The core equipment of the coal-water slurry gasification process is the vaporizer. After the coal-water slurry and oxygen have been thoroughly mixed and atomized in the burner, enter the vaporizer’s combustion chamber. The gasification reaction is carried out at a pressure of 6.5 MPa and 1 350 °C. Finally, the combined gas and molten ash are brought down together.
The combined gas and molten ash go downwards together. They pass through a cooling ring with uniformly distributed cooling water and then enter the cooling bath in the cooling chamber along a descending tube. Therefore, the reliability of the level measurement instrumentation in the vaporizer cooling chamber directly impacts the vaporizer’s safe operation. Thus, the magnetic flap level meter is a vital control instrument.
1. vaporizer device magnetic flap level meter prevention countermeasures analysis
1.1 Complex working conditions
The working conditions inside the cooling chamber are complex, and the process conditions are very harsh. Therefore, it has exceptionally high requirements for the performance of the level meter body. Thus, when Jiangsu BCST purchased the level meter, its technical requirements were high temperature, high pressure, hydrogen, vacuum, corrosion, and flushing.
1.2 Anti-vacuum design
The anti-vacuum design diaphragm is fully welded. This means that the connection from the capillary tube to the flange and the link from the membrane head to the capillary tube are all-welded.
1.3 Anti-high temperature design
The anti-high temperature design means that the filling fluid of the diaphragm cassette is selected with a correspondingly high temperature-resistant filling liquid. To prevent hydrogen precipitation corrosion, the transmitter uses a gold-plated diaphragm transmitter. It can reduce the frequent damage to the transmitter due to hydrogen permeation.
Gold plated diaphragms are generally sintered at high temperatures over a long period. It results in a homogeneous, stress-free gold diaphragm layer, significantly reducing the hydrogen diffusion effect. It also greatly extends the service life.
2. Installation matters for the vaporizer
It is not enough to improve the performance of the transmitter itself. For this reason, it is drawing on the continuum principle.
2.1 Material of the balancing cylinder
A balancing cylinder was added to the original measurement port of the vaporizer. The balancing cylinder is made of a 3″ 316 stainless steel pipe. It has to be connected to the flange at the outlet of the process valve, which is made of a 2″ 316 stainless steel pipe.
2.2 Pipeline unblocking
We consider clearing the pipeline and need to add a 1/2″ flushing water pipe to the pressure port for regular flushing, using a blind flange seal at the upper end of the cylinder. Adding a drain valve at the lower back, connecting the flange to the transmitter, and then welding the original pressure port at 90°.
2.3 Role of flushing water
When we add the balancing cylinder, the flushing water will not corrode the membrane box for long or short-term use. At the same time, the flushing water is relatively clean, and a small amount of flushing water can make the lower measuring diaphragm relatively clean.
At the same time, the temperature of the fluid section is significantly lower (approx. 270°C for the fluid in the cooling chamber and approx. 110°C for the flushing water), which results in a relatively low operating temperature of the fluorine oil in the cartridge. It also reduces the corrosion of the membrane cartridge by liquid CI-ions and reduces the problem of leakage in the joint section due to high-temperature changes.
3. Vacuum environment
For the vacuum environment, when we purchase the level meter, technical engineers will require the use of vacuum occasions outside; but also to ensure that when the process baking furnace, close the process valve connected to the remote level meter and vaporization furnace.
Try to avoid the use of vacuum occasions. Instead, the operator can observe the magnetic flap level meter in situ according to the site. It will ensure regular oven drying and extend the service life of the level meter.
4. Magnetic flap level meter inadmissible faults and handling
4.1 Root valve failure
Cause of failure.
① During plant start-up, the vaporizer level meter was inaccurate.
② The site flushing has no effect after stopping the disassembly and Inspection of the liquid level meter calibration qualified.
③ Inspection found that the root valve is faulty. Rotate the root valve handwheel. The valve ball does not move, and the root valve is in the fully closed position, resulting in the liquid level meter display inaccuracy.
When the vaporizer is routinely inspected, we have to replace the valve.
4.2 Plugging of the pressure extraction pipe
Cause of failure
The cooling water in the vaporizer unit is black water with a large amount of ash. Therefore, if the vaporizer telemeter is not flushed regularly, the pressure tube will be easily blocked, resulting in false indications.
During start-up, we should strictly implement the regular flushing system of the vaporizer telemeter. At the same time, during parking, we must clean and unblock the balancing cylinder and the pressure-taking tube to ensure smooth operation.
4.3 Leakage after feeding
Cause of failure
Leaks appear at the pressure port after feeding due to poor fastening during installation.
Close the root valve of the vaporizer level and tighten the leaky flange. If necessary, we will replace the gasket. If the root valve cannot be closed, we must plug the leak with pressure or stop the process.
The liquid level meter in a vaporizer plant is a critical control parameter. It directly affects the safe operation of the vaporizer by implementing the above preventive measures for the vaporizer remote level meter.
It extends the performance and life of the Jiangsu BCST level meter. In addition, it reduces maintenance costs and provides an essential basis for the gasification plant’s safe, stable, and long-cycle operation.