
Tn some cases, the at least one further component can
entirely con~ist of particulate cellulosic material which
not only forms the skcleton but i5 able selectively to absorb
liquid components from the liquid by-product and reduce
the latter to an extrudable solid, whilst in other instances
the at least one further component provides a structure
within which the liquid by-product is dispersed to form an
extrudable solid, the structure also providing the skelekon
on combustion of the log. In most cases, however, at least
two further components will be utilized, one, which will
usually be particles of cellulosic material, with the primary
function of forming the skeleton, and the other with the
primary function of solidifying the li~uid by-product. Either
~ component, together with further.components and modifications ~:
to the physical structure of the log may be utilized to ~ -
; achieve the desired rate and completeness of burning of the
. log. Thus the combustion properties of the log may be controlled :
by one or more of the shaping of the log, the inclusion of ~ .
flaws or flaw inducing means in the log, the character and
. particle size of the particulate material, the inclusion of ~:
a combustion modifying additive, controlling the order and
, ~1
~,. vigor of admixture of the various ingredients, and the selection
. of the by-product.and the further component or components.
. . ,~ .
~ The component or components interacting with the by-product
. . .
` may comprise one or more substances combining physically there-
,~: with to a solid solution or gel or other solid dispersion,
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~nd/or chemic~lly therewith to form solids.
Suitable liquid combustible by-products include pitch
residues from the treatment of vegetable or animal materials;
asphalts and coal tar pitches, creosote residues; sugar
refininy by-products; organic by-products of pulp and paper
production; used, spent or spoiled lubricating or industrial
or cooking oils; crude soaps or ~atty residues from the soap
industry; crude oils and fats or residues thereof from
industries processing vegetable or animal oils, by-products
10from the manufacture of starches and polysaccharides; and
refinery bottoms, slops and oil pitches.
In order to convert the foregoing materials into -:
extrudable solids that can be combined with cellulosic
: particle~ to ~orm satisfactory synthetic fire-
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l.ogs, thcy aro combinecl with modi:Ler.q selec-tcd to provide
thc nece~ssal.y so~idifyi.ny and/or plastici~ing e~ec-t such as
~atty ~cids, fa-tty acld salts, ol- ~lycerides; waxes; solid
solu~ion forming synthetic polymers; synthetic or natural
surfac~ants, soaps; rosins and rosin modified plastics;
synthetically modified natural products such as stear~tes and
gums; solid hydrocarboIIs either natural or synthetic; and
lignosulphonates, lignin or sulphite lyes. In some cases,
one licIuid combustible waste or by-product may be used ~s a
modifier for another such product, or the waste or by-product
may partially replace a fuel conventionally used in firelogs, ..
such as slack wax, which itself acts as a modifier for the :~
waste or by-product.
In order to permit e~ficient combustion of the
synthetic firelog, the following further materials may be ~. .
included in the fuel-modif-er mixture in order to control the ~ ~ .
combustibility of the resulting log: non~porous extenders,
such as clays, graphite, coal dust,diatomaceous earths, silica,
mica etc, oxidising agents to assist combustion such as per-
borates, peroxides or persulphates; acid generating media to
catalyse thermal degradation; alkaline media to block thermal
polymerisation or produce higher melting point materials;
chemically active materials to assist in ring openiny or
double bond breaking; fire retardants to extend burning times;
and low flash point liquids and solids to maintain continuous
combustion.
~fficient combustion of the synthetic firelogs may
also be assisted by the selection of the shape of the &xtxuded
logs. The lo~s may have grooved surfaces to assist in the
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prop~tion of tl-e flaines; or may be hollow, or extruded with
holes th~rein or therethrough Conventionally shapea logs
may ~l~o be produced with intention~l flaws therein, or with
a~ents included therein to inducing flawing or cracking
duriny burning and thus assist in the complete combustion of
the log.
Further features of the invention will be apparent
from the following more detailed description of preferred
embodiments.
S HORT DESCRI PTIO~ OE' THE DRP-WI~G
In the drawing:
Figures lA, 2A and 3A show different form~ of
extruded firelog, and
Figures lB, 2B and 3B show, diagrammatically,
relevant portions of apparatus for extruding such logs.
DESCRI PTION OF TE~E PREE~ERREI) EMBOD~ TS
In the following description, all parts and percent-
ages are by weight, unless otherwise stated.
Among the combustible liquid by-products which may
~20 be used in the manufacture of the novel synthetic firelogs of
the present invention are:
Veqetable Pitches and Tall Oil Pitches and Sulphite ~yes
These materials are respectively by-products of the
destructive distillation of vegetables, seeds, leaves and
flowers; by-products of destructive distillation of timber;
and by-products of the destructive extraction of cellulose
fom timber to form paper.
Vegatable seeas such as coconut, soyabean, sunflower,
corn, ~round nut, almond, olive, palm, castor, babassu, cotton,
_ 7 _
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]inseecl, oi-ticia, perilla, canbra, safflower, sesame, and
tung arc cnemically scparated on a large scale to proauce
such fatty acids as stearic, oleic, linoleic, linolerie,
palmitic, myristic, lauric and ricinoleic acids. Complex
mixtures of these and many other ac;ds obtained are then
separated into refined or semi-refined blends or euts, and
have many uses in the manufaeture of soaps, varnishes, paints,
plastics and cosmetics. A viscous dark eoloured piteh remains
after the removal of the useful aeids, and eontains high
lQ molecular weight acids and organie dehris. ~his vegetable
piteh ean usefully be eonverted into a solid fuel suitable ~ !
for synthetie log manufaeture.
A similar material, a by-produet of the destruetive
distillation of wood, is ealled tall oil pite~h. By a similar
process, the useful aeids and ehemieals are removed from wood
to leave a dark viseous end produet, having a similar eompc)si-
tion to vegetable pitch and eomposed of organie high moleeular
weight aeids and debris. The ehemieal eonstituents o tall
oil piteh are generally more unsaturated or higher in aromatie
eontent then those of vegetable piteh.
Sulphite lyes are produeed from timber as a by-
produet of the paper industry. When paper is made from wood,
the reslnous organie eonstituents are dissolved out of the
eellulose eells in th~ form of aqueous solutions of sulphates,
sulphonates or sulphites. The solutions, eommonly having
40-60% solids eontent, are ealled "lyes" or "liquors" and
generieally "sulphite",lignin or "ligno" deseribes the salt
procluet~ EIenee, they are eommonly ealled "sulp~ite lyes",
"lignosulphonate liquor", "lignin liquor" or even more
qenerally pulp liquor"
In order to U5e the foregoing materials in log
manu fac ture, the pitches, which can vary from hiyhly viscous,
sticky liquids having a ~iscosity o~ 3000-15000 centiposes at
20C to mobile viscous ].iquids or slurries of viscosity as
low as a few hundred centiposes, are converted to extrudable
solids. Ideally the fuels used for synthetic firelogs are
firm solids at room temperature and thus hard logs which will
transport without damage are obtained. It has been found that
the viscous vegetable ana tall oil pitches can be converted
into extrudable solids by the incorporation of suitable
modifiers such as
(1) solid fatty acids or fatty acid salts, such as sodium
stearate, oleate and l.inoleate, or the corresponding
alumLnium, calcium, barium, potassium or strontium
salts; .
(2) petroleum or natural waxes such as paraffin, slack,
micro-crystalline, carnuba, montan and bees' wax.
(3) wood resins and modified wood resins such as rosin
esters of various types, dimeric rosin acids, poly-
merised resins dehydrogenated resins, hydrogenated
resins, and alkyd and phenolic copolymers of rosin;
(4) synthet.ic high molecular weight polymers such as poly-
: ethylene, phenolic novolacs, polyethylene glycols,
polybutadienes, silicones, polyxylene, polybutylene,
polyiso~utylene, polypropylene, ethylene vinyl acetate
polymers, and polyvinyl pyrollidone;
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(5) synth~tic surfact~nts such as nonylphenols with high
ethylene o~ide contents, ethylene oxide propylene oxide
copolymers (polyglycols), polyglycol ethersO aliph~tic
oxyalkylated alcohols D and lauryl sulphate and laur~l
sulphate ethers,
(6) solid hydrocarbons such as phenols, reSorcino
naphthalene, quinolene, hydroquinine, ph~halates, ~lu~
tamic anhydride, naphthol, polystyrene and its copolymers
and norbornene,
(7) saccharides, polysaccharides and their acid s~lts
such as sucrose, sorbitol, mannitol, carboxymethyl
cellulose, hydroxycellulose~, cellulose resins, starches,
gums, alginates, proteins, xanth~tes and uronates; and
(8) fats such as lard, tallows, suets, butter, fish lards,
and whale fat,
(9) neutralizîng agents i.e. alkaline materials which
form with the acid components of the pitch salts
which solidi~y or increase the viscosity of the
latter. Suitable alkalis are for example sodium
hydroxide, potassium hydroxide and sodium carbonate.
