RU2452913C2 - Method of controlling industrial furnace state - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed method comprises defining temperature variations in furnace lining thermal state. Furnace outer surface temperature is measured on all sections or on one section without interrupting operation with the help of IR-spectrum temperature meter, IR-imager or pyrometer to define heat losses by mathematical equation.

EFFECT: higher accuracy.

4 dwg

Description

The invention relates to ferrous metallurgy and is intended to monitor the condition of the lining of an industrial furnace, namely, a thermal furnace for heating material, without changing its state of aggregation.

Improving control over the processes that occur during the operation of industrial furnaces is a prerequisite for increasing the energy efficiency of production and improving the environment.

The need for control over the processes that occur in the furnace lining is due to the fact that the furnace lining is the main structural element that isolates the heat exchange process between the heat carrier and the heated body.

The heat loss that occurs through the lining of the furnace, in direct proportion determines the efficiency of the furnace and the amount of fuel (energy) consumed.

To control the processes of changing the size of the working layer of the lining of industrial - metallurgical, blast furnaces, various control methods have been developed.

A known method of monitoring the condition of the lining of the hearth of a blast furnace, described in the description of the invention to the patent of the Russian Federation No. 2299910, IPC C21B 7/24 from 07/07/2007, publ. 02.10.2007., Which includes measuring the temperature in the lining using several temperature sensors (m) located along the belts (n) and radii (r), into which the lining of the furnace metal detector is conventionally divided, where (m) is the number of the temperature sensor in the r- direction radius, determination of the changes in the thermal state of the furnace lining of the blast furnace by signals of temperature sensors, characterized in that, after checking the signals from each functioning sensor for readability and their reliability, effective temporary sequences, which are then subjected to structural analysis using a mathematical transform of the wavelet, the wavelet is calculated values of mathematical expression index

,

,

, а изменение в тепловом состоянии футеровки горна доменной печи констатируют при синхронном появлении экстремальных значений вейвлет-показателя на всех заданных уровнях детализации структуры сигнала функционирующего термодатчика.where x (l) is the actual value of the analyzed signal at the 1st moment of time; φ * ( a , b) - type of nonlinear weight function - wavelet basis; а - scaling parameter; b is the parameter of displacement along the time axis; L is the number of data on the moving interval of calculating the wavelet indicator, remember the calculated values of the wavelet indicator, determine the extreme value of the wavelet indicator at the current time at all levels of detail of the signal structure from the set of stored calculation data

and a change in the thermal state of the furnace lining of the blast furnace is observed with the simultaneous appearance of extreme values of the wavelet index at all given levels of detail of the signal structure of a functioning temperature sensor.

In industry, the control of the technical condition of the lining is carried out according to recommendations from various numerous analogues:

- M.A. Glinkov // Metallurgical furnaces, part 1. - M .: State scientific and technical publishing house of literature on ferrous and non-ferrous metallurgy, 1963, pp. 199-205;

- A.S. Telegin and N.S. Lebedev // Designs and calculation of heating devices, ed. the second one. - M.: Engineering, 1964, table 53, p. 269 shows the service life of the masonry of the vault, walls and hearth.

- The system of preventive maintenance of power equipment at industry enterprises. - M.: Research Institute of Technology and Organization, 1972, part 2, book 1, in table 9-1, p. 15-16, p. 3-10.

From analogues it is known that the technical condition of the lining of the furnace is examined, as a rule, when it is completely stopped and cooled, by inspecting the furnace in a certain volume.

The methods and recommendations given for comparison as known analogues do not solve the problem of determining the relative magnitude of energy consumption and have disadvantages:

- the technical condition of thermal insulation on working industrial furnaces is determined subjectively by inspection of the outer surface, mathematical calculations are not used, the accuracy of determining the technical condition is low;

- suggest a partial destruction of the lining for the installation of control sensors or direct contact with the lining of the furnace, the temperature of the outer surface of which can be heated to a temperature significantly higher than the maximum allowable for safe contact with parts of the body of the researcher;

- the subjective factor - visual, external inspection of the furnace is currently the main one - to "clarify" the actual condition of the lining and thermal insulation of industrial heating furnaces when it is stopped. The accuracy of determining the actual technical condition is low and depends on the qualifications and experience of the staff;

- at the same service life of the furnace, its technical condition may vary from the state of suitability for work to the state of unsuitability for work and partial destruction of the structure. The accuracy of determining the actual state by service life is low.

Known analogues do not allow to evaluate the efficiency of the lining and thermal insulation in dynamics during operation of the furnace and thereby plan ahead for the repair of the furnace.

Effect: increasing the accuracy of control over the state of thermal insulation and lining of a heating furnace without stopping its operation.

