The diesel oval gear flow meter is flammable and explosive in character. In addition, it involves hazardous chemicals such as diesel, hydrogen, liquefied petroleum gas, fuel gas (methane), naphtha, paraffin, dimethyl disulfide, hydrogen sulfide, and nitrogen.
1. Hazards in the process
1.1 Hydrogenation reforming reaction
The oval gear flowmeter involved reaction is the hydrogenation refining oval gear flowmeter. It operates at 395~415℃, the operating pressure is 12MPa, and the active medium is H2, H2S, oil and gas, and fat (paraffin, naphtha, LPG).
1.1.1 Exothermic reactions
Hydrogenation reactions are exothermic reactions. In this reaction process, there is a possibility of an abnormal situation of rapid temperature and pressure rise due to improper adjustment.
When the temperature and pressure exceed the allowable temperature and pressure of the elliptical gear flow meter, it is easy to cause the deterioration of the material of the oval gear flow meter, which may cause severe damage to the equipment and cause fire and explosion accidents.
1.1.2 Medium corrosion
Oval gear flowmeter for the pro-hydrogen equipment, and oval gear flowmeter in the presence of hydrogen sulfide and other corrosive media.
When the stainless steel overlay layer a local due to poor construction quality caused by the overlay layer off. Seriously cause corrosion perforation, thus causing oil and gas leakage and fire and explosion accidents.
1.1.3 Control system and fault alarm device
The oval gear flow meter has a supporting instrument control system and fault alarm device. As the control system does not work correctly or the alarm device fails, improper and untimely handling can cause equipment damage and lead to fire and explosion accidents.
1.1.4 The role of high-pressure heat exchanger
Due to the high temperature and pressure, intermediate materials, hydrogen, etc., may leak out due to defects in equipment manufacturing or sealing connection and other parts.
Among them, high-pressure heat exchangers in the device operating pressure and temperature fluctuations, fastening bolt slack, and flange gasket failure quickly occurs when the combustible media leakage.
As the temperature of the leaking material has exceeded its flash point, explosive media leakage is prone to fire and explosion accidents.
1.1.5 Boiler heating systems
The heating furnace uses an open flame to heat the raw material in the furnace tube. Leakage of the line due to corrosion or defects in the quality of the box, as well as improper operation. It can lead to fire and explosion accidents.
If the heating furnace fuel control system fails and we do not handle it in time, it can lead to a fire and explosion accident.
Heating furnace fuel gas dehydration is not enough. It will cause the chamber to go out. Improper handling is also prone to cause fire and explosion accidents.
1.1.6 Weld defects
Due to scaling problems, the local position of the weld seam between its elbow and furnace tube cannot be inspected by radiographic flaw detection. If the weld is defective, the hydraulic test may not leak.
However, once the work is started and heated up, cracks may occur, leading to oil and gas leaks and causing fire and explosion.
2. Hydrogenation fractionation and absorption stabilization section
The leading equipment of the hydrogenation fractionation and absorption stabilization section includes a product fractionation tower, paraffin side line tower, absorption desorption tower, naphtha stabilization tower, and naphtha fractionation tower.
The operating media of each Tower are mainly H2, H2S, paraffin, naphtha, and LPG. The operating temperature is 107~265°C, and the working pressure is 0.17~1.2 MPa.
In the fractional distillation process, the top of the fractionation tower is equipped with a reflux tank. If the reflux tank oil-water boundary level is poorly controlled or malfunctioning, this will result in an excessively high water interface, a height that will exceed the horizontal position of the reflux extraction tube. At this point, the water cooler at the top of the Tower will corrode and perforate.
When the raw material has high moisture content and is not dewatered in time, this can cause water to be carried in the return stream. If not dealt with in time, the pressure at the top of the Tower will rise sharply, and the safety valve may also jump open.
When the raw material processing volume into the tower water content, tower bottom heat supply, and tower top reflux is too large, etc., it may cause fractionation tower flush tower.