These may be added to the pitch before it is added
to the sawdust or other particulate cellulosic material
or directly to a blend of sawdust and pitch. Such
neutralization also reduces coXing during bu~ning
o the log and thus provides a more satisfactory
perormance. However, it has a disadvantage when
chemicals are added to the log composition to induce
-- 10--
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colourcd flames duriny burnin~. The normal chemicals
used for this purpose are copper sulphate and cuprous
chlo~ide, often with ammonium chloride added to
i~prove volatility. Under strongly alkaline conditions
such as those produced by sodium hydroxide or carbonate,
the copper salts appear to be converted into copper
oxides or non volatile salts since the flame colouring
effect is noticeably reduced. The desirable solidifi-
cation or Viscoslty increase which occurs on n~utrali-
zation can be achieved without loss of flame colour by `-
the use of weaker bases such as ammonia, ammonium
carbonate, monoethanolamine or other organic amines.
Other methods of countering this interference re--
action are however more convenient. Firstly, the pitch
may be carefully neutralised before addition to the
log mix so that no free alkalinity occurs to upset the
colour inducing chemicals. A standard titration for
free fatty acid on each batch of pitch may be used to
determine the exact amount of alkali required which
~20~ may then be added to the pitch in a pre-blend tank
- where with sufficient agitation and heat a neutral salt
or "soap" may be prepared. Such a "soap" can then be
maintained in molten form for subsequent addition to
the log mix~ A simpler means of neutralization avoiding
. .
` ` colour loss is to change the alkali ;n such a mann~r
that it cannot contact the colour chemicals without
first reacting with the pitch. Thus the chemicals may
be added to the dry sawdust and mixed with sufEicient
wax or other water insoluble material so that it i9
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coate~l. Subsequent addition of pitch in the acid
form follow~d by other fuels (wax etc) and finally the
neutralizing alkali ensures tllat the risk of contact
between the alka]i and colour chemicals is minimal.
I,ogs made by this method showed no deterioration or
loss of flame colour whereas when the alkali was not
separated from the colour producing chemicals some
permanent loss of flame colour was observed.
(10) additives which copolymerize with the pitch acids to
form solids, Such polymerization can be achieved by ~ -
a variety of routes and the degree of polymerization
or thermal stability of the pol~mer can be controlled
to prevente~Y~sivecoking or flaring of the log. Suit-
able additives or compounds containing active hydroxyl
groups such as glycols, formaldehyde condensation
polymers such as urea-formalde~de and phenol-formalde-
hyde, paraformaldehyde, and epichlorohydrin. For
example, the addition of 5 per cent by weight of para- -
formaldehyde to a liquid bend of pitch and sawdust
20 ~ gave a solid which produced excellent logs with good
burning properties.
~11) oxidizing agents. Oxidation of the pitches gives a
significant increase in viscosity and csn result in
the conversion of a liquid pitch into a solid pitch
in some cases. This is believed to be caused by
oxidative polymerization similar to that achieved in
the production of oxidi2ed asphalts and castor oils.
The e~fect can be obtained hy the use of air passed
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thro~ the heated liquid pitch, or by the addition
o~ solicl or liquid oxidizi~g agents such as perborates
to tlle mixture.
Other solid or~anic material or liquids which can
be con~erted into solids by, for example, neutralization or
pol~nerization, may be suitable for modifying the physical
structure of the pitches.
Low cost effectiveness and deleterious properties
such as coking, toxicity, sooty flame, and rapid co~bustibility
of some of the above groups or individual modifiers make them
less desirable than others for use in synthetic firelogs.
The amounts of modifier required are determined by the need
for the resulting material to be extrudable and essentially
solid at normal ambient temperatures. Certain pitches from
distillation plants where maximum recovery of "light ends"
is made, have such high viscosity as to require little
modification, and as little as for example 0.25-2% by weight
a suitably chosen modifier is sufficient to form a solid
extrudable blend of the fuel, the modifier, and any further
additives employed.
.
The preferred modifiers are of course the less
costly ones and comprise materials from all of the above
mentioned groups, including fatty acids and salts; paraffin~
slack and microcrystalline waxes; wood rosins and their
modifîed forms, polyethylene, phenolic novolacs, polyethylene
.
~lycols, EVA polymers, nonylphenols, ethylene oxide-propylene
oxide copolymers, polystyrenes, sugars, ca~bohydra~es,
starches, gums, all forms of fats or glycerides, and ligno-
sulphonates.
- 13 -
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usiny 100 parts by wei~ht of a typical pitch as
a s-tar-tin~ material, a fuel that is a firm solid at room
temperature may be obtaincd by thc addition of the amounts
specified of the following modifiers:
stearic acid, 5-10 parts; hydrogenated ylycerides,
5-10 parts; aluminium stearate, 2-5 parts; aluminium octoate,
1-2.5 parts; coonut mono ethanolamine 2-5 parts; nonylphenyl
(50 EtO) 2-5 parts; polyethylene glycol (M.W 6000), 2-5
parts; sodium oleate, 3-10 parts; sodium linoleate, 2-7
parts; wood resin, 3-10 parts; lignosulphonates, 1.5-6 parts;
sugars 3-8 parts; polysaccharides 0.25-1 part~
Most of the above ranges of modifier content are
suitable for both medium and high viscosity vegetable or :~
wood pitches. Particular blends may also give other
desirable features such as smooth extrusion without plugging,
and less sooty burning. Specifically, the fatty
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acids and glyceride~ or fatty ~cid salts are particularly
satisfac~ory ~or obtaining these t~lo f~atures. The salts are
known ind~strially as lubricating so~p~ and hence addition
of these ensures a good lubrication during extrusion of
the logs E~owever, some of the free solid fatty acids polymerise
under mild oxidative conditions and elevated temperatures
and this can lead to excessive coking, Coking is caused by
incomplete combustion, and gives a cohesive carbon structure
that can produce a hard skin ~n the log ana result in suffocation
of the flame, a very slow flame spread during initial ignition,
and small flames with excessively long burning time~ for the
log. Some degree of coking is desirable, as it gives predictable
burning times for the logs and minimises the risk of the
splitting or breaking up of the log upon combustion. It
has been found that neutralisation of the fatty acids to form
salt reduces coking, perhaps by removing the active hydrogen
on the carboxy group and/or deactivating any active alcohol `~
side chains. In the case of oleic acid~ linoleic acid, etc.O
the neutral salt i9 the desired form for the same reasons,
but also because this salt is a solid whereas the acid
i5 a liquid. Wood rosins are o~ similax structure ¢hemically
and hence these too are preferred in the neutralissa form even
though they are hard brittle solids and can be used as free
acids to give a solid solution with pitches. Similarly the
acidic pitches may in SOmQ cases be neutralised to optimise
their properties. Hence b~ careful select$on of the addit$ve
and degree o~ neutralisation an ideal blend can be selected.
Gl~ceride~ ar~ also capable of polymeri.zation and coking,
acid or alX~line media re~ulting in the hydrolysis of the
ester bond with improved combustionr Other methods of controlling
coking have also been found. Unsaturated acids or glycerides
burn more readily as a result of the oxidative double bonds
e,g, oleic, lineoleic and linolenic acids burn more readily
with less coking than does stearic aci~ or hydrogenated glycerides.
Suitable modifiers are hence blends of stearic, oleic, linoleic,
lineolenic acids which may be partially or wholly neutralised.
