System and method for treating hazardous waste

Abstract

A system and method for treating hazardous waste, the system comprising: a pyrolysis reactor for receiving hazardous waste and generating a pyrolysis gas; at least one afterburner arrangement comprising: an inlet for receiving pyrolysis gas from the pyrolysis reactor, an inlet for receiving and mixing the pyrolysis gas with a source of oxygen to form a combustible gas mixture, an igniter for igniting the pyrolysis gas received by the inlet, a combustor for combusting the pyrolysis gas at an oxidation temperature to form flue gas, and an outlet connected to the combustor for providing the flue gas, a flue gas treatment arrangement in fluid communication with the outlet for receiving flue gas, the flue gas treatment arrangement comprising a cooler for cooling the flue gas, and a flue gas cleaning arrangement, for filtering the flue gas and providing filtered flue gas, and wherein the combustor comprises a flow conduit for leading and retaining the flue gases, and wherein the combustor comprises a heater for heating the flow conduit.

Description

[0001] SYSTEM AND METHOD FOR TREATING HAZARDOUS WASTE

[0002] TECHNICAL FIELD

[0003] The present invention relates to a system for treating hazardous waste, such as medical waste.

[0004] BACKGROUND

[0005] Waste treatment and disposal of waste is of importance since improper handling of waste may lead to negative environmental impact. Hence, waste treatment aims to reduce the dangerous effects of waste on the environment and human health.

[0006] Waste may be hazardous waste. Hazardous waste such as medical or biological waste, may contain pathogens harmful to the environment or humans. Hazardous waste such as medical or biological waste may also comprise pharmaceutical waste, infectious waste, pathological waste, chemotherapy waste and the receptacles and supplies generated during its handling and / or storage. Such waste is commonly produced in hospitals and medical care institutions or laboratories. Improper handling, and disposal of such waste to landfills may result in the spread of disease in the environment to both animals and humans. Hence, reducing handling and transport of such waste would be desirable.

[0007] In addition to a need to reduce handling and transport of waste, there is also a need to provide alternative waste treatment in cases where transport of waste to a waste management facility may be impractical, uneconomical, or impossible. Such an alternative may be desirable for offshore platforms, such as oil rigs, or ships having limited space for waste storage.

[0008] Waste may also be in the form of illegal and controlled drugs, or narcotics, wherein controlled destruction is required to prevent the waste from reaching the wrong hands.

[0009] Accordingly, there is a need to provide a safe and improved system and method for treating waste that reduces the risk of waste negatively impacting the environment and harming humans, and that reduces handling and transport of the waste.

[0010] SUMMARY

[0011] At least one of the abovementioned needs or at least one of the further needs which will become evident from the below description, are according to a first aspect of the present invention obtained by: A system for treating waste, preferably hazardous medical waste, the system comprising: a gasification reactor for receiving waste and generating a gas; at least one afterburner arrangement comprising: an inlet for receiving the gas from the gasification reactor, an inlet for receiving and mixing the gas with a source of oxygen to form a combustible gas mixture, an igniter for igniting the combustible gas mixture received by the inlet, a combustor for combusting the combustible gas mixture to form flue gas, and an outlet connected to the combustor for providing the flue gas, a flue gas treatment arrangement in fluid communication with the outlet for receiving flue gas, the flue gas treatment arrangement comprising a cooler for cooling the flue gas, and a flue gas cleaning arrangement, for filtering the flue gas and providing filtered flue gas, and wherein the combustor comprises a flow conduit for leading and retaining the flue gas, and wherein the combustor comprises a heater for heating the flow conduit.

[0012] Waste may be hazardous waste. Hazardous waste such as medical or biological waste may comprise infectious waste, pathological waste, chemotherapy waste and the receptacles and supplies generated during its handling and / or storage. Such waste is commonly produced in hospitals and medical care institutions. The waste may thus be hazardous medical waste.

[0013] The waste may be mixed waste comprising waste of the above-mentioned types. The waste may be in a dry state, a wet state and or a combination thereof. The system for treating waste can be installed in a medical facility or other facility in-situ and thereby reduce the need to transport waste by providing a local waste treatment system. By in situ is meant that waste treatment is done at a location, at or close to, where the waste is produced. The waste treatment may thus be made locally or on site. The waste treatment system may be installed in a hospital, a medical care institution, or in a laboratory to treat waste produced at these facilities. For instance, the system may be installed on an oil platform for treating the waste produced on the oil platform. In another example, the system may be installed on a ship for treating the waste produced on the ship. In a further example, the system may be installed in a customs or border agency facility, for treating or the destruction of illegal drugs seized at the customs or border facility. The system may be adapted for treating waste in batches. Each batch may comprise 10 L to 100 L of waste, preferably 10 L to 60 L of waste, such as 30 L of waste. Alternatively, each batch may comprise 10kg to 100 kg of waste, preferably 10 kg to 60 kg of waste, such as 30kg of waste. The system is thus adapted for treating waste in smaller batches and the overall footprint of the installation of the system is small. This allows for the system to be installed in situ, or locally to the source where the waste is produced.

[0014] The gasification reactor converts organic or fossil-based carbonaceous materials at high temperatures (<700°C), without combustion, with a controlled amount of oxygen and / or steam into carbon monoxide, hydrogen, and carbon dioxide. The gaseous product, or syngas, has a high energy content and may subsequently be mixed with a source of oxygen gas, ignited and combusted.

[0015] Preferably the gasification reactor converts organic or fossil-based carbonaceous materials, or waste, at a temperature in the range of 130 to 550 °C .

[0016] The gasification reactor or pyrolysis reactor comprises a heater for heating the waste. The gasification reactor may be a pyrolysis reactor for, receiving waste and generating a pyrolysis gas. The pyrolysis reactor may perform a pyrolysis reaction with an oxygen- deprived environment present inside the pyrolysis reactor. The oxygen-deprived comprises no or low levels of oxygen, preventing combustion of the pyrolysis gas during pyrolysis gas generation in the pyrolysis reactor. The oxygen-deprived environment may be achieved by pyrolysis using a heater for heating the hazardous waste and providing a purging gas, such as nitrogen. The purging gas may also be used to displace the pyrolysis gas to flow from the pyrolysis reactor to the afterburner arrangement. The pyrolysis reactor may comprise an opening or inlet for receiving the hazardous waste, such as a door or hatch.

[0017] The inlet may also be arranged for receiving hazardous waste that has been mechanically processed or prepared to remove or separate any metals and inert material from the hazardous waste material. Alternatively, removal of metals and inert material may be done after pyrolysis, by processing of the ash.

[0018] The opening or inlet of the pyrolysis reactor may be manually loaded by an operator. The processed material may also be fed through an automated arrangement such as using a screw feeder. This removes the need for manual filling of the pyrolysis reactor and thus reduces the risk of humans coming into contact with any harmful pathogens in the hazardous waste.

[0019] The pyrolysis reactor may comprise a steam outlet, or second outlet. The second outlet may be fluidly connected to a controllable steam valve. The steam valve may be set in a closed position or an open position. The steam outlet and steam valve are connected and arranged to allow steam, or water vapor, to be removed, or discharged, from the pyrolysis reactor, or pyrolysis chamber.

[0020] As the heater of the pyrolysis reactor heats the waste to above a vaporization temperature, water in the waste will vaporize and form steam, or water vapor. The water vapor may exit the pyrolysis reactor via the steam outlet. In a drying step, the pyrolysis reactor may heat the waste to a predetermined temperature or to a temperature within a range suitable for vaporizing the water vapor in the waste, and maintain the temperature at the predetermined temperature or within the temperature range for a predetermined time. Alternatively, the moisture content inside the pyrolysis reactor may be measured by a sensor, and the drying step may maintain the temperature at the predetermined temperature or within the temperature range until the moisture content has decreased to a desired, or predetermined, level, that indicates that the waste is dry.

[0021] The heater may be connected to a control unit. The control unit may be connected to sensor for measuring and determining the moisture content inside the pyrolysis reactor. The pyrolysis chamber may comprise further sensors such as pressure sensors for determining the pressure inside the pyrolysis chamber, and / or weight sensors to determine the weight of the waste loaded into the pyrolysis reactor. The further sensor may be connected to, and provide data, to the control unit. The control unit may control the heater and adjust the temperature of the pyrolysis reactor based on the data provided by the sensors to the control unit. This may provide an energy efficient heating of the pyrolysis reactor.

