GB2260336A

GB2260336A - Artificial or simulated solid fuel material

Info

Publication number: GB2260336A
Application number: GB9121444A
Authority: GB
Inventors: William Robertson Cunn Erskins
Original assignee: Shimada
Current assignee: Shimada
Priority date: 1991-10-09
Filing date: 1991-10-09
Publication date: 1993-04-14
Anticipated expiration: 2011-10-09
Also published as: GB2260336B; GB9121444D0

Abstract

A substantially incombustible simulated fuel element comprises 30-90% by weight of a crystalline, metamorphic rock. eg slate, from 10-40% by weight of carbonaceous material, eg charcoal, and up to 20% of an inorganic binder, eg silane or silicate, with the balance as necessary being inert inorganic material or incidental impurities. In the manufacture of the element, the constituents, having a moisture content below 10%, are mixed to a substantially homogeneous mass.

Description

Artificial or Simulated Solid Fuel Material The present invention relates to a substantially incombustible artificial or simulated solid fuel material based on a flame resistant non-consumable substrate which may be shaped to provide briquettes, or lumps as a charcoal substitute for use in gas or electric barbecue grills or as simulated fuel elements e.g. representing natural coal for gas fuelled domestic fires and the like. The nature of the artificial fuel product and its process for production thereof provides for a variety of shaped forms including for example charred log shapes.Although the said artificial element contains some combustible components e.g. for smoke flavouring purposes in its use in barbecues, the selected substrate is flame resistant and the artificial fuel element formed therefrom is thus very durable and will not be consumed by prolonged application of a flame. On removal of the flame source the substrate does not support combustion and therefore is immediately self-extinguishing. Unlike many known charcoal substitutes, the fuel element of the present invention does not form ash when in use with gas burners. It is also water resistant and in contrast to some leading commercially available synthetic barbecue briquettes will not disintegrate if soaked.

The preferred application of the invention is in providing charcoal substitutes for barbecues and to this end the artificial fuel element of this invention comprises substantially incombustible material, a binder and combustible carbonaceous and aromatic material which provides flavouring characteristics which will be absorbed by food cooked in the barbecue.

The conventional grills commonly use "charcoal briquets1' to cook various kinds of foods by way of the grills being placed over a bed of these known charcoal or charcoal and wood briquets. The wood, in the form of sawdust, within the briquet imparts an aromatic smell and flavour to the food being cooked.

Conventional briquets are mainly combustible but tend to form ash as they burn and are not suitable for use in gas or electric grills because this would be detrimental to the burners of gas-barbecue grills necessitating inconvenient cleaning operations to prevent clogging and failure of the burners. There are also briquets consisting of "lava rock" and some combustible material which have been proposed as charcoal substitutes. This so called "lava rock" is basically formed from igneous rock and so does not form ash on application of a flame and will last indefinitely under barbecue cooking conditions. Such briquets thus consist essentially of a clay type carrier and a combustible flavour producing agent.However, otherwise, in the process of barbecuing, the only flavour to be added to the cooking food is that of smoke or the vapours produced by fats of the meat which fall through the grill onto the briquets and are vaporised.

Thus although it is known to use "lava rock" in place of charcoal briquets because of its non-shedding character to avoid ash formation during barbecue cooking that material is not entirely acceptable because it lacks any flavouring capacity for meats or other foods being cooked on the barbecue grill. Furthermore the cost of transporting volcanic rock for such use is a disadvantage.

Most recent proposals for production of fuel briquettes for barbecues etc as described in the patent literature suggest the use of clays as a carrier. For example US Patent No. 4,167,398 discloses a charcoal briquet utilising an inexpensive binding substrate consisting of sodium bentonte clay and a water soluble acid polymer which makes up 1-10% of the charcoal briquet. Also US Patent No. 3,405,599 discloses the use of bentonite clay which makes up 3-4% by weight of a rapid ignition charcoal briquet to act as a retarder to prevent the briquet from burning too rapidly after ignition or from igniting spontaneously. That material contains hickory essence for flavouring purposes.

Another proposal is set forth in US Patent No. 3,689,234 which discloses an instantly ignitable charcoal briquet utilising 8-12% weight of clay such as bentonite, kaolin and the like, again used as a retarder to regulate the ignition of the charcoal briquet. Use of clay in a charcoal briquet is also disclosed in US Patent No. 3,402,033 wherein 1-15% by weight of a non-hydratable clay. More recently EP-A-0281370 describes a briquet for gas and electric grills which also uses a high percentage of clay (30-80% by weight) as a carrier.

