DE3133723C2 - Process for gasifying carbonaceous raw materials with superheated steam - Google Patents

Abstract

To achieve an increased reaction rate when gasifying carbonaceous raw material with H ↓ 2O, this raw material is suspended or emulsified in a liquid aqueous solution of the catalytically active salt in the reaction chamber and the amount of the catalytically active salt and pressure in the reaction chamber are dimensioned so that the liquid phase of the aqueous solution is retained.

Description

- That the carbonaceous substance in the reaction chamber in a liquid aqueous solution of the catalytically active salt is suspended or emulsified and

- That the concentration of the catalytically active salt in the solution and the temperature and the pressure in the reaction chamber are so dimensioned that the liquid phase of the aqueous Solution remains

2. The method according to claim i, characterized in that the reaction temperature is below the melting temperature of the catalytically active salt at the pressure prevailing in the reaction chamber and 25 tion of CO to methane and water according to the 374 ° C gross reaction equation CO + 3 H ₂ = CH ₄ + H ₂ O

A method of gasifying fossil fuels with water vapor at elevated pressure and elevated pressure Temperature is known from the German Offenlegungsschrift 25 30 600. In the case of the one described there Process should work with a steam pressure of 50 to 600 bar and temperatures of 500 to 1100 ° and the catalyst should be dissolved in the gas phase.

Finally, on pages 137 to 139 there is also “Energy Research”, Vo. 4, 137 to 147 (1980) a method is known in which an aqueous solution of potassium carbonate is sprayed as a catalytically active salt on a raw material consisting of ground coal. The coal is then dried and fed into the reaction chamber of a fluidized bed reactor. In this fluidized bed reactor, H ₂ O is also introduced in the form of steam so that at a reaction pressure of 35 bar and a reaction ^{temperature of 700 0} C a gasification of carbon to carbon monoxide and hydrogen after Gross reaction equation C + H ₂ O = CO + H ₂ , a conversion of carbon monoxide to carbon dioxide and hydrogen according to the gross reaction equation CO- + H ₂ O = CO ₂ + H ₂ and finally a methanization

3. The method according to Ansprvsh 1, characterized in that water, if necessary. The catalytically effective salt or the salt mixture contains, is supplied.

4. The method according to claim 1 or 3, characterized in that as the catalytic salt, or as a mixture thereof, K ₂ CO ₃ , KO ", KHCO ₃ , KCL, NaCi, K ₄ P ₂ O ₇ , KBO ₂ , Na ₂ B ₂ O ₇ or CaCl ₂ is used.

The invention relates to a method for gasifying

expire. The potassium carbonate, which acts as a catalyst, not only accelerates the gasification, but also the setting of the conversion and

the methanation equilibrium.

The product gases hydrogen, carbon monoxide, carbon dioxide and Methane as well as the unreacted water. From this mixture can first carbon dioxide z. B. by a Monoethanolamine wash can be removed. Methane can then be separated off from the residual mixture by means of low-temperature distillation. The remaining hydrogen / carbon monoxide mixture can be used again Mixed water vapor, heated to reaction temperature

of carbon-containing substances, in particular of 40 heated and returned to the vortex light reactor, coal or petroleum, for treating this substance with.

superheated steam in a reaction space The invention is based on the object

under increased pressure in the presence of catalytic reaction rate of the gasification even further

to increase and thereby either at the same

effective salt, especially an alkali salt or a mixture of such salts.

A process for the production of water gas, in which carbon and superheated water vapor in a molten salt bath using a catalyst to be brought to reaction is by the Germans

catalytically active salt is suspended or emulsified and that the concentration of the catalytically effective salt in the solution, as well as temperature and

Reaction temperature an increased generation rate of product gas or with the same generation rate one to achieve reduced reaction temperature.

In order to achieve this object, a method of the type mentioned at the outset is characterized in accordance with the invention Patent specification 5 39 891 known The catalyst is used w characterized that the carbonaceous substance in the the increase in the reaction rate It becomes the reaction space in a liquid aqueous solution of the In this process added to the molten salt bath In of the patent are as catalysts in a Melt of sodium chloride, sodium carbonate, at

a melt of sodium chloride, calcined soda 55 pressure in the reaction chamber so that the or alternatively, red iron oxide is disclosed. liquid phase of the aqueous solution is retained

A process in which strong gas by gasification on this. This ensures that im

Bituminous fuels always produce water in the liquid phase under increased pressure by means of water vapor under the reaction chamber, is available from DE-PS, in which the catalytically active salt is genuinely 5 76 134 known. In this publication it is shown that the methane yield can be increased by increasing the carbon monoxide and hydrogen by increasing the carbon monoxide and hydrogen according to the gross peak pressure in the reaction vessel. tion equation C + H ₂ O = CO + H ₂ quite considerably

This document also shows that it can accelerate. Comparative measurements resulted desired reactions by catalytically active 65 compared to gasification according to the known Additions, such as iron oxide, alkalis or the like, give the process six times the reaction speed Fuel are mixed in, are accelerated To reduce corrosion on the reaction vessel,

can. ,. especially by molten chlorides, it is

favorable, the reaction temperature below the melting temperature of the catalytically active salt at im The pressure prevailing in the reaction chamber and above 374 ° C to be selected. This makes a sufficiently faster The gasification process is achieved when the pressure is not too high, because it is sufficiently catalytically effective aqueous salt solution is present in the reaction space

Advantageously, water, which optionally contains the catalytically active salt or salt mixture, are fed.