The neutralisation may be carried out prior to
compounding of the log mix; for example caustic soda in solid or
liquia form is added to the acid in predetermined amounts in a
suitable mixing vessel. The molten salt produced may then
be blended with the pitch ~or addition to the remainder of
the log mix or added directly into the log mix before or after
the pitch, preferably after the pitch in order to take advantage
o~ its lubricating property during extrusion of the logs.
Neutralis.ation may also be carried out directly in the log mix,
for example, by adding caustic soda, sodium carbonate, aluminium
: 20 hydroxide, or o~her alkali to the mixture before or after
the addition of the acidic material. A more desirable alternative,
since the final mixture has to be cooled to allow extrusion,
is to preneutralise the acid to it~ salt and prepare it in
the form of a powder or flake for addition to the log mix.
; This means that the heat of reaction produced during neutralisation
and the latent heat of liquification of the prQduct~ do not
have to be removed from the mixture before it is extruded.
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coXin~ may also be reduced by the inclusion in
thl~ mix of ~ non porous powderea extender such as graphite,
china clay, silica)diatomaceous earth, etc. Thi~ extends
the liquid phase over a larger surface area part of which is
non porous and as a result the cohesion of any carbon coke
skeleton foxmed during combustion is reduced. For example,
the addition of 5 parts of china clay to 100 parts of a mix
which exhibits severe coking and flame suffocation results
in reduced coXing and a more continuous burn. A similar
effect can be achieved by controlling the particle size of
the wood waste car~ier or any wicking agent employed. Meaium
sized wood particles 1/10" 20 mesh 40 mesh and 60 mesh give
su~ficiently little surface area that the film thicknes~ obtained
when coated and saturated with the fuel at normal ratio by
we~ght (40:60) i~ signiffcant and the carbon skeleton
(coke) therefore has a degree of cohesion. If very fine
sawdust is used e.g~ 80 - 100 mesh the additional surface
area to be wetted results in a thinner fuel film and hence
a less cohesive coke skeleton. This has bee~ tested u9ing
the following formula:
Wood Particles 37.5 pts. by wt.
Tall oil pitch 50.0 pts~ by wt.
Stearic acid lO.O pts. by wt,
When made with normal ~ized sawdust ~circa 20 mesh)
the log suffocated and extinguished itself leaving a hard coked
skin and unburnt;fuel trapped inside. Replacing the coarse
sawdust with 80 - 100 mesh wood flour gave a much improved log
_ 17-
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with a l~ coh~siv~ co}~ed shell ancl co~npl.ete comb~lstion was
acl~i.eve~ 1ith th~ me formula using circa 20 m~sll particles
a s;milar improvernent ~s made by the addition of 5 parts
china clay or 9ilica or graphite.
Increasing the average particle si~e to coarser
than 10 mesh also had the desired effect of ~educing coke
coherence. Whilst the surface area oE the wood was in theory
reduced giving a thicker fuel film, it was found that less
solid fuel was required to produce a cohesive log. This
resulted in the film thickness being similar to that with 20
mesh wood but the area of contact and number of contact
points between the coarser particles was also reduced, and
a more complete burn and a less cohesive ash was obtained.
Tt has also been found that the tendency to coking
is reduced when the sawdust is partially or wholly replaced
by nut-shell fines, bagasse or paper pulp.
Lignosulphonates are usually manufactured in salt
form as a paper mill by-product, and may be used to modify
the pitch to provide the desired extrudability and solidifi-
cation. They are supplied as dark free flowing hydroscopic
powders and can be added directly to the sawdust or other
cellulosic component of the mixture before or after the pitch
or dissolved in the hot pitch prior to spraying on the wood
particles.
Starches, sugars, proteins, polysaccharides and
carbohydrates in general are suitable for addition to pitches
as modifi rs. The materials are typically produced from
sugar cane, sugar beet, various woods, palm nuts, maplet
sorghum, millet, potatoes, corn, etc. Sugars (disaccharides
.
~ 18
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1324~
~Ip to ~ o~ cch~ri~l~s) al-;o h~v~ a uscful calorific value,
but as tllcir rnolecular wei~ht increases ~he tendency to cause
cokinc~ incrcases. This m~y be controll~d or r~duced by the
inclusion in tlle lo~ mix oE oxidizing aq~ntS such as peroxides,
nitrat~s, persulphates or perbor~tes at l~vels up to 15%.
An alterna-tiv~ method is to induc~ fission by inclucling in
the mix fugitive acids such as aluminium sulphate, ammonium
chloride, or acid anhydrides, which on heating or combining
with water driven off during combustion become acidic. Acid
hydrolysis of the polysaccharides pro~uces readily combustible
organic materials such as sorbose, dextrose, glucose,
fructose and hexoses. Addition of reducing agents also
produces more ready combustion. ~ -
Sulfite lyes or liquors can be made suitable for
use by methods similar to those described for pitches and
molasses, except that neutralization is not applicable as
they are already neutral salts in aqueous solution. For
example, addition of polyethylene glycols, lecithin pitch,
sorbitol, mannitol, nonylphenol adducts at 40 mol ethylene
oxide or gelatine can be used to convert these liquids into
the preferred solid or semi-solid extrudable material. As
the water content of the lyes is relatively high (up to 60%)
the amount of modlfier required is proportionately highex
e.g 10-20% of soaps or polyethylene glycols are required for
lyes or 10-30% nonylphenol adducts or lecithin. This renders
the lyes relatively expensive fuel sources and they are bet-
ter used as a diluting component for higher viscosity material
such as molasses. The burning properties of lyes and ligno-
sulphonates are generally better than pitches since they are
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l~ss su~ ct: to ~>ol.yrn~ri z~t :ion ~n~ tllu~; have le~s tendency
to cau~;~ cokin-~.
~iner~l Pitches,__sph.-llts, _oal ~rar Pitc_ec., Creosote
e~i~ues
In gencral al] ~he m~difications that can be
appli~d to vegetable or wood pitches can also be applied to
these materials. These residues also have acidic groups
which can be neutralized to reduce cokiny. However, the
aromatic con~ent of these by-products is generally higher
than previously encountered and sooty flames resul~. This
can be overcome ~o a large extent by the inclusion in the mix
of suitable oxygen carriers such as nitrates, peroxides,
perborates or persulphates.
Suqars, Syxups, Molasses
The combustible material may be a waste or by-
product rom the sugar industry since low grade sugars are
a cheap source of heat.
Extraction of sugars from cane, beet, berries,
millet, fruit, maple, etc. after crushing of the base under
high~ pressure, solvent extraction or tapping, proceed~ in an
established pattern; an initial crude liquor or syrup is
obtained which in itself may be used as a fuel source when
solidified by means discus~ea later in relation to molasses.
However, most sugar producing countries boil of~
excess water and filter to produce crude crystalline sugar
called "muscovado", plantation white or "raws", together with
molasses. During this initial conversion 96-97% of the
sugars present are produced as crude crystalline sugars and
5~O as syrups or molasses - viscous dark liquids of sugar
content as high as 86% by weight. Duxing processing, higher
z~
mol(~c~l]ar ~ci(~ sacch~rides are precipi~ted out by treat-
ment witll, or e~ample, llme to produce powdered calcium
saccharat~s. These ~a]ts can be us~d as fuels i~ synthetic
logs
If solid or crystalline sugars are used in making ~ ~;
log5, the material is melted and sprayed on~o the wood chips
as for a normal molten fuel. The extrudability of the mix
may be improved by the inclusion of modifiers such as polyols,
polyethylene glycols, EVA copolymers, modi~ied wood rosin
esters, gums, waxes, fatty acids, fatty oils, alcohols or
soaps.
Molasses is a more convenient and cheaper form of
sugar for use as a fuel. It is liquid and can be pumped
readily when warmed to a temperature as low as 80F. Despite
containing 20% or more by weight water it burns ~uite well.
It can be readily converted into an extrudable solid form by
the inclusion of relatively small amounts by weight of water
soluble solids such as polyethylene glycols 0.5-So~; nonyl-
phenols of high ethylene oxide content 1-10%; starches, gums
~20 or cellulose derivatives 0.25-5% gelatines, alginates or
xanthates 0.25-2%; wood resins 1-10%.
A particularly useful modifier for molasses is the
substance known as crude lecithin pitch, which is the end
residue of the destructive aistillation of soya bean9.