[0022] Arranged downstream the pyrolysis reactor a particle separator, may be arranged. The particle separator may be arranged to receive pyrolysis gas from the pyrolysis reactor and separate particles, such as soot, from the pyrolysis gas. This reduces the risk that soot or particles generated during the pyrolysis reaction clog and negatively influence system components arranged downstream the particle separator. The particle separator may be a mechanical particle separator. For example, the particle separator may be a filter, that mechanically filters particles from the pyrolysis gas by pores or openings arranged in the filter. In an alternative, the particle separator may be a filterless particle separator. For example, the particle may be separated from the pyrolysis gas by an induced electrostatic charge applied on the particles. The particle separator may be an electrostatic separator.

[0023] The particle separator may be a gravity or inertia separator. It is understood that a gravity separator works on the principle that gravity acting on the particles flowing in the pyrolysis stream separates the particles from the pyrolysis gas stream. The separated particles may be collected and removed from the system.

[0024] It is understood that an inertial separator concentrate, or collect, or separate particles from the pyrolysis gas by changing the direction of motion of the pyrolysis gas, in a way that the particle trajectories cross over the pyrolysis gas steamlines. The particles are either concentrated into a small part of the pyrolysis gas flow or are separated by impingement onto a surface. The inertial separator may be a cyclone separator or vortex separator.

[0025] In a further example, the particle separator may be a baffle separator or a settling separator. The particle separator may be arranged upstream the at least one afterburner arrangement as is discussed below. The particle separator may thus reduce the risk of clogging or negative impact soot may have on the afterburner arrangement, or further system components arranged downstream the afterburner arrangement.

[0026] Alternatively, the particle separator may be an electrostatic particle separator. It is understood that an electrostatic particle separator uses an electric charge to bias, and pull or push, particle from the flue gas stream to a point of collection, or removal from the flue gas conduit.

[0027] The system comprises at least one afterburner arrangement for combusting the pyrolysis gas. The system may comprise two, or further, afterburner arrangement arranged in series, wherein flue gas from a first afterburner arrangement outlet is routed to the inlet of a second afterburner arrangement. Alternatively, the afterburner arrangement may comprise two, or further, afterburner arrangement arranged to operate in parallel. When the system comprises two, or further, afterburner arrangements, two smaller sized afterburner arrangement may fill the function of one larger afterburner arrangement. When two, or further, afterburner arrangements are present, functional elements of the afterburners may be shared, such as the igniter, further reducing the cost manufacturing and installation of the system.

[0028] The afterburner arrangement comprises an inlet for receiving gas from the gasification reactor; or pyrolysis gas from the pyrolysis reactor. The inlet may comprise a flow control valve arranged upstream the inlet arranged for controlling the amount of gas received by the inlet.

[0029] The afterburner arrangement may further comprise a chamber and the flow conduit may be arranged inside the chamber. The chamber may also be regarded as a combustor. The combustor may thus comprise the flow conduit. The chamber may be insulated to maintain heat energy within the chamber and in the flow conduit. The chamber may also protect the environment outside the flow conduit, should the flow conduit rupture or fail.

[0030] The afterburner arrangement comprises an igniter for igniting the gasification or pyrolysis gas received by the inlet. The igniter initiates the process of combustion of the gas. During combustion the gas oxidizes and forms a combustion gas or flue gas. The igniter may be in the form of a pilot flame. Worded differently, the igniter may be an open-flame igniter. The igniter may ensure that combustion of the gas is initialized. The pilot flame may be provided with a as source of ignitable gas or fuel gas, such as natural gas, and an ignition device. Activation and deactivation of the pilot flame may be controlled using a control unit. The ignition device may also be a hot surface ignition device or a spark ignition device.

[0031] The ignitor may form part of the afterburner chamber, or the combustor. The ignitor may also be arranged upstream the combustor and fluidly connected to the combustor. After ignition of the gas mixture, the combustion or flue gas flows downstream to the combustor comprising the flow conduit. The ignitor may be arranged in the combustor, at a position upstream the flow conduit, adjacent the gasification gas inlet, the oxygen gas inlet and the fuel gas inlet.

[0032] The afterburner comprises an outlet fluidly connected to the combustor downstream of the inlet of the afterburner arrangement. The flue gas treatment arrangement is in fluid communication with the outlet for receiving flue gas. The outlet provides flue gas from the combustor of the afterburner arrangement to a flue gas treatment arrangement. The flue gas treatment arrangement comprises at least a cooler for cooling the flue gas, and a flue gas cleaning arrangement. The flue gas cleaning arrangement filters the flue gas and provides filtered flue gas. The filtered flue gas may subsequently be provided to a system outlet such as a stack, or funnel, wherein the filtered flue gas is provided to ambient environment.

[0033] In the combustor, the combustible gas mixture is combusted to form a flue gas. The combustion may be controlled by controlling the gas and oxygen mixture and the ignitor activation for igniting the combustible mixture. Hence, the combustor may provide for an optimal combustion of the combustible gas mixture. During combustion, the gas mixture is oxidized and an oxidation reaction takes place. The combustor comprises an outlet for providing a flue gas.

[0034] The combustor comprises a flow conduit for leading and retaining the gas mixture during combustion and immediately after combustion is started. The flow conduit is formed for leading or guiding the gas from the inlet to the outlet of the afterburner arrangement. The control of the combustion and the combustion and oxidation of the gas mixture may thereby be improved. The flow conduit provides for keeping the temperature of the flue gas within a predetermined temperature range during combustion. In addition, the flow conduit provides for obtaining that the time for which the combustion gas is maintained at the predetermined temperature range may be controlled. The time for which the combustion gas is maintained at the predetermined temperature range may be referred to as retention time. The retention time may preferably be at least 2s or longer.

[0035] The retention time and temperature range may be improved when the length of the flow conduit is longer than the shortest distance from the inlet to the outlet of the afterburner arrangement. When the combustion gas or flue gas is forced or lead to flow a longer length compared to a shortest distance between the afterburner inlet and outlet, an improved and more complete combustion of the gas mixture can be ensured. This provides an efficient retention time of the gas in the flow conduit. In addition, increasing the routing length of the flow conduit, decreases the size of the afterburner arrangement.

[0036] The combustor of the system further comprises a heater for heating the flow conduit. The flow conduit may be pre-heated using the heater, prior to activating the ignitor and combusting the pyrolysis gas. Pre-heating or addition heating may also be performed between waste batches. Additionally, the heater may be arranged to adjust heating of the flow conduit to match the inflow of pyrolysis gas from the pyrolysis reactor. One advantage of the heater is improved control of the combustor to ensure complete combustion of the pyrolysis gas, reducing the risk of pathogens of the hazardous waste from exiting the afterburner arrangement. The heater for heating the flow conduit provides for the flue gas to maintain, or be subjected to, a predetermined temperature during the retention time.

[0037] The heater may be in the form of a burner, or open flame heater. The heater may also be an electric heater, such as a resistance heater. The heater may further comprise a fan for blowing air over the resistance heater for providing a heated air flow. The heater may be arranged to flow the heated air over the flow conduit of the combustor, thereby heating the external surface area of the flow conduit. The heater, or multiple heaters, may be integrated into the flow conduit during manufacturing, such as resistance heating wires or cables wrapped or arranged around the flow conduit, or integrated into the material forming the flow conduit.

[0038] The heater may be an induction heater, and the flow conduit may be formed by a metal susceptible for induction heating. The induction heater may be arranged to inductively heat the flow conduit. The flow conduit may be made from a metal material with a melting point higher than the temperature the flow conduit is heated to. For example, the flow conduit may be made from steel or stainless steel or suitable alloys of steel. The induction heater coil may be in the form of an induction coil arranged externally to the combustor or flow conduit. Using an induction heater has one advantage in that the combustor and flow conduit may be arranged inside a casing, and the induction heater and coil may be arranged outside the casing. The induction heater provides improved process efficiency and energy saving since heating is localized to the flow conduit. An additional advantage is improved temperature control of the flow conduit. In addition, the heating is transmitted from the induction coil to the flow conduit in a contact-less manner, providing a closed system, thus reducing hazardous risk. In addition, the casing may be made having no serviceable parts arranged inside the casing, reducing costs and complexity of the casing.

