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Optimization and improvement of rotary kiln hood structure

  1 general structural form and construction method of rotary kiln head cover

  NSP kiln kiln head cover common structure form for use i-steel welding steel structure frame, the steel structure framework laying 6 ~ 10 mm of steel plate, under the uniform anchorage parts, sheet metal castable construction in anchoring a cramp, the root plate surface laid 50 ~ 100 mm calcium silicate board, on the anchoring piece bituminous paint or wrap adhesive tape, reserved expansion joint, sheet metal pouring hole, at the bottom of the template, the template below need erection of scaffolding for support.

  2. Disadvantages of traditional structural forms

  2.1 the insulating calcium silicate plate is easy to be damaged

  The traditional form of kiln head cover requires a layer of calcium silicate plate to be laid on the root of the anchoring part and the surface of the steel plate, which plays a major role in heat insulation and can protect the bottom steel plate, steel structure frame and the welding points of the anchoring part and the steel plate from high temperature erosion.

  Calcium silicate board fixed is generally in the anchoring of the roots with fine wire winding bundle and the link is the most weak link in the process of construction of the kiln head cover, the castable construction calcium silicate board by the vibration of the vibrator and castable liquidity shocks tend to be out of the original fixed position, cause in every area of the entire castable internal filling calcium silicate board, exposed on the surface of the castable, calcium silicate board by high temperature gas scour and clinker particles after it is easy to damage, damage to the calcium silicate board connected to each other within the castable channel formation, high temperature gas through channel damage anchorage pieces, backplane, framework, until the kiln hood is damaged.

  2.2 it is easy to damage the insulation layer by opening pouring holes

  Castable construction need to reserve pouring hole in the bottom of the steel plate surface, shoulds not be too reserved and pouring hole is too big, because too much too much pouring hole will reduce the number of certain anchorages, and affect the structure of the framework of the overall strength, and the pouring hole is not easy to leave less than hours castable construction and vibration rods is not easy to reach the designated position, in order to fill in place can only take the castable more water, flowing way let castable to each location, the castable construction quality is the most important link of water control, too much water can cause castable internal pore rate is too high, the serious influence to the castable use cycle,

  At the same time, excessive moisture will also cause maintenance difficulties and long maintenance cycle, which will be particularly prominent in heavy production tasks and short maintenance cycle, seriously affecting and restricting the normal development of various work.

  2.3 other disadvantages

  Traditional structure form of the kiln hood because of the need to lay at the bottom of the steel plates, calcium silicate board, anchor laid partial problems such as long, so the framework of the overall weight of the heavy, cost is high, lead to the thickness of the pouring material is not easy to control, the castable use cycle short, thin castable too thick, support the reinforcement effect of i-steel easy to bending deformation, the stress will directly effect the castable, resulting in stress cracking of castables, high temperature flue gas carrying fly within the kiln hood ShaLiao erosion from castable crack anchoring pieces to lay a foundation and steel plates, the anchor pieces, castable and damage of steel structure quickly.

  3.Optimization and improvement of the structure of rotary kiln hood

  3.1 increase the structural strength

  Because the wing is too narrow a structural characteristics, lead to the strength of the beams is difficult to play in the application of the steel, in order to increase the strength of steel structure, the steel structure framework by beams to h-beam, compared with h-beam although slightly heavier than beams, but large, h-beam flange welding surface, welding splice than beams, simple operation, unit weight of better mechanical properties, and the construction more convenient, can save a lot of material and construction time, the bearing quality is better.

  3.2 reduce frame weight

  In order to reduce the weight of the frame and facilitate the pouring construction, the steel plate laid on top of the steel structure frame was cancelled. The steel plate before was 6 mm thick, with an area of about 50 m2 and a weight of nearly 3 t. After removing the steel plate, the weight was significantly reduced.

  3.3 change the welding point position of anchorage parts

  Use Φ 50 mm seamless pipe laying in the frame of the H welded together, steel tube and steel tube parallel arrangement of steel tube and steel tube center is the distance between the anchor spacing, anchorage welding on the seamless steel pipe, solder joints exposed, not affected by high temperature corrosion.

  3.4 cancel calcium silicate plate

  For calcium silicate board difficult to fixed, castable construction, easy to produce holes and castable false vibration problems, take measures is to cancel the calcium silicate board, the top teams at the bottom of the mold, pouring construction method, poured into a mould of the castable should immediately use vibrator vibrated, vibration may not be in the same position for a long time, when the surface FanJiang castable, bubble is less the vibrator can be slow, avoid castable or segregation phenomenon appears holes.

