DE102013110447B4 - Gasification plant and method for stringing its ash sluice - Google Patents

Abstract

A gasification plant for producing a carbon monoxide and hydrogen-containing synthesis gas by gasification of solid, carbonaceous feedstocks, for example coal or coke, comprising a process gas consisting essentially of water vapor as gasification vapor and oxygen to form a solid or partially solid, non-flowable ash, comprising a fixed bed pressure gasification reactor, which is connected directly to a pressure lock for discharging the ash, wherein the pressure lock can be steamed and wherein the plant comprises a steam generating plant for supplying the reactor with gasification steam and for supplying the pressure lock with steam covering, characterized in that the steam generating plant is designed that it can deliver water vapor having at least two different pressures, temperatures and degrees of superheat each for use as gasification vapor or string vapor.

Description

Field of the invention

The invention relates to a gasification plant for producing a synthesis gas comprising carbon monoxide and hydrogen by gasification of solid, carbonaceous feedstocks, for example of coal or coke, with a gasification gas consisting essentially of water vapor and oxygen to form a solid or partially solid, non-flowable ash, comprising one Fixed-bed pressure gasification reactor, which is connected directly to a pressure lock for discharging the ash, wherein the pressure lock is covered with water vapor and wherein the gasification plant comprises a steam generating plant for supplying steam as gasification steam for the production of the process gas and as a covering steam for covering the pressure lock.

State of the art

Systems for fixed bed coal gasification have already been described in detail in the prior art. The core is in many cases formed by one or more Lurgi fixed bed pressure gasification reactors, as described in Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, Vol. 15, p. 369, 24 , as well as the DE-Offenlegungsschrift DE 10 2007 048 673 A1 are described.

In such a reactor, carbonaceous fuel, such as. As coal or coke gasified in a fixed bed at elevated pressure and elevated temperature with the addition of oxygen and water vapor to a carbon monoxide and hydrogen-containing product gas. The temperature of the vapor supplied as a gasification agent is typically 400 ° C. The working pressure of the carburettor is typically up to 40 bar. The raw synthesis gas leaves the carburetor in its upper region with a temperature of typically 400 to 600 ° C. During the gasification, a solid or largely solid, non-flowable ash is produced as a by-product, which is discharged from the gasification reactor via a rotary grate and via a pressure lock, since the reactor is under an increased operating pressure of, for example, 40 bar. In the following, this is the discharge of the ash serving pressure lock referred to as ash sluice. The emptying of the ash sluice takes place after its relaxation to ambient pressure.

To refill the ash sluice, it must first be returned to the operating pressure of the fixed bed pressure gasification reactor. In this case, a partial flow of the steam is used for re-covering the ash sluice, which is fed as gasification steam for the gasification process in the gasification reactor.

The patent DD 1 56 536 describes a method for commissioning fixed bed pressure gasification reactors. In this start-up procedure, the double jacket of the reactor vessel filled with a water / steam mixture is first heated by introducing high-pressure steam into the double jacket. By this measure, the formation of condensation on the inside of the reactor vessel should be prevented when subsequently the introduced into the reactor fuel bed is heated with high-pressure steam. The supply of high-pressure steam into the reactor vessel takes place partly via the gasification medium line and partly via the ash sluice. In the process, the high-pressure steam, as in the production operation of the stringing steam, is conducted into the ash sluice and passes through the open closure between reactor and sluice into the reactor and to the fuel charge. The covering of the emptied ash sluice takes place with high-pressure steam.

The patent DD 2 79 260 A1 describes a device for the deashing of fixed-bed pressure gasification reactors. The invention addresses the problem that, in particular the lower cone closure of the ash sluice, must be pressed into the overlying ash dump for opening, which leads to increased wear and frequently occurring mechanical disturbances. To solve the problem, the closure is preceded by a conical closure working in the reverse direction, with the tip of the closure cone facing upwards, which is opened by lowering the closure cone. The document shows that the ash sluice is covered with high-pressure steam.

The patent DD 299 379 A7 describes a method for increasing the availability of fixed bed pressure carburetors. The method is intended to prevent corrosion caused by the oxygen content of the gasification agent below the rotary grate, by ensuring the tightness of the ash sluice locks and thus preventing a flow of the gasification agent in the reactor area below the rotary grate and through the ash sluice into the environment. By measuring the temperature below the lower closure of the ash sluice, the tightness of the closure is monitored. After an operation-related emptying of the ash sluice and the closing of the upper and lower sluice closure, the sluice is covered with high-pressure steam to reactor pressure.

