RU2500961C1 - Method for determining characteristics of combustion in lines of baffle plates of multichamber furnace with rotating flame - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves subsequent tests of full fuel spray stop, which are conducted in series in each line of baffle plates, without using any other actions in lines of baffle plates (6), except for the action related to the test. Calculation of the change between measurements of the parameter characterising total content of incomplete burning in flue gases before and after full spray stop is carried out in the tested line of baffle plates. Identification of any line of baffle plates is performed in incomplete burning situation if the specified change exceeds x% of the value of the specified characteristic parameter at the beginning of the corresponding test; besides, x% is preferably approximately 5% to 10%.

EFFECT: improving measurement accuracy.

16 cl, 6 dwg

Description

The invention relates to the field of multi-chamber furnaces, called “rotary flame furnaces”, for firing carbon blocks, in particular carbon anodes and cathodes, intended for the electrolysis of aluminum, and, in particular, the invention relates to a method for determining combustion characteristics in partition lines such a multi-chamber furnace.

Rotary flame furnaces for burning anodes are described, in particular, in the following documents: US 4859175, WO 91/19147, US 6339729, US 6436335 and CA 2550880, which can be consulted for more information on this subject. At the same time, we can briefly recall their design and principle of operation with reference to the accompanying figures 1 and 2, where Fig. 1 is a plan view of the design of a rotary flame furnace with open chambers, while Fig. 2 shows a partial view in perspective, in cross section with a cutout of the internal structure of such a furnace.

The kiln (FAC) 1 contains two parallel shafts 1a and 1b, passing along the longitudinal axis XX along the length of the furnace 1 and each containing a series of transverse (perpendicular to the axis XX) chambers 2, separated from each other by transverse walls 3. In their the length, that is, in the transverse direction of the furnace 1, each chamber 2 is formed by the alternation of adjacent cells 4, which are open in their upper part to ensure loading of carbon blocks intended for firing and unloading of cooled fired blocks in and into which carbon blocks 5, immersed in carbon dust, and hollow heating partitions 6 with thin walls, usually held at a distance from each other by transverse struts 6a, are stacked for firing. The hollow partitions 6 of the chamber 2 are in a longitudinal extension (parallel to the largest axis XX of the furnace 1) of the hollow partitions 6 of the other chambers 2 of the same shaft 1a or 1b, and the hollow partitions 6 communicate with each other through windows 7 in the upper part of their longitudinal walls opposite the longitudinal channels made at this level in the transverse walls 3, so that the hollow partitions 6 form the longitudinal lines of the partitions located parallel to the largest axis XX of the furnace and designed to circulate gaseous media in them (combustion air, combustible gases and gaseous combustion products and fumes) that allows to provide preheating and calcining anodes 5 and then cooling them. In addition, the hollow partitions 6 further comprise bulkheads 8 for lengthening and more even distribution of the path of the gaseous products of combustion and fumes, and these hollow partitions 6 are equipped in their upper part with openings 9 closed by removable covers and made in the crown of the furnace 1.

Both furnace shafts 1a and 1b communicate with their longitudinal ends through rotation channels 10, which allow gas flows from one end of each line of the hollow partitions 6 of the shaft 1a or 1b to the end of the corresponding line of the hollow partitions 6 of the other shaft 1b or 1a, forming essentially rectangular closed contours of the lines of the hollow partitions 6.

The principle of operation of rotary-flame furnaces, also called "flame-propagating furnaces", is based on the movement of the flame front from one chamber 2 to another adjacent to it during a cycle, with each chamber passing through pre-heating, forced heating, intense combustion, then cooling (first natural, then forced).

The burning of the anodes 5 is carried out using one or more torches or groups of torches (Fig. 1 shows two groups of torches in the position in which one passes in this example through thirteen chambers 2 of mine 1a, and the other through thirteen chambers 2 of mine 1b), which cyclically move from chamber 2 to chamber 2. Each torch or group of torches consists of five consecutive zones AE, which, as shown in Fig. 1 for the torch of mine 1b, and from the exit to the entrance relative to the direction of flow of gaseous media in hollow lines partitions in the opposite direction Positive cyclic movements from camera to camera are:

A) The pre-heating zone, containing, if we consider the torch shaft 1A and take into account the direction of rotation of the flame, indicated by the arrow at the level of the rotary channel 10 at the end of the furnace at the top in figure 1:

- a suction ramp 11, equipped, for each hollow partition 6 of the chamber 2, over which this suction ramp is located, with one system for measuring and adjusting the flow of gases and combustion fumes for each line of the hollow partitions 6, and this system may contain, in each suction pipe fixedly connected to the suction ramp 11 and exiting into this ramp, on the one hand, and, on the other hand, extending into the hole 9, respectively, of one of the hollow partitions 6 of this chamber 2, an adjustable shutter rotated by a shutter drive for adjusting flow calibration, as well as a flow meter 12, located close to the entrance to the corresponding pipe On, a temperature sensor (thermocouple) 13 measuring the temperature of the flue gases upon suction, and

- a pre-heating measurement ramp 15, essentially parallel to the suction ramp 11 and located in front of the latter, usually above the same chamber 2 and equipped with temperature sensors (thermocouples) and pressure sensors to prepare a static vacuum and temperature in each of the hollow partitions 6 this chamber 2, so that it is possible to take readings and adjust this vacuum and this temperature of the preheating zone;

B) A heating zone comprising:

- several identical heating ramps 16, two or preferably three, as shown in FIG. 1; each of them is equipped with burners or nozzles for fuel injection (liquid or gaseous) and temperature sensors (thermocouples), while each of the ramps 16 is located respectively above one of the chambers from the corresponding number of adjacent chambers 2 so that the nozzles of each ramp 16 heating went into the holes 9 of the hollow partitions 6 for fuel injection into them;

C) A cooling or freezing zone comprising:

- the so-called “zero point” ramp 17, which passes above the chamber 2, located immediately in front of the chamber, located under the very front heating ramp 16, and equipped with pressure sensors for measuring pressure in each of the hollow partitions 6 of this chamber 2 so that this pressure can be adjust as described below, and

- a blowing ramp 18 equipped with electric fans equipped with a device for regulating the flow of ambient air injected into each of the hollow partitions 6 of the chamber 2 at the inlet of the chamber located under the zero ramp 17, so that the ambient air flows pumped into these hollow partitions 6 , it was possible to adjust in order to obtain the necessary pressure (with a slight overpressure or with a small vacuum) at the level of the ramp 17 of the zero point;

D) The forced cooling zone, which extends to the three chambers 2 at the inlet of the blowing ramp 18, and which in this example contains two parallel cooling ramps 19, each of which is equipped with electric fans and blowing tubes that pump ambient air into the hollow partitions 6 of the corresponding chamber; and

E) The working area located at the inlet of the cooling ramp 19 and allowing loading anodes 5 into the furnace and unloading from the furnace and servicing the chambers 2.

Thus, the heating of the furnace 1 is provided by heating ramps 16, the burner nozzles of which enter through the openings 9 into the hollow partitions 6 of the respective chambers 2. At the input of the heating ramp 16 (relative to the direction of flame advance and the direction of circulation of air and flue gases in the lines of the hollow partitions 6), the ramp 18 of the blower and the cooling ramp or ramp 19 contain pipes for pumping combustion air supplied by electric fans, these pipes being connected through openings 9 with hollow partitions 6 of the respective chambers 2. At the outlet p Amp 16 of heating is located a suction ramp 11 for removing gaseous products of combustion and fumes, collectively called the term "flue gases", which circulate in the lines of the hollow partitions 6.

The heating and burning of the anodes 5 is ensured simultaneously by burning fuel (gaseous or liquid), supplied in a controlled manner through heating ramps 16, and also, equally, by burning volatile substances (such as polycyclic aromatic hydrocarbons) emitted by the anode pitch 5 in cells 4 of chambers 2 in preheating and heating zones, and these volatile substances, which are mainly combustible and are located in cells 4, can pass into two adjacent hollow partitions 6 through channels made into the partition kah, due to the presence of residual combustion air at this level among the flue gases in these hollow partitions 6.

Thus, the circulation of air and flue gases occurs along the lines of the hollow partitions 6, and the vacuum created at the outlet of the heating zone B by the suction ramp 11 at the output end of the preheating zone A allows controlling the flow of flue gases inside the hollow partitions 6, while the air entering from cooling zones C and D using cooling ramps 19 and especially blowing ramps 18, it is preheated in hollow partitions 6, cooling burnt anodes in adjacent cells 4 on its way, and serves as an oxidizing agent reaching zones s in heating.

