The closed cycle spray drying tower (also known as organic solvent spray drying system) needs to strictly follow the safety operation procedures because of its particularity in handling flammable and explosive solvents. The following is a summary of key precautions:
1、 Safety preparation before operation
1. Environmental and equipment inspection
Confirm that the explosion-proof level meets the Class II area standard, the exhaust volume of the ventilation system is ≥ 20 times/hour, and the error of the combustible gas alarm is ≤± 3%.
The grounding resistance of the equipment must be less than 4 Ω, and the operator must wear anti-static clothing (resistance 10 ^ 7-10 ^ 9 Ω). The environmental humidity should be controlled at 45% -65%.
The nitrogen pressure holding method is used to test the sealing performance of the solvent system, and the pressure drop does not exceed 5% within 30 minutes.
2. Solvent and Explosion proof System Verification
The solvent recovery condenser needs to be pre cooled to below -20 ℃ to ensure a condensation efficiency of>85%.
Test the linkage response time between the oxygen content analyzer (alarm value ≤ 8% VOL) and the nitrogen protection system, with a requirement of ≤ 3 seconds.
2、 Key points of control during the operation phase
1. Dynamic parameter adjustment
The inlet air temperature needs to be strictly controlled: ethanol ≤ 120 ± 2 ℃, ethyl acetate ≤ 90 ± 2 ℃, temperature fluctuation<1%.
The formula for matching atomization pressure and feed rate is Q=0.78 × d ² × √ (2 Δ P/ρ) to prevent incomplete atomization from causing wet powder accumulation.
2. Safe operation window
The solvent concentration temperature pressure should be controlled below 25% of the lower explosive limit (LEL), and the system pressure should be maintained at a slight negative pressure of -50 to -100Pa.
Record oxygen content (≤ 5%), solvent recovery rate (≥ 92%), and bag filter pressure difference (<800Pa) every 30 minutes.
3、 Exception handling and maintenance
1. Emergency response measures
When the oxygen content is greater than 10%, the nitrogen emergency filling valve (flow rate ≥ 50m ³/h) will be triggered within 5 seconds.
When the temperature exceeds the limit, the heating power will be automatically cut off and the emergency solvent discharge valve will be activated to the accident storage tank.
2. Regular maintenance requirements
Monthly testing of the coating resistance on the inner wall of the tower (<10 ^ 6 Ω) and flange cross connection resistance<0.03 Ω.
Replace the conductive grease (resistivity 10 ^ 3-10 ^ 5 Ω· cm) every 500 hours for the bearings of the rotary atomizer.
4、 General safety regulations
1. Before operation, it is necessary to check the status of the atomizer, fan, heating system, and dust removal device to ensure that there are no leaks.
2. When handling organic solvents, a nitrogen sealed circulation system must be used and explosion-proof devices must be installed.
3. Do not open the maintenance door or touch rotating parts during operation. After shutdown, wait for the tower temperature to drop below 80 ℃ before turning off the heating system.
The above measures combine equipment safety, process control and emergency management, which can effectively reduce the operational risk of closed cycle spray drying tower.