I. Urea: The "Golden Player" in the Fertilizer Industry

Urea (CO(NH₂)₂), with a nitrogen content as high as 46%, is the "top-tier" nitrogen fertilizer. It not only provides nutrients for crops but also plays a significant role in industrial denitrification and automotive urea applications. But did you know? Behind these seemingly ordinary white granules lies a perfect combination of high-temperature, high-pressure chemical reactions and precision industrial processes.

II. Core Raw Materials: The "Duel" Between Coal and Natural Gas

The two main schools of urea production—coal-based urea and gas-based urea—directly determine cost and process.

• Coal-based urea: Uses coal as raw material, which is gasified to produce synthetic ammonia, which then reacts with carbon dioxide. 70% of my country's urea comes from coal-based processes. Its advantage is low raw material cost, but it has high carbon emissions.

• Gas-based urea: Relies on natural gas, resulting in a cleaner process, but it is greatly affected by fluctuations in international gas prices. For example, producing 1 ton of urea requires 700 cubic meters of natural gas, and the cost formula is **"natural gas price × 700 + 300 yuan"**. • Oil-based urea: Due to excessively high costs, it has been largely phased out.

III. Core Process: The Four-Step Transformation from Liquid Ammonia to Granules

Whether coal-based or gas-based urea, the core process involves four main steps:

Liquid Ammonia Pressurization (High-Pressure Injector): Liquid ammonia is pressurized to 14 MPa, mixed with carbon dioxide, and then fed into the reaction "heart"—the synthesis tower.

High-Temperature and High-Pressure Synthesis (Synthesis Tower): In a "pressure cooker" at 183℃ and 14 MPa, liquid ammonia and carbon dioxide first react to form ammonium carbamate, which is then dehydrated to form urea. The conversion rate in this step is only 50%-75%, and unreacted gases must be recycled.

Stripping Decomposition (Stripping Tower): Using high temperature and carbon dioxide gas, unreacted ammonium carbamate is "forced" back into the synthesis system, achieving a "full cycle" of raw materials.

Evaporation and Granulation (Granulation Tower): Molten urea is concentrated to 99.7% through two stages of evaporation, then spray-cooled to form uniform granules for easy storage and transportation.