DD202857A1 - PROCESS FOR PREPARING DEFILED SULFURIC ACID - Google Patents

Abstract

The invention relates to a process for producing verduennter sulfuric acid by absorption and oxidation of sulfur dioxide SO deep 2-containing gases. The aim of the invention is an improved environmentally friendly process for producing verduennter sulfuric acid from SO deep 2-containing exhaust gases with SO 2 deep levels to 3.0 vol .-%. The invention has for its object to avoid the previously required Apparatedimensionen unfavorable load ratios of volume flow gas to volume flow liquid. According to the invention, the object is achieved by reacting the SO 2-containing gas at elevated temperatures, preferably> 60 degrees C, and at pressures greater than atmospheric pressure, preferably> 0.98 MPa, with the absorption solution ,

Description

Process for the preparation of dilute sulfuric acid Field of application of the invention

The invention relates to a process for the preparation of dilute sulfuric acid by absorption of the sulfur dioxide SOp-containing gases in dilute metal salt solutions with simultaneous oxidation with air or oxygen.

The scope of the invention extends except for the production of dilute sulfuric acid for certain chemical processes also on the smoke and emission control.

Characteristic of the known technical solutions

At present, large amounts of gaseous sulfur compounds, mainly sulfur dioxide, are produced by various metallurgical and chemical processes and processes or by the combustion of sulfur-containing energy carriers.

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The steady increase in the accumulation of SO _p- containing gases requires increasingly, both for economic reasons and for reasons of environmental protection, a recovery of sulfur.

Numerous process descriptions are known from the literature to describe the SO ₂ work-up in an alkaline medium or a recycling of SO ₂ from SO-containing gases by absorption and oxidation of the SO in catalyst-containing dilute sulfuric acid. Thus, for example, according to WP 147 935 is known that from exhaust gases containing up to 2.0 vol .- $> SO ₂ , the sulfur dioxide can absorb almost completely, if this gas for a very long time with a dilute sulfuric acid, the until to 25 g Al ⁺⁺⁺ / 1 and as a catalyst up to 12 g Fe ⁺⁺⁺ / 1 may contain, contacted »The iron ions may also be present in divalent Porm, since in the apparatus itself an oxidation to Fe ⁺ " * "* he follows.

Since the method mentioned but in the gas to be processed, a 0_ molar ratio t SO ₂ £ 4 calls ,, can S0 ₂ ~ containing almost oxygen-free gases, as they are obtained, for example, in the decomposition of basic aluminum sulphate to produce aluminum oxide, only by adding large air or acid amounts are processed. "This leads to the generation of very large amounts of gas. If, on the other hand, one does not want to produce very dilute sulfuric acid from this, the quantities of absorption liquid must be kept small so that unfavorable loading conditions occur in the apparatuses used. Gas volume flow: liquid volume flow. Thus, for example, results in the thermal decomposition of basic aluminum sulfate according to WP 140 737th

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a ratio of gas volume flow to liquid volume flow (referred to the same unit of measurement i.N.) of> 700. ;

For economic and environmental reasons, a conversion of SO ₂ in the exhaust gas of> 95 % is desired, so that when using the absorption process according to WP 147 935 high residence times of the gas in the liquid are realized because of the too low reaction rate of the SOp. However, this leads to industrially difficult to implement and very expensive apparatus.

Object of the invention

The aim of the invention is an improved environmentally friendly process for the production of dilute sulfuric acid from SOg-containing exhaust gases.

Explanation of the essence of the invention

Based on the technical causes of the lack of the known technical solution of the invention, the object is based on the previously required device dimensions under unfavorable load conditions of

Volume flow gas to avoid volume flow liquid. According to the invention the object is achieved by the SOg-containing gas at elevated temperatures, preferably fis 60 ⁰ C, and at pressures greater than the atmospheric pressure, preferably 22 0.98 MPa, is reacted with the absorption solution. One liter of absorption solution, as used to prepare dilute sulfuric acid from oxygen-free, S0_-

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containing gases, d. In addition to aluminum and iron ions, it contains about 35 ··· 15Og of sulfuric acid and under normal conditions can dissolve a maximum of 30 g of sulfur dioxide until the saturation limit is reached.