  The overall structure of kiln hood is shown in figure 1.
 schematic diagram of overall structure of kiln hood

  FIG. 1 schematic diagram of overall structure of kiln hood

  From the kiln head cover use condition and economy into consideration, high strength refractory castable appropriate chooses mullite castable, expansion joints according to design requirements to keep in the intermediate position of the anchoring pieces of interval, insert 2 mm every 1.5 m thick plywood, considering the convenience of construction, can also be installed templates folder in the template docking aperture place when installed three-ply board, can have the effect of expansion joint and convenient construction.

  4. Matters needing attention in optimizing and improving the construction of kiln hood

  The improved kiln head cover cancels the calcium silicate plate and is all castable, so the bearing calculation should be carried out according to the structure of the kiln head cover to prevent the steel structure from deformation due to the heavy castable and the stress cracking on the surface of the castable.

  The steel pipe of welded anchorage should not be too long, and should be controlled within 1 m as far as possible, so as to avoid bending and deformation of the steel pipe due to excessive force.

  In order to prevent the steel pipe from deformation, after the construction of pouring material, a steel pipe can be laid horizontally on the longitudinally uniformly distributed steel pipe. The steel pipe is welded to the contact point of the steel pipe. The two ends of the horizontally distributed steel pipe are in close contact with h-shaped steel and are welded to strengthen, prevent stretching and prevent deformation, as shown in figure 2.
 steel pipe layout in the cell

  FIG. 2 steel pipe layout in the cell

  In order to increase the welding surface between the anchorage part and the steel pipe, the root of the anchorage part and the steel pipe shall be welded at an Angle, that is, in the form of "zhe".

  The arrangement of anchorage parts is shown in FIG. 3.
schematic layout of anchorage parts

  FIG. 3 schematic layout of anchorage parts

  As the castable is directly exposed to the surface and in a good state of ventilation, the improved structure can well avoid the oxidation deformation of the steel and the solder joints of the steel and anchorage parts after high temperature corrosion. However, it must pay attention to rain-proof and snow-proof and dust-covered accumulation, so it must add rain-proof and dustproof shed, as shown in figure 4.
rainproof and dustproof shed

  FIG. 4 rainproof and dustproof shed

  Because the top of the kiln head cover is sloping and the pouring material has the property of self-leveling, the upper surface of the pouring material is not easy to be consistent with the Angle of the steel structure frame during the construction.

  In anchorage in order to make the point of view is consistent, need root laid sheet steel, the thickness of the thin plate with 2 ~ 3 mm advisable, thin steel plate and steel tube welding can, but must be dismantled when castable loss of liquidity, as shown in figure 5, such not only is advantageous to the castable castable in evaporation also facilitate internal holes, and found the problem and deal with the problem in time.
steel plate layout

  FIG. 5 steel plate layout

  Expose the solder joints of the anchorage and steel tubes to the natural environment as much as possible, or reduce the covering thickness of the pouring material as much as possible on the solder joints to prevent the solder joints from being corroded by high temperature.

  In order to strengthen the structural strength of the steel structure frame, the h-shaped steel in the direction of length should use the whole steel, in the direction of width use short steel, but in the welding of the contact surface must be full welding.

  The bottom formwork shall not be removed until the surface of the pouring material is hardened and the strength reaches more than 70%. The pouring material shall be inspected in time after the molds are removed. In case of quality problems such as honeycomb, peeling and holes, the same type of pouring material shall be used for treatment and repair in time.

  Use effect and economic benefit

  The service life of the traditional kiln hood is generally 1.5~2 years. After the optimization, the service life of the kiln hood can be stabilized to more than 3 years.

  According to the traditional form of kiln head cover use period of 1.75 years, the use amount of kiln hood castable for 30 t, tons of castable for 3, 000 yuan, the price of the kiln head cover production costs 100000 yuan, tons of castable construction costs $1, 200, the kiln head cover use steel quantity to 12 t, 4 tons of steel price 000 yuan, the anchoring piece cost roughly 20, 000 yuan, the traditional form of the kiln head cover of a total value of 000 yuan, 274 amortizing the cost for 156, 571 yuan a year.

  According to the total cost of the kiln hood before and after the transformation is basically the same, but the use cycle is different to calculate, the average cost of the optimized transformation of the kiln hood is 91,333 yuan per year.

  In this way, compared with before the transformation, the annual cost of the transformed kiln hood can be saved by 65,238 yuan, and the cost can be saved by 195,714 yuan in one service cycle (3 years), which does not include the template, calcium silicate plate, scaffolding, crane, impact on the production system and the investment in safety, with considerable economic benefits.

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