RU2395773C1 - Procedure for control of envelope restoration on lining of rotating kiln - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: procedure for control of restoration of envelope on lining of rotating kiln consists in determination of degree of heating of rotating kiln case by temperature on its surface. Controlled by any known procedure jet of flow of compressed air and dust mixture is supplied into the kiln; also dust can be trapped from fumes of the rotating kiln. Controlled area of kiln case area is divided into a limited number of zones depending on length of the kiln or on setting. Degree of heating of kiln case surface is continuously measured by temperature of zones of its surface and their derivatives in time for each zone; this measured value is compared with process specified threshold values or settings. Coordinates of revealed points of deviations of current or measured temperatures in concrete zones are recorded, when preset thresholds are exceeded; thus there is obtained information on location of envelope chip. At chip passing between an upper point of a kiln roof and a lower end of chord of a layer of baked material the jet of air-dust mixture is supplied into the zone of a revealed chip. All operations of air-dust mixture supply are repeated to complete equalising compared temperature on kiln case surface in the zone of the revealed chip.

EFFECT: advanced defect revealing of lining and its efficient restoration.

1 cl, 2 dwg, 1 tbl

Description

The invention relates to the field of production of building materials, in particular to the production of cement or metallurgical clinker, and is intended to extend the service life of the lining of heating rotary kilns by eliminating chipping coatings without stopping the operation of the furnace.

Known methods and apparatus for controlling the temperature of materials inside the furnace by determining the degree of heating of the body (by the intensity of infrared radiation) and by the ratio of the intensity of dark and light (in the infrared range) sections on the outer surface of the furnace body, generating control actions on the process of firing the material in a rotary kiln [ 12].

However, the method according to [1] and implemented in the system [2], although the purpose and operations are close to the features of the claimed technical solution, they cannot solve the problem of controlling the process of restoring the coating on the lining of a rotary kiln without stopping it for a long time.

Closest to the proposed technical solution in terms of technical nature and the achieved result is the "Method of monitoring the condition of the lining and coating of a rotary kiln", known from [3].

Known in [3], the method (prototype) includes determining the degree of heating of the furnace body by the temperature of its surface, determining the rate of temperature growth over time, fixing its steady-state maximum value, and determining the thickness of the lining after cleavage by the calculation formula.

The disadvantage of the prototype is that:

- the time taken to detect a chip is large, including the time to reach the maximum growth rate of the temperature of the furnace body after cleavage of the coating and lining, V _max , which is from 20 minutes to 3 hours;

- the accumulation of errors for each of the determined parameters affects the accuracy of calculating the residual thickness of the lining after cleavage;

- errors of the operator or entity leading the determination of parameters are inevitable when implementing control by a calculation or inductive method;

- there is no possibility of eliminating chipping of the lining and coating (or separately) without stopping the operation of the furnace.

The technical result of the invention is to increase the service life of equipment by reducing thermal deformations of furnace elements by promptly identifying and eliminating chips or defects in the coating and lining of a rotary kiln without drastic changes in temperature, i.e. without stopping the normal operation of the furnace.

The achievement of the listed technical results of using the present invention is that a method for monitoring and controlling the process of restoration of the coating on the lining of a rotary kiln in addition to the known prototype includes the steps of: introducing into the furnace, by any known method, an adjustable jet of a mixture of compressed air and dust (e.g. dust trapped from the exhaust gases of a rotary kiln, then dust); dividing the controlled surface of the furnace body into a limited number of zones depending on the length of the furnace (from 3 to 30); assignments for each zone of technologically permissible values of temperatures and their derivatives; continuous measurement of the degree of heating of the furnace body according to the temperature of its surface zones and their growth rate over time; comparing the measured values with technologically predetermined thresholds and at the intersection of predetermined thresholds of information on the detection of chips; supply or direct a stream of compressed air with dust to the cleavage zone according to the obtained coordinates of the identified cleavage between the upper point of the furnace vault and the lower end of the chord of the calcined material layer, the last dust feeding operation being repeated until the compared temperatures of the furnace body surface are completely equalized in the identified cleavage zone.

