Field of the invention

The present invention relates to an alternative fuel from waste materials for co- combustion with coal in a coal fired power plant, which fuel has low C<¾ emission compared to coal. More particularly the present invention relates to an alternative fuel from waste materials including waste oils and other industrial by-products, suitable for co-combustion with coal in a coal fired power plant to reduce CO ₂ emissions of coal fired power plants while retaining combustion efficiency.

Background

Most of the world's current electricity requirements are derived from fossil fuel power stations, which burn fossil fuels such as coal, oil and natural gas. Heat generated from combustion of coal for example produces, inter alia, steam which is used to drive turbines that produce electricity.

Coal is predominantly used in power stations, compared to natural gas and oil, to generate electricity because of its relatively low cost. Coal generated electricity is used for many applications including lighting, heating, cooling, cooking, industry and farming.

During the process of producing coal generated electricity, flue gas from combustion of the coal is discharged to the air; this contains CQz and water vapor, as well as other substances such as N ₂ , nitrogen oxides, sulfur oxides, fly ash, mercury and traces of other metals. These emissions can lead to smog, acid rain, and haze. In addition, these power plant emissions increase the risk of climate change.

Attempts have been made to reduce flue gases such as N ₂ , nitrogen oxides, and sulfur oxides. Some attempts have included providing smoke stack exhaust of power plants with a scrubber. In the scrubber, a cloud of fine water droplets is mixed with crushed limestone, which reacts with the sulfur and pulls it out of the exhaust. A side effect of this is the formation of gypsum.

Coal fired power plants also produce solid waste ash from coal-fired boilers which must be removed. Roughly 80% of the waste ash falls into an ash hopper, but the rest of the ash is carried into the atmosphere to become coal-fly ash. Particulate matter from coal- fired plants can be harmful and have negative health impacts. Studies have shown that exposure to particulate matter is related to an increase of respiratory and cardiac mortality. Particulate matter can irritate small airways in the lungs, which can lead to increased problems with asthma, chronic bronchitis, airway obstruction, and gas exchange. One method of helping to reduce the particulate matter emissions from coal- fired plants includes an electrostatic precipitator.

While post combustion methods and apparatuses attempt to reduce solid ash content and discharge of substances such as N ₂ , nitrogen oxides, and sulfur oxides, coal fired power plants remain the major emitters of C0 _2j a greenhouse gas which according to general consensus is a contributor to global warming over the last 100 years.

The current standing of global C0 ₂ emissions shows the power sector is still using coal in very substantial quantities due to its relatively low cost. As a consequence greenhouse abatement targets are now a major issue at environmental forums around the world focussing attention on existing problems. However the analysis of test data shows that the world still has a long way to go on curbing emissions growth.

Several methods exist to improve the efficiency of fossil fuel power plants. A frequently used method is to convert an existing power plant to run on a different fuel. This includes conversions for the use of biomass waste. While conversions to biomass waste- fired power plants have the benefit of reducing landfill, the cost of conversion can be very high. A typical co-firing installation includes modifications to the fuel-handling and storage systems and possibly the burner to accommodate biomass. Costs can increase significantly if wood needs to be dried, size needs to be reduced, or the boiler requires a separate feeder. In addition, the incentive to use coal remains high because coal reserves are abundant which effectively keeps the cost of electricity for industrial and domestic use at a reasonably low level hence coal is still preferred. Carbon capture and storage (CCS) of emissions from coal fired power stations is another alternative but the technology is still being developed and will increase the cost of fossil fuel-based production of electricity. CCS may not be economically viable, unless the price of emitting C0 ₂ to the atmosphere rises. Hence it would be

advantageous to provide an alternative fuel which substantially avoids the need for plant conversion but which helps to minimise C0 ₂ emissions whilst retaining current economies of scale.

It is known that in some instances coal fired power stations have been directed to close down by local governments because of adverse C0 ₂ emissions. This type of closure however has an immediate economic flow through effect on employees of the power station and local communities. Hence it would be a clear advantage to provide a fuel which can be burned with coal in existing power stations with concomitant low C02 emission, low ash content while maintaining combustion efficiency and cost effectiveness associated with coal.

