Technical Field

The present invention relates to a fuel-utilising method.

Background

Many industrial processes in various industries such as in power generation, marine industry, and aluminium recovery, just to name a few, involve the burning of fuel. Currently, most of the processes use heavy fuel oil (HFO), which is derived from residues from petroleum catalytic cracking. Combustion of HFO contributes to air pollution and results in high emissions of carbon dioxide (CO2), oxides of nitrogen (NO _X ) and oxides of sulphur (SO _X ). Accordingly, processes would require an additional step to scrub any emissions following the combustion of HFO before the emissions are released into the atmosphere. Such additional steps lead to additional resources being utilised. Further, fumes from burning HFO is corrosive and thereby require constant replacement of protective equipment which come into contact with the fumes. Also, since HFO is derived from fossil fuels, it is not considered to be sustainable.

Biodiesel has been proposed as a replacement for fossil fuels. While biodiesel results in a more sustainable alternative compared to fossil fuels, it requires additional processing such as conversion into biodiesel which contributes to the carbon footprint.

Thus, there is a need for an improved fuel-utilising method.

Summary of the invention

The present invention seeks to address these problems, and/or to provide a fuelutilising method using an environmentally friendly fuel.

According to a first aspect, the present invention provides a fuel-utilising method comprising: heating a fuel to form heated fuel; igniting the heated fuel to form ignited fuel; and burning the ignited fuel, wherein the fuel comprises a biofuel comprising > 5 wt% free fatty acid and wherein the fuel does not comprise biodiesel. The biofuel may be any suitable biofuel. For example, the biofuel may be agricultural- derived biofuel.

According to a particular aspect, the fuel may further comprise heavy fuel oil, light fuel oil, biodiesel, or a combination thereof.

The heating may be by any suitable means. The heating may comprise heating the fuel to a suitable temperature.

The igniting may be by any suitable means and under suitable conditions. For example, the igniting may be carried out in a burner. The igniting may comprise igniting the fuel at a suitable temperature. According to a particular aspect, the temperature may be a temperature below the flash temperature of the fuel. In particular, the igniting may be at a temperature of 30-80°C.

According to another particular aspect, the igniting may comprise igniting the fuel at a fuel to air volume ratio of 0.1 -0.5 L/m ³ .

The combusting may be under any suitable conditions. According to a particular aspect, the combusting may result in reduced NO _X , SO _X and CO2 emissions.

The method may further comprise filtering the fuel prior to the heating.

Brief Description of the Drawings

In order that the invention may be fully understood and readily put into practical effect there shall now be described by way of non-limitative example only exemplary embodiments, the description being with reference to the accompanying illustrative drawings. In the drawings:

Figure 1 shows a system utilising a method of burning fuel according to one embodiment of the present invention.

Detailed Description

As explained above, there is a need for an improved fuel-utilising method.

In general terms, the present invention provides a fuel-utilising method which enables the utilisation of an environmentally friendly fuel and one which is derived from sustainable sources. The method of the present invention utilises a biofuel which need not be converted into biodiesel and which may be used directly as obtained. In particular, the biofuel may be a by-product of or produced as waste in agricultural processes and may be used directly as a fuel in a fuel-utilising method without any further processing prior to its use.

The method of the present invention enables the use of sustainable agricultural-derived fuels instead of fossil fuels at almost equal rates of fuel consumption, thereby maintaining the fuel costs in the long run and at the same time, meeting the regulatory requirements as per the Paris Agreement on environmental emissions. The method enables reduction of the use of fossil fuels, as well as reduction of harmful gas emissions to the environment.

According to a first aspect, the present invention provides a fuel-utilising method comprising: heating a fuel to form heated fuel; igniting the heated fuel to form ignited fuel; and burning the ignited fuel, wherein the fuel comprises a biofuel comprising > 5 wt% free fatty acid and wherein the fuel does not comprise biodiesel.

