DE2813208A1 - Gasification of solid fuels in molten slag bath - giving synthesis or reducing gas mixts. of improved compsn. - Google Patents

Abstract

Prodn. of cracking gas (CO/H2) mixt. from fuels, e.g. powdered coal, is effected by reaction with a gasifying medium, e.g. O2, in a high temp. alag bath through which the reactants flow. Used as synthesis or reducing gas mixts., e.g. for iron are reduction. Compared with the known process in which the reactants are blown tangentially onto a rotating slag bath, passage through the slag gives a reduction in CO2 content, e.g. from 14% to nil, and in H2S content, e.g. from 0.5% to 85 ppm. In the product gas.

Description

Method and device for the production of cracked gas

The invention relates to a method and a device for production of cracked gas from fuels and gasification media in contact with highly heated Slag.

A method for generating synthesis gas in the slag bath generator is known. In this process, for example, brown coal with 4% to 10% water and a grain size of 0 to 2 mm through carbon dioxide as a conveying means tangentially Two-substance nozzles printed on a rotating slag bath. At the same time, it is preheated Oxygen inflated. The heat of reaction is withdrawn from the highly heated slag, those in the concentric heating shaft through preheated air and fuel residues heated and rotated by the currents achieved during tangential injection 0 The slag formed in excess flows over an overflow from the heating compartment and granulated in a water bath.

As a gasification agent, 460 m3N of oxygen are used per ton of lignite with a purity of approx. 98 was added. 44 m3N of carbon dioxide are used for extraction consumed. The carbon conversion is given as 98.1%.

The synthesis gas produced by the known slag bath generator has for example the following composition: CO = 53.6, C ° 2 = 14.0% H2 = 30.7% CH4 = 0.5% N2 = 0.7% H2S = 0.5 5 'See the publications: "Production of reducing gas for the ironworks industry by converting moist brown coals into those heated by nuclear energy Bleibad "Dissertation by Dipl.-Ing.Jürgen Schneider, 1974, pages 121/122; and F. Dohmann: nStatus of the slag bath generatorn International magazine nGaswärmen 14 (1965) page 325.

In the case of the synthesis gas produced with the known slag bath generator the high proportions of approx. 14% to 15% C02 and 0.5% H2S are used of the synthesis gas as the starting product for synthesis processes or to carry out re duction processes as disruptive to possibly completely felt to be inadmissible. Because the intended use as a synthesis or reducing gas requires a proportion of C02 as close as possible to 0, of CO as close to 70 5 'as possible H2 between 20% and 25 5 '; sulphurous compounds such as H2S or COS should not exceed values of around 100 ppm in total.

Such, from the point of view of use, to be described as an ideal gas However, cracked gas is not possible with the known method of the slag bath generator achievable.

The object of the invention is to provide the known process for the production of Fission gas from fuels and gasification media in contact with highly heated slag to improve in order to obtain a cracked gas whose composition as possible the of the ideal gas.

It has now surprisingly been found that the solution to this problem this succeeds in that the fuel and the gasification medium through the slag be passed through.

In contrast to the well-known process for the production of synthesis gas in the slag bath reactor, the advantage of the invention is that the cleavage of the fuel at Passing through the slag so intimately Contact with complete closure by the highly heated slag and as a result the all-round heat supply with such great speed as a spontaneous reaction what is happening is that undesirable formation of CO 2 is prevented because of this cannot be stable at the temperature of the surrounding slag.

The same applies to the reaction between slag and sulfur, because here, too, the intimate contact of the reactants evidently results in a complete conversion of sulfur and / or its complex compounds to the basic components of the Slag intensified in such a way that the escaping gas is negligible has small traces of sulfur, the order of magnitude below the limit of 100 ppm.

In attempts to produce cracked gas according to the invention The following analysis values are the mean values from 10 tests: Fuel Ruhr hard coal Moisture: 3.5 5 'Sulfur content: 1.2 96 Grain size: 0/2 mm Slag temperature: 1,400 ° C bath height: 0.9 m basicity factor: 1.2 Cracked gas CO: 74.5 % CO2 0.0% H2 24.85% CH4 0.0% N2: 0.65% H2S / COS: approx. 85 ppm With an appropriate Embodiment of the invention, the passage is made in such a way that the fuel and the gasification medium at the lowest possible point in the Slag bath are initiated0 This can be done, for example, in such a way that the introduction is carried out from below, preferably through floor nozzles.

As is well known, the temperature of the slag bath depends on its basicity away. The basicity for its part depends - as is also known - according to the Sulfur content of coal.

In the case of fuels with a low sulfur content, the basicity and thus the melting temperature of the slag can also be relatively low.

In such a case, the procedure is expedient in that the introduction of fuel and gasification medium through from above at least one lance is made into the depth of the bath.

Both types of introduction of substances into a weld pool can be made by the Those skilled in the art can optionally be used as required.

An expedient measure in the design of the procedure sees before that in addition to the fuel and at least one oxidizing gasification medium a medium for regulating the basicity of the slag, preferably calcium oxide and / or magnesium oxide, is introduced into the slag bath.

In this case, BO can proceed that the oxidizing gasification medium as a carrier gas for the preferably fine-grain calcium oxide and / or magnesium oxide is used.

However, it may also be useful if the calcium or Magnesium oxide is introduced into the slag in a mixture with the fuel.

In an embodiment of the method, use can continue to be made of the measure be made that the preferably solid and conveniently fine-grained fuel with the aid of a carrier gas, preferably containing a hydrocarbon Gas is introduced into the slag bath.

Natural gas can preferably be used as the carrier gas.

This has the advantage that the carrier gas is also completely converted to CO H2 is split up without foreign substances taking part in the reaction.

Another measure essential to the invention in the design of the Method consists in keeping the various media separate from each other, however are introduced into the slag bath at immediately adjacent points.

The more intimate the mixture of those introduced into the slag bath with one another the substances to be reacted, the better the results will be with the process achieved according to the invention. On the other hand, however, there must be a mixture of the carbon carrier and the oxygen carrier -be avoided before introduction into the slag bath because otherwise the risk of an explosive reaction cannot be ruled out.

The advantage of the specified measure, namely that the media is connected directly Adjacent sites are introduced into the slag bath is based on the fact that their Mix according to Entry into the slag bath obviously optimal is.

This could also explain the surprising effect of the invention Find.

This is an important prerequisite for the functioning of the process autothermal process. That is, that is necessary to maintain the slag bath temperature as well as to cover the radiation and convection losses as well as for heating and finally, to cover the costs required for the endothermic cracking reaction Amounts of heat in the order of magnitude between 1,500 and 1,800 kcal per kg of fuel the fuel / oxygen reaction mechanism must be covered.

In the case of fuel with a relatively low calorific value, it can therefore happen that a heat deficit arises.

As a result, the slag bath would freeze and the process come to a standstill.

This difficulty is remedied with the invention in that according to one embodiment of the method, the drying and / or preheating at least The amount of heat required for the solid fuel is at least partially withdrawn from the cracked gas will.

This has the further advantage that the cracked gas in a for whose Forwarding and further use brought more favorable because lower temperature level will.

Another embodiment of the method, which is in the same direction acts, is characterized5 that the required for heating the oxygen carrier Amount of heat is at least partially withdrawn from the cracked gas.

A device for carrying out the method according to the invention is characterized by a temperature-resistant reactor for receiving the slag bath with devices for introducing gaseous, liquid or solid reactants under the surface of the slag bath, as well as with a gas collecting space for the gap gas and an adjoining line for discharging the gas, as well as with a Outlet opening for the slag.

This outlet opening is arranged approximately at the level of the bath level and by means of a preferably siphon-like configuration, it closes off opposite the gas space of the reactor.

In a further embodiment of the device it is provided that a Device for introducing the reactants into the slag bath as a multiple nozzle arrangement is designed.

This results in the possibility that at least the oxygen carrier guided separately from the carbon carrier in immediately adjacent channels and so introduced into the slag bath.

The multiple nozzle arrangement can be designed so that this has at least two channels arranged concentrically to one another.

And finally, the device has a heat exchanger for transmission of heat from the cracked gas to at least one of the gas generating media.

In the following the invention is based on an exemplary embodiment explained in more detail in the drawing and their function described. They show: Fig. 1 shows a block diagram of the complete system; FIG. 2 shows a reactor for receiving the Slag bath, in section, In Fig. 1, the storage bunker 1 contains fine-grain fuel, and the reservoir 2 granular calcium oxide as a medium for regulation the basicity of the slag.

With the help of the dosing chutes 3 and 4, both substances mixed in a defined ratio and as a mixture in the intermediate container 5 submitted. This is at its lower end with a metering discharge Rotary feeder 6 equipped, which is followed by a plug screw 7. This conveys the mixture of carbon and calcium oxide through the gas-tight lock 8 in the pressure vessel 9 belonging to a pneumatic conveyor system has a connection 10 for the pneumatic conveying means, for which in the shown Example natural gas (CH4) is used, which with the help of the booster pump 11 is brought to the pressure necessary for the pneumatic transport of the goods.

The pressure vessel 9 has the riser pipe 12 through which the powdery mixture of carbon and Ca0 is fed into the system. Included the mixture passes through a heat exchanger 14 with the delivery line 13, which Is part of the cooling unit 15 for the cracked gas generated.

Through the delivery line 13, the carbon-lime mixture reaches the Reactor 16 of the plant, which the liquid slag in the form of the slag bath 17 contains, as can be seen from the device partially shown in section- is.

