WO2001030691A1

WO2001030691A1 - Method for incinerating sour water stripper gas

Info

Publication number: WO2001030691A1
Application number: PCT/EP2000/010575
Authority: WO
Inventors: Edwin Kniep; Rainer Kalthoff; Michael Bayertz; Christoph Sievering; Detlef Gorka
Original assignee: Ruhr Oel Gmbh
Priority date: 1999-10-28
Filing date: 2000-10-27
Publication date: 2001-05-03
Also published as: AU1276101A; DE19951909A1; DE19951909C2

Abstract

The invention relates to a method for incinerating sour water stripper gas whereby incineration occurs in a combustion chamber provided with at least one burner and an oxygen-containing gas feed. At least one of the gas flows and/or partial gas flows and/or gas flows of gas mixtures of two or more gases are pre-warmed prior to combustion. The invention also relates to a device for carrying out said method containing at least one burner and/or a burner muffle, whereby means for heating the gas are provided for at least one of the gas supply lines.

Description

Process for the combustion of acid water stripping gas

The invention relates to a method for the combustion of acid water stripping gas, the combustion taking place in a combustion chamber equipped with a burner with the supply of an oxygen-containing gas. The invention further relates to an apparatus for performing the method.

Fossil fuels such as natural gas, coal, oil sands, oil shale and petroleum contain organic and inorganic sulfur compounds that are produced as gaseous, sulfur-containing products when processed. It is necessary to remove these sulfur compounds or to convert them into harmless sulfur compounds. Desulphurization takes place with the help of gaseous hydrogen (H ₂ ). The organic sulfur compounds are converted into hydrogen sulfide. The gases containing hydrogen sulfide originating from such sources are separated from the hydrocarbons still present in a gas cleaning installation, a so-called "amine treater". The gas containing hydrogen sulfide (also called acid gas or Claus gas) coming from the amine scrubbers can contain up to 90% by volume of hydrogen sulfide.

Since numerous refinery gases and liquids come into contact with water and / or steam during their treatment, contaminated water, which is referred to as "acid water", is another waste product of the oil refineries. The "acidic water" contains, among other things, ammonia and hydrogen sulfide in dissolved form. When this contaminated water is stripped, a gas mixture (the acid water stripper gas = SWS gas) is obtained which contains ammonia and hydrogen sulfide.

A process is used to remove the hydrogen sulfide, in which the hydrogen sulfide is converted into elemental sulfur. The most frequently used direct conversion process is the Claus process, which was developed in 1883. This process relies on a dry one waited Claus procedure. This process is based on a dry oxidation process. The various process variants developed are based on the same basic chemical reactions, using thermal and catalytic reactors.

The thermal reactor consists of a combustion chamber with a burner, a waste heat boiler. The catalytic reaction part is carried out in two or three stages. The individual stages each have a heater, a catalyst bed and a sulfur condenser.

The main chemical reactions that take place in the combustion chamber and in the catalytic reactors are listed below:

1. 6 H ₂ S + 3 O ₂ 2 SO ₂ + 4 H ₂ S + 2 H ₂ O 2. 2 SO ₂ + 4 H ₂ S 6 S + 4 H, 0

Total: 6 H ₂ S + 3 O ₂ → 6 S + 6 H ₂ O

The actual Claus reaction, in which elemental sulfur and water vapor are formed, is reaction 2. Here, the sulfur dioxide produced from the partial combustion of hydrogen sulfide reacts with the remaining hydrogen sulfide. Elemental sulfur and water are also formed in the combustion chamber by thermal decomposition of hydrogen sulfide.

Other accompanying gases contained in sour gas and SWS gas, such as hydrogen, methane, higher hydrocarbons, ammonia, water vapor, carbon dioxide, react in a variety of side reactions according to their concentrations. For gases which essentially only contain hydrogen sulfide, a method is used in which a part of the amount of hydrogen sulfide is burned by the burner by means of combustion air to sulfur dioxide at a temperature of 900 to 1300 ° C. The remaining hydrogen sulfide is converted at temperatures between 180 ° C and 400 ° C in the catalytic reactors with the sulfur dioxide formed from the combustion to elemental sulfur and water. The reaction is optimal when the hydrogen sulfide / sulfur dioxide ratio is 2: 1.

o The elemental sulfur formed in the combustion chamber is separated in the waste heat boiler after the process gas has cooled. Before entering the subsequent catalytic reactors, the process gas is adjusted to the required reaction temperatures of the catalytic stages on the one hand by appropriate switching of the sulfur condenser or by upstream heaters. The 5 sulfur formed by the Claus reaction is separated in sulfur condensers.