[0039] When the heater is an induction heater, the heater may be arranged to heat both the gasification reactor or pyrolysis reactor; and the flow conduit at the same time, reducing system electric energy requirements. One induction heater control unit may then be used to control both heating of the gasification reactor or pyrolysis reactor; and the flow conduit.

[0040] The flue gas treatment arrangement comprises at least one cooler for cooling the flue gas.

[0041] The cooler is arranged in downstream fluid communication with the outlet connected to the combustor. The cooler may be at least one of a liquid-to-gas heat exchanger and an evaporative cooler. The liquid-to-gas heat exchanger comprises an inlet for receiving flue gas and an outlet for providing cooled flue gas. The heat exchanger further comprises an inlet for receiving cooling liquid such as water, and an outlet for releasing cooling liquid heated by the flue gas.

[0042] In one alternative, the liquid-to-gas heat exchanger may form part of a waste heat recovery (WHR) system. It is understood that a WHR may cool the flue gas by heat exchange between the flue gas and a cooling medium. The heated cooling medium may be recovered and utilized for a beneficial purpose. For example, the heat transferred to the cooling medium may be stored in an isolated liquid tank and used to preheat the pyrolysis reactor, the afterburner arrangement, or other components of the system.

[0043] In a further alternative, the waste heat recovery system may be a Rankine cycle waste heat recovery system. The waste heat recovery system may comprise the liquid-to-gas heat exchanger, a turbine, a condenser or second heat exchanger and a pump. The waste heat recovery system may be a closed system. This means that the cooling medium in the waste heat recovery system is circulated in a closed loop. The cooling medium may be a liquid in a first phase and a gas in a second phase. The liquid-to-gas heat exchanger may receive and cool the flue gas and transfer heat from the flue gas to the liquid of the waste heat recovery system. The heat exchanger may be connected to a turbine. The turbine may be arranged downstream the heat exchanger. The cooling medium flowing into the heat exchanger may be heated and change phase from a liquid phase to a gas phase. The gas may flow into the turbine through a turbine inlet. The gas may power and drive the turbine. The turbine may be connected through an output shaft to a generator. The generator may generate electricity or electric power.

[0044] The turbine may comprise an outlet. The turbine outlet may be connected to a condenser or second heat exchanger. In the condenser the gas is condensed to change phase from the gas phase to the liquid phase. The condenser may be actively or passively cooled. For example, the condenser may be a liquid-to-gas heat exchanger and the cooling of the gas may be done using a second cooling medium. The condenser may also be a gas-to-gas heat exchanger wherein the cooling medium gas is cooled by ambient air.

[0045] A pump may be arranged downstream the condenser. The pump may have a pump inlet and a pump outlet. The pump inlet may be fluidly connected to the condenser outlet. The pump outlet may be fluidly connected to the heat exchanger inlet, and the heat exchanger inlet may be arranged downstream the pump outlet. The pump may supply cooling medium to the heat exchanger to cool flue gas in the heat exchanger.

[0046] In a further example, a second turbine may be arranged downstream the afterburner arrangement. The second turbine may be arranged upstream the liquid-to-gas heat exchanger or the second turbine may be arranged downstream the liquid-to-gas heat exchanger. The second turbine may comprise an inlet and an outlet, wherein the inlet is fluidly connected to the afterburner outlet and arranged to receive flue gas.

[0047] The second turbine may be driven by the thermal and kinetic energy of the flue gas. The second turbine may extract work from the energy of the flue gas. Worded differently, the second turbine may be arranged to receive flue gas from the afterburner and recover thermal and / or kinetic energy from the flue gas and drive an electric power generator. The second turbine outlet may be fluidly connected to the heat exchanger inlet and arranged to provide flue gas to the heat exchanger or components downstream the second turbine such as the flue gas treatment arrangement discussed below. The second turbine may comprise an output shaft arranged to power an electric power generator to generate electric power. The generated electric power may be stored in a battery or electric energy storage to be used to heat the pyrolysis chamber, the afterburner arrangement or components of the system requiring electric power. This has the effect that the flue gas is cooled and heat or thermal energy and kinetic energy is recovered.

[0048] In addition, or alternatively, the cooler may be an evaporative cooler. The evaporative cooler comprises an injector for injecting a cooling liquid, such as water, into the flue gas stream. Injector may comprise a spray nozzle for dividing a cooling liquid provided to the injector into small drops or droplets having an increased surface area. Increasing the surface area of water drops, or droplets, coming into contact with the flue gas stream into the exhaust gas improves heat transfer between the flue gas and water. The evaporative cooler may also comprises a mixer for improving the mixing of the injected water to the flue gas stream. In addition, the water may be mixed with injected pressurized air to aid in the dispersion or breaking up of water drops into smaller drops, or droplets. This in turn provides an increase in evaporation efficiency and thus also improved cooling of the flue gas.

[0049] The flue gas treatment arrangement may comprise a combination of liquid-to-gas heat exchangers and evaporative coolers. The afterburner arrangement may further comprise a first flow control valve for controlling the flow amount of pyrolysis gas entering the inlet for receiving pyrolysis gas. The flow control valve may be connected to a control unit. Providing a flow control valve allows for adjusting the amount of pyrolysis gas entering the inlet, thereby the improving control of the combustion in the combustor. In addition, the first flow control valve allows for the flow amount of pyrolysis gas to be completely interrupted. This prevents non-combusted pyrolysis gas from flowing through afterburner arrangement should the afterburner arrangement fail.

[0050] The combustor of the afterburner arrangement may comprise an inlet for receiving an oxygen containing gas, such as air, or high content oxygen gas, and a second flow control valve for controlling the amount of oxygen containing gas entering the combustor. The second flow valve is controllable to adjust an amount of oxygen provided to the combustor for combusting the pyrolysis gas. Adjusting the flow of oxygen allows for ensuring complete combustion by adjusting the amount of oxygen in relation to the gasification gas or pyrolysis gas.

[0051] The combustor may additionally comprise a third flow control valve for providing a fuel gas, or natural gas to an inlet of the combustor.

[0052] The first flow control valve, the second flow control valve and / or the third flow control valve may be controlled to provide complete combustion of the combustion gas mixture. The flow control valves may be electrically connected to a control unit. The control unit may additionally be connected to flow sensors, temperature sensors and gas content sensors. The sensors may be arranged upstream and / or downstream the afterburner arrangement. The control unit may control the flow control valves based on sensor data from the sensor(s). This provides the advantage of improved control and increased efficiency of the system for treating hazardous waste.

[0053] The flue gas cleaning arrangement may further comprise at least one of: an ammonia solution injector for injecting an ammonia solution with the flue gas stream, and optionally a mixer for mixing the ammonia solution with the flue gas stream; an injector for injecting a dry sorbent into the flue gas for capturing acid gases; an injector for injecting activated carbon into the flue gas for capturing heavy metals, and wherein the filter is arranged to filter flue gas to segregate and remove particular matter from the flue gas. The flue gas may comprise harmful substances and particular matter, and thus needs to be filtered. The flue gas cleaning arrangement may comprise one, two or a combination of filterers and arrangement for cleaning the flue gas. An injector may be arranged to inject and mix an ammonia solution with the flue gas. The ammonia solution aids in nitrous oxide gas (NOx) reduction. The term NOx may represent several forms of nitrous oxide including nitric oxide (NO), nitrogen dioxide (NO2) and nitrous oxide (N2O). The amount of ammonia injected may be determined using sensor data from a NOx sensor arranged upstream the injector. In addition, an additional NOx sensor may be arranged downstream the injector and the mixer. The sensor data from the two NOx sensor may then be used for adjusting and controlling amount of ammonia injected improving and optimizing NOx reduction efficiency. The control unit may adjust the amount of injected ammonia solution based on the NOx sensor data. This reduces the risk of unreacted ammonia from being ejected from the system, such ejection of unreacted ammonia also commonly referred to as ammonia slip.

