DE3422202A1 - Process for catalytic gasification - Google Patents

Abstract

The catalytic gasification of coals or cokes or carbon-containing materials of the widest provenance and composition, preferably by steam, is currently still in the development stage. Industrial introduction has hitherto failed because of the costs of the raw materials such as potassium carbonate used for the potassium preferred for the development of catalytic activity at low temperatures, which costs result both because of the specific price of the potassium carbonate and also because of the high catalyst requirement of potassium carbonate of up to 30%. In contrast, it has been found that by the use of certain raw materials or raw material mixtures which contain the alkali metals potassium and/or sodium in the form of non-readily degradable and reducible compounds such as chlorides and sulphates, a catalytic activity comparable to the carbonates can be achieved. However, the decisive advantage of the salts or salt mixtures underlying the invention lies in that the main components are available almost without restriction as minerals and can be used as such directly or after simple redissolution processes, that is, are available particularly inexpensively. Certain additives are available as by-products of the chemical and metallurgical industry.

Description

Process for catalytic gasification

It has long been known that mineral or inorganic additives in the gasification of coal with hydrogen, water vapor, carbon dioxide or even Mixtures of the same, which also contain oxygen (autothermal gasification) and / or carbon monoxide (multi-stage gasification, circulation) may contain the gasification reaction accelerate catalytically. They are responsible for the catalytic effect Metals contained in the mineral or inorganic aggregates. Have so for the hydrogenative gasification, which is preferably carried out under increased pressure is proven, iron and the ferrous metals to be particularly active (1). Same metals are also excellent catalysts of steam gasification, provided they are under Gasification conditions are present in a reduced state.

This presupposes reducing gasification conditions.

The outstanding advantage of ferrous metals is that they contain extremely low levels of about 0.5 wt. metal for maximum acceleration of the gasification reaction are sufficient. Iron also has the advantage that it comes in different salts (e.g. in pickling waste water or waste acids from ilmenite digestion) in sufficient quantities Quantity and is available inexpensively. So it would be an ideal catalyst.

The decisive disadvantage of iron and the other ferrous metals however, is that they are bound by the organically and inorganically bounds present in coals Sulfur are poisoned and thereby largely lose their catalytic activity. A certain compensation is possible by increasing the temperature, so that iron is still to be regarded as a catalyst with favorable properties for high-temperature gasification is.

In addition to the ferrous metals, especially the alkali metals have proven to be proved to be excellent catalysts. They are both in a reducing atmosphere (e.g. H2 / CO / H20 mixtures) as well as under oxidizing conditions (H20, H20 / 02, CO2) catalytically active. Given the catalytic activity and availability Potassium enjoys particular technical interest. The advantage of this metal as is the case with the other alkali metals compared to iron and ferrous metals, that they are catalytically active at lower temperatures and also by the Sulfur present in coal has little or no catalytic activity be affected. However, the existing activity at the low temperature can are only fully effective if such alkali or

Potassium salts are used as catalyst raw materials, which are relatively lower temperatures (500 - 600 "C) to the catalytically active form, probably the metal, can be reduced under gasification conditions. Such connections are for example the carbonates, nitrates and hydroxides. On the basis of potassium carbonate a process has also already been developed to pilot scale in which one Pressure of about 3.5 MPa and 700 "C is generated from coal methane. The high cost for the catalyst raw material, which is not only true for the potassium carbonate, but in the same way For other easily reducible potassium salts, the extraordinarily high catalyst requirement applies of up to 30 parts by weight, but above all the high catalyst losses Reaction with the mineral components of the coals with the formation of silicates are a technical realization of the process for economic reasons Ways. To make matters worse, the recovery of the potassium from the gasification residues technically and economically is not solved.

Given these problems, it is not surprising that despite one thing Decades of extremely intensive research and development in the field of catalytic Coal gasification no technically relevant process was found. According to the above In remarks, it is obvious that the problem is primarily addressed by locating a suitable catalyst raw material should be to solve. Such a catalyst raw material should be available in sufficient quantities, inexpensively and, above all, under gasification conditions be easily reducible. The problem of availability and cost would be through use to solve a mineral raw material. A typical example is potassium chloride called, which is present in sufficient quantities in hard salts. This stable However, salt cannot be reduced or can only be reduced with difficulty under gasification conditions is hydrolysis by water at best. The solution to the problem could be by accelerating the activation process, i.e.

