PROCESS ANALYTICS

Monitoring Steam Generators

Steam generators play a central role in a variety of processes. They feed generators or turbines in power generation, drive steam engines, provide power in thermal power plants, and are used in heat-consuming processes in the chemical and metal industries.

Since steam generators fulfill application-critical functions and the cost of their downtime or replacement is extremely high, damage caused by wear should be prevented by monitoring water quality. The following risks threaten the plant:

Contamination of pipes with biological or mineral substances that negatively affect the efficiency of the plant
Corrosion of plant parts, which shortens their service life and poses a potential hazard for personnel
Inadequate monitoring of the condensate, which leads to an increase in the number of desalination processes and in turn, to the economically inefficient consumption of water, chemicals, and energy.

Chemistry

Energy

Monitoring Water Quality Ensures the Output of Steam Generators

Heating pipes are in special focus when it comes to steam generators. Normally, steam generators are supplied with alkaline water that provides favorable conditions for the formation of a thin oxide coating on the surface of the heating pipes to protect against corrosion. To alkalize the water, sodium phosphate and sodium hydroxide are added to it. However, excessive addition of these chemicals can lead to problems and their metering should be based on precisely monitoring pH measurement.

The SE558 sensor was developed by Knick for high-precision pH measurement in liquids with very low ionic activity, which is why it is typically used in ultra-pure water applications and water treatment for power generation.

With its highly corrosive properties – even the smallest concentrations in the ppm range attack metallic surfaces – oxygen has a significant influence on the service life of steam generators. For this reason, chemicals like hydrazine are used to bind oxygen radicals.

The SE707 sensor measures dissolved oxygen down to the detection limit range in traces of 1 ppb, enabling hydrazine to be properly metered. Defective heating pipes or overdosing chemicals can lead to harmful substance concentrations in the water that can be detected by measuring contacting conductivity.

An increase in conductivity indicates increased contamination of the water, which must be countered with desalination or, if necessary, a plant inspection. For the precise, reliable measurement of small and the smallest conductivity levels in pure water, cooling water, and boiler feed water, as well as in steam circuits, Knick developed the Memosens SE604 sensor with robust stainless steel electrodes in a coaxial arrangement. Like all Memosens sensors, SE604 has an integrated temperature detector for exact temperature compensation.

Since the connections of conventional, analog sensors are not watertight, manufacturers of analog products encapsulate the cable in the sensor. This is why users must remove the cable at the transmitter when replacing sensors. With the contact-free, fully moisture-resistant measurement transmission of Memosens sensors, this effort is a thing of the past. Thanks to inductive measured value transmission in the Memosens sensor coupling, neither moisture nor incrustation can have a negative effect on transmission.

Further, digital Memosens technology makes it possible to pre-calibrate the sensors under ideal conditions in the laboratory and then have them replaced on site – even by untrained personnel. The cell constants are automatically transmitted to the transducer and are available for additional calibration operations.

Return on Investment

Since Memosens sensors need to be re-calibrated or replaced less often, your costs for measuring loop maintenance and procuring new sensors are significantly reduced.
And for applications with a high volume of moisture in particular, you benefit from much simpler sensor handling. With the inductive data transmission and supply voltage characteristic of Memosens sensors, and thanks to the high degree of protection of the transmitters, you no longer need to worry about wet or corroded contact loops or damage to the electronics. The transmitters have a three-year warranty from Knick.

Associated Products

SE707 Oxygen Sensor | Memosens | 120 mm | Ex | Measuring range (resolution) 0 ... 50 mg/l (1 μg/l)

Product number:

SE707X/1-NMSN

SE558 pH Sensor | Memosens | 120 mm | Ex | For ultrapure water, water and analytical chemistry

Product number:

SE558X/1-NMSN

SE604 2-Electrode Conductivity Sensor | Memosens | Ex | Measuring range from ultrapure water to 500 μS/cm

Product number:

SE604X-MS

Associated Industries and Applications

Chemistry

The chemicals industry is characterized by an extremely wide variety of applications, often in toxic and explosive environments.

Ion Exchanger Systems

Measurement of pH values, dissolved oxygen, and conductivity in boiler feed water, steam, and condensate in combined gas turbines in power plants.

Boiler Feed Water Circuits

Measurement of pH values, dissolved oxygen, and conductivity as key parameters in the boiler feed water circuit.

Cooling Water Systems

Measurement of pH value, redox potential, and conductivity in cooling water, which has to be continuously treated with acid and biocides.

Flue Gas Desulfurization

pH value measurement in the pre-scrubber, the neutralization phase, and the lime scrubber as part of the flue gas desulfurization process in power plants.

Combined Cycle Power Plants

Measurement of pH values, dissolved oxygen, and conductivity in boiler feed water, steam, and condensate in combined gas turbines in power plants.

Water Treatment Systems

Measurement of pH value, dissolved oxygen, and redox potential in various applications during the water treatment process of power plant wastewater.

Pulp and Paper Production

Many measuring loops in pulp production are located in environments in which technical personnel must spend as little time as possible.

Breakthrough Detection for Heat Exchangers

Heat exchangers are used when liquid process media need to be cooled and/or dissipated heat needs to be recovered for other processes.

pH Measurements in the Dye Synthesis of Azo Dyes

In terms of numbers, azo dyes are the largest group of synthetic dyes. They are used as food dyes, paint dyes, primary colors for 4-color printing (yellow and magenta), and on a massive scale, as textile dyes.

Cooling Tower Monitoring

In a wide range of industrial sectors, cooling towers are used to dissipate process heat from cooling circuits. Mineral deposits and corrosion reduce their efficiency and lead to premature wear on plant parts.

Reverse Osmosis Systems

Reverse osmosis systems are used for water treatment in a wide range of industrial applications. The main application is industrial saltwater desalination.

Energy Industry Brochure

Overview of specific applications and product solutions in different areas of power plants.

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