[0054] The flue gas cleaning arrangement may further comprise an injector, separate from the ammonia injector, for injecting a dry sorbent into the flue gas for capturing acid gases. The dry sorbent may be in the form of a powder or granulate. The dry sorbent aids in removal of acid constituents in the flue gas stream. The dry sorbents may be calcium (Ca) or sodium-based (Na) alkaline sorbents injected into the flue gas to remove acid gases (SO2, SO3 / H2SO4, HCI).

[0055] The flue gas cleaning arrangement may further comprise an injector, separate from the ammonia injector and the dry sorbet injector, for injecting activated carbon into the flue gas for capturing heavy metals. Injecting activated carbon into the flue gas stream further aids in the removal of heavy metals such as, but not limited to, Mercury (Hg). The injected activated carbon particles may be in powder of granulate form.

[0056] The flue gas cleaning arrangement may further comprise a filter being arranged to filter flue gas and to remove particular matter from the flue gas. The particular matter may include combustion particles, dry sorbent and activated carbon particles or granulate. The filter catches and removes the injected particular matter from the flue gas prior to the flue gas being ejected to ambient air.

[0057] The flow conduit may comprise plates or discs, arranged to form the flow conduit. The plates may be ceramic plates. The plates may also be in other material suitable for the high temperatures inside the flow conduit, such as steel, stainless steel or vermiculite. The heater, or multiple heaters, may be integrated into the plates or discs during manufacturing. The heater, or heaters, may be resistance heating wires or cables integrated into the plates or discs forming the flow conduit.

[0058] The flow conduit may comprise at least a first plate and at least a second plate, each having an inlet and an outlet and a flow channel extending within the plate between the inlet and outlet, and wherein the outlet of the first plate is arranged in upstream fluid communication with the inlet of the second plate, such that the flow of combustion gas exiting the first plate flow channel, subsequently enters the inlet of the second plate flow channel. The flow conduit may comprise two, or more, plates or discs in a stacked formation. A second plate is stacked, or arranged, on top of a first plate. A third plate is stacked, or arranged, on top of the second plate and so forth.

[0059] The flow conduit may alternatively comprise at least a first plate and at least a second plate arranged in a stacked formation, wherein the volume delimited between the first plate stacked on top of the second plate forms the flow conduit.

[0060] Worded differently, the plates are formed such that when a plurality of plates are stacked on top of each other, the volume delimited by two adjacent plates form the flow conduit. There is thus no need to form flow channels internally or within the respective plates. The flow conduit is formed by the delimited volume, or flow channels, being an effect of the shape of the plates when the plates are stacked on top of each other. The plates may thereby be made without internally arranged flow channels reducing the complexity of the plates. This further reduces the cost for manufacturing the plates since only one type of plates needs to be manufactured. Depending on the gas flow amount more plates or discs may be added to the stack, to extend the length of the flow conduit. In addition, the arrangement allows for improved serviceability of the flow conduit, since a damaged or blocked plate may be removed from the stack and replaced. In addition, a removed plate may be removed, serviced or repair and refurbished to be re-installed in the stack of the current system, or a different system.

[0061] Alternatively, each plate may comprise an inlet, an outlet and flow channel extending internally in the plate, between the inlet and the outlet. When the plates are stacked an outlet of the first plate is in fluid communication with the inlet of a second plate. The flow conduit thereby guides the pyrolysis gas through the first plate and subsequently through each additional plate in the stack of plates. This leads and retains the pyrolysis gas during combustion aiding in reducing the risk of incomplete combustion and that pathogens exit the flow conduit of the afterburner arrangement. The number of plates of the stack of plates may be adapted based on the size and pyrolysis amount generating properties of the pyrolysis reactor. The plates may be circular in shape and the inlet and outlet may be centrally arranged. The plates may be disc shaped. The inlet and outlet may be concentric around the circular plate central axis. The central axis of the circular plate may also be referred to as the axis the circular plate revolves around, or the revolving axis of the circular plate.

[0062] A flow channel extending internally, and within a disc, may extend radially outwards, from the centrally arranged inlet, to a radial outer edge portion of the disc, wherein the flow channel reverses direction and extends radially inwards to the centrally arranged outlet.

[0063] The flow conduit may be formed by plates, or discs, having the internally arranged flow channels, combined with the plates shaped such that flow channels are formed by the volume delimited by two adjacent plates. Thus flow channels are provided both within the plates and in the volume delimited by two adjacent plates.

[0064] The number of plates may be adapted based on the amount of flow of flue gas / combustion gas to be treated by the system.

[0065] The flow conduit may alternatively comprise a bundle of parallelly arranged straight tubes joined together at the tube ends to form a single continuous flow conduit having a shared single inlet and single outlet. The flow conduit may comprise a tubular unit having a series of parallelly arranged tubes, or pipes, having curved bends at their ends to maintain parallelism. The tubes, or pipes, together form one continuous flow conduit. The flow conduit thus has a length being longer than the shortest linear distance between the flow conduit inlet and outlet. The tubes, or pipes, may be made from the metal material suitable for induction heating as disclosed earlier. In one example, the tubes are steel or copper tubes. Arranging the flow conduit as a bundle of parallelly arranged straight tubes or as a tubular unit, provides a compact flow conduit. A compact flow conduit may be heated using smaller induction heater coil. In addition, when the flow conduit is in the form of a bundle of parallelly arranged straight tubes or a tubular unit, the flow conduit may be arranged inside the chamber. The afterburner chamber may thus be made compact. Thus, reducing space constraint for installing the afterburner of the system, and further improving heat retention inside the chamber and of the flow conduit, and decreasing the heat amount needed to be provided by the heater, to maintain an operational temperature of the flow conduit. The operational temperature may be regarded as the temperature needed in order to provide a complete combustion of the gas in the flow conduit. Additional forms for the flow conduit are also possible. For example, the flow conduit may comprise a tubular unit comprising a tube that is formed in a plane in a spiral patten around a central axis. This provides a significantly flat flow conduit allowing for an afterburner arrangement having a low height.

[0066] Alternatively, the flow conduit may comprise a tubular unit comprising a tube formed having a helical shape.

[0067] The flow conduit may be formed by a chamber having a chamber inlet and chamber outlet, wherein the chamber being filled with silicon carbide granules. The silicon carbide may also be in the form of pellets, balls, or spheres. The chamber comprising the silicon carbide granules, form flow channels in the interstice between adjacent granules, thereby increasing a flow length the combustion gas needs to travel between the inlet and outlet, compared to the shortest distance from the inlet to the outlet of the chamber of the afterburner arrangement when the chamber is devoid of granules. The chamber may in addition comprise a plurality of steel rods or steel pipes dispersed or arranged within the chamber. The steel rods may thus be heated using an induction heating coil and transfer heat from the rods to the silicon carbine granules. Alternatively, the silicon carbide granules may be replaced with steel granules, pellets, or spheres. The granules may further be from other materials having high thermal conductivity and suitable for heating to the high temperature experiences in the chamber. Additionally, the silicon carbide granules may be mixed with steel granules reducing the need for providing steel rods. The steel granules may then be heated by the induction heater and heat from the steel granules may be transferred to the surrounding silicon carbide granules.

[0068] According to a second aspect, a method using the system according to the first aspect of the present invention is provided, the method comprising the steps of:

[0069] - gasifying the hazardous waste in the gasification reactor by heating the waste in an oxygen-deprived environment to generate a gas,

[0070] - mixing the gas with a source of oxygen to form a combustible gas mixture,

[0071] - routing the gas mixture into the afterburner,

[0072] - igniting the gas mixture using the ignitor to form a combustion gas,

[0073] - flowing the combustion gas through the flow conduit to produce flue gas,

[0074] - providing the flue gas to the flue gas treatment arrangement,

[0075] - cooling the flue gas using at least the cooler,

[0076] - filtering the flue gas using at least the filter. The method may further comprise, during the step of flowing the combustion gas through the flow conduit, the combustion gas flowing through the flow conduit is controlled to have a temperature in the range of 700 to 1300 °C, such as 850 to 1300 °C, by heating the flow conduit.