Transfer to the active state can be found.

Gasification studies with binary salt mixtures were therefore carried out of mineral origin as catalyst raw materials. Were used for example mixtures of potassium chloride with magnesium chloride, magnesium sulfate, Calcium carbonate and, on a trial basis, also with vanadium pentoxide.

In addition, ternary systems were also investigated as catalyst raw materials, for example mixtures of potassium chloride, magnesium sulfate and various iron salts. The gasification investigations were carried out with graphites as model materials and above all carried out with natural coals. The catalyst raw materials were the graphite or mixed dry with the coals, the catalyst content between approximately 1 and 50 mass% were varied. In addition to the above-mentioned catalyst systems became the effect of the well-known, catalytically active potassium compounds such as potassium carbonate and potassium nitrate studied comparatively. In further experiments became also pure potassium sulfate, which is made up of potassium chloride through simple dissolving processes can be obtained without and with added iron.

A laboratory fixed bed reactor was used for the gasification studies, which is designed for pressures up to 5 MPa and temperatures up to 1,200 ° C. The temperature rise always took place linearly in order to directly observe the start of the gasification reaction to be able to. Pure hydrogen, H2 / H2O and Ar / H2O mixtures were used as gasification agents different composition as well as pure carbon dioxide are used. The gassing was followed by continuous gas analysis using infrared analyzers.

The tests showed that mixtures of potassium chloride and magnesium chloride have a higher activity in Ar / H20 than pure potassium chloride. The activity however, the mixtures cannot be compared to that of potassium carbonate or potassium nitrate. Surprisingly high activity was found with mixtures of potassium chloride and magnesium sulfate (0.0955 g KCl + 0.25 g MgSO4 7 H2 0 per 0.5 g residue to be gasified) and potassium chloride and calcium carbonate (0.0955 g KCl + 0.062 g CaCO3 per 0.5 g residue to be gasified) observed, both in Ar / H2O and in pure carbon dioxide. The activity this mixture is comparable to or even greater than that of potassium carbonate or potassium nitrate. The results with ternary systems (potassium chloride, magnesium sulfate, Iron (II) chloride or iron sulfate or iron oxide) were even better than with the underlying binary systems of potassium chloride and magnesium sulfate.

Based on these results, studies with potassium sulfate were also carried out and the above-mentioned iron salts as well as with pure potassium sulfate. In these cases, all gasification agent mixtures mentioned at the beginning were used as gasification agents used.

Surprisingly, both in oxidizing (Ar / H2O) as well as in a reducing (H2 / H2O) atmosphere that potassium sulfate is catalytically active is, and that this catalytic activity by adding an iron salt (for example 1 to 2 parts by mass of iron per 5 parts by mass of potassium) can be increased significantly can.

The same positive results were obtained with gasification with carbon dioxide found. For example, in all gasification atmospheres, the activity is one Mixture of potassium sulfate and iron sulfate comparable to that of potassium carbonate or potassium nitrate. Comparable activity means in all cases that the gasification reaction starts at about the same temperature and that also the maximum gasification rates are about the same size.

The lesson from the foregoing research is that in all cases the acceleration of the activation process is the basis for the Activity must be, and that the catalytic effect de facto exclusively from Running out of potassium. In the case of mixtures of potassium chloride and magnesium sulfate it would be It is conceivable that potassium sulfate is formed in an early stage of the gasification. Whose surprising catalytic activity was found in the experiment described above found. Wetting studies in a gasification atmosphere with graphite as a base showed that a melt is already present at 750 "C, which also penetrates the graphite. Obviously, this molten phase plays a decisive role in the activation and thus the catalytic activity. With the addition of the Iron compounds For potassium sulfate, a melt was already observed at around 650 "C, which in turn suggests that the iron compound is responsible for the decomposition or