The technical result is achieved due to the fact that in the method of monitoring the condition of the lining of an industrial furnace, including determining the temperature changes in the thermal state of its lining, measure the temperature of the outer surface of the furnace in all its sections or selectively in one of the sections without stopping the operation of the furnace using infrared instruments measuring temperature, thermograph, thermal imager or pyrometer and determine the value by calculating the relative value of the actual heat loss through the laying of the stove and in mathematical terms:

ΔQ = 62∑ _i S _{surface i} (t _{ext .i} -t _calc. ) + 64∑ _i S _{ext. out gases i} (kJ / hour),

where ΔQ is the value of heat loss from the outer surface of the furnace (kJ / hour);

62 is the value of the heat transfer coefficient by radiation and convection from the outer surface of the furnace, (kJ / ° C hour),

∑ _i S _{out surface i} is the area of all sections of the outer surface of the furnace lining that do not have signs of exit of furnace gases (m ² );

t _ext.i -t _calc. - the temperature difference t is _external.i is the temperature of the outer surface of the furnace installed during measurements, and t _calc. - the set or calculated temperature of the outer surface in accordance with the design of the furnace from all sections of the outer surface of the furnace that does not have signs of the exit of furnace gases (K),

∑ _i S _{out surface i} - the area of all sections of the outer surface of the furnace with signs of exit of furnace gases (m ² );

64 is the mathematical value of heat loss with exhaust gases consisting of natural gas combustion products passing through the furnace lining to the outside at a speed of 0.15 m / s and a temperature of 20-300 ° C, (kJ / m ² hour).

The inventive method allows to conduct a survey of a working furnace and to identify deviations in the lining of industrial furnaces - furnaces made of solid and fibrous materials, furnaces with sheet steel lining during their operation and others.

The inventive method is based on obtaining the values of the relative magnitude of heat loss from the outer surface of the furnace using objective control methods, subsequent heat engineering calculations based on the basic theoretical principles of heat engineering, analyzing the causes of deviations and taking into account the service life of the furnace lining. Only one value is directly obtained from the furnace: the temperature of the outer surface, while the researcher is at a distance that excludes the influence of the temperature factor (radiation) on parts of his body, and the use of high-tech temperature measuring devices will allow the researcher to obtain a planar image of the outer surface of the furnace, automatically save the picture in the memory of the device, with a high degree of accuracy to process the data.

A comparative analysis of the presented solution with analogues allows us to conclude that the claimed invention meets the conditions of patentability: it is new, has an inventive step and industrial application.

A comparison of the proposed method with analogues shows that the claimed method differs from the known ones in that

- it is not necessary to control the temperature of the material directly in the lining layer;

- it is not required to stop loading materials into the furnace for a long period without changing external parameters, i.e. the oven can work in normal, normal mode;

- the moment of measuring the parameters changes - the temperature of the outer surface of the furnace is measured during stabilization of the temperature inside the furnace space;

- there is no destructive or other impact on the lining for the installation or implementation of various control bodies.

The novelty of the proposed method lies in the fact that to determine the relative magnitude of heat loss, a new dependence is proposed that takes into account heat loss by convection, radiation, filtering of the furnace gases through the masonry, depending on changes in the temperature of the outer surface of the furnace, the surface area of the furnace, and the surface area of the furnace with signs exit of furnace gases through the masonry.

Figure 1 shows a diagram for determining the measurement of temperature at predetermined points on the surface of the furnace;

Figure 2 shows a diagram of temperature measurements at predetermined points, from places on the outer surface of the furnace having signs of exit of furnace gases;

Figure 3 shows a diagram of temperature measurement in predetermined sections of the surface of the furnace;

Figure 4 shows a diagram of temperature measurements in predetermined sections of the surface of the furnace.

A method for monitoring the condition of the lining of an industrial furnace includes monitoring the relative amount of heat loss from the outer surface of industrial furnaces 1-12 times a year, periodically examining a heating industrial furnace 1-3 times a year and consisting of examining and checking the health and operability of all nodes, mechanisms and structural elements of the furnace, technical control of the operating modes of the furnace, for a gas-fired furnace consisting of control of fuel consumption, the ratio of fuel and oxidize spruce (gas and air), above the overpressure in the working space, above the vacuum in the removal system of the combustion products and their temperature, if necessary, correcting the following deviations: the ratio of the volume of gas supplied for combustion to the furnace and air supplied to the combustion of gas , by increasing or decreasing the air volume or the volume of natural gas using the furnace controls or burner devices to the parameters of the optimal gas-air ratio structurally specified in the burner device f, excess pressure in the furnace and rarefaction in the smoke exhaust system by reducing or increasing the bore of the smoke exhaust channel of the furnace with a gate using the gate controls or changing the engine speed of the smoke exhaust pump drive to the parameters specified in the mode map that is made for each furnace, an electric furnace, after checking the electrical circuits and the readings of the devices on the regime map; after determining the constant stable temperature in the furnace t _vn (° C) during technological exposure, determining the ambient temperature of the furnace t surrounding _. (° C) when examining 1-3 times a year and when monitoring the relative magnitude of heat loss 1-12 times a year. To compare the results and the subsequent analysis of changes in the relative magnitude of heat losses during repeated examinations and monitoring, the temperature in the furnace during the examination and monitoring should be equal to the temperature of the previous examination with deviations not exceeding 50 ° С. Moreover, the temperature determination of the outer surface of the furnace is carried out in all areas or selectively on one of the sections of the outer surface of the furnace using infrared instruments for measuring the temperature of a thermograph, or a thermal imager 5, or pyrometer 3 by remote temperature measurement in predetermined sections of the surface plane 4 or at specified points 2 . For the process of determining the temperature of the outer surface of the furnace with a temperature measurement at predetermined points 2, instruments that measure the temperature Only at the point of direct pointing of the scanning device, for example, the pyrometer 3 of the infrared measurement range.