To prove positive results from the use of distinguishing features, we will give a detailed description of the implementation of the proposed method.

The degree of heating of the furnace body by the temperature of its surface is measured by converting infrared radiation from the furnace body into a visible image or by a signal (see Fig. 1) from a thermal imager, which is known from [1-3].

The calcined material, for example cement clinker, in the sintering zone has a temperature of 1400-1450 ° C. At these temperatures, clinker has about 25-30% of the liquid phase. The resulting melt well wetts the surface of the refractory (lining), partially penetrates deep into the lining material, interacting with its components. For clarity of the physical processes of formation and elimination of chips, we turn to figure 2. In the text of the description of the invention, this figure is optional, because it is given only as additional information for illustration.

When the furnace rotates in the arc section P-N (Fig. 1), the surface of the clinker layer is heated by the radiation of the torch to 1500-1530 ° C. In this section of the PN arc (Fig. 1), the surface of the lining is coated with a layer of calcined material and the liquid phase on its surface, due to heat transfer to the layer of calcined material and through the lining to the environment, the temperature decreases to 1400-1420 ° FROM. The viscosity of the liquid phase increases, the adhesion strength of the clinker to the surface increases. This becomes enough to keep a layer of clinker granules with a diameter of up to 15-20 mm on the working surface of the lining when it leaves the calcined material.

After the lining section with an adherent layer of clinker granules enters the section of the BB arc and falls under the direct influence of the torch, the lining again begins to heat up more than 1420 ° C. The viscosity of the liquid phase begins to decrease and the adhering clinker granules again come off, being in the upper position of the furnace roof. Part of them is held on the working surface of the lining, as a rule, the smallest (figure 2). However, this does not always happen, because if a sufficiently deep or large cleavage of the lining or coating occurs, then in the upper (on the arch of the furnace) position through the cleavage, the temperature of the body under it heats up very quickly and this makes it impossible to hold the viscous phase with particles of clinker granules in place of the cleavage. Therefore, the size of the chip will only increase, and the thermal deformation of the furnace elements will increase due to an increase in the speed or rate of increase in the temperature of the body at the site of chip formation. Essentially, by measuring the value of the derivative of the temperature rise over time, the depth or size of the cleavage is indirectly measured or predicted.

Therefore, it is proposed to introduce into the furnace an adjustable, or controlled by flow rate, air-dust mixture flow. To quickly identify the place where the lining and coating are cleaved, the controlled surface of the casing is divided into a limited number of zones, and to ensure the given furnace performance and thermal performance indicators, technologically permissible temperatures and their derivatives for each zone are set (experimentally determined or calculations for specific furnaces and materials) . During operation of a rotary kiln, the mentioned temperatures and their derivatives are continuously compared (on comparison elements) and thereby the coordinates of the occurrence of chips are detected, and a stream with a controlled flow of “compressed air - dust” or circulating dusts is directed with the identified chip zone for the duration of the passage of the latter the arc section 1/2 L-B and to the lower end of the chord of the material (figure 2). In this case, a chip filled with a liquid phase and small fractions of dust and clinker granules in the lower part of the furnace under a layer of fired material (in the arc section NL in (Fig. 2) begins to cool due to heat transfer to the fired material layer and through the lining - The viscosity of the liquid phase in the chip increases, the adhesion of the clinker to the refractory increases. As the chip leaves the calcined material layer, the radiation temperature of the torch onto the chip increases. Moreover, due to the onset of re-melting of the clinker: The granules begin to fall out of the chip or are replaced by fine dust. Most of the compressed air-dust mixture flow directly into the chip. As it is filled, the temperature inside the chip decreases to the specified temperature of the chip location zone, which is a sign of restoration of the coating and lining. the lining could not be completely restored during the first rotation of the furnace, then all operations are repeated at the next (their) rotation (s).