Since the feed gases contain different hydrogen sulfide concentrations, two main variants can be distinguished in the combustion process: the main flow operation for hydrogen sulfide concentrations greater than 50 vol.% And the secondary flow operation for hydrogen sulfide concentrations between 30 and 50 vol.%.

During main power operation, the entire amount of hydrogen sulfide is partially burned with the combustion air in the combustion chamber. Due to the thermal splitting of the hydrogen sulfide in the combustion chamber, a large proportion of the sulfur is already separated in the waste heat boiler of the thermal stage. In subsequent catalytic stages, the hydrogen sulfide is converted further to sulfur. The exhaust gas from the fine cleaning stage is led to the conversion of H ₂ S to SO ₂ via thermal afterburning.

BE The gas flow is split in the secondary flow mode since the hydrogen sulfide gas has only a low calorific value. Part of the hydrogen sulfide gas is burned with the combustion air in the combustion chamber and the sulfur dioxide gas that is produced is mixed with the remaining hydrogen sulfide gas and converted into elemental sulfur and water in the reactor. The catalytic part is constructed analogously to the main current operation.

If the hydrogen sulfide concentration of the feed gases is less than 30% by volume, the bypass operation can no longer be used due to the low calorific value. In addition, the bypass operation requires an ammonia-free feed gas, since otherwise the catalysts would be contaminated with ammonium salts.

When burning acid water stripping gas, which may contain up to 50% ammonia, the acid water stripping gas must be burned separately from the acid gas (H ₂ S gas = Claus gas) in the combustion chamber in order to cause thermal decomposition of NH ₃ by higher reaction temperatures according to the following equation to ensure: 2 NH ₃ + 3/2 O ₂ → N ₂ + 3 H ₂ O

In order to be able to burn larger quantities of gases containing hydrogen sulfide, the combustion air can be partially or completely replaced by oxygen. By using oxygen, the proportion of inert gas is reduced or eliminated entirely. With this method, the throughput of acid water stripping gas and Claus gas can be increased. In addition, low-hydrogen sulfide feed gases with a low calorific value and high ammonia content can also be processed in a mainstream reactor.

BESTATIGUNGSKOPIE DE 197 18 261 A1 describes how the throughput and the degree of conversion of hydrogen sulfide to elemental sulfur can be improved. In this method, oxygen or oxygen-containing gas is blown into the combustion chamber at high speed, as a result of which the mixture between the oxygen, the combustion air and the hydrogen sulfide-containing process gas is increased due to the high turbulence. In this process, oxygen is not only used as an oxidizing agent, but also to increase the mixing energy. By increasing the mixing energy, the combustion density and thus the throughput of hydrogen sulfide can be increased. The use of oxygen has a positive effect on the thermal cracking and complete combustion of higher hydrocarbons and ammonia, whereby a minimum temperature of 1,350 ° C is maintained, especially for complete ammonia combustion (see also Ullmann's Encyclopedia, 6 ^th ed. 1999, The Lurgi Multipurpose Claus-Oxygen Burner).

A typical incinerator is the Lurgi oxygen Claus burner. The Claus gas and the ammonia-containing acid water stripping gas are processed in this burner via separate burner muffles. The sour water stripper gas is burned with air in a central burner muffle. The Claus gas is burned with oxygen and air as the oxidation medium with several double-concentric individual burners, which are arranged around the burner muffle. A single burner consists of a central oxygen nozzle, a concentric Claus gas nozzle and a double-concentric air nozzle. This arrangement creates individual oxygen / hydrogen sulfide flames, which are enveloped by colder air / hydrogen sulfide flames. This allows the temperature in the combustion chamber to be controlled.

The disadvantages of the combustion processes of the prior art result from the fact that the central burner muffle contributes to the complete destruction of ammonia

CONFIRMATION COPY Excess air (eg SWS gas: air = 1: 3) must be operated in order to completely decompose ammonia. However, this excess of air contradicts the process control with regard to the Claus reaction, since the increased air supply results in an SO ₂ excess and the optimal H ₂ S / SO ₂ ratio of 2: 1 can no longer be achieved depending on the utilization of the system with acid gas. In addition, in the methods of the prior art, the sour gas / SWS gas ratio must be at least 3: 1 in order to ensure adequate cooling of the separate SWS gas burner muffle with the amount of air required to convert the sour gas. This results in a disadvantageous limitation of the capacity for processing SWS gas in the Claus plants. Another disadvantage of processes with additional O ₂ addition is the high cost of oxygen, as well as the then higher minimum load of the Clausaniage compared to pure air operation.

The technical object of the invention was therefore to increase the throughput in the combustion of SWS gas without increasing the minimum load of the Claus plant.

