Lawther, John Mark (Gevninge Bygade 55, Roskilde, DK-4111, DK)
Kvist, Sten (Frostgatan 100, Ödåkra, S-260 35, SE)
Lawther, John Mark (Gevninge Bygade 55, Roskilde, DK-4111, DK)
| 1. | A biofuel mixture comprising starch and cereal husk, characterized in that the starch is present as a flour obtained from wheat, barley, rye, triticale, oat, rice, maize and/or potato, and the cereal husk is obtained from the dehulling of cereal grains such as wheat, barley, rye, triticale, oat, rice and/or maize, wherein the content of starch flour ranges from 20% (w/w) up to 80% (w/w), the remainder being hull for use as a biofuel. |
| 2. | A biofuel mixture according to claim 1 , wherein the content of starch flour ranges from 30% (w/w) up to 70% (w/w). |
| 3. | A biofuel mixture according to claims 1 and 2, wherein the starch flour consists of at least one of the following; wheat, rye, triticale, oat, rice, maize, potato or a mix thereof and is mixed with the cereal husk obtained from wheat, rye, triticale, oat, rice or maize or a mix thereof. |
| 4. | A biofuel mixture according to claims 1 and 2, wherein the starch flour and the cereal husk are obtained from oat. |
| 5. | A biofuel mixture according to claims 14, in which the ash melting temperature is greater than 10000C. |
| 6. | Use of the biofuel mixture according to claims 1 to 5, as fuel for burning, for either direct heat or the generation of electricity. |
| 7. | A process for the production of a free flowing biofuel mixture of starch flour and cereal husk according to claims 14, characterized in that the starch flour obtained from wheat, barley, rye, triticale, oat, rice, maize and/or potato is mixed with the husk obtained from the dehulling procedure of cereal grains such as wheat, barley, rye, triticale, oat, rice and/or maize, using a dry mixer which is optionally then pelleted and/or briquetted and used as a biofuel. |
DESCRIPTION
TECHNICAL FIELD The present invention relates to the development and utilization of a biomass fuel based on specific mixtures of flour and husk from cereal grain.
BACKGROUND OF THE INVENTION Starch rich flour from wheat, barley, rye, triticale, oat, rice, maize and potato is a potentially useful bio-fuel, particularly as it often is a potential bi-product from the production of cereal brans and fibres. The flour has a calorific value consistent with carbohydrate materials, interesting enough as a fuel for burning for the generation of electricity or secondary heat for the warming-up of buildings. However, some starch flours, in particular oat flour has a renowned tendency to clump and cake and pack in silos and related containers, making it difficult to move around and deliver to a burner in a consistent stream. This behaviour is mainly a consequence of its relatively high fat content (6-8%) compared to other flours such as wheat flour. Coincidentally, the fat also tends to become rancid and develop a bitter, off-taste, very quickly, so oat flour has to be heat stabilized prior to use in foodstuffs. This heat treatment destroys structural aspects of the starch granules and severely limits the use of oat flour in foods (eg baked goods), which heightens the need to recover energy from the product.
Cereal husk is generally regarded as a waste material from cereal processing and has few tangible end uses. Relatively high wax and silica contents make it suitable only as a low grade animal feedstuff additive. The material is produced during the standard processing of cereal grain prior to further use of the grain. As with the flour, there is potential to use the husk directly as a bio-fuel for combustion in the generation of heat and electricity. However, two factors make the material a low-quality fuel:
1. The relatively high silica content results in a fairly high ash residue and to date use as a fuel is limited. 2. The low bulk density and coarse nature of the material makes it difficult to move around.
A blend with starch flour improves this situation dramatically: the overall silica content of the mix is satisfactory, and the flow properties and bulk density of the flour provides a blend which is good.
Flour rich in starch can also be used as a feedstuff for husbandry animals, such as in particular horses and pigs. However, such flour normally needs to be supplemented with different feed additives to make up a complete fodder. Such fodders are normally produced from different ingredients stored in different storing vessels, such as silos, whereupon the ingredients are fed to a mixer. The problem is then to feed the cereal, and the oat meal in particular, in a satisfactorily, non-disturbing way, as it as mentioned above, tend to cake and become non- flowing.
The present invention discloses a process in which the husk of cereal grain is mixed into the flour in proportions ranging from 30% (w/w) husk/70% (w/w) flour (dry matter basis) to 70% (w/w) husk/30% (w/w) flour, producing an excellent, free-flowing product.
In particular, the mixture has overall low silica content with a fairly low ash yield, making it an excellent bio-fuel.
SUMMARY OF THE PRESENT INVENTION It has now been discovered that a free-flowing bio-fuel mixture can be produced by mixing the husk of cereal grain into the flour in proportions ranging from 30% (w/w) husk/70% (w/w) flour (dry matter basis) to 70% (w/w) husk/30% (w/w) flour.
