EP0064089B1 - Device for the coal dust pressure-gasification - Google Patents

Abstract

1. Apparatus for coal dust gasification under pressure, in which the coal dust and/or a coal dust/liquid mixture is blown in a reactor and gasified, in the presence of steam and acid, to a gas containing CO2 and H2 , so that a clinker film is formed at least at the discharge end of the reactor, characterised by a reactor with, at the discharge end, a flow conducting device (5, 12) which is formed as a table.

Description

The invention relates to a device for coal dust pressure gasification in which the coal dust and / or a coal dust / liquid mixture is blown into a reactor and gasified in the presence of steam and oxygen to form a CO and H ₂ -containing gas, and at least at the discharge end of the reactor a slag film is generated.

Gasification in the slag bath is known. The coal dust with the gasification agent is blown obliquely from above onto a liquid slag melt. The solid particles, which are specifically lighter than the slag, are deposited on the surface of the bath and float on the surface until only the molten ash portion remains. The slag is drawn down over an overflow of the bath. The gas leaves the reactor upwards.

Such an approach has several advantages. The very long residence time of the solid ensures almost complete carbon conversion. Lower degrees of fineness of the carbon carrier are sufficient for this and an exactly constant dosage is not necessary. The reactor temperature should be set so that the flow behavior of the slag allows turbulent movement of the slag bath.

The disadvantage of the slag bath reactor is the difficulty in handling the liquid slag. Overall, an extremely complex construction is required. These disadvantages have hitherto stood in the way of implementing the method on an industrial scale.

In a “new generation” coal gasification process, gasification takes place in a cloud of airborne dust that is created by blowing the very fine-grained gasification agent into a recator. The reactor can be operated without special installations. The flow control is determined by the burner with which the gasification agent is blown in and the reactor geometry. Due to the relatively short residence time of a few seconds, a high reactor temperature is required to achieve high carbon conversions. A complete carbon turnover is sometimes not economical considering the total energy balance of the process.

The simple structure of the reactor ensures trouble-free operation, but in order to achieve constant operating conditions, an absolutely constant use of coal and gasification agent is required. In order to reduce the necessary dwell time of the solid particles, very fine grinding of the coal is also imperative.

The present invention has for its object to improve the carbon conversion in coal dust gasification while maintaining or increasing the economy. The invention is based on the fact that the residence time of the solid should be independent of the residence time of the gas, as is the case in the slag bath generator. At the same time, however, the simple operation of the entrained-flow gasifier should be retained as far as possible.

It is known from DE-C-885 766 and from FR-A-2 369 502 to direct the coal dust to the inside of the reactor as part of a coal dust pressure gasification and to produce a slag film there. However, this solution is still unsatisfactory because a large part of the coal dust particles does not touch the slag of the supporting reactor inner walls. The proposed solution according to DE-B-1 091 268 would remedy this disadvantage. But there would be other disadvantages. The causes would be the entry of the coal dust particles against the inner wall of the reactor and the gas flow caused in this way

According to the invention, a sufficient residence time is achieved without the disadvantages of DE-B-1 091 268 in that the usual routing of the coal dust / liquid / gas mixture is maintained and the reactor is provided at the discharge end with a flow control device which is table-shaped.

• Fig. 1 einen besonders für die Vergasung von Kohlenstaub in trockener oder suspendierter Form geeigneten Reaktor,
• Fig. 2 einen insbesondere zur Vergasung einer Kohle-Wasser-Suspension geeigneten Reaktor.

Two exemplary embodiments of the invention are shown in the drawings. Show it:

• 1 a reactor particularly suitable for the gasification of coal dust in dry or suspended form,
• Fig. 2 shows a reactor particularly suitable for gasifying a coal-water suspension.

A burner 1 turns a rotationally symmetrical reactor space 2 into a solid carbon carrier, e.g. Coal dust, supplied in dry or suspended form. The necessary gasification agent, e.g. Oxygen and water vapor into the reactor interior 2. The reactor interior is surrounded by a refractory lining 3, which, as shown in FIG. 1, is only cooled by the heat given off by a steel jacket 4, or has forced cooling, not shown, within the steel jacket 4 .

The oxygen portion of the gasification agent converts with the combustible portions of the gas atmosphere in the reactor interior 2 in a flame. The coal dust is brought to the reaction temperature by absorbing heat from the environment, the mean temperature of which is above the slag flow point, that is, depending on the type of coal, above approximately 1350 ° C. When the coal dust is introduced in the form e.g. a coal-water suspension, the suspension drops produced on the burner 1 by atomization are still dried before heating to the reaction temperature.

With increasing temperature of the carbon particles, carbon gasification begins, which requires the supply of heat from the environment, since these are exclusively endothermic reactions.