[0077] The method may further comprise the step of: before gasifying the hazardous waste in the gasification reactor by heating the waste in an oxygen-deprived environment to generate a gas, heating the waste to a predetermined temperature, or predetermined temperature range, and maintaining the waste at the predetermined temperature, or within the predetermined temperature range, for a predetermined amount of time. This allows for moisture to vaporize and to be removed from the waste in the pyrolysis reactor further improving waste treatment by reducing moisture in the pyrolysis gas. The predetermined temperature range may be above or about the boiling point of water. The predetermined temperature range may be at least 60 °C, such as 60-130 °C.

[0078] The method may further comprise, discharging the vapor from the pyrolysis reactor. Discharging may be done using the steam outlet described above in relation to the system.

[0079] It is specified above that the method comprises cooling the flue gas using at least one cooler. Cooling may be performed by extracting heat, or transferring heat, from the flue gas to a cooling medium using at least one cooler or heat exchanger forming part of the waste heat recovery system. Additionally, or alternatively, the step of cooling may be performed by flowing the flue gas through a waste heat recovery turbine, or second turbine.

[0080] BRIEF DESCRIPTION OF THE DRAWINGS

[0081] A more complete understanding of the abovementioned and other features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments in conjunction with the appended drawings, wherein:

[0082] Fig. 1 shows a schematic view of a system for treating hazardous waste by pyrolysis, afterburning and flue gas treatment according to a first aspect of the present invention; Fig. 2a shows a first embodiment of an afterburning device of the system in Fig. 1 , according to the first aspect of the present invention;

[0083] Fig. 2b shows a top-down view of a first ceramic disc shown in Fig. 2a;

[0084] Fig. 2c shows a top-down view of a second ceramic disc shown in Fig. 2a;

[0085] Fig. 3a shows a second embodiment of an afterburning device of the system in Fig. 1 , according to the first aspect of the present invention;

[0086] Fig. 3b shows a top-down view of a ceramic disc shown in Fig. 3a;

[0087] Fig. 4 shows a third embodiment of an afterburning device of the system in Fig. 1 , according the first aspect of the present invention.

[0088] Fig. 5 shows a fourth embodiment of an afterburning device of the system in Fig. 1 according to the first aspect of the present invention.

[0089] Fig. 6 shows a method for treating hazardous waste according to a second aspect of the present invention, using the system according to the first aspect of the present invention;

[0090] Fig. 7a shows a partial view of the heat exchanger in Fig. 1 forming part of waste heat recovery system;

[0091] Fig. 7b shows an alternative waste heat recovery system of that shown in Fig. 7a further comprising a turbine;

[0092] Fig. 7c shows an alternative waste heat recovery system to that of Fig. 7b;

[0093] Fig. 8 shows an alternative system to that of Fig. 1 further comprising a particle separator;

[0094] Fig. 9 shows an alternative method for treating hazardous waste according to the second aspect of the present invention, using the system according to the first aspect of the present invention.

[0095] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the respective embodiments, whereas other parts may be omitted or merely suggested. Any reference number appearing in multiple drawings refers to the same object or feature throughout the drawings, unless otherwise indicated. Letter suffixes of reference numbers indicate single individual objects or features among the objects and features having the same number.

[0096] DETAILED DESCRIPTION

[0097] Fig. 1 shows an embodiment of a system for treating hazardous waste 1 according to a first aspects of the present invention. The system 1 comprises a gasification reactor 10 in the form of a pyrolysis reactor 10, an afterburner arrangement 40 and a flue gas treatment arrangement 80. The afterburner arrangement 40 is arranged in downstream fluid communication with the pyrolysis reactor 10. The flue gas treatment arrangement 80 is arranged downstream and in fluid communication with the afterburner arrangement 40.

[0098] The pyrolysis reactor 10 is shown comprising a chamber 12. The pyrolysis reactor 10 receives hazardous waste material provided to the pyrolysis reactor 10 through an opening 14. The pyrolysis reactor 10 further comprises a heater 16 for heating the hazardous waste material to generate a pyrolysis gas. The pyrolysis gas is provided from the pyrolysis reactor to an outlet 18 of the pyrolysis reactor 10. The pyrolysis reactor 10 further comprises an inlet 20 for receiving an oxygen-deprived gas for displacing and forcing the pyrolysis gas to flow from the pyrolysis reactor 10 through a first pipe conduit 22 to the afterburner arrangement 40. In addition, the oxygen-deprived gas aids in the pyrolysis reaction by preventing the hazardous waste material from combusting. The oxygen-deprived gas is provided from a first gas pressurized tank 24. The pressure and flow amount of the oxygen-less gas provided to an inlet 20 of the pyrolysis reactor 10 is adjusted and controlled by a control valve 26.

[0099] The afterburner arrangement 40 is shown in Fig. 1 as comprising a chamber 42 having an inlet 41 for receiving the pyrolysis gas. The chamber 42 may also be referred to as a combustor 42. The inlet is in fluid communication with an upstream arranged pyrolysis gas flow adjustment valve 64. The chamber 42 is further shown having an outlet 46 for providing a flue gas to the flue gas treatment arrangement 80. The outlet 46 is arranged in downstream fluid communication with the inlet 44. The chamber 42 further comprises an oxygen gas inlet 48 in downstream fluid communication with an oxygen gas tank 50. The pressure and flow amount of the oxygen gas provided to an oxygen inlet of the chamber is adjusted and controlled by an oxygen gas control valve 52.

[0100] The afterburner chamber 42 may comprise additional equipment such as pressure safety valves, or pressure relief valves opening if the pressure inside the chamber exceeds a threshold pressure, to flow gas from the chamber to a stack, or chimney, and prevent explosive rupture or leakage of the chamber (not shown).

[0101] In addition, Fig. 1 shows the chamber 42 comprising a gaseous fuel inlet 54, e.g. natural gas inlet 54. The natural gas inlet 54 is connected in fluid downstream communication with a pressurized natural gas tank 56 through a natural gas control valve 57. Arranged between the natural gas control valve and the pressurized natural gas tank, a pressure regulator 58 is shown. The natural gas control valve 57 is adjustable to control the flow amount and pressure of the natural gas received by the chamber inlet 54. In addition, the pressurized natural gas tank 56 is connected to an ignitor 60 through an additional gas control valve 59. The ignitor 60 is shown as a pilot flame 60. The pilot flame 60 is controllable to inject natural gas from the pressurized natural gas tank 56 to the chamber 42 and ignite the natural gas. The ignited natural gas, in turn, ignites the pyrolysis gas.

[0102] Fig. 1 shows a heater 62 for heating the chamber 42 of the afterburner arrangement 40. The heater 62 is shown as a fan heater 62 for heating and flowing heated air into the chamber 42. The heater 62 is also used for pre-heating the chamber 42 during start-up of the system 1

[0103] Fig. 1 further shows the flue gas cleaning arrangement 80 comprising a liquid-to-gas heat exchanger 82, an ammonia solution injector and mixer 84; an evaporative cooler 86; an injector for injecting a dry sorbent 88; an injector for injecting activated carbon 90 and a filter 92. The liquid-to-gas heat exchanger 82 is shown arranged downstream the afterburner chamber outlet 46. The liquid-to-gas heat exchanger 82 comprises a flue gas inlet 94 and a flue gas outlet 96. The liquid-to-gas heat exchanger 82 is cooled using water, provided to a water inlet 98 of the liquid-to-gas heat exchanger 82. The liquid-to- gas heat exchanger 82 is further shown comprising a water outlet 100 for ejecting water heated by the flue gas. The flue gas is thereby cooled by the liquid-to-gas heat exchanger 82, and the temperature of the flue gas at the outlet 96 is lower than a temperature of the flue gas at the flue gas inlet 94.

[0104] Arranged downstream and in fluid communication with the liquid-to-gas heat exchanger 82 is an ammonia injector and mixing arrangement 84. The arrangement comprises an injector 102 for injecting a solution comprising ammonia and a mixer 104 for aiding in the dispersion of the ammonia solution in the flue gas stream. The ammonia injector 102 is connected to a source of ammonia solution 106, shown in the form of an ammonia storage tank 106. Arranged downstream the ammonia tank 106 is a pump 108 for pressurizing the ammonia solution. The pump 108 may also provide pressurized ammonia solution to a pressure vessel such as pressure storage tank or hydraulic accumulator (not shown). Downstream the pump 108 is a control valve 110 for controlling the injection amount of ammonia into the flue gas stream and the mixer 104. The injection of ammonia aids in reducing nitrous oxide (NOx) gas in the flue gas stream.