A commercially significant problem with use of clays lies in the expense of that material. Therefore an object of the present invention is to provide a cheaper alternative to clay based products and to otherwise provide improvements in charcoal substitutes for use in gas or electric barbecue grills. It is also an object of this invention to provide a realistic simulated fuel element for use in gas-fuelled fires e.g. open hearth fires or the like domestic heating appliances.

According to this invention there is provided a substantially incombustible simulated fuel material element comprising 30-90% by weight of a crystalline, metamorphic rock and from 10-40% by weight of carbonaceous material (preferably of up to 80% carbon content) up to 20% of an inorganic binder, with the balance as necessary being inert inorganic material or incidental impurities.

The substantially dry composition preferably comprises from 50-80% metamorphic rock, 15-30% carbonaceous material and not less than 5% inorganic binder. More preferably the composition comprises from 65-75% metamorphic rock, from 1525% carbonaceous material and about 10% inorganic binder with the balance as necessary being inert inorganic materials.

Preferably the crystalline metamorphic rock is slate with a typical density range of from 2.7-2.85 g/cm3 and about 4% porosity. Advantageously the slate is used in the form of slate sand and is selected from the group consisting of chlorite, micas, quartz, hematite and mixtures thereof.

Further according to this invention there is provided a process for producing an artificial or simulated fuel material comprising mixing a particulate metamorphic rock (about 60% silica) and a carbonaceous material (of up to about 80% carbon) with an inorganic binder (about 80% solids mainly as silicates), the mix having a low moisture content of say less than 10% and continuing mixing for a sufficient period of time to achieve a substantially homogeneous mass, observable by a change to a plastic or doughy consistency. The preferred particle size for the rock is such as to allow passing through a sixteenth screen and more particularly the following sieve analysis is representative of a suitable starting slate sand.

BS Sieve Size (mm) % by mass passing BS Sieve 10 100 5 89-100 2.36 60-100 1.18 30-100 0.600 15-100 0.300 5-70 0.150 0-20 0.075 0-15 The preferred amounts to be mixed are 30-90%, preferably 50-80%, more preferably about 72% by weight of the crystalline, metamorphic rock with from 10-40%, preferably 1530% by weight of the carbonaceous material, more preferably about 20% as mixed sawdust and charcoal fines, with up to 20%, preferably about 8-10% of an inorganic binder the balance if any being incidental inert inorganics or impurities.

Preferably the binder is a silicate binder such as water glass present in an amount of from 8-10%. However it may be formed of silanes or other silicate based liquid binder.

In accordance with the present invention, the applicant also provides a simulated fuel material by forming the said mixed homogeneous material to a shape e.g. by extrusion and cutting as required to provide a briquet, brick, twig, log, or lump wood charcoal or coal lump shape. The thus formed and set simulated fuel material has a ceramic character which means it is extremely durable and heat resistant.

Environmental and commercial advantages arise from use of slate since it is generally available in countries already using charcoal for barbecuing so it would be easily available and prevent stockpiles appearing at slate quarries.

Incidentally there is nothing to prevent certain slates being heat treated and comminuted to acceptable particle sizes if the local "waste" slate is not available in sufficient quantity or size.

An example of the process for producing a simulated fuel briquet of the invention will now be described for the purposes of illustrating the invention further.

The following components are added to a shear mixer to provide a mixture of (% by weight): 72% slate of particle size to pass a sixteenth screen 10% sawdust (oak) 10t charcoal made from pyrolised sawdust (oak) comprising about 78% carbon, thorough mixing for perhaps about 10 minutes or so when the inorganic binder, 8-10% soluble sodium silicate is added and mixing is continued till the powder/binder mass becomes a plastic doughy homogeneous mass which depending on the quantity mixed and power of mixer may occur within 35-40 minutes but may be achieved in less time if a more powerful or high shear mixer is used.

Once the mixture has reached the plasticity stage it is fed into a roller press to obtain "egg" -shaped barbecue briquettes, although it may be extruded to form other shapes such as shapes resembling lumps of charcoal or coal pieces.

These further shapes of fuel material can be used as simulated fuel materials for gas fires and flame effect displays.

Sodium silicate or water glass as it is sometimes known, forms the preferred binder in the mix and is composed of 12% Na2O and 30% Sio2. This has been found to confer ideal properties on the subsequently extruded mixture to provide a simulated fuel briquet capable of retaining its structure at the temperatures typical of barbecuing. With continued use the fuel briquet containing the binder appears to form a ceramic shell mimicking well used charcoal very well.