The technical problem is solved by a method for the combustion of acid water stripping gas, the combustion taking place in a combustion chamber equipped with at least one burner with the supply of an oxygen-containing gas, and wherein at least one of the gas flows and / or partial gas flows and / or gas flows of gas mixtures of two or more gases are preheated before combustion.

A burner in the sense of the invention can be understood to mean a single nozzle, a burner with two or more nozzles, an arrangement of burners, a burner ring and variations thereof.

BES In a preferred process, the acid water stripping gas is burned in a mixture with acid gas. In a particularly preferred process, the sour gas is also preheated.

In these processes, the ammonia with the oxygen-containing gas is completely burned to nitrogen and water. The hydrogen sulfide gas is reacted as follows. Part of the hydrogen sulfide reacts with the gas containing oxygen to form sulfur dioxide. The remaining hydrogen sulfide is reacted with the sulfur dioxide formed in a molecular ratio of 2: 1 to form elemental sulfur and water.

It was surprisingly found that the preheating of the feed gases leads to the thermal decomposition of ammonia even in the main combustion chamber even with the stoichiometric addition of air to the SWS gas, so that no ammonia breaks through to the Claus reactors. The increase in the combustion chamber temperature for the complete thermal decomposition of ammonia can be achieved simply by preheating one or more process gases. In the process according to the invention, no superstoichiometric amounts of air are required, since the thermal decomposition of NH ₃ above a minimum temperature no longer requires an excess of oxygen when burning SWS gas. The processing capacity of sour water stripping gas can be increased because the sour gas / SWS gas ratio is no longer limiting. The sour gas / SWS gas ratio can therefore now also be less than 3: 1. This increases the working window for sour water stripper gas processing. Another advantage results from the fact that preheating the feed gases is less expensive than feeding in O ₂ to increase the combustion chamber temperature.

In a preferred process, the combustion takes place at a temperature above 1300 ° C., particularly preferably at 1,350 to 1,500 ° C. The implementation Combustion in this temperature range ensures the complete decomposition of ammonia, whereby lower temperatures require longer dwell times.

In a further particularly preferred method, the temperature of the preheated gas or the preheated gas mixture is at least 200 ° C. With this method the combustion temperature can be increased to the required values. Precise control of the combustion temperature can be achieved through the specific preheating of the individual gas flows.

In a particularly preferred process, air, oxygen-enriched air or pure oxygen is used as the oxygen-containing gas. This is particularly advantageous because the combustion process can be additionally controlled via the concentration of oxygen in the oxygen-containing gas. For example, the combustion chamber temperature can be increased by adding an oxygen-containing gas if necessary above the temperature values achieved by preheating.

In a particularly preferred method, part of the sour water stripping gas is not preheated and burned with preheated air in a central burner muffle. The remaining part of the sour water stripper gas is mixed with the sour gas and preheated to over 200 ° C, whereby this preheated sour gas / sour water stripper gas mixture is fed into the individual burners arranged concentrically around the central burner muffle and burned together with air, whereby these are fed to the individual burners Air is also preheated to over 200 ° C. In addition, non-preheated oxygen gas can be fed into the individual burners.

BESTATIGUNGSKOPIE In a very particularly preferred method, the preheating is carried out using means selected from the group consisting of high-pressure steam, electric heaters, in-line burners and heat exchangers.

Furthermore, the technical problem is solved by means of a device for carrying out the method, the device containing at least one burner and / or a burner muffle, means for heating the gases being provided on at least one of the gas feed lines.

In a preferred embodiment, additional individual burners are arranged around the central burner muffle, which contain at least one nozzle for oxygen-containing gas and at least one nozzle for acid gas or an acid gas / acid water stripping gas mixture. This device also contains means for heating the gases on at least one of the gas feed lines.

In a particularly preferred embodiment, means for heating the gases are provided on all gas supply lines.

In a very particularly preferred device, the means for heating the gases are high-pressure steam heating means, electric heaters, in-line burners or heat exchangers.

The advantages of the device according to the invention are that the combustion temperature during the combustion of the ammonia-containing SWS gas can be increased to above 1300 ° C, preferably to 1350 to 1500 ° C, by preheating the supplied gases to over 200 ° C, for example by means of high pressure steam , The high combustion temperatures when using this preheating have a positive effect on the thermal cracking and complete combustion of ammonia.

