DE2264878A1 - Sulphur dioxide contg gases prepn - at temp for conversion to trioxide, by burning sulphur stoichiometrically and removing excess heat - Google Patents

Abstract

The heat of combustion in excess of the starting temp. is dissipated partly in the combustion zone and partly in the directly following zone. The S is burnt in stoichiometric proportions or in the stoichiometric proportions for conversion to SO3. Advantages are that a masonry-clad combustion furnace is unnecessary. The heat-exchanger surfaces need not be very large, due to the high gas temps. Thus the appts. is compact, and so heat is economized.

Description

FRIEDRICH UHDE GMBH
DORTMUND

File number: 10005 α

Method and device for the production of SO - containing Gases

The invention relates to a method and a device for generating SO_-containing gases at a temperature corresponding to the light-off temperature of the subsequent catalytic conversion to SO ₃ . SO -containing gases are usually obtained by burning sulfur with air.

In such S0 "generation processes, it is necessary to remove a substantial part of the heat of combustion from the gas, since the following catalytic conversion of the S0 _? -Share of S0 "expediently begins at the respective light-off temperature of the catalyst mass. The light-off temperature is usually UOO - 450 ° C.

It is known to carry out the S0_ generation in such a way that the The sulfur used and the air are ignited in a burner and the flame then in a brick-lined incinerator is and for economic industrial plant sizes a diameter of 3 m and more and a length of 10 m and has more, comes to full training. This incinerator is usually followed by a waste heat boiler for generating steam, in which the hot gas up to a temperature below 450 C ■ is cooled.

In order to minimize heat losses in conventional incinerators To obtain them, they are on the one hand with a thick-walled insulating lining and on the other hand with an additional one Provide external insulation around the steel jacket. As a result of the large size of the incinerator, considerable investment is required necessary. ·

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The combustion is usually at such an excess of air, the -at λ approximately 2.3 is carried out, that the 'combustion gases' leave the combustion furnace comparable with a temperature below 1,000 ⁰ C. In the waste heat boiler which is connected downstream of the combustion furnace , a maximum temperature difference of 1,000 - U50 = 5 50 ⁰ C. is then available for steam generation. As a result of this small temperature difference, considerable heat exchanger surfaces are required. De "r". A high excess of air results from the addition of the reaction oxygen in the form of air for the subsequent S0 ₃ reaction and the addition of more air to lower the gas temperature in the incinerator.

After OS 1/948 745 the temperature of the leaving the incinerator gases attempting to about 1,600 ⁰ C to raise by substoichiometric combustion of sulfur with air as SauerstofftrSger. The gases containing SO «and sulfur vapor are cooled ^{to approx. 750 ° C. in a waste heat boiler after the incineration furnace.} Then • if more air is added, the remaining sulfur vapor is burned with an increase in temperature. In a subsequent mixing device, the amount of air required for the formation of S0_ is added and the temperature is thereby lowered to 450 C. According to this publication, only the heat of combustion of part of the sulfur used is partially used in the waste heat boiler.

According to OS 1 667 421, sulfur-containing substances are used to produce sulfur dioxide Raw materials with an excess air coefficient of

λ = 1.0 to 1.6 burned and in the stream of combustion gases additional amounts of air introduced so that the sulfur dioxide-oxygen ratio required for the oxidation to sulfur trioxide is achieved. The heat of combustion from the first oxidation stage is dissipated in a waste heat boiler located spatially downstream of the combustion chamber.

From OS 2 210 77 3 is known sulfur under pressure and stoichiometric to burn. The mixture requiring the combustion zone Secondary air is added immediately. This measure will make that

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high temperature level of combustion lowers without being optimally used to have become. The combustion chamber has a thick-walled outer wall and a heat exchanger connects to the combustion chamber outlet. · *

In summary, it can be seen that in known processes with over-stoichiometric combustion, i.e. Oj excess, the combustion gases enter the waste heat boiler at a temperature of less than 1000 C and, with below-stoichiometric combustion, unburned sulfur flows through the waste heat boiler and the available part of its heat of combustion not used to generate steam, but to heat the remaining combustion air supplied. Which in the generation of S0 _? Combustion heat arising from the combustion of all the sulfur used with an oxygen-containing gas cannot be obtained by means of known processes at an optimal temperature difference, or the combustion heat of the residual sulfur amount remaining in the case of substoichiometric combustion cannot be used for steam generation.

