DE1028097B - Process for the production of sulfur dioxide from sulphates - Google Patents

Description

GERMAN

The production of sulfur dioxide by the decomposition of sulfates has already been described several times been. In the technical design of the reductive decomposition, however, there is the risk that the Sulphates cannot be completely reduced when some of the reducing agent is in the furnace atmosphere is lost through combustion. If, on the other hand, excess reducing agent is added, then im Residue sulphides remain, which would interfere with the further processing of this residue. It there is also the fact that undesirable reduction products arise, primarily sulfur vapors, which are burned must be used before the sulfur dioxide can be used in the manufacture of sulfuric acid can.

Methods and apparatus have been described for overcoming these difficulties should be. You can z. B. use an internally heated rotary kiln in which at different Make air is blown in. At the same time, different zones are created inside the rotary kiln formed, which differ both in terms of temperature and in terms of the composition of Differentiate between the gas atmosphere and the reaction material. In the initial zone it is at 700 to 800 ° C Air blown in, which causes the sulfur vapors and escaping from the neighboring hotter zone other undesired reduction products are burned without the sulphates at this temperature slammed reducing coke is attacked. In this zone, the reaction mixture is at temperatures incompletely reduced up to 1100 ° C with insufficient solid or gaseous reducing agents. The previously unreduced portions are in the hottest end zone with gaseous reducing agents implemented. This method, too, is still effective, especially when it is carried out on an industrial scale some flaws. The desired zone setting can be in the gas atmosphere, but not in the Carry out reaction material. The blowing of air into the hotter parts of the rotary kiln also hits technical difficulties. The high temperatures required lead to frequent malfunctions, caused by the formation of rings and deposits as well as damage to the masonry. This is special the case when mixtures are to be fired whose melting and sintering points are close together lie.

Finally, processes have already been described in which sulfur dioxide is obtained by roasting a mixture of calcium sulphate, rock phosphate, silica and fuel on a sintering apparatus using the induced draft process and by roasting granules made from heavy metal sulphates
of sulfur dioxide from sulfates

Applicant:

Paint factories Bayer Aktiengesellschaft, ίο Leverkusen-Bayerwerk

Dr. Hans Zirngibl, Duisburg,
has been named as the inventor

oxides, fuel and binding agent on a traveling grate.

It has been found that the difficulties described above can be avoided and one can be flawless Decomposition products are obtained when the decomposition is carried out on a sintering belt, which is equipped with a hood heater and allows heating in three zones, with the Atmosphere in the coldest zone is kept weakly oxidizing. The exhaust gases from the hottest end zone and the neighboring, less hot central zone, provided they are not required for temperature control and are therefore rolled back, optionally with the addition of air and optionally with additional Heating led to a colder zone. The reduction takes place mainly in the central zone, which contains a stoichiometric deficit of reducing agent. The reaction mixture is in the Initial zone to 500 to 800 ° C, in the middle to 900 to 1200 ° C and in the end zone to Sintering heated. In the middle zone, the atmosphere is increased when reducing coal is used kept indifferent and reducing in the end zone. But it can also reduce gas in both zones to be worked.

The process is shown schematically in Fig. 1. The reaction material is first granulated in the granulating device α and predried in the bunker b . It now reaches the sintering belt d, which continuously transports the material into the individual heating zones of the hood heating system. In the heater c , the fuel, z. B. oil, in the direction of the horizontal arrow on the fan I supplied the combustion air. In the initial

709 tS0 / 3SO

zone I, the reaction mixture is preheated to 500 to 800 ° C. The atmosphere is kept slightly oxidizing by the addition of air, but coal is not attacked at the temperatures prevailing in this zone. Therefore, all undesirable reduction products, such as. B. sulfur vapors contained in the gases exiting at h from the middle zone II and entering the starting zone via the blower ο at e

in the high heat exchange speed and in the good heat utilization with a low heat gradient. The proposed method of operation ensures that the production gas from undesired Admixtures is free. The dust content of the production gases is also considerably lower than that of the rotary kiln process. The inventive method allows errors to be recognized immediately, the z. B. in an incorrect raw meal setting, incorrectly measured

Sulfur dioxide are burned. Possibly ion quantities of reducing agents or incorrect fermentation the exhaust gases exist before entering the initial position of the gas atmosphere. As a result of

Using the endless sintering belt, the operation cannot be carried out by melting or sintering the Reaction goods are brought to a standstill. There

zone additionally heated. That at i via the fan η
Outflowing production gas is therefore after the usual dedusting without further cleaning for the
Fabrication of sulfuric acid after the contact 15 the process an exact setting of the temperature process can be used. such mixtures can also be fired

The reduction takes place mainly in the middle zone, whose sintering and melting points are close to one-zone at a temperature of 900 to 1200 ° C instead. other lie.

There is a stoichiometric deficit in this zone

With the decomposition of calcium sulphate under equal

in front of reducing agents. If the formation of cement clinker takes place here, it is z. B. not

finding reduction by solid reducing agents, such as. B. coal, the atmosphere becomes indifferent held. However, it is also possible to work with gaseous reducing agents.

necessary to make the final composition of the clinker dependent on the type of furnace management, like it has been the case so far. On the sintering belt, which is equipped with a hood heating, you can at the same time

The final reduction takes place in the last, hottest 25 complete desulfurization. B. aluminate and ferrari cement and is heated. The dicalcium silicate-containing clinker required for temperature control, which is based on the alumina fraction of the bar flowing off at k via the fan m.

Exhaust gases are circulated back into zone III at g. In connection with the simultaneous profit

other portion is under additional heating at 30 for drying of sulfuric acid and Portland cements is performed including the middle zone. It has been claimed that special cements, as indicated above, are also used in the desulphurisation process in which the exhaust gases from the rotary kiln can be preserved. In practice, the middle and end zones are removed together. However, this has not been the case, as Mauer-The portion required for temperature control will prevent damage to the factory and excessive ring formation.

