DE2362065A1 - PROCESS FOR REDUCING THE TOTAL SULFUR CONTENT OF CLAUS EXHAUST GASES - Google Patents

Description

SHELL INTERNATIONAL RESEARCH MAATSCHAPPIJ B.V.

The Hague, Netherlands

"Procedure for reducing the total sulfur content of Claus exhaust gases"
(Addition to patent .... (patent application P 21 35 522.6).)

Priority: December 15, 1972 - Great Britain - No. 58 020/72

The present application relates to an addition to the method to reduce the total sulfur content of Claus exhaust gases according to patent .... (patent application P 21 35 522.6).

The subject of the earlier law is a process for reducing the total sulfur content of Claus exhaust gases, in which one the exhaust gases above 175 C together with a free hydrogen and / or gas containing carbon monoxide passes over a catalyst which contains a sulfided metal of VI. and / or VIII. group contains on an inorganic oxide carrier, the treated exhaust gases through a customary, liquid, regenerable absorbent for 'hydrogen sulfide sends the unabsorbed part of the exhaust gases, possibly after combustion, into the. the atmosphere drains the absorbent loaded with hydrogen sulfide regenerated in the usual way and used for a new absorption, and the sulphurous water released during regeneration

hydrogen-rich gas in the usual way to a Claus process. With the aforementioned method xv is used for the subsequent Reduction of sulfur dioxide and other convertible sulfur compounds hydrogen-containing gas required for hydrogen sulfide either directly to the reducing catalyst bed ' fed or fed into the line through which the Claus exhaust gases are introduced into the reducing catalyst bed.

A burner built into the line and consisting of a burner and a mixing chamber can be used to heat the Claus exhaust gases will. In such a burner built into the line, a fuel is used together with an oxygen-containing one Gas burned in the burner. And the hot gases obtained are introduced into the mixing chamber, in which they are also mixed with Claus exhaust gases introduced into the mixing chamber are mixed and heated in the process. The oxygen-containing gas is in the Burner introduced in stoichiometric proportions so that those flowing to the reducing catalyst bed were heated Exhaust gases do not contain free oxygen. This method of the Heating of the Claus exhaust gases can, however, because of the subsequent feeding of the hydrogen-containing gas into the reducing Catalyst bed or in the line for feeding the; · Claus exhaust gases in the aforementioned bed can be dangerous. The danger in the aforementioned procedure is due to the possibility of ' back that the exiting the burner built into the line Exhaust gases e.g. due to a control error that leads to the introduction of an excess of oxygen or an excess of fuel leads into the burner built into the line, certain quantities

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contain genes of free oxygen "In this case" there is the Possibility of contacting the hydrogen containing Gas comes to an explosion with the free oxygen

The present invention accordingly represents an improvement of the method for reducing the overall sulfur content of Claus exhaust gases according to patent ... ο (patent application P 21 35 522 * 6). available in which the Claus exhaust gases are heated in.einem burner built into the line to temperatures above 175 ° C and in which a hydrogen-containing gas is fed to the Claus exhaust gases without the risk of explosion. The present invention facilitates the task of ensuring stoichiometric combustion of the fuel and the oxygen-containing gas _; in the burner built into the line. control, because of the accuracy with which the system must be operated, because of the practical elimination of the risk of explosion due to the contact of free oxygen with hydrogen. containing gas in the Claus exhaust gases _; is no longer of such critical importance with regard to the safety of the process. Nevertheless, it is of course desirable to maintain a practically stoichiometric combustion for reasons of economic operation and to keep the hydrogen consumption as low as possible to regulate the amounts of fuel and oxygen-containing gas precisely.