We contacted flow gas to flow fluid> · JOO corresponding to a ratio a liter of absorption liquid with 700 liters Ci. N.) gas with 2.5 to 3.0% by volume, corresponding to 51.1 to 61.4 g of SO ₂ per unit of time, it can be seen that due to the solubility limit of a maximum of 30 g of S0 "only one Part of the sulfur dioxide can be absorbed. As a result, only 30 g S0 _? can be oxidized per unit of time under normal conditions a maximum of 49 ··· 59/5 of the leading sulfur dioxide can be converted «

Surprisingly, it has now been found that the solubility of sulfur dioxide in the absorption solution is only insignificantly influenced by its concentration of sulfuric acid. Accordingly, more than 30 g of SO ₂ could be absorbed in one liter of absorption liquid per unit of time, if sulfur dioxide is accelerated to sulfur trioxide accelerated and thus removed as SO ₀ from the system.

According to the invention, the required acceleration of the oxidation reaction was achieved by increasing the temperature, whereby the solubility of the sulfur dioxide, which greatly decreased with the temperature, could be compensated for by simultaneously increasing the system pressure. By simultaneously increasing the temperature and pressure, it is also below these unfavorable loading conditions for absorption processes From volumetric flow gas to volumetric flow liquid S ^ 700 has become possible, a desulfurization of exhaust gases with SO ₂ contents up to

Ä. Ä. Err 4M .Λ - »** üi η ft» w, k.

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3.0 VoI # - ^ make. Another decisive advantage of the solution according to the invention is that, due to the increased SOp conversion, much smaller device dimensions are required.

The invention will be further illustrated by the following examples.

example 1

In a suitable apparatus, at a temperature of 70 ⁰ C and different Apparatedrücken (measured above the liquid), a gas laden with sulfur dioxide at a speed (based on the free Waseherquerschnitt) of about 0.18 m / s passed through the liquid, the above

50 ... 80 g S0 _3free / l

40 ... 60 g Al ₂ O / 1

4.5 ... 5.5 g Fe ₂ O ₃ A as Fe ⁺⁺ and Fe ⁺⁺⁺

contains.

The residence time of the gas in the liquid is approx. 12.5 s. The liquid supply is approx.

3 2

0.89 nr / m · h. The load ratio gas ί liquid is set to 728 nr ^ / nr. At the various apparatus pressures, the following SOg contents in the gas were determined

Equipment overpressure

in kPA 0.0 49.0 147.1 245.2

S0 _o content (on)

in Vm ³ 73.64 71.89 74.23 73.64

SO ₂ content (off)

in g / m ³ '59.03 46.17 22.50 4.09

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Example 2

₁ liter of gas is passed through an apparatus at a temperature of 80 ^° C. and the other conditions described in Example 1, and the apparatus overpressure (measured over the liquid) is thereby changed. The following SO levels in the gas were determined «

Equipment overpressure

in kPa 0.0 49.0 147.1 245.2

S0 _o content (on)

in ^ g / m ⁵ 68.38 73.35 46.17 66.34

S0 _o content (off)

in ² g / m ³ 54.36 45.30 13 * 74 2.63

Example 3

A gas is passed through an apparatus at a temperature of 90 ⁰ G and the other conditions described in Example 1 and the apparatus over pressure (measured over the liquid) changed. Following contents of S0 _? in gas were determined:

Equipment overpressure

in kPa, 0.0 49.0 147.1 245.2

SO ₉ content (on)

in ^ g / m · ⁵ 66.05 71.31 66.92 67.80

SOp content (off)

ixTg / m * * 51.43 43.25 16.95 1.17

Claims (1)

237024 3 Erfindungaanapruch Process for the preparation of dilute sulfuric acid from SOp-containing gases by absorption and oxidation of sulfur dioxide, the gas being mixed with air or oxygen and reacted with an aqueous solution containing catalysts to accelerate the oxidation reaction, characterized that the suction-containing gas at elevated temperatures, preferably £ 60 ⁰ C and at pressures greater than atmospheric pressure, preferably 0.98 MPa Ä, is reacted with the absorbing solution. For this iSelto drawings Q Λ I ß f U U U J J J J J J J J 11