DE3017998A1 - Removal of minor impurities from crude partial oxidn. gas - by treatment with sulphided iron catalyst at relatively low temp. - Google Patents

Abstract

A process is claimed for the purificn. of crude gas from the partial oxidn. (gasification) at a temp. of 1000-2000 deg.C of solid or liq. hydrocarbons. After removing dust, and before further treatment, the gas is passed pref. at a temp. of 90-200 deg.C and a pressure of 2-60 bar, over a catalyst contg. 2-65 wt.% Fe in sulphided form, to remove traces of N oxides, SO2 and O2. The catalyst may be added as Fe oxide or hydroxide, or mixed Fe, Cr oxide (Fe/Cr=5-15 wt./wt.) or gas purificn. catalyst contg. Fe(III) hydroxide. It is normally sulphided by the H2S in the crude gas. Used for the treatment of gases from e.g. the Koppers-Totzek gasification of coal, to be used finally as heating gas, synthesis gas, reducing gas etc. It prevents deposition downstream of S, Fe sulphide, or Fe nitrosyl complexes on gas compressor turbine rotors or interstage coolers, and of solid NO in the liq. N2-wash system. The catalyst is cheap. The treatment temp. is lower than in prior art processes, so a special re-heating of the gases is not required.

Description

Process for the catalytic treatment of partial oxidation raw gas.

The invention relates to a method for catalytic treatment by partial oxidation (gasification) of solid and / or liquid carbonaceous Raw gas extracted from material at temperatures between 1000 and 2000 "C.

The production of raw gas by partial oxidation of carbonaceous Starting material and the subsequent processing of this raw gas for different Uses, such as heating gas, synthesis gas or reducing gas, has been known for a long time and is used in a variety of large-scale engineering Systems realized with success. A well-known, often used for the stated purpose and is a gasification process operating in the above temperature range for example the Koppers-Totzek process, in which the starting material to be gasified is subjected to so-called entrained flow gasification.

A major advantage of this procedure is, among other things, in it to see that it is extraordinary in terms of the carbonaceous feedstock is flexible. This means that everyone can use this method in practice occurring types of coal as well as other solid and / or liquid fuels such as for example pitch, tar, petroleum coke, heavy hydrocarbons and distillation or production residues from the petrochemical industry are gasified. the further processing of the resulting raw gas depends of course on the respective purpose.

For example, the raw gas for the ammonia production has to be in the train the further work-up in many cases of a more or less strong compression as well as treatment at low temperatures, such as a methanol cold wash or a liquid nitrogen wash.

However, it has been shown that when performing both of these Treatment stages may have certain problems and in some facilities Difficulties can arise. So were on the impellers of the raw gas compressors as well as deposits of sulfur and iron sulfide in the associated intercoolers and iron nitrosyl complexes (so-called Roussint's salts). Index cold MethanoWash led to the formation of sulfur as well as sulfur-iron compounds soluble in methanol to undesired deposits in the heat exchangers. In the low temperature part of the Liquid nitrogen scrubbing also resulted in undesirable deposits in the heat exchangers which were due to freezing NO and which can only be eliminated by defrosting could become.

The only cause for these malfunctions was initially the Presence of nitrogen oxides NO, which are considered trace constituents in the raw gas are normally contained in an order of magnitude of <100 ppm. In more recent There is therefore time in the production of ammonia from coal gasification Synthesis gas has already been proposed to remove nitrogen oxides from the gas by a Treatment with a cobalt molybdate catalyst to remove. (Chem.

Closely. , February 1980, 88 - 90, 94) Further investigations the applicant have shown, however, that for some of the above Disturbances in addition to nitrogen oxides are also responsible for S02 and oxygen, soft also as trace constituents in the raw gas in an order of magnitude of 50ppm or <150 ppm. It must also be assumed that the mentioned trace constituents generally in the further processing of the raw gas to malfunctions (deposits) in pipes, compressors, washing stages, heat exchangers etc. can lead.

The invention is therefore based on the object of providing a method for to create catalytic treatment of raw gas obtained by partial oxidation, in which, in addition to the nitrogen oxides, the SO2 and oxygen are also removed from the raw gas will. At the same time, in the interest of the economy of this process if possible, a particularly inexpensive catalyst should be used. In addition, the ongoing operating costs should of course be kept as low as possible will. It is therefore desirable that the method according to the invention in a The lowest possible temperature level, which means excessive heating and cooling again avoid the raw gas.

det, can be performed. Furthermore, the pressure drop over the Catalyst are kept as low as possible.

