EATON MTL Gas Analysers and Systems User Guide

EATON MTL Gas Analysers and Systems

Product Information

The MTL gas analysers & systems, manufactured by Eaton, are designed specifically for monitoring hydrogen and chlorine gases in the Chlor-Alkali industry. These gas analysers are used to measure the composition of gas streams at different stages of the chlorine manufacturing process. The Chlor- Alkali process involves electrolysis of a salt brine solution to produce chlorine gas, hydrogen gas, and caustic soda. The MTL gas analysers are essential for maintaining the efficiency and safety of the manufacturing process.

Chlor-Alkali Process

The Chlor-Alkali process utilizes three electrolysis technologies – membrane, mercury, and diaphragm – to produce chlorine gas and caustic soda. The majority of plants have shifted from mercury-based technologies to more energy-efficient membrane technology. During the electrolysis process, an electric current is passed through a brine solution, resulting in the production of chlorine gas at the anode and hydrogen gas at the cathode. Caustic soda solution is also produced as a by-product.

Gas Makeup Measurement

It is crucial to measure the composition of gas streams at different points in the chlorine manufacturing process. Gas compositions are typically measured at the following points:

1. Straight from the electrolysis plant (Wet Chlorine)
2. After the cooling tower (Dry Chlorine)
3. During the washing/liquefaction stages of the process
4. After the liquefaction process or hypo plant (Dry Chlorine) (Tail / Snift Gas)

Understanding the gas makeup is important for ensuring process efficiency, maintaining product quality, and ensuring safe operation.

Product Usage Instructions

To use the MTL gas analysers for hydrogen and chlorine monitoring in the Chlor-Alkali industry, follow these steps:

1. Install the MTL gas analysers at the desired measurement points in the chlorine manufacturing process.
2. Ensure that the gas analyser is properly connected to the gas stream being measured.
3. Power on the gas analyser and allow it to initialize.
4. Select the appropriate gas composition measurement mode on the analyser.
5. Wait for the analyser to stabilize and provide accurate readings.
6. Repeat the above steps for each measurement point in the process.
7. Monitor the gas composition readings displayed on the analyser’s screen or interface.
8. If any abnormalities or deviations from desired gas makeup are detected, take appropriate corrective actions to ensure process efficiency and safety.
9. Regularly calibrate and maintain the MTL gas analysers as per the manufacturer’s instructions to ensure accurate and reliable measurements.

Following these instructions will help you effectively monitor hydrogen and chlorine gases in the Chlor-Alkali industry using the MTL gas analysers, ensuring optimal process performance and product quality.

Hydrogen & Chlorine monitoring for the Chlor-Alkali Industry

Eaton’s MTL product line manufacture a range of application specific hydrogen and chlorine gas analysers for monitoring all process stages in the manufacture of chlorine gas.
Chlor-alkali chemistry produces three highly useful chemical building blocks: chlorine, sodium hydroxide (caustic soda) and hydrogen. These building blocks react with other compounds to produce thousands of vital products used around the world each day, including plastics, pharmaceuticals and crop protection products.

What is the Chlor-Alkali process

The Chlor-Alkali process involves passing electricity through a salt brine (NaCl) solution with chlorine gas being produced at the (+ve) electrode (anode) and hydrogen gas at the (-ve) electrode (cathode), a process known as electrolysis with an important by-product of the process being the production of caustic soda solution (NaOH).
There are three electrolysis technologies used for producing chlorine and caustic soda, these include – membrane, mercury and diaphragm. Historically most plants have utilised mercury based technologies but environmental pressures have driven the chlor-alkali industry towards closing or converting the vast
majority of mercury based plants. Over the past fifteen years
the gradual shift away from the mercury cell technology has
continued, with more energy-efficient membrane technology
now providing for the majority of chlorine capacity.

How does it work

• Chlorine is produced by passing an electric current through a solution of brine (common salt dissolved in water). This process is called electrolysis. The chemical term for salt is sodium chloride (NaCl).
• The two electric connection points of each chlorine production cell, the anode and the cathode, are separated by an ionexchange membrane. Only sodium ions and a little water pass through the membrane.
• The brine is de-chlorinated and recirculated.
• Solid salt is usually needed to re-saturate the brine.
• After purification the brine is further purified by precipitationfiltration using an ion exchanger.
• The caustic solution (NaOH) leaves the cell with about 30% concentration and, at a later stage in the process, is usually concentrated to 50%. The chlorine gas contains some oxygen and must often be purified by liquefaction and evaporation.

Where to measure your gas makeup

• It is important to understand the composition of your gas streams throughout the chlorine manufacturing process.
• From the electrolysis plant the Chlorine gas undergoes a process of filtration, purification and liquefaction, similar to that shown below:

Gas compositions are typically measured at the following Points:

1. Straight from the electrolysis plant (“Wet Chorine”)
2. After the cooling tower (“Dry Chlorine”)
3. During the washing / liquefaction (“Dry Chlorine”) stages of the process
4. After the liquefaction process (“Tail / Snift Gas”) or hypo plant

Why measure your gas makeup

It is important to understand the composition of your gas streams across the various stages in the production process for a number of key reasons:

Hydrogen Concentration Measurement
This is a critical safety process indicator to ensure that the hydrogen levels in chlorine gas are maintained well below the lower explosive limit (LEL) of 4% H2 in Cl2. Increasing hydrogen levels are also used as an indicator to give advanced warning on potential membrane failure in electrolyser cells.