It has been found that these disadvantages can be avoided if the process for generating SOj-containing gases with an _{oxygen content required for the catalytic conversion to SO 0} and at a temperature corresponding to the start temperature of the catalytic conversion to SO _{3 is} carried out in such a way that all of the _{sulfur required to generate S0 2 is} stoichiometrically or near-stoichiometrically for the subsequent catalytic conversion, to SO ^ and under a pressure of at least 3 atmospheres, and the removal of that amount of heat from combustion that is above the light-off temperature, in the area of combustion and partly in the immediately following Area takes place.

Highly oxygenated gases include those with an oxygen content of more than 50% and a nitrogen content of less than ■ 50% understand. The nitrogen can also be replaced by another inert combustion gas.

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A device is used to carry out the method according to the invention, which is characterized by an elongated pressure vessel, in which a burner device is arranged on an end wall and in which the flame and the outflowing hot gases from a essentially cylindrical tube wall are surrounded as a heat exchanger, wherein the tubes are arranged longitudinally and tightly connected to one another.

In order to be able to reduce the high flame and gas temperature quickly, is According to a further embodiment, it is expedient if the tubes of the heat exchanger move from the coolant in the direction of flow of the flame and the hot gases are flowed through.

The advantages achieved with the invention are in particular: that the brick-lined incinerator is not needed .. As a result The high gas temperatures result in improved heat transfer values, which means that the heat exchange surfaces are kept small can. This makes the sulfur incineration plant more compact. The stoichiometric mode of operation to SO- provides more available waste heat, since no ballast oxygen has to be heated up. Except for minor ones There is less heat loss on the foundation and less space is required. Furthermore, this method can be used for vertical ' Installation of the incineration plant.

Since the process is operated at a pressure above 3 atmospheres, better heat transfer figures can be obtained for heat dissipation achieve and on the other hand there is a reduction in the dimensions of the apparatus.

Surprisingly, it turns out to be a further advantage that the NO content of the combustion gases is in the same ppm range as in conventional processes, despite the high combustion temperature. However, since the amount of gas generated is less due to the lack of atmospheric nitrogen and due to the combustion at λ of approximately 1, the

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effective N0 kenge also lower. The rapid cooling of the Combustion gases "prevent the establishment of equilibrium prematurely the NO - parliamentary group, '' "**

The combustion of water and oxygen under a pressure of at least 3 atmospheres, also has the surprising effect, that the PeaktionsfIcirama has a reduced flame volume 'V and thereby the combustion chamber volume taking into account the permissible Warruestromdichten can be kept small.

In general, it is useful to carry out the process according to the invention to be carried out in such a way that all of the sulfur to be burned and the oxygen or the gases with a high concentration of oxygen are removed from the burner are fed. The combustion should be practically stoichiometric led, d. H. with the lowest possible for technical reasons Excess oxygen. " The flame in front of the burner is surrounded by a combustion chamber, which is formed by heat exchanger tubes is formed through which the heat transfer medium, usually feed water or evaporating water, flows. The heat dissipation takes place directly to the heat transfer medium. - · The SOrj-containing gases leave with a temperature of "approx. 450 C the combustion and heat exchanger equipment.

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Claims (3)

10005 claims 1. Method for producing SO -containing rabbits with a temperature corresponding to the light-off temperature of the following catalytic conversion to S0_, with the SO containing O Z Gases by burning sulfur with oxygen or strong ' Oxygen-containing gases are formed, characterized in that all of the sulfur required for S0 "generation is stoichiometric or near stoichiometric for the following catalytic conversion to SO “and under a pressure of at least 3 atm is burned and the removal of that amount of combustion heat that is above the light-off temperature is partly in The area of combustion and partly in the directly adjoining area takes place. 2. Device for performing the method according to claim 1, characterized in that the device consists of an elongated Pressure vessel exists, the burner device on an end wall is arranged and the flame and the outflowing hot gases from a substantially cylindrical Pohrwand as Heat exchangers are surrounded, the tubes Kings are arranged and tightly connected to one another. 3. Apparatus according to claim 2, characterized in that the tubes of the heat exchanger from the coolant in the direction of flow the flame and the hot gases flow through. EAD GRiGiNAL 509820/0880