GB2262536A

GB2262536A - Combustible wood product

Info

Publication number: GB2262536A
Application number: GB9220907A
Authority: GB
Inventors: David Jones
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-12-16
Filing date: 1992-10-05
Publication date: 1993-06-23
Anticipated expiration: 2012-10-05
Also published as: GB2262536B; GB9126676D0; GB9220907D0

Abstract

Controlled distillation of softwood timber sticks in the presence of a restricted supply of oxygen removes water, alcohol and other volatiles boiling at less than about 110 DEG C at ambient temperature, and is terminated while the sticks remain intact with a substantially cellulosic molecular structure. The processed sticks are resistant to crumbling and gold yellow to pale brown in colour, and contain at least 4% by weight of oils and resins boiling at at least 120 DEG C at ambient pressure. As exemplified the distillation involves raising the temperature of a distillation vessel slowly from 40 - 110 DEG C over fifteen hours and thereafter increasing the temperature to about 120 DEG C over thirty minutes.

Description

wood Product The present invention is concerned with wood products and in particular, wood distillation products.

The controlled pyrolysis of wood to charcoal has been knout since time immemorial. The charcoal process involves expulsion and combustion of volatiles, and conversion of cellulose to substantially pure ( > 99%) carbon, under conditions of restricted access to oxygen to avoid combustion of the carbon. Also known since ancient times are processes of wood distillation in which the object is to produce valuable chemicals, such as methanol, acetic acid, turpentine, rosin and the like.

Gums and resins like turpentine and rosin are typically present in softwoods (coniferous woods) in amounts up to 6 to 10 < c, whereas in hardu-ood (deciduous or broadleafed woods the proportion of gums and resins is typically only 1 to 3%. Charcoal is therefore normally made commercially from hardwoods in order to avoid the protracted processing needed for producing charcoal from softwoods.

Softwoods are also commonly destructively distilled to extract products such as turpentine, rosin, rosin oil, pine oil, pine tar and pitch, the residue being charcoal.

FR 2512053 is concerned with roasting of ligneous materials wherein fragmented ligneous starting materials are roasted at a temperature of 200 to 280t'C to produce a product with a substantially intact cellulosic structure and increased exothermic value. The product is distinguishable from both wood and charcoal.

The process disclosed by FR 2512053 may be used for roasting an extremely wide range of ligneous starting materials. The specification teaches that wood, bark, sa xdust, rice balls. nut shells, kernels, straw and flax are all suitable starting materials.

There is no clear statement of preferred ligneous starting material; the only starting materials exemplified are oak (a hardwood) and saudust. There is no hint or suggestion tat the use ot softwood might be advantageous, or of a lox: temperature distillation process.

I have now developed a method of low temperature distillation which utilises softwoods as a starting material, and have found that it is desirable for some purposes to stop the distillation of softwoods at an early stage, when substantially all the water has been removed .

According to a first aspect of the invention therefore, there is provided a method of distillation of a plurality of sticks (typically logs, split wood or planks) of softwood timber, which comprises controlled distillation of said sticks in the presence of a restricted supply of oxygen so as to substantially remove water, alcohols and other volatiles boiling at less than about 110 C at ambient pressure, and terminating said distillation such that the processed sticks remain intact with a molecular structure substantially in cellulose form such that the bulk of said processed sticks is resistant to crumbling and gold yellow to pale brown in colour, said processed sticks containing at least 4% based on the weight of the sticks, of oils and resins boiling at at least 1200C at ambient pressure.

A method according to the present invention is a relatively slow distillation process which allows an equilibrium to be established within a distillation vessel and thereby produces a substantially homogeneous product which differs from that obtained a roasting process as described by FR-2512053.

If the distillation according to the present invention is taken further, there arises a product of higher calorific value, but the cellulosic molecular structure is impaired and the loss of the natural oils impairs the flammability of the processed sticks.

The product of the method just described is highly combustible and burns with a smokeless yellow flame in a manner similar to charcoal soaked in turpentine (although, of course, the product according to the invention retains its structural integrity, which is, of course, a significant difference relative to turpentine-soaked charcoal).

It is further preferred that the method involves splitting of the processed timber sticks, such that the resultant product comprising a plurality of sticks each having a maximum thickness of less than about 2cm, and preferably of thickness of about 0.5cm.

The softwood sticks used as starting material in a method according to the present invention are typically logs, planks or split wood having diameters of up to about locum and lengths in the range of 150 to 200cm. Such softwood sticks would not be suitable to be used in a method as disclosed by FR 2512053, as such a method uses a preferred starting material comprising a fragmented ligneous material.

