Plant operation in the chemical process industry (CPI)

Storage tanks on a chemical production plant

Find information on this page on the following topics:

  • Analysis in the Solvay process (soda ash production)
    > Learn more
  • Sulfuric acid determination in the cumene-phenol process
    > Learn more
  • Industrial wastewater characterization
    > Learn more

Steam tracing and corrosion

Chemical reactions are all about making and breaking chemical bonds. With increasing temperatures, bonding and debonding processes are significantly accelerated. This effect is utilized in chemical manufacturing, where reactants are heated up to operating temperatures for processing. Heat is also required to lower viscosity, keeping tars and waxes flowing through pipelines and equipment.

The heat required for process lines, vessels, and tanks may be provided by electric, fluid, or steam tracing. Since steam provides the highest temperatures of the three tracing methods, it has been a viable option for heating for over a century. Supplying steam to the inside of the jacketed kettle is an efficient way to heat the reactor contents.

Rusty pipe valve

Besides providing the necessary heat, steam also serves other purposes, including cleaning, moisturizing, and separation (stripping). All these benefits notwithstanding, steam is conducive to corrosion – often occurring in non-accessible places (e.g., corrosion under insulation, CUI) –, which has an enormous impact on plant integrity, safety, and operation costs.

To suppress corrosion, a chemical water treatment program is necessary to control and adjust the pH value and monitor the concentrations of corrosive ions, corrosion inhibitors, and corrosion by-products.

Metrohm offers a range of instruments and methods for measuring corrosion parameters. Read more about parameters that are relevant in the context of corrosion below.

Understanding and investigating corrosion

Detail of potentiostat/galvanostat instrument and software for electrochemical research

To counteract corrosion effectively, you need to understand the underlying corrosion processes and types (uniform, pitting, crevice, galvanic, or microbiologically induced corrosion).

> Metrohm has a series of Application Notes on corrosion. Read more …

Electrochemical analysis, e.g., linear polarization (LP) and electrochemical impedance spectroscopy (EIS), is widely used to investigate the corrosion mechanisms, allowing you to characterize the processes and effects quickly and accurately.

> Learn more about Electrochemical Impedance Spectroscopy

> Learn more about Metrohm Autolab instruments for electrochemistry

Monitoring corrosion indicators and inhibitors

Detail of an industrial petrochemical production plant
In chemical production plants, corrosion has to be prevented to the largest extent possible, since corrosion increases costs and plant downtimes. 

Corrosion control relies on two principles: removing corrosive compounds and adding corrosion inhibitors. The relevant parameters and compounds have therefore to be monitored:

  • Corrosion indicators, e.g., conductivity, pH value, or corrosive anions and cations
  • Corrosion inhibitors, e.g., zinc ions, phosphate, or phosphonates for steel and its alloys and triazoles for copper and its alloys

Metrohm pH electrode immersed in solution for use with pH meters

Corrosion indicators 

We offer the instruments and the know-how for conductivity and pH value measurement as well as anion and cation determination.

pH and conductivity measurement Anion and cation determination with ion chromatography
Chromatogram of corrosion inhibitors

Corrosion inhibitors

Corrosion inhibitors (zinc ions, phosphates, phosphonates, tolytriazole, benzotriazole, and 2-mercaptobenzothiazole) can be reliably monitored with ion chromatography with spectrophotometric detection.

Go to the application Learn more about Metrohm ion chromatography
Process Analyzer for voltammetric trace analysis for online monitoring of water and wastewater quality

Online measurements of Fe and Cu

Flow-accelerated corrosion (FAC) leads to thinned pipes and elevated Fe concentrations in the circuit. FAC in the heat exchangers results in elevated Cu concentrations. The 2045VA Process Analyzer detects these metal ions, before corrosion develops its destructive potential.

Learn more about the ADI 2045 VA Go to the application


Solvay process: Process monitoring in soda ash production

Portrait of Ernest Solvay

Soda ash (sodium carbonate) is a chemical that is not only used in the production of numerous goods (e.g., glass, soaps, detergents, and paper), but also for processes (e.g., in flue gas treatment in power stations, as an alkali in chemical manufacturing, and in water treatment). 