According to the process according to the invention, all technically important sulfates can be decomposed without interference, z. B. iron sulfate, magnesium sulfate, calcium sulfate and mixtures of calcium sulfate with clayey Materials that simultaneously obtain cements or clinker leachable on alumina, furthermore Aluminum sulfate, mixtures of aluminum sulfate, sodium sulfate and sodium sulfate bauxite as well as other

rolled back into these zones. The remaining portion is led into the initial zone, so that here too the entire Production gas must pass the oxidizing initial zone before removal, where the undesired Reduction products are eliminated.

The required heating and decomposition energy can be generated by coal dust, gas or oil combustion will.

It is particularly beneficial to use the energy entirely or
partly through the incineration of elemental sulphate mixtures. To produce sulfur, as it is known per se for the reduction of sulphates. The method used here is a complete combustion
of sulfur guaranteed. At the same time one finds

example 1

78 parts of anhydrite with 91% CaSO ₄ are included in the composition with 15.2 parts of a slate

Concentration of the production gases in sulfur 50 60.0% SiO ₂ , 20.0% AI2O3 / T1O, 6.5% Fe ₂ O ₈ 3.5% dioxide. This is mixed for further processing into alkalis and 5.5 parts of coke (81% C), especially up to sulfuric acid after the contact process
favorable, as the apparatus dimensions are kept smaller due to the higher sulfur dioxide content
than with dilute gases.

Occasionally it is advantageous to use mixed firing, which consists of working in the middle Zones to the reaction material apart from the reducing carbon, further combustible carbon-containing substances

added that some of the necessary energy 60 when filling the granules at the same time fine-grained deliver. or dust-fine clinker entered.

A major advantage of the process is that the product passes through the first hood and is un-

to see that the reaction conditions in this through the exhaust gases of the second zone to about have the individual zones set exactly. Preheated without 600 ° C. To set the desired Difficulty can be in each zone any desired 65 oxygen content of 1 to 2% is in this hood Temperature with a margin of error of about 10 ° C, the necessary amount of air is pressed in. Afterward can be set. The gas composition can also be used under the second hood through the gases and gas pressure as well as the residence times of the solid from the last zone and additional heating with oil phase to be changed. Further advantages are on fire at 1000 to 1100 ° C in an indifferent cedar good distribution of the gas in the material filling, 70 maintained gas atmosphere and finally under the

ground to cement fineness and with about 10 to 12% water in a granulating plate in the usual way Way deformed. To protect the grate bars, the sintering tape is initially 3 to 5 cm high with finished fired Clinker is covered and the granules are layered 50 cm high on top. To protect against heat loss and as a seal against the heating hoods attached over the sintering belt, on both sides

Claims (2)

last hood heated to 1400 ° C by oil flames in a slightly reducing atmosphere. The gas atmosphere under the hoods is adjusted by regulating the oil and combustion air. The combustion air is previously pressed through the hot clinker on the last belt section and heated in this way while cooling the clinker at the same time. The clinker is sintered and practically sulfur-free; plaster of paris is added to it as usual and ground to cement. The SO2-containing gases that leave the furnace and have a temperature of around 150 to 200 ° C are cleaned of dust, mixed with air in a known manner and processed via contacts on sulfuric acid. The output of the sintering plant is 7.5 t / m2 of usable sintering area. EXAMPLE 2 Iron sulphate monohydrate, mixed with coke, is hot granulated with a concentrated iron sulphate solution and decomposed on the sintering belt with hood heating, similar to that described in Example 1. However, the exhaust gases from the end zone are removed together with the exhaust gases from the middle zones, as can be seen from FIG. 2. The molar ratio S O4: C is 2: 1. In the preheating zone the temperature is kept at 500 ° C, in the second at 900 ° C and in the last at 1100 ° C. The output is about 6 tpd / m2 of usable sintering area at a belt speed of 15 cm / min and a layer height of 20 cm. Example 3 A mixture of aluminum sulfate-sodium sulfate-coke in the molar ratio aluminum sulfate to sodium sulfate =! : 1 and SO4: C = 1.6: 1 are granulated and fired in the same way as described in Example 1. In the preheating zone, the temperature is set to 500 ° C, in the middle to 1000 to 1100 ° C and at the end to 1200 ° C. The result is sodium aluminate, which contains less than 0.1% sulfur. P Λ TENT Λ X SlMiC C H E: 1. Process for the production of sulfur dioxide by the reductive decomposition of sulfates on a sintering belt, characterized in that the granulated and dried reaction material decomposed on a sinter belt, which is provided with a hood heater, which is a heating Allowed in three zones, the atmosphere of the coldest zone being weakly oxidizing is held and the exhaust gases of the hottest end zone and the neighboring, less hot Central zone, if they are not rolled back for temperature control, if necessary under additional heating and possibly with the addition of air into a colder zone furthermore, a temperature is maintained in the coldest zone at which the in The sulfur compounds contained in the exhaust gases burn to sulfur dioxide and coal still is not attacked, and the reduction takes place mainly in the central zone, the one Contains stoichiometric deficiency of reducing agent and the final reduction in the hottest Zone is effected by gaseous reducing agents. 2. The method according to claim 1, characterized in that the reaction material in the initial zone to temperatures between 500 and 800 ° C, in the middle to between 900 and 1200 ° C lying temperatures, is heated in the end zone until sintering. Considered publications:
German Patent No. 682,261;
U.S. Patent No. 2,202,414. 1 sheet of drawings © 709 960/390 4.58