To produce anhydrous ammonia from natural gas. The process is based on applying Casale’s highly efficient equipment, including:
• Casale high-efficiency design for the secondary reformer
• Casale axial-radial technology for shift conversion
• CASALE ejector ammonia wash system
• Casale axial-radial technology for the ammonia converter
• Casale advanced waste-heat boiler design in the synthesis loop.
Natural gas (1) is first desulfurized (2) before entering a steam reformer (3) where methane and other hydrocarbons are reacted with steam to be partially converted to synthesis gas, i.e., hydrogen (H2), carbon monoxide (CO) and carbon dioxide (CO2). The partially reformed gas enters the secondary reformer (4) where air (5) is injected, and the methane is finally converted to syngas. In this unit, Casale supplies its high-efficiency process burner, characterized by low ΔP and a short flame. The reformed gas is cooled by generating high-pressure
(HP) steam, and then it enters the shift section (6), where CO reacts with steam to form hydrogen and CO2. There are two shift converters, the high-temperature shift and low-temperature shift; both are designed according to the unique axial-radial Casale design for catalyst beds, ensuring a low ΔP, lower catalyst volume, longer catalyst life and less expensive pressure vessels.
The shifted gas is further cooled and then it enters the CO2 removal section (7), where CO2 is washed away (8). The washed gas, after preheating, enters the methanator reactor (9), where the remaining traces of carbon oxides are converted to methane.
The cleaned synthesis gas can enter the synthesis gas compressor (10), where it is compressed to synthesis pressure. Within the syngas compressor, the gas is dried by the ejector driven Casale liquid ammonia wash (11) to remove saturation water and possible traces of CO2. This proprietary technology further increases the efficiency of the synthesis loop, by reducing the power requirements of the synthesis gas compressor and the energy duty in the synthesis loop refrigeration section.
The compressed syngas reaches the synthesis loop (12) where it is converted to ammonia in the Casale axial-radial converter (13), characterized by the highest conversion per pass and mechanical robustness. The gas is then cooled in the downstream waste-heat boiler (14), featuring the Casale water tubes design, where HP steam is generated. The gas is further cooled (15 and 16) to condense the product ammonia (17) that is then separated, while the unreacted gas (18) is circulated (19) back to the converter. The inerts (20), present in the synthesis gas, are purged from the loop via the Casale purge recovery unit (21), ensuring almost a complete recovery of the purged hydrogen (22) back to the synthesis loop (12), while the inerts are recycled as fuel (23) back to the primary reformer (3).
Licensor: Ammonia Casale SA, Switzerland