Level measurement solutions for ammonia vaporisation skids

Ammonia vaporisation changes the state of ammonia from a liquid to a gas. Vaporised ammonia is important for use in industrial refrigeration and in pollution abatement technology, such as selective catalytic reduction (SCR) systems used to neutralise nitrogen oxides from large electric utility and industrial boilers.

Although ammonia is generally shipped and stored under pressure in its liquid form, it is most frequently used in its vapor state. Aqueous ammonia vaporisation uses heat to evaporate an ammonia and water mixture. The liquid is mixed with atomising air and dispersed into the vaporisation chamber as a fine mist where it is heated until it vaporises. The air, ammonia, and water vapour mixture is then transferred to the injection grid.

In this article, Magnetrol explores skid configurations for vaporising ammonia and discusses common level applications that impact skid functioning.

Why Choose Skids?

Throughout the process industry, modular fabrication has become a viable option to field construction for owner/operators, OEMs, and plant engineers. From zero site disruption during fabrication to plug-and-play commissioning, single- and multiple-skid systems have become more popular in recent years. Nearly any unit operation can be fabricated as a self-contained, modular skid system. While most skids are housed within an open structural framework, a skid maker can also fabricate the skid system inside a standard shipping container.

Anhydrous and aqueous ammonia are skid-configured for unloading, storage, transfer, vaporisation, stripping, metering, injection, and urea-to-ammonia (U2A) conversion. Skids range from compact, single-process systems to multi-unit utility systems.

Level Measurement Solutions

Below are common level measurement applications for ammonia vaporisation skids and level measurement solutions for these applications:

• Ammonia Storage Tanks: Pure ammonia is stored in a pressure vessel rated at 250 to 300 psig. Aqueous ammonia (70 to 80 per cent water) is stored in a tank rated at 25 to 30 psig. For continuous level, the Eclipse Model 706 guided wave radar transmitter or the Atlas or Aurora magnetic level indicators are recommended. For point level, the Model A10/A15 single stage displacer switch is recommended.
• Mixing Tanks: The mixing tank uses an agitator for blending. Level controls trigger alarms in underfill and overfill incidents. For continuous level, the Pulsar R86 non-contact radar transmitter or the Atlas or AURORA magnetic level indicators are recommended. For point level, the Echotel Model 961/962 ultrasonic level switch or the Model T20 single stage float level switch are recommended.
• Vaporiser Liquid Level: Functioning as an essential safety measure, a level switch in a vaporiser can provide high liquid level alarm, overfill tank alarm, leak detection alarm, or low level alarm. For continuous level, the PULSAR R86 non-contact radar transmitter; the ECLIPSE Model 706 guided wave radar transmitter; or the ECHOTEL Model 355 ultrasonic transmitter are recommended. For point level, the ECHOTEL Model 961/962 ultrasonic switch for high/low alarm or the Thermatel TD1/TD2 are recommended.