Equipment for the combustion of fluids with high particle content

Abstract: Equipment for the combustion of a suspension of a combustible liquid and combustible solids in particle shape, for instance carbon particles. The equipment comprises a tank (1), a burner unit (6) and a pipe (3) which is connected to the burner unit (6) and which protrudes into the tank where it is connected to a pump system (9). The pump system (9) comprises an eddy current pump with a branched outlet (12) where one of the outlet branches (13) is connected to the pipe (3), while the other branch or branches (14) is formed as a nozzle or a jet with its outlet directed into the tank, thus serving to stir the suspension in the tank.

Description: The present invention relates to equipment for the combustion of a suspension of a combustible liquid that contains a large amount of combustible material as solids in particle shape, for instance carbon particles. The equipment comprises a tank, a burner unit and a pipe for fluid transport, said pipe being arranged between the burner and an injection- or a feed pump located inside the tank. In Norwegian patent No. 171127, that is owned by the applicant, it is described an equipment of the type as mentioned above, comprising a pump of the displacement type, i.e. a ordinary gear pump. When using this type of pump, it is experienced that it operate in a satisfactory manner when combusting viscous liquids as tar from filters with small amounts of particles. However, when pumping suspensions with a larger content of carbon particles, pumps of this type are rapidly worn out, and have to be replaced. Another problem related to this known technique is that particles contained in the liquid precipitate and settle at the bottom of the tank, that may cause clogging at the pump inlet. It is an object of the present invention to provide a technical solution where the above mentioned problems are eliminated or substantially avoided. Thus, the invention represents a solution where the problems related to particle precipitation are avoided, and further the problem with excessive pump wear is substantially reduced. EP-A-0 466 167 discloses an apparatus for pumping fibre suspensions of the pulp and paper industry. The pump comprises at least two outlets, at least one of the outlets being preferably provided with a means for regulating the flow through the outlet. The outlets may have different diameters, where the ducts connected with the outletsreceive pulp from the pump at different pressures. The pump is arranged outside a vessel, where one outlet duct may return pulp back to the vessel for keeping the bottom level in said vessel moving to prevent the solids of the pulp from accumulating at the bottom of the vessel. The pump of the present invention differs from the pump in this reference as the present pump is arranged inside the tank and has a vertical rotation axis. These features, among others, will contribute to proper stirring and even particle distribution in the fluid pumped to the burner. In carbon plants around the world, for instance plants that produce carbon bodies for the aluminium industry, there is a large excess of carbon dust. This is generally carbon dust with a particle size less than 100 µm. Carbon dust of this type is today deposited, and represents in this manner a loss for the companies that "produce" the dust. When using the combustion equipment according to the present invention, the carbon dust may be combusted when mixing it with for instance waste oil. Tests have shown that it is possible to mix up to 50% (weight) coke dust in the oil, and having a quantity of energy corresponding to 36000 kJ/kg (10kWh/kg), the use of carbon dust for combustion purposes represents a substantial saving in energy costs per year. Besides, the use of carbon dust for combustion purposes will, in addition, lead to a reduction in the amount of dust to be deposited and correspondingly a reduced demand for waste depositing areas, thus having good environmental effects. The invention will now be further described by means of examples and with reference to the drawings where: Fig. 1 shows a principal sketch of the equipment according to the invention, and Fig. 2 shows on an enlarged scale an eddy current pump as shown in Fig. 1 More precisely, Fig. 1 shows an insulated tank 1 that is adapted to contain a suspension of a combustible liquid mixed with carbon particles. At the interior of the tank there is arranged an eddy current pump 9 driven by a shaft 8 that is connected to a motor 2 placed at the top of the tank. The pump 9, that is further shown in Fig. 2, has a branched outlet where one of the branches 13 is connected with a burner 6 via a pipe 3, while an other branch, or possibly two or more branches 14, is formed as a jet or a nozzle that is open towards its surroundings inside the tank. In this manner the pump is partly arranged to supply the burner 6 with suspension from the tank and partly arranged to circulate the suspension in the tank via the nozzle or the nozzles 14 to maintain the suspension of liquid and particles in the tank. The liquid level in the tank is monitored by a level monitor 7, that is not further shown in the Fig. 1. Moreover, the tank is provided with one or more heating elements 10 to, if necessary, warm up the contents of the tank, if in case the tank contains a viscous, temperature dependent liquid. In addition, a suction pipe 5 is arranged in connection with the tank for evacuating possible vaporised components out of the tank. The eddy current pump 9 with fastening means and motor 2 is shown on an enlarged scale in Fig. 2. The pump comprises a pump housing 15 with an internal driven eddy current rotor 16, driven by a shaft 8. The rotor used in the pump may preferably be of the brand EGGER. The pump housing and thereby the pump is connected to an axle housing 17 with a flange connection 19. The purpose of the axle housing, besides serving as an connection for the pump, is to provide a sealing of the shaft 8 and its bearings 20, 21, and in addition the pump bearing 22, against the surrounding liquid (suspension) in the tank. The bearings 21,22 is pressure lubricated by means of pressurised oil pipes 23 supplying oil from an oil reservoir or a pump 24 driven by a transmission belt 26 connected to the shaft 8. The axle housing 17 is at its top end attached to a removable hatch or cover 25 providing easy removal of the pump including its axle housing and driving motor, when performing maintenance or replacement operations. In the illustrated embodiment, the axle is driven by the motor via direct connecting means 27. Thus, it should be understood that other connecting means, such as transmission belts or gears, may alternatively be used within the scope of the invention.

Claims: Equipment for the combustion of a suspension of a combustible liquid and combustible solids in particle shape, for instance carbon particles, comprising a tank (1), a burner unit (6) and a pipe (3) for transporting the suspension, said pipe having one end connected to the burner unit (6), and having its other end protruding into the tank where it is connected to a pump (9) arranged inside the tank, characterized in that the pump (9) is an eddy current pump with its axis of rotation arranged vertically and further being provided with a branched outlet (12), where one of the outlet branches (13) is connected to the pipe (3), while the other branch or branches (14) is formed as a nozzle or a jet with its outlet directed into the tank, thus serving to stir the suspension in the tank.

Inventors: HOLDEN INGE, RUUD ANDERS, WERGE-OLSEN ARNE, HOLDEN, INGE, RUUD, ANDERS, WERGE-OLSEN, ARNE
Applicants: NORSK HYDRO AS, NORSK HYDRO ASA
Application year: 1995
Main classification: F23K5
IPC codes: F23K5, F23G7