The patent DD 147 250 describes a method and an apparatus for safely removing gasification residues, in particular from fixed bed pressure gasifiers. The invention aims to prevent oxygen-containing gasification agent from entering the ash sluice due to leaks in the ash sluice closures, where it leads to an explosive atmosphere. To solve the problem, it is proposed to connect two ash sluices in succession and to check the tightness of the ash sluice closures by measuring the inflow of string gas to the respective sluice. For stringing and rinsing the ash sluices, inert gas is used here.

According to the prior art described above, no distinction is made between the high-pressure steam used as a gasifying agent and that for covering the ash sluice. Therefore, the quality of this vapor in terms of pressure and temperature must be compromised between the needs of the gasification process and the operation of the ash sluice.

In order to operate the gasification process with high product gas yield, the highest possible temperature for this vapor is sought. The higher the steam temperature of the gasification steam, the lower the coal consumption for achieving the process temperature required for the gasification reaction.

For the ash sluice, however, a high steam temperature is unfavorable, since it makes the production of the lock technically complicated and thus more expensive than it is for the actual task of the lock, d. H. the intake and discharge of the ashes would be necessary. It must then be used high temperature resistant, expensive materials.

It was therefore an object to provide a system and a method for covering the ash sluice a fixed-bed pressure gasification reactor available, on the one hand allows the design of the ash sluice using inexpensive materials. On the other hand, an energy-efficient operation of the upstream gasification reactor is to be ensured.

Description of the invention

According to the invention, this object is achieved according to claim 1 by a plant for producing a synthesis gas consisting mainly of carbon monoxide and hydrogen by gasification of solid, carbonaceous feedstocks, for example coal or coke, with a substantially consisting of water vapor as gasification vapor and oxygen process gas to form a solid or partially solid, non-flowable ash comprising a fixed bed pressure gasification reactor connected directly to a pressure lock for discharging the ash, the pressure lock being susceptible to steam, and the plant comprising a steam generator for supplying the reactor with gasification steam and for supplying the pressure lock with string steam characterized in that the steam generating plant is designed to produce water vapor having at least two different pressures, temperatures and degrees of overheating, each for use as Ver supply steam or string steam.

By separating the steam supply for the gasification process and for the covering of the ash sluice for the gasification process can be a cheaper, d. H. higher steam temperature can be selected. So z. B. by increasing the steam temperature from 400 to 470 ° C, the oxygen demand for the gasification of bituminous coal by 5%. At the same time, coal consumption decreases to achieve the process temperature required for the gasification reaction.

Further preferred embodiments of the invention

In a particularly suitable embodiment of the invention, the steam generating plant comprises two steam generators which can be operated independently of one another, one of the generation of the gasification steam for the gasification reaction and the other of the generation of the steam covering the covering of the ash sluice. This refinement has the advantage that steam generators optimized for the respective task can be used, and that these can be operated independently of one another. Thus, the steam generator for generating the covering steam for the ash sluice due to the required here, smaller steam flow rates are designed to be considerably smaller than the generation of the process steam serving steam generator. Furthermore, the steam generator can be taken out of service for the production of the string steam for the ash sluice for a large part of the service life of the gasification plant, since it is needed only during the covering of the ash sluice.

Since in many cases air and / or oxygen are fed into the gasification steam line as additional oxidation and gasification means, in a further embodiment of the invention the steam generator for the gasification steam is equipped with a steam heater for overheating the steam. In this way, condensation of the vapor on the line to the gasification reactor can be avoided. Furthermore, an additional possibility is thus obtained of adjusting the temperature of the gasification steam to a value which is particularly favorable for carrying out the gasification reaction.

In a cost-effective and structurally particularly simple embodiment of the invention, the steam generating plant is equipped with only one steam generator, from which a steam line goes, which branches into a gasification vapor and a Bespannungsdampfleitung and wherein there is a steam cooler in the course of Bespannungsdampfleitung. Since the investment and operating costs for a steam generator tend to be higher than for a steam cooler, significant savings can be achieved in this way.

In a particularly advantageous embodiment, this steam cooler comprises a water supply and a room, for. As a spray chamber or quench, are brought into contact with each other in or in the water and steam, for example by spraying and the steam is thus cooled to a suitable temperature for use as a clothing steam.

• (a) Ausleiten der Asche aus dem Festbettdruckvergasungsreaktor in die Ascheschleuse mittels eines Drehrostes bei geöffneter Ascheeintrittsöffnung und geschlossener Ascheaustrittsöffnung,
• (b) Schließen der Ascheeintrittsöffnung, Entspannung der Ascheschleuse auf Umgebungsdruck,
• (c) Öffnen der Ascheaustrittsöffnung, Entleeren der Asche aus der Ascheschleuse,
• (d) Schließen der Ascheaustrittsöffnung, Bespannen der Ascheschleuse mit Bespannungsdampf,
• (e) Öffnen der Ascheeintrittsöffnung,

wobei das Verfahren dadurch gekennzeichnet ist, dass die Temperatur des Bespannungsdampfes kleiner ist als die Temperatur des Vergasungsdampfes.In a further aspect, the invention relates to a method for operating an ash sluice in a gasification plant for gasification of solid carbonaceous feedstocks with a substantially consisting of water vapor as gasification steam and oxygen process gas to form a solid or partially solid, non-flowable ash, the gasification plant a Fixed bed pressure gasification reactor and an ash sluice, comprising the following process steps:

• (a) discharging the ash from the fixed-bed pressure gasification reactor into the ash sluice by means of a rotary grate with the ash inlet opening open and the ash outlet outlet closed,
• (b) closing the ash inlet opening, relieving the ash sluice to ambient pressure,
• (c) opening the ash outlet, emptying the ash from the ash sluice,
• (d) closing the ash outlet opening, covering the ash sluice with string steam,
• (e) opening the ash inlet,

the method being characterized in that the temperature of the string vapor is less than the temperature of the gasification vapor.

The process according to the invention is preferably carried out such that the temperature of the coating steam is at least 50 ° C., preferably at least 70 ° C., lower than the temperature of the gasification steam.

The implementation of the method is particularly advantageous when the temperature of the string vapor is at most 400 ° C and the temperature of the gasification vapor is greater than 400 ° C. This allows a low-cost selection of materials for the ash sluice with high gasification capacity and energy-efficient operation of fixed-bed pressure gasification reactor. So z. B. by increasing the steam temperature from 400 to 470 ° C, the oxygen demand for the gasification of bituminous coal by 5%. At the same time, coal consumption decreases to achieve the process temperature required for the gasification reaction.

Execution and numerical examples

Further developments, advantages and applications of the invention will become apparent from the following description of non-limiting examples of execution and numerals. All of the described features alone or in any combination form the invention, regardless of their combination in the claims or their back-reference.

Reference to the drawing, the invention will be explained below. Show it

1 a sketch of the gasification plant according to the invention,

2 a steam generating plant with two steam generators,

3 a steam generating plant with a steam generator and a steam cooler.

Unless otherwise stated, all stated pressures are to be understood as absolute pressures.

1 shows the gasification plant according to the invention, comprising the fixed-bed pressure gasification reactor 1 , the ash sluice 2 and the steam generating plant 3 , The fixed bed pressure gasification reactor 1 is over the ash inlet 4 with the ash sluice 2 connected. The top of the reactor 1 added solid, carbonaceous feedstock 5 , for example, coal or coke, is in a above the rotary grate 6 forming fixed bed 7 to product gas 8th gassed. Below the rotary grate 6 becomes the water vapor-oxygen mixture needed for the gasification 9 in the fixed-bed pressure gasification reactor 1 fed. The ash 10 leaves the fixed bed pressure gasification reactor 1 through the opened ash inlet 4 the ash sluice 2 , wherein the ash outlet opening 11 closed is. The pressure in the ash sluice corresponds to the working pressure of the fixed bed pressure gasification reactor, for example 40 bar.

After the ash sluice 2 has been filled to a predefined maximum level, it must be emptied. For this purpose, first the ash inlet opening 4 closed and the ash sluice 2 about one in 1 Relaxation line not shown relaxed to ambient pressure. Since the expansion gases still contain significant amounts of synthesis gas components such as carbon monoxide, they are a corresponding exhaust disposal, z. As a flare system, or an exhaust gas treatment supplied. If appropriate, an inerting step is followed by flushing with inert gas, for example nitrogen, to form last synthesis gas constituents from the ash sluice 2 to remove.

After relaxation, the ash sluice 2 over the opened ash outlet opening 11 emptied into a collecting vessel provided underneath. After emptying, the ash outlet opening becomes for the first stringing step 11 the ash sluice 2 at still closed ash inlet opening 4 closed and the ash sluice 2 with the in the steam generating plant 3 generated clothing steam 12 covered to a pressure which is less than or equal to the working pressure of the fixed-bed pressure gasification reactor. Finally, the ash inlet opening 4 at still closed ash outlet opening 11 opened, resulting in the ash sluice 2 again sets the working pressure of the fixed bed pressure gasification reactor. The ash sluice 2 can now be refilled with ash.

The steam generating plant 3 generates the gasification vapor 13 and the string steam 12 , Into the gasification vapor line 13 becomes air and / or oxygen 14 fed. The steam generating plant 3 becomes boiler feed water 15 and fuel (eg coal, oil or natural gas) and oxidising agent (usually air), 16 , fed.

