The "Three Mountains" of Flue in Electrolysis Plant: High Temperature, Corrosion and Large Displacement
It is not too much to say that the flue system of the electrolysis plant is the "lung" of the whole production line. But if you have really touched it, you will know how much this "lung" has suffered-the temperature of the flue gas has soared above 500℃ all the year round, and there are strong corrosive gases such as HF and SO₂ sandwiched in it. In addition, the pipeline expansion and contraction caused by the alternation of hot and cold shutdown is always displaced by tens of millimeters. With these three things together, the metal expansion joint simply can't handle it.
Isn't metal stronger? Yes, metal is indeed tough at room temperature. However, in the electrolytic flue, the high temperature will make the metal creep, and the corrosive gas will gnaw pitting corrosion on the surface of the bellows, not to mention the frequent displacement cycle that directly cracks the weld. I have seen some factories use metal rectangular expansion joints. In less than a year, they leaked like a sieve, the flue was blocked, the exhaust air volume dropped, the temperature of the electrolyzer was out of control, and finally they were forced to stop production and replace parts. Who could bear the price?
Non-Metal Compensator vs Metal Expansion Joint: Who Carries More?
Take our rectangular non-metallic expansion joints and fabric fiber expansion joints as examples. The material is a dimensionality reduction blow. The main body of non-metallic compensator is corrosion-resistant materials such as silicone rubber, fluororubber and polytetrafluoroethylene. With multi-layer glass fiber cloth or ceramic fiber, it can withstand high temperatures above 600℃ without any problem. The key is that it has good elasticity-even if the flue has an axial or lateral displacement of 30mm or 50mm, the loop belt will be absorbed as soon as it expands and contracts, unlike metal bellows, which is hard to carry and cracks if it can't be carried.
Let's talk about corrosion. The fluoride ions in the electrolytic flue gas are a nightmare for 304 and 316 stainless steel. But what about the vitron and PTFE layers? Basic insulation. I have encountered a case in an anode roasting workshop. It used to use metal bellows, and it was perforated in three months; Replaced with fabric fiber expansion joints (non-metallic expansion joints), which are still intact after two years. Old drivers all say that the non-metallic compensator in the flue of the electrolysis plant is the "true master".
Key to model selection: Material matching, structural design and synergy of baffle door
Choosing a non-metallic compensator is not done just by looking at the thickness. You have to calculate the flue gas composition and maximum temperature-if the acid concentration is high, the lining has to be a PTFE compensator or rubber PTFE compensator; If the temperature exceeds 450℃ and contains particulate dust, a ceramic fiber layer and a wear-resistant guide tube should be added.
Structurally, rectangular non-metallic expansion joints are more suitable for rectangular flues, while fabric fiber expansion joints are flexibly suitable for round pipes. But there is a point that is easy to overlook here: the compensator should work in cooperation with the smoke baffle door and the electric plug-in insulation door. For example, when shutting down for maintenance, it is necessary to use a double-sealed single-axis circular baffle door to cut off the flue gas. If the flange surface of the compensator is not tightly sealed, or the displacement compensation is not in place when the baffle door is linked, the flue gas will flow back and corrode the valve and actuator. Our supporting desulfurization flue gas baffle door is specially designed for this wet and acidic pressure reduction scenario, and in cooperation with the compensator, it can ensure zero leakage.
Several pits in installation and maintenance
Tie rod nut adjustment. Many installation teams welded directly after unpacking, and forgot to loosen the limit rod first-the non-metallic compensator will be tightened for transportation safety when it leaves the factory, and the nut must be withdrawn to the designed displacement position after installation. Otherwise, if the flue expands and the circle rips apart, it will really lose his wife and his soldiers.
The role of the deflector is neglected. The guide tube is a protective sleeve arranged on the inner wall of the compensator, which can prevent the high-speed dusty smoke from directly washing the ring belt. I have seen the scene in order to save costs, the guide tube was disassembled, and as a result, the circle belt was worn out in three months. According to the national standard JB/T 12235-2015, the guide tube must be installed as designed.
Seal check go form. The flange connections of non-metallic compensators must be compacted with flexible sealing tapes without gaps. The inspection method is very simple: after the flue is running, use the back of your hand to close to the seam and feel whether there is any hot air leakage. If available, tighten the bolts or replace the gasket immediately. This step is lazy, and the subsequent corrosion spreads directly to the pipe wall.
From the perspective of life and cost: Why do old drivers of electrolysis plants look for non-metallic compensators?
At the end of the day, using a non-metallic compensator is not trendy, it is posting. Metal expansion joints have short life and high replacement frequency. The key is that they lose hundreds of thousands a day after shutting down production. What about non-metallic compensators? It is common to use it for 3-5 years under normal maintenance, and the price is only about one-third of the price of metal products of the same specification. You see, counting the electrolysis plant flue non-metallic compensator in the whole life cycle of the whole flue gas system saves money and worry.
Two days ago, an old purchaser from an aluminum factory talked to me. Their factory used to use metal all the time, but later it was afraid of corrosion. The technical transformation of the whole factory was all replaced with rectangular non-metallic expansion joints. Before and after comparison, the failure rate dropped by 80%, and the maintenance hours were 90% less. He said something that I think makes sense: "In electrolytic flues, non-metals are the hard currency." So, regardless of new projects or technical modifications, look for non-metallic compensators, yes.