Alternative sources of electricity to fossil fuel power plants include nuclear and other forms of renewable energy including solar, wind, hydroelectric and geothermal.

However coal fired power plants for example remains attractive due to their low initial capital costs and abundance of coal reserves.

In view of

(i) global warming continuing,

(ii) the increasing attention being given to C0 ₂ emissions from the burning of fossil fuels such as coal,

(iii) the expense and inefficiency of alternatives and conventional techniques for capturing carbon dioxide emissions, and

(iv) immediate economic concerns stemming from closing down power stations, a need exists for a recuperative and conductive heat transfer technique which reduces C0 ₂ emissions resulting from the burning of coal at power stations.

It is therefore an object of the present invention to provide an alternative fuel for replacing coal or at least for co-combustion with coal to reduce C0 ₂ emissions substantially without the need for power plant conversion. Summary of the invention

In the present invention there is disclosed a fuel composition for co-combustion with coal in a coal fired power station, the fuel composition having substantially reduced C0 ₂ emissions while retaining combustion efficiency, and including:

a predetermined amount of a waste oil; and

an effective amount of a cellulose material to absorb the predetermined amount of waste oil;

wherein when the composition is subject to combustion the composition exhibits a C0 ₂ emission of less than about 2%, an S0 ₂ emission of less than about 0.2% by weight, an ash content of less than about 1% by weight, and a net calorific value of greater than about 25 MJ g. .

The fuel composition of the present invention can be efficiently burnt with coal in an exiting power station to generate electricity cost effectively while significantly lowering carbon emissions.

The present invention therefore represents a significant improvement in reducing flue gas emissions in coal fired power stations. In particular co-combustion of coal with the composition of the present invention has the effect of reducing C0 ₂ emissions, reducing ash content and other substances such as N ₂ , nitrogen oxides, sulfur oxides, while the energy produced from combustion of the composition in the form of heat is at least equal to the heat produced by burning coal.

The instant fuel composition can be used as an effective fuel substitute for coal or in co- combustion with coal while substantially minimizing:

(i) C0 _2j S0 ₂₎ and nitrogen oxides emissions, and

(ii) Ash residue

without the requirement for conversion in a coal fired power plant.

A further advantage of the present invention is that co-combustion of the composition with coal produces heat of combustion equal to or greater than that produced by combustion of coal. An even further benefit of the instant invention is that waste materials are used including waste oil, and cellulose, which would otherwise go to landfill. A further economic advantage is achieved to local communities and power plant employees by co-combustion of coal with the present invention because reduced carbon emissions may prolong usefulness of coal fired power stations.

The cellulose material can be reclaimed MDF (rMDF) . It is preferred that the rMDF is pre-treated with a water resistant material.

The waste oil can be selected from a range of sources including spent motor oils, spent aviation fuels, spent marine fuels, lubricants, vegetable oils, animal fats, municipal waste, camellina, algal oil, sewage sludge, babasu, cooking oils, fuel oils and the like.

In a related aspect of the present invention there is disclosed a solid fuel composition for co-combustion with coal in a coal fired power plant, the composition including:

a waste oil such as engine oil, present in an amount of between about 10 to 20% by weight;

a cellulose material capable of absorbing the waste oil, wherein the cellulose material is present in an amount of about 80 to 90% by weight;

wherein when the composition is subject to combustion the composition exhibits a C0 ₂ emission of less than about 2%, an S0 ₂ emission of less than about 0.2% by weight, an ash content of less than about 1% by weight, and a net calorific value of greater than about 25 MJ/Kg.

The fuel composition can further include an effective amount of a material or mixture of materials selected from grasses, plants (including extracts derived therefrom), trees, animal waste, algae, hemp, coconut, rice husks, and corn. In one embodiment the material can include a mixture of mallee grass and timber pulp such as sawdust. In an alternative embodiment the material can be selected from one or more of maize, wheat, reed canary grass, Jerusalem artichoke, sunflower, potatoes, barley, sugar beets, switchgrass, mallee eucalypts, hybrid poplar, willow, cottonwood, sycamore, canola oil, animal fats (such as tallow), recycled grease, fungus, pongamia pinnata, dryland juncea, kudzu, giant miscanthus, phragmites australis, arundinella nepalensis, themeda avenacea, jatropha curcus, yeast, sugar cane, starch, red sorghum, palm oil.

