In all kinds of high-temperature industrial scenarios, from the blazing steel mill furnace, to the continuous operation of the cement plant rotary kiln, to the high-temperature operation of the glass factory kiln, refractory materials play an extremely critical role. The correct installation of refractory materials ensures efficient and stable operation, extends service life and reduces energy consumption and maintenance costs. However, once the installation process is wrong, it is like putting a grain of sand in a precision instrument, which can lead to a series of serious problems, such as premature failure, soaring energy consumption, and even lead to costly and prolonged downtime. So what are the common mistakes in refractory installation? Let’s explore some in-depth.
In a steel mill, workers in a service for many years of small steelmaking furnace refractory replacement, in order to catch up with the schedule, the furnace wall is not thoroughly cleaned. The refractory was hastily laid when oil and dust from previous production processes remained on the furnace wall. As a result, the newly installed refractory material began to fall off locally less than a month after it was put into use. The reason is very simple, dirty, greasy furnace wall can not provide good adhesion for the refractory material, in the high temperature, high pressure and steel flushing and other complex conditions, the refractory material and the bond between the furnace wall is unbearable.
Solution: Stop production immediately after the problem is found. First, use professional degreasing agent to wipe the furnace wall repeatedly to ensure that the oil is completely removed. Next, use a wire brush to carefully brush away the surface dust and loose impurities, and finally sandblasting, so that the furnace wall presents a rough, clean state, for the resurfacing of refractory materials to provide an ideal substrate. When resurfacing, choose the refractory material with stronger bonding force and matching binder to ensure that the new refractory material can be firmly attached.
A cement company in a new rotary kiln production line, due to the construction personnel of the importance of the substrate surface treatment is not enough to recognize, in the kiln body of the internal surface of the case of smooth, directly for the laying of refractory bricks. After running for a period of time, the kiln body appeared localized overheating, and upon inspection, it was found that some areas of the refractory bricks appeared to be loose and displaced. This is because the smooth surface of the substrate can not be a close fit with the refractory bricks, in the rotary kiln continues to rotate, material friction and temperature changes under the combined effect of the refractory bricks are difficult to stabilize the fixed, gaps and voids resulting from this, the hot gases take advantage of the situation, resulting in overheating problems.
Solution: After stopping the kiln, use mechanical milling or drilling to process evenly distributed grooves or holes on the surface of the kiln body to increase the surface roughness. At the same time, before laying new refractory bricks, apply a layer of high-strength, high-temperature-resistant special bonding agent to enhance the bond between the refractory bricks and the kiln body. For refractory bricks that have been loosened and displaced, carefully remove them and reinstall them according to the new treatment process.
There is a small glass factory, in order to reduce costs, in the key parts of the glass furnace selected a lower price, grade does not meet the requirements of the refractory material. Originally, the part needs to be able to withstand high temperatures of more than 1600 ℃ of high-grade refractory materials, and they choose the actual temperature of the material is only about 1300 ℃. After the furnace was put into use, just three months, the part of the refractory material appeared serious erosion, softening phenomenon, had to be replaced urgently, not only cost a lot of money, but also led to the production interruption, resulting in considerable economic losses.
Solution: Immediately stop production to replace the advanced refractory materials that meet the requirements. When selecting new materials, consult the refractory supplier in detail and provide specific working parameters of the furnace, including maximum temperature, temperature fluctuation range, chemical erosion medium, etc., to ensure that the selected materials fully meet the usage requirements. At the same time, the newly replaced refractory materials are regularly monitored, and a usage file is established to record the changes in their performance at different stages to provide data support for subsequent maintenance.
In a large steel plant’s blast furnace hot blast furnace renovation project, the construction team did not fully consider the compatibility between the old and new refractory materials when replacing some of the refractory materials. The newly selected refractory materials were chemically different from the original alkaline refractory materials, and after being installed next to each other, a chemical reaction occurred in a high-temperature, high-alkali environment. After a period of time, the performance of the refractory material at the connection decreased sharply, cracks and spalling occurred, affecting the normal operation of the hot air furnace.
Solution: First, conduct a comprehensive inspection of the hot air furnace to determine the scope and extent of the chemical reaction. For the seriously affected areas, remove the old and new incompatible refractory materials and re-select products with good compatibility with the original refractory materials for replacement. Prior to installation, materials are screened in strict accordance with the compatibility charts provided by the manufacturer, and compatibility tests are conducted on a small scale. In addition, at the intersection of new and old refractories, set up a transition layer to relieve the chemical and physical stress that may arise.
During the construction of a shuttle kiln in a ceramic factory, the bricklayers were inexperienced and failed to ensure uniformity of the ash joints when laying bricks. Some of the ash joints are too thick, resulting in the process of heating the kiln, these parts of the refractory expansion is not consistent, resulting in internal stress. After half a year of operation, multiple cracks appeared inside the kiln, seriously affecting the insulation performance and service life of the kiln.