Measurements of the temperature of the outer surface t of the _outer . they are produced on the geometric plane 4 of the outer surface of the furnace systemically, through equal distances with the establishment of axial distances in a flat coordinate system. The results of the examination are drawn up in the form of a diagram (Fig. 2), which indicates the places on the outer surface of the furnace that have signs of exit of furnace gases, indicating the area of localization, signs of leakage of thermal insulation, visible changes in the refraction of light at the interface between air and volumetric mass of furnace gases knocked out lining. From the results obtained, the value of ∑t _ext. - the average temperature of the outer surface of the studied areas, which is found as the arithmetic mean.

The process of measuring the temperature of the outer surface of the furnace can be performed in predetermined planes 4 using a thermograph or thermal imager 5 of the infrared measurement range, which allows to obtain contrast or color images of the temperature on the geometric plane 4 of the outer surface (figure 3).

In the control settings of the device of the thermograph or thermal imager 5, a fixed range of temperature values from 40 to 200 ° C is set.

Measurements of the temperature of the outer surface t of the _outer . produce pictures of geometric planes 4 of a given section of the outer surface of the furnace, make up a diagram (Fig. 4) of the studied fragments of the outer surface areas. The survey results (pictures) are stored in electronic form in the memory of the device, the designations of the pictures are recorded on the circuit. In the diagram, pictures of places on the outer surface, which have signs of the exit of furnace gases, indicating the area of localization are noted. Signs of the exit of furnace gases through the furnace lining, which are revealed during thermography as areas of a relative increase in temperature, visible on the display of the device, areas are characterized by an increased temperature background and clearly distinguishable clear boundaries of places of elevated temperature, which, as a rule, coincide with masonry joints or damage to the metal sheathing frame. The exit regions of the furnace gases are visible in a lighter tone and, as a rule, coincide with the boundaries of the masonry joints. Calculation of ∑t _ext. - the average temperature of the outer surface of the investigated areas to obtain the result is found as the arithmetic mean.

Processing of the results includes:

calculation of the temperature of the outer surface of the furnace t _calc ,

calculation of the relative value of heat loss ΔQ,

establishing the reasons for the formation of ΔQ,

ΔQ calculations in monetary terms € _{(monetary units)} ,

the conversion of the relative loss ΔQ to ΔW is the power loss of the electric furnace due to heat loss from the outer surface by ΔQ for processing the results of the inspection of the electric furnace,

calculations of ΔW in monetary terms € _{(monetary units)} , which are performed as follows:

calculation of the temperature of the outer surface of the furnace t _calc. carried out by the formula

t _calc. = t _environment + Q _settlement / α _nar. (° C)

where t _surround - determined during preparation for the inspection of the furnace.

Q _settlement - determine for the heat flux in the multilayer masonry, provided that the temperature of the inner surface of the masonry with an acceptable approximation is equal to the temperature in the furnace during the inspection - t _int :

Where

- соответственно толщина каждого слоя многослойной кладки, деленная на коэффициент теплопроводности материала слоя; значение толщины каждого слоя стенки берут из паспортных (проектных) характеристик печи; значение коэффициента теплопроводности из справочных данных материала слоя;

- respectively, the thickness of each layer of the multilayer masonry, divided by the coefficient of thermal conductivity of the material of the layer; the thickness value of each wall layer is taken from the passport (design) characteristics of the furnace; thermal conductivity value from the reference data of the layer material;

t _vn -t _ok - the relative difference between the calculated temperature inside the furnace and the ambient temperature, the value of t _{vn is} taken from the readings of temperature measuring devices in the furnace control point or measured with a pyrometer 3; the temperature outside the furnace t _ok take 303 ° K (30 ° C) and is due to the most common temperature conditions for furnaces installed in closed heated rooms, directly at the casing or over the arch 1 of the furnace;

α _nar - heat transfer coefficient by radiation and convection is taken equal to the calculated value:

α _nar = 62 kJ / (m ² ° С hour).