In a related aspect of the present invention there is disclosed a solid fuel composition for co-combustion with coal in a coal fired power plant, the composition including:

a waste oil such as engine oil, present in an amount of between about 10 to 20% by weight;

a cellulose material capable of absorbing the waste oil, wherein the cellulose material is present in an amount of about 75 to 85% by weight; and

an amount of about 5% by weight of a material or mixture of materials selected from grasses, plants, trees, algae, hemp, coconut, rice husks, and corn;

wherein when the composition is subject to combustion the composition exhibits a C0 ₂ emission of less than about 2%, an S0 ₂ emission of less than about 0.2% by weight, an ash content of less than about 1% by weight, and a net calorific value of greater than about 25 MJ/Kg.

In a further related aspect of the present invention there is disclosed a method of producing a fuel for co-combustion with coal in a coal fired power plant, the method including:

providing a predetermined amount of cellulose waste material;

providing a source of waste oil such as engine oil or the like;

the method including the steps of:

comminuting the cellulose material by filtering to obtain particle sizes in the range of less than about lmm;

decanting the waste oil at a temperature less than ambient temperature for reducing moisture content;

passing the cellulose material of reduced size through a vibrating hopper to substantially minimise particle bonding/coagulation; introducing the predetermined amount of cellulose material into a mixing chamber;

adding progressively the decanted oil to the mixing chamber to form a composition with the cellulose material, wherein the oil is added in an amount so that the composition contains about 10 to 20% by weight of oil;

allowing air drying of the composition at ambient temperature for about 24 to 48 hours;

wherein when the resultant fuel is subject to combustion, the fuel burns at about 1100 degrees C with substantially reduced C0 ₂ emissions and a resulting ash content of less than about 1%.

The method of producing a fuel for co-combustion of coal can further include addition of about 5% by weight of material selected from one or a combination of grasses, plants, trees, algae, hemp, coconut, rice husks, and corn. In one embodiment the material can include a mixture of mallee grass and timber pulp such as sawdust, to the cellulose material prior to addition of waste filtered oil.

In a related aspect of the present invention there is further disclosed a method of preparing a fuel composition for co-combustion with coal in a coal fired power station, the method including:

providing:

a mixing tank;

a source of waste oil selected from spent engine oil, spent aviation fuel, spent marine fuels, lubricants, vegetable oils, animal fats, municipal waste, camellina, algal oil, sewage sludge, babasu, cooking oils, fuel oils and the like; and

a source of reclaimed MDF (rMDF);

wherein the method includes:

pre-treating the rMDF with an effective amount of a water resistant material to form a coating;

comminuting the pretreated rMDF by filtering to obtain particle sizes in the range of less than about 1mm in diameter;

decanting the waste oil at a temperature less than ambient temperature for reducing moisture content; passing the rMDF of reduced size through a vibrating hopper to substantially minimise particle bonding/coagulation;

introducing a predetermined amount of the rMDF material into the mixing tank;

adding progressively the decanted oil to the rMDF in the mixing tank to form a composition with the rMDF material, wherein the oil is added in an amount so that the composition in the tank contains about 10 to 20% by weight of the waste oil;

allowing air drying of the composition in the tank at ambient temperature for about 24 to 48 hours;

wherein the waste oil is preferentially absorbed by the pre-treated rMDF to form a coagulated mixture having substantially low water content; and wherein the. mixture provides an alternative fuel source for co-combustion with • coal in a coal fired power plant with low carbon emission and low ash content while substantially maintaining combustion efficiency.

The method of the present invention represents an improvement over prior art waste oil reclamation systems and methods. It is found unexpectedly that the mixture formed from the method of the invention burns very efficiently leaving a low ash content. The mixture therefore provides an alternative fuel source which has the ability to produce energy efficiently, reduce reliance on fossil fuel reserves, replace coal and reduce carbon emissions.

The ability to effectively harness these waste materials as alternative fuel source reduces problems associated with waste oils and MDF going to landfill. In addition the use of reclaimed waste oil reduces the reliance on fossil fuel reserves.

The ability of water resistant treated rMDF to preferentially absorb oil in the presence of a source of waste oil, while substantially minimising water absorption, provides a cost effective means of reclaiming oils and an alternative efficient fuel source for coal replacement and co-combustion. In a related aspect of the present invention there is disclosed a method of producing an alternative fuel composition for co-combustion with coal in a coal fired power plant including:

providing a mixing tank;

a source of waste oil;

an amount of rMDF pre-treated with a water resistant coating in an amount of between about 10% to 20% by weight of the composition, and wherein the treated rMDF is capable of absorbing an amount of oil in waste oil in a ratio of oil to water of between about 5 to 15 times the amount of water absorption; and

providing a material or mixture of materials selected from grasses, plants (including extracts derived therefrom), trees, animal waste, algae, hemp, coconut, rice husks, and corn in an amount of up to about 5% by weight of the total composition; the method including:

comminuting the pretreated rMDF and select material(s) by filtering to obtain particle sizes in the range of less than about 1 mm in diameter;

decanting the waste oil at a temperature less than ambient temperature for reducing moisture content;

passing the rMDF and select material(s) of reduced size through a vibrating hopper to substantially minimise particle bonding/coagulation;

introducing an amount of the pretreated rMDF and select material(s) into the mixing tank so that the range of between about into the mixing tank;

adding progressively the decanted oil to the rMDF and select material(s) in the mixing tank

to form a composition with the rMDF material, wherein the oil is added in an amount so that the composition in the tank contains about 10 to 20% by weight of the waste oil;

allowing sufficient contact time in the mixing tank between the waste oil, water resistant rMDF and select material(s) to form a resultant coagulated material with substantially low water content;

allowing air drying of the composition in the tank at ambient temperature for about 24 to 48 hours;

recovering the coagulated material containing absorbed waste oil;

subjecting the coagulated waste material to sufficient compression effective for converting the waste material into a solid form; wherein the solid form is combustible such that a residue of less than about 17%w/w of the waste product remains post combustion.

An advantage of the present invention is that the alternative fuel source provides minimal residual waste at a power plant. The fuel source can be used as a substitute to coal and in comparison to coal there is provided a significant reduction in post- combustion residue.

In a further related aspect of the invention, there is disclosed a solid fuel for co- combustion with coal produced from the method of the invention. In one embodiment the alternative fuel can include:

a substantially solid fuel block containing water resistant rMDF and waste oil, wherein the amount of waste oil absorbed by the water resistant rMDF is between about 5 to 15 times the amount of water in the waste oil; and

wherein combustion of the block produces an emission of PCDD/F of substantially about 0.1 TEQ ng/Nm3.

The solid fuel block containing water resistant rMDF and waste oil burns efficiently and can substitute coal in conventional combustion systems. One advantage of the improved system is that waste oil and waste MDF can be reclaimed and combined to provide a fuel source that can replace or co-combust with conventional fossil fuels including coal.

The solid alternative fuel represents an advance over prior art systems. Without wishing to be bound by any theory, it is postulated that pre-treating the rMDF with a water resistant material gives the rMDF material oil super absorbency properties. In the presence of waste oil, the pre-treated rMDF is capable of preferentially absorbing oil in an amount of at least five times that of water. This significantly alters the absorption uptake of oil to water in the waste oil to produce a coagulant mixture with low water content.

In a further related aspect of the present invention there is disclosed an alternative fuel source including: a substantially solid fuel having a composition containing an effective amount of rMDF pre-treated with a water resistant material, and waste oil wherein the waste oil is absorbed by the treated rMDF in a ratio of waste oil to water of about 5:1 to 15: 1 ;

wherein the composition has a moisture content of less than about 18%w/w; and wherein the solid fuel is combustible whereby a residue of less than about 17%w/w of the waste product remains post combustion.

The solid fuel is adapted for substituting coal in combustion or co-combustion with improved fuel efficiency and concomitant conservation of fossil fuel reserves.

A further advantage of the product of the present invention is that emitted combustion gases are reduced compared to corresponding fossil fuels and reduce the environmental effects otherwise associated with fossil fuels. Hence the product of the invention represents a substitute for the fossil fuel industry.

Throughout the description "waste oils" can include waste materials from heavy and light industry, restaurants, fast food chains, households including Automotive Waste Oil (inc. mineral), Cooking Oils, Coconut Oil (& fibrous husks)

Reclaimed Cellulose waste can be obtained from building by-products, wood and wood based particle board, Straw, Coffee grounds, Olive pips, Fly ash (after burden) of current brown coal and the like.

In a further related aspect there is disclosed a method of reclaiming waste oil for use as a fuel source including:

providing:

a mixing tank,

a source of waste oil, and

a source of reclaimed cellulose;

wherein the method includes:

pre-treating the cellulose with an effective amount of a water resistant material to form a coating;

introducing an amount of the waste oil into the mixing tank; supplying an effective amount of the pre-treated cellulose to the waste oil;

wherein the waste oil is preferentially absorbed by the pre-treated cellulose to form a coagulated mixture having substantially low water content; and

wherein the mixture provides an alternative fuel source with low ash content for substituting coal and the like in combustion.

In a further related aspect there is disclosed an alternative fuel including:

a substantially solid fuel block containing substantially reclaimed cellulose and waste oil, wherein the reclaimed cellulose has been pre-treated with a water resistant material effective to absorb the waste oil in an amount between about 5 to 15 times the amount of water in the waste oil; and

wherein combustion of the block produces a calorific value equal to or greater than brown coal and an ash content of less than about 5% by weight.

The following embodiments are provided by way of examples, and not meant to be exhaustive.

Example 1

Composition:

20% by weight used engine oil; and

80% by weight rMDF.

In this example, a fuel composition for co-combustion with coal in a coal fired power station was prepared in accordance with the method of the present invention.

The method includes obtaining rMDF fibres and subjecting the fibres to a pre-treatment with a water resistant coating of a synthetic resin. A source of waste engine oil in an amount of 20% by weight of the composition was delivered and subjected to decanting at a temperature of about 0 degrees C to remove visible water. The pre-treated rMDF is comminuted by filtering to obtain an average particle size in the range of less than about 1mm in diameter. The comminuted rMDF is passed through a vibrating hopper and an amount of about 80% by weight of the total composition is introduced into a mixing tank.

The decanted waste engine oil is progressively added to the rMDF in the mixing tank to form a composition with the rMDF. The composition was allowed to air dry in the mixing tank at ambient temperature for about 24 to 48 hours to form a coagulant mixture.

A sample of the coagulant mixture was removed from the mixing tank and analysed. The coagulant composition was found to have a moisture content of 12%w/w.

The coagulant composition was subject to compression to form a solid block. The solid fuel block was subject to combustion and a residue of less than about 17%w/w of the waste product remained post combustion.

After the settling process, the coagulant composition is analysed, if required additives are injected, then the coagulant mass is combined through a screw mixing process, compressed and extruded into a solid fuel product. The solid product is then ready for shipment to the power plants to be loaded onto conveyor systems and into a boiler feed silo's ready to burn.

The waste can be combined before transport (coagulated) making it very stable and safe as the mixture has ah extremely low flash point and therefore is easier to transport by rail, road, ship and the like.

A particular benefit of the rMDF (wood fibre) is its absorbency. It was observed that rMDF acts as super coagulant with the waste engine oil and absorbs minimal parts of water from the waste supply.

The waste products required to formulate the fuel include oil (crude, automotive, cooking) and wood fibre, these are available in abundant quantities around the globe, which otherwise go to landfill or are only partially recovered. The applicant has found that waste management takes wood fibre such as rMDF that is currently dumped as landfill and waste oils (including crude, automotive, cooking, aviation fuels, engine oils etc.) that is disposed of in environmentally unfriendly or cost effective ways, and converts waste into energy with low residual waste ash (after burden) that could be combined with fertiliser and returned to the ground.

