Usage of level gauges in the gasifier quench chamber and scrubber tower
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There are many discussions and papers online regarding the quench chambers of gasification furnaces and the level gauges in scrubber towers, but few companies seem to achieve good performance with them. Our company uses Texaco’s multi-material slurry gasification technology, with a gasifier pressure of around 65 KG. The liquid level in the quench chamber is monitored using three double-flange differential pressure transmitters; approximately 80 KG of flushing water is added through a flushing ring before the pressure-taking connections. Due to hydrogen penetration, chloride corrosion, and erosion by washing water, within just over a year of operation, the diaphragms of the level transmitters in this area would bubble or rupture after two to three cycles of pressure measurement, preventing the interlock system from functioning continuously... Both ordinary diaphragms and gold-plated diaphragms were tried, but neither yielded satisfactory results. Due to inaccurate liquid level measurement in the scrubber tower, water contamination in the raw gas has occurred on multiple occasions... Recently, the pressure tapping points in the scrubber tower have been extended to increase the distance between the flushing water and the transmitter diaphragm box. I’m not sure about the performance of these instruments in various units – what brand of transmitters are being used? Are there any good measures or suggestions?
If the differential pressure method doesn’t work, should we try another approach?
It is said that a certain foreign manufacturer has radar level gauges of this type, but the patented technology is used in urea plants.
Rosemount’s double-flange differential pressure transmitters, with their diamond-like diaphragms, can be used over the long term for measuring liquid levels in the quench chamber of vaporization furnaces as well as black water flow rates. The maximum usage time for the black water flow is one and a half years
Our BGL feels pretty good
At present, our plant’s vaporization furnaces use Rosemount 3051 double-flange transmitters; however, the diaphragms in these devices accumulate carbon deposits, so they need to be cleaned regularly
I fully agree with you; due to factors such as hydrogen permeation, chloride ion corrosion, and erosion by washing water, the pressure diaphragm of the level transmitter will bubble or rupture after two to three cycles, preventing the interlock system from remaining operational continuously. In fact, double-flange differential pressure transmitters are not necessarily the best choice; in many situations they are less effective than regular differential pressure transmitters. I have conducted experiments in this area, and the key is to take certain measures. I suggest switching to a differential pressure transmitter, along with a minor backflow prevention mechanism (including automatic and manual functions), which can solve these problems. Of course, a measurement plan needs to be designed based on the specific conditions at the site. This enables the transmitter to operate for long periods of time, while also simplifying and facilitating maintenance.
Double-flange transmitters do indeed have many problems related to penetration, ion corrosion, erosion by flushing water, diaphragm coking, and so on； Furthermore, the service life of double-flange transmitters is shorter than that of ordinary transmitters; they are more difficult to replace, and the replacement cost is also higher. So I still recommend using a regular differential pressure transmitter. Of course, this requires a minimal recoil mechanism. This facility is shared by multiple level gauges.
We use four-nozzle water-coal slurry gasifiers; for the level gauges, we have used both gold-plated and diamond ones, and in either case they need to be replaced every 3 to 6 months