According to the results of measurements previously performed on the outer surface of the furnace, the actual value of the relative value of the heat loss ΔQ through the masonry is calculated according to the formula:

ΔQ = 62∑ _i S _{surface i} (t _ext.i -t _{calc. I} ) + 64∑ _i S _{out. surface} (kJ / hour);

Where

ΔQ - the total value of the relative magnitude of heat loss from the outer surfaces of the furnace from different in their structural purpose sections of the outer surface of the furnace;

62 kJ / (m ² ° C hour) - a known, conditionally constant, with sufficient approximation for calculations value of the mathematical expression of the heat transfer coefficient by radiation and convection from the outer surface - α _nar. ,

∑ _i S _surface (t _ext. -t _calc. ) - the total value of the temperature difference t _ext. - the actual temperature of the outer surface established during the measurements, and t _calc. - a given temperature of the outer surface according to the design of the furnace (calculated) from all sections of the examined outer surface that does not have signs of the exit of furnace gases (m ² K);

averaged value of t _ext. - the actual temperature of the outer surface - according to the scheme (figure 2 or figure 4);

∑ _i S _{out surface i} is the total value of the external surface area of the furnace, with signs of the exit of furnace gases (m ² );

64 (kJ / m ² hour); - conditionally constant, with a sufficient approximation for calculations, the value of the mathematical expression of heat loss with exhaust simple gases Q _select. as a part of natural gas combustion products with a temperature of 200-300 ° C, through a lining with a speed of 0.15 m / s, made of shaped products in accordance with GOST 8691-73 (ISO 5019-1-84, ISO 5019-2-84, ISO 5019-5-84) “Refractory products for general use. Shape and dimensions (as amended by N 1-4), through damaged masonry joints 3 mm. The quantity Q _sps. in approximate calculations it will be constant and in the method by calculation it is defined as 64 kJ with 1 m ^{2 of} area in 1 hour. The quantity Q _sps. will be equal to zero in the absence of signs of infiltration of furnace gases through the masonry and for electric furnaces, without forced circulation of the atmosphere.

Formula: ΔQ = 62∑ _i S _{surface. i} (t _{ext . i} -t _{calc. i} ) + 64∑ _i S _{out. surface} (kJ / hour) - in the present method forms the basis for calculating heat loss and is intended to determine the relative value of heat loss from the outer surface of the furnace by convection, radiation, gas infiltration through the masonry in proportion to the increase in the temperature of the outer surface.

When calculating the ΔQ value for industrial furnaces using electric energy, without forced mixing of the atmosphere, gas infiltration through the masonry does not occur, the value of the surface area of the outlet of the furnace gases is S _{o. surface} taken equal to zero, S _{o. surface} = 0, and the formula for calculating the relative value of heat loss ΔQ = 62∑ _i S _{surface. i} (t _ext . _i -t _{calculation i} ) + 64∑ _i S _{out. surface} (kJ / hour), is converted into the formula for the loss of electric power, ΔW for 1 hour, in direct proportion to changes in the temperature of the outer surface of the furnace and takes the form:

ΔW = 0.017∑ _i S _{surface i} (t _{ext. I} - t _{calc. I} ), kW / m ² ° C per hour.

The formula is the main one for calculating the power loss of an electric furnace for reasons of heat loss from the outer surface.

Then, the results of the furnace inspection are entered into the furnace inspection report, which is signed by the persons directly conducting the examination, calculations and commenting on the pictures (diagrams).

The result - the value of ΔQ, from each section of the survey, thermograph images, measurement schemes (figure 2 and figure 4) - indicate in the report. Additionally, the report indicates the main reasons for the formation of the ΔQ value in the form of comments on images or measurement schemes.

The inventive method describes the main causes of heat loss generated on the outer surface of the furnace, not provided by the furnace design, considers factors contributing to changes in the overall thermal resistance of the lining or the appearance of local heating of the external surface due to:

- the total operational wear of the lining (masonry) - is determined by the term of its actual work and the standards of the enterprise by the timing of repairs (overhaul period),

- influence of factors: vibration from presses and hammers, vibration from electrical installations - parts of the furnace structure, aggressiveness of the furnace environment, mechanical impact on the lining of the moving structural elements of the furnace (rotating or withdrawable under and others), if any factors are present;

- a decrease in the thermal resistance of the masonry due to shrinkage of the materials of the lining (masonry) or an increase in its thermal conductivity due to the low quality of structural materials - take into account the presence of local places of heating of the outer surface and the presence of signs of penetration of furnace gases through the lining of the furnace;

- decrease in the thickness of the lining for reasons related to the chemical interaction of the lining material with the furnace medium;

- inefficiency of the furnace gas removal system and automatic pressure maintenance in the furnace;

- technological level of the furnace: fuel combustion technology, furnace construction technology, technology for regulating temperature, pressure and other parameters;

- compliance of the production technology with the technical capabilities of the furnace.

According to the results of the analysis, a comparison of indicators: the actual furnace life and the standard service life, the obtained value of the heat loss with the calculated value, the general technical condition of the furnace and the degree of influence of additional factors to increase the lining wear: vibration, furnace environment, quality of the lining material, make a conclusion if necessary, study the influence of various reasons and factors on the condition of the furnace lining.

