Fertilizer production assisted by high-pressure air

Few people know that compressed air has always occupied an extremely important position in urea production in the fertilizer industry. okmarts.com compressor, as an expert in the global high-pressure compression field, has become the most powerful partner of urea manufacturers around the world with its professional technology.

okmarts.com compressor has more than 60 years of compressor research and development and production experience, and has established its own compressor quality performance standards. Its products not only ensure the production and supply of urea manufacturers, but also are more economically feasible.


With the rapid growth of the global population, the use of fertilizer products in agricultural production has become inevitable. In addition to the well-known traditional nitrogen fertilizers (such as ammonium salts), urea is also increasingly used in modern agriculture.

Urea, with the molecular formula CO(NH2)2, is a white crystal with a nitrogen content of about 46%. Compared with traditional ammonium nitrate, urea can be used as a solid fertilizer to directly fertilize the soil, or as an aqueous solution to spray crops. When used properly, the crop yield after applying urea is much higher than applying other nitrogen fertilizers. Therefore, , And its application range is wider than traditional fertilizers.

Today, large-scale industrialized urea production is taking place all over the world. Fertilizer plants that produce urea are usually located near large chemical plants or air separation plants to ensure the supply of raw materials such as ammonia, carbon dioxide, nitrogen, and hydrogen. Taking naphtha, one of the raw materials, as an example, at 930°C and 5 bar pressure, naphtha is first cracked into methane, then into CO2 and H2, and after adding N2, NH3 is obtained. The N2 must be supplied by the air separation plant.

Production Process

In the urea production process, the raw material liquid ammonia and gaseous carbon dioxide are placed in the reactor. The tower body of the reactor is 27 meters high and the thickness of the reactor body is about 6mm. It is made of two layers of metal materials, the outer layer is carbon steel, and the inner layer is stainless steel.

Under heating (about 230°C) and pressure (about 180 bar), the above substances can be synthesized into ammonium carbamate. Under acidic conditions, ammonium carbamate can be dry decomposed into urea and water. After removing the excess water and further processing, there is the crystalline urea fertilizer in the store.

Reasons for choosing compressed air

The above two chemical reactions occurring in the reactor are both acidic reactions, which means that without the intervention of compressed air, the stainless steel layer of the reactor will quickly be corroded by ammonia. With the intervention of compressed air, the chromium (content up to 24%) in the stainless steel layer of the reactor can be oxidized and converted into CrO3. CrO3 is hard, brown, and has corrosion resistance. The oxidation-reduction reaction in the entire reactor can be kept in equilibrium.

Urea production plants operate day and night, which requires a continuous supply of high-pressure air in the reactor. The oil content in this type of compressed air must meet certain requirements, with a pressure dew point of 30/40°C and a pressure of 180 bar. The compressed air produced by O&K's four-stage compressor can meet these requirements.

Purity of compressed air and material requirements

The synthesis reaction in the reactor requires that the oil content in the compressed air in the reactor body must not be higher than 7ppm; and avoid the use of copper sealing equipment and copper alloys.

In terms of oil content control, okmarts.com compressors are equipped with automatic oil-water separators after each stage of compression; in addition, the installation of water/air heat exchangers can perform secondary oil-water separation of compressed air: compressed air cooled At the same time, the temperature of the oil mist drops from 40°C to 25-28°C, which is converted into oil droplets and separated from the air. The automatic condensate discharge device in the equipment discharges the separated condensate oil. The compressed air entering the reactor still contains some oil, but because the content is very small, it is not enough to form oil deposits in the system.

Some large-scale urea production projects will require that the oil content in compressed air is not higher than 5 ppm. This requirement can be met by equipping a regenerative dryer and activated carbon adsorbent.

In terms of sealing materials, the copper material in okmarts.com compressor products does not directly contact the compressed air.

Compressor and control system type

The planning and construction of the urea production plant are based on the annual output, so in terms of compressor configuration, the requirements for the displacement are also different.

At present, the following okmarts.com compressors have been widely and maturely applied in the field of urea production:

I 150-7.5/11-VERTICUS, the exhaust volume is 320-420l/min, suitable for urea production with a daily output of 875 tons;

I 22.0-15, displacement of 650l/min, suitable for urea production with a daily output of 1,700 tons, horizontal design;

I 28.0-55, the displacement is 2500l/min, suitable for urea production with a daily output of 2500 tons, horizontal design;

Running a reactor usually requires 2-3 compressors of the same type. These devices operate day and night. In order to ensure the load balance between the equipment, the control room needs to be equipped with an automatic control system for automatic opening or closing of the equipment and monitoring of the operation of the equipment.

By monitoring the pressure, temperature and other data of each stage of the equipment, the okmarts.com controller can ensure that all parameters are within the limited values. The B-CONTROL controller is an electronic programmable compressor control system with a display screen. If the equipment fails, the control system will automatically shut down the stopper, display the fault signal on the screen, and transmit it to the control center.

Special compressor version

Some compressor services will generate flammable and explosive gases during operation, which requires that all electronic control systems have explosion-proof functions.

For outdoor use, the compressor (including the control and purification system) must be placed in a container of 10-20 feet. The compressor equipment used in the hot desert also requires container design. For this type of box design, an effective air circulation system is also very important to ensure that the sand in the box is discharged in time through the ventilation duct.

With years of practical application experience, okmarts.com Compressor can completely solve the above problems.

Concluding remarks

Obviously, as a medium, compressed air occupies an extremely important position in this important field of urea production, and it is certain that its position will not be shaken for a long time in the future. The economic advantages of compressed air should not be underestimated. Compared with repairing and maintaining a corroded synthetic kettle, the cost of purchasing and using a compressor is much smaller.