The present application accordingly relates to a. -_. Process for reducing the total sulfur content of Claus- Exhaust gases in which the aforementioned hydrogen sulfide and hydrogen

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field dioxide containing exhaust gases above 175 C together with a Gas containing free hydrogen and / or carbon monoxide are passed over a catalyst which is a sulfided metal the VI. and / or VIII. group on an inorganic oxide carrier contains, in which the treated exhaust gases by a common, liquid, regenerable absorbent for hydrogen sulfide will be sent, in which the unabsorbed part of the exhaust gases is discharged into the atmosphere optionally after combustion, in which the hydrogen-laden absorbent in usually regenerated and used for a new aosüi-ption and in which the hydrogen sulphide-rich released during regeneration Gas is fed to a Claus process in the usual way, according to patent .... (patent application P 21 35 522.6), which is characterized in that the Claus exhaust gases to temperatures be heated above 175 ° C by passing them through a burner built into the pipe in which a fuel is burned with an oxygen-containing gas and in which the for the subsequent reduction of the sulfur dioxide to hydrogen sulfide required hydrogen-containing gas is fed in directly will.

- The direct feeding of the hydrogen-containing gas into the burner built into the line has the main advantage on that, provided that after the combustion of the fuel for any reason there is an excess of free oxygen in the combustion gases is present, the excess oxygen burns spontaneously with the hydrogen that is built into the line Burner is included. The oxygen gets on that way

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- 5 - controlled and safe way removed from the exhaust gases.

The hydrogen-containing gas must be fed to the process in an amount sufficient for the complete reduction of all sulfur dioxide and the other convertible sulfur compounds in the Claus exhaust gases. Preferably an excess of Sas containing hydrogen is fed. In addition, all of the hydrogen-containing gas required for the process is preferably in d.en. fed into the pipe built-in burner. This has Üzn advantage ^ that no additional gas to ^ power lines containing the hydrogen necessary and that the safety ^ tolerance limits of the permissible in the built-in! Line burner amount of oxygen are high regard because the existing in the burner large amount of hydrogen containing Gas burns spontaneously with any free oxygen formed. In this way, relatively large amounts of free oxygen can be burned in a safe and controlled manner in the burner built into the pipe.

However, it is not necessary that the entire procedure to be fed hydrogen-containing gas into the line built-in burner is fed. Part of the hydrogen containing gas can be installed in the burner in the line and the remainder is fed directly into the catalyst bed of the reduction stage or to that through the exhaust gas feed line fed to the reduction stage flowing hot exhaust gases

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will. The ones fed into the burner built into the line

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The amount of gas containing hydrogen must not fall below a certain minimum value Burner contained due to an imprecise control of the feed of fuel and / or oxygen. ting gas in the burner can be expected during operation, this minimum amount of hydrogen-containing gas accordingly depends on the accuracy of the control mechanism used ο In general, at least that required to burn 10 percent _{a of} the oxygen-containing gas in the Burner built into the line is fed, required amount of hydrogen-containing gas fed ^r

Regarding the type and amount of the hydrogen-containing gas suitably used in the present process and with regard to the operating conditions expediently used, reference is made to patent application P 21 35 522.6.

The hydrogen-containing gas can be incorporated in the line Burner can be fed at any point at which the temperature to ensure spontaneous combustion .of any free oxygen that may be present is sufficient. Fm absolutely ensure that, if necessary, in the combustion gases Free oxygen present in the burner built into the line spontaneously when it comes into contact with hydrogen burns, the hydrogen-containing gas is preferably on at one point in the burner built into the pipe.

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conducts at which the temperature of the gases in the burner is at least 500 ° C and preferably at least 600 ° C. ·

According to a preferred embodiment of the present invention, the hydrogen-containing gas is introduced into the burner installed in the conduit by spreading it around the flame formed by the combustion of the fuel and the oxygen-containing gas. In this way, the hydrogen-containing gas is not only introduced into the burner installed in the line at a point at which the gas temperature exceeds 50O ⁰ C, but there is also good distribution of the hydrogen-containing gas in the burner installed in the line . In this way, spontaneous combustion of the hydrogen-containing gas with any free oxygen present is ensured. The hydrogen-containing gas is preferably distributed around the flame by means of one or more nozzles. . ·

The point at which the Claus exhaust gas in the built into the line Burner is initiated is not critical. However, to the combustion of the fuel and the oxygen containing it Not to disturb the gas, the exhaust gases are preferentially on a point introduced into the burner at which the combustion is .practically completed.