Statistical collection and storage of data on changes in the temperature of the outer surface of the furnace over time are carried out, measures to correct deviations are outlined.

The correction of temperature deviations of the outer surface of the furnace, the technical condition of the masonry (lining) and the efficiency of the thermal insulation device is carried out during furnace repairs by restoring the lining and thermal insulation.

Repair of the furnace entails costs. Costs are usually determined by the suitability of the furnace or its individual structural elements for use.

The furnace may be suitable for production, but the operation of the furnace may have a relatively high cost due to undetermined additional fuel costs of €.

€ - the amount of additional costs for the purchase and transportation of natural gas to the furnace, associated with deviations in the technical condition of the masonry (lining).

Comparison of repair costs or costs of changing the design of the furnace with the costs associated with the deviation of the technical condition of the masonry (lining) is a necessary action to determine the economic feasibility of repair or modernization.

The described inventive method allows you to objectively determine the costs € associated with the deviation of the technical condition of the masonry (lining). Costs are defined as the ratio of the relative amount of heat loss (energy loss) to the cost of the energy carrier.

The determination of the cost of fuel costs depending on the relative amount of heat loss for - natural gas, where the amount of relative heat loss - ΔQ are in monetary terms € _{(monetary units per hour)} , the following: calculate the value (volume) of natural gas V _gas , which must be burned in the furnace to obtain the value of heat loss ΔQ associated with deviations of the technical condition of the masonry (lining) from normal, according to the formula:

V _gas = ΔQ / Q _combustion (m ³ )

Where

V _gas is the volume of natural gas necessary for the formation of ΔQ during combustion;

ΔQ is the obtained relative amount of heat loss determined by the present method;

Q _{burned fuel} - the calorific value of natural gas supplied to the enterprise. Calorific value information is contained in the quality certificate.

The main economic calculations for the turnover of natural gas are made in 1000 m ³ . To determine the cash equivalent value of 1000 m ^{3 of} natural gas - € _{1000 cubic meters. m the} value of the cost is taken into account the costs within the enterprise (expenses for transportation, reduction, dehydration of natural gas; expenses for the maintenance of gas pipelines; expenses for various examinations and diagnostics of gas pipelines; expenses for the maintenance and calibration of commercial gas meters and other expenses).

The expression of the heat loss ΔQ in monetary terms € takes the form:

€ _{(monetary units)} / per 1 hour = € _{1000 cu m} (ΔQ / Q _{combustion fuel} ) / 1000,

Where

€ _{1000 cu m} - the cost of 1000 m ^{3 of} natural gas;

ΔQ is the relative value of heat loss calculated by the basic formula:

ΔQ = 62∑ _i S _{surface i} (t _{ext. i} -t _{calculation i} ) + 64∑ _i S _{out. surface} (kJ / hour)

Q _{burned fuel} - calorific value of fuel, which is indicated in the certificate of quality of natural gas.

Formula € _{(monetary units)} / in 1 hour = € _{1000 cubic meters. m} (ΔQ / Q _{combustion fuel} ) / 1000 - is the main one for calculating the additional cash costs for the purchase of natural gas in direct proportion to the relative value of heat losses ΔQ.

When calculating the ΔQ value for industrial furnaces using electric energy, gas infiltration through the masonry does not occur, the value of the surface area of the outlet of the furnace gases is S _{o. surface} taken equal to zero S _{o. surface} = 0, and the formula for calculating the relative value of heat loss ΔQ = 62∑ _i S _{surface. i} (t _{ext. i} -t _{calculation i} ) + 64∑ _i S _{out. the surface} (kJ / hour) is converted into a formula for calculating the consumed power ΔW of electricity per hour depending on the change in temperature of the outer surface of the furnace, which takes the form:

ΔW = 0.017∑ _i S _{surface i} (t _{ext. i} -t _{calc. i} ), kW / m ² ° С per hour,

the value of € _{(monetary units)} is defined as:

€ _{(monetary units)} = ΔQ (kW / m ² ° C per hour) / € _{cost 1 kW / h.}

The formula: € _{(monetary units)} = ΔQ (kW / m ² ° C per hour) / € _{cost 1 kW / h} - is the main one for calculating the additional cash costs for electricity payment in direct proportion to the relative amount of heat loss ΔQ converted to thermal power.

A method for monitoring the condition of the lining of an industrial furnace is implemented as follows.