With global annual production totaling more than 40 million tons, soda ash is among the ten most produced chemicals. The largest portion of the soda ash is produced via the Solvay process, with the remainder being obtained from mined rock. In the Solvay process, sodium carbonate is produced from brine and limestone with ammonia acting as a “catalyst” through a series of chemical reactions.

Ammonia concentration in ammoniated brine

Schematic of the Solvay process

First, the brine is saturated with ammonia in the absorption tower. Then, in the carbonation tower, carbon dioxide – which stems from heated calcium carbonate (calcination) – reacts with the ammonia-saturated brine to form ammonium bicarbonate, then finally sodium bicarbonate and ammonium chloride. Sodium bicarbonate is heated in rotary dryers to produce light soda while ammonium chloride reacts with calcium oxide to recycle ammonia.

To ensure adequate product yield in the carbonation tower, the ammonia concentration in the brine has to be monitored after the brine has been saturated with ammonia. Metrohm Process Analytics online analyzers offer a solution for continuous monitoring and can be set up to trigger an alarm if the values are out of spec.

> Learn more about Metrohm Process Analytics instruments


And more …

Process Analyzer set up for online monitoring
Online process analyzers from Metrohm Process Analytics include both easy-to-use single-parameter analyzers and multifunctional versions fully tailored to your specific process requirements. Furthermore, they can be configured for a variety of analytes and parameters of interest in soda ash production, such as:
  • Alkalinity
  • Carbonate
  • Calcium oxide
  • Carbon dioxide
  • Hardness
> Learn more about our online process analyzers

Sulfuric acid in the cumene-phenol process

Most of the world’s phenol and acetone is made by the cumene process, also known as cumene-phenol or Hock process. First, benzene is Friedel-Crafts alkylated with propylene to the intermediate cumene (isopropylbenzene), which is oxidized to cumene hydroperoxide (CHP). After concentrating CHP in a series of distillation columns to about 65 to 90%, CHP is cleaved to form phenol and acetone. Small amounts of sulfuric acid (0.1 to 2%) catalyze the cleavage at 60 to 65 °C and prevent runaway reactions in the hot and concentrated CHP.

Illustration of the cumene process

Before downstream distillation and purification of phenol and acetone, the product stream is washed to remove sulfuric acid traces, which induce corrosion and produce undesirable by-products.

In the hazardous environment of the cumene process, rugged online process analyzers such as the 2026 Titrolyzer and ADI 2045TI monitor the concentration of sulfuric acid, as catalyst in CHP cleavage on the one hand and as a corrosive impurity in the product stream on the other. Besides online monitoring of the sulfuric acid, the analyzers can also titrate CHP concentrations.

> Learn more about the single-method 2026 Titrolyzer

> Learn more about the ADI 2045TI Process Analyzer


More applications and information

2035 Process Analyzer for photometric analysis

Calcium and magnesium in brine

In the electrolysis processes of the chlor-alkali industry, the purity of brine is crucial. Our process analyzers can be used in several stages of the process, from high feed concentrations of calcium and magnesium to very low concentrations in the ultrapurified brine.

Download the brochure Read the application More about the chlor-alkali process
Tubes in an industrial production plant

Peroxide in the HPPO process

Propylene oxide (PO) is an important intermediate in the chemical industry. The HPPO (Hydrogen Peroxide to Propylene Oxide) process yields PO from propene and hydrogen peroxide. Hydrogen peroxide is the critical parameter, because it indicates the conversion rate to PO. Our analyzers enable online monitoring of the H2O2 concentration.

Read the application Download the flyer Learn more about Process Analyzers

Industrial wastewater characterization

Miscellaneous standard-compliant methods for the examination of wastewater

Industrial wastewater treatment

Industrial production generates massive wastewater streams. Operators of wastewater treatment plants are obliged to monitor their installation to control its performance. Part of this duty is regular determination of various parameters in the laboratory and in the process. We have compiled a list of selected standards describing numerous international test and requirement specifications.

> Go to the standards overview