The method described at the outset serving to solve this problem Art is characterized according to the invention in that its dusty Freed impurities and cooled to a temperature between 70 and 250 "C Raw gas before further gas treatment at a pressure between 1 and 100 bar as well with a space velocity between 3,000 and 30,000 Nm³ gas per 3 m of catalyst per hour is passed over a catalyst, which is the active Component 2 to 65 wt. - 7o (based on the total iron catalyst mass) rests, which is in sulfidic form.

It has proven to be particularly advantageous if the catalytic Treatment of the raw gas at a temperature between 90 and 200 4 C and one pressure between 2 and 60 bar.

To carry out the method according to the invention can be of a Catalyst starting material we assumed which mixtures of iron and Contains chromium oxides with or without a carrier material. . Furthermore, Fe - III - hydroxide * Fe - oxide hydrates, red sludge from bauxite production and iron oxide or. Hydroxide-containing gas cleaning compounds (so-called lawn iron ore) as catalyst starting material come into use.

The necessary sulfidation of the iron component of the catalyst starting material normally takes place by reaction with the H2S contained in the raw gas. It is therefore useful when performing the method according to the invention a minimum sulfur content of 7 mg / Nm³ raw gas is not fallen below.

Under certain circumstances it is of course also possible to first use the catalyst starting material a special sulfidation with a H2S, CS2 and / or mercaptans containing Submit gas.

The sulfidation described above may react Chromium component not present or only to a very limited extent. The chrome stays therefore retained in the catalyst in oxidic form and functions primarily in the process as a structural reinforcement of the catalyst.

If mixtures of iron and chromium oxides are used as the catalyst starting material are used, it is useful if there is an Fe in these mixtures : Cr - weight ratio of 5: 1 to 15: 1 is present.

As stated above, the active component can be used in the catalyst with or without a support material. Unless the catalyst Contains carrier material, A1203 or SiO2 can preferably be used as carrier material Find. However, other known carrier materials such as MgO, ZrO2 and-TiO2 as well as their mixtures and compounds (spinels) and also clays or alumina can be used for this purpose.

Because of the high space velocities at which the inventive Procedure can be carried out, it may be useful if the active component of the catalyst is applied to the support body by their Shaping prevent the pressure drop across the catalyst bed. This is for example achieved by a honeycomb structure of the carrier body.

The inventive treatment of the raw gas takes place before the further Gas treatment, that is, before the so-called. Sour gas scrubbing and, if necessary, conversion, after the gas escaping from the gasifier by suitable measures, such as treatment in the cyclone separator and / or in so-called. Wet washing, from its dusty solid Impurities has been freed. If in the course of the Follow-up of the raw gas compression is provided, the invention is 5 gemäs se gas treatment expediently before or between the first compression stages of the raw gas carried out. It reacts with the hydrogen present in the gas the SO2 converted to H and the nitrogen oxides to N2 and / or NH3. The formation of elemental sulfur, Iron nitrosyl complex (so-called. Roussint's salts) or carbon according to the Boudouard equilibrium has not been established.

In contrast, the oxygen contained in the raw gas turns completely into water implemented. That this is done at the relatively low temperatures at which the invention Procedure is carried out is possible, was surprising and unexpected when one takes into account the conditions of conventional cleaning.

There are at temperatures that are only comparatively little below the temperature level according to the invention, the nitrogen oxides from the Fe III - Hydroxide-containing gas cleaning compound bound in a complex, and the oxygen reacts in this case with the H2S with the formation of elemental sulfur. For economy of the method according to the invention is the relatively low one used However, the temperature level is of particular importance because it causes a special heating of the raw gas stream can be omitted.

The catalysts used according to the invention favor neither the conversion of CO to the water gas equilibrium nor the methanation of CO under the claimed reaction conditions. The sulfided catalyst is not damaged by water vapor. Finally, depending on the initial concentration, COS becomes corresponding to the simultaneous equilibrium between COS hydrogenation and GOS hydrolysis formed or removed.