For accuracy and reliability of forecasts for the further operation of an industrial furnace, the method is carried out in conjunction with organizational measures. The company organizes monitoring and diagnostics of the furnace industry with providing researchers with temperature measuring instruments: a pyrometer 3 in the infrared range with a measurement range from 20 to 400 ° C or a thermograph, or a thermal imager 5 working in the infrared range in the temperature range from - 20 to + 360 ° C. The thermograph should have the following options: protection of the matrix from radiation exceeding the permissible values for the functionality of the device; pointing the axis of the lens at the laser pointer; electronic memory with the ability to store and save at least 50 pictures; in thermograph controls, it should be possible to manually adjust (select) the temperature range; the complete set of thermograph software should ensure the processing of images on a computer (the ability to copy and paste into electronic documents). Organize records of monitoring and inspection, collection of statistical data on the results of the survey for each furnace. Specialists are trained in techniques for using temperature measuring devices and data processing. A sample examination of an industrial furnace according to the claimed method allows a decrease in the reliability of the analysis and the establishment of the causes of deviations in the lining, while the accuracy of the mathematical calculations of this method is maintained.

Directly on the furnace, examinations are performed in the following order. Inspect and verify the serviceability and operability of all nodes, mechanisms and structural elements of the furnace. Carry out technical control of the furnace operating mode and set the furnace operation parameters according to the values of the regime map. In electric furnaces, electrical circuits are checked. A constant temperature t _vn (° C) is established and maintained inside the furnace, if the examination is repeated, then the value of t _vn (° C) should be set equal to the value of t _vn (° C) of the previous examination. The value of t _vn (° C) - should be equal to the value of the process temperature for heating the main product. Determine the ambient temperature at the furnace _circle t (° C); make up a measurement chart at predetermined points 2 (Fig. 1) or specified surfaces 4 (Fig. 3), a measurement chart for predetermined surfaces are made without inserting pictures that are obtained only when measuring to determine the temperature of the outer surface of the furnace. The temperature of the outer surface of the furnace or of the outer surface is determined using infrared instruments for measuring the temperature of the pyrometer 3 or a thermograph or thermal imager 5 by measuring the temperature in predetermined sections of the surface plane 4 or at predetermined points.

In the measurement scheme at the set points 2 (Fig. 1), the temperature values at the set points are recorded after each temperature measurement. On the measurement scheme in the given planes 4 (Fig. 3), the designations of the images, surfaces in the given coordinate system are pre-recorded, the images are stored in a certain sequence in the electronic memory of the thermograph or thermal imager 5, the circuit is finally made using electronic information processing by inserting the images into the circuit . The image contains the value of the outer surface of each plane 4 specified for the examination. The value of наружt of the _outer - average temperature of the outer surface of the studied areas is calculated as the arithmetic average value when examined with a pyrometer 3, a thermograph, or a thermal imager 5.

The calculated temperature of the outer surface of the furnace is determined for each section that has differences in the size of the lining thickness, the structural material and the thermal insulation device.

Calculation t _calc. carried out by the formula

t _calc. = t _environment + Q _settlement / α _nar. (° C)

where, t _surround - ambient temperature;

Q _settlement - determine for the heat flux in the multilayer masonry, provided that the temperature of the inner surface of the masonry with an acceptable approximation is equal to the temperature in the furnace during the inspection - t _int :

Where

- соответственно толщина каждого слоя многослойной кладки, деленная на коэффициент теплопроводности материала слоя; значение толщины каждого слоя стенки берут из паспортных (проектных) характеристик печи; значение коэффициента теплопроводности из справочных данных материала слоя;

- respectively, the thickness of each layer of the multilayer masonry, divided by the coefficient of thermal conductivity of the material of the layer; the thickness value of each wall layer is taken from the passport (design) characteristics of the furnace; thermal conductivity value from the reference data of the layer material;

t _vn -t _ok - the relative difference between the calculated temperature inside the furnace and the ambient temperature, the value of t _{vn is} taken from the readings of temperature measuring devices in the furnace control point or measured with a pyrometer 3; the temperature outside the furnace t _ok take 303K (30 ° C) and is determined by the most common temperature conditions for furnaces installed in closed heated rooms, directly at the casing or over the arch 1 of the furnace;

α _nar - heat transfer coefficient by radiation and convection is taken equal to the calculated value:

α _nar = 62 kJ / (m ² ° С hour).

According to the results of measurements previously performed on the outer surface of the furnace, the actual value of the relative value of the heat loss ΔQ through the masonry is calculated according to the basic formula:

ΔQ = 62∑ _i S _{surface i} (t _{ext. i} -t _{calc. i} ) + 64∑ _i S _{out. surface} (kJ / hour)

Where

ΔQ - the total value of the relative magnitude of heat loss from the outer surfaces of the furnace, with different in their structural purpose sections of the outer surface of the furnace;

62 kJ / (m ² ° C hour) - a known, conditionally constant, with sufficient approximation for calculations value of the mathematical expression of the heat transfer coefficient by radiation and convection from the outer surface - α _nar ,

∑S _surface (t _ext. -t _calc. ) - the total value of the temperature difference t _ext. - the actual temperature of the outer surface established during the measurements, and t _calculation - the set temperature of the outer surface according to the design of the furnace (calculated) from all sections of the examined outer surface that does not have signs of the exit of furnace gases (m ² ° C).

