Urea process technology

CO2 stripping is the dominant method; many of the units in use nowadays employ CO2 stripping

The carbon dioxide stripping method has significant advantages

Of course, it’s the NH3 stripping method and the CO2 stripping method, as well as the full-circulation aqueous solution method – processes that have been phased out abroad. However, in recent years, through modifications by domestic experts, the water-based process has gradually moved closer to carbon dioxide stripping or ammonia stripping methods, with ammonia and gas consumption levels approaching those of the aforementioned two processes. Specifically, whether to adopt carbon dioxide stripping or ammonia stripping is a question; as for upgrading existing processes, it is more cost-effective to add equipment to the existing systems in order to save costs.

The CO2 stripping method can be scaled up on a large scale in China, giving it a significant advantage

Of course it’s the CO2 stripping process; currently, the CO2 stripping process is the main trend. Many new large-scale projects use this process. Aqueous solutions are already an obsolete process

The CO2 stripping method for urea production is not something new; 11 units with a capacity of 1,620–1,740 tons per day were introduced as early as 36 years ago. However, little progress has been made in urea production technology since then. Some advancements were made in terms of materials, with the introduction of pool-type condensers, but the overall technical approach remains unchanged. With proper management of the CO2 stripping process, it is possible to achieve ammonia consumption of 573 KG per ton of urea produced, CO2 consumption of 750 KG, steam consumption of 1,530 KG, electricity consumption of 18 KW/H, and recycled water consumption of 88 M3. The ammonia stripping method used in Italy is also not a new technique; it certainly has its own advantages. Its consumption levels are similar to those of the aforementioned method, and it allows for operation at lower loads as well as prolonged periods with the tower shut down. A number of such systems have been introduced in China, and there are also projects under construction.

Currently, the carbon dioxide stripping method represents the most advanced technology available – 2000+. The high-pressure urea production equipment has been simplified to either two units (a batch reactor and a stripping tower) or three units (a batch condenser, a stripping tower, and a synthesis tower with a washing section). The two-unit setup is not feasible for transportation within China due to the heavy weight of the equipment, so such systems are not available in that country; the three-unit setup is used by Ordos United Chemicals. Hainan Fudao and the Jinxin Chemical Plant under construction currently use pool-type condensers, but they still retain traditional high-pressure washers.