This invention relates to an apparatus for ^' converting solid pulverous fuel to combustible gaseous state, comprising a cyclone and a gasification device conn¬ ected thereto with a tangentially directed inlet.

In DE-0 2 623 770 an apparatus of the aforesaid kind is disclosed which, thus, comprises a gasification device and a cyclone. In the gasification device easily combustible particles are gasified, and in the cyclone the renaini g gasification is carried out and solid incombustible particles are separated. The combustible gas is discharged upwardly from the cyclone. The gasification device operates with high speeds by means of a venturi tube. The gasification device also comprises a catalyst, which decomposes hydroperoxide to oxygen gas and water vapour. The oxygen gas is used as oxidizing agent. For assisting in the formation of the oxygen gas, according to the known state of art also heated air can be supplied.

The present invention eliminates the requirement of a special catalyst and utilizes the moisture cont¬ ent, which normally is found in the fuels and/or is supplied in pulverized coal, whereby the invention in general presupposes an increase in the moisture content of the fuel. According to the invention, the moisture amount is to be controlled and adjusted so as to obtain optimum combustion prerequisites.

The invention is characterized in that the gasific¬ ation device comprises a cylindric chamber with small diameter relative to the diameter of the cyclone, to which at one end an inlet member with tangential inflow direction is attached which is in common for fuel and primary air of a certain drive pressure, that means are provided for adding moisture to the fuel at least prior to its feed into the chamber,

through which fuel and air flow helically into the cyclone with flame formation, that a suppply member for secondary air to the cyclone is located at the inlet, and the supply of the primary air and second¬ ary air is controlled so that the total amount of primary air and secondary air is smaller than the stoichiometrically corresponding one for a complete combustion of the respective supplied fuel amount.

The invention is based on the prerequisite known per se, that water vapour is required for the water gas reaction. At the invention, the water vapour is formed by a relatively high water content in the fuel or is added as steam with supply of hot air. The water vapour increases the reaction speeds so that the apparatus proper is a compact one. The water vapour, besides, increases the capacity of controlling the process.

In the gasification device the reactions proceed substantially as follows:

C+H O = CO+H endother ic reaction C+O = CO _p exothermic reaction

In the cyclone the reactions are substantially as follows:

1 C+- O _p = CO exothermic reaction

C+CO _p = 2C0 endothermic reaction

A preferred embodiment of the invention is described in the following, with reference to the accompanying drawing, in which Fig. 1 is a schematic lateral view ^* of an apparatus according to the invention idea, Fig. 2 is a cross-section along the line II-II in Fig. 1, and Fig. 3 is a perspective view on an enlarged scale of the gasification device connected to the cyclone.

In Fig. 1 the apparatus, which is shown from the side, comprises a cyclone 1 with an upwardly located outlet 2, from which the gas in ready state is discharged. In the upper portion of the cyclone gasification devices 3 are located which at the embodiment shown are four in number and connected by tangential inlets to the cyclone (see Fig. 2). To the gasification device 3 a powder- moisture mixture and preferably heated primary air are supplied through a conduit 4. The fuel is stored in a magazine 5 above the cyclone. The primary air is pre- -heated and has a pressure of 500-900 Pa, and the powder-moisture mixture is caused to flow with the prim¬ ary air through the conduit 4 to the gasification dev¬ ice 3. The storage and feed of the fuel in the form of, for example, coal particles, thus, are effected in a manner known per se, in that the coal is fluidized in the primary air. As appears from Fig. 2, four gasification devices 3 are arranged by a tangential inlet to be connected to the cyclone 1. All four gasification devices are supplied with fuel and air from the m-gazine 5 common to all of them.

Fig. 3 shows by way of a perspective view and on an enlarged scale the gasification device 3. It comprises a cylindric chamber 3, the end of which in tangential direction is connected to the cyclone 1, and at the other end of which the duct 4 is connected tangentially to the cylindric chamber 3. This implies, that the mixt¬ ure of primary air and coal powder flowing through the duct 4 into the chamber is passed in a helical path through the chamber 3 where it is ignited and forms flames. It is the more volatile parts of the fuel, which hereby are ignited and burn. The flames and the remaind¬ er of the fuel pass out through the opening 6 and into the cyclone 1. A conduit 7 extends centrally through the

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chamber 3, through which conduit secondary air is supplied, which is fed into the cyclone 1 at the open¬ ing 6 of the chamber. The primary and secondary air have a pressure, which overcomes the total pressure drop in the entire gasification arrangement and at the inlet to the subsequent combustion chamber or collect¬ ing supply. A sufficient pressure also can be ensured by a booster device for the gas after the cyclone.

