DE4344035A1 - Desulphurising sulphur-contg. crude gas charged with coke dust - Google Patents

Abstract

Desulphurising S-contg. crude gas charged with porous fine grain coke dust comprises: (a) mixing an O2-contg. gas with the crude gas depending on the H2S content at 150-300 deg C in vol. ratio of O2:H2S 1-10:1; (b) passing the gas-coke dust mixt. obtd. through a fly-stream reactor for 1-60 secs.; and (c) removing a S-charged coke dust from desulphurised gas mixt. in a dust filter.

Description

The invention relates to a method for desulfurizing sulfur term, especially H₂S-containing with porous, fine-grained coke dust loaded raw gas.

A sulfur-containing, in particular H₂S-containing raw gas falls for example in the gasification of brown coal in the fluidized bed. In this context, the high temperature comes as the gasification process tur-Winkler gasification, HTW gasification for short. The HTW Gasification generated raw gas with which, for example, a gas turbine be in addition to dust, it contains a number of environmental and turbines harmful trace substances such as B. H₂S, COS, NH₃, alkali halo genes and others that are separated or converted from the gas and around must be disposed of in an environmentally friendly manner. In addition to the trace substances the raw gas but also a coke-like dust, which is one very porous, fine-grained coke dust with a grain size is usually less than 0.1 mm and an ash content of 40-60 vol .-% has. The coke-like dust is either in one Water wash or before water wash at temperatures above the Water vapor dew point, for example with filters, in a dry way deposited. The core of gas cleaning is, however, the Ent sulphurization. Washing processes are known for this, according to which the raw gas with water and physical or chemical detergents Temperatures below the water vapor dew point is treated. The separated sulfur compounds, primarily H₂S, become Worked up sulfur or sulfuric acid.  

The known scrubbing processes for gas cleaning are technically complex and associated with not inconsiderable operating costs; also falls a waste water that must be treated additionally. That dusted off and desulfurized synthesis gas is particularly good for the operation of Combined power plants suitable where it is used to generate steam and electric current is used. In the combination power plants the cleaned gas burned in the combustion chamber of a gas turbine, the drives a generator as part of the power plant process and thereby generates part of the electrical current.

Of power plants in general and in particular of combined cycle power plants required that they respond to changes in load changes as quickly as possible can be fitted. For example, at a speed of The load change of such a power plant of 8% per minute must be in one Period of 5 minutes the gas to be made available for the gas turbine quantity between 60 and 100% based on full load can be changed. This is not easy with the known washing processes realizable. The maximum achievable rate of load change is primarily determined by the sluggishness of the washes. Also fall in the cooling of the gas caused by the washing under the Water vapor dew point considerable waste heat losses at a low temperature level that is no longer available for power generation stand. Such heat losses can affect the overall efficiency of a com lower binations power plant, being on the other hand in the same Dimensions that CO₂ emissions can increase.  

Hot gas cleaning processes are also known in which the ent sulfurization takes place at temperatures above the water vapor dew point. For this, metal oxides are used, which are mutually sulfurized and then regenerated again. These procedures have However, it cannot be implemented on an industrial scale, as there are no Sorbs ties are available that meet the requirements for real continuous operation fulfill.

From the disadvantages of the known methods and possibilities the task for the present invention, a method for Propose desulfurization of raw gas, especially for use is suitable in combination power plants. In particular, efforts are being made a:

• - increasing the efficiency of electricity generation
• - lower CO₂ emissions,
• - saving wastewater washing and treatment,
• - Saving the desulfurization scrubbing and the sulfur rim win,
• - Reduction of consumption of resources and operating cost and
• - Simplified management and higher load change speeds capabilities of the combined cycle power plant.

To solve the problem it is proposed that

• - The raw gas loaded with coke dust depending on the because H₂S content at temperatures between 100 and 300 ° C. an O₂-containing gas in the volume ratio between 1: 1 O₂: H₂S 10: 1 added,  
• - The gas-coke dust mixture thus obtained in a residence time between 1 and 60 seconds through an entrained flow reactor directs and
• - A sulfur-laden one in a downstream dust filter Coke dust is separated from the desulfurized gas mixture.

Depending on requirements, the separated coke dust can be reused or fed into a furnace and burned there.

The invention is based on the knowledge that the raw gas Desulphurize coal gasification with brown coal coke. In particular, can for desulphurization, use the coke dust that is already in the Raw gas is included. If the proportion of the coke contained in the raw gas dust is not sufficient, can ensure adequate desulfurization required amount of brown coal coke by admixing additional adsor needs, such as B. stove coke can be added. Desulfurization follows by partial oxidation of H₂S according to the following main reaction tion:

2 H₂S + O₂ = 2 S + 2 H₂O.

Process conditions for desulfurization are particularly favorable before when the HTW raw gas at a pressure of 25 bar and temperatures desulphurized between 160 and 260 ° C. The raw material to be desulfurized gas, which has an H₂S concentration of about 0.3 vol .-% up to 1 vol .-% oxygen admixed. Here H₂S is almost oxidized quantitatively and also the oxidation of COS takes place to more than 80% based on its original share. The one in the oxidation Sulfur that forms is deposited in the pores of the coke.  

Finally, in the desulfurized gas, H₂S contents of less than 5 ml / m³ i.N. and COS contents of less than 20 ml / m³ i.N. reached become. In contrast, the sulfur loading of the coke is up to 20 mass percent.