The amounts of the substances added to the mix vary as the product has to change as to country habits. The sawdust can be doped with different amounts of dried herbs such as Rosemary, Thyme, Bay leaves and such like. The artificial or simulated fuel material of this invention prevents the known problem of flaring and residual burning of sawdust or herbs because of its homogeneous nature and confinement of such material in an incombustible substrate which extends the effective lifetime for flavouring effects of these materials on the barbecue allowing slower release and better usage.

Once the carbonaceous material of the fuel material has been burnt off only a hard ceramic shell remains. This ceramic shell will no longer be able to impart aromatic smell and flavour to the food being grilled but will still serve as a conventional lava rock-type heat retaining briquet. In this form it will still provide some amount of flavour to the food being cooked due to the fats from the meat being vaporised into a smoke.

The most important advantage of the artificial fuel material of this invention is that it is extremely durable being based on a substantially incombustible non-consumable substrate consisting mainly of inorganically bound slate powder thus saving the use of valuable clays typical of the prior art. A further advantage of the invention is that ability to utilise a waste material, slate sand, which is often stockpiled at slate quarries and presents difficulties in disposal thereof.

Claims

1. A substantially incombustible simulated fuel material comprising 30-90% by weight of a crystalline, metamorphic rock and from 10-40% by weight of carbonaceous material (preferably of up to 80% carbon content) up to 20% of an inorganic binder, with the balance as necessary being inert inorganic material or incidental impurities.

2. A simulated fuel material according to claim 1 comprising as a dry composition from 50-80% metamorphic rock, 15-30% carbonaceous material and not less than 5% inorganic binder with the balance as necessary being inert inorganic materials.

3. A simulated fuel material according to claim 1 comprising 65-75% metamorphic rock, from 15-25% carbonaceous material and about 10% inorganic binder with the balance as necessary being inert inorganic materials.

4. A simulated fuel material according to any one of the preceding claims wherein the crystalline metamorphic rock is slate with a density range of from 2.7-2.85 g/cm3 and about 4% porosity.

5. A simulated fuel material according claim 4 wherein the slate is selected from the group consisting of chlorite, micas, quartz, hematite and mixtures thereof.

6. A simulated fuel material according to any one of the preceding claims, wherein said carbonaceous material is selected from the group consisting of charcoal, pyrolised sawdust and mixtures thereof.

7. A simulated fuel material according to claim 6 wherein said charcoal is made from pyrolised sawdust.

8. A simulated fuel material according to claim 7, wherein said charcoal contains at least 78% carbon.

9. A simulated fuel material according to claim 6 wherein said carbonaceous material contains a herbal or aromatic flavouring.

10. A simulated fuel material according to claim 9 wherein said flavouring is a selected sawdust, wood chip or particle.

11. A simulated fuel material according to claim 10 wherein said flavouring is of wood selected from the group consisting of oak, hickory, mesquite, maple, alder, cherry, and sassafras.

12. A simulated fuel material according to claim 9 wherein said flavouring is sawdust packed with dried herbs.

13. A simulated fuel material according to claim 9 wherein said flavouring is selected from the group consisting of Rosemary, Thyme, Bay leaves, spice hulls, nut shells and spices.

14. A simulated fuel material according to any one of claims 1 to 9 comprising at least 72% by weight of slate, 20% by weight of carbonaceous material and 8% inorganic binder.

15. A simulated fuel material according to claim 14 where said carbonaceous material is made up of about 10% by weight of charcoal and about 10% by weight of sawdust packed with an aromatic flavouring agent.

16. A simulated fuel material according to any one of wherein said binder is selected silanes or silicates.

17. A simulated fuel material according to claim 16 wherein said binder is sodium silicate.

18. A process for producing an artificial or simulated fuel material comprising mixing a particulate metamorphic rock and a carbonaceous material with an inorganic binder, the mix having a low moisture content of less than about 10% and continuing mixing for a sufficient period of time to achieve a substantially homogeneous mass, observable by a change to a plastic or doughy consistency.

19. A process according to claim 18 wherein said mixing is carried out in a high-shear mixer.

20. A process according to claim 18 or claim 19 wherein the particulate metamorphic rock and a carbonaceous material are mixed for about 10 minutes before adding the inorganic binder and further mixing is carried out for from 35 to 45 minutes or longer.