Explosion-proof control measures for production of ammonia

Explosion-proof control of ammonium nitrate compound fertilizer production line under high-temperature seasons

Introduction: safe production of ammonium nitrate compound fertilizer

In the high-temperature season, the production of ammonium nitrate compound fertilizer using high tower granulation has certain risks, because the raw materials of ammonium nitrate compound fertilizer are very sensitive to temperature during processing. When the temperature is too high, it is easy to explode. So how to ensure safe production in the high-temperature season? Very important. This article will introduce how to safely produce ammonium nitrate compound fertilizer during high temperature seasons and some equipment parameters that need to be paid attention to, so as to prevent accidents and ensure the safety of operators.

What are the effects of high temperature on the raw materials of nitro compound fertilizer?

The hygroscopic point of most compound fertilizer raw materials is around 80% (relative humidity). However, high temperature seasons are often accompanied by rainfall, so the raw materials have high humidity and strong hygroscopicity, which may cause blockage of the loading and unloading chutes or chute pipes, and the silo Bonding and clogging of trommel screens and vibrating screens. If any of the above blocks, a explosion might occur.

How to solve the problem of nitro compound fertilizer sticking in high temperature season and prevent ecplosion?

Use nitro raw materials with low moisture content to dry and use the nitro raw materials with high original moisture content. At present, the raw materials with higher moisture content in the three towers of the nitro compound fertilizer device are mainly monoammonium phosphate, which has increased There is a drying device, the urea-based compound fertilizer adopts a double-spiral drying device, and the nitro-based compound fertilizer adopts a drum drying device.
Regularly check the feeding slides, feeding openings, silos, etc. of each nitro raw material, and clean them regularly, ensuring they are cleaned once per shift.
(3) Purchase imported low-moisture potassium chloride from June to September to prevent system clogging. The domestic moisture content is 0.6-1.0%, and the imported moisture content is 0.1-0.3%.
The moisture content of other raw materials must be strictly controlled to ensure that the raw material system is normal. Generally, the moisture content is required to be below 0.5%. The discharge pipe of the monoammonium phosphate drying facility of the urethane tower is easily blocked, which may cause system impact. We need to pay more attention to it. We plan to add vibration to the discharge port to prevent blockage and explosion.

The impact of high-temperature seasons on nitro powder flow cooler:

The nitro compound fertilizer plant uses a new type of powder flow cooler to cool the compound fertilizer material. The cooling effect is good, but it is prone to scarring, causing blockage of the powder flow. The most obvious blockage is the middle section, which leads to Hazards of clogging and explosion.

High temperature control measures for powder flow coolers:

In the high-temperature season in the south, it is recommended to add dehumidified air and compressed air (heating) into the powder flow to take away the high temperature and high humidity air around the compound fertilizer to ensure that the air in the powder flow does not reach the dew point.
Clean the powder flow regularly during high-temperature seasons, and clean the powder flow according to scaling conditions to ensure the heat exchange effect.
Adjust the cold water indicator to ensure that the air in the powder flow does not reach the dew point temperature.
During the high-temperature season, the internal compressed air supply of the powder flow cooler of the nitro compound fertilizer production line is insufficient, the pressure is small (1000pa), and the distribution is uneven. As a result, the dehumidified air in the powder flow cannot reach every corner of the powder flow. It is planned to A pressurized fan is added to the dehumidifier outlet.

Transportation and storage of ammonium nitrate compound fertilizer and finished compound fertilizer in high-temperature seasons:

In summer, after the ammonium nitrate raw material is melted and granulated into compound fertilizer, its hygroscopicity will greatly increase. The hygroscopic point is about 50% (relative humidity). Therefore, when the air humidity is high, it is easy to absorb moisture, causing the surface of the fertilizer to become wet. (As if there is water), it is difficult for the material to flow, causing blockage and pollution in the transportation link.

How to solve the problem of poor circulation of ammonium nitrate compound fertilizer raw materials in summer:

Dehumidified air is added to the belt corridor. 45,000 cubic meters of dehumidifiers have been added to the belt corridor. After dehumidification, the air humidity is around 35%.
Clean the floor materials in time to prevent the ground materials from absorbing water and causing the ground to become slippery, which will affect the conveyed materials and the environment.
Convey dehumidified air into the phosphate fertilizer finished product elevator, organic fertilizer finished product silo, and compound fertilizer trommel screen to reduce the contact between the powder material and the moist air during the flow, causing moisture absorption and affecting the material flow. At present, the introduction of dehumidified air has been completed.
Seal the powder flow, elevator, coating machine, and finished product silo to ensure that moist air cannot enter.

