SGEC installed 3×1 configureation and includes three gas turbine and HRSG, and 1 steam turbine, the water treatment is using cation and annion plus mix to generatre the deminerlization water to provide the make up for three HRSG durms, due to two shift oeration mode, and drain water from HRSG and STG at start time drain to blowdwon tank can’t return to condenser, so the requested make up water amount is larger than based load opertion mode , cation and annion bed regeneration was using HCL and caustic, in genreal the cation and annion system was operaiton success to provide the demelierization water.
For the boiler water treatment to add triphoshate to HP drum then cascade to IP drum and keep IP drum phoshate 4.00 ppm ,also add ammine to condensate water to nuetralized carbonate acid and increase the condensate water PH 9.8 to prevent the FAC in the condensate water system, but water treatment system had a lot of problem after commisoning.
For the cooling tower add suphric acid to control the PH and also add corrossion inhibtor and yellow meteal corrosion, use bleach as beocide to control the bugs grow up. Cooling tower blow down request 0 free clorine according to city bylaw, so soidum bisulfite add inside to nutrialize free chlorine.
1 Chemical offload to wrong tank
Demin plant has two chemical tanks installed side by side in the demin building, one is acid tank use to regenretaion of the resin and another cation resin and another is caustic tank to used for the regenerator annion resin.
Due to the driver careless, and site two connector not labeled clear, one day the driver connect acid truck to to caustic tank and offlocd chlorie acid to caustic tank, cause the acid reacted with caustic in the tank produced heat and with water and salts, the specific Heat of HCl & NaOH Solution is 4.017 J/g°C , caustic did fulling cleaning and test after this accident, and driver got training, and the offloading labeled clearly and the connection valve install a lock, driver need use right lock to open the valve to prevent this kind of the accident happen again
Figure 1 Demin plant caustic and acid tank
2 Acid tank to repair
After the first year operation and found the acid tank has chemical leaking on the bottom of the tank, and to contact with manufacture to claim warranty, and a temporary tank installed just outside of the Demin water building to keep plant operation
Acid thank successfully rebuild on site which was cut the bottom of tank and rebuild, after another half year the rebuild tank leakage, so it still under the warranty of the most recently repair so OEM was on site to repaired the tank, second time rebuild is sccssfully last over 10 years no problem.
Figure 2 Acid tank leaking from bottom first time
Figure 3 Acid tank leak from bottom after repair
Figure 4 Cut the bottom replace it to new
Figure 5 repaired acid tank second time
3 Rebuid the acid skid
HCL storage room acid pump sikd installed inside of the aicd tank enclosue, which is in the acid atomosipher. The the skid system material is carbon steel which was very fast corrided, so the pump flange leakage very fast and requests to repair every 6 month, the acid pump outlet check valve was corroided and damaged frequencyly and cause could’t to pump acid for the resin generation.
Figure 6 the acid pump corrosion on the acid
Figure 7 acid skid
4 sum pump damaged
Chemical building sump pump damaged then the water cause over flow , the sum pump outlet was broken
American-Marsh Model SREM Sump Pumps are used in a variety of industries
Figure 8 sum pump outlet was broken
Figure 9 the sump pump
5 Resin qualitly analyisis
Resin was sent out to OEMs to analysis the quality and find how much degree degradation which plant was found the regeneration efficiency was low, here is some points from OEMs.
Figure 10 cation resin
the strong acid cations have elevated water retention capacities and someresin capacity loss 8%. The strong base anions also have some resin capacity loss 5%. We noted your concern about broken anion beads however the samples that we looked at showed very little signs of cracking or breakage. If the sample sent to the lab is not representative we may not have been able to see any broken beads that may be present. It is imperative that you determine the source of oxidation due to the extremely short
run lengths, high conductivity and current resin damage. The resin may need to bereplaced if the damage is irreversible. Oxidative degradation has been seen with the ion exchange resin, as indicated in the sample results section. When resins are degraded, the water capacity increases and the ion exchange capacity decreases. This loss of capacity will lead to short run lengths and premature bead breakage and should be avoided by minimizing the source of oxidation. For the lead ion exchange vessel, generally the cation resin, the typical source of oxidation is free chlorine in the feed water. If chlorine is present, it should be treated to lower the levels to 0.1 ppm or less. Common techniques for chlorine removal are carbon beds or the addition of a reducing agent such as sodium bisulfite. If chlorine removal is not feasible, short resin life will occur. Switching to a higher cross-linked resin may minimize the rate of performance decline for systems where chlorine removal is not possible.
Anion resins, while not generally exposed to free chlorine from the feedwater, are more susceptible to oxidation. Trace amounts of oxidizers can cause loss of functional sites. Even dissolved oxygen from a forced-draft degas unit can cause an elevated rate of degradation. High operating temperatures and the presence of catalytic metals can also contribute to an increase in the rate of degradation. To minimize anion resin degradation the resins should not be subjected to oxidizers, and the temperature guidelines should be carefully followed during operation and regeneration. For Type I anion resins, the suggested maximum operating temperature is 140°F. For Type II anion resins the degradation occurs much faster and a maximum temperature of 95°F should be used. Acrylic anion resins are very sensitive to oxidation and should also use 95°F as the maximum temperature. If the source of oxidation is not immediately clear, it should be identified and remedied in order to prevent further degradation of the ion exchange resins.
6 demin water tank over heating
Due to hot water tank heater thermocouple fault and not detect the heater over heated the hot water tank and tripped the tank heater, It was over heated upper side of the tank the painting was bubbled.
Figure 11 the upper side of the hot water tank was overheated
7 Conculsion
SGEC was largest of combined power plant in Canada which experience some problems for the water treatment system, plant staff worked very hard to overcome those kind of the problems after commissioning.