The LiquiSonic® Measurement technology is used in various processes and production streams to detect concentration and thus optimize quality and productivity. Another application field of the measurement technology is in the downstream process of chlorine gas drying. The chlorine gas must be freed from its water content, otherwise chlorohydrate forms and the corrosion behavior continuously increases with a moisture content above 30 ppm.
Advantage of sound velocity over conductivity and density
Application
The process of chlorine gas drying is based on passing the gas through absorption towers (scrubbers), where the water content in the chlorine gas is chemically bound by concentrated sulfuric acid (H2SO4) is chemically bound. Sulfuric acid is used as a drying agent because it has hygroscopic properties, meaning a strong attraction to water.
The moist chlorine passes through several scrubbers during drying, with the concentration of H2SO4 increasing from scrubber to scrubber. The higher the H2SO4- is concentrated, the higher the absorption efficiency (or effectiveness of drying). In this regard, there is a highly concentrated H2SO4 (90 – 96 %), da die Wasseranteile im Chlorgas auf wenige ppm (< 30) reduziert werden. Durch die Entziehung der Wasseranteile im Chlorgas, kommt es zu einer Verdünnung der Schwefelsäure in den Scrubbern. The verdünnte H2SO4 is consequently led into the previous scrubbers with lower H2SO4 concentrations.
The effectiveness of this drying process significantly influences the productivity and quality of the gas. Therefore, reliable measurement of the sulfuric acid concentration is of particular importance.
The measurement system LiquiSonic® 30 enables the measurement of sulfuric acid concentration using sound velocity and provides highly accurate temperature measurement. Through inline concentration analysis with LiquiSonic® sensors the process of chlorine gas drying can be analyzed around the clock, guaranteeing an exact real-time analysis of the sulfuric acid concentration. Through precise monitoring of the sulfuric acid concentration in the respective absorption towers using the measurement system LiquiSonic® 30 the desired effectiveness of chlorine gas drying is ensured at all times.
Installation
The installation of the sensors takes place in the DN80 transport lines of the absorption towers.
Concentration range H2SO4: 70 wt% to 100 wt%
Temperature range H2SO4: 20 °C to 60 °C
When used in sulfuric acid, the liquid-contacting parts of the sensor are made of HC2000.
Customer benefits
LiquiSonic®enables a reduction in laboratory costs by eliminating manual sampling:
- Time required: 3 hours per day
Payback period: approximately 7 months
Um Anlagenteile vor Korrosion zu schützen,muss der Wasseranteil im Chlorgas weniger als 30 ppm betragen. Durch die kontinuierliche Überwachung der Schwefelsäure in den jeweiligen Scrubber kann die erforderliche Reinheit des Chlorgases (< 30 ppm H20) can be ensured.
Chlorine is one of the most important basic chemicals and is among the most produced chemicals worldwide. Chlorine is produced on a large scale through chlor-alkali electrolysis. The starting material for electrolysis is an aqueous sodium chloride solution (NaCl). Hydrogen and caustic soda are by-products, which are also recycled in large quantities by the chemical industry. In the chlor-alkali process, different electrolytic methods are used, with the diaphragm, membrane, or amalgam process being themost common production technologies.