[0105] Arranged downstream the ammonia injector and mixer is shown an additional cooler 86 shown as an evaporative cooler 86. The evaporative cooler 86 comprises an injector 112 for injecting a mixture of water and pressurized air. The pressurized air may be provided by a compressor 114 connected to a pressurized air tank 116. Downstream the pressurized tank 116 and upstream the injector 112 is a compressed air control valve 118. In addition, the evaporative cooler 86 is shown comprising a water control valve 120. The two valve 118, 120 are controllable to adjust the water spray and air mixture amount, the pressure and / or the spray pattern. In addition, the valves 118, 120 may be controlled to discontinue the injection when cooling is not required.

[0106] Downstream the evaporative cooler 86 is shown a first injector arrangement 88 and a second injector arrangement 90 for injecting a dry sorbent into the flue gas. The second injector arrangement 90 is shown arranged downstream the first injector arrangement 88. The dry sorbent injected by the first injector arrangement 88 aids in capturing acid gases contained in the flue gas stream. Each of the first injector arrangement 88 and the second injector arrangement 90 comprises a dry sorbent storage tank 122 for storing a dry sorbent. Connected to an outlet of the dry sorbent tank is a dry sorbent portioning, or feeding, arrangement 124. Fig. 1 shows the portioning, or feeding arrangement, in the form of a hopper feeder 124. Other suitable feeders for granular material are also possible, such as a screw feeder. The dry sorbent portioning, or feeding, arrangement 122 is controllable to inject an amount of dry sorbent in relation to an amount of flue gas flow in the flue gas cleaning arrangement.

[0107] The second injector arrangement 90 injects dry sorbent in the form of activated carbon granulate or powder, for capturing heavy metals such as mercury (Hg).

[0108] The injected dry sorbent, injected by the first injector arrangement 88 and the second injector arrangement 90, is carried by the flue gas stream to a filter 92 for filtering the flue gas to remove the dry sorbents and other particular matter contained in the flue gas stream. The filter 92 is arranged downstream the first injector arrangement 88 and the second injector arrangement 90. The filter 92 has an inlet 126 for receiving the flue gas and an outlet 128 for providing filtered flue gas to a system outlet, such as a stack or funnel, to ambient air (not shown). In addition, the filter 92 comprises an outlet for removing dry sorbents 130, and particular matter filtered from the flue gas stream, by filter.

[0109] Fig. 2a shows a first embodiment of the afterburner arrangement 40 of the system disclosed in Fig. 1 according to the first aspect of the present invention. The afterburner arrangement 40 is shown having a cylindrical body 140 revolving around a central axis A. The cylindrical body 140 forms the chamber 42, enclosing a chamber volume 42. The chamber 42 may also be referred to as a combustor 42. The chamber 42 having an inlet 41 for receiving pyrolysis gas. The chamber 42 further comprises an outlet 46 for providing flue gas. The chamber 42 extends in a direction parallel to the central axis A shown. The inlet 41 is shown arranged at a first end of the chamber 42. The outlet 46 is arranged at an opposite longitudinal end of the chamber 42. When the afterburner is in use, the gas flow is from the inlet 41 to the outlet 46.

[0110] Fig. 2a further shows an ignitor 60 in the form of a pilot flame arrangement 60 arranged at the same longitudinal end as the inlet 41. Arranged adjacent the ignitor 60 is a heater 62. The heater 62 is in shown as a fan and resistive heater assembly 62. The heater 62 is arranged for providing additional heat to heat the internal volume 42 of the afterburner chamber 42 as well as the fluid conduit contained within the chamber 42. In addition, the afterburner chamber may comprise a combustible gas inlet 54 for receiving a combustible gas such as natural gas. In addition, the chamber shown in Fig. 2a shows an oxygen gas inlet 48, for receiving an oxygen-containing gas.

[0111] The chamber further comprises a plurality of ceramic plates 142, 144. The ceramic plates are shown as ceramic discs 142, 144 mounted in a stacked arrangement. The chamber comprises first ceramic discs 142 having a first shape. The chamber also comprises second ceramic discs 144 of a second shape, the second shape being different from the first shape. The chamber shown in Fig. 2a shows five, first ceramic discs and five, second ceramic discs. The ceramic discs 142, 144 are stacked, having a first ceramic disc 142 followed by a second ceramic disc 144, in a repeating pattern in a direction parallel to the axis A. The discs 142, 144 are arranged parallel to each other. The ceramic discs 142, 144 are mounted and secured within the chamber 42 using a first securing rod 146 and a second securing rod 148. The rods 146, 148 extend in a direction parallel to the axis A. The rods 146, 148 are secured to the chamber 42 at the longitudinal ends of the rods 146, 148. Fig. 2a-2c shows two rods 146, 148, however preferably three rods spaced apart by an angle of 120 degrees are used.

[0112] Fig. 2b, shows a top-down view of a first ceramic disc 142. The first ceramic disc 142 comprises a centrally arranged opening 150 for receiving a combustion gas flow. The centrally arranged opening 150 has an opening diameter DD. In addition, Fig. 2b shows the openings 152 for receiving securing rods 146, 148. The first ceramic disc 142 comprises an outer diameter D. Fig. 2b shows two openings 152, however preferably three openings, matching the number of rods that are used, wherein the openings are spaced apart by an angle of 120 degrees.

[0113] Fig. 2c, shows a top-down view of the second ceramic disc 144. The second ceramic disc 144 is devoid from a centrally arranged opening. The second ceramic disc 144 shows two openings 152' for receiving the securing rods 146, 148. Fig. 2c shows two openings 152', however preferably three openings, matching the number of rods that are used, wherein the openings are spaced apart by an angle of 120 degrees. In addition, Fig. 2c shows the outer diameter d of the second ceramic disc 144. The outer diameter D of the first ceramic disc 142 is larger than the outer diameter d of the second ceramic disc 144, D>d.

[0114] Returning to Fig. 2a, spacers 156 for maintaining the discs 142, 144 at a predetermined distance from each other are shown. The spacers 156 may also be referred to as bushings 156. The discs 142, 144 are mounted in the chamber 42 by threading the discs onto the securing rods 146, 148 such that the rods 146, 148 protrude through the disc openings 154, with spacers 156 threaded onto the rods 146, 148 between two adjacent discs 142, 144.

[0115] Returning to Fig. 2a, the different outer diameters D of the first ceramic discs 142 and d of the second ceramic disc 144 in combination with the spacing due to the spacers 156, form a flow conduit 158 for the flow of combustion gas. The spacing, or volume, delimited between the first ceramic disc stacked on the second ceramic plate forms the flow conduit 158. The combustion gas flows radially outwards, axially along the axis A of the chamber 42 and subsequently radially inwards. The flow conduit 158 thus leads and retains the combustion gases in the flow conduit 158 during combustion. The length of the flow conduit is thereby made longer than a shortest distance from the inlet to the outlet of the afterburner arrangement. Fig. 2a, schematically shows the combustion gas flow using dashed and arrowed lines.

[0116] Fig. 3a shows a second embodiment of an afterburning arrangement 40' of the system in Fig. 1 according to the first aspect of the present invention. The second embodiment differs from the first embodiment in that the first ceramic disc 142' and the second ceramic disc 144' have the same shape and form. The first ceramic disc 142' and the second ceramic disc 144' are thus identical. For the afterburner arrangement 40' in Fig. 3a, the flow conduit 158'is formed by flow channels extending inside or internally within the first ceramic disc 142' and the second ceramic disc 144'. Fig. 3a shows the flow channel dividing the ceramic disc 142', 144' into an inner portion 159 and an outer portion 157 wherein the inner portion 159 and the outer portion 157 are connected at points between the inner 159 and outer portion 157 to secure the inner portion 159 to the outer portion 157 (not shown). Each ceramic disc 142', 144' comprises an inlet 150' and an outlet 160, the outlet 160 arranged in downstream communication with the inlet 150'. The flow channel extends between the inlet 150' and the outlet 160. A plurality of stacked ceramic discs 142', 144' are shown, stacked directly on top of each other, without any spacers or bushings present as for the embodiment of Fig. 2a. Fig. 3a shows five stacked ceramic disc 142, 144'. The outlet 160 of the first ceramic disc 142' is directly connected to the inlet 150' of the second ceramic disc 144'. The flow channels formed within the respective ceramic disc 142', 144' are thus joined together to form one flow conduit that leads and retains the combustion gases during combustion.