Purified lecithin i~ used in many dietary foods and vitamin
preparations in which it is claimed to have advantageous
properties. However, the crude pitch is found ta exhibit a
particularly useful property in that it will absorb the water
present in molasses to form a solid. Blend5 of molas5es and
_ 2~ -
..
. , ; .
2g~
lecithirl pi,~Cll irl ratios be-~ween 2:1 and 9:1 appear useful
for log manuacture.
Waxes may also be u~ed -to solidify molasses when
i,ncorporated into a log forming mixture. The wax is added
last and preferably contains a small amount o~ an oil soluble
emulsifier e.g. nonyl phenol ethoxylate, During the mixing
process, the molasses is encapsulated in the wax, and on
cooling a solid wax skin gives the log a cohesive structure.
Molasses to wax ratios between 1:1 and 4:1 may be so utiliæed.
,10 Other suitable modifier systems are similar to
those discussed previously in relation to pitches.
Sugars and molasses tend to char and coke during
combustion but this can be minimized by using the techniques '
previously discussed in relation to their u~e as modifiers
for pitches.
A further series of problems are associated with
water containing fuels such as molasses and lyes. Dapending
on the finished log density, the problem may be minor in
~ nature or major. The synthetic logs currently on the market
-~ 20 cover a wide range of density. Low density logs are extruded
or formed using a relatively high speed but low compression
' ratio compactor or extruder. The log thus produced shows no
signs of stress cracking but is larger in diameter to achieve
,' a standard weight to length relationship. It is cohesively
weak being spongy or soft in texture and often does not handle
well during packaging and shipping. Thus it is not uncommon
for such logs to arrive at the point of sale broken into two
or more pieces.
High density logs are hence preferred as they are
.
~_
, . ,
~L32~6
, . ..
not only qu;te firm and hand]eable at the warm extrusion
tem~rat~res b-~t on cooling they are hard and cohe~ive and
very l;ttle clama~e is sustained during handling and trans~
por ta tion .
With low density logs few problems occur when using
mola.sses even at relatively high levels e.g up to 40% of
total log weight, alone or together with up to 20% of sulphite
lye. f-Iowever, with high density logs some problems occur.
Using normal feed grade molasses having 25% water conkent, no
unusual prablems occur when up to 25% of the wax is replaced -
- e g. 40 pts sawdust, 15 pts molasses, 45 pts wax. Above this
level of molasses the increased mbisture added via the molasses
begins to plasticize the sawdust thereby making it increasingly
elastic. If the higher solids sugar refinery grade of
molasses (85% solids) is used, it can be used up to 25% of
the total log weight before it too is donating sufficient
water to effect the behaviour of the sawdust. When producing
high density logs with high levels of molasses or lyes,
swelling occurs as the logs leave the extruder and stress -
~20~ ~ cracking develops in the log surface, whilst the logs feel
; springy and soft. The swelling and cracking associated with
:: :
~ both gxades of molasses can be ovexcome if they are added in
.
a particular manner as follows
If the total charge of wood is divided into two
! ~ :
parts and the molasses is premixed with one portion, the pro- ~ ~
.
blems are almost eIiminated - certainly higher levels of the
molasses can be used with no stress cracking. For example
if 10 pts of sawdust a~e mixed with 25 pts of feed grade
molasses a free flowing slightly tacXy material results. A
~ ':
- 2~ -
,;
-- ~$3L32~i
fu~ther 30 parts ~wdust are then mixed in followed by 35 pts
of wax. The mix has the texture of and behaves like a normal
all wax formula giving no swelling or cracking, Higher levels
of t:he refinery molasses can be similarly incorporated with
no serious softening of the log. It appears that the improve-
ment is as a result of confining the donated moisture to only
a portion of the sawdust which is then dispersed by subsaquent
additions with wax impregnated material. As a result the
- springiness is dissipated and contained within the log giving
little swelling and no visible cracking~ The molasses
impregnated wood particles and the wax containing particles
may be made as separate mixes, cooled as necessary and blendea ,
just prior to extrusion.
Replacing part of the sawdust by a cellulosic material
which absorbs moisture less re,adily or is less affected by
absorbed water also reduces the swelling and cracking. For
example the use of peanut shell fines, cocoa bean shell
fines, coconut shell or walnut shell fines, bagasse, or
paper pulp in part or whole replacement of the wood sawdust
gives a log less subject to swelling and cracking. If
this modification is co~bined with the preblending technique
excellent firm logs are obtained. The nut shell replacements
,~ have an additional advantage due to being less absorbent in
that lower overall fuel levels may be employed and yet normal
log appearance and performance is maintained. All or part
of the sawdust may also be replaced by coal dust.
Using the two charges of sawdust in the form of a pre-
blend also so~es two other opposing problems. If the molasses
is added after the wax or soap fuel a sticky mix results
- 24 -
Z4~;
which gives some build-up problem~ on transfer conveyors
etc. The sticky mix can a~so run slower through the extruder
or in extreme cases plugging of the extruaer can result
with excessive ~riction induced back pressure. If the
molasses is added to the entire wood charge and wax or soap
fuel is added last, build-up and plugging are avoided, but
coking of the molasses during the burn is increased with
suffocation of the fire. Both prob~ems are solved by using
the separate wood/fuel mix technique or preblend. Low levels
of molasses may be satisfactorily incorporated by addition
after part of the wax is charged and prior to the final por-
tion of wax e.g. sawdust 40 pts, slack wax 22 pts molasses
15 pts, slack wa~ 23 pts added in order as written.
One final problem associated with water containing
fuels is the temporary loss of flame colour. If the chemicals
added to produce coloured flames are added simultaneously
with, prior to or immediately after, molasses or sulphite
lye, the coloured flames are not evident at normal intensity
until the logs have matured for several days e.g. at least
4 days. It is thought that the cause is the solution of
the chemicals in the m~isture donated by those aqueous fuels
~ which probably occurs particularly if the mix 1s warmed by
; addition of molten fuels, e.g. wax etc. Recrystallization
on aging results in the reappearance of the coloured flames
which improve in intensity to normal as the crystals grow
in size~
It is on the other hand al50 possible to take advantage
of the ab~orbency of sawdust of low moisture content and
- ~5 -
,. . . .
L3Z4~
some ot~ler cel].ulosic parti.cul.ate materials such as wood
flour. If molasses is mixed with such materials, and the
latter are allowed time to absorb moisture from the molasses,
the moisture content oE the latter can be reduced to a level
at which it becomes an extrudable solid, whilst the swelling
and cracking problems discussed above are reduced since the
cellulosic material has swelled prior to extrusion. The
use of molasses alone with the cellulosic material will
usually provide a log which burns too slowly and with exce~sive
coking, but modifiers may be added to the molasses to avoid
this, as already discussed above. Other materials may also
be used in place of essentially cellulosic materials to
absorb the moisture from molasses and to help provide the
necessary skeleton for the log (although the coking of the
molasses, even if reduced by modifiers, will contribute to
the formation of such a skeleton). An example of such a
material is soya flour or meal.
The selection of molasses type and lye aepends on cost
Savings required, available cellulose base (nuts, shells,
wood etc.) and manufacturing process. The lower solids
molasses and lye are mobile liquids at ambient temperatUre
' i
~:~ ' ' . ' '
- 26 -
'.
.. ,. . . - :
:. . , . : ..
, , : ,
~': ' ; '
~IL3;2~3L6
and ~-~nc~ c~n b~ added cool. This reduces the efforts and
costs involved in cooling the mixes to extrud~ble temperature.
Ilowever, the high solids molasses has a higher heat value and
yives less problems as previously discussed. An ideal com-
promise is to use a blend of high solids molasses and sulphite
lye. For example 3 pts of 85% molasses, normally a highly
viscous unpumpable liquid at ambient temperature, becomes a
mobile liquid when mixed with one part 60% sulphite lye.
The blend is 75% solids and burns with less coking then a
~10 75% solids feed grade molasses. Alternatively 4 pts 85%
molasses with 1 part 60% lye gives a mobile liquid which can
be pumped of total solids 80%, This blend has a better heat
value then 75% molasses and gives less swelling etc. as
previously discussed.
Many different types of molasses are avail~ble
depending on the source e.g.