Solution: For the parts where cracks have appeared, first assess the severity of the cracks. If the cracks are small, high temperature resistant sealant can be used to fill and repair; if the cracks are large, remove the problematic refractory bricks and re-lay them. When re-laying, arrange experienced workers to operate, use precise trowels and shims, and strictly follow the manufacturer’s specified brick joint size (generally controlled at 2 – 3 mm). At the same time, strengthen the quality check during the construction process, and measure the thickness of the mortar joints with professional tools every time a certain number of bricks are laid to ensure uniformity.
A foundry in the melting furnace lining repair, the use of unshaped refractory materials for pouring construction. Construction personnel in order to speed up the progress, in the pouring process did not use vibration equipment on the non-shaped refractory material for adequate compaction. As a result, after the repair of the melting furnace in the use of the process, the furnace lining of the internal cavity gradually exposed, high temperature metal liquid penetration into the cavity, accelerated the erosion of the furnace lining, less than two months will need to repair again.
Solution: After stopping the furnace, conduct a comprehensive inspection of the furnace lining to determine the distribution range of voids. For the area where the voids are concentrated, remove the loose, uncompacted indefinite refractory material and re-pour. When re-pouring, use the appropriate power of vibration equipment, such as insertion vibration rod, according to a certain vibration spacing and time for vibration, to ensure that the material is fully compacted. At the same time, control the pouring speed, to avoid too fast resulting in uneven material accumulation, affecting the compaction effect.
When the boiler of a thermal power plant was upgraded with refractory materials, the construction party selected anchor nails of substandard quality in order to save costs, and did not operate in strict accordance with the specifications during the installation process, and the anchor nails were embedded in insufficient depth. After the boiler is put into operation, in the high temperature, high pressure and flue gas scrubbing and other harsh conditions, the refractory material due to poor anchoring, there is a large area of the phenomenon of falling off, not only endangering the safe operation of the boiler, but also caused a long time of shutdown maintenance.
Solution: First of all, carry out a comprehensive downtime inspection of the boiler, remove all peeling and loose refractory materials. Replace the anchor nails with qualified quality and matching specifications, and ensure that the embedding depth of the anchor nails reaches the design standard (generally 2/3 – 3/4 of the length of the anchor nails) in accordance with the installation specifications. When reinstalling the refractory material, use special tools to closely connect the refractory material with the anchor nails to ensure that the refractory material is firmly fixed. Upon completion of the installation, conduct an anchorage force test to ensure that each anchorage point meets the requirements for use.
In the construction of an electrolysis tank in an aluminum refinery, due to the designers’ insufficient prediction of the temperature changes during the operation of the tank, no expansion joints were set during the installation of the refractory materials in the tank body. As the electrolysis process continued, the temperature inside the tank increased, and the refractory material was subjected to thermal expansion but had no place to expand, eventually leading to extensive cracking and bulging. This not only seriously affected the normal operation of the electrolysis tank, but also significantly shortened the service life of the refractory material.
Solution: Stop production and remodel the electrolyzer, and cut expansion joints in the refractory material of the tank body according to a certain spacing. The width and spacing of the expansion joints need to be determined by precise calculations based on the thermal expansion coefficient of the refractory material, the maximum temperature of the electrolytic cell operation and the size of the cell body (generally, the width of the expansion joints is 5 – 10 mm, and the spacing is 1 – 2 meters). Cutting is completed, in the expansion joints filled with high-temperature resistant, flexible ceramic fibers and other filler materials to adapt to the expansion and contraction of refractory materials.
When a chemical plant’s reactor was undergoing refractory maintenance, the workers made a mistake in filling the expansion joints and used a filling material with high hardness and poor flexibility. When the reactor is running, the refractory material expands, due to the filling material can not adapt to this expansion and contraction changes, the expansion joint loses the buffer role, the refractory material is subjected to additional extrusion, resulting in cracks in many parts of the furnace body.
Solution: After stopping the furnace, clean out the original unsuitable filler material, and choose filler material such as ceramic fiber, alumino-silicate fiber and other flexible, high temperature resistant filler material to refill the expansion joints. Filling, to ensure that the material is filled closely and evenly, not only can effectively buffer the expansion force of the refractory material, but also will not affect the normal expansion and contraction of the material. At the same time, assess the cracks that have appeared on the furnace body, and according to the size of the cracks, use grouting to repair or locally replace the refractory material and other ways to deal with it.
From the many practical cases mentioned above, it can be clearly seen that every link in the refractory installation should not be underestimated. From the early stage of the installation of the surface of the meticulous treatment, to the precise and accurate selection of suitable materials; from the strict implementation of the installation technology in accordance with the norms, and then consider the expansion and contraction characteristics of the material and properly respond to any deviation in any of the steps, may be for the subsequent production and operation of the buried hidden danger.
For industrial enterprises, in the installation of refractory materials, should be organized for professional training of construction personnel, so that they deeply understand the principle behind each installation point, master the correct operation method. At the same time, the establishment of a strict quality control system, starting from the source of material procurement, each link in the installation of supervision and inspection to ensure that the installation process is scientific and standardized. Only in this way can we give full play to the performance advantages of refractory materials, to ensure that high-temperature industrial equipment for a long time, stable and efficient operation, reduce equipment maintenance costs, and enhance the economic benefits and market competitiveness of enterprises.
