FI87108B - Power station using fluidised-bed combustion - Google Patents

Description

87108

A power plant where combustion takes place in a fluidized bed

The new method applies to a power plant where the combustion of fuel takes place in a fluidized bed of particulate material in the combustion chamber of a grate vessel. The layer usually contains a material that acts as an ash absorbent, such as limestone or dolomite. Combustion can occur at a pressure of about atmospheric or higher, such as in a PFBC-1 plant. PFBC are the English expression for Pressurized Fluidized Bed Combustion aikuki rjai met.

Equally, a power plant refers to a plant solely for heating water, e.g. to a district heating network, solely for the production of '' steam or for the production of steam and gases for separate steam and gas turbines in an electric power plant.

The layer material particles are in constant motion. Particles that hit the bed pipes at high speeds have an eroding effect.

The pipe material wears out gradually and the pipes of the grate vessel must be replaced after a certain period of use. The replacement incurs partly direct costs for pipe replacement, partly indirect costs during the maintenance period.

In order to reduce the erosion of the pipes, the pipes for non-layer use are provided with a hard coating which is metallically bonded to the base material, for example by means of a metal powder or a drama 11a. The pipes are also provided with surfaces, flanges or longitudinal strips below them to reduce erosion. The task of the wedding is to break up the layer matrix flows. In this way, the layer particles are slowed down and energy is absorbed. A smaller amount of particles hits the tube directly and, in addition, the velocity of the hits particles decreases, thereby reducing their eroding effect.

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The new method takes into account erosion as an enery problem and the fact that the disintegration of the grate material 1 in the vicinity of the pipe by absorbing energy reduces the velocities of the particles and weakens the erosion effect of the particles hitting the pipe walls. An important goal of the new method is thus to absorb the energy of the arinama material stream in the vicinity of the pipes. Another important goal of the new method is to provide erosion protection that is easy to manufacture and install on pipes.

According to the new method, the pipes are surrounded by a helical strip in which the pitch of the spiral is greater than that of the strip. An opening is then formed between the turns, to which the grate material has free access and in which it comes into contact with the pipe. The trouser is preferably less than two ribbon widths, i.e. the gap between the turns is smaller than the width of my ribbon. The diameter of the strip spiral can be so much larger than the tube that a significant gap is left between the strip spiral and the tube. The strip spiral may be attached to or detached from the tube so that it can be moved slightly axially and rotated around the tube. The strip spiral can then move so that different parts of the tube are covered at different times, and by selecting a suitable combination of strip width and thickness and pitch and diameter in the strip spiral, the desired effects can be achieved. Coverage can be varied with tape slope and pitch options. The flow conditions around the pipe can be influenced by the choice of strip thickness and pitch.

Enery yield can be influenced by choices of weight as well as spiral and tube clearance.

The new method makes it possible to protect the pipes from erosion in a simple manner. When making the pipe package a, a spiral can be wound around the pipes. A particular advantage is that the i, 3 87108 pipe protection can be brought into the pipes in a finished pipe package. Worn anti-erosion coils can be replaced during equipment inspection. Either the finished spiral can be screwed onto the tube with suitable auxiliary tools or the steel strip can be formed into a spiral around the tube with a special tool.

The new method will be described in more detail with reference to the accompanying figures.

Figure 1 schematically illustrates the PFBC-1 apparatus to which the new method is applied, and Figure 2 shows the spiral protection of the pipe.

Figure 1 illustrates a pressure vessel. The grate vessel 2 and the cyclone-type gas purifier 3 are enclosed in a pressure vessel. Only one cyclone is described, but in reality there are several parallel groups of cyclones connected in series in the purification device. At the bottom of the grate vessel there is a base 4 constructed of longitudinal distribution chambers 5 with air nozzles 6 for blowing air into the bed 7 of the combustion chamber 8 above the base 4 and for burning the fuel introduced therein. Between the distribution chambers 5 there are gaps 10 through which the grate material and the ash can enter the space 11 under the base 4. aateri .i «1 i j ö. ! i.:> le U <_; !:,: >> i .. vK- poi ssyo! · t. via line 12 poi ssyottol ai tteel 1 a 13 away. The fuel and ash absorbent are fed to layer 8: via separate lines 14 and 15. The combustion chamber 8 has cooling pipes 16 to which cooling water is introduced via line 17 and which supply steam to the non-described steam turbine 11e via line 18. These tubes 16 cool the bed and keep it at a temperature suitable for efficient combustion. Depending on the load, the height of the layer 30 varies and the part of the pipe supporting the part or the free part of the pipes is free above the layer 7. The combustion gases accumulate in the free space 21 and flow along the line 22 to the gas purifier 3 and from there 4 87108 along the line 23 to the turbine 2h. The separated karst is carried away along line 2b. The turbine 24 is driven by a generator a 20 and a compressor 27. The compressed combustion air is introduced into the space 28 between the pressure vessel 1 and the grate vessel 2 via a line 24.

The tubes 10 are surrounded by a spiral 31 consisting of a strip having a width b, a thickness t and a pitch s. The trouser s is a stripe length bsuufp "> 'ni so that an opening G is formed between the turns. the service

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a larger that significant gap is formed between the tube 10 and the coil 31. The spiral can hang freely in the tube 16 and can then move axially between the two limit bearings and can rotate. The spiral can also be attached to one tdi at several points along the tube.

Claims (4)

5 87108 Patent Requirements A power plant in which fuel burns in a particulate fluidized bed in a grate vessel (2) and has pipes (16) in the grate vessel (2) for cooling the layer (7) and heating water or generating steam, the pipes (16) being provided with erosion protection characterized in that the erosion protection consists of a strip (31) wound helically around the tube (16). Power plant according to Claim 1, characterized in that there is a clearance (1) between the helical strip (31) and the pipe (16). Power plant according to Claim 1, characterized in that the pitch of the spiral (31) formed by the strip is so large that there is an opening (G) between the turns: Power plant according to Claim 1, characterized in that the spiral (31) formed by the strip is arranged: detached from the tube (16) so that it can rotate or move Y: axially with respect to the tube. 6 87108