Cane Molasses ~,
Origin Viscosity Viscosity
CP at 20C CP at 20 C
ex factory feed grade
(75% solids)
Ecuador 28000 3250
Iran 7250 3250
- Pakistan 8550 1680 `
' Brazil 21100 ~650 ;
Jamaica 108200 10300
Trinidad 35560 4580
!,' Beet Molasses
Belgium 5460 1460
Germany - 1~140 1800
Turkey 51700 2200
~ussia 6700 2680
~, From the viewpoint of viscosity at low temperatures,
beet molasses is desirable, being lower in viscosity at the
: - :
- X7 -
- ' .
~13;~4~ :
sai~ XJ~i.C~S c~nt~n-. El~ /ev~r, ff~r -r jr~ e~;s of~ th~ logs
tl-~ re~er~ is tru~. ritos- nl)~a~eC; thicken anci so~e "gel"
i~l t}~e ~ ?';(`LlC~ c,~;phoric acic~ ox <,oine organic acids.
U~e can b~ ad~ of this ef~ct to "body~' up the mola~ses
as sho~n in example 32. The ~cid is injected illtO the
In~lass~s streall just prior to reaching the sawdust or the
acid can be added to the wo~d/molasses ,nix immediately
the molassec. has been added. The thicken~ng is thought
to be due to hydxogen bonding induced by polari-~ation in
the molasses.
A particularly useful means of controlling coking
in the logs containing molasses is achleved by compoundinc~
the mix in a specific manner. In such a log, a double
coking effect occurs. The residual resins and tar
residues in the c~llulosic material, eg. wood, coke and
produce a carbon skeleton of some cohesive strength ~uite
naturall~ during the burn. Indeed this is why normal wax
based synthetic logs are so successful: when formulaced
properly, no sagging or dripping occurs as a result of
the coking which occurs on partial co~bustion of the
sawdust. The carbon skeleton acts as a porous but
cohesive wick for the melting and burning fuel. When
substantial amounts of mo1asses are introduced tabove
5% of the total weight of the log) the wood carbon
skeleton is reinforced by the molasses coke to a point
where suffocation begins (at above l~/o by weight of
:
molasses). A dilution of the molasses coking effect
.
can be achieved by preabsorbing all the molasses on
part of the wood component eg. of the ~wo following
formulae, identical in overall composition, formula B
shows markedly less suffocation than A as the second
-28-
32~;
charge o~ ~lntre~ted wood dilutes the molasses coking
ef~ect.
A B
Sa~Jdust (1) 40 ~0 parts by weight
Molasses 25 25 parts by weight
Sawdust (2) ~ 20 parts by weight
Slack Wax 35 35 parts by weight
The ingredients were added consecutively in the order ~-
shown and mixed thoroughly prior to subsequent additions.
Many useful and unexpected features occur with logs made
- incorporating molasses viz:-
(1) Reduced Smoke during burning ~;
.
Side by side comparisons of totally wax logs, wax plus
pitch logs, and wax plus molasses logs show that with
mola~ses visibly less smoke is evolved. The smoke
normally is of two forms - white smoke which is a vapour
of unburnt fuel eg. wax vapour or black smoke as a
result of incomplete combustion. Totally wax loys can
give undesirable amounts of the white smoke as a result
of flash boilin~ at the surface. Pitch, particularly
tall oil and coal tar give black smoke as a result of
partial combustion of the aromatic components therein.
Either or both these components used in conjunction
' ~ .
with molasses give reduced smoke. It is believed the
reduction in smoke is due to t~o effects - molasses has
j oxy~en in its structure and hence should burn less
; smokily, but its tendency to coke also results in a
slower release of other fuels present and hence a higher
oxygen to uel xatio reduces the vapour smoke and blacX
5moXe. Reduced smoking is desirable not only for aesthetic
. ~
,
~3Z~
reasons, hut ~lso because it reduces the formation of
flamrnable d~posits in chimn~ys and flues.
(2) Increased E~ardness
__ __
Despite molasses being a moblle or viscous liquid at room
temp~rature, logs made using molasses are generally harder
than when made with even the hardest of slack waxes. Slack
waxes are most often derived from the dewaxing o-E lubricating
oils and the texture of the resulting wax varies considerably
depending on the dewaxing process, the source of the crude
oil utilized and the type of lubricating oil being produced
from the refinery tower. For example, American crudes
produce quite soft slack waxes often with the texture of
petroleum jelly or margarine whereas certain Canadian crudes
yield slack waxes which are quite firm at room temperature.
In particular the higher the viscosity the oil being
separated, the more cohesive and the higher the melting
point of the slack wax by-product becomes. With the
trend to using lower viscosity base oils in motor oils,
the slack waxes produced have generally tended to become
softer and/or of lower melting point. This trend in turn
results in the production of softer synthetic logs - an
undesirable effect since such logs do not handle well during
::
packaging and are subject to more damage during shipping
and warehousing. The addition of molasses counteracts
~! this trend as shown by the following tests of the hardness
of different log mixesJ thus enabling quite soft and
... .
mobile waxes or fuels to be used without producing a
softer Log.
~ardness oE Log Mixes
- Method a dial vernier with a spring return was modified
-30-
'
-: ; . . ..
Z~
with a 3/16" cone p2rl~t:ration tip and a platform to take
var~ing weigllts. The cone tip was placed on the surface
to be tested and weights were added. Penetration was
measured ov~r an elapsed time period, ie. the higher the
penetration reading~ the soEter the surface.
The slack waxes used as a binder component
of the log mixes axe listed in Table 1. Samples were ;~
made using 6~o by weight binder component and 4~/0 by
weight sawdust, the compositions of the binder component
and the resulting hardness readings being tabulated in -- ;
Table 2. ~ -
The same hardening effect hae been observed ;
even when liquid fuels are used as a partial replacement
of the slack wax, eg.
Li~uid Fuel Textuxe at Room Temperature
Tall Oil Pitch (TOP) Viscous Liquid
Vegetable Oil Pitch (VP) Thin Liquid
Used Cooking Oil (UCO) Thin Liquid
~; Samples were made and tested as above, the compositions
of the binder components and the resulting hardness
readings being tabulated in Table 3.
The hardening effect of molasses is thought to
be due to two main reactions. Firstly the moisture
present in molasses and not present in slack waxes or
pitches, may be preferentially`absorbed by the kiln dried
sawdust conventionally utilized .in artificial firelogs
leaving a solid molasses sugar residue on the outside of
the wood-----------------------------------------------
-31-
'~
~.324~;
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-- 33 --
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324~i
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p~ :
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-34-
3Z4~;
particl~c;. ~ probab]y mo~e signiEicant cause i.s the
gellation ei~f~ct of acids on molasses. Some typ2s of
molasses have been kr-own to c~el Whell compo~nded into
animal feedstocks and these yrades are either avoided
or have to be used carefully to avoid problems in such
applications. Some previous work carried out suggest~
that a particular component of these unusual molasses
is acid sensiti~re and yelation occurs as a result, although
the mechanism has not been fully explained.
We have found that in the pxesence of phosphoxic
acid at particular levels even a molasses considered to
be non-gelling can be made to gel. Over a fairly narrow
ratio of molasses to phosphoric acid gelation occurs and
the viscosity increases at lower levels of addition
suggest a ætoichemetric mechanism ie. the phosphoric
i acid radicals co~bine in some way with the molasses to
~ form a new "copolymer". However other acids particularly
;~ organic acids are known to exhibit a similar effect. Since
wood is acidic it is believed that the acid radicals in
~20 the sawdust cause the hardening due to gellation of log
- mixes containing molasses. This wa~ confirmed by addiny
a small quantity of sodium carbonate to one of two
otherwise similar batches of a log mix containing 35 parts
- by weight of sawdust, 20 parts by weight of molasses and
45 parts by weight of molasses. The neutralisation of
; the wood acids by the æodium carbonate was found to
result in a marked reduction in the hardness of the mix,
confirming that the acidity of the wood contributes to
the hardening process. With the pressure of carboxylic
acids, amino acids and hydroxyl groups in molasses, and
~, ~
- similar groups in wood, it is likely that the hardening
~` -35-
'; ' . .
~L3Z4~il
is c-ls a r~sult ol copolymerisation oE molasses in~redients
and ~ood colnponcnts to forl~ for example esters, ethers
~r polya!nides~ The acid c3ellinc~ effect can be promoted
by addition to the mix oE phosphoric acid or other acid
donating chemicals to speed up gellation.
