Problems existing in the storage process of ammonium nitrate and suggestions for improvement

Ammonium nitrate (NH ⁴ NO ³ ) has a relative molecular weight of 80.
05, a theoretical nitrogen content of 34.
98%, a melting point of 169.
6 °C, and will decompose at 210 °C
.
Its physical and chemical properties are: the pure product is colorless and odorless transparent crystals or small white particles, with deliquescence; strong oxidizing agents, mixed with reducing agents, organic substances, flammable substances such as sulfur, phosphorus or metal powders can form explosive Mixture; combustion-supporting; it will explode when mixed with flammable (combustible) materials or heated rapidly; it will also explode when subjected to strong vibration
.
Ammonium nitrate is mainly used as fertilizer, analytical reagent, oxidant, refrigerant, pyrotechnic and explosive raw material
.

According to public statistical reports, there have been at least 5 explosion accidents in the storage of ammonium nitrate at home and abroad:

In 1993 Qingshuihe "8.
5" dangerous goods warehouse explosion accident, the dangerous goods warehouse co-stored 49.
6 tons of porous ammonium nitrate and 15.
75 tons of ammonium nitrate
.
The accident resulted in the death of 15 people, the injury of more than 800 people, the destruction of 39,000 square meters of buildings, and the direct economic loss of 250 million yuan
.

In 2001, the AZF factory in Toulouse, France, exploded, and a large-scale explosion occurred in a warehouse storing 200-300 tons of bulk ammonium nitrate, causing 30 deaths and 2,500 injuries
.
In the accident, several kilograms of sodium dichloroisocyanurate mixed with 500 kilograms of ammonium nitrate on the ground, resulting in a chemical reaction that caused a strong explosion of ammonium nitrate
.

In 2013, the "4.
17" explosion accident of a fertilizer plant in Vico, Texas, USA, a fire broke out in a fertilizer plant that stored and sold ammonium nitrate in West Texas.
The fire caused the stored ammonium nitrate to explode, causing the accident 15 people were killed, 260 people were injured, and 150 buildings outside the factory were damaged
.
A 2016 CSB accident report attributed the accident to a wood-structured ammonium nitrate warehouse, construction materials and a lack of a proper automatic sprinkler system
.

At around 23:30 on August 12, 2015, a fire and explosion accident occurred in the warehouse of Ruihai Company, located in Tianjin Port, Binhai New Area, Tianjin City, where a variety of dangerous goods (including 800 tons of ammonium nitrate) were stored.
The accident caused 165 deaths and 8 missing.
, 789 people were injured, 304 buildings, 12,428 commercial vehicles, 7,533 containers were damaged, and the direct economic loss reached 6.
866 billion yuan
.

At around 18:00 on August 4, 2020, a huge explosion occurred at the port of Beirut, the capital of Lebanon, with a total of about 2,750 tons of ammonium nitrate
.
As of August 30, 2020, 190 people were killed, 6,500 were injured, and 3 people were missing
.

There are relatively few accidents involving ammonium nitrate in history, but the social impact of accidents is great, and most of them have catastrophic consequences
.
On September 26, 2021, the Ministry of Emergency Management, the Ministry of Industry and Information Technology, the Ministry of Public Security, the Ministry of Transport, and the General Administration of Customs jointly issued the "Notice on Further Strengthening the Safety Management of Ammonium Nitrate" (Emergency [2021] 64 No.
) to further deepen the safety supervision of ammonium nitrate
.
On February 15, 2022, the First Division of Hazardous Chemical Supervision of the Ministry of Emergency Management issued the "Notice on Carrying out Special Governance of Security Risks in High-risk Subdivisions", and also announced the work plan and guidelines for 6 subdivisions, of which the first The guide is the "Guidelines for Special Safety Risk Investigation of Ammonium Nitrate Production Enterprises (Trial)", which is used to guide ammonium nitrate production enterprises to carry out safety risk investigation and assessment and classification of ammonium nitrate production and storage processes
.