BESTATIGUNGSKOPIE In the device according to the invention, the method described above for the combustion of acid water stripping gas can be carried out, the thermal decomposition of ammonia with oxygen already taking place completely with the stoichiometric addition of air to the SWS gas. The means for heating the feed gases enable the combustion chamber temperature to be increased for the complete thermal decomposition of ammonia. Due to the reduction in the amount of air required, an increase in the processing capacity of acid water stripping gas is achieved with the device according to the invention. The sour gas / SWS gas ratio in the combustion carried out in the device is no longer dependent on the amount of sour gas due to the preheating of the feed gases.

BESTATIGUNGSKOPIE Examples

The following examples are intended to illustrate the invention:

The process according to the invention is carried out in principle like that in the process described above in the Lurgi oxygen Claus burner. The modifications are explained as follows:

Part of the SWS gas is burned with air in a central burner muffle. This air flow, which is fed to the central burner muffle, is a mixture of preheated air and non-preheated air. The remaining part of the SWS gas is mixed with the sour gas and preheated to approx. 290 ° C. This preheated sour gas / SWS gas mixture is fed into the individual burners arranged concentrically around the central burner muffle and burned together with air, which is preheated to 285 ° C and also fed to the individual burners. In addition, non-preheated oxygen gas can also be supplied to the individual burners.

Table 1 lists the parameters of seven different modes of operation of the sour gas / SWS gas combustion method according to the invention. In each case, the sour gas / SWS gas mixture is preheated to 290 ° C and the air destined for the individual burners to 285 ° C. Columns A and B indicate which sour gas or SWS gas quantities are burned in total. Column C shows the amounts of the gas stream that carry a sour gas / SWS gas mixture. This mixture is preheated to 290 ° C. Column D shows the ammonia content of the sour gas / SWS gas mixture. Column E shows the amounts of the non-preheated SWS gas component that is burned separately from the sour gas in the central burner muffle. Column F shows the quantities of combustion air used. In some variants, pure oxygen is also added

B leads (column G). From column H the resulting temperatures of the Claus combustion chamber and from column I the quantities of the process gas before entering reactor 1 can be seen. Column J shows the respective sulfur yields.

BE T I

* [tato] = tons per day [t / d] SWS-Gas = sour water stripping gas

Claims

claims

1. A process for the combustion of acid water stripping gas, the combustion taking place in a combustion chamber equipped with at least one burner with the supply of an oxygen-containing gas and wherein at least one of the gas streams and / or partial gas streams and / or gas streams of gas mixtures of two or more gases prior to the combustion is preheated.

2. The method according to claim 1, characterized in that a mixture of acid water stripping gas and acid gas is burned.

3. The method according to claim 1 or 2, characterized in that the acid gas is preheated before combustion.

4. Process according to claims 1 to 3, characterized in that the combustion takes place at a temperature above 1300 ° C.

5. Process according to claims 1 to 4, characterized in that the combustion takes place at a temperature of 1350 ° C to 1500 ° C.

6. Process according to claims 1 to 5, characterized in that the temperature of the preheated gas or the gas mixture is at least 200 ° C.

7. The method according to claims 1 to 6, characterized in that air is used as oxygen-containing gas, air enriched with oxygen or pure oxygen.

BESTATIGUNGSKOPIE

8. The method according to claims 2 to 7, characterized in that a part of the acid water stripper gas is not preheated and is burned with preheated air in a central burner muffle and the

5 remaining part of the sour water stripper gas is mixed with the sour gas and preheated to over 200 ° C., this preheated sour gas / sour water stripper gas mixture being fed into the individual burners arranged concentrically around the central burner muffle and being burned together with air, whereby this Air supplied to individual burners is preheated to above 200 ° C.

9. The method according to claim 8, characterized in that oxygen gas is additionally fed into the individual burners.

15 10. The method according to claims 1 to 9, characterized in that the preheating is carried out with high pressure steam, with electric heaters, in-line bumpers or heat exchangers.

11. Device for performing the method according to claims 1 to 20 10, containing at least one burner and / or a burner muffle, characterized in that means for heating the gases are provided on at least one of the gas supply lines.

12. Device for performing the method according to claims 1 to 25 10, containing a burner with a central burner muffle, in the

Sauerwasserstrippergas and oxygen-containing gas is burned, single burners are arranged around the central burner muffle, which contain at least one nozzle for oxygen-containing gas and at least one nozzle for sour gas or a sour gas / Sauerwasserstrippergas- 30 mixture, characterized in that means for heating the

Gases are provided on at least one of the gas feed lines.

13. The apparatus according to claim 11 or 12, characterized in that means for heating the gases are provided on all gas supply lines.

14. Device according to claims 11 to 13, characterized in that the means for heating the gases are selected from the group of high pressure steam heating means, electric heaters, in-line burners and heat exchangers.

CONFIRMATION PIE