' Whilst the water content of molasses might appear
to be undesirable, the water can in fact lead to improved
combustion. Papers presented to the wood Energy Institute
of Canada in 1978 show that wood burns most efficiently
at a moisture content of 12-22%. Normally kiln dried
wood is used for synthetic logs, having a moisture content
of 6-10% by weight since with higher moisture contents
extrusion problems occur as the wood becomes springy.
Additions of 2~/o by weight molasses having 80% by we-iyht
active solids to a log mix gives an improved wood moisture
content, from the point of vlew of combustion efficiency,
., i,,
but the moisture is trapped in the molasses and does not
;~ interfere with the extrusion behaviour of the mixture.
Waste Oils and Used oils-Mineral~ Animal and Vegetable
This is a particularly important group since
` not only are used or waste oils cheap usef~l sources of
.. ~,~ .
~; heat as a fuel but, with conservation and energy economy
. ~, . ..
major current social problems, the non~polluting disposal
of such waste products is of major significance.
~ Waste or used oils fall into two groups, mineral
`3`~ or non-edible oils and edible oils. Activities where,~ ~
fairly large quantities of used oils accumulate are:-
(1) Automotive service stations-used engine oils,
transmission oils, etc.
3~
-36-
,~
~ .
~; ' . .
1~3Z~
~2) ~estaurclnts and hotels - usecl coo]clng oils.
{3~ ~eavy industry, sheet metal manufacturers, et~. -
lubricating or metal surfa~ preparation oils.
(4~ Ship repair harbours - waste ~unkering oils,
hydraulic oils and engine oils.
(5) Metal filament industry - oils used during the
drawing process in wire manufacture.
(6) Slaughter houses - waste fats and animal oils.
(7) Tanning industry - hide oils produced during curing.
~8) Soap and food manufacture - off colour or contaminated
fatty oils, etc.
(9) Paint and varnish manufacture - reject castor oils,
varnish oils, etc.
All oils are useful fuels and can be converted
into a form suitable for synthetic log manufacture.
~ . .
~ Conversion into an extrudable solid form suitable for
, ... . .
loy manufacture can bP achieved in a variety of ways,
but all rely on inclusion of the oils into a solid
''''~i`~
j solution. Most organic solids will absorb varying
amounts of oils before losing their solid form at room
temperature. Particularly useful solids are waxes, fatty
: I
;-~ acids and glycerides, rosins, rosin esters, soaps,
synthetic polymers such as polystyrene, polybutadienes,
. ,
` isoprenes, polyolefins, and polybutylenes.
~'
For example, waxes can retain up to 30-40~0 by
:.:";. 1 .
weight of oils before losing their solid form at room
temperature. Blends of waxes are particularly desirable -
paraffins of varying melting points up to 160 F. not
only retain oils ~particularly mineral types) but can
give a quite firm solid at room temperature, as illustrated
by the following table:
-37-
s:
~32~i
R~ined P~raEfi.n/~, used oi]. Texture After
Wax Mpt F. Cooli~Z
125 30 Soft Oily Semi solid
155 30 Slurry With oil
Separation
50% ~ 125; 50% - 155 30 Fai~ly Firm solid
- 25% ~ 125; 25% - 135;
25% - 145; 25% ~ 160 30 Firm Solid
The texture of the above blends may be further
;
~nhanced by dissolving in the hot blend small amounts
(0.25-2~/o) of other solids such as the following:
- 10 polyethylene, polypropylene, polyvinylp~rrolidone,
- polybutylene, polyisoprene, polyisobutylene, polybutadiene,
micxocrystalline waxes, and natural waxes such as carnuba
or montan.
A particularly efficient group of polymers for
- providing solid solutions of oils is the diene polymers.
For e~ample, if a polybutadiene is formed with suitable .
catalysts (lithium aluminium hydride or titanium tetraiodide)
to give a high level of transfiguration it will reta-in as
much as 96% by weight of oils. The polydiene i9 heated
in the oil until dissolved and thoroughly dispersed~
spraying of this solution onto the sawdust followed by
cooiing and extrusion gave cohesive logs of good fireplace
~i~ performance. Other polymers may be also dissolved in the
hot solution e.g. polyethylene, which acts as a cheaper
` extender for the diene, also gives a more cohesive
~'~,' ' .
structure if added at levels such as to replace 10-50%
~ of the polydiene. Natural rubber or gutta percha, which
;~ are polydienes of high trans configurations, can also be
usFd in a similar manner.
~ Solid solutions such as those described in the
s~ -3~-
::"~
~' ' .. .
,, . . : .... . .
~3246
pr~cedincJ p~racJraoh ccln also be utilized to form
satisf~ctoly logs with reduced contents of cellulosic
material, or even without cellulosic material, since
the polymers will carbonise during combustion 50 as
to release the oil and at the same time provide the
required porous skc~leton. Gutta percha provides
particularly good results under these circumstances.
Edible oils and other animal, fish or
vegetable oils can be retained by mineral oil based
carrier solids, particularly micro-crystalline waxes
at, for example, up to 3~/O by wèight of oil. However,
more cohesive and ~irmer solid solutions can be
prepared by using non-mineral carrier solids such as
carnuba wax, rosins, stearic acid, and linolenic and
. ;, ~
linoleic acid salts.
The solid solutions are prepared by dissolving
the oil in the carrier solid applying heat if necessary.
,
~eutralisation to form a salt, for example, in the case
; - of oleic or linoleic acid may be carried out in
.
~- 20 solution or during preparation of the log mix as
~; described previously. Blends of oleic, linoleic and
linolenic acid with up to 4~/O dissolved oil and when
suitably neutralised and prepared for log manufacture
(mixed with a wicking agent of wood sawdust) make
, excellent logs with good burning properties.
,. .
In some cases, even when all the chemical
modifications discussed above (eg. neutralisation to
minimize coking, acidification to assist degration),
the resultant log continues to burn in an unsatisfactory
manner. Other modifiers can then be employed to overcome
the problem. Typical types of unsatisfactory burning
-39-
., - . .
.
~3'24~
take two oppos ite forms: -
l) Inad~quate Combustion (S3 owne5s in ~,ighting,
Sufoc?tlon or IncomE~ete Co~rbustion~ _
This may be corrected by one or more of the following
means:
(a) Inclusion in the solid fuel of small amounts of
volatile or low flashpoint mater ials . For
example, a log co~prising a fuel of vegetabla
and tall oil pitch hardened with sodium oleate
gave a log which burned with small flames for
an excessively long time. Its burning time ~-
could be reduced by the addition to the hot
fuel solution 5-15% of fuel oil, kerosene,
trioxane or acetic acid. A similar reduction
on buring time and increase in flame heiyht was
,
achieved by adding 5-2~o by weight polyoxyethylene
glycol (paraformaldehyde? to the sawdust before
. ~ . , - :
addition of the hot fuel solution.
(b) Physical changes in the log shape. For example,
- ~ ~ a circular log 2 with a barely adequate burning
:~,
rate was improved by the foxmation of grooves
4 along its length as shown in Figure lA, either
. ~
by cutting or scooping material out of the log
a~ter extrusion or by forming projections 6 in
''`Z~i ~ - .
the extruder barrel 8 as shown in Figure lB.
The flames from ignition spread more rapidly
along the edges of the grooves and dur ing the
.
burn fis~ures developed at the bottom of the
,~ . grooves, allowing faster release of the fuel.
.~ .
;~ This gave more pleasing taller flames and a
shorter burning time. An equally good
- -40-
, . ' ,
. . . . . . . . . ...... . ...