For the purposes of the present invention, free fatty acid is defined as fatty acid which is produced from triglycerides by hydrolytic reactions in a process, such as dehydration or esterification.

The biofuel may be any suitable biofuel. The biofuel may be any suitable biofuel which has a suitable combustion characteristics and peak heat release rate, for example, a peak heat release rate similar to fossil fuels. The biofuel may be any non-corrosive biofuel and/or any edible or non-edible biofuel. For example, the biofuel may be agricultural-derived biofuel, such as a sustainable liquid fuel. The biofuel may be derived from, but not limited to, palm oil, coconut acid oil, jatropha oil, algae-derived liquid fuel. In particular, the biofuel may be, but not limited to, crude palm oil, palm oil methyl ester, palm sludge oil, palm acid oil, palm fatty acid distillate, high free fatty acid oil, or a combination thereof. According to a particular aspect, the fuel may further comprise heavy fuel oil (HFO), light fuel oil (LFO), marine fuel oil, biodiesel, or a combination thereof. The fuel may also further comprise bio-ethanol, ethanol, methyl-ester mixtures, or a combination thereof.

In particular, the fuel may comprise > 10 wt % biofuel based on the total weight of the fuel. The remaining weight may comprise a further fuel, such as that described above. For example, the fuel may comprise 10-80 wt %, 15-75 wt %, 20-70 wt %, 25-65 wt %, 30-60 wt %, 35-50 wt %, 40-45 wt % biofuel based on the total weight of the fuel. Even more in particular, the fuel may comprise about 80 wt % biofuel based on the total weight of the fuel. The fuel comprising a mixture of biofuel and a further fuel have the advantage of a controlled pH of the fuel in view of the mixture and reduction in corrosion as compared to using the further fuel alone.

The method of the present invention enables sufficient heat to be generated for use in various processes at high temperatures while at the same time reducing the amount of harmful gaseous emissions. Harmful gaseous emissions may comprise NO _X and SO _X emissions. The method of the present invention involves heating the fuel in use to an appropriate flash point so that the fuel may ignite and subsequently burn. In particular, the flow of the fuel may be controlled so that the thermal efficiency of the fuel being burned is achieved.

The heating may be by any suitable means. For example, the heating may be carried out in a heater. The heater may be any suitable heater. In particular, the heating may comprise heating the fuel using thermal oil. Even more in particular, the heating may be carried out in a heater comprising a thermal oil heating system.

The heating may comprise heating the fuel to a suitable temperature. For example, the heating may comprise heating the fuel to a temperature suitable to reduce the viscosity of the fuel. In particular, the heating may comprise heating the fuel to a temperature lower than the ignition temperature of the fuel. According to a particular aspect, the heating may comprise heating the fuel to a temperature of 33-80°C. For example, the heating may comprise heating the fuel to a temperature of 35-75°C, 40-70°C, 45-65°C, 50-60°C, 55-57°C. In particular, the heating may comprise heating the fuel to a temperature of 45-60°C. The method may further comprise filtering the fuel prior to the heating. In this way, any contaminant comprised in the fuel is filtered out prior to the heating. Such contaminants may interfere with the heating and eventually the burning of the fuel. The filtering may be by any suitable means. For example, the filtering may be carried out in a suitable filtering unit.

The igniting may be by any suitable means and under suitable conditions. For example, the igniting may be carried out in an igniting unit, such as, but not limited to, a burner. The igniting may comprise igniting the fuel at a suitable temperature. According to a particular aspect, the temperature may be a temperature below the flash temperature of the fuel. In this way, a lower amount of energy is required for igniting the fuel and the method would also be safer since the risk of being exposed to over-heated oil is reduced. In particular, the igniting may be at a temperature of 30-80°C. For example, the igniting may be at a temperature of 33-80°C, 35-75°C, 38-70°C, 40-65°C, 42-63°C, 45-60°C, 48-58°C, 50-57°C, 51-56°C, 52-55°C, 53-54°C. Even more in particular, the temperature is 45-60°C.

