JPH0240954B2 - KAITENSHOSEIRONOSASUPENSHONPUREHIITAANIOKERUGENRYOFUNMATSUFUCHAKUBOSHIHOHO - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention prevents passing raw materials from adhering to the inner wall of a suspension preheater attached to a rotary furnace for firing clinker such as cement or refractory raw materials, and then becoming stuck and forming a coating state. It is about the method. [Prior art] As rotary kilns become larger, many of them are equipped with a suspension preheater to improve thermal efficiency and take advantage of installation space. The kiln is sequentially guided from above into several stages of cyclones, and kiln exhaust gas at approximately 1000°C is introduced from below to preheat it. FIG. 1 is a perspective view schematically showing the entire apparatus of a rotary kiln and a suspension preheater for firing cement clinker. In the figure, 1 is a suspension preheater with a height of approximately 70 m, and mixed powder raw materials mainly consisting of limestone and clay are inputted from the raw material charging port 2 at the top, and the cyclones 3a, 3b,
3c, 3d and ducts 4a, 4b, 4c, 4d connecting each cyclone, the raw material is sufficiently preheated and falls into the input chamber 5, from which the raw material is supplied to the rotary kiln 6. It's getting old. As is well known, the rotary kiln 6 sequentially moves the raw material in the direction of the kiln burner 7 by rotation of the inclined kiln, and is finally fired at around 1500°C in the firing zone near the burner to become clinker. At this time, the combustion gas is sucked toward the suspension preheater and passes through the inlet chamber 5 at the bottom of the suspension preheater. At this time, the temperature of the exhaust gas is 1000°C to 1200°C, and is the main preheating heat source for the raw material in the suspension preheater. In Fig. 1, 8 is a cooler for cooling the high-temperature clinker, 9 is a cooler bleed pipe,
The high temperature gas in the cooler 8 is also drawn into the suspension preheater through this pipe. [Problems to be solved by the invention] The suspension preheater has the above-mentioned structure, and in order to increase the preheating efficiency, the input raw materials fall sequentially while rotating inside each cyclone. There is also a lot of movement of raw materials within the input chamber 5. Furthermore, as the mixture of powdered limestone and clay undergoes a calcination reaction when heated, the raw material powder starts to adhere to the inner wall of the input chamber after 1 to 2 days of operation of the kiln, and eventually grows to form a front coating. Then, by further heating to a high temperature, a layer of hard, rock-like solid matter (hereinafter referred to as "coating") is formed on the entire inner wall surface. If the operation continues for a long period of time, the interior of the suspension preheater will become narrow, and eventually the ducts and input chambers will become clogged with raw materials, which will seriously impede the supply of raw materials to the kiln. In addition, the pressure loss will increase, which will affect the operation of the exhaust gas suction fan (IDFAN). The coating state of such raw material powder is
For example, in the input chamber, approximately
It reaches a thickness of 250mm to 300mm in 48 hours. Therefore, in a cement rotary kiln, 3
Currently, this coating removal work is carried out 5 to 6 times a day, sometimes 5 to 6 times a day. However, rotary kilns operate continuously for 24 hours.
In addition, since the inside of the suspension preheater is also high temperature, it is impossible to enter inside, so conventionally, we have installed working windows of about 20 cm square in the necessary places, and from these windows, a high pressure (250 to 300 kg/cm ² pressure) water flow is directed to the inner wall surface. inject into;
The coating was removed by blowing off the coating that had expanded in volume due to the hydration reaction. The amount of water required for this is approximately 300,1
The amount of water reaches 1 to 1.5 tons per day, and this water needs to be evaporated inside the preheater, which not only consumes a huge amount of heat calories, but also draws in outside air during the removal process, which significantly increases the preheating efficiency of the preheater. Due to this, the amount of cement clinker baked out has to be reduced to 90-97% of the standard amount, and the large amount of water vapor generated also promotes the sticking of raw material powder in other parts, which is a problem. The dot was hot. The present invention was made to solve this problem, and an object of the present invention is to provide a method that makes it difficult for input raw materials to adhere to the inner walls of various parts of the suspension preheater. [Means for Solving the Problems] The method for preventing adhesion of a suspension preheater according to the present invention is applied to the inner wall of each part through which input raw materials pass through in a suspension preheater, particularly in areas where conventional clinker is significantly adhered (the state of adhesion is (depending on the rotary kiln), an excipient consisting of a layered lattice structure material, a heat-resistant binder, a spreading material, and a dispersion medium is applied in layers. However, the layered lattice structure materials include graphite, molybdenum disulfide, tungsten disulfide, boron nitride,
One or more types of mica is used, one or two types of alumina and silica are used as the heat-resistant binder, starch, resin, sodium silicate, and aluminum phosphate are used as the spreading substance, and it also serves as a dispersion medium for the spreading substance. An excipient containing water, mineral oil, or synthetic oil is applied. [Function] The layered lattice structure substance contained in the excipient has a large lubricity effect due to its layered crystal structure, and is best as a substance that also has heat resistance. The reason why the heat-resistant binder is included is that after the excipient is applied, a portion of the excipient becomes vitrified by the heat received from the high-temperature gas, thereby firmly adhering and solidifying the coating layer. The purpose of containing an organic or inorganic spreading substance is to make the coating agent into a pasty or sprayable fluid using a dispersion medium, which will be described later, and to impart spreading and adhesion properties to the brick and castable surfaces, as well as to improve the coating properties after coating. Since the surface layer is carbonized by heating, it becomes even more difficult for the raw material powder to adhere to it. Furthermore, the coated layer thermally expands as heating progresses and tends to form a gap with the inner wall, so that even if the coating is stuck, it is likely to peel off. [Example] A situation in which the present invention was applied to a suspension preheater attached to a rotary kiln of N Cement Company M Plant will be described. Equipment used: Rotary kiln Diameter 4.2m, Length 61m Rotation speed 3 rotations/Min Kiln suspension preheater for Portland cement clinker firing Height 70M NSF type Powder raw material input rate 190ton/hour Exhaust gas temperature near input camber 1030~ 1100
℃ Inner wall material Basic firebrick

