Application and Analysis of Electromagnetic Flowmeter in Coal Water Slurry Pipeline
The accuracy of coal slurry flow measurement directly affects the stable operation of the four-nozzle opposed gasifier and is also a key factor in the production control of syngas produced by the gasifier. The electromagnetic flowmeter used in the three four-nozzle opposed gasifier coal slurry pipeline of a company has a large fluctuation of flow during different periods during operation, and some directly lead to zero flow indication. The instrument personnel conducted on-site inspection: the signal of the excitation coil of the sensor is normal, there is no excessive resistance; the voltage between the two signal lines of the sensor is greater than IV, there is no electrode contamination phenomenon. There is no grounding phenomenon between the two signal lines of the sensor; the electromagnetic flowmeter The internal parameter setting is consistent with the factory checklist, and there is no parameter setting error. *** Finally concluded that the electromagnetic flowmeter measures the internal problems of the pipeline and needs to be dismantled to check the internal conditions of the electromagnetic flowmeter before making further plans. From the results of the dismantling and inspection of the electromagnetic flowmeter after the ***, the correctness of this judgment is fully verified. The electromagnetic flowmeter used in the coal slurry pipeline measures the bulge cracking phenomenon of the inner lining of the pipeline.
1. Analysis of the cause of the failure
In view of the situation in the internal lining of the electromagnetic flowmeter, the workshop organizes personnel to
analyze and communicate with the process workshop and the electromagnetic flowmeter manufacturer. The reason
for the final judgment may be
1.1 The coal slurry pipeline is not equipped with an exhalation valve. Because the height difference between the
coal slurry pump and the gasification furnace coal slurry pipeline is large, the negative pressure is easily generated
in the pipeline during the gasification furnace opening and stopping, which causes bulging and cracking.
1.2 The temperature of the coal slurry pipeline is too high, especially in the summer, the internal temperature of the
coal slurry pipeline can reach about 80 °C, and the material used in the internal lining of the electromagnetic flowmeter
is polyurethane rubber, which is resistant to high fluid temperature of 80 °C, due to Long-term exposure to temperature
limits can lead to aging and cracking of the lining.
1.3 Coal slurry is mixed with fusel oil during use, causing the acidity of the coal slurry. The internal lining material of
the electromagnetic flowmeter is urethane rubber, which has poor acid and alkali resistance. It is prone to bulging and
cracking when used for a long time.
2. Solution to fault handling
According to the communication with the electromagnetic flowmeter manufacturer and the use status of the electromagnetic flowmeter of the on-site coal slurry pipeline and the process operation index, it is decided to carry out the transformation
test of the internal lining of the electromagnetic flowmeter, and select the lining material which is more suitable for the actual working conditions of the site, through research In comparison, ZUI chose Teflon PFA as the internal lining material for the electromagnetic flowmeter. Polyurethane rubber compared with Teflon PFA: main properties of polyurethane rubber
(1) has good wear resistance (ten ten times that of natural rubber), poor acid and alkali resistance
Polyurethane rubber application range
(1) Temperature is less than 40 ° C
(2) Neutral strong wear of slurry coal slurry, mud
The main performance of Teflon PFA is temperature resistance and corrosion resistance is the same as that of PTFE. The bonding property of the lining and the pipe is enhanced by the molding method, the thermal expansion coefficient of the lining is reduced, and the thermal expansion due to high temperature and the lining of the negative pressure are overcome. damage.
Teflon PFA scope (same as PTFE):
(1) Temperature is between 40 ° C and +180 ° C
(2) Strong corrosive medium such as concentrated acid and alkali
(3) Hygienic media
One disadvantage of Teflon PFA is that the wear resistance is not very good, but through the calculation of the coal slurry
flow rate of the coal slurry pipeline (the normal use of coal slurry flow is about 14m, the diameter of coal slurry pipeline is
0lm, the flow velocity of coal slurry is 0495 The flow rate of the coal slurry is about 3600×3.14×0050495m8, and the lining material can be used as an attempt.