An example of the implementation of the proposed method for monitoring the state of magnesite-chromite lining (thickness 235 mm) and coating of a rotary kiln.

The tests were carried out when a chip appeared on the most stressed section of the furnace. The following values of the temperature change of the furnace body and its derivative are obtained.

Time - t, sec 0 60 180 240 300 360 420 480 540 600 660 720 The temperature of the furnace body in the cleavage zone - T _to , ° C 220 238 290 343 404 492 423 366 317 283 254 239 Derivative dT _c / dt, ° C / min 0 0.3 0.4 0.9 1,0 1,5 -1.2 -1.0 -0.8 -0.6 -0.5 -0.3

The temperature of the surface of the furnace body was measured by a scanning thermal imager in conjunction with the Thermoscan program, with a scan of the controlled surface of the body and the output signal (Fig. 2) to the program for converting an electrical signal to the temperature of the body. The frequency of scanning a thermal imager of the entire surface of the housing is 8 times per second. Upon reaching the derivative value of 1.5 ° C / min, a directed flow of the air-dust mixture was supplied to the cleavage after it exited from the calcined material.

As can be seen from the table, T _k in the cleavage zone after 3 min began to drop sharply and after the flow of the “dusty air stream” stopped (600 seconds), the temperature T _{k was} established approximately at its initial (predetermined value), which indicates the restoration of the coating in the considered area lining.

We emphasize that all measurements, comparisons, setting temperatures, their derivatives and other operations are performed by means of electrical signals using the software of thermal imagers and regulatory bodies. The time to identify a chip and its recovery, in comparison with the operator’s work, is 12-15 times less. In addition, possible operator errors are excluded. Identification and restoration of cleavage is carried out without stopping the furnace and the value of the derivative of temperature over time (and do not wait until it reaches its maximum value, as is done in the prototype [3].

Thus, the combination of known and distinctive features of the proposed method almost completely eliminates the possible emergency state of the coating or lining, increases its service life and housing elements by at least 2-3 times.

Information sources

1. Salikhov Z.G., Salikhov K.Z. A method of controlling the process of firing materials in a rotary kiln. Patent for the invention of the Russian Federation No. 22979775. Bull. No 10 on April 10, 2005

2. Salikhov Z.G., Shubin V.I., Bekarevich A.A., Salikhov K.Z. A control system for the process of firing material in a rotary kiln. Patent for the invention of the Russian Federation No. 2232959. Bull. No. 20 dated July 20, 2004 (MKI: F27B 7/42; F27D 19/00).

3. Shubin V.I., Gnedina I.A., Sokolinskaya Ch.A., Gorban T.M. A method for monitoring the condition of the lining and coating of a rotary kiln. A.S. for the invention No. 1086331. Bull. No 14 on 04/15/84

Claims (1)

A method for monitoring and controlling the process of restoration of the coating on the lining of a rotary kiln, including determining the degree of heating of the rotary kiln body according to its surface temperature, characterized in that an adjustable stream of a mixture of compressed air and dust, for example dust collected from the waste, is introduced into the furnace by any known method gases of a rotary kiln, divide the controlled surface area of the kiln shell into a limited number of zones depending on the length of the kiln, task or set point, for each zone technologically temperature values and its derivatives, continuously measure the degree of heating of the furnace body surface according to the temperature of its surface zones and their derivatives in time, compare the measured values with the technologically set thresholds or settings, and when the set thresholds are crossed, the coordinates of the detected deviation points of the current or measured temperatures are recorded in specific areas, and thereby receive information about the location of the cleavage of the coating and in the area of the identified cleavage serves (direct) a stream of air-dust mixture when the cleavage between the upper point of the furnace vault and the lower end of the chord of the calcined material layer, all the operations of feeding the dusty air stream are repeated until the compared temperatures of the surface of the furnace body are completely equalized in the area of the identified chip.

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