The average value of t _ext. - the actual temperature of the outer surface - according to the scheme (figure 2 or figure 4);

∑S _{out. surface i} - the total value of the outer surface of the furnace with signs of exit of furnace gases (m ² ),

64 (kJ / m ² hour) - conditionally constant, with approximation sufficient for calculations, the mathematical expression of heat loss with exhaust simple gases in the composition of natural gas combustion products, with a temperature of 200-300 ° C, through the lining at a speed of 0.15 m / s, made of shaped products in accordance with GOST 8691-73 (ISO 5019-1-84, ISO 5019-2-84, ISO 5019-5-84) “General refractory products. Shape and dimensions (as amended by N 1-4), through damaged masonry joints 3 mm. The quantity Q _sps. with approximate calculations it will be constant. The quantity Q _sps. will be equal to zero in the absence of signs of infiltration of furnace gases through the masonry and for electric furnaces without forced circulation of the atmosphere.

When calculating the ΔQ value for industrial furnaces using electric energy, without forced mixing of the atmosphere, gas infiltration through the masonry does not occur, the value of the surface area of the outlet of the furnace gases is S _{o. surface} taken equal to zero, S _{o. surface} = 0, and the formula for calculating the relative value of heat loss ΔQ = 62∑ _i S _{surface i} (t _{external. i} -t _{calculation i} ) + 64∑ _i S _{out. surface} (kJ / hour) is converted into the formula for the loss of electric power, ΔW for 1 hour, in direct proportion to changes in the temperature of the outer surface of the furnace and is used for calculations in the form: ΔW = 0,017∑ _i S _{surface i} (t _{external. i} -t _{calc. i} ), kW / m ² ° C per hour.

Then, the furnace inspection results are entered into the furnace inspection report, and the main causes of heat losses formed on the outer surface of the furnace that are not provided for by the furnace design are established, for which the most significant wear factors are determined:

- the actual time of operation of the furnace is compared with the standard service life and the timing of repairs (overhaul period), if the ratio of the actual operation of the furnace to its service life is close to the normative or exceeds the standard period, then the operational wear factor is indicated in the report as determining the reason;

- the influence of vibration factors from presses and hammers, vibration from electrical installations - part of the furnace structure, aggressiveness of the furnace environment, mechanical impact on the lining of the moving structural elements of the furnace are taken into account, if any factors are present, are defined in the report as factors that increase the intensity of wear of the lining or for blacksmith furnaces production - determining the cause of wear, if in the forge furnaces there are signs of infiltration of furnace gases through the masonry; along the masonry seams.

- a decrease in the thermal resistance of the masonry due to shrinkage of the materials of the lining (masonry) or an increase in its thermal conductivity due to the low quality of structural materials or the quality of construction work - indicate in the report as the determining reason for the presence of local places of heating of the outer surface, deformation of structural elements and visible shrinkage masonry material; the reason is considered the determining factor when the furnace is less than half of the standard service life or the overhaul period;

- a decrease in the thickness of the masonry due to the interaction of the furnace environment with the lining material is indicated as the determining reason if the wear process of the lining is the most short-lived process in time, in relation to other processes, namely: the process of wear of the lining during heat exchanges, long service life (standard term), abrasive wear of the lining by a gas-dynamic flow.

- inefficient operation of the furnace gas removal system and automatic pressure maintenance in the furnace is indicated in the report and considered the main factor in the wear of the lining in the presence of signs of exit of furnace gases through the masonry on most of the surface of the furnace in the absence of other factors;

- the technological level of the furnace, the technology of burning fuel, the technology of building the furnace, the technology of regulating temperature, pressure and other parameters are taken as an additional circumstance and are indicated in the report when comparing the actual value of the temperature of the outer surface t _outer. with normative values of maximum permissible temperature values established by sanitary-hygienic standards.

The report comments on all the main causes of wear and the degree of influence of wear factors. Comments accompany pictures or measurement patterns.

The report calculates the value of ΔQ in monetary terms €.

There is a distinction between the calculation of ΔQ for industrial furnaces using natural gas as a fuel and furnaces using electric energy for heating.

For furnaces that use natural gas as fuel, economic losses are determined as follows.

Calculate the value (volume) of natural gas V _gas , which must be burned in the furnace to obtain the value of heat loss ΔQ associated with deviations of the technical state of the masonry (lining) from normal. Why is the value of the relative value of the heat loss ΔQ obtained in the calculation divided by the value of the heat of combustion of the fuel Q _burned. , which is indicated in the certificate of quality of natural gas supplied to the enterprise.

V _gas = ΔQ / Q _{burn. topl.} (m ³ )

Where

V _gas is the volume of natural gas necessary for the formation of ΔQ during combustion;

ΔQ - obtained from the basic formula ΔQ = 62∑ _i S _{surface. i} (t _{ext. i} -t _{calc. i} ) + 64∑ _i S _{out. surface} (kJ / hour) relative value of heat loss;

Q _{burn out. topl.} - the calorific value of natural gas supplied to the enterprise.