This makes it possible to work with relatively low pressure in the reaction space, so that also the compression work to promote the H2O in the reaction space to maintain the aqueous salt solution in the liquid phase is proportionate is low

The invention and its advantages are based on the drawing, which schematically shows a device for Implementation of the method according to the invention shows, explained in more detail using two exemplary embodiments:

In the drawing is a Vorratsgef.äß 1 for water via a water pump 2 with the input of a electrically heated once-through steam generator 3 connected. The steam outlet of this continuous steam generator 3 is by means of a steam line 4 at the bottom of a pressure-tight closed, hollow cylindrical Reaction vessel 5 connected. This reaction vessel 5 can be heated electrically, in particular when starting the process. Near its bottom it has an ash discharge 6 on the side and a nozzle 7 for feeding in near its cover Raw material, e.g. B. ground coal on. Between the cover of the reaction vessel 5 and this nozzle 7 a sieve 8 is located in the reaction space of the reaction vessel 5.

On the lid of the reaction vessel 5 there is a discharge line 9 for the reaction products, including not converted water vapor connected. In this derivation 9 there is a controllable expansion valve 10 with a regulator 11, which is not closer illustrated, the expansion valve 10 upstream pressure sensor in the discharge line 9 is assigned to Dem The expansion valve 10 is a cooler 12 in the discharge line 9 and this in turn is a water separator 13 downstream with a water collecting vessel 14 Product gas connected.

According to a first embodiment, there is a suspension of ground coal coke with a carbon content of about 85% by weight in a liquid aqueous solution of potassium carbonate in the reaction chamber in the reaction vessel 5 according to the drawing. The reaction space contains 1.8 grams of potassium carbonate per millimeter of hard coal coke. The grain size of the ground hard coal coke is between 1 and 4 mm. The reaction temperature in the reaction space of the reaction vessel 5 is 650 ^° C. and the pressure in this reaction space is 250 bar. The coke, which is specifically lighter than the salty water, is prevented from floating by the sieve 8, which is slightly immersed in the liquid aqueous potassium carbonate solution in the reaction chamber of the reaction vessel S. The amount of potassium carbonate present in the reaction chamber of the reaction vessel 5 is so high that that the level of the liquid aqueous salt solution is located between the sieve fc and the lid of the reaction vessel 5.

Water vapor generated by the water pump 2 in the once-through steam generator 3, whose temperature of 650 ^° C. and whose pressure of 250 bar is in the supercritical range of pure H2O, is fed through the steam line 4 into the reaction vessel 5 at its bottom. This water vapor flows through the liquid aqueous salt solution in the reaction space of the reaction vessel 5, in which the ground hard coal coke is suspended.

With the aid of the controllable expansion valve 10, the pressure in the reaction chamber of the reaction vessel is increased 5 held constant at 250 bar. Ash can be removed from the reaction vessel 5 from the ash discharge 6 withdrawn and conveyed through the nozzle 7 freshly ground hard coal coke into the reaction vessel 5 will. By adding potassium carbonate to this coal coke conveyed through the nozzle 7 If necessary, iialium carbonate formed by the removal of ashes from the nozzle 6 can be used in the reaction space of the reaction vessel 5 be balanced. In this way, continuous operation of the system is possible.

The reaction products leaving the reaction vessel 5 through the discharge line 9, including the unreacted water vapor are cooled in the cooler 12. The water condensed in this case is in the Water separator 13 deposited in the water collection vessel 14. The product gases are through the Discharge 15 withdrawn from the water separator 13.

For the specified operating conditions, a

Gasification rate in the reaction space of the reaction vessel 5 of 03Gew .-% carbon per

J5 minute achieved The composition of the product gas withdrawn in the discharge line 15 is 16% by volume CH ₄ (methane), 1% by volume CO, 36% by volume Co ₂ and 46% by volume H ₂ .

If after a further execution example in

■ »ο reaction space of the reaction vessel 5 according to FIG. 1 a liquid aqueous solution of a mixture of potassium chloride and sodium chloride (60 wt .-% KCl and 40 wt .-% NaCl) used to treat the same hard coal coke as in the first embodiment, is obtained at a reaction temperature of 650 ° C and a Pressure of 170 bar in the reaction chamber of the reaction vessel 5 at the outlet 15 a product gas which contains 19% by volume CH ₄ (methane), 1% by volume CO, 30% by volume CO ₂ and 49% by volume

so contains _{H 2.} The reaction rate in the reaction space is 0.06% by weight of carbon per minute. To maintain a liquid, aqueous solution in the reaction space of the reaction vessel 5 is at the. en embodiment, only one water vapor partial pressure of at least about 90 bar is required at 65O ⁰ C, while this, for pure NaCl least 400 bar are required bar with pure KCl at least 200 bar and at about pure potassium carbonate 200th

The catalytically active salts used are to be selected from the point of view that they _{form a system with H 2} O which can form a liquid phase of the aqueous salt solution at the reaction temperatures in question for the gasification of the carbonaceous raw material.

The liquid phase of an aqueous salt solution differs from a molten one Phase of the salt in that in it when exceeded

a saturation concentration of the salt can always exist excreted solid salt, which in the molten phase except at the triple point of the salt is not possible so that a liquid phase the aqueous salt solution can form, the salt concentration in the reaction space must be higher than that Saturation concentration of the salt in the gas phase at the gasification temperature. Above a certain

critical pressure, which depends on the gasification temperature is dependent, there can be no phase interface between the liquid and gaseous phase in the reaction space exist.

In addition to potassium carbonate (K ₁ COj), the salts KOH are particularly suitable as catalytically active salts. KHCO ₃ , KCl, NaCl, KBOi, ICPjO ₇ , Na ₂ B ₂ O ₇ and CaCl ₂ .

1 sheet of drawings

Claims (1)

Patent claims: 1. Process for gasifying carbonaceous substances, in particular coal or petroleum, by treating this substance with superheated steam in a reaction space under increased pressure in the presence of a catalytically active salt, in particular an alkali salt, or a mixture of such salts, characterized in that