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Ammonia plays an important role in the national economy; currently, about 80% of ammonia is used to produce fertilizers, while the remainder is used as a raw material for manufacturing other chemical products. Nitrogen fertilizers used in agriculture, such as urea, ammonium nitrate, ammonium phosphate, ammonium sulfate, as well as various nitrogen-containing mixed and compound fertilizers, are all manufactured using ammonia as a raw material. However, the complex operating conditions in the ammonia synthesis process also pose significant challenges for industry professionals; its raw materials are nitrogen and hydrogen, which must be converted under high temperature and pressure conditions. N2: Nitrogen; H2: Hydrogen. One of the major challenges is the level monitoring in high-pressure gas-liquid separators. The case study in this article comes from a well-known fertilizer factory in Shanxi, and it focuses on the application of Dinghua external level switches for monitoring the level in high-pressure separators. The high-pressure gas-liquid separator, as a key device in ammonia synthesis processes in fertilizer factories, generates some waste liquid during the separation of ammonia. This waste liquid must be removed promptly; otherwise, frost may form at the bottom of the tank or the liquid level inside the tank may rise, affecting the normal operation of the facility. In more severe cases, overfilling of the tank can lead to ammonia leakage. △Schematic diagram of the gas-liquid separator (online). Since ammonia is a toxic, hazardous, and highly flammable substance, any leakage can contaminate the environment and pose a threat to human life and property. Therefore, during the production process, it is necessary to ensure that the waste liquid in the tank is discharged regularly or at specific intervals. In a large fertilizer plant, the ammonia production process consists of four stages: 1. Heating a mixture of solid amine salts and alkali. Reaction principle: 2NH4Cl + Ca(OH)2 = CaCl2 + 2NH3↑ + 2H2O. Reaction setup: Solid + Solid = Gas. 2. Heating concentrated ammonia solution. Reaction principle: NH3·H2O ==△== NH3↑ + H2O ； 3. Alkaline substances in concentrated ammonia solution: Reaction principle: The following equilibrium exists in concentrated ammonia solution: NH3 + H2O ⇌ NH3·H2O ⇌ NH4+ + OH-. 4. Industrial synthesis of ammonia: N2 + 3H2 → 2NH3; this reaction requires high temperature and pressure as well as a catalyst. In the case presented in this issue, the high-pressure gas-liquid separator used by the customer has flange holes pre-installed in the first two sections, allowing for the installation of flanged pipes. A magnetic float level gauge is employed; when it indicates that the liquid level in the tank has risen to a certain level, the discharge valve at the bottom of the tank can be opened manually or automatically to remove the waste liquid. The subsequent third and fourth sections are forged from 16Mn steel; there are no pre-drilled holes in these sections, making it impossible to install insert-type or submersible level gauges such as those based on buoyancy, double flange design, or radar technology ； Moreover, since the bottom of the tank is grounded, an external-type level gauge cannot be used either. It is difficult to estimate the height of the waste liquid in the tank, so companies can only drain it by manually opening the valves at regular intervals. This approach not only requires manual labor but also poses risks of delays and errors due to human intervention; it also hinders companies from achieving fully automated management and control, thereby reducing production efficiency. ►►►Dinghua Solution 01: Comprehensive analysis and identification of challenges – high pressure inside the tanks; no pre-existing holes. The pressure is 13.5 MPa for three-tank systems and 27.6 MPa for four-tank systems. To ensure safety, it is not possible to create holes, so isolated level gauges must be used ； The tank has a small diameter but a large wall thickness: its diameter is 444 mm, which is less than half a meter, while the wall thickness is 40 mm, which is relatively large ； The medium inside the tank is complex in terms of composition; it contains hydrogen, nitrogen, methane, argon, water, and other substances ； The state of the medium inside the tank is varied; there is mixing and separation of gas and liquid, and bubbles may be present in the liquid, which generates numerous interference signals. 02 Customized strategies to ensure stability: After attempts were made, it was found that traditional isolated external level gauges and external level switches could not fully meet the measurement requirements in the field. The new ELL-SA-QE type external level switch designed by Dinghua Electronics addresses the issues of weak signals and moderate stability resulting from thick wall thicknesses and small diameters. It utilizes a next-generation sensing probe; the technical performance of this probe has been optimized for such operating conditions, its structure has been improved, and the contact area between the probe and the tank wall has been increased, thereby enhancing signal strength and ensuring long-term signal stability ； △Application diagram of 3-stage separator △ Application diagram of 4-stage separator. To address the issues of complex media inside tanks and numerous interference signals, the new ELL-SA-QE external level switch incorporates a \"multi-source information fusion algorithm\" on top of the existing \"micro-vibration analysis technology\" and \"frequency-variable ultrasound technology\". Thanks to these multiple safeguards, the stability of the instrument is further enhanced. 03 Debugging and support for upgrades: Dinghua Electronics boasts a pre-sales and after-sales service system nationwide. In the face of special or complex operational conditions, it responds promptly by dispatching local customer service staff and technical experts to conduct on-site debugging, ensuring accurate and stable measurements. The ELL-SA-QE type external level switch continuously and stably outputs signals indicating the presence or absence of liquid, enabling users to install control valves later on to achieve automatic valve operation for liquid discharge. This enhances the automation level of the enterprise and improves production efficiency. All 8 sets of equipment in this company are equipped with ELL-SA-QE type external level switches. After 3 months of trial operation, the personnel on site report that the instruments operate stably, without any failures, and require no manual intervention. The control valves open and close accurately, and the discharge of waste liquid is safe and reliable! △Click to learn more about the new ELL-SA-QE external level switch