How to calculate the ventilation rate of explosion-proof ventilation system in MIBK storage warehouse?

Safety knowledge

April 18, 2025

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MIBK (methyl isobutyl ketone) is a kind of flammable and explosive chemical raw material, which is widely used in paint, plastic and rubber fields. Due to its flammable and explosive characteristics, the safety requirements of the storage warehouse are very high. Among them, the explosion-proof ventilation system is one of the important facilities to ensure the safety of the warehouse, and the calculation of the number of ventilation is particularly critical. This paper will analyze the calculation method of the ventilation rate of MIBK storage warehouse explosion-proof ventilation system in detail.

1. The nature of MIBK and ventilation requirements

MIBK is a colorless liquid with a low lower explosive limit (LC5 ≥ 0.7%) and readily forms a flammable mixture in air. Therefore, during storage, it must be ensured that the concentration of MIBK vapor in the warehouse does not reach the explosive limit. The main function of the explosion-proof ventilation system is to reduce the concentration of MIBK vapor in the air and prevent the occurrence of explosion accidents.

2. Definition and calculation basis of ventilation frequency

the number of air changes refers to the number of times the air in the warehouse is completely replaced per unit time. In the design of explosion-proof ventilation system, the calculation of the number of air changes needs to be based on the following factors:

gas release amount: The amount of vapor release of MIBK is related to its storage and volatilization rate.
Warehouse volume: The volume of the warehouse directly affects the number of air changes. The larger the volume, the more air changes are required.
Gas Density and Diffusion Characteristics: The density and diffusion speed of MIBK vapor also affect the number of air changes.

3. The calculation steps of the number of air changes.

In order to calculate the number of air changes of the explosion-proof ventilation system of the MIBK storage warehouse, the following steps can be followed:

step 1: Determine the amount of MIBK vapor released

the amount of MIBK vapor released is closely related to its storage and volatilization rate. In general, MIBK volatilizes faster, and its vapor concentration needs to be monitored regularly during storage. Assuming that the total amount of MIBK stored in the warehouse is G(kg), the amount of vapor release can be determined by experiments or related standards.

Step 2: Calculate the volume of the warehouse

the volume V (cubic meters) of the warehouse can be calculated by length × width × height. Assuming that the length, width and height of the warehouse are L, W and H respectively, then the volume V = L×W×H.

Step 3: Determine the formula for calculating the number of air changes.

The number of air changes (N) can be calculated by the following formula:

[ N = \frac{\text {gas release }}{\ text {warehouse volume}} \times \text {ventilation factor} ]

among them, the ventilation coefficient is usually 1.5-3, and the specific value needs to be determined according to the tightness and ventilation design of the warehouse.

Step 4: Refer to industry standards and specifications

in the actual design, the calculation of the number of ventilation also needs to refer to the relevant industry standards and specifications. For example, HG/T 3657-2006 "Chemical Warehouse Design Code" stipulates that the ventilation rate of flammable liquid storage warehouse should not be less than 3 times/hour. For flammable gases such as MIBK, the recommended number of air changes is not less than 5 times/hour.

4. Practical case analysis

assume that the volume of a MIBK storage warehouse is 1000 cubic meters and the total amount of MIBK stored is 500kg. According to the experimental data, the vapor release of MIBK is 200 g/h. Then the number of air changes is calculated as follows:

vapor release was 200 g/h and warehouse volume was 1000 m3.
Assuming a ventilation coefficient of 3, then the number of ventilation N = (200/1000) × 3 ≈ 0.6 times/hour.

According to the requirements of HG/T 3657-2006, the ventilation rate shall not be less than 3 times/hour. Therefore, in the actual design, it is necessary to further optimize the ventilation system and increase the number of air changes.

5. Summary and recommendations

the calculation of the ventilation rate of the explosion-proof ventilation system of the MIBK storage warehouse requires comprehensive consideration of factors such as gas release, warehouse volume and ventilation coefficient. The design should be carried out in strict accordance with relevant industry standards and specifications, and adjusted according to the actual situation. It is recommended to regularly check and maintain the ventilation system to ensure its normal operation, so as to ensure the safety of the warehouse.