Scheme For Generating Liquid So2 Using Low Temperatures

The following scheme was considered for generating liquid sulphur dioxide from gases having an SO2 concentration of 20-50% (Figs.1, 2). The gas is compressed to 10 atmospheres, cooled to -30°C and passed through the turbo-expander where it is cooled to -78°C. Liquefied sulphur dioxide is separated after each stage. The effluent gas contains 0.6% SO2, and sulphur dioxide recovery at the last stage is 97.6% and 99.4% for gas streams containing 20% and 50% SO2, respectively.

Schematic Turbo Expander

Figure 1. Schematic diagram of low temperature production of liquid sulphur dioxide, 20%

SO2 in gas.

Figure 1. Schematic diagram of low temperature production of liquid sulphur dioxide, 20%

SO2 in gas.

Power inputs to generate liquid SO2 (calculated per ton) using gas streams with 20% and 50% SO2 at the compression and cooling stages are 205 and 78.5kW/t and 133 and 94.9kW/t, respectively. Figure 3 shows the change in the total power inputs (compression and cooling) needed to generate liquid sulphur dioxide using the proposed scheme, with liquid sulphur dioxide concentrations increasing in the considered gases. It is evident that power inputs reduce considerably as sulphur dioxide concentrations increase in the original gas stream.

Refrigerating machine

Compressor

Compressor

Figure 2. Schematic diagram of low temperature production of liquid sulphur dioxide, 50%

SO2 in gas.

350-

300-

40 60 80

SO2 content in gas, % vol

100-

Figure 3. Power inputs for low temperature production of liquid SO2: ® - with heat recuperation, n - without heat recuperation.

Power inputs can be reduced at the cooling stage by using cold recovery. The calculations based on using cold recovery for 20% SO2 streams under the scheme shown in Figure 4 demonstrate that power inputs reduce by nearly 2.5 times at the cooling stage. Another way to conserve energy can be the use of power generated by hot gases emerging from the smelters. Power-input data based on the use of energy recovered from cooling gases when generating liquid sulphur dioxide from gas streams containing 20, 50 and 75% SO2 is shown in Figure 3. It is evident that power inputs for compression and cooling are almost compensated with the energy generated via gas cooling.

Schematic Diagram Organic Cyclic Farming
Figure 4. Schematic diagram of low temperature production of liquid SO2 with cold recuperation; 20% SO2 in gas.

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