A pipe 8 joining the duct 4 prior to its opening into the chamber 3 is mounted for adjusting the moisture content. Through said pipe 8 water or water vapour can be supplied in a controlled manner.

The gas bulk from the gasification device 3 flows into the cyclone 1 and describes a downward helical movement along the shell surface of the cyclone downward to the cone-shaped portion 9.Here the gas turns and flows cent¬ rally upward where is flows out through the conduit 2, which leads to a burner (not shown) located in a boiler. Combustion air is supplied to the burner, here¬ by the gas bulk combusts with white flame in the fire place of the boiler, where the heat content at the combustion of the gas is recovered.

Solid incombustible particles are collected downwardly at the bottom of the cone 9 ₃ and a bottom valve 11 acting as a sluice and known per se is provided for removing the solid particles.

It is essential for the function of the apparatus, that the temperature in the cyclone is not so high as to reach the fusion temperature for the ash therein. The temperature, therefore, is controlled and adjusted by a temperature scanner 12, which emits a signal before the fusion temperature is obtained. The signal is sent to an adjusting device 13,14, which decreases the amount of supplied primary and/or secondary air and fuel so that the effect from the combustion process, and thereby

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the temperature, is reduced. The temperature scanner 12 also sends a signal at a lower temperature limit, so that the temperature in the cyclone is maintained within a lower and a higher value. There is alternat¬ ively, or in addition, the possibility of affecting the temperature by supplying a greater or smaller amount of inert gas (waste gases from the combustion space) .

The primary air, as mentioned, is pre-heated to about 700°C. At cold starting the heating must be effected by some external heating process, but in operation the air-can be heated by passing about the cyclone 1 prior to the feed of the air into the chamber 3. This can, for example, proceed in such a manner that the cyclone has a jacket about the cyclone shell proper, so that an annular passageway is formed about the cyclone. At cold starting the entire apparatus is heated in that the air addition is adjusted so that the gases substantially entirely are combusted, i.e. carbon dioxide leaves the cyclone. As soon as operat¬ ion temperature prevails, the production of combust¬ ible gas (CO) can commence. In this connection ad¬ justment to the desired load is required, and the supply of primary and secondary air must be throttl¬ ed so that the supply of air is smaller than the one corresponding stoichiometrically to the fuel amount supplied. When, thus, the load is low (the fuel amount supplied is small), the gas amount in the apparatus can be too small forbeing capable to maintain the speed through the apparatus. In that case inert gas is to be supplied, and preferably the waste gases from the boiler can be used which are recycled to the primary air and/or secondary air inlet.

The correct water content in the fuel at the combust¬ ion is controlled by studying the flame spectre in a subsequent combustion space by means of a spectrometer 15,Iβ. When the spectre is not as desired, the amount of liquid through the conduit 8 is increased or decreas¬ ed. The control can be carried out by observing manu¬ ally or through instrument lines arising in one area of the spectre and to compare them to a spectral patt¬ ern 16 during the adjustment of the air amount supplied- When there is agreement with the pattern, the fuel has correct moisture content at the combustion. The spectrom¬ eter can be placed in a position other than the one shown and may, for example, be directed to the flame out of the gasification device.

It is to be noted, that the diameter of the gasificat¬ ion device, i.e. the diameter of the chamber 3 ₃ is small compared to the cyclone diameter. When four gasif¬ ication devices 4 are provided, as shown at the ill¬ ustrated embodiment, four gas paths are formed which sweep downward in a helical flow through the cyclone. It is to be observed that the air and the gas flows are helical both in the gasification device 3 and in the cyclone 1. This yields time and contact situation required for the chemical reactions to be complete and for ash formed to be separated out of the gas flow. Furthermore, the gasification in the gasification device 3 and in the cyclone 1 must take place at air deficit. The supply of primary air and secondary air is to be adjusted so that substantially combustible gas in the form of carbon monoxide is discharged from the cyclone. The total amount of primary air and second¬ ary air, thus, is smaller than the one corresponding to the stoiciometric amount for complete combustion and is preferably 25-50?..

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The gas produced, as mentioned above, is discharged from the upper portion of the cyclone through the outlet. 2. The gas is combusted with a white flame in that tertiary air is supplied in the burner (not shown) . The apparatus utilizes the heat content of the fuel substantially completely, in that heat loss¬ es from the apparatus are maintained at a minimum, and the heat losses also are recovered by heating the primary air, as mentioned, by causing it to flow about the cyclone before the primary air is supplied to the gasification device.