CS231487B1 - Method of utilization of heat and sulfur dioxide from combustion gases of boiler rooms in hydrometallurgical process - Google Patents

Abstract

The subject of the invention is a method of utilizing heat and sulfur dioxide from boiler flue gases in a hydrometallurgical process. The liquid phase containing ferrous sulfate is fed into a heat exchange device, where it is brought into direct contact with the flue gases. In this process, the flue gases are cooled while the liquid phase is heated, and the ferrous sulfate is oxidized by oxygen contained in the flue gases to ferric sulfate, and the sulfur dioxide is catalytically oxidized by this oxygen to sulfuric acid. The sulfuric acid enriches the liquid phase, which is subsequently used in the processing cycle of the hydrometallurgical process.

Description

(54) The use of heat and sulfur dioxide from the combustion gases of boiler rooms in a hydrometallurgical process

The subject of the invention is a method of utilizing heat and sulfur dioxide from the combustion gases of boiler rooms in a hydrometallurgical process. The liquid phase containing ferrous sulphate is fed to a heat exchange device where it is brought into direct contact with the combustion gases. The combustion gases are cooled while the liquid phase is heated and oxidation of the ferrous sulphate with oxygen contained in the flue gases to ferric sulphate and catalytic oxidation of sulfur dioxide with this oxygen to sulfuric acid. Sulfuric acid enriches the liquid phase, which is subsequently used in the process cycle of the hydrometallurgical process.

The subject of the invention is a method of utilizing heat and sulfur dioxide from the combustion gases of boiler rooms in a hydrometallurgical process.

The utilization of heat of combustion gases is of great economic importance and enables to increase the boiler room efficiency by up to 10% with respect to the primary fuel under appropriate conditions.

A number of types of recuperators are described in the literature, which remove the heat of the combustion gases and allow them to be used in various processes. However, these indirect recuperation devices have strict temperature limits in their operating mode and are characterized by never exceeding the condensation limit of the combustion gases, they are also structurally demanding and in many cases their reliability is problematic. The condensation limit significantly limits the amount of heat that can be recovered. The calculations confirm that these devices make it possible to recover a maximum of 50% of the useful heat of the combustion gases.

The hydrometallurgical process requires a considerable amount of water, often pumped from the sludge puddles, and thus ό ambient temperature, for its processing cycle. If it is necessary to heat the medium in the processing process, and most of it is, these volumes are heated to a technologically given temperature and, after the processing cycle, carry most of this heat back to the sludge in a thermally degraded form where heat is then transferred to the environment. The temperature differences between the discharged and the pumped liquid phase from the sludge reservoir reach several tens of ° C, which represents a large part of the energy intensity of the processing process at large volumes. The cost of heating such volumes of liquid phase to the required temperature is therefore very high. '

To a certain extent, these disadvantages are overcome by the method of utilizing heat and sulfur dioxide of the combustion gases of the boiler rooms in the hydrometallurgical process according to the invention.

It is based on the fact that the liquid phase, which contains ferrous sulphate, is fed to a heat exchange device, for example a shower preheater, where it is brought into direct contact with the combustion gases. Here, the combustion gases are cooled while the liquid phase is heated, and on the one hand, oxidation of ferrous sulfate by the oxygen present in the flue gases to ferric sulfate, and on the other hand, catalytic oxidation of sulfur dioxide by this oxygen to sulfuric acid. Sulfuric acid enriches this liquid phase, which is subsequently used in the process cycle of the hydrometallurgical process.

Process heat recovery and sulfur dioxide from exhaust gas boiler according to the invention, _t is based on the possibility that in many cases the layout offers tight linkage between boiler house and hydrometallurgical process, which for its processing cycle requires a considerable quantity of heated process water.

By utilizing the heat of the combustion gases to heat the liquid phase, the energy intensity of the actual processing cycle is reduced. In the case of the use of ferrous sulphate or manganese dioxide, the resulting sulfuric acid and ferric sulphate are advantageously used for their own processing cycle, and the emission of pollutants into the surrounding atmosphere is significantly reduced, which will have positive ecological effects, especially in large agglomerations.

A predetermined amount of iron salt or manganese ore may be metered into the liquid phase, which may be, for example, sludge-return water, process solutions or possibly mash, if these components are no longer present in sufficient quantities in the liquid phase due to process control. .

The cold liquid phase containing iron and manganese salts is fed to a heat exchange device, for example a shower preheater, where it comes into direct contact with the combustion gases. As it passes through the heat exchanger, the liquid phase raises its temperature and at the same time absorbs the constituents contained in the combustion gases, such as SO 2, which, as a result of 2 to 2 oxidation-catalytic reactions, translates to SO ₄ . ambient atmosphere. At the same time, ferric sulphate and sulfuric acid are formed and these components have a direct effect in the hydrometallurgical process. In 'many cases, therefore, a partial absorption of sulfur dioxide S0 ₂ from flue gases with regard to the subsequent use of the liquid phase only without the negative effects, but may be advantageous due to the formation of sulfuric acid and ferric sulfate, which is effectively used in technologibkém processing of uranium ores as an oxidizing agent. The low concentration of the sulfuric acid thus formed is preferably neutralized by the ore in the production process without having a negative impact on the corrosion problem.

Example

From the boiler combustion chamber, combustion gases of a volume of 60 x 10 µm / h, measured under normal conditions and at a temperature of 250 to 300 ° C, are sucked out by the fan into the bottom of the absorber.

The enthalpy of these gases in the temperature range of 30 to 300 ° C is equivalent to about 275 kg of black oil per hour, i.e. about 9.5 GJ / h. In the absorber, the combustion gases transfer the heat □ liquid phase in countercurrent. The liquid phase contains 0.1 to 1.0 kg / m < 2 > of FeSO4. and 0.5 to

3 ⁴

1.0 kg / m of manganese dioxide MnO ^ · Heated water at a flow rate of approximately 250 m / h exits the absorber at a temperature of 80 to 90 ° C and is pumped into the production process. The cooled combustion gases at 20 to 30 ° C, saturated with water vapor, are dispersed into the atmosphere. When the absorber is out of service, the combustion gases can be routed directly to the stack.

Claims (1)

SUBJECT OF THE INVENTION Process for utilizing heat and sulfur dioxide from combustion gases of boiler rooms in a hydrometallurgical process, characterized in that the liquid phase containing ferrous sulphate is fed to a heat exchange device, for example a shower preheater, where it is brought into direct contact with the combustion gases while cooling combustion of gases with simultaneous heating of the liquid phase and oxidation of ferrous sulphate by the oxygen present in the flue gases to ferric sulphate and catalytic oxidation of sulfur dioxide by this oxygen to sulfuric acid, which enriches this liquid phase which is subsequently used in the hydrometallurgical process .