[0117] The ceramic discs 142', 144' also comprise a protruding ring 162 and a matching recessed ring 164. When the ceramic discs 142', 144' are stacked, the protruding ring 162 and matching recessed ring 164 prevent radial, or transverse the axis A, movement.

[0118] Fig. 3b, shows a top-down view of a ceramic disc of the second embodiment. The ceramic disc 142', 144' has an outer diameter DB, matching the internal diameter of the chamber 42. Fig. 3b further shows the opening 150' having a diameter Db.

[0119] Fig. 4, shows a third embodiment of the afterburner arrangement of the system in Fig. 1, according the first aspect of the present invention. Fig. 4 shows a cross-sectional view of the afterburner arrangement 40'' comprising a cylindrical chamber 42'. The chamber 42' may also be referred to as a combustor 42'. The chamber 42' comprises an inlet 152", and an outlet 166 in fluid downstream communication with the inlet 152". Fluidly connected upstream the afterburner chamber is an igniter arrangement 60', arranged upstream the chamber inlet 152". The third embodiment thus shows that the ignitor arrangement 60' is separate from the afterburner chamber 42' or combustor 42'. The ignitor arrangement 60' is shown comprising an ignition and mixing chamber 170. The ignition and mixing chamber 170 comprises an inlet 172 for receiving the pyrolysis gas and an inlet 174 for receiving an oxygen containing gas. In addition, the ignition and mixing chamber 170 comprises an inlet 176 for receiving natural gas or other hydrocarbon (hydrogen carbon) gas, for promoting ignition of the pyrolysis gas. Fig. 4 further shows an ignition source 60 in the form of a pilot flame 60. After ignition of the mixture of pyrolysis gas, oxygen containing gas and the natural gas the combustion of the continues and completes in the afterburner chamber 42'. The chamber 42' further comprises induction rods 178 extending parallel to the axial direction of the cylindrical chamber. Silicon carbide granulate 168 is dispersed inside the chamber 42'. The interstice 180 between the silicon carbide granulates form a flow conduit 180 for leading and retaining the combustion gas during combustion.

[0120] Fig. 4 further shows an induction heater in the form an induction current producing controller 182 and a helical coil 184 arranged around the chamber 42' and electrically connected to the induction current producing controller 182. The induced magnetic current heats the induction rods 178. The heated rods 178 in turn transfer heat to the silicon carbide granulate 168. The heated silicon carbide granulate 178 in turn heats the combustion gas flowing through the chamber from the chamber inlet 152'' to the outlet 166. The gas provided to the outlet 166 subsequently enters the flue gas treatment arrangement.

[0121] Fig. 5 shows a fourth embodiment of an afterburning arrangement 40'" of the system in Fig. 1 according to the first aspect of the present invention. The afterburner arrangement 40'" shown in Fig. 5 comprises an insulating chamber 42" and a flow conduit 186 arranged internally in the chamber 42". The fourth embodiment thus shows that the ignitor arrangement 60' is separate from the afterburner chamber 42" or combustor 42" The flow conduit 186 is in the form of a tubular unit 186 having a series of parallelly arranged tubes 188, or pipes, having curved bends 190 at their ends to maintain parallelism. Fig. 5, shows one flow conduit, however the afterburner chamber may comprise more flow conduits, such as two to three, or more. The tubes 188, or pipes, together form one continuous flow conduit 186. The tubes 188, or pipes, are made from a metal material suitable for induction heating by the helical induction coil 184. The flow conduit is connected to the ignitor arrangement 60' shown in Fig. 4, having an ignition and mixing chamber170.

[0122] Fig. 6 shows a method for treating hazardous waste according to a second aspect of the present invention, using the system according to the first aspect of the present invention shown in Fig. 1.

[0123] The method comprises the first step of pyrolyzing hazardous waste in a pyrolysis reactor by heating the hazardous waste in an oxygen-deprived environment (601). After generation of the pyrolysis gas, the method comprises the step of mixing the pyrolysis gas with a source of oxygen to form a combustible gas mixture (602). Following the mixing of the pyrolysis gas, the pyrolysis gas is then routed, or lead, into the afterburner arrangement (603). The afterburner arrangement is an afterburner according to any one of first through fourth embodiments of the first aspect of the invention disclosed in relation to Figs. 2-5. The method further comprises the step of igniting the gas mixture using the ignitor to form flue gas (604) and flowing the flue gas through the heated flow conduit (605). After combustion of the combustible gas mixture the method comprises the step of providing the flue gas to a flue gas treatment arrangement (605), for cooling the flue gas using at least one cooler (606) and filtering the flue gas using at least one filter (607). The cooler is at least one of the coolers disclosed in relation to Fig. 1, and the filter is at least one of the filters disclosed in relation to Fig. 1.

[0124] Fig. 7a shows a partial view of the heat exchanger 82 shown in Fig. 1 forming part of a waste heat recovery system 200. The heat exchanger 82 comprises an inlet 98 for receiving a colling medium, and an outlet 100 for discharging the cooling medium. The outlet 100 is fluidly connected to a turbine inlet 204 on a turbine 202. The turbine 202 receives cooling medium from the heat exchanger 82 that has changed from a liquid to a gas phase, or vapor phase. The cooling medium drives the turbine 202. The turbine 202 further comprises an output shaft 206 that drives an electric generator for generating an electric power (not shown). After exerting a driving power on the turbine 202 the cooling medium is discharged from a turbine outlet 208. The turbine outlet 208 is fluidly connected to, and arranged upstream, a condenser 210, or second heat exchanger 210. The turbine outlet 208 is connected to a condenser inlet 212. The condenser 210 further comprises an outlet 214. Additionally, the condenser 210 comprises a cooling liquid inlet 216 and cooling liquid outlet 218. The cooling liquid inlet 216 receives a cooling liquid, such as water, to cool and condense the cooling medium of the waste hear recovery system 200. The cooling liquid is subsequently discharged through the cooling liquid outlet 218. The cooling medium entering the condenser 210 is cooled to change a phase from vapor, or vapor and liquid mixture, to a liquid phase. The condenser outlet 214 is fluidly connected to a pump 220. The condenser outlet 214 is arranged upstream the pump 220. The pump 220 comprises an inlet 222 and an outlet 224. The pump 220, pumps and provides the cooling medium to the heat exchanger inlet 98. The heat exchanger 82, the turbine 202, the condenser 210 and the pump 220 thereby form the waste heat recover system 200 of a Rankine cycle type.

[0125] Fig. 7b shows a partial view of a further example of the waste heat recovery system 200, wherein a second turbine 226 is arranged in the flue gas conduit upstream the heat exchanger 98. The second turbine 226 is arranged downstream the afterburner arrangement. The second turbine 226 has an inlet 228 and an outlet 230, wherein the inlet 228 is fluidly connected to the afterburner outlet and arranged to receive flue gas. The second turbine 226 has an output shaft 232 arranged to power an electric generator to generate electric power (not shown). As heat energy in the flue gas is converted to rotational power of the output shaft 232, the temperature of the flue gas is reduced.

[0126] Fig. 7c shows a further example wherein only the second turbine 226 is used for waste heat recovery. This means that the heat exchanger 98 is only used to cool the flue gas after passing through the second turbine 226. Worded differently, the heat exchanger 82 does not form part of a waste heat recovery system in this example.

