The present invention relates to a marine vessel waste treatment installation, which installation includes at least one waste receiving unit, at least one waste feeding unit, at least one incinerator unit provided with an outlet, and at least one flue gas pipeline, according to the pre-characterizing portion of claim 1 . The present invention also relates to a method for flue gas cooling in a marine vessel waste treatment installation according to the pre-characterizing portion of claim 9. Background art

Various waste treatment installations are known from prior art. Typical waste treatment installations, also for treating wet waste such as food waste and so- called household waste, include a waste feeding hopper, from which waste is fed onto a transport screw which forwards the waste into an incinerator fur- nace. Burning of the waste takes place in the incinerator furnace e.g. at a temperature of 850 °C to 1200 °C. An example of such an installation is known from EP 1 384 948 B1 .

In such known waste treatment installations flue gas resulting from the burning of the waste has a very high temperature which generates dioxin-like chemi- cals.

In order to reduce the amount of generated dioxin-like chemicals a number of different solutions have been presented. CN 102230627 discusses a land based refuse combustion furnace with a separate gas quenching cooling tower. The cooling tower is provided with cooling water atomizers in order to lower the temperature of the flue gas. CN 103644570 discloses another known land based solution where high pressure water mist is used for quenching flue gas in connection with the combustion furnace. These are technically complex and space requiring constructions. EP 1 065 444 B1 discloses other exhaust gas cooling arrangements where high pressure water and high pressure air is in- troduced into a separate cooling chamber through a separate mixing device or high pressure hot water is introduced to an exhaust gas duct. These are technically complex constructions making them very expensive and apt to function- al failure. Furthermore, the known solutions are space demanding making them unsuitable for marine vessels.

Summary of invention

An object of the present invention is to avoid the drawbacks of prior art and to achieve an efficient marine vessel waste treatment installation with a simple flue gas cooling arrangement fulfilling the requirements of the relevant IMO Resolutions. This object is attained by a marine vessel waste treatment installation according to claim 1 and a method for flue gas cooling in a marine vessel waste treatment installation according to claim 9. The basic idea of the present invention is to effectively cool the flue gas within a short distance after the flue gas enters the flue gas pipeline from the outlet of the incinerator unit. This is achieved by an inline cooling arrangement that is installed in the flue gas pipeline. The cooling arrangement includes a water injection device with a water discharge nozzle for feeding a water stream directly into the flue gas pipeline at a given location of the flue gas pipeline. The cooling arrangement further includes a pressurized air injection device for feeding pressurized air into the water stream.

The advantage of the present invention is that no auxiliary cooling reactor is required. In addition, it is only necessary to provide the flue gas pipeline with a technically simple cooling arrangement and a temperature measuring arrangement. This is a technically advantageous and inexpensive measure, which requires no extra space onboard the marine vessel.

The pressurized air fed into the water stream disperses the water into mist that has a maximal surface to cool the flue gas within a given distance of about 2.5 m in the flue gas pipeline measured from the outlet of the incinerator unit. The flue gas is cooled to a temperature under or about 250 °C.

This particular requirement is based on the IMO Resolution MEPC 244(66), the Standard Specification for Shipboard Incinerators.

There are various advantageous arrangements for feeding the pressurized air into the water stream, which is fed directly into the flue gas pipeline. In a first arrangement, pressurized air is fed into the water stream as it is discharged from the water discharge nozzle. In another advantageous arrangement pres- surized air is fed into the water stream before it is discharged from the water discharge nozzle. In an alternative advantageous arrangement, pressurized air is fed into the water stream after it is discharged from the water discharge nozzle. The flue gas pipeline is advantageously provided with a temperature measuring unit located in the flue gas pipeline at a given distance from the outlet of the incinerator unit. This enables the control of the temperature at said given distance.

The given distance is advantageously about 2.5 m, whereby the prevailing norms can be accommodated.

