WO2011113437A1

WO2011113437A1 - Preheater unit for heating oil

Info

Publication number: WO2011113437A1
Application number: PCT/DK2011/050085
Authority: WO
Inventors: Martin SØRENSEN
Original assignee: Mst Montage-Service Teknik V/Martin Baltø
Priority date: 2010-03-15
Filing date: 2011-03-15
Publication date: 2011-09-22
Also published as: DK201070100A; DK177174B1

Abstract

A preheater unit for heating oil, preferably vegetable oil, where the preheater unit includes an oil tank, where the oil tank includes a supply connection from an oil reservoir, and where the preheater unit further includes a flow-type heater, which is peculiar in that the oil tank and the flow-type heater are in thermal connection, where an inlet connection connects the flow-type heater and the oil tank, where the flow-type heater has an outlet connection, and where the flow-type heater includes a heating element.

Description

PREHEATER UNIT FOR HEATING OIL

Field of the Invention

The present invention concerns a preheater unit for heating oil, preferably vegetable oil, where the preheater unit includes an oil tank, where the oil tank includes a supply connection from an oil reservoir, and where the preheater unit further includes a flow- type heater.

The present invention also concerns a method for heating oil, preferably vegetable oil, in a preheater unit, where oil is conducted from a reservoir to an oil tank.

The present invention further concerns use of the preheater unit.

Background of the Invention

Bio-fuel in the form of vegetable oil, e.g. rape oil, has been developed into a substitute for fossil fuels as e.g. fuel oil. However, vegetable oils cannot be used directly in existing oil-fired burners.

The most important reason that vegetable oils cannot be used directly in existing oil- fired burners is that vegetable oil is a heavy type of oil. "Heavy" is to be understood that it does not flow very easily at normal atmospheric conditions, corresponding to high viscosity. In order for vegetable oil to flow sufficiently for use in an oil-fired burner, the oil is to have a temperature of about 60-80°C, whereby it is provided a lower viscosity. In GB 751 635 is described an oil-fired burner with a preheater tank for burning heavy types of oil. The preheater tank is supplied oil from an oil tank via a pipeline. The oil level is controlled by a level regulator measuring the oil level with a float. An electric heating element is disposed in the tank for heating the oil. Heating is controlled by a thermostat disposed in the tank. One of the drawbacks of the preheater tank as described in GB 751 635 is that the oil is in direct contact with the electric heating elements. Some types of vegetable oil easily form soot in the shape of flakes at high temperatures. In that the oil is in direct contact with the heating elements there may be great temperature differences between the oil in contact with the heating element and the oil at the thermostat, and soot is therefore easily formed. These soot flakes may in the worst case be carried with the flow of oil from the preheater tank to the firing unit, where they may block the oil flow and interrupt the production of the firing unit, or even cause damage to it. In GB 1 128 557 is described a flow-type heater for an oil burner. The preheater consists of two coils of piping superposed on each other and in which the oil flows. An electric heating element is inserted between these coils. A thermostat with a sensor disposed around the piping controls the heating element. The preheater in GB 1 128557 does not expose the oil to direct contact with the heating element, however, the oil in the piping closest to the heating element will be subjected to more heating than in the piping farther from the heating element. This may imply uneven heating of the oil, and it may therefore be difficult to control the temperature precisely. Furthermore, the preheater will generate a lot of waste heat which cannot be utilised.

Object of the Invention

It is the object of the invention to indicate a preheater unit for an oil-fired burner which ensures precise control of the oil temperature at the same time as the risk of formation of soot is eliminated, where furthermore optimisation of the utilising of the supplied heat is effected such that no waste heat is generated.

Description of the Invention

According to the invention, this is achieved by a preheater unit of the type mentioned in the introduction which is peculiar in that the oil tank and the flow-type heater are in thermal connection, where an inlet connection connects the flow-type heater and the oil tank, where the flow-type heater has an outlet connection, and where the flow-type heater includes a heating element.

The method according to the invention is peculiar in that the oil in the oil tank becomes preheated by waste heat from a flow-type heater, where the oil is conducted from the oil tank to the flow-type heater, where the oil in the flow-type heater is heated further to an outlet temperature, and where the oil is conducted directly or indirectly from the flow-type heater to a place of consumption, preferably in an oil-fired burner. Oil to be burned is typically stored in an oil reservoir close to where the combustion takes place. In order to heat the oil to a desired temperature, the outlet temperature, the oil is conducted from the reservoir via a supply connection to an oil tank. The oil level in the oil tank will typically be kept constant, e.g. by using a float in connection with the supply connection.

The oil tank will preferably contain a relatively small amount of oil, typically in the range of a quarter to one litre. The oil tank may advantageously be thermally insulated in relation to the surroundings.