D. the ratio of the amount of the in the mixing chamber to the. management built-in burner fed - Claus exhaust gases; depends on the amount formed in the burner

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e.g. on the calorific value of the fuel, on the temperature of the inflowing Exhaust gases and the temperature to which the exhaust gases must be heated. In general, however, the molar ratio is from Claus exhaust gases fed into the burner installed in the line to the combustion of the fuel and of the oxygen-containing gas formed in the burner combustion gases from 4: 1 to 50: 1.

A method will be described below with reference to the drawings described in which the inventive method is expedient can be used to reduce the total sulfur content of Claus exhaust gases. Details of the system, such as valves, Pumps and control instruments are not shown in the drawings.

Fig. 1 shows a flow diagram for the reduction of Claus exhaust gases, the subsequent absorption of the hydrogen sulfide and the regeneration of the absorbent, in which the The aforementioned exhaust gases in a burner built into the line, in which all of the hydrogen required for the reduction stage containing gas is fed directly, heated to temperatures above 1? 5 ° C.

Figures 2 and 3 show two types of built-in conduit Burners which can conveniently be used in a method according to the invention.

In Fig. 1, reference numeral 1 represents a line through which

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the exhaust gases from a Claus plant are introduced into a burner 5 built into the line. Fuel is fed into the burner 5 installed in the line via a line 2 and gas containing oxygen via a line 3. Hydrogen, substance-containing gas is introduced into the burner built into the line via a line 4. A temperature of about 150 ° C having the exhaust gases are heated-.and at a temperature of 225 ° C then via a line 6 through a reducing catalyst in a reactor ¹ J routed to built-in into the line burner. 5 All of the hydrogen-containing gas required for the reduction is fed to the process via line 4. The treated gases flow out of the reactor 7 through a line 8 and are cooled in two stages, namely in a heat exchanger 9 and in a downstream cooling tower 10. In the second cooling stage, namely in the cooling tower, the gases are cooled in countercurrent with cold water fed into the cooling tower through line 11. The cooling water and the water formed by condensation of the steam contained in the exhaust gases flow out of the cooling tower through line 12. The amount of water leaving the cooling tower via line 12 can optionally be completely or partially cooled and then returned to the cooling tower (this return is not shown in Pig. I). The gases leave the cooling tower at a temperature of about ¹ K) ⁰ C through line 15 and are introduced into an absorption column 14, which contains a liquid and regenerable absorbent for hydrogen sulfide. The unabsorbed components of the exhaust gases, which consist mainly of carbon dioxide and nitrogen, are passed through a line.

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derived. To get the last traces of hydrocarbons and To convert hydrogen sulfide, the remaining gas is heated in a heat exchanger 16 and in an incinerator 17 burned at 400 ° C before it passed through line l8 into the chimney is derived. . \

An absorbent enriched with hydrogen sulfide is passed through line 19 for regeneration into a desorption column 21 directed. The regenerated absorbent is to the absorption column l4 via line, 2> returned and the released

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relatively small amounts / hydrogen sulfide containing carbon dioxide withdrawn via line 25 in a Claus plant.

In the desorption column 21, the absorbent is increased at Temperatures regenerated by heating with steam fed in via line 22. Because the regenerated absorbent at low Temperatures is used, it becomes one. Heat exchange with the absorbent to be regenerated in the heat exchanger 20 and then subjected to cooling in a cooler 24. The hydrogen sulphide is withdrawn through line 25 Gas is cooled in a cooler 26 and thereby the all entrained water vapor condenses. The condensed water is returned to the desorption column via line 27. ·. . . . .