At the start of gasification, the temperature difference between the carbon particles and the surrounding gas atmosphere is large, so that the heat flow necessary for the gasification reactions is guaranteed. As the reaction progresses, however, the temperature difference becomes smaller because the surrounding gas atmosphere changes in accordance with the heat cooling consumption of the reaction. As a result, the carbon conversion rates per unit of time become lower and lower the further the reaction progresses, since the partial pressure reduction in the gasification agent also has the same effect.

A built-in flow guide device 5 has the effect that some of the coal dust particles settle directly on the surface of this flow guide device and the remaining coal dust particles are separated on the refractory lining 3 by sharp deflection of the gas flow.

A built-in flow guide device 5 has the effect that some of the coal dust particles settle directly on the surface of this flow guide device and the remaining coal dust particles are separated on the refractory lining 3 by sharp deflection of the gas flows.

The flow guide device 5 is designed here in the form of a round table. The table top consists of several spirally wound, pinned tubes 6, which are clad with a refractory mass. A cooling medium flows through the tubes 6, which enters at 7 and exits at 8. There are a total of four inlets 7 and outlets 8 uniformly distributed around the reactor circumference. From the cooling medium inlets 7, feed lines 9 lead to the pipes 6. From the pipes 6, discharge pipes 10 lead to the outlets 8. The four feed and discharge pipes 9, 10 in total also pinned and clad with a fire-resistant mass. They also serve as a supporting structure for the table top.

The already partially gasified carbon particles either deposited on the flow guide device 5 or on the lining 3 are now exposed to the reaction conditions until the carbon is practically completely converted to gasifying agent. Only then does the mineral substance of the feed material become flowable and run off as a slag film on the lining 3 or on the edge of the flow guide device 5.

The fact that the slag only flows at very low carbon contents of the order of one percent ensures that the residence time of the coal dust particles under reaction conditions is sufficient for the carbon to be converted practically completely.

The resulting slag film runs on the wall of the reactor neck 11 and arrives in a water bath (not shown), where the slag is granulated and discharged via a lock device.

The gas generated also leaves the reactor through the reactor neck 11 and is subsequently cleaned or fed to any use.

The slag film reactor according to the invention according to FIG. 2 is particularly suitable for the gasification of coal dust which is introduced into the reactor as a coal-water suspension. This prevents the drying and heating of the coal dust particles in the area of the highest temperature within the gasification reactor, namely in the area of gas combustion with the oxygen, while the gasification reaction takes place in the coldest part of the reactor. Rather, the gasification reaction in the high temperature region of the reactor is initiated with the advantage of a particularly intensive reaction, while the drying and heating of the carbon particles takes place at low but sufficient temperatures.

The reactor parts which are identical in FIG. 2 to FIG. 1 have the same designations. Through the burner 1, a pumpable coal-water suspension enters the reactor interior 2. At the outlet end of the burner 1, the pressure of the suspension is destroyed. This atomization is optionally carried out by additional atomizing medium, e.g. Steam, supported.

The suspension drops are first dried and preheated by heat transfer from the backflow of hot gas from the gasification zone before they reach the actual reaction zone at the highest temperature. The reaction zone is located in the lower reactor area, in which a flow control device 12 similar to the flow control device 5 is located. The flow guide device 12 is designed in the same way as the flow guide device 5 in the form of a round, centrally arranged table which is provided with tubes 6 and is held by the feed lines 9 and discharge lines 10.

A line 14 for oxygen or air is passed through one of the supply lines 9. The line 14 is connected to an air or oxygen supply line via a connecting piece 13 and leads to a nozzle 15 at the other end. The nozzle 15 projects centrally through the flow guide device 12 into the reactor interior 2. It is equipped with a cap 18 to prevent clogging by slag particles protected. The line 14 is cooled by the cooling medium flowing into the tubes 6.

The oxygen entering the reactor interior 2 through the nozzle 15 reacts in a flame with combustible gas formed in the reactor and with dried and preheated coal dust. This results in a particularly high and advantageous reaction temperature in the area of the flow guide device 12 in the lower reactor part. The remaining reaction sequences are the same as those described in the description of FIG. 1.

Claims (4)

1. Apparatus for coal dust gasification under pressure, in which the coal dust and/or a coal dust/ liquid mixture is blown in a reactor and gasified, in the presence of steam and acid, to a gas containing CO₂ and H₂, so that a clinker film is formed at least at the discharge end of the reactor, characterised by a reactor with, at the discharge end, a flow conducting device (5, 12) which is formed as a table.

2. Apparatus according to claim 1, characterised in that the table (5, 12) is provided with cooling tubes (6) and is held in the reactor with the tubes (6) and/or inlet ducts (9) and/or outlet ducts (10).

3. Apparatus according to claim 2, characterised in that a duct (14) for air or acid, opening in a nozzle (15), is positioned above the flow conducting device (5, 12) in a vertical reactor configuration, in a cooling agent duct (6, 9, 10) combined with the flow conducting device (5, 12).

4. Apparatus according to claim 3, characterised in that the nozzle (15) is protected by a cap (18).

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