The preheater unit further includes a flow-type heater which is in thermal connection with the oil tank. By thermal connection is meant that excess heater is conducted from the flow-type heater to the oil tank. Since heat tends to move upwards, in a simple embodiment the thermal connection is made by arranging the flow-type heater in physical contact with and immediately under the oil tank. The thermal connection may, among others, also include a liquid connection conducting excess heat from the flow-type heater to the oil tank. This thermal connection ensures that excess heat from the flow-type heater ends in the oil tank and thereby preheats the oil in the oil tank.

The flow-type heater is connected to the oil tank with an inlet connection. The oil may thereby flow from the oil tank and through the flow-type heater to the outlet connection. The outlet connection will typically lead to an oil burner. The outlet connection may, however, also lead to a combustion engine or other kind of combustion facility. The flow-type heater includes a heating element such that the oil flowing through the flow-type heater is heated thereby to the desired temperature. The heating element may advantageously be disposed in a block of heat-conducting material and may be provided with up to a plurality of integrated channels for a flow of oil in connection with heating of the latter. The waste heat acting on the mentioned oil tank and emerging from this block can come from heat radiation and heat conduction as the block may be in direct or indirect thermal contact with the oil tank.

According to a further embodiment, the invention is peculiar in that the flow-type heater includes at least one regulating thermostat.

The flow-type heater further includes a regulating thermostat. The regulating thermostat is connected with the heating element and thereby controls the outlet temperature of the oil after having flowed through the flow-type heater. The regulating thermostat will typically include one or more temperature sensors in the flow-type heater for measuring the oil temperature. By including a regulating thermostat is achieved that the heating element can be turned off and on, and possibly power regulated, thereby achieving that the heat deposited in the oil while passing through the flow-type heater can be regulated.

According to a further embodiment, the method is peculiar in that the outlet temperature of the oil is controlled and regulated by a thermostat, where the thermostat is connected to a heating element. By heating vegetable oils it is important that the temperature can be controlled precisely as the efficiency of the current combustion methods is strongly dependent thereon. In that the outlet temperature is controlled by the regulating thermostat is achieved that an optimal combustion of the oil can be achieved when the oil is conducted on from the preheater unit.

According to a further embodiment, the method is peculiar in that the outlet temperature of the oil is between 40 and 100°C, preferably between 60 and 80°C. By burning e.g. fuel oil and diesel oil the oil is atomised before ignition in a combustion chamber. In order to burn vegetable oil in the same way, it is required that the oil can be atomised, though different types of vegetable oil have a viscosity which depends on the temperature. Therefore, it is important that the oil has a temperature and thereby a viscosity ensuring an optimal atomisation and thereby optimal combustion. For most types of vegetable oil, this will mean a temperature of the oil is between 40 and 100°C, preferably between 60 and 80°C. By precise temperature control an optimal combustion and thereby high utility value of the fuel is achieved. According to a further embodiment, the invention is peculiar in that the flow-type heater includes an over-temperature safeguard.

As a safety measure, the flow-type heater includes an over-temperatures. The over- temperature safeguard ensures that the heating element is switched off in case that the oil becomes too hot due to a deficient thermostat or other events. The over- temperature safeguard is typically disposed in connection with the heating element and in the vicinity thereof. The over-temperature safeguard ensures that due to an error in the system, no overheating of the oil occurs, which either may boil over (i.e. run out of the oil tank) or cause dangerous situations in other ways. If the over-temperature safeguard detects too hot temperature around the heating element, it is switched off. A light indicator or the like may possibly be connected to the over-temperature safeguard to inform that it is switched on.

According to a further embodiment, the invention is peculiar in that the flow-type heater is made of a heat conducting material, e.g. aluminium.

In that the flow-type heater is made of a heat conducting material, it is achieved that the heat from the heating element is rapidly distributed on the entire flow-type heater. Thereby is achieved uniform heating of the oil in the flow-type heater.

In a very suitable embodiment, the flow-type heater is made of one piece of aluminium with a duct in which the heating element and the regulating thermostat are inserted. The oil then flows through the duct and becomes heated thereby. The oil will become uniformly heated since the heat from the heating element will be dispersed to the whole piece of aluminium, and in addition it is ensured that no deposition of oil in the form of soot or similar substances occurs, where these deposits are formed by overheating by direct contact with the heating element. Such deposits may eventually be loosened and cause problems in the form of e.g. clogged connecting lines and nozzles. The temperature sensor of the regulating thermostat may advantageously be disposed in the channel close to the outlet connection in order to ensure precise and correct temperature of the oil. According to a further embodiment, the invention is peculiar in that the heating element an electric heating element.

Electric heating elements are cheap and robust while at the same time being reasonably efficient. An electric heating element is an ideal choice for the flow-type heater. The power of the electric heating element will typically be determined by the size of the preheater unit, i.e. how much oil the preheater unit is to deliver per time unit, and which type of oil to be used and thereby which outlet temperature to be demanded.

Description of the Drawing

The invention is described in the following with reference to the drawing, wherein:

Fig. 1 shows the preheater unit as seen from one side;

Fig. 2 shows the preheater unit as seen from another side; and

Fig. 3 shows the flow-type heater.

In the explanation of the Figures, identical or corresponding elements will be provided with the same designations in different Figures. Therefore, no explanation of all details will be given in connection with each single Figure/embodiment. Figure references

1. preheater unit

2. oil tank 3. supply connection

4. float

5. flow-type heater

6. inlet connection

7. heating duct

8. outlet connection

9. heating element

10. regulating thermostat

11. boring for a heating element

12. boring for a regulating thermostat

Detailed Description of Embodiments of the Invention

Fig. 1 shows the preheater unit 1 as seen in cross-section from one side. The preheater unit 1 includes an oil tank 2 where the oil tank 2 is connected to an oil reservoir (not shown) via a supply connection 3. The oil level in the oil tank 2 is controlled by a float 4 acting by interrupting the supply connection when the oil level and thereby the float 4 reach a certain height. When the oil level and thereby the float 4 are below this height, the supply connection 3 will be open, and oil will flow from the oil reservoir (not shown) to the oil tank 2. The oil tank 2 is connected to a flow-type heater 5 via an inlet connection 6. The inlet connection 6 is connected to the oil tank 2 at a level some distance apart from the flow-type heater 5. The oil supplied to the oil tank 2 has a different temperature than the one existing in the oil tank 2 while at the same time waste heat is supplied from the flow-type heater 5 to the oil tank 2, meaning that a natural circulation is imparted the oil in the oil tank 2. Disposition of the inlet connection 6 utilises the circulation so that oil conducted away from the oil tank 2 becomes mixed and thereby has a uniform temperature. The oil is conducted through the flow-type heater 5 in a heating duct 7 to an outlet connection 8. The outlet connection 8 is typically connected directly or indirectly to a combustion unit, as e.g. an oil-fired burner (not shown). In this embodiment, the flow-type heater 5 is disposed directly under the oil tank 2 such that waste heat from the flow-type heater 5 is easily conducted to the oil tank 2. Fig. 2 shows the preheater unit 1 as seen in cross-section from another side. Here, it appears that the flow-type heater 5 includes a heating element 9 which is arranged in a boring in the block constituting the flow-type heater 5, and a regulating thermostat 10 which is also arranged in a boring in the block constituting the flow-type heater 5.

Fig. 3 shows the preheater unit 5 as seen in cross-section from above. The flow-type heater 5 includes a heating duct 7, a boring 11 for a heating element 9 and a boring 12 for a regulating thermostat 10.

Claims

1. A preheater unit (1) for heating oil, preferably vegetable oil, where the preheater unit (1) includes an oil tank (2), where the oil tank (2) includes a supply connection (3) from an oil reservoir, and where the preheater unit (1) further includes a flow-type heater (5), characterised in that the oil tank (2) and the flow-type heater (5) are in thermal connection, where an inlet connection (6) connects the flow-type heater (5) and the oil tank (2), where the flow-type heater (5) has an outlet connection (8), and where the flow-type heater (5) includes a heating element (9).

2. Preheater unit (1) according to claim 1 , characterised in that the flow-type heater (5) includes at least one regulating thermostat (10).

3. Preheater unit (1) according to claim 2, characterised in that the flow-type heater (5) includes an over-temperature safeguard.

4. Preheater unit (1) according to any preceding claim, characterised in that the flow- type heater (5) is made of a heat-conducting material, for example aluminium.

5. Preheater unit (1) according to any preceding claim, characterised in that the heating element (9) is an electric heating element (9).

6. A method for heating oil, preferably vegetable oil, in a preheater unit (1), where oil is conducted from a reservoir to an oil tank (2), characterised in that the oil in the oil tank (2) becomes preheated by waste heat from a flow-type heater (5), where the oil is conducted from the oil tank (2) to the flow-type heater (5), where the oil in the flow- type heater (5) is heated further to an outlet temperature, and where the oil is conducted directly or indirectly from the flow-type heater (5) to a place of consumption, preferably in an oil-fired burner.

7. Method according to claim 6, characterised in that the outlet temperature of the oil is controlled and regulated by a thermostat (10), where the thermostat (10) is connected to a heating element (9).

8. Method according to claim 6 or 7, characterised in that the outlet temperature of the oil is between 40 and 100°C, preferably between 60 and 80°C.

9. Use of a preheater unit (1) according to any of claims 1 - 5 for heating oil for an oil- fired burner.

10. Use of a preheater unit (1) according to any of claims 1 - 5 for heating oil for a combustion engine.