How "abnormal" is the dry coke quenching working condition-temperature, dust and thermal displacement, which ordinary compensators can't bear
Dry quenching is really not something that ordinary compensators can connect. Think about it, the temperature of circulating gas soars above 950℃ at every turn, and there are coke powder particles sandwiched between them, and the wind speed is as fast as a grinding machine. Calculated by the thermal expansion of the pipeline, the axial displacement is tens of millimeters, and the lateral offset is not small. Metal corrugated expansion joint Under this working condition, high-temperature creep and dust scour will crack in a few months. Some factories have tried to use ourHigh temperature axial expansion jointHowever, once the metal part exceeds the design temperature, the fatigue life directly dives.
What about that? Only non-metallic compensators can be used. However, note that not all non-metals will work-ordinary rubber compensators are directly carbonized here, and they have to be high-temperature types specially developed for dry coke quenching.
Why can the non-metallic compensator go on? Combination of Fabric Fiber + Temperature Resistant Layer
The core secret is in structure. OurNon-metallic expansion joint (fabric fiber expansion joint)The outermost layer is a glass fiber cloth coated with silicone rubber or fluororubber, which can withstand temperatures up to 600°C without any problem; The ceramic fiber felt is sandwiched in the middle, which is heat insulating and flexible; For the inner layer, use stainless steel wire mesh reinforced polytetrafluoroethylene membrane, or simply add a metal guide tube to block erosion.
And guess what? This combination carries better than metal pieces. Because the non-metallic elastic modulus is low, the stress when absorbing heat displacement is small, and the stress concentration will not occur like that of metal bellows. Moreover, the fabric fiber itself has micropores, can "breathe", and has better tolerance to alternating thermal shock. However, one thing must be said-when the temperature exceeds 1000℃, you still have to use a cooling jacket or a series metal diversion structure.
Don't step on pits when selecting the model: temperature grade, structural form and installation space must not be lacking
Two days ago, I met a customer and asked, "How many degrees can your non-metallic compensator withstand?" I said you had to tell me the actual temperature of the pipeline medium first, whether there was an instantaneous peak, and the dust concentration. Dry coke quenching pipeline has a characteristic-large temperature fluctuation and frequent alternation of hot and cold. So the first parameter of the selection isDesign temperature class, not the average value, but the highest possible value plus a 20°C margin.
Second, structural form. The diameter of dry quenching pipes is large (many exceed 2 meters), so rectangular non-metallic expansion joints save more space than round ones at this time. Remember we haveRectangular non-metallic expansion joint, specially adapted to square flue. However, if it is a circular pipe, be careful to matchguide tube— — The specific function of the expansion joint guide tube is to guide the high-speed airflow smoothly and prevent the direct erosion of the flexible ring belt. Generally, the length of the guide tube should cover more than 50mm on both sides of the ring belt.
Third, installation space. The inlet and outlet space of some dry quenching waste heat boilers is extremely narrow, and even the wrench can't reach in. That's when you have to use itRotary compensatorOr other compact construction, but the rotational compensator is suitable for angular displacement, not axial displacement. Therefore, we have to communicate with the design institute in advance and leave enough maintenance gap.
Installation and O&M: Practical experience with deflectors, pull rods and daily inspections
When installing a non-metallic compensator, the most common problem is the tie rod. Many people ask "How to adjust the expansion joint tie rod nut?" Remember: the tie rod at the time of leaving the factory is for limiting, not for stressing. After installation in place, the tie rod nut must be loosened to the scale position corresponding to the design displacement, otherwise the tie rod will directly pull the compensator out once the pipeline expands. On the contrary, if you forget to loosen it, the end flange top will deform when it expands thermally.
Don't reverse the direction of the deflector. The direction of the arrow points to the direction of the media flow-the direction of the arrow of the expansion joint refers to the direction of the media flow. When installed backwards, the guide tube becomes a dust collector, and the coke powder is piled up in it, which will be blocked in a few months.
What about daily inspections? Look once a month for bulging and cracking on the surface of the circle belt. The service life of non-metallic compensator is 3-5 years under normal conditions, but it is recommended to replace the sealing layer during annual maintenance under dry coke quenching conditions. Don't wait until there is an air leak before replacing it-the system pressure differential has changed at that time, which may affect dry quenching efficiency.
Compared with metal expansion joints, what are the advantages and disadvantages of non-metal? When should I use it?
Metal expansion joints (e.g. corrugated expansion joints)Suitable for high pressure, high temperature (but not exceeding material creep temperature), need to bear internal pressure occasions;Non-metallic expansion jointIt is good at low pressure, large displacement, high-frequency vibration and dust. The pressure of dry quenching pipeline is generally only a few kPa to tens of kPa, and the temperature is high but the pressure is low, which is just the strength of non-metals.
The biggest shortcoming of non-metal is that it has weak pressure bearing capacity and cannot be used in medium and high pressure pipelines. In addition, rubber and fabric aging is inevitable, unlike metal parts that can resist corrosion by wall thickness. But on the other hand, the non-metallic compensator is light in weight, easy to install and has good shock absorption effect-a 2m diameter metal rectangular expansion joint has to be served by a crane, and two non-metallic people can lift it.
Then when should I use it? Listen to me: For dry quenching primary dust removal, secondary dust removal pipeline, waste heat boiler inlet and outlet, and circulating gas pipeline (temperature below 1000℃, pressure below 0.1MPa), non-metallic compensator is preferred. When you encounter high-temperature and high-pressure steam pipes, such as the main steam pipe of the waste heat boiler, it is still honestly made of metal, such as oursUniversal corrugated expansion jointOrStraight pipe pressure balanced expansion joint, with a good insulation layer.
Whether it's metal or non-metal, don't forget to look at the national standard- -National standard for non-metallic expansion jointsIt is JB/T 12235-2015, and the manufacturer is required to provide the type test report when selecting the type. Dry quenching pipeline is related to the whole factory production, so don't try to save that little money cheaply.