The water injection device of the inline cooling arrangement is advantageously provided with a flow control means for adjusting a flow volume of the water stream based on a temperature measured by the temperature measuring unit. This enables adjustment of the cooling based on flue gas parameters. The pressurized air feed connection of the inline cooling arrangement is provided with a pressure control means for adjusting a pressure of the pressurized air based on a temperature measured by the temperature measuring unit. This enables adjustment of the cooling based on flue gas parameters.

Advantageously, both the flow control means and the pressure control means can be used in combination for an optimized control of cooling the flue gas in view of the desired temperature of the flue gas at the given distance from the outlet of the incinerator unit.

Further advantages features of the marine waste treatment installation are given in claims 2-8 and further advantageous features of the method for flue gas cooling in a marine waste treatment installation are given in claims 9-16.

Brief description of drawings

In the following the invention will be described, by way of example only, with reference to the accompanying schematic drawings, in which

Figs. 1 and 2 show a first embodiment of the present invention, Figs. 3 and 4 show a second embodiment of the present invention, and Figs. 5 and 6 show a third embodiment of the present invention. Detailed description

In figures 1 to 6 a marine vessel V waste treatment installation is indicated by reference numeral 1 . The waste treatment installation 1 is installed on board a marine vessel V as indicated in Figures 1 , 3 and 5.

The waste treated onboard the marine vessel V waste treatment installation 1 is normally composed of a mixture of dry waste and wet waste. Typically dry waste according to IMO standards would be composed of about 40% of cardboard, 30 % of other packaging and paper, 20% of fibers and 10% of plastics. Typically wet waste would be composed of food waste and sludge with a maximum moisture content of about 80%. The purpose is to maintain average moisture content of the waste mixture at a level of about 50% or below in order to ensure that the waste mixture burns efficiently in an incinerator unit.

Figures 1 and 2 illustrate a first embodiment of the present invention, figures 3 and 4 illustrate a second embodiment of the present invention, and figures 5 and 6 illustrate a third embodiment of the present invention. Generally the three embodiments comprise similar arrangements, whereby the main difference is in a cooling arrangement provided for the waste treatment installation, which is described separately in more detail below. The main components of the waste treatment installation 1 include a waste receiving unit 2, a waste feeding unit 3, and an incinerator unit 4. Flue gas resulting from the burning of the waste in the incinerator unit 4 is discharged into a flue gas pipeline 8 from an outlet 7 of the incinerator unit 4. The flue gas pipeline 8 is directly connected to the outlet 7 of the incinerator unit 4. The incinerator unit 4 may include a secondary burning chamber 6 with a flue gas channel 5 arranged before the actual outlet 7 of the incinerator unit 4. The waste mixture is burned in the incinerator unit 4 where after the flue gases resulting from the burning of the waste or waste mixture are discharged through the outlet 7 into the flue gas pipeline 8. In case the incinerator unit 4 includes a secondary burning chamber 6, an additional burning phase can take place in the secondary burning chamber 6 to ensure high fly-ash separation and a more complete burning of the flue gases. Such an arrangement would provide for a long gas retention time resulting in very clean burning. The first section of the incinerator unit 4 and the secondary burning chamber 6 are advantageously connected by the flue gas channel 5. The flue gas pipeline 8 is advantageously provided with a blower 9 in order to enhance the efficiency of discharge of the flue gas. In order to effectively cool the flue gas in the flue gas pipeline 8, the marine vessel V waste treatment installation 1 includes an inline cooling arrangement 10 connected to the flue gas pipeline 8. The inline cooling arrangement 10 includes a water injection device 1 1 with a water discharge nozzle 12 for feeding a water stream directly into the flue gas pipeline 8 at a given location A of the flue gas pipeline 8. The water injection device 1 1 is directly connected to and installed in a casing 81 of the flue gas pipeline 8 so that the water discharge nozzle 12 is located inside the casing 81 , whereby the water can be fed directly into the flue gas discharged into and flowing in the flue gas pipeline 8.

