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Concentration and density measurement of H2SO4 in copper mining

Copper is obtained by the extraction of copper sulfide ores, which have a copper content of ~ 2 wt%. The raw metal production includes a wide variety of process steps. 

Analyzer Sulfuric acid monitoring

Case studies on sulfuric acid in copper mining


Benefits Sulfuric acid monitoring

The processing of copper sulfide ores is carried out by flotation. Thereby, crushed copper sulfide ores are enriched with water and a foaming agent, to skim quartz or silicates. The obtained copper concentrate has a copper content of 20 - 40 wt%. 

In the pyrometallurgical extraction, SO2 is generated which is oxidized with atmospheric oxygen to form sulfur trioxide SO3 (contact process). What remains is a copper content of approx. 96-99 wt%. In order to reach a purity of 99.99 wt%, a electrolytic refining takes place subsequently. Otherwise, the impurities strongly influence the thermal and electrical conductivity and quality of copper.

Challenges in measuring the density or concentration of sulfuric acid

During the process of sulfuric acid production, process engineers are often faced with a challenge:

Numerous measuring methods, with which the concentration or density of the sulfuric acid is to be measured, work only insufficiently at a concentration of 85m% - 99m%. These problems occur especially when the underlying physical value of the concentration or density meter does not change when the concentration changes.

For example, the diagram shows that conductivity sensors provide only poor measuring results for a concentration range of sulfuric acid of 80m% - 97m%, because the conductivity of the liquid hardly changes in this concentration range. For this reason, conductivity sensors have extremely low measuring accuracy if sulfuric acid is to be analyzed in this measuring range.

The situation is similar with density meters, where the density of the liquid itself is to be evaluated. Here it can be seen that especially in measuring ranges above 90m% the density of the liquid hardly changes. Therefore, many simple density meters show high problems if they are to be used to measure the concentration of sulfuric acid in this measuring range.

LiquiSonic® sonic velocity measurement

Precise measurement of the concentration and density of sulfuric acid using the sound velocity

In contrast to conductivity or density sensors, ultrasonic measuring instruments are able to measure the concentration of sulfuric acid extremely precisely. When the concentration of sulfuric acid changes, the speed of sound also changes significantly. Therefore, concentration meters whose sensors evaluate the velocity of sound deliver significantly more accurate results than conductivity or density meters.

 

Application

In the pyrometallurgical extraction, the copper concentrate is slagged by adding SiO2 in the furnace at 1200 to 1400 °C. The melt of copper and iron sulfi de is removed as the so-called copper matte from the slag phase. The liquid copper matte is poured into a converter and the iron sulfi de reacts with air to sulfur dioxide SO2.

Resulting SO2 is oxidized to sulfur trioxide SO3 (contact process), which SO3 is directed into sulfuric acid (96 wt%). In the absorber, sulfuric acid in high concentrations by adding water or oleum is generated. In the blending process, the H2SO4 is diluted on desired target concentration. Each process step can be both monitored continuously by the inline LiquiSonic® measurement technology and optimally set. The high dependency on sonic velocity enables an accuracy of +/- 0,05 wt% for sulfuric acid.

Installation

The LiquiSonic® immersion sensor is easily installed into pipelines after absorber or sulfuric acid produc-tion and blending. By using the LiquiSonic® controller 30, up to four  sensors can be connected, allowing the simultaneous monitoring of several measuring points.

Typical measuring range:
concentration range from H2SO4: 80 to 100 wt%
temperature range: 20 to 90 °C

concentration range from oleum: 0 to 10 wt%
temperature range: 10 to 60 °C

Customer Value

The LiquiSonic® analyzer provides a precise inline H2SO4 and oleum concentration measurement with real-time monitoring. The robust sensor construction and the optional special materials, like Hastelloy C2000, promote long process life. 

LiquiSonic® enables a reduction of labor cost through the elimination of manual process steps:

  • time saving: 1 h per day

In comparison to conductivity and density measurement, LiquiSonic® generates a clear signal in the concentration range from 80 to 100 wt% and provides at every time reliable process information.