~ .............................. . . - , ~ . .. : . :
324~
~ provem~nt in performa~ce was achieved on a
log ~lhich suffered from suffocation problems
lincornplete combustion due to coke formation)
by formi.ng a hole alony i.ts axi.s as shown in
Figure 2A, using an extruder modification as
shown in Figure 2B, in which a rod 14 was
attached to the extruder screw 16 so as to
extend thxough the barrel 1~
(c) Flaws 20 (see Figure 3A) were developed in logs
22 otherwise similar to those discussed unaer (b)
. . above by insertion in the extruder forming barrel
20 of short pins or rods 24 close to the end of
the barrel as shown in Figure 3B. This gave
.: ~
~, high turbulence pressure points in the barrel
;; where they were situated and as a result, during
:, the fireplace life of the logs they developed
large flaws 20 in the form of cracks at the
~: ~ : location of the pressure points as shown in
i .. ~ '
:: Figure A~ Fuel again was able to escape ~ore
readily through the cracks giving bright tall
,~. ~ . , ~ . . .
flames and complete-combustion~ Cracking was
also successful1y induced using thermally
` expan~ible matexi.als in the mix eg. seeds of
.'
various descriptions such as rice or corn,
encapsulated water, very coarse wood slivers,
and expansible polystyrene beads.
,
. .
.: .,~
~41-
.~'j , . .
;.,
.~..,~
'
.;~,, , ' ' ' ,
, . ..
4~
((3) ~Suhlivi~ion 0~ the ma~-~rial sho~ing cok;ng t~ndenci~s
can l)c acl~ieved by coating pr~sat:urated sawdust with a
non-col;inc3 fuel s~cll as wax. For exa~ple, molasses
pr~hlel~ded with sawdllst is further coated with wax to
ke~p the molasses from forming "coke bridges" across
adjacent particles.
(e) A compatible wetting agent may be added to a fuel
showing coking tendencies, e.g. nonylphenol 10 mol
ethylene oxide in molasses at 0.5-5%, nonylphenol
4-6 mol ethylene oxide in pitches, nonylphenol 3 mol
ethylene oxide in asphalt. ~;
~f) Antioxidants may be added to the fuel showing coking
tendencies e.g. phenol may be added to pitches, fur-
- furyl alcohol or furfuryl aldehyde to molasses.
(2) Bxcessive CombustibilitY (Excessive Flare UP - RaPid
Burninq-Excessively Tall Flames)
Logs made using used and waste oils trapped in a wax
solution initially gave tall flaring flames with a
resulting disappointingly short burn time. The burn
time was extended by the inclusion in the mix of small
~ ~.
~ 20 amounts of fire retardants e.g. 5-20% sodium phosphate,
.
2-8% sodium iodide or chloride, 0.5-7% urea formalde-
hyde resin, 2-8% sodium carbonate, 0.5-4% asbestos
fibre, 0.5-5% melamine resin, 1-12% dicyandiamide or
''
urea.
. .
-~ Whilst synthetic fireplace logs have in the past
.~
generally utilized particulate wood, particularly sawdust,
: ~ .
~ as a carrier for the fuel component, other particles derived
:~
from cellulosic materials may be used. The particles may be
,,,~ .
' . - ~ _
.
1, i
~3;Z~L~
c~ natllral or processed cellulosic materials such as
bagasse, cl-oE~pecl straw, waste paper in pulped, shredded or
flaked forms, spha~num moss, nut shells, coffee groundsJ
fi~rous residues remaining after the extraction of juices
or oils from vegetables and fruit, cotton waste, and bark.
AlternativelyJ particles of regenerated cellulose or
cellulose esters may be utilized, or particles of materials
derived by total or partial degeneration and mineralization
of cellulosic materials such as peat~ lignite and coal.
The state of division of the material should be such as to
permit them to act as a carrier and working agent for the
fuel component. If the material is in the form of fine
fibres or thin webs, then it need not be very finely divided.
Non-cellulosic combustible materials may also be
utilised, such as coal dust, though the lack of absorbency
of the 1atter may be a problem with certain types of liquid
by~product. Soya flour is another combustible material which
may be utilised, and which has a high melting point. It is
also possible to utilise non-combustible solids to provide
the basis of the log skeleton, such a diatomaceous earths,
clays or rock wools, although preferably such non-combustible
materials should not form too large a proportion of the total
weight of the log. Non cellulosic organic fibres may also
be utilised, particularly those that will carbonise at high
temperatures to provide the desired skeleton.
When non-cellulosic materials such as coal dust are
utilised, the coking properties of molasses may be used to
advantage. The ash residue left from a log containing a
substantial amount of mol~sses after all the volatile fuels
are exhausted (flames disappear) i5 a firm cohesive brightly
-43-
,. .
.. . .
3246
glowing block shaped ember not unlike a coal ember. Thisel~ber is attractive and prolongs the aesthetically useful
life of the log by up to 45 minutes. Normally the ash from
synthetic logs has a dull red glow which is at best barely
v:isible. A more important advantage of the coking of
molasses is that it facilitates the use of non-cellulosic
corriers which either will not themselves coke or which will
only coke at high temperatures. For example bituminous
coal dust, anthracite dust5 carbon dust and graphite powders
are useful cheap fuels. However, without a coking binder,
such materials crumble too rapidly during burning. ~olasses
forms the basis of an excellent coking binder for this
purpose and hence a synthetic log based on coal dust or
similar material may be produced.
;; Typical formulae comprise:
(1) Coal Dust70 pts by wt
Molasses50-35 pts by wt
(2) Gas or Oil
j;~ Coke Dust70 pts by wt ~-
` 20 Molasses45-30 pts by wt
These two basic formulae are somewhat soft and the molasses
is solidified by the inclusion of slack waxes of the 778
`~ type in place of part of the molasses (up to 50~/O replacement),
. ; ~
~`, and/or suitable oil soluble emulsifier (e~. nonyl phenol
ethoxylate) may be added at up to 1% to give improved
~ texture. Other heat resistant fuels or polymers may also s
; be used as modifiers, eg. one of the following:
.~
2 - 40 pts lignosulphonate powder
1/2 - 5 pts melamine resin powder
'~ 5 - 40 pts pitches of any or all varieties
, .~ .
~ ~ 2 - 10 pts mimosa or quebracho rosin powder
:. .
~3Z9~;
1/2 - 5 pts Polyethylene, polypropylene>
polyvinyl acetate
1/2 - 10 pts Phe~olic resins
A solid emulsion can be obtain by using water based polymers,
for example the following formùlation gives good results:
Coal Dust 70 pts
U
.: 6~/o U~e~ Formaldehyde
- ~u~ 3-20 pts
res~J
Molasses 15-50 pts
Slack Wax 15-0 pts
Emulsifier 0.25-1 pts
The emulsifier in this case is a water soluble emulsifier
eg. sulphosuccinates, benzene sulphonates, naphthalene
sulphonates.
Polymerisation of the resin is achieved by addition
of conventional acid catalysts eg. phosphoric acid or strong
organic acids such as benzene sulphonic acid or paratoluene
sulphonic acid. The heat resistance of these mixes can be
enhanced by addition of small amounts of melamine, phenol,
resorcinol, furfuryl alcohol, furfuraldehyde, or dicyandiamide.
These reinforcinq agents can be usefully employed at levels
as low as 2% or as high as 30/0 by weight based on ~he weight
. ,~, . .
~ ~ of the urea resin.
.,.
- The cellulosic or other substitute particulate
materials w.ill normally form about 35-4~/O by weight of the
~`j log, although contents in the range 25% to 7~/O by weight are
, ~....................................... .
possible provided that the combustion properties re~uired of
a firelog can be obtained. Moreover, as described elsewhere
:. .
in this disclosure, contents down to zero may be utilized
provided that components are present capable o~ forming an
, . . . .
'; -45-
s `. .
~32~
aclequate s~eleton during combustion of the lo~.
Rec3ardless of the materials utilised to form the
log it is important that whatever constituent of the log
mix which is used to solidify the liquid combustible by-
product is thoroughly blended therewith, so às to achieve
the necessary physical or chemical interaction. This is
particularly so when the liquid by-product is solidified
by dispersion in another material, or by reason of other
material absorbing liquid therefrom.
- 10 The invention is further illustrated by the
following tabulated examples of log formulations. The
ingredients listed in each example under the heading "Formula"
were thoroughly mixed in the order given7 and extruded into
shape o~ a conventional cylindrical log weighing about 3
kg., the combustion behaviour of which was then observed
and is noted under the heading "Burn Comments".