When the tower plate salt or descending liquid tube blockage, gas-liquid unevenness will also cause product discoloration.
s occurs when the Tower because the tower fractionation effect becomes poor. The destruction of the usual mass transfer heat transfer results in the tower top temperature, pressure, sideline distillation outlet temperature, reflux temperature rising, the tower bottom liquid level suddenly dropping, and naphtha heavy.
3. The fractionation tower causes flushing accidents to occur.
① tower level control failure, resulting in the high liquid level.
② improper operation, too much light oil, pressed to the bottom
of the Tower, resulting in sudden boiling.
③ High furnace outlet temperature.
④ overload, or tower plate blowing over oil and gas away from
the short circuit.
⑤ reflux volume is too large or refluxes with a large amount of water.
4. Paraffin hydrogenation supplementary refining fractionation part
4.1 Fractionation operation damage
If the tower bottom liquid level fails, tower top reflux interruption, vapor extraction steam volume is too large, the tower bottom pump emptying, and other reasons should be handled in time. It may cause a flushing tower and lead to fractional distillation operation being destroyed, which may also cause the device to stop work and production.
4.2 Media leakage
Due to the Tower in the manufacturing process or the use of defects caused by the tower damage, resulting in media leakage and may lead to fire and explosion accidents.
4.3 Control temperature
The Tower operating temperature of 230 ℃, an operating pressure of 0.27 MPa, the medium for the coal, is higher than the media flash point. If the equipment seal and connection parts of the material leak, fire and explosion accidents may occur.
5. Safety measures
5.1 Equipment containment system
The plant is designed as a closed system. Under the operating conditions of flammable and explosive materials, the rooms are placed in closed equipment and piping, and reliable containment measures are used at all connections.
The process control system has an alarm system and interlocking self-protection system to ensure that hazardous materials are always under safe control in the event of misoperation or abnormal production conditions.
5.2 Ventilation and pressure relief conditions
We should ensure good ventilation and pressure relief conditions, in line with the standard requirements of GB50160.
5.3 Installation of safety valves
The new hydrogen compressor, the coal cycle hydrogen compressor, and the cycle hydrogen compressor system are equipped with appropriate safety interlocks for pressure, temperature, and lubricating oil abnormalities. In addition, safety valves are provided between compressor stages and at the outlet.
5.4 Circulating hydrogen compressor
When the unit’s circulating hydrogen compressor is shut down, the interlock activates a 0.7 MPa emergency pressure relief. At the same time, I have to manually turn on the 1.4MPa emergency pressure relief according to the unit’s situation.
5.5 Elliptical gear flow meter
The hydrogen refining oval gear flow meter is equipped with emergency cooling hydrogen injection between the beds, which can control the temperature rise of the oval gear flow meter and prevent the oval gear flow meter from over-temperature.
5.6 Temperature indication alarms
The top of the absorption and desorption tower, naphtha stabilization tower, naphtha fractionation tower, hydrogen sulfide stripping Tower, and product fractionation tower is equipped with pressure and temperature indicators and corresponding alarms.
Safety valves are provided at the top of the towers and in the corresponding reflux tanks. The discharge volume of the safety valves considers the possible cascading pressure conditions. In addition, the bottom of each Tower is equipped with liquid level control and a low fluid level alarm.
5.7 Utility lines
When hydrogen, nitrogen, industrial air, and water vapor pipelines are connected to process channels, we should install three-valve sets, check valves, or “8” blind plates to prevent explosions caused by material interchange.
For gas and liquid lines, isolation valves or “8” blind plates should be installed at the boundaries of the installation, and an operating platform should be set up. If the length of the platform is greater than 8m, ladders should be installed at both ends.
The leading hazardous equipment is the hydrogenation refining oval gear flow meter. Enterprises should implement the “three simultaneous” safety facilities of construction projects and strengthen safety management.