The water injection device 1 1 receives line pressure water from a source of water 13 onboard the marine vessel V, the line pressure usually being approximately 4 bar, normally available on a marine vessel. Between the water injection device 1 1 and the source of water 13 there is a flow control means 14 for adjusting and controlling the volume of water flow.

Further, the cooling arrangement 10 is provided with a pressurized air injection device 16 for feeding pressurized air into the water stream as the water is discharged from the water discharge nozzle 12 (Figures 1 and 2), into the water as it flows through the water injection device (Figures 3 and 4), or into the water after it is discharged from the water discharge nozzle 12 (Figures 5 and 6).

Pressurized air is provided to the pressurized air injection device 16 from a source of pressurized air 17 onboard the marine vessel V. Between the source of pressurized air 17 and the pressurized air injection device 16 there is a pressure control unit 18. The pressurized air used in this cooling arrangement is the pressurized air normally available in machinery rooms on a marine vessel. The flue gas pipeline 8 is provided with a temperature measuring unit 20 at a given distance D from the outlet 7 of the incinerator unit 4. The given distance is under or about 2.5 m as discussed above. The volume of water flow is controlled and adjusted based on the temperature measured by the temperature measuring unit 20 as indicated by broken lines in Figures 1-6. The pressure of the pressurized air is controlled and adjusted based on the temperature measured by the temperature measuring unit 20 as indicated by broken lines in Figures 1-6. By optimizing the volume of water flow and the pressure of the pressurized air the desired degree of cooling can be achieved, i.e. a flue gas tem- perature of under or about 250 °C in the flue gas pipeline 8 at the given distance of about 2.5 m from the outlet 7 of the incinerator unit 4.

In the embodiment of Figures 1 and 2, the water injection device 1 1 is provided with a channel for the water stream coming from the source of water 13 and a surrounding double hollow jacket. The pressurized air injection device 16 is di- rectly connected to the interior of the hollow jacket of the water injection device 1 1 from the side of the water injection device 1 1 so that pressurized air is fed into and along the hollow jacket and into the water discharge nozzle 12, whereby pressurized air is introduced into the water discharge nozzle 12 so that the pressurized air encounters the water stream as it is discharged from the water discharge nozzle 12 into the flue gas flowing in the flue gas pipeline 8. The pressurized air could also be fed to the water discharge nozzle 12 e.g. through a separate tubing.

In the embodiment of Figures 3 and 4, the water injection device 1 1 is provided with a channel for the water stream coming from the source of water 13 and a surrounding jacket. The pressurized air injection device 16 leads directly into the water channel through the jacket from the side of the water injection device 1 1 , whereby the pressurized air is introduced into the water stream already as it flows along the water channel and before the water is discharged from the water discharge nozzle 12 into the flue gas flowing in the flue gas pipeline 8. In the embodiment of Figures 5 and 6, the water injection device 1 1 is provided with a channel for the water stream coming from the source of water 13 and a surrounding jacket. In this embodiment, the pressurized air injection device 16 is directly connected to and installed in the casing 81 of the flue gas pipeline 8, separately from the water injection device 1 1 , so that the pressurized air injec- tion device 16 is partly located inside the casing 8. The pressurized air injection device 16 is installed closely to the discharge nozzle 12 of the water injection device 1 1 . In this way, the pressurized air is fed directly into water after the water is discharged from the water discharge nozzle 12 into the flue gas flowing in the flue gas pipeline 8. In all three embodiments, the pressurized air fed into the water stream disperses the water into mist that has a maximal surface to cool the flue gas within the given distance of about 2.5 m in the flue gas pipeline measured from the outlet 7 of the incinerator unit 4. The flue gas is cooled to a temperature about or under 250 °C.

The drawings and the description related thereto are only intended for clarification of the basic idea of the invention. The invention may vary in detail within the scope of the ensuing claims.