GB2164391A - A gas turbine with a particle separator for the working gas - Google Patents

Abstract

To prevent their entry into the turbine's rotor, particles such as ash are separated from the working gas using the turbine's lead spiral (4) in which the particles experience centrifugal acceleration and so concentrate on the periphery of the lead spiral for discharge through one or more outlets (5, 6, 7). <IMAGE>

Description

SPECIFICATION Gas cleaning method and device for use with turbines The present invention relates to a method for cleaning gas led into a turbine. The invention also relates to lead spirals of axial and radial turbines used in carrying out the method. The turbine lead spiral is used as a particle separator.

Erosion causing ash particles are nowadays a primary hindrance for the use of solid fuels in gas turbines. Thus one of the most central challenges in the combustion technique is the separation of small solid particles. Running of gas turbines e.g. on coal has been studied in many pilot plants, some of them even with a 80 MW fuel capacity. In these researches gas has been cleaned in usual cyclones, connected parallelly and in series. Another research line in the separation of particles from hot gases is the development of ceramic fiber filters.

Experiences from pilot plants provided with cyclon separators show that a sufficient cleaning capacity is not achieved with cyclones within a reasonable loss of pressure. In turbines provided with lead spirals a pronounced particle concentration in the spirals can be detected. This manifests itself in rapid spiral erosion. According to calculations it is also evident that the particles concentrate in the spirals because a typical tangential speed is 300 m/s and the radius in a small turbine is e.g.

0,0150 m, which gives.a centrifugal acceleration of 3002/0,15 m/s2, in other words 60000 times the acceie'ration of earth gravitation.

In usual cyclones a centrifugal acceleration of 6.105m/s2 would cause an unreasonably great, permanent loss of pressure, but in connection with a turbine the periphery speed after the spiral is made use of as a mechanical power.

The object of the present invention is to make an economic use of the great centrifugal acceleration accomplished in the lead spiral in order to separate particles from gas before the rotor wheel of the turbine. The method enables a substantial increase in the particle content allowed in gases used as a turbine energy source.

The method according to the present invention is characterized in that particles concentrated on the periphery of the lead spiral of a turbine will be discharged through one or a plurality of outlets. A radial or an axial turbine according to the invention is characterized in that one or a plurality of outlet ducts are disposed on the periphery of the turbine lead spriral, preferably on the radially outer periphery. The concentrated particles on the outer periphery of the spiral can be discharged in a controlled manner through the outlet ducts.

One of the most important advantages of the invention is the great attainable separation ability which enables the use of flue gases from a combustion plant provided with an ordinary precleaning. Furthermore there are hardly any investment or operating costs for the separation device.

The invention will be described in detail in the following with reference to the accompanying drawing.

The drawing shows the method according to the invention applied to a lead spiral of a radial turbine. Gas containing particles enters a lead spiral 4 though a device 1. The cleaned gas is led from the lead spiral to an axial exhaust 3 through a rotor wheel 2. Due to a great centrifugal acceleration particles concentrate on the outer periphery of the spiral 4 to which outlet ducts 5, 6, 7 with valves are tangentially connected.

The flow through the outlets can be adjusted from OFF to ON, so that according to the example in the drawing with three outlets the discharge can be optimized (the necessary discharge flow minimized).

The lead spiral can be used as a tangential flow cyclone also in an axial turbine where usually no spiral is used with clean gases. The invention can be put practiced in many different ways as regards to direction, form, location and number of the outlets within the scope of the ciaims.

1. A method for cleaning gas to be led into a turbine, in which the particles concentrated on the periphery of a turbine lead spiral are discharged through one or a plurality of outlets.

2. A radial or axial turbine, in which one or more outlet ducts are disposed on the periphery of the turbine lead spiral, preferably on its radially outer periphery.

3. A turbine as claimed in claim 2, in which the or each outlet duct is tangentially disposed on the periphery of the lead spiral.

4. A method for cleaning gas to be led into a turbine substantially as herein described.

5. A radial or axial turbine constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Gas cleaning method and device for use with turbines The present invention relates to a method for cleaning gas led into a turbine. The invention also relates to lead spirals of axial and radial turbines used in carrying out the method. The turbine lead spiral is used as a particle separator. Erosion causing ash particles are nowadays a primary hindrance for the use of solid fuels in gas turbines. Thus one of the most central challenges in the combustion technique is the separation of small solid particles. Running of gas turbines e.g. on coal has been studied in many pilot plants, some of them even with a 80 MW fuel capacity. In these researches gas has been cleaned in usual cyclones, connected parallelly and in series. Another research line in the separation of particles from hot gases is the development of ceramic fiber filters. Experiences from pilot plants provided with cyclon separators show that a sufficient cleaning capacity is not achieved with cyclones within a reasonable loss of pressure. In turbines provided with lead spirals a pronounced particle concentration in the spirals can be detected. This manifests itself in rapid spiral erosion. According to calculations it is also evident that the particles concentrate in the spirals because a typical tangential speed is 300 m/s and the radius in a small turbine is e.g. 0,0150 m, which gives.a centrifugal acceleration of 3002/0,15 m/s2, in other words 60000 times the acceie'ration of earth gravitation. In usual cyclones a centrifugal acceleration of 6.105m/s2 would cause an unreasonably great, permanent loss of pressure, but in connection with a turbine the periphery speed after the spiral is made use of as a mechanical power. The object of the present invention is to make an economic use of the great centrifugal acceleration accomplished in the lead spiral in order to separate particles from gas before the rotor wheel of the turbine. The method enables a substantial increase in the particle content allowed in gases used as a turbine energy source. The method according to the present invention is characterized in that particles concentrated on the periphery of the lead spiral of a turbine will be discharged through one or a plurality of outlets. A radial or an axial turbine according to the invention is characterized in that one or a plurality of outlet ducts are disposed on the periphery of the turbine lead spriral, preferably on the radially outer periphery. The concentrated particles on the outer periphery of the spiral can be discharged in a controlled manner through the outlet ducts. One of the most important advantages of the invention is the great attainable separation ability which enables the use of flue gases from a combustion plant provided with an ordinary precleaning. Furthermore there are hardly any investment or operating costs for the separation device. The invention will be described in detail in the following with reference to the accompanying drawing. The drawing shows the method according to the invention applied to a lead spiral of a radial turbine. Gas containing particles enters a lead spiral 4 though a device 1. The cleaned gas is led from the lead spiral to an axial exhaust 3 through a rotor wheel 2. Due to a great centrifugal acceleration particles concentrate on the outer periphery of the spiral 4 to which outlet ducts 5, 6, 7 with valves are tangentially connected. The flow through the outlets can be adjusted from OFF to ON, so that according to the example in the drawing with three outlets the discharge can be optimized (the necessary discharge flow minimized). The lead spiral can be used as a tangential flow cyclone also in an axial turbine where usually no spiral is used with clean gases. The invention can be put practiced in many different ways as regards to direction, form, location and number of the outlets within the scope of the ciaims. CLAIMS

1. A method for cleaning gas to be led into a turbine, in which the particles concentrated on the periphery of a turbine lead spiral are discharged through one or a plurality of outlets.

2. A radial or axial turbine, in which one or more outlet ducts are disposed on the periphery of the turbine lead spiral, preferably on its radially outer periphery.

3. A turbine as claimed in claim 2, in which the or each outlet duct is tangentially disposed on the periphery of the lead spiral.

4. A method for cleaning gas to be led into a turbine substantially as herein described.

5. A radial or axial turbine constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.