Through the recent safety inspection of ammonium nitrate production enterprises, the problems existing in the storage of solid ammonium nitrate are summarized, which can be roughly divided into the following seven problems:

(1) The external safety protection distance assessment does not meet the requirements

First, there is a deviation in the enterprise's understanding of the maximum amount of storage of solid ammonium nitrate, and the production and storage facilities have not been evaluated as a whole for the external safety protection distance; Requirements for Risk Benchmarks of Production Installations and Storage Facilities of Hazardous Chemicals (GB 36894) and Determination of External Safety Protection Distances of Production Installations and Storage Facilities of Hazardous Chemicals (GB/T 37243) (hereinafter referred to as "two standards"); Third, when evaluating the external safety protection distance, the facilities or places around the ammonium nitrate warehouse were not fully identified, and not all were listed as protection targets
.

(2) The risk management and control of the recycling and disposal of ammonium nitrate (sweeping materials, "unqualified" products, etc.
) is not in place

The enterprise did not set up a special warehouse for ammonium nitrate (sweeping materials, "unqualified" products, etc.
), and temporarily stored it in the ammonium nitrate warehouse in violation of regulations; nor did it manage the temporary warehouse in accordance with the relevant storage requirements for explosive hazardous chemicals, and follow " The accident consequence method in the “Two Standards” calculates the external safety protection distance; some enterprises send unqualified ammonium nitrate to the accident pool for recycling and reproduction, and do not analyze and monitor the content of impurities such as chloride ions and oils in the reused unqualified products
.

(3) The designed storage capacity of a single warehouse of ammonium nitrate does not meet the requirements, and excessive storage

The enterprise has not conducted in-depth study and research on the terms in the "Guidelines for the Investigation of Special Safety Risks of Ammonium Nitrate Production Enterprises (Trial)", and there is a deviation in the understanding of the terms
.
For example, the "Guide" requires that the storage capacity of a single ammonium nitrate warehouse should be no more than 500 tons.
A professional from an enterprise misunderstood the concept of a single warehouse.
The ammonium nitrate warehouse is divided into 3 fire compartments, and the maximum storage capacity of ammonium nitrate in each fire compartment is 500 tons, resulting in a maximum storage capacity of 1,500 tons in the entire ammonium nitrate warehouse, which is inconsistent with the requirements of the Guidelines
.

(4) The fire separation distance of the ammonium nitrate warehouse does not meet the requirements

There are production devices or storage facilities involving inflammable and explosive materials within 50m around the ammonium nitrate solid warehouse of the enterprise.
For example, the distance between the ammonium nitrate warehouse and the ammonium nitrate crystallization workshop and the liquid ammonium nitrate production device is less than 50m
.

(5) The fire resistance grade of the ammonium nitrate warehouse building does not meet the requirements

The doors and windows of the ammonium nitrate warehouse are ordinary doors and windows, and there are no Class A fire doors and windows, and their fire resistance integrity and thermal insulation do not meet the fire protection requirements
.

(6) The ammonium nitrate warehouse is not equipped with relevant monitoring alarms, video surveillance, spray cooling, ventilation and other safety facilities

The inspection found that some enterprises' ammonium nitrate warehouses did not set far-infrared thermal imaging monitoring alarms, flame video recognition alarms, and did not set up over-temperature segmented forced ventilation or outdoor spray cooling facilities; the main valve of the spray water pipeline in the ammonium nitrate warehouse of an enterprise .
The branch valve of the pipeline is in the closed state, which cannot play the role of emergency response; the buzzer of the monitoring alarm of an enterprise is in the closed state, and the post personnel cannot find it in time when the alarm is issued
.

(7) Irregular fire management in ammonium nitrate warehouses

The hot work in the ammonium nitrate warehouse of some enterprises does not meet the requirements of GB30871, and there are problems such as irregular filling of hot work tickets, and hot work in the ammonium nitrate warehouse if the ammonium nitrate in the warehouse is not emptied
.

Therefore, based on the above analysis, the author believes that the safety risk control of ammonium nitrate warehouses can be further strengthened from the following aspects:

(1) Strengthen the publicity and training of standards and norms, and organize the study of the "Notice on Further Strengthening the Safety Management of Ammonium Nitrate" (Jiangong [2021] No.
64) "Guidelines for the Investigation of Special Safety Risks in Ammonium Nitrate Production Enterprises (Trial)" and other documents , standard, and comprehensively improve the knowledge and skills of safety management personnel and operators
.
Accurately identify and scientifically manage and control the safety risks of ammonium nitrate storage, and timely investigate and control hidden dangers, so as to effectively prevent and control major risks
.