In the burning of logs in accordance with the
` various examples, the burn was considered to last from the
~- time that the log was lighted until the flames died out. -~
:7- ~` 20 For a satisfactory burn, the rate of burning should be ;
~ aesthetically satisfactory through substantially the entire
.
burn once the log i9 fully allght, ie. a cheerful flame
effect should be provided without excessive flaring or flame
height suah as to prejudice safety, the duration of the burn
should be satisfactory, ideally about three hours, the log
! should substantially retain its shape and dimensions,
although some shrinkage will normally occur, and substantially
~ ' the whole of the volatile fuels contained by the log should
,,~ ',~ ,
,~ -46- -
~ , , -,
~3i
3Z~
h~ conc~lmecl. rhe skeleton formed by most of the log
compo~itions described and exempl;fied will be formed largely
of car~on, in which a flameless combustion process will often
contin~le after cornpletion of the normal burn, resulting in
subsequent breakdown of the skeleton into mineral ash.
Ilowever, the log should be formulated so that a-t least 85%
of the total combustible content of the log is consumed
during the burn, including at least 95% and preferably at
least 9~/O of the volatile combustibles. The above
requirements were met by those logs exemplified which were said
to achieve a good or improved burn, or to burn well, very
comfortably met by those which achieved a very good or
excellent burn, and just met by those achieving a fairly
good burn. Those logs which suffocated did not burn well,
and went out before all the volatile combustibles contained
therein were consumed.
.,:,.
.
'~
~-
~ ~20
''~'
;: .
'~
,- .
, , .
,. ~ ,~ . .
-47-
'".'
~ .
'
~".;:`'": ' '
~1' :, . .
Example Formula Burn Comments
-
(1) vegetable pitch 60 pts. suffocated due to coking
(by weight) improved burn with
cocoanut mono- grooves, centre hole or
ethanolamine 3 " induced flaw
sawdust 20 mesh 37 "
(2) vegetable pitch 60 pts. burned well with little
nonylphenol coking, improved with
ethoxylate (50 addition of 6 pts. slack
EtO) 3 " was
sawdust 20 mesh 37 "
(3) vegetable pitch 60 pts. suffocated due to coking
hydrogenated improved burn replacing
glycerides 6 " 20 mesh with 80-100 mesh
sawdust 20 mesh 37 " sawdust or addition of
10 pts. chine clay or
addition of 6 parts mine-
ral wax or addition of 5
pts. SO~ sodium hydroxide
or 6 pts. wax
(4) vegetablepitch 60 pts. suffocated due to coking,
stearic acid 6 " improved as in (3) and by
sawdust 20 mesh 37 " addition of 4 pts. wood
rosin
(5) vegetable pitch 60 pts. good burn
polyglycol ether 3 "
sawdust 20 mesh 37
., . i: '
(6) vegetable pitch 60 pts. fairly good burn improved
refined wax 155F by neutralization with
Mpt 5 " caustic soda or as in (1)
polyethylene 1 "
sawdust 20 mesh 37 "
:~,
~- (7) vegetable pitch 40 pts. coking, burn improved as
sugar 20 " in (1) and~by addition of
I wood sawdust 1/2-5 pts. aluminium sul-
20 mesh 40 " phate or phthalic anhyd-
ride
(8) vegetable pitch 60 pts. good burn
` oleic acid 6 "
`~ 50% caustic soda 3 "
or sodium
carbonate 3
wood sawdust
20 mesh 37 " -
(9) vegetable pitch 60 pts. good burn
~`i polyethylene
glycol solid 3
50~ caustic soda 12
~ wood sawdust 20
;~j mesh 37
. I
-48-
.
i,';' .
1" ~ ' .
Z~
E~ e~_ormula Burn Comments
(lO)tall oil pitch 60 pts. good burn
oleic acid 4~ "
50~0 caustic soda 3
wood sawdust 20
mesh 37 "
(:Ll) vegetable or tall
oil pitch 60 " fairly good burn
wood rosin or some coXing improved by
ester thereof 6 " addition of 3 pts. 50%
wood sawdu~t 20 alkali or 6 pts. wax
mesh 37
(12) vegetable or
tall oil pitch 60 " fairly good burn
mixed fatty acids as (11)
lolei~, lineolic,
linolenic etc.) 6 "
wood sawdust 20
mesh 37 ~'
;, ' '
: (13) 86% molasses 60 " fairly good burn~: polyethylene some coking improved
glycol (solid) 6 " by add~tion of aluminium
wood sawdust 20 sulp~ate (1-3 pts.), or
. mesh 6 pts. wax
(14) 86% molasses 60 " as (13)
~:~ rosin or starch 2
: wood sawdust 20
.. ~ mesh 37 "
(lS) 86~ m~ohlasses 60 ~ good burn, slight coking
xant~um gum 0~3 " reduced by addition o
wooa 20 mesh 40 " 3 pts. slack wax or 3 pts.
nonyl phenol e~hoxylate
. . ~
: (16) 86% molasses 60 " a~ (15)
~ ~ alginate 0~3
t ~: wood 20 mesh 40 "
, . (17) refined para~fin
, wax 140F Mpt 30 " very good burn .
microcrystalline
. 160F Mpt lO "
Iji used engine oil 20
rA~ wood 20 mesh 40
. . (18) pol~butadiene
trans form) 6 " ve~y good burn
~: polyethylene
~: used en~ine oil 53
wood 20 mesh 40
~'' ' ., .
:~ .
~ 49-
.~, .
.. ~ .
.~ .
Ex~p-e Formula Burn com~ents
(19) vegetabl~ acid 30 pts. good burn
blend (oleic~
linoleic and
linolenic)
used cooking oil 30 "
Sodium carbonate 6 "
wood 20 mesh 40 "
~ !
(20) crude cocoanut
fatty acid 30 " good burn
off colour fish
oil 25 "
slack wax 5 "
sodium carbonate 5 "
wood 20 mesh 40 "
- ~ (21) tall oil ~ 30 " good burn, some coking ~ :
'-J slack wax 30 " reduced by additional ~ -
. wood 20 mesh 40 " 1 part sodium carbonate
(22~ tall oil pitch 10 " ~:
: sodium carbonat-e 8
molasses (85%) 20- " - -
slack wax 20 " :
nonyl phenol
ethoxylate (4
~ EtO) 1 "
:~ wood 20 mesh40 " very good burn -~
~ 23) tall oil pitch 10
.: sodium carbonate 8 " . ~ .
,` molasses (85%) 20 "
slack wax 20
~ nonyl phenol :
'''::~! , ethoxylate (4
;. ~ EtO) 1 " :- ;
bagasse (finely
- divided) 40 " very good burn
(24) vegetabIe pit~h 30 " : :
sodium carbonate 6 " :~
para~ormaldehyde 5
molasses 30 " . ~-.
wood 20 mesh40 " very good burn
(25) molasses .25 -"
slacX wax 30
: finely divided :-
~ ~ crushed peanut
!'''', ~ ' 'shells 45 u very good burn .
, i .. . .
.
-50-
~-":
~' ' , ' - ,
. ..
~' ~
. . , , , - ~
~32~i
~ am~le l~rrnul.a s~rn comm nts
- (26) veg~table pitC~I 60 pts,
oleic acicl 6
50~.caustic sod~ 3
coffee yrounds 37 " good burn
(27) vegetable pitch 60
poly~thylene
glycol solid 3 "
50~/0 caustic soda 12
sawdust 20 mesh 18
shredded waste
paper 18 " good burn
(28) sawdust 40 " spongy log but good burn
molasses
. (75% solids)15 "
slacX wax 45
(29) sawdust 10 " firm log, excellent burn
-.: molasses
- (75% solids)25 "
sawdust 30 "
slack wax 35 "
(30) sawdust 10 " very hard log, excellent
: molasses burn
(85% solids)25
:~ 5 awdust 30
~:~ slack wax35 "
;. , .
.. (31) sawdust 10 " hard log, excellent burn
85% molasses 20 ' . } pre mixed ~ : :
~`` saw~ st 30
slack wax 35
(32~ sawdust 10 " firm log, good burn
molasses (75%)30 "
85% phosphoric -mixed in stream
: : acid 3 " -
sawdust 30
` sl~ck wax 30
: (33) vegetable pitch 60
nonyl phen~l
~: ethoxylate (SO
EtO) 3 .
~.~ ` coal dust 37 " good burn
,~ "
~ .
.,
~'' .
~ ~ . 51 `
~-.,, -
~ ' ' .
,