In the example shown, technically purer is used as the gasification agent Oxygen with 98% 02, which is taken from an 02 system 18, which has a Shut-off and pressure reducing valve 19 is connected to line 20. This line 20 goes through the interior of the cooling unit 15 in the form of the heat exchanger 21, in which the oxygen gas is heated in countercurrent to a temperature of approx. 500 ° C will. The heated media, on the one hand the mixture of fine-grain fuel and fine-grain calcium oxide and, on the other hand, oxygen, are from below passed through the bottom nozzles through the slag bath. Thereby the hydrocarbons split and it forms cracked gas, which above the slag bath in the Gas collecting space 22 of the reactor 16 with a temperature of approx. 1,400 ° C is obtained. The cracked gas is discharged from the collecting space 22 of the reactor 16 through a line 23 and passed through the cooling unit 15, in which it is partially discharged its sensible heat to the reagents mentioned is cooled down to approximately 600 OC will.

In Fig. 2, the reactor 16 is shown in section on an enlarged scale. This contains the slag bath 17, the bath level 24 of which is formed like a siphon Overflow 25 is kept at an approximately constant level. From the gas collection room 22nd the product gas, symbolized by the arrow 26, is withdrawn.

The bottom nozzles 28, 28 'are located in the bottom part 27 of the reactor 16. In the present case, it is a question of concentric ring nozzles. The innermost channel 29, 29 'conducts the gasifying agent oxygen from the space 30, which through the Connection piece 31 is introduced into the space 30. Received through terminal 32 the space. 33 fine-grain calcium oxide with a carrier gas, while the space 34 through the connection 36 is supplied with coal dust and a carrier gas. These different Media flow through corresponding concentric channels of the nozzles 28, 28 'as concentric Flows into the slag bath and are as an intimate mixture of substances through the slag bath conveyed through, as symbolically indicated by the arrows 35, 35 '.

When passing through the slag bath 17, the calcium oxide goes into the slag over and binds the sulfur of the introduced fuel while the carbon is cracked in the presence of oxygen and becomes the product and cracked gas, essentially CO (approx. 76%) and H2 (approx. 23%) is split. As already described above, this product gas passes through the collecting space 22 of the reactor 15 with a temperature of about 1.4o0 0C according to the arrow 26 from the reactor 16. The described example of a plant to the Implementation of the method according to the invention is only to be understood as an example.

Other device designs which are at the discretion of those skilled in the art are also covered by the invention if they are one of the applicable claims suffice.

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Claims (1)

Patent claims 1. Process for the production of cracked gas from fuels and gasification media in contact with highly heated slag, d a d u r c h g e k E n n e i c h n e t9 that the fuel and the gasification medium through the slag passthrough werden0 2. The method according to claim 1D characterized in that the fuel and the gasification medium at the lowest possible point in the slag bath 3 method according to claim 1 or 2, characterized in that that the introduction through at least one floor nozzle is pre-standardized according to one of claims 1 or 2, characterized in that the introduction by at least one lance is made into the depth of the bath0 5. Procedure according to one of claims 1 to 4, characterized in that in addition to fuel and gasification medium a basic medium to regulate the basicity of the slag, preferably calcium oxide and / or magnesium oxide is passed through the slag0 6th Method according to one of Claims 1 to 5, characterized in that the gasification medium is used as a carrier gas for the basic medium. 7. The method according to any one of claims 1 to 5, characterized in that that the basic medium is introduced into the slag in a mixture with fuel. 8. The method according to any one of claims 1 to 7, characterized in that that the fuel is introduced into the slag bath with the aid of a carrier gas. 9. The method according to claim 8, characterized by the use a carrier gas containing hydrocarbons or carbon and oxygen, preferably natural gas, C02 or recirculated cracked gas. 10. The method according to any one of claims 1 to 9, characterized in, that the different media are separated, but at adjacent points in the slag bath be initiated. 11. The method according to any one of claims 1 to 10, characterized in, that the amount of heat required for drying and / or preheating the solid fuel are at least partially withdrawn from the cracked gas. 12. The method according to any one of claims 1 to 10, characterized in that that at least some of the amounts of heat required to heat the oxygen carrier are withdrawn from the cracked gas. 13. Device for performing the method according to one of the claims 1 to 12, characterized by a temperature-resistant reactor (16) for receiving of the slag bath (17) with devices (28, 28 ') for introducing gaseous, liquid or solid reactants below the surface (24) of the slag bath (17) as well as with a gas collecting space (22) and an adjoining line (23) to the Discharge of the product gas and with an outlet opening (25) for slag. 14. The apparatus according to claim 13, characterized in that the The outlet opening (25) is arranged at the level of the bath level (24) and is designed as a siphon is. 15. Device according to one of claims 13 or 14 ,. characterized, that the device for introducing the reactants into the slag bath as a multiple nozzle arrangement (28, 28 ') is designed which has adjacent channels for the reactants. 16. The device according to claim 15, characterized in that the Multiple nozzle arrangement having concentric channels (29, 29 ', 39, 39', 49, 49 '). 17. Device according to one of claims 1 to 16, characterized through a heat exchanger (14, 15, 21) between the product gas and at least one the reactants.