Key Applications and Advantages of Titanium and Titanium Alloys in Urea Production

The production of urea, a neutral and efficient nitrogen fertilizer, involves several complex chemical reactions. In particular, the conversion of ammonium carbamate to urea is not complete and therefore requires efficient separation from a mixture containing urea, excess ammonia and water. Considering that the ammonium carbamate solution, an intermediate product generated at high temperatures and pressures, is extremely corrosive, the selection of the ideal material is of particular importance. Titanium stands out in this regard due to its outstanding properties.
Research by the American Crucible Company has shown that titanium equipment can significantly improve the efficiency of the urea process. This is mainly due to titanium's stable behavior at high temperatures. In contrast, stainless steel, although it has good corrosion resistance to urea at low temperatures, increases its corrosion rate exponentially with every 10°C rise in temperature. As a result, titanium tube heat exchangers and titanium piping have become indispensable and critical equipment in urea production plants.

Back in the 1960s, the Japanese Mitsui East Pressure Chemical Company took the lead in applying titanium as a lining material in urea production. After verifying the corrosion resistance of titanium through a series of experiments, the company decided to fully adopt titanium in the urea synthesis tower and its ancillary equipment. This innovative initiative not only increased the synthesis rate, but also simplified the operation process, improved product quality, and realized the large-scale equipment, which was eventually widely used in the global urea production field.
In the key process of urea synthesis, the Italian company Nationwide Methane Pipeline Transport also chose titanium for its stripper towers. This is because the use of amines in the stripper tower to separate the urea from the reactive products of the production process further exacerbates the problem of corrosion. Titanium's excellent corrosion resistance made it the ideal choice to solve this problem.
In the early 1970s, China also began to explore the application of titanium in urea production. At that time, China designed and manufactured a 240,000 tons of urea with carbon dioxide stripping tower, its key components such as the head, straight tube and upper and lower tube plate are used in the explosion composite titanium - steel plate technology, and built-in 1,361 31mm × 31mm titanium tubes. The equipment was put into production in 1979 and decommissioned in 1987, during which it operated for a total of 1,310 days and underwent 31,440 hours of chemical production tests with good performance. After that, in 1990, China successfully designed and manufactured a 400mm titanium-lined synthesis tower, which was put into operation in Anyang. Under the same conditions, the corrosion rate of titanium is one order of magnitude lower than that of 316L stainless steel, and the use of higher temperatures, thus bringing significant economic benefits for the enterprise in terms of power saving, steam saving and water saving.