According to another particular aspect, the igniting may comprise igniting the fuel at a suitable fuel to air volume ratio. The fuel to air volume ratio may be controlled by adjusting the valves and pumps responsible for pumping the fuel and air to the unit in which the igniting is performed. In particular, the fuel to air volume ratio may be 0.1-0.5 L/m ³ . For example, the fuel to air volume ratio may be 0.15-0.28 L/m ³ , 0.16-0.25 L/m ³ , 0.18-0.23 L/m ³ , 0.19-0.22 L/m ³ , 0.20-0.21 L/m ³ . Even more in particular, the fuel to air volume ratio may be 0.16-0.25 L/m ³ . The advantage of having a suitable fuel to air volume ratio is to enable the fuel to ignite below its flash point. For example, a high fuel to air ratio will result in incomplete burning and producing a lot of soot, while a low fuel to air ratio may result in too much air being supplied and therefore prevent the fuel from igniting.

The combusting may be under any suitable conditions. For example, the combusting may be carried out in the same or different unit as the igniting. In particular, the combusting may be in the same unit as the igniting. According to a particular aspect, the combusting may result in reduced NO _X , SO _X and CO2 emissions. In particular, the combusting may result in about 15-25% decrease in emissions. For example, the combusting may result in a 16% decrease in NO _X emissions. According to another particular aspect, the combusting may result in a 21% decrease in SO _X emissions. The combusting may result in a 16% decrease in CO2 emissions.

The method of the present invention may be carried out in any suitable system. Examples of suitable systems include, but not limited to, aluminium dross recycling systems, ship bunkering systems, non-iron metal smelting system, energy production system.

According to one embodiment, Figure 1 shows a system utilising the method as described above. The system as shown in Figure 1 is by way of example only and a skilled person would understand that the method may be carried out on other suitable systems as well. As shown in Figure 1 , the system 100 comprises a fuel storage tank 102 for storing a fuel. The temperature of the fuel stored within the fuel storage tank 102 may be maintained at a first pre-determined temperature by way of a thermo oil heating element 104. The first pre-determined temperature may be a temperature at which the fuel within the fuel storage tank 102 remains at liquid state and does not solidify.

In particular, the system 100 may comprise a temperature controller (not shown). The temperature controller may be an automated temperature controller. The temperature controller may be configured to execute instructions for monitoring and measuring the temperature of fuel stored within the fuel storage tank 102. In some embodiments, the temperature controller may be configured to perform instructions for heating the fuel within the fuel storage tank 102 so that the temperature of the fuel is maintained at the first pre-determined temperature. The temperature controller may be in communication with various components, such as the thermo oil heating element 104, a thermo oil storage tank 108, a pump 110 and a thermo oil heater 112, in the system 100 to control temperature of the fuel within the fuel storage tank 102. The temperature controller may comprise at least one thermometer 106 for measuring the temperature of the fuel comprised in the fuel storage tank 102.

The thermo oil heating element 104 may be fluidically connected to the thermo oil storage tank 108. In particular, the thermo oil storage tank 108 may be configured to hold thermo oil for supplying thermo oil to the thermo oil heating element 104 so that fuel stored in the oil storage tank 102 may be heated by indirect heating to the first predetermined temperature. Thermo oil comprised in the thermo oil storage tank 108 may be supplied to the thermo oil heating element 104 by way of the pump 110. In particular, the thermo oil comprised in the thermo oil storage tank 108 may be heated prior to being supplied to the thermo oil heating element 104. The heating may be by the thermo oil heater 112.

There is continuous flow of thermo oil between the thermo oil storage tank 108 and the thermo oil heating element 104 to ensure that there is no pressure build-up in the system supplying the thermo oil.