The main economic calculations for the turnover of natural gas are made in 1000 m ³ . To determine the cash equivalent value of 1,000 m ^{3 of} natural gas, € _{1,000 cubic meters. m} determine the value of the cost of 1000 m ^{3 of} natural gas, taking into account all costs within the enterprise.

Calculate the value of heat loss ΔQ in monetary terms € _{monetary units} according to the formula:

€ _{(monetary units)} / per 1 hour = € _{1000 cubic meters} (ΔQ / Q _{burned fuel} ) / 1000,

Where:

€ _{1000 cu m} - the cost of 1000 m ³ purchased and delivered to the furnace natural gas;

ΔQ is the relative value of heat loss calculated by the basic formula:

ΔQ = 62∑ _i S _{surface i} (t _{ext. I} -t _{calc. I} ) + 64∑ _i S _{out. surface} ) (kJ / hour),

Q _{burned fuel} - calorific value of fuel, which is indicated in the certificate of quality of natural gas.

For industrial furnaces using electric energy, using the result of the calculation of the consumed power ΔW of electricity according to the formula: ΔW = 0,017∑ _i S _{surface. i} (t _{ext. i} -t _{calculation i} ) (kW / m ² ° C per hour). The value of € _{(monetary units)} is defined as:

€ _{(monetary units)} = ΔW (kW / m ² ° С per hour) / € _{cost 1 kW / h} .

The results of calculations of the value of € _{(monetary units) are} indicated in the report.

Comparison of the value of € _{(monetary units)} with the cost of repairing the furnace is the basis for concluding the need for repairing the furnace.

After the report is compiled, measures of a statistical nature are performed, data are stored on changes in the temperature of the outer surface of the furnace over time on electronic or other media, and the timing of repair of the furnace is specified.

Technical and economic effect.

The inventive method has been used at a metallurgical enterprise in Chebarkul, Chelyabinsk region since 2007 to examine furnaces at the enterprise to determine the locations and magnitude of heat loss from the outer surface of the masonry.

Using the proposed method allows: to increase the accuracy of control over the state of thermal insulation and lining of the heating furnace without stopping its operation,

- monitor the lining condition of gas-fired heating furnaces and determine the value of the relative amount of heat loss from each furnace; the method was used to monitor the furnaces for changes in the amount of heat loss from the outer surface over time;

- timely carry out repairs of furnaces and use in full the life of the lining, the method was used to predict the deadline for the safe operation of furnaces;

- assess the effectiveness of measures to change the design of thermal insulation of arches;

- control the effectiveness of thermal insulation during operation of the furnace,

allows you to solve the following technical, organizational and economic problems:

- to conduct a survey of working furnaces without stopping production, to identify deviations in the lining and thermal insulation, including for furnaces of fibrous materials in furnaces with sheet steel sheathing;

- plan in advance lining repairs and thermal insulation of furnaces based on the actual condition of the lining;

- check the effectiveness of measures related to the improvement of thermal insulation or modernization of furnaces;

- highlight the economic value of the magnitude of heat loss associated with deviations of the lining and thermal insulation, in the form of the cost of a certain amount of energy carrier.

List of items

1 - arch of the furnace;

2 - set points for measuring the temperature;

3 - pyrometer for measuring temperature;

4 - predetermined planes on the surface of the furnace roof for measuring the temperature;

5 - thermal imager for measuring the temperature on the plane.

Claims (1)

A method for monitoring the thermal state of the lining of an industrial furnace, including determining temperature changes in the thermal state of its lining, characterized in that the temperature of the outer surface of the furnace is measured in all its sections or selectively in one of the sections without stopping the operation of the furnace using infrared spectrum measuring instruments in the form of a thermograph thermal imager or pyrometer and determine the amount of heat loss through the lining of the furnace according to the mathematical expression:
ΔQ = 62Σ _i S _poverhn.i (t -t _{naruzhn.i calc)} + 64Σ _i S _{surface. out gases i} (kJ / h),
where ΔQ is the value of heat loss from the outer surface of the furnace, kJ / h;
62 is the value of the coefficient of heat transfer by radiation and convection from the outer surface of the furnace, kJ / m ² ° C h,
∑ _i S _surface.i is the area of all sections of the outer surface of the furnace lining that do not have signs of exit of furnace gases, m ² ;
t _{external i} -t _calculation is the temperature difference t _{external i} is the temperature of the external surface of the furnace established during measurements, and t _calculation is the set or calculated temperature of the external surface from all sections of the external surface of the furnace that does not have signs of furnace gases, ° K ,
∑ _i S _{surface out gases i} - the area of all sections of the outer surface of the furnace with signs of exit of furnace gases, m ² ;
64 is the mathematical value of heat loss with exhaust gases consisting of natural gas combustion products passing through the furnace lining to the outside at a speed of 0.15 m / s and a temperature of 200-300 ° C, kJ / m ² h.

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