(2) Accelerate the popularization and application of ammonium nitrate external safety protection distance evaluation software.
According to the requirements of the "two standards", evaluate the internal and external safety protection distance of ammonium nitrate enterprises, and calculate the maximum storage capacity of ammonium nitrate
.
For ammonium nitrate warehouses that store explosives in the dangerous category, and warehouses for storing substandard ammonium nitrate products, the external safety protection distance shall be determined according to the accident consequences method; other ammonium nitrate production devices and storage facilities shall be calculated according to the quantitative risk assessment method
.
When using the accident consequence method and the quantitative risk calculation method at the same time, the external safety protection distance determined by the two methods should be satisfied at the same time
.
When determining the external safety protection distance, quantitative risk assessment should be carried out on all hazardous chemical production devices and storage facilities in the enterprise as a whole
.

(3) According to the requirements of the "Guidelines", solid ammonium nitrate warehouses should be included in the management of major hazard sources regardless of whether they are enough to become a major hazard source
.
Fill in the relevant information of major hazard sources through the hazardous chemicals registration information management system, and connect the safety monitoring and monitoring data of major hazard sources to the hazardous chemicals safety production risk monitoring and early warning system as required
.

(4) The solid ammonium nitrate warehouse is equipped with complete safety facilities
.
For example: install fire-fighting water system, equipped with appropriate portable fire extinguishers, must ensure that fire-fighting facilities are completely put into use; improve safety facilities such as forced ventilation, far-infrared thermal imaging monitoring and alarm, spray cooling and video surveillance in the warehouse, and set up flame video recognition outside the warehouse Alarm and other security facilities
.

(5) Strengthen the fire prevention management of solid ammonium nitrate warehouses
.
First, in terms of building fire protection, in accordance with the requirements of "Code for Fire Protection in Architectural Design (2018 Edition)" (GB50016), it is designed according to Class A warehouses, built independently on a single floor, adopts a closed structure, and has a fire resistance rating of not lower than Class II; Class A fireproof doors and windows are set up.

.
The maximum allowable area of ​​each warehouse is 1500 square meters, and the maximum allowable construction area of ​​the fire compartment is 500 square meters
.
Second, in terms of hot work, strictly implement the "Safety Regulations for Special Operations of Hazardous Chemical Enterprises" (GB 30871-2022).
The hot work in the warehouse should be videotaped and kept for at least one month, and no hot work should be carried out in the warehouse that is not emptied.
homework
.
Motor vehicles entering the ammonium nitrate warehouse for operation should be equipped with flame arresters, and battery vehicles should be explosion-proof
.

(6) Strengthen the safety management of solid ammonium nitrate storage
.
The first is to further improve the storage conditions of solid ammonium nitrate warehouses.
According to the provisions of 7.
1.
3 of the "Safety Standards for Civil Explosive Items Engineering Design (GB50089)", the storage capacity of a single warehouse shall not exceed 500 tons, and inflammable and explosive materials shall not be stored around the warehouse (50m).
, No production equipment and storage facilities involving inflammable and explosive materials shall be built
.
If the external and internal safety distances meet the requirements, the total maximum storage capacity of multiple warehouses shall not exceed 2500t
.
Second, the storage management of ammonium nitrate should meet the requirements of GB15603, GB17914, etc.
It should be stored in a special warehouse.
Excessive storage is strictly prohibited.
Contact with incompatible organic substances, etc.
, bulk storage and open storage are strictly prohibited
.

(7) Ammonium nitrate production enterprises shall, in accordance with the requirements of the "Notice on Further Strengthening the Safety Management of Ammonium Nitrate" (Emergency [2021] No.
64), implement the supporting construction of nitro compound fertilizers and ammonium nitrate solutions that match the production capacity of solid ammonium nitrate.
Requirements for peak shaving devices or capacity diversion facilities, the design capacity of peak shaving devices or diversion facilities should be able to effectively balance the production and sales of solid ammonium nitrate and avoid excessive storage of solid ammonium nitrate
.

(8) Improve emergency support capabilities
.
One is the establishment of emergency plan system
.
Prepare a special plan for potential fire and explosion accidents during the production and storage of ammonium nitrate
.
The second is to provide emergency equipment and equipment to deal with ammonium nitrate accidents
.
The third is the configuration of emergency personnel and capabilities
.
Set up full-time fire brigade or micro fire station, process disposal team, strengthen on-duty duty, and improve their ability to deal with disaster accidents
.