Accelerated reduction of potassium sulfate. Melts in an inert atmosphere Potassium sulfate only at 1.069 "C. The same cause should be the effect of the potassium chloride / Magnesium chloride mixture (equimolar mixture of both components). A melt at 770 "C was found with potassium chloride, with the mixture being this temperature approx 500 "C This results with the mixture of potassium chloride and Magnesium sulfate suggests that when potassium chloride was mixed with calcium carbonate it is based on a similar mechanism, i.e. possibly formation of potassium carbonate at an early stage of gassing. From this it can be concluded that the possibilities of catalytically active salt mixtures does not refer to the examples mentioned above are limited, but that basically binary or multiple salt mixtures have a high catalytic activity where under gasification conditions an acceleration of the activation process takes place, be it due to the catalytic Effect of one or more components on the activation process, or be it due to an anion exchange, which under gasification conditions to an easily Reducible potassium or alkali compound leads. The foregoing observations are to be explained in more detail below with the aid of some examples.

Example 1 0.5 g of graphite (natural graphite Ceylon) was added with 0.0955 g Potassium chloride and 0.25 g MgSO4 7 H2 0 thoroughly mixed by rubbing, the mixture was compressed into tablets, which were then ground to a grain size of 0.4 to 1.0 mm became.

0.8455 g of this grain were in the gasification reactor at a total pressure of 2 MPa gasified with an equimolar Ar / H20-2 mixture. The temperature was with a speed of 4 K min to 900 "C, this temperature was then increased held for an hour. Samples with the pure components were made in the same way (0.0955gKCl per 0.5 g graphite and 0.25 g MgSO4.7 H20 per 0.5 g graphite) and K2CO3 (0.042 g K2C03 per 0.5 g graphite) and K2 SO4 (0.055 g K2SO4 per 0.5 g graphite) prepared and gassed. The gasification was carried out by on-line analysis of CO2 and CO tracked with IR analyzers. Figures (1a) and (1b) show the formation speed of CO2 and CO with increasing temperature up to 900 "C and during the hour isothermal gasification at 900 "C.

It can be seen that the formation of CO2 and CO when the KCl / MgSO4 mixture is added starts at about the same temperature as when the highly active K2C03 was added, and the maximum formation rates of both gases are also when using the Mixture as a catalyst comparable to that with the addition of K2CO3. In contrast in addition, it is found that both pure KCl and, to an even greater extent, pure MgSO4 * 7 H2 0 are only weakly catalytically active. The reactivity of pure graphite without Surcharge is completely negligible. The high gas formation rates that with the KCl / MgSO4 mixture cannot be achieved by adding an additive Explain the effect of the two pure components. A surprisingly high catalytic activity shows K2 SO4, but with this salt the catalytic Reaction occurs much later than with K2CO3 or the mixture under investigation KCl and MgSO4 .7 H2O. A completely analogous gradation of activity was also found in the gasification of a coal (GFK Leopold) found. Results with this coal will be described in the following example (2).

Example 2 After the preparation of the described in Example (1) Samples were added to 0.5 g GFK Leopold, to which 0.055 g K2 SO4 and 0.049 g FeSO4g7 H2O were added were, in the gasification reactor with a temperature rise of 4 K min to Final temperature of 850 "C and a one-hour holding time at the final temperature in an equimolar H2 / H2O atmosphere at a total pressure of 2 MPa. In Samples with the pure components of the catalyst mixture were made in the same way (0.055 g K2SO4 per 0.5 g GFK Leopold and 0.049 g FeSO4w7 H2O per 0.5 g GFK Leopold) as well as samples that were used as reference K2CO3 (0.042 g K2CO3 per 0.5 g coal) and KNO3 (0.064 g KNO3 per 0.5 g coal), prepared and gasified. Comparative was also investigated the reactivity of the untreated GFK Leopold. The main products of the Gasification reaction CH4 and CO were recorded by IR analysis.