In Figs. 2 and 3, the same parts of the two are in the line built-in burner with the same reference numerals. Accordingly, the reference number 50 denotes the heat-resistant lining

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tion of the burner built into the line, the reference number 51 the inlet for the exhaust gases in the burner built into the line and the reference number 56 the outlet for the exhaust gases from the burner. Reference number 52 denotes the fuel supply line to the burner and reference number 53 denotes ^the supply line for the oxygen-containing gas to the burner. The reference numerals 54a and 54b denote the various feed lines for the hydrogen-containing gas in the burner built into the line, and the reference numerals 55a and 55b denote the nozzles for introducing the hydrogen containing gas into the burner built into the line. The reference number 58 refers to the mixing chamber of the burner built into the line. ■

, In Fig. 2 a burner built into the pipe is shown, which contains a conventional burner. The hydrogen containing Gas is either in the burner built into the pipe via one attached at an angle close to the mouth of the torch neck Nozzle (i.e. nozzle 54a) or through a nozzle placed perpendicular to the walls of the mixing chamber near the mouth of the torch neck (i.e., nozzle 54b). It should be noted, however, that the introduction of the hydrogen-containing gas by means of a or several nozzles can be carried out, which at a large number of from locations near the neck of the torch, either perpendicularly or at an angle to the walls of the built-in torch are. The places shown in this figure are only two νση many possibilities.

In Fig. 3, a burner built into the line is shown,

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which contains a high-performance burner. The one containing hydrogen Gas is fed into the burner built into the line either via feed line 5 ^ -a. and nozzle 55a into the combustion chamber. · of the high-performance burner or via the supply line 5 ^ b and the nozzle 55t> * die are arranged in the vicinity of the mouth of the combustion chamber, initiated.

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Claims (1)

-.15 - ■ .., Pat tans ρ rüche 1. A method for reducing the overall sulfur content of Claus exhaust gases, in which the aforementioned exhaust gases containing hydrogen sulphide and sulfur dioxide are passed above 175 ° C together with a gas containing free hydrogen and / or carbon monoxide over a catalyst which contains a sulphidated metal of VI. and / or VIII. group on an inorganic oxide carrier, in which the treated exhaust gases are passed through a conventional, liquid, regenerable absorbent for hydrogen sulfide, in which the unabsorbed part of the exhaust gases is released into the atmosphere, if necessary after combustion in which the absorbent loaded with hydrogen sulfide is regenerated in the usual way and used for a new absorption, and in which ⁴ the hydrogen-rich gas released during the regeneration is usually fed to a Claus process, according to patent ... (patent application P 21 35 522.6), thereby geke η η ζ eich η et that the Claus exhaust gases on. Temperatures above 175 ° C are heated by passing them through a burner built into the line, in which a fuel is burned with an oxygen-containing gas and into which the hydrogen-containing gas required for the subsequent reduction of the sulfur dioxide to hydrogen sulfide is fed directly will. . ' 2. The method according to claim 1, characterized in that the Hydrogen-containing gas at one point in the line built-in burner at which the temperature of the Gases in the burner built into the pipe at least 500 C amounts to. J5. Method according to claim 1 or 2, characterized in that that the introduction of the hydrogen-containing gas into the burner built into the line is carried out by making it distributed around the flame formed by the combustion of the fuel and the oxygen-containing gas. * i. Method according to claims 1 to 3 *, characterized in that that the hydrogen-containing gas is distributed around the flame by means of one or more nozzles. 5. The method according to claim 1 to 4, characterized in that that the Claus exhaust gases in the burner built into the pipe be introduced at a point at which the combustion of the fuel and the oxygen-containing gas is practically complete is. 6. The method according to claim 1 to 5 *, characterized in that that the molar ratio of the burners built into the line fed in Claus exhaust gases to the combustion of the fuel and the oxygen-containing gas in the combustion gas of 4: 1 to -50 formed in the burner built into the line : 1 concerns. ' 0 9 8 2 6 / Q 7 9 8