The present invention therefore further comprises a combustible product conaprising, a plurality of sticks of softwood, said softwood of said product retaining its structural integrity and comprising a cellulosic molecular structure, being substantially free of moisture, alcohol and other volatiles boiling at less than about 110"C at ambient pressures, and containing at least 4% of oils and resins boiling at at least 1200C at ambient pressure.

The oils and resins generally comprise turpentine or rosin (a principal constituent of which is abietic acid and its anhydride) as well as rosin oils, pine oils dipentenes, and the like natural oils and resins.

The plurality of sticks of the combustible product according to the invention each typically have a maximum thickness of less than about 2cm, preferably about 0.5cm, and are preferably provided in sealed, substantially waterproof packaging comprising sheet or tilt material (such as plastics bags or sacks!. The product, which has an appreciably higher calorific value than the air-dried wood, is useful as a firelighter material because it is easily ignitable ard sustains a regular flame.

The present invention therefore further comprises a method of ignition of carbonaceous material (such as charcoal, coal or the likei which comprises igniting the product according to the invention with discrete sticks of said product arranged around said carbonaceous material.

The softood used in the method according to the invention mav be European larch Noruetian spruce, Scots pine or the like. The distillation may be effected in distillation vessels such as charcoal kilns. distillation units, or oil baths. in the latter case direct contact between the timber and oil is substantially obviated. Heating is gradual during the distillation, with restricted access to air so as to preclude flame generation. degradation or des+rilctive distillation of the soft!ood.

During a first distillation stage of the method according to the present invention, the operating temperature of the distillation vessel is slowly raised from 40 to 110"C over a period of about fifteen hours in order to drive off water and softwood volatiles boiling at less than 110"C at ambient pressure.

Following the first distillation stage, the operating temperature is further raised for about thirty minutes until a temperature of about 1200C is attained, when a yellow distillate characteristic of a product according to the present invention is observed. The distillation is terminated on observation of the yellow distillate to ensure that the resultant product contains at least 4% by weight of the natural oils and resins boiling at at least 1200C at ambient pressure.

Claims

CLALNIS:

1.A method of distillation of a starting material comprising a plurality of sticks of softwood timber, which comprises controlled distillation of said sticks in the presence of a restricted supply of oxygen so as to substantially remove water, alcohols and other volatiles boiling at less than about 110 C at ambient pressure, and terminating said distillation such that the processed sticks remain intact with a molecular structure substantially in the form of cellulose and that the bulk of said processed sticks is resistant to crumbling and gold yellow to pale brown in colour, said processed sticks containing at least 4%, based on the weight of the sticks, of oils and resins boiling at at least 120"C at ambient pressure.

2. A method according to claim 1, wherein said starting material comprises a plurality of softwood timber sticks, each having a diameter of up to 10cm and a length in the range of 150 to 200cm.

3. A method according to claim 1 or 2. which comprises splitting of the processed sticks, such that the split product comprises a plurality of sticks. each having a maximum thickness of less than about 2cm.

A. A method according to claim 3, wherein said split product comprises a plurality of sticks each having a maximum thickness of about 0.5cm.

5. A method according to any of claims 1 to A, which comprises a first distillation stage wherein the temperature of a distillation vessel is raised from about 40 C to 110 C over a period of about fifteen hours.

6. A method according to claim 5, wherein the temperature of said distillation vessel is further raised to about 120 C over a period of about thirty minutes, following said first distillation stage.

7. A method according to any of claims 1 to 6, wherein said distillation is terminated on observation of a yellow distillate.

8. A method according to any of claims 1 to 7, wherein said softwood comprises European larch, Norwegian spruce or Scots pine.

9. A combustible product comprising a plurality of sticks of softwood, said softwood of said product retaining its structural integrity and comprising a cellulosic molecular structure, being substantially free of moisture, alcohols and other volatiles boiling at less than about 110 C at ambient pressures, and containing at least 4% of oils and resins boiling at at least 1200C at ambient pressure.

10. A product according to claim 9, wherein said oils and resins comprise one or more of turpentine, rosin, rosin oils, pine oils and dipentenes.

11. A product according to claim 9 or 10, wherein said plurality of sticks each have a maximum thickness of less than about 2cm.

12. A product according to claim 11, wherein said plurality of sticks each have a maximum thickness of about 0.5cm.

13. A sealed pack comprising substantially waterproof sheet or film material containing therein a product according to any of claims 9 to 12.

14. A method of ignition of carbonaceous material which comprises igniting a product according to any of claims 9 to 12 with discrete sticks of said product arranged around said carbonaceous material.