The following is the effectiveness of the method according to the invention will be explained using four examples. In Examples 1, 2 and 4 was the feed gas used (raw gas) by partial oxidation of coal and in the example 3 obtained by partial oxidation of heavy hydrocarbons. In the examples 1 to 3, a mixture of iron and chromium oxide was used as the catalyst starting material used, while in Example 4 an Fe - III - Hydroxide-containing gas cleaning compound was used. The sulfidation of the catalyst feedstock occurred in all four cases due to the H2S content of the feed gas. more details of the examples result from the following information: Examples 1) Catalyst gang material: Fe / C r -oxides (ratio Fe: Cr = 9: 1) temperature 1500 C pressure : 2.5 bar Space velocity: 13000 h-1 Feed gas: H2 21.4 Vol .-% CO 51.4 "" CO2 8.0 "" N2 12.1 "H2O 6.2" "H2S 0.9" "NO 100" -ppm SO2 50 "" O2 50 "" In the product gas: NO 0.5 vol.ppm SO2 <2 "" NH3 70 "" others Components essentially unchanged.

2) Catalyst starting material: Fe / Cr oxides (ratio Fe: Cr = 9: 1) Temperature: 150 ° C. Pressure: 2.5 bar Space velocity: 26,000 h-1 feed gas : as in example 1 in the product gas: NO 3 vol. -ppm SO2 <2 NH3 50 other components essentially unchanged.

3) Catalyst starting material: Fe / C r - oxides (ratio Fe: Cr = 9: 1) Temperature: 150 ° C. Pressure: 2.5 bar Space velocity: 26,000 h-1 feed gas : H2 34.8 vol .-% CO 42.0 "" CO2 7.5 "" N2 9.2 "'H2O 6.2 H2S 0.3 NO 100 vol. -ppm SO2 50 "" In the product gas: NO 2.5 vol.ppm SO2 2 "" NH3 55 "" other components essentially unchanged.

4) Catalyst starting material: Fe - m - hydroxide (gas cleaning agent se) temperature: 150 ° C. pressure: 2.5 bar space velocity: 26000 h feed gas : as in example 1 In the product gas: NO 2 vol. -ppm SO2 2 "" NH3 60 "" "others Components essentially unchanged.

The present results show that in all four cases one effective reduction of the SO2 and nitrogen oxide content in the feed gas can be achieved could. The nitrogen oxides are mainly reduced to NH3. Example 4 deserves special attention in this respect, because absorbed here. Gas cleaning compound was used as a catalyst starting material. This is of course even cheaper than the mixtures of iron and chromium oxide used in Examples 1 to 3 and represents an extremely economical solution to the problem.

Claims (6)

Claims 1.) Process for the catalytic treatment of by Partial oxidation (gasification) of solid and / or liquid carbonaceous material Raw gas obtained at temperatures between 1000 and 2000 ° C, characterized in that that that freed of its dusty impurities and brought to a temperature between 70 and 250 ° C cooled raw gas before further gas treatment at a Pressure between 1 and 100 bar and with a space velocity between 3 3,000 and 30,000 Nm of gas per m of catalyst and hour is passed over a catalyst, as active component 2 to 65 wt .-% (based on the total catalyst mass) Contains iron, which is in sulfidic form. 2.) The method according to claim 1, characterized in that the catalytic Treatment of the raw gas preferably at a temperature between 90 and 200 ° C and a pressure between 2 and 60 bar. 3.) Process according to claims 1 and 2, characterized in that that catalysts are used in which the iron is in the catalyst starting material is initially present as an oxide or hydroxide, which by reaction with the in the raw gas contained H S or by special treatment with an H2S, 052 and / or mercaptans containing gas is converted into sulfidic form. 4.) Process according to claims 1 to 3, characterized in that that as a catalyst starting material iron-chromium oxides with an Fe: Cr weight ratio of preferably 5: 1 to 15: 1 are used. 5.) Process according to claims 1 to 3, characterized in that that as catalyst starting material a gas cleaning mass containing Fe - III - hydroxides is applied. 6.) Process according to claims 1 to 5, characterized in that that catalysts are used in which the active component is superficial has been applied to carrier bodies, the pressure drop due to their shape decrease above the catalyst bed.