Chlorine Concentration Measurement

As the primary product it is essential the concentration of this highly toxic and corrosive gas be continuously monitored. It is important to measure the chlorine concentration in order to understand the efficiency of the electrolysis, drying and liquefaction process stages. Also, by measuring both the hydrogen and chlorine gas components together, this allows the amount of impurity gas (inert’s) to be determined in the final manufactured chlorine product.

How we measure your gas makeup

• Our KK650 instrument has been specifically developed to measure hydrogen and chlorine gas in all process stages of the Chlor Alkali production process with a key design feature being that it can be easily installed and serviced in the field by end users. It measures hydrogen in the range of 0 to 5% H2 or 0 to 10% H2 with a 4 to 20mA output signal that can be programmed down to a range of 0.00 to 1.00% H2.
• At the same time as measuring hydrogen, chlorine gas is also measured over the range 0 to 100%, which can be calibrated using plant laboratory results or benign surrogate gases if required.
• As shown in the below diagram, the complete analyser comprises two separate parts, where the control electronics are housed in a weather proof GRP cabinet with the sensor/reactor being mounted on in separate remote panel or GRP enclosure. This is an important design concept that reduces the risk of any chlorine corrosion attack on the electronics, either by chlorine gas leaking from any sample pipework, and or entering the cabinet from the surrounding ambient air. As an additional safe guard against chlorine attack in harsh environments, an air purge option can also be offered with the analyser electronics cabinet.
• The unique design of our software and dual sensor katharometer, allows the analyser to interpret and calculate the hydrogen, chlorine and inert gas components of the chlor-alkali process gas during “start-up” and normal running conditions. The non-depleting design of our katharometer (TCD) sensor comprises two thermal conductivity measurement sensors and a sealed reference sensor for ambient temperature corrections. These are mounted together in one encapsulated assembly, which ensures that the chlorine sample gas only comes into contact with materials that are chemically compatible.
• The thermal conductivity of the sample gas is measured before and after the heater reactor by means of two sensing elements as shown below. The hydrogen gas component of the sample, in preference to oxygen, reacts with excess chlorine gas during the heater reaction. The difference in thermal conductivity between sensor 1 and 2 is used to calculate the hydrogen value, as the inerts remain unchanged during the reaction. The chlorine gas measurement is determined through the KK650 software and calibration look up table.
• Sensor 1 Sample Composition (Before Reactor) H2 + Cl2 + inerts (CO2 + N2 + O2)
• Sensor 2 Sample Composition (After Reactor) HCl + Cl2 + inerts (CO2 + N2 + O2)

What sample system to use

• Selecting the correct analyser to match your process requirements is only part of the solution. Ensuring you have the correct sample system for the process sampling point is critical to the accurate, reliable and trouble free operation of your plant analyser system.
• Our experienced application specialists are available to offer technical support and assist in the design and development of tailored sample conditioning systems for both wet and dry chlorine gas.

Advantages of the KK650 when compared to GC and IR/UV based anlaysers

<5 years
Sensor Maintenance| Can be washed| Can not be washed| Can not be washed
Cost of ownership| Calibration gases +labour| Calibration gases,labour + columns| Calibration gases,filters + labour
Ease of Installation + commissioning| Can be installed by a competent site C&I Engineer| Often requires the support of an engineer from the supplier. Installation of a permanently installed carrier gas supply is also required.| Often requires the support of an engineer from the supplier.
Ease of replacing old installed analysers| Very small compact instrument that can be installed outside.| Additional instrument housing often required with a permanent installed gas bottle/

carrier gas line.

| Typically supplied in a large floor mounted enclosure (houses two instruments). Typical size being 2m (6.5ft) x 2m (6.5ft)

What we offer

Our Chlorine / Hydrogen gas analyser range has been developed with the specific requirements of the Chlor Alkali industry in mind. Over the past 30 years we have worked closely with Plant Operators, OEMs and Process Licensors alike to develop the latest generation of gas instruments. Key benefits we can offer include:

• A proven solution with over 30 years gas analyser design experience.
• Unique non-depleting sensor design.
• Online continuous measurements during “start-up” and normal running process conditions.
• Designed to be installed and maintained by end-users with minimal maintenance.
• No hidden expensive service contracts are required.
• Comprehensive lifetime service kits provided
• With regional offices and a global distributor network, we are well-positioned to assist you and your customer needs wherever they may be.

Eaton are world leader in the development and supply of Intrinsic Safety, Industrial Networks, Visualisation and Surge Protection products. We have been an international manufacturer of fixed and portable gas analyzers for over 30 years, supplying process industries with gas instruments for both safe and hazardous area applications. Instruments manufactured include portable, fixed and custom built analysers, complete with sample conditioning systems.
For further details on this or any other of our products, including application-specific analysers, detailed application guides, reference lists and presentations, please visit our website or contact us directly at –
www.mtl-inst.com
mtlgas@eaton.com
+44 1582 435600

Eaton Electric Limited, Great Marlings, Butterfield, Luton Beds, LU2 8DL, UK.
Tel: + 44 (0)1582 435600 Fax: + 44 (0)1582 422283 www.mtl- inst.com
E-mail: mtlgas@eaton.com
© 2016 Eaton
All Rights Reserved Publication No. AN-9041 Rev 2 181016 October 2016

EUROPE (EMEA):
+44 (0)1582 723633
mtlenquiry@eaton.com
THE AMERICAS:
+1 800 835 7075
mtl-us-info@eaton.com
ASIA-PACIFIC:
+65 6 645 9888
sales.mtlsing@eaton.com

The given data is only intended as a product description and should not be regarded as a legal warranty of properties or guarantee. In the interest of further technical developments, we reserve the right to make design changes.

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