Testing & Technical Data

The fuel composition obtained from example 1 has undergone a series of analytical tests following combustion to compare technical properties with brown coal (lignite) as a source of co-combustion in existing power plants. The technical results are produced in Table 1 (refer below).

Example 2

Composition:

15% by weight used engine oil;

80% by weight rMDF;

1% by weight Malee tree;

1% by weight Saw dust;

1 % by weight Eucalyptus tree/ leaves;

1% by weight Olive tree/leaves; and

1% by weight used paper.

In this example, a fuel composition for co-combustion with coal in a coal fired power station was prepared in accordance with the method of the present invention including obtaining rMDF fibres and select combined materials comprising Malee tree, Saw dust, Eucalyptus tree/ leaves, Olive tree/leaves, and used paper.

The rMDF fibres were pre-treated with a water resistant spray coating of a synthetic resin. A source of waste engine oil in an amount of about 15% by weight of the composition was delivered and subjected to decanting at a temperature of about 0 degrees C to remove visible water. ^■ The pre-treated rMDF and select combination of materials is comminuted by filtering to obtain an average particle size in the range of less than about 1mm in diameter. The comminuted rMDF and select materials was passed through a vibrating hopper and introduced into a mixing tank.

The decanted waste engine oil is progressively added to the rMDF and the select combined materials in the mixing tank to form a composition. The composition was allowed to air dry in the mixing tank at ambient temperature for about 24 to 48 hours to form a coagulant mixture.

After the settling process, the coagulant composition is compressed and extruded into a solid fuel product through a screw mixing process, and analysed.

Testing & Technical Data

The fuel composition obtained from example 2 has undergone a series of analytical tests following combustion to compare technical properties with the composition of example 1 and brown coal (lignite). The technical results are produced in Table 1 (refer below).

Comparison with Existing Fossil Fuels

Table 1 below compares brown coal norms with the fuel composition of the present invention as obtained in examples 1 and 2 initial laboratory combustion testing.

Table 1

Measurement Brown Coal Solid Fuel 1 Ex. 1 Solid Fuel Ex. 2

(Lignite) from Invention from Invention

Gross Calorific Value 25 27.395 30.9

(MJ/Kg)

Net Calorific Value 15 25.090 28.9

(MJ/Kg)

Sulphur (S0 ₂ ) (%wt) 0.4% - 0.77% 0.148% 0.001%

Ash Content (%wt) 15% 0.690% 0.9%

Carbon Emitted 4.5% - 7.5% 0.6% - 1.5% 0.5% As shown in Table 1 the reclaimed waste oil fuel source of the present invention exhibits a significant decrease in ash content upon combustion hence more efficient combustion by alternative fuel of the instant invention, and there is a significant reduction in C0 ₂ emissions and S0 ₂ emissions compared to brown coal. This shows a potential for reclamation of waste oil and conversion to efficient energy source with concomitant reduction in C0 ₂ emissions.

Preliminary crude testing of co-combustion efficiency between brown coal and the fuel composition of the present invention was conducted using a test sample of the fuel composition obtained from example 2. A base load of fuel composition from example 2 was ignited in the presence of a sample of ground brown coal under ambient temperature and pressure conditions. The test exhibited accelerated burning of brown coal compared to a sample of brown coal on its own. The fuel composition of the invention improves combustion efficiency of coal.

The outcome of testing of the instant fuel from waste oil and cellulose such as pre- treated rMDF has the ability to challenge the Greenhouse gas effect globally because: a. reclaims waste oil - converts waste into energy and minimal residue that is eco friendly,

b. Reforms coal fired generation - could avoid costly replacement of infrastructure, c. Ensures that plant operators meet the requirements of their operating licence, d. Substantial C02 reduction - cleaner air & green bank for reduction credits, e. Societal benefits - waste management, creation of employment, less pollution.