[0127] Fig. 8 shows the system of Fig. 1 with an added particle separator 250 arranged downstream the pyrolysis reactor 10 and upstream the afterburner arrangement 40. The particle separator 250 is arranged to filter out any particles or soot and prevent depositions of such particles in the afterburner arrangement 40 or further components of the system arranged downstream the afterburner arrangement 40. The particle separator 250 is shown in the form of a cyclone separator 250. The particle separator 259 comprises an inlet 244 for receiving pyrolysis gas from the pyrolysis reactor 10 and any particles. The particle separator 250 is further shown comprising a pyrolysis gas outlet 246 and a particle outlet 248. In the particle separator 250, particles are separated from the pyrolysis gas and collected in the bottom of the particle separator 250. Any collected particles may then be removed from the particle separator 250 through the particle outlet 248. Particle free pyrolysis gas, or pyrolysis gas with reduced amounts of particles, compared to pyrolysis gas entering the particle separator 250, is discharged from the pyrolysis gas outlet 246. The pyrolysis gas outlet 246 is fluidly connected to the afterburner arrangement inlet 41.

[0128] Additionally, Fig. 8 shows that the pyrolysis reactor 10 comprises a steam outlet 240, or second outlet 240. The steam outlet 240 is arranged at the top of the pyrolysis reactor 10. The steam outlet 240 may be fluidly connected to a controllable steam valve 242. The steam valve 242 may be set in a closed position or an open position. The steam outlet 240 and steam valve 242 are arranged to allow steam, or water vapor, to be removed, or discharged, from the pyrolysis chamber 10. When the pyrolysis reactor 10 is loaded with waste and the waste is heated, above a vaporization temperature, water in the waste will vaporize and form steam, or water vapor. The water vapor is discharged from the pyrolysis reactor 10 via the steam outlet 242. Water vapor is thereby removed from the waste. After the removal water vapor from the waste the temperature is increased to form the pyrolysis gas from the waste. Fig. 9 shows the method of Fig. 6, further comprising the step of: before, or prior to, gasifying the hazardous waste in the gasification reactor by heating the waste in an oxygen-deprived environment to generate a gas, heating the waste to a predetermined temperature, or predetermined temperature range, and maintaining the waste at the predetermined temperature, or within the predetermined temperature range, for a predetermined amount of time, to generate steam or water vapor and discharging the vapor from the pyrolysis reactor through the steam outlet of the pyrolysis reactor (600).

[0129] FEASABLE MODIFICATIONS

[0130] The invention is not limited only to the embodiments described above and shown in the drawings, which primarily have an illustrative and exemplifying purpose. This patent application is intended to cover all adjustments and variants of the preferred embodiments described herein, thus the present invention is defined by the wording of the appended claims. Thus, the equipment may be modified in all kinds of ways within the scope of the appended claims.

[0131] It shall also be pointed out that all information about / concerning terms such as above, under, upper, lower, etc., shall be interpreted / read having the equipment oriented according to the figures, having the drawings oriented such that the references can be properly read. Thus, such terms only indicate mutual relations in the shown embodiments, which relations may be changed if the inventive equipment is provided with another structure / design.

[0132] It shall also be pointed out that even thus it is not explicitly stated that features from a specific embodiment may be combined with features from another embodiment, the combination shall be considered obvious, if the combination is possible.

[0133] Throughout this specification and the claims which follows, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or steps or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims

Claims1. A system (1) for treating waste, preferably hazardous medical waste, the system (1) comprising: a gasification reactor (10) for receiving waste and generating a gas; at least one afterburner arrangement (40, 40', 40", 40'") comprising: an inlet (41, 172) for receiving the gas from the gasification reactor (10), an inlet (48, 174) for receiving and mixing the gas with a source of oxygen to form a combustible gas mixture, an igniter (60, 60') for igniting the combustible gas mixture received by the inlet, a combustor for combusting the combustible gas mixture to form flue gas, and an outlet connected to the combustor for providing the flue gas, a flue gas treatment arrangement in fluid communication with the outlet for receiving flue gas, the flue gas treatment arrangement comprising a cooler for cooling the flue gas, and a flue gas cleaning arrangement, for filtering the flue gas and providing filtered flue gas, and wherein the combustor comprises a flow conduit for leading and retaining the flue gas, and wherein the combustor comprises a heater for heating the flow conduit.

2. The system according to claim 1 , wherein the length of the flow conduit is longer than the shortest distance from the inlet to the outlet of the afterburner arrangement.

3. The system according to any preceding claim, wherein the gasification reactor is a pyrolysis reactor, and the gas is pyrolysis gas.

4. The system according to any preceding claim, wherein the heater is an induction heater, and the flow conduit is formed by a metal susceptible for induction heating, wherein the induction heater is arranged to inductively heat the flow conduit.

5. The system according to any preceding claim, wherein the cooler is at least one of a liquid-to-gas heat exchanger, and an evaporative cooler.

6. The system according to any preceding claim, wherein the flow conduit comprises at least a first plate and at least a second plate, each having an inlet and an outlet and aflow channel extending within the plate between the inlet and outlet, and wherein the outlet of the first plate is arranged in upstream fluid communication with the inlet of the second plate, such that the flow of combustion gas exiting the first plate flow channel, subsequently enters the inlet of the second plate flow channel.

7. The system according to any preceding claim, wherein the flow conduit comprises at least a first plate and at least a second plate arranged in a stacked formation, wherein the volume delimited between the first plate stacked on top of the second plate forms the flow conduit.

8. The system according to claims 1-5, wherein the flow conduit comprises a bundle of parallelly arranged straight tubes joined together at the tube ends to form a single continuous flow conduit having a shared single inlet and single outlet.

9. The system according to any one of claims 1-5, wherein the flow conduit is formed by a chamber having a chamber inlet and chamber outlet, the chamber being filled with a granular material such as silicon carbide granules.

10. The system according to any preceding claims, wherein the afterburner arrangement further comprises a first flow control valve for controlling the flow amount of pyrolysis gas entering the inlet for receiving pyrolysis gas.

11. The system according to any preceding claim, wherein the combustor comprises an inlet for receiving an oxygen containing gas, such as air, and a second flow control valve for controlling the amount of oxygen containing gas entering the combustor.

12. The system according to any preceding claim, wherein the flue gas cleaning arrangement further comprises at least one of: an ammonia solution injector for injecting an ammonia solution with the flue gas, and optionally also a mixer for mixing the ammonia solution with the flue gas; an injector for injecting a dry sorbent into the flue gas for capturing acid gases; an injector for injecting activated carbon into the flue gas for capturing heavy metals, and wherein the filter is arranged to filter flue gas to segregate and remove particular matter from the flue gas.

13. The system according to any preceding claim, wherein the cooler is a liquid-to-gas heat exchanger, and wherein the liquid-to-gas heat exchanger forms part of a waste heat recovery system.

14. The system according to any preceding claim, comprising a turbine that has an inlet and an outlet, the inlet arranged downstream the afterburner arrangement, wherein the turbine is arranged to receive flue gas from the afterburner and recover thermal and / or kinetic energy from the flue gas, and drive an electric power generator.

15. The system according to any preceding claim, further comprising a particle separator, arranged downstream the pyrolysis reactor, arranged to receive pyrolysis gas from the pyrolysis reactor and separate particles, such as soot, from the pyrolysis gas.

16. The system according to any preceding claim, wherein the pyrolysis reactor comprises a steam outlet, or second outlet, arranged to allow steam, or water vapor, to be removed, or discharged, from the pyrolysis reactor.

17. A method using the system according to any one of claims 1-16, the method comprising the steps of:- gasifying the hazardous waste in the gasification reactor by heating the hazardous waste in an oxygen-deprived environment (601) to generate a gas,- mixing the gas with a source of oxygen to form a combustible gas mixture (602),- routing the gas mixture into the afterburner arrangement (603),- igniting the gas mixture using the ignitor to combust the gas mixture and form a flue gas (604),- flowing the flue gas through the heated flow conduit (605),- providing the flue gas to the flue gas treatment arrangement (605),- cooling the flue gas using at least one cooler (606),- filtering the flue gas using at least one filter (607).

18. The method according to claim 17, wherein during the step of flowing the combustion gas through the flow conduit, the combustion gas flowing through the flow conduit is controlled to have a temperature in the range of 700 to 1300 °C, such as 850 to 1300 °C, by heating the flow conduit.

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