2 shows a steam generating plant 3 with two independently operable steam generators 3a and 3b , The steam generators are each supplied with boiler feed water 15a , b and fuel / oxidizer 16a , b supplied. The steam generator 3a produces gasification steam 13 which is overheated in many cases. Its temperature is usually at least 470 ° C. The steam generator 3b produces string steam 12 which has a maximum temperature of 400 ° C.

3 shows a steam generating plant 3 with a steam generator 3a , The steam generator is supplied with boiler feed water 15 and fuel / oxidizer 16 provided. From the line 13 for the generated gasification steam is a stream 13a branched off and through the steam cooler 17 led, in which he to string steam 12 is cooled. To operate the steam cooler 17 is from the water pipe 15 a stream 15c branched off and to the steam cooler 17 guided. The steam cooler is designed as a spray chamber into which the over water pipe 15 supplied boiler feed water sprayed and thus a reduction of the steam temperature is achieved.

The following table summarizes operating parameters for a gasification plant operating at two different gasification steam temperatures. Gasification steam temperature 400 ° C Gasification steam temperature 470 ° C Relative O ₂ consumption 100% 95% Cold gas efficiency 88.8% 89.8% Proportion of stratified steam to generated steam <1% <1%

It can be clearly seen that a gasification steam temperature increased from 400 ° C. to 470 ° C. leads to lower oxygen consumption and to an increased cold gas efficiency of the gasification plant.

Industrial Applicability

By the invention, a lower design temperature can be set for the construction of the ash sluice, resulting in a cost advantage for the construction of the ash sluice.

LIST OF REFERENCE NUMBERS

1

Fixed bed pressure gasification reactor

2

ash sluice

3

Steam generating plant

3a, b

steam generator

4

Ash inlet opening

5

Feedstock for gasification

6

rust

7

fixed bed

8th

product gas

9

Steam oxygen mixture

10

ash

11

Ash outlet opening

12

upholstery steam

13

gasification steam

13a

Partial stream gasification steam

14

Air and / or oxygen

15

Boiler feed water

15a, b, c

Boiler feed water

16

Fuel and oxidizer for steam generators

16a, b

Fuel and oxidizer for steam generators

17

desuperheaters

Claims (8)

A gasification plant for producing a carbon monoxide and hydrogen-containing synthesis gas by gasification of solid, carbonaceous feedstocks, for example coal or coke, comprising a process gas consisting essentially of water vapor as gasification vapor and oxygen to form a solid or partially solid, non-flowable ash comprising a fixed bed pressure gasification reactor, which is connected directly to a pressure lock for discharging the ash, wherein the pressure lock is spanzbarbar with steam and wherein the plant comprises a steam generating plant for supplying the reactor with gasification steam and for supplying the pressure lock with string steam, characterized in that the steam generating plant is designed that it can deliver water vapor having at least two different pressures, temperatures and degrees of superheat each for use as gasification vapor or string vapor. Gasification plant according to claim 1, characterized in that the steam generating plant comprises two independently operable steam generator. Gasification plant according to claim 2, characterized in that at least one of the steam generator is equipped with a steam heater for overheating of the generated steam. Gasification plant according to claim 1, characterized in that the steam generating plant comprises a steam generator, from which a steam line branches off, which branches off into a gasification steam line and a steaming line and wherein there is a steam cooler in the course of the steam line. Gasification plant according to claim 4, characterized in that the steam cooler comprises a water supply and a space in which water and steam are brought into contact with each other. A method of operating an ash sluice in a gasification plant for gasifying solid carbonaceous feedstocks comprising a process gas consisting essentially of steam as gasification vapor and oxygen to form a solid or partially solid, non-flowable ash, the gasification plant including a fixed bed pressure gasification reactor and an ash sluice, comprising the following Process steps: (a) discharging the ash from the fixed-bed pressure gasification reactor into the ash sluice by means of a rotary grate with the ash inlet opening and the ash outlet outlet closed, (b) closing the ash inlet, relieving the ash sluice to ambient pressure, (c) opening the ash outlet, emptying the ash from the ash sluice , (d) closing the ash outlet opening, covering the ash sluice with string steam, (e) opening the ash inlet opening, characterized in that the temperature of the string steam is less than the temperature of the gasification vapor. A method according to claim 6, characterized in that the temperature of the clothing steam at least 50 ° C, preferably at least 70 ° C is less than the temperature of the gasification vapor. A method according to claim 6, characterized in that the temperature of the string vapor is at most 400 ° C and the temperature of the gasification vapor is greater than 400 ° C.

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