In this description, starch flour is the starchy endosperm material obtained from the dry milling of previously de-hulled cereal grain or potato flour. Cereal husk is the material recognized by cereal millers as the coarse hulls removed from the grain using standard de-hulling equipment. Cereal grain is routinely de-hulled in such a manner, prior to further processing.
In one preferred embodiment of this invention the grain is oat wherein the oat flour is blended with husk, preferably oat husk removed from oat grain during a standard de-hulling operation, to produce a free-flowing bio-fuel with an energy value between 4000 and 4100 Kcal/kg (17- 18.5 MJ/kg; 4.7-5.1 MWh/ton).
The material is a far more suitable fuel than either of the starting materials from two main standpoints: it is relatively easy to move around because of its improved flow characteristics and the level of ash (between 2% and 5%) is acceptable for utilization in many types of burners for energy generation. Furthermore, the ash melting temperature in the mix is more than 12000C, as opposed to under 6000C for the flour alone. This is very advantageous, as low temperature melting ashes can be a real problem in many types of bio-fuel burners.
DETAILED DESCRIPTION OF THE INVENTION The inventors have developed an excellent free-flowing biomass fuel based on a mixture of starch-rich flours dry-milled from cereal grains or obtained from potatoes, and the husk removed from grain, and a process for the production of such a bio-fuel. The fuel is ideal for burning in that it has a calorific value characteristic of many carbohydrate and lignocellulose materials, much improved flow and handling characteristics as compared to the original flour and husk raw materials. Additionally, the ash melting temperature of the mixtures (more than 12000C) is very favorable for a bio-fuel intended for many standard burners.
The invention is characterized in that the flour dry-milled from de-hulled cereal grain or potato flour is combined with the cereal-hulls, removed from cereal grain using a de-huller, in a dry- mixer of the type or any such other suitable dry-mixing set-up, in the proportions ranging from 20% (w/w) husk/80% (w/w) flour (dry matter basis) to 80% (w/w) husk/20% (w/w) flour, preferably the range 30% (w/w) husk/70% (w/w) flour (dry matter basis) to 70% (w/w) husk/30% (w/w) flour. The free-flowing material generated by the mixing of the components can then be optionally formed into pellets and/or briquettes, or be used directly in the loose particulate form emanating from the mixing stage.
The material in any of the forms, i.e. free-flowing particulate, pelleted or briquetted can then be used as a fuel in most types of burners, either for the production of direct heat, or for the generation of electricity.
The material may also be used as feedstuff for husbandry animals, such as in particular horses and pigs, supplemented with different feed additives to make up a complete fodder. DESCRIPTION OF THE PREFERRED EMBODIMENTS
Example 1 1000 kg Oat grain was de-hulled using a Buhler de-huller system. This yielded 306 kg of hull and 690 kg of grain. The resulting grain was then dry-milled on a short-flour milling system. This yielded 312 kg of a fine, endosperm rich flour fraction and 375 kg of a more coarse bran rich fraction.
The flour was then mixed with the hull in the proportions 1 part flour to 1 part hull (25 kg + 25 kg), on a dry weight basis, using a dry mixer. The resultant mix was observed to have improved flow properties compared to either the flour, which tends to clump and cake, or the hull, which is very coarse.
The fuel value of the material was assessed using calorimetric techniques and the following results were obtained:
The mixture had a measured ash content of 3.6%. The measured ash melting temperature was greater than 14000C. That of the flour alone is under 600°C. Example 2 A further portion of the flour prepared as in example 1 above, was mixed with the hull, also as prepared in Example 1 above, in the proportion 30% flour: 70% hull (6 kg flour + 14 kg hull), on a dry weight basis, using a dry mixer. Again, the flow properties and the handling of the mixture were observed to be far superior to those of either starting material.
The fuel value of the material was assessed using calorimetric techniques and the following results were obtained:
The mixture had a measured ash content of 4.6%. The measured ash melting temperature was again greater than 14000C.
Example 3 A yet further portion of the flour prepared as in Example 1 above, was mixed with the hull, also as prepared in Example 1 above, in the proportion 70% flour:30% hull (14 kg flour + 6 kg hull), on a dry weight basis, using a dry mixer. Once again, the flow properties and handling of the mixture were observed to be far superior to those of either starting material. The fuel value of the material was assessed using calorimetric techniques and the following results were obtained:
The mixture had a measured ash content of 2.4%. The measured ash melting temperature was again greater than 14000C.
The husk material normally has a size of 1 to 10 mm, whereby oat husk has a size of 2 to 7 mm. It means that any similar straw material can be used and mixed with a pulverulent starch material after having been milled down to a size of 1-10, preferably 2-7 mm. Thus the term husk herein also includes straw material so milled.