Ammonium sulfate (NH4) 2SO4, abbreviated as ammonium sulfate, commonly known as manure powder, contains about 20% nitrogen and 25% sulfur, with a moisture content of 0.2%. It is the earliest nitrogen fertilizer variety used and produced in China, currently accounting for about 0.7% of China's total nitrogen fertilizer production. Pure products are colorless orthorhombic crystals, while industrial products are white to pale yellow crystals. Density 1.77, high decomposition temperature (greater than 280 ℃), not easily hygroscopic, but difficult to break after clumping.

Ammonium sulfate can be used as base fertilizer, topdressing, and seed fertilizer. Suitable for general soil and crops, it can promote vigorous growth of branches and leaves, improve fruit quality and yield, enhance crop resistance to disasters, and long-term use may lead to soil compaction. Suitable crops are more common, including wheat, corn, rice, cotton, and various economic crops;

The production of ammonium sulfate is made by neutralizing ammonia and sulfuric acid, but later the proportion of by-product ammonium sulfate increased. Now, most of the ammonium sulfate in China comes from three major fields: coking, caprolactam, and other industries, with ammonium sulfate production accounting for 52%, 30%, and 18%, respectively. Other industries include acrylonitrile, methyl methacrylate, sulfuric acid tail gas desulfurization, zinc oxide, power desulfurization, etc.

At present, ammonium sulfate is mainly used as a raw material for steam pellet method compound fertilizers in China. The direct fertilization amount is only a small amount. We should vigorously explore the direct fertilization market, optimize the market consumption structure, and achieve a balance between supply and demand in the market. Accelerating the development of the direct fertilization market is the top priority for the future ammonium sulfate market.

Ammonium sulfate, a by-product of coking and power industries, is in powder form and difficult to control due to clumping and poor fluidity. To expand the direct fertilization market, it is necessary to carry out dry rolling granulation. Ammonium sulfate granulation can increase density from around 1.1 to 1.7, and particles from 0.5mm to 2.5-4.5mm, without clumping or powdering, suitable for machine sowing.

According to the characteristics of different ammonium sulfate, various combinations of dry rolling granulation processes are adopted:

1. Granulation process of ammonium sulfate by-product from lactam: A granulation unit for ammonium sulfate by-product from lactam has been developed to address its coarse crystal structure and difficulty in forming.

2. Urea ammonium granulation process: In order to increase the nitrogen content, urea is mixed with ammonium sulfate for granulation.