It would be appreciated by a person skilled in the art that the heating of fuel comprised in the fuel storage tank 102 is by way of indirect heating and therefore the system 100 provides a safe way of heating the fuel since using any form of direct heating of the fuel may pose a fire hazard. As heated thermo oil used for heating the fuel within the fuel storage tank 102 is not in direct contact with the fuel, there is minimal or no risk of a fire or explosion.

The fuel storage tank 102 may be fluidically coupled to a burner unit 114. The burner unit 114 may be any suitable unit configured to ignite and burn fuel from the fuel storage tank 102. The burner unit 114 may comprise a nozzle having a suitable nozzle size, thereby controlling the ratio of fuel to air volume ratio entering the burning unit 114 when in use.

In particular, the fuel storage tank 102 may be coupled to the burner unit 114 via a filter unit 116 and/or a secondary heater unit 118. The filter unit 116 may be any suitable filter unit capable of filtering the fuel from the fuel storage tank 102 prior to being heated in the secondary heater 118 and/or prior to being ignited and burnt in the burner unit 114.

The secondary heater 118 may comprise a suitable heater for adjusting the temperature of the fuel to a second pre-determined temperature just before it enters the burning unit 114. For example, the second pre-determined temperature may be a temperature below the flash temperature of the fuel. The secondary heater 118 may comprise a heating element to heat the fuel passing through the secondary heater 118 to a second pre-determined temperature. However, the heating element comprised in the secondary heater 118 may not be in direct contact with fuel passing through the secondary heater 118, thereby providing indirect heating to the fuel. In particular, use of the secondary heater 118 is so that fuel entering the burner unit 114 is not directly heated by an open flame, but rather is heated via the heating element comprised in the secondary heater 118, thereby improving the safety of the system 100. Fuel from the burner unit 114 may also be re-directed back to the secondary heater 118 for reheating, if necessary.

Fuel entering the burner unit 114 may be maintained at a pre-determined temperature by way of a thermo oil heating element (not shown). The thermo oil heating element may be similar to the thermo oil heating element 104. A skilled person would understand that other forms of the thermo oil heating element may also be used. Accordingly, thermo oil from the thermo oil storage tank 108 may also be directed to the burner unit 114. In particular, the thermo oil comprised in the thermo oil storage tank 108 may be heated prior to being supplied to the thermo oil heating element of the burner unit 114. The heating may be by the thermo oil heater 112. Thermo oil may be re-routed back to the thermo oil storage tank 108 from the thermo oil heating element of the buner unit 114 to maintain continuous flow of thermo oil within the system 100. In this way, pressure build-up in conduits supplying the thermo oil may be prevented within the system 100.

Having now generally described the invention, the same will be more readily understood through reference to the following embodiment which is provided by way of illustration, and is not intended to be limiting.

Example

Example 1 - Comparison of results using HFO and biofuel

The method of the present invention was carried out using crude palm oil (CPO) and heavy fuel oil (HFO) as the biofuel. In particular, the biofuel comprised a mixture of 7.67 wt % HFO and 92.33 wt % CPO. The method was also carried out using HFO as the fuel as a comparative example.

Each of the fuels was burnt in a burner unit having an oil nozzle size of 5 mm. A fuel to air volume ratio of 0.16 L/m ³ was maintained within the burner to ensure the fuel burnt properly and completed combustion to minimize soot. The fuel mixture was heated to a temperature of 60°C and maintained there for 12 hours prior to being ignited and burnt. Samples of the emitted smoke were obtained and analysed. The results are provided in

Table 1.

Table 1 : Results of analysis carried out of emissions using biofuel and HFO as fuel

As can be seen from Table 1, use of the biofuel in the method of the present invention resulted in lower emissions of NO _X , SO _X and total particulate matter as compared to using HFO alone.

Whilst the foregoing description has described exemplary embodiments, it will be understood by those skilled in the technology concerned that many variations may be made without departing from the present invention.