Sulfuric acid is one of the world’s most widely produced basic chemicals and places high demands on process control, materials, and plant safety. In production using the double-contact process (DCDA) or the contact process (WSA), the exact acid concentration at each process stage determines the absorption rate, product yield, emissions, and corrosion load. Even small deviations can have significant economic consequences when production volumes are high. With LiquiSonic®, SensoTech offers an inline measurement system that measures the concentration of sulfuric acid and oleum directly in the process and in real time, thereby providing a reliable basis for process decisions.
In-line measurement for sulfuric acid and oleum
The focus is on highly concentrated media that require special process and safety considerations due to their corrosiveness and reactivity. It is particularly crucial in these cases to continuously monitor the actual condition of the liquid. LiquiSonic® measures directly in the pipeline (or in a bypass) and provides continuous information on concentration and process temperature.
High Concentrations, Corrosive Media, Delayed Laboratory Results
Sulfuric acid plants face the challenge of reliably and traceably assessing acid concentration simultaneously across multiple process stages. A laboratory sample provides important quality information but reflects only a specific point in time. Often, the laboratory result is not available until hours later. In practice, however, concentrations change dynamically—for example, due to fluctuating gas qualities, changes in water addition, or temperature effects. If absorption operates outside its optimal window, this has a direct impact on yield, emissions, and plant availability. Furthermore, manual sampling of hot, highly concentrated acid streams is labor-intensive and involves risks.
Temperature-compensated and integrable into existing systems
LiquiSonic® is based on a high-precision measurement of the speed of sound in the medium. In addition, the process temperature is recorded and factored into the analysis. Since the speed of sound in sulfuric acid depends heavily on concentration, a distinct measurement signal is generated in the range from 70 to 100 wt%. Unlike conductivity or density measurements, the measured value can thus be clearly identified even in the highly concentrated range. The achievable accuracy is up to ± 0.03 wt%.
The measurement system operates inline and without consumables. The robust, maintenance-free sensor design prevents extended process downtime. A LiquiSonic® controller can be connected to up to four sensors, allowing multiple measurement points to be monitored simultaneously. Measurement values can be displayed on-site, documented, or transmitted to the process control system via serial interfaces, fieldbus, or Ethernet, for example. This allows monitoring, alarms, dilution control, or release decisions to be integrated directly into existing operational workflows.
Greater transparency for yield and quality
The key added value lies in continuous concentration measurement. While laboratory analyses are always delayed, and indirect parameters fail to adequately reflect dynamic process changes, LiquiSonic® provides reliable real-time information. Notable trends or critical deviations become apparent at an early stage. This allows for a timely response to issues such as declining absorption efficiency, incorrect water addition, or the risk of falling below the corrosion protection window. At the same time, the effort required for sampling is reduced.
Direct Benefits for Sulfuric Acid Plants
LiquiSonic® is designed for companies that produce, condition, use, or distribute sulfuric acid or oleum. Typical users include operators of DCDA and WSA plants, sulfuric acid manufacturers and distributors, fertilizer producers, mining and smelting operations involving ore beneficiation, as well as plants with chlorine and synthesis gas drying, gas scrubbers, or etching and pickling baths. This measurement solution complements existing safety and quality concepts by providing continuous, maintenance-free inline monitoring.