Figures (2a) and (2b) show the formation rates of CH4 and CO with increasing temperature up to 850 "C and during the following one hour gasification at 850 "C. It can be seen that the rate of formation of the CH4 formed as the main product under these reaction conditions on addition of the Mixture of K2 SO4 and FeSO4 the methane formation rate, which with the addition other active catalyst raw materials (KNO3, K2CO3) achieved will, surpasses. The CO formation rates with these catalyst raw materials are about the same size.

The sharp drop in gas formation rates in the isothermal range is due to the high carbon turnover. In contrast to the active mix from K2 SO4 and FeSO4 .7 H2O, the pure components of this mixture show a lower level Activity. In the case of FeSO4 7 H2 0 there is practically no increase in activity achieved beyond that of the untreated coal. In the case of K2 SO4, one of the gas formation rate significantly different from the non-catalyzed reaction (CH4, CO) only observed at a considerably higher temperature. This results in, that the high activity of the catalyst mixture K2SO4 / FeSO4 does not go through a additive effect of the pure catalyst components K2 SO4 and Fest4 * 7 H2O results.

Literature (1) K. J. Hüttinger, Fuel 62 (1983), 166 - Blank page -

Claims (7)

Patent claims 1. Process for the catalytic gasification of coal, Coke carbons and carbon-containing residues of any kind with hydrogen, Water vapor, carbon dioxide as well as mixtures of these gases, the carbon monoxide and also May contain traces of other gases, characterized in that as catalysts such raw materials (salts) or raw material mixtures (salt mixtures) are used, in which during the heating to gasification temperature, preferably under gasification conditions, due to mutual catalytic influence and / or due to an anion exchange the activation process, i.e. the transfer of the catalytically active raw material (s) is accelerated into the metal or an easily reducible compound, though the starting compound (s) (catalyst raw material (s)) catalytically in the gasification active component (s) is or are thermally and chemically stable to such an extent that in the absence of one or more of the three above, activation accelerating processes do not or only at high temperatures or below activated under extreme conditions (e.g. supercritical high density steam) and thus can be catalytically active. 2. A method for catalytic gasification according to claim 1, characterized characterized in that as the one or more containing the catalytically active component (s) Raw material (s) technical potassium chloride and / or technical sodium chloride and / or technical grade potassium sulphate and / or technical grade sodium sulphate can be used, with the salary of potassium and / or sodium in terms of the amount of used raw material to be gasified is between 1 and 50% by mass. 3. A method for catalytic gasification according to claim 1 and 2, characterized characterized in that the claimed according to claim 2, the catalytically active component Raw materials containing potassium chloride and / or sodium chloride and / or potassium sulfate and / or sodium sulfate in mixtures with magnesium carbonate and / or magnesium sulfate and / or containing calcium carbonate and / or magnesium sulfate as the main component Raw materials are used, the content of magnesium and / or calcium in relation on the potassium and / or sodium contained in the mixture at least 25 mol% and is a maximum of 175 mol%. 4. A method for catalytic gasification according to claim 1 and 2, characterized characterized in that the claimed according to claim 2, the catalytically active component Raw materials containing potassium chloride and / or sodium chloride in mixtures with magnesium chloride and / or raw materials containing calcium chloride as the main component are used, the content of magnesium and / or calcium with respect to that in the mixture contained potassium and / or sodium is a minimum of 25 mol% and a maximum of 125 mol%. 5. A method for catalytic gasification according to claim 1 to 4, characterized characterized in that the catalyst raw material (s) additionally contains a vanadium compound contain, the content of vanadium in relation to the catalytically active potassium and / or sodium is a minimum of 2 mol% and a maximum of 50 mol%. 6. A method for catalytic gasification according to claim 1 to 3, characterized characterized in that potassium sulfate and / or sodium sulfate and / or the mixture of Potassium chloride and magnesium sulfate with additives of a technical inorganic Iron salt, preferably iron chloride and / or iron nitrate and / or iron sulfate can be used, the content of iron in terms of potassium and / or sodium is a minimum of 1 mol% and a maximum of 100 mol%. 7. A method for catalytic gasification according to claim 1 and 2, characterized characterized in that technical potassium sulfate is used as catalyst raw material, the content of potassium in relation to the amount of used to be gasified Material is between 1 and 25 mass.