[Results of use]

As a result of repeating each of the above coating work tests three times, it was found that in the first test, there was almost no adhesion of raw material powder for each excipient after 15 days of operation, and after 20 days, there was no adhesion of raw material powder with a thickness of about 15 mm. Unlike conventional Atsuta, the adhesion was very soft, so it was easily peeled off by applying light vibrations without using high-pressure water jets. When the coating was applied during kiln operation, about 21 days later, raw material powder of about 15 cm in thickness remained attached, but it was peeled off by the same simple operation as above. As a result of repeating the above, the conventional clinker removal work three times a day is no longer necessary, and even if it occasionally sticks, it is easily peeled off by applying light vibrations, so the conventional removal work using high-pressure water jets is no longer performed. The amount of water required for conventional work was 30 to 40 tons per month, but it has been reduced to zero. By the way, the above explanation was given regarding the case where this invention is used in the suspension preheater inlet chamber, but it can of course also be used to prevent the adhesion of raw material powder to other parts of the suspension preheater, and it can also be used for cement clinker firing. The same results as in this example can be expected by adjusting the formulation of the coating agent not only in the equipment but also in a suspension preheater attached to a rotary kiln for firing lime, dolomite, magnesia clinker, alumina, etc. [Effects of the Invention] As explained above, the present invention provides a method to prevent raw material powder from adhering to the inner wall of the suspension preheater, where raw material powder tends to stick.
The simple method of forming a coating layer of specially formulated excipients can significantly reduce the adhesion of raw material powder, resulting in the following effects in the operation of cement firing equipment. 1) Decrease in preheating efficiency due to conventional coating removal work - reduction in raw material input - reduction in production of fired clinker is eliminated, and product productivity can be improved by 3 to 5%. 2) The large amount of water evaporation and the multiple suction of outside air associated with conventional coating removal work are eliminated, and the loss of thermal calories can be significantly reduced. 3) The coating removal work is approximately 1/40th of the conventional work, significantly reducing both the labor force and working time, and eliminating the dangerous work that was previously required. 4) Damage to the lining refractory caused by high-pressure water jet injection has been eliminated, extending the useful life of the furnace material. 5) It is no longer necessary to use the conventional high-pressure water usage of 30 to 40 tons/month.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing a rotary firing furnace and a suspension preheater attached thereto. In the figure, 1 ...suspension preheater, 6...rotary firing furnace.

Claims (1)

[Claims] 1. One or more layered lattice structure materials such as graphite, molybdenum disulfide, tungsten disulfide, boron nitride, mica, etc. and one or two heat-resistant binders such as alumina, silica, etc. are added to the necessary locations on the inner wall of the suspension preheater. Forming a coating layer of an excipient consisting of seeds, an organic or inorganic spreading substance such as starch, resin, sodium silicate, or aluminum phosphate, and water, mineral oil, or synthetic oil as a dispersion medium. A method for preventing the adhesion of raw material powder in a suspension preheater of a rotary firing furnace, characterized by: