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Reasons and countermeasures for damage of castable in pulver

Date:2019-04-02 15:06     writer:admin     Views:

  In the calcining process of cement clinker, whether the pulverized coal burner can operate normally and stably will decide the output and quality of cement clinker.

  As the pouring material of the protective cover of the pulverized coal burner is particularly important.

  Qingzhou zhonglian cement co., LTD. Phase ii 6000t /d clinker cement production line adopts Duoflex coal powder burner produced by fl.smith company. It has been put into production for about 4 months.

  In this paper, the causes of the damage of castable in pulverized coal burners are discussed from two aspects of cause analysis and countermeasures.

  1 cause analysis

  Normally, the burners work for 3 to 4 months and the castables are damaged to varying degrees.

  Under the action of thermal stress and mechanical stress, microcracks in the castable continuously expand and extend, resulting in spalling of the castable.

  Damage of qingzhou zoomlion phase ii burner after about 4 months of use is typical, as shown in figure 1.

  The following is an analysis of the thermal stress and mechanical stress.

  (1) influence of thermal stress.

  Rotary kiln burner the location for the former kiln mouth, working environment temperature is 600 ℃ ~ 300 ℃, and the fluctuation range high temperature.

  As the pouring material of the pulverized coal burner is a poor conductor of heat, the thermal expansion coefficient is different due to the temperature difference, and cracks will occur in the parts that are not heated evenly after a period of use.

  Table 1 shows the values at different temperatures of corundum/mullite castables used in several pulverized coal burners at different temperatures.

  In addition, in the process of pouring material construction, transverse construction is adopted. Due to the effect of gravity, the upper half of the pouring material of the cylinder body is inevitably different from the lower half of the pouring material. The different density leads to uneven heat conduction, and it is easy to generate cracks.



  (2) influence of mechanical stress.

  The high temperature secondary air is blown into the rotary kiln from the grate cooler under the pulverized coal burner.

  Resulting in crack will grow big, reveal internal anchor pieces, even under the high temperature anchoring pieces of welds will be melt, due to the gravity and then anchor a drop, along with castable burner metal shell, no protection castable, burner cracks easily at high temperature as shown in figure 3, once the cracks caused by air leakage, the burner can't continue to use.



  2. Countermeasures

  In view of the problem of easy damage and falling off of the castable of pulverized coal burner in most cement factories, relevant technical personnel and construction personnel were consulted on the site of phase ii of qingzhou zhonglian group co., LTD.

  (1) pouring construction method.

  Due to the limitations of site construction conditions, transverse construction has the advantages of convenience, speed and cost saving, so it is adopted by most construction units. For the pouring materials in horizontal construction, due to gravity, the density of the upper and lower parts will be uneven to different degrees, and it will be easier to be deformed and fall off in the rotary kiln.

  Therefore, it is recommended to use vertical construction, and use lifting equipment to lift the whole burner and the ground vertically for pouring. This pouring method can make the density of pouring material more even and the head pouring closer.

  (2) the shape of the pouring material at the burner head is chamfered.

  Pulverized coal burners are produced in the air stream of rotary kiln

  The outside of the primary wind is easy to generate swirl, and the airflow will drive some pulverized coal to bond in the head of the pulverized coal burner, resulting in coking phenomenon. As the coking gradually increases and spreads, it interferes with the shape of the flame, resulting in uneven temperature on both sides of the burner.

  Therefore, the pulverized coal burner cannot be simply poured into a cylindrical shape, as shown in figure 4.

  And should be pouring into chamfering (30 ° ~ 40 °) proposed, chamfering pouring method can simply and effectively reduce the coking phenomenon as shown in figure 5.





  (3) arrangement of anchorage parts.

  All anchorage parts shall be welded in strict accordance with the vertical interactive welding method, with a distance of 150mm. Generally, the manufacturer will add plastic caps on the anchorage parts, and replace the plastic caps with a layer of asphalt, without direct contact with the castable.

  Wax all anchorage parts and all surfaces before pouring.

  In order to prevent the burner thermal expansion and lead to the pouring material damage.

  (4) casting material selection and ingredients.

  Castable material is selected according to the principle of high temperature wear resistance, anti-stripping, relatively small weight (cantilever pulverized coal burner has strict control over weight).

  It is recommended to add SiC or other high-temperature wear-resistant materials because the lower end of the pouring material of the pulverized coal burner is easily worn.

  Strictly control the amount of water used for construction, the recommended amount of water is below 8%, depending on the specific use of refractory material model requirements, in the premise of ensuring the construction performance, the amount of water should be strictly controlled, less should not be more.

  (5) retention of expansion joints.

  In the direction of every 1m, one expansion seam shall be left in the ring of the pouring material of the pulverized coal burner, and 2~4 expansion joints shall be left in the axial direction (staggered joints). The width of expansion joints shall be 10mm, and the expansion joints shall be filled with ceramic fiber blanket.

  In a word, improving the construction technology of pulverized coal combustion castable and extending its service life are of profound significance for improving the continuous operation time of rotary kiln and even improving the quality and output of cement products.

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