How to solve the problem of wet ground in compound fertilizer workshop in summer

When parking for maintenance and when the weather is humid, the ground and belts will be slippery. According to the hygroscopicity of fertilizers, the compound fertilizer dropped on the ground absorbs moisture and melts, causing the ground to be slippery and accumulate water (the compound fertilizer absorbs moisture and eventually forms a compound fertilizer aqueous solution).

Treat solid particle leakage points in the system to prevent material leakage.
Use semi-hydrated gypsum to clean the ground.
Clean the system before driving, and clean the “water” on the ground and equipment before driving.

Problems with powder flow coolers in summer:

When cleaning the powder flow cooler, the material takes a bypass. During this period, the material temperature is high and it is easy to agglomerate, causing quality risks. The solution is to add a backup powder flow to each existing powder flow equipment and install a lithium bromide unit to reduce the problem. The burden of powder flow fully water-soluble high-tower compound fertilizer cooler.

Operation status of lithium bromide unit

The lithium bromide unit of the nitro compound fertilizer plant was installed in May. The lithium bromide unit was systematically cleaned, debugged and tested. It was officially put into operation on May 28. During the operation, the indicators were explored and the unit is currently operating stably and can meet production needs.
Operation status of lithium bromide unit of nitro compound fertilizer plant:

Unit design: cooling capacity: cold water outlet temperature 15 degrees. The temperature of warm water inlet and outlet is 110/80 degrees. After using the unit, the temperature of the compound fertilizer dropped to below 32 degrees.
Unit operation: cold water outlet temperature is 26 degrees. The temperature of warm water inlet and outlet is 90/80 degrees. The adjustment of unit operating data is mainly due to the rainy and hot weather in summer. If the cold water temperature is too low, the air in the powder flow will reach the dew point and compound fertilizer will be used to absorb water. Therefore, the water temperature is adjusted to 25-30 degrees. Currently, a system is developed to heat the compound fertilizer. Lowered to 31 degrees, two sets can reduce the material temperature to between 30-35 degrees to meet production needs.

Comparison of the operation of the powder flow cooler before and after dark installation of the lithium bromide unit:

Before	After
The circulating water temperature is 35-38 degrees, and the compound fertilizer temperature is 42-48 degrees.	The cold water temperature is 25-30 degrees, and the compound fertilizer temperature is 31-35 degrees.

What is the working principle of the lithium bromide unit, and how does it help the powder flow cooler to reduce the temperature?

The internal circulation of the hot water two-stage machine consists of two independent systems. Each independent system contains the following circulation process: the dilute solution in the absorber is sent to the generator by the solution pump and flows through the heat exchanger on the way.
The dilute solution entering the generator is heated by the heat of the hot water in the tube, generating refrigerant vapor and concentrating into a concentrated solution. The concentrated solution flows through the heat transfer tubes of the heat exchanger, and the dilute solution in the heating tube flows to the generator. After the temperature drops, it enters the absorber.
The refrigerant steam generated by the generator enters the condenser, and the refrigerant water condensed by the cooling water flows into the evaporator liquid bag through the U-shaped tube, and then is sent to the spray system on the upper part of the evaporator through the refrigerant pump, and is sprayed evenly on the transmission line. The surface of the heat pipe absorbs the heat of the cold water in the pipe and evaporates.
The generated refrigerant vapor enters the absorber and is absorbed by the concentrated solution. After being absorbed, the refrigerant vapor releases a large amount of heat energy and is taken away by the cooling water. The concentrated solution absorbs water vapor and becomes a dilute solution, which is then sent to the generator by the solution pump. This process circulates continuously, and the evaporator continuously produces cold water.
The external circulation system of the hot water two-stage machine: includes three systems: hot water, cold water, and cooling water. Hot water enters from the high temperature section and exits from the low temperature section. Cold water enters from the high temperature section and exits from the low temperature section. The cooling water enters from the low temperature section and exits from the high temperature section. This system can effectively reduce the impact of high temperatures in summer on the powder flow cooler.