Chlor-Alkali Industry Dependable online, inline, and atline solutions for your process needs. Chlorine and Caustic Soda: Chemical Building Blocks 02 Uses of chlorine Chlorine (Cl ) ranks number 7 on the list of the most com 2 monly produced chemical substances. Since chlorine is such an extremely reactive molecule, it is dangerous to transport and handle after purification. Corrosive acids can form if the purified Cl is exposed to moisture. 2 It is the ba sis for the production of numerous intermediate sub stances, which, in turn, are important feedstock ma te rials in the petroleum, aluminum, paper and pulp, or pharmaceutical industries. For instance, chlorine is used in the production of an impressive 80% of drugs. Polyvinyl chloride (PVC, one of the most widely produced polymers worldwide), isocyanates, and several chemical solvents can be made as a result of the generation of chlorine. Another common use is the disinfection of water sources (drinking water, swimming pools) to protect human health. Uses of caustic soda Caustic soda (sodium hydroxide, NaOH) is another cru cial basic chemical which enables production of or ga nic chemical products, bleach, detergents, paper, cellulose products, and several other materials. The Kraft Process, which is used in paper mil s to convert solid wood into pulp, is responsible for a considerable percentage of caustic soda consumption. This product is also used frequently to adjust pH in several production processes in many industries. The Chlor-Alkali Process By far the largest part – about 95% – of the chlorine pro ­ Safer technologies for the future 03 duced global y is obtained via the chlor­alkali process. In The most commonly applied electrolysis technique in this process, caustic and chlorine are created together in Europe is the membrane cell technique (64%). All new similar proportions via electrolysis of sodium (or po tasplants are based on membrane cell electrolysis of brine, sium) chloride brine. which does not include mercury and asbestos like the other processes. There are three main methods used to create chlorine and caustic from brine: In Europe, the top chlor­alkali producers are Germany, • membrane cell process fol owed by France, Belgium, and the Netherlands. • mercury cel process • diaphragm cel process Power Supply Chlorine Gas (Cl ) Hydrogen Gas (H ) 2 2 Na+ ions OH- pass through - membrane Na+ Cl- - Depleted brine 33% NaOH H + 2OH 2 2 + 2e 2 Cl2 H- Cl- OH- Caustic Soda 2Cl THODE (-) 30% NaOH (NaOH) 33% NaOH ANODE (+) A O + 2e 2 Cl- C Na+ 2H Evaporation steps Diluted Brine Diluted NaOH Saturated brine Non-permeable Ultrapure ion exchange membrane H O 2 Diagram of membrane cell technique for the production of chlorine. Adapted from www.eurochlor.org. 04 Reduce Risk with Online Process Analysis Every minute counts Advantages of online process analysis Performing manual sampling fol owed by laboratory Metrohm Applikon, with the brand of Metrohm Process analysis can take up precious time. Inefficient and Analytics instruments, is able to offer several application cumbersome analytical methods can also miss solutions for the chlor­alkali industry. significant events such as ion exchange breakthrough early on, or al ow the process to be out-of-specification Process analyzers from Metrohm are designed to offer until the next measurement is taken, whenever that may fast, reliable, accurate measurements in a rugged housbe. When it comes to true process optimization tactics, ing, 24/7 to ensure processes are always running within every minute counts. specifications. Online analysis with industrial process analyzers lessens the need for highly­skil ed technical In the membrane cell process, it is imperative that ulemployees and saves time by automating measurements trapure brine is used for electrolysis, otherwise the exdirectly at the sample point. Reducing manual samppensive membranes can become fouled. Even exposure ling lowers costs and increases the safety of plant to higher levels of hardness for a short time can lead operations. to premature membrane fouling. This causes a loss in current efficiency which leads either to higher utility With subsidiaries located worldwide, you can rest easy costs or lower product yields until the membrane is knowing we can support you local y, wherever you are. eventual y replaced during a scheduled shutdown. Y TIVIT $ SAVE PRODUC MONEY Applications Process Application Notes for the Chlor-Alkali Industry 05 • Hardness in Brine. AN-PAN-1005 Improve upon your brine treatment efficiency • Monitor hardness in brine in μg/L to mg/L with Brine must be pretreated in several steps to reduce im high­precision burette dosing & auto­calibration. purities such as calcium and magnesium ions (hard ness). • Available in three versions for maximum application After primary treatment, the purified brine is passed coverage: potentiometric titration, thermometric through an ion exchange unit to further minimize contatitration, or photometric measurement. minants before the electrolysis process. • Suitable for other applications such as caustic and carbonate in brine, hypochlorite in brine, chlorine Accurate determination of hardness concentrations can in brine & waste streams, and much more. estimate the efficiency of settling and resin treatments. Upstream control of brine quality helps overcome costly membrane remediation procedures before fouling oc curs. The 2035 Process Analyzer is the perfect solution to monitor hardness in brine online during all stages of this process. The Metrohm Process Analytics 2035 Process Analyzer (L), for The 2035 Process Analyzer configured for photometric meapotentiometric titration of high levels of hardness in raw brine. surements (R) is ideal for monitoring low concentrations of hardness in polished brine prior to the electrolysis process. Applications 06 Fast, safe moisture measurements in gases Inline near infrared spectroscopy (NIRS), with a reference Moisture determination in the produced gases (Cl , method (such as Metrohm Karl Fischer titration) is ideal 2 H ) is necessary to overcome corrosion in storage for this application. Near real­time analysis of low 2 containers and transport pipelines. Vaporization of the moisture content without chemical reagents is possible gases after storage, without proper removal of moisture with the use of flow cel s and fiber optic connections. beforehand, can also clog the container valves and lead to further handling issues. • Safe, reagent­free analysis directly inline. • NIRS XDS is capable of monitoring up to 9 different process points with the multiplexing capability. • Measurement technique sensitive to low levels of moisture. • Reference method also provided by Metrohm (Karl Fischer titration). • Process analyzer is available in ATEX version. The NIRS XDS Process Analyzer from Metrohm Process Analytics, configured for ATEX applications, with rugged flow cel s (R) for inline gas measurements. Applications Process Application Notes for the Chlor-Alkali Industry 07 • Online Determination of Anions in 50% NaOH and 50% KOH by IC (ASTM E1787­16). AN-PAN-1046 Impurities in concentrated caustic with Process IC • IC is a robust analysis method suitable for measur­ ASTM method E1787-16 specifies ion chromatography ing several components in a single sample run. to measure several anions in concentrated NaOH or • Intel igent sample preparation leads to safer analysis KOH solutions. The many intelligent sample pre con - and more reproducible results. ditioning techniques offered by the Metrohm Process • Measures analytes from ng/L to %. IC make the analysis of anion impurities in con centrated • Optional: integration of pressureless ultrapure water caustic solutions simple and easy to perform online. system for the most reliable automated trace analysis. The Process Ion Chromatograph TWO from Metrohm Pro­ Model shown with the optional integrated ultrapure water cess Analytics. Configured to analyze both anions and cations system (ELGA) and several sample preconditioning modules to simultaneously for the most comprehensive overview of your keep the analyzer running unattended with full protection from process. Up to 20 sample streams can be connected to a single harsh sample streams. instrument. www.metrohm.com itzerland w erisau, S 0 H ­910H , CG hm A etro otice y M r n rio rinted b ut p itho ­07 anciki, p 019 n L hange w lyso o c y A 51EN – 2 ut b 0.520.0 Subject t Layo 8