According to the invention, the raw gas of the HTW gasification is by partial oxi desulfurization before the gas is dedusted.

The invention is explained in more detail below using an exemplary embodiment. The figure shows, in a highly simplified and schematic representation, one possibility for carrying out the method. Pre-dried and crushed coal 1 is gasified together with air 2 in a HTW gasifier 3 . This produces a raw gas 4 with a temperature of approximately 900 ° C. In a heat exchanger 5 , the dust-laden raw gas 4 is cooled to temperatures above the water vapor dew point, for example to a temperature between 150 and 300 ° C. When the raw gas 5 is cooled, superheated steam 6 is obtained. The dust-laden raw gas 7 cooled to about 200 ° C. is mixed with an O₂-containing gas, for example air 8 . By admixing the O₂-containing gas 8 to the dust-laden cooled raw gas 7 , a ratio of O₂: H₂S between 2: 1 to 10: 1 is set in the gas mixture 9 . The gas mixture 9 is passed through an entrained flow reactor 10 , which in the simplest case consists of a pipeline. For example, at flow speeds of the gas in the order of 5 m / s results in a residence time of 1 s of the Gasge mixture 9 in the entrained flow reactor 10, a tube length of 5 m. Entrained-flow reactors with a lower gas velocity are used if the upper limit of the dwell time of 60 s provided according to the invention is reached.

In any case, in the entrained flow reactor 10, the sulfur contained in the gas mixture is separated in the pores of the coke-like dust which is carried along by the gas mixture 9 itself.

In the event that the amount of coke dust contained in the gas mixture 9 is not sufficient, it is provided to feed the entrained flow reactor 10 via a connection 11 to further adsorbents. This can be active coal or lignite coke obtained by coking on the stove, so-called stove coke.

The desulfurized crude gas 12 present at the outlet of the entrained-flow reactor is then passed through a dust filter 13 . A sulfur-laden coke dust 14 is produced in the dust filter 13 . The desulfurized and dedusted raw gas 15 can then be burned in a gas turbine (not shown). Similar things can happen with the sulfur-laden dust 14 , which can be fed to the furnace of a steam boiler (not shown), for example. It can also be fed to a sulfur or sulfuric acid production according to generally known processes.

A further cleaning or aftertreatment of the dedusted gas mixture 15 in front of the gas turbine is provided, for example by NH 3 removal, conversion and the like, or also a direct supply of the dedusted gas mixture 15 to the gas turbine and a NO _x reduction in the flue gas behind the gas turbine.

Using the following numerical example, the procedural Revenues explained again:

• - Rhenish lignite is turned into electricity in a combination power plant. The crushed and pre-dried lignite 1 is gasified with air 2 in the HTW gasifier 3 . The emerging from the HTW Verga ser 3 dust-laden raw gas 4 is cooled by indirect heat exchange 5 to a temperature of 200 ° C. The H₂S content of the cooled gas 7 is 0.1-0.2 vol .-% and the dust load is between 20 and 40 g dust / m³ iN The dust is a very porous, fine-grained coke dust with a grain size 0.1 mm and an ash content of 40 to 60 vol%. The dust-laden raw gas 7 is admixed with up to 2% by volume of air 8 and the gas mixture 9 thus held is passed through an entrained flow reactor 10 . The metering of the air 8 is adapted to the H₂S content of the gas 7 such that a volume ratio O₂: H₂S of about 2: 1 is maintained, provided that the H₂S content of the gas 7 is measured continuously and as a guide size is entered into a regulation.

In the entrained flow reactor 10 , the complete partial oxidation of the H₂S takes place, the sulfur formed separating out in the pores of the coke dust 14 . The sulfur-containing dust 14 is quantitatively separated in the closed dust filter 13 .

The desulfurized gas 15 is fed to the gas turbine (not shown) without further treatment stages.

Behind the waste heat boiler (not shown) of the gas turbine is followed by a NO _x removal from the raw gas using a known SCR process (Selective Catalytic Reduction). The sulfur-containing dust 14 is burned together with the carbon-containing HTW bottom product 16 in a steam generator (not shown) with a subsequent flue gas desulfurization (not shown).

Claims (5)

1. A process for desulfurizing sulfur-containing, in particular H₂S-containing raw gas loaded with porous, fine-grained coke dust, characterized in that

• - The raw gas, depending on the respective H₂S content at temperatures between 150 and 300 ° C, contains an O₂-containing gas in a volume ratio between 1: 1 O₂: H₂S 10: 1,
• - The gas-coke dust mixture thus obtained passes through a entrained flow reactor in a residence time between 1 and 60 s and
• - separates a sulfur-laden coke dust from the desulfurized gas mixture in a downstream dust filter.

2. The method according to claim 1, characterized in that one Raw gas depending on the respective load with porous, fine-grained coke dust and the respective H₂S content, others Adsorbents, such as. B. fine-grained hearth coke made of brown coal admixed. 3. The method according to claim 2, characterized in that one at an H₂S content of the raw gas between 0.1 to 0.2 vol .-% total dust load between 10 to 50 g / m³ i.N. sets. 4. The method according to claim 1, characterized in that one dust-laden raw gas up to 5 vol .-% air. 5. The method according to claim 1, characterized in that at Pressures in the range of 1 to 40 bar works.