As the anodes 5 are fired, all the ramps 11-19 and control and measuring equipment and devices are cyclically (for example, approximately every 24 hours) moved to one chamber 2, and thus, each chamber 2 sequentially provides a loading function at the input of preheating zone A raw carbon blocks 5, then in pre-heating zone A, the function of natural pre-heating of fuel and pitch vapor by flue gases, which leave cells 4, entering hollow partitions 6, taking into account the vacuum in the hollow partitions 6 p 2 in the preheating zone A, then in the heating or firing zone B, the function of heating the blocks 5 to about 1100 ° C and, finally, in the cooling zones C and D, the function of cooling the calcined blocks 5 with ambient air and, accordingly, heating this air , which is an oxidizing agent in furnace 1, while in the opposite direction to the flame advancement and flue gas circulation, forced cooling zone D is followed by discharge zone E of cooled carbon blocks 5, and then, if necessary, the raw carbon blocks are loaded into cells 4 .

The control method of the FAC 1 furnace mainly comprises temperature and / or pressure control of the preheating zones A, heating B and blowing or free cooling C of furnace 1 in accordance with predetermined rules.

The flue gases emitted from the flares through the suction ramps 11 enter the chimney 20, for example, a cylindrical chimney, partially shown in figure 2, with a chimney 21, which may have a U-shape in plan (see dotted line in figure 1 ) or can pass around the furnace, with its outlet 22 directing the intake and collection of flue gases to a smoke treatment center (CTF), which is not shown in the figures, since it does not relate to the invention.

In order to give the anodes (carbon blocks) optimal characteristics and, therefore, to achieve a final firing temperature, currently, when controlling furnaces of this type, preference is given to supplying fuel (liquid or gaseous) heating ramps 16 regardless of the difference in pressure and air conditions in the partitions 6, which can lead to incomplete combustion in a rather significant and even large number of partition line lines 6. This, in turn, leads to an increase in the cost of operation of the furnace, not only because of excessive fuel consumption va, but also due to contamination of the suction pipes and channels, in which underburn is deposited in the form of unburned fuel residues, which creates a potential risk of ignition and disruption of the firing process.

The objective of the invention is to optimize the operation of such furnaces in continuous operation, in order to reduce the cost of their work and prevent the risks of fire and disruption of the firing process.

The problem is solved in a method for determining the characteristics of combustion in the lines of the walls of a multi-chamber furnace, called a “rotary flame furnace” for burning carbon blocks, by analyzing the value of at least one parameter that displays the total content of underburning in flue gases and residual air, coming from the partition lines and collected in the suction ramp of the furnace, the furnace contains a series of chambers of pre-heating, heating, free cooling and cooling, sequentially located along the longitudinal axis of the furnace, each chamber consisting of adjacent adjacent to each other transversely to the specified longitudinal axis and alternating cells into which the carbon blocks intended for firing are placed, and from hollow heating partitions communicating and located on one lines with partitions of other chambers parallel to the longitudinal axis of the furnace, while cooling and combustion air and flue gases circulate in the lines of the partitions, while the indicated suction ramp It is connected during preliminary heating from each of the partitions of the first chamber, respectively, to one of the suction pipes, while the necessary combustion air is partially forced by the ramp of blowing the free cooling zone, connected to at least one fan, and partially passes due to rarefaction through the lines of the partitions, the fuel necessary for firing the carbon blocks is partially injected through at least two heating ramps, each of which passes, respectively, at least in front of one of two adjacent chambers of the heating zone and each of which is configured to inject fuel into each of the partitions of the corresponding chamber of the heating zone, while controlling the combustion of the furnace mainly includes temperature and / or pressure control of the zones of preheating, heating and free cooling on each line the baffles in accordance with predetermined laws of predetermined values of temperature and / or pressure, wherein said method for determining combustion characteristics, according to the invention, comprises at least one stage of sequential tests of a complete stop of fuel injection, which are carried out sequentially in each line of partitions, with a duration sufficient to stabilize the measurement of the specified parameter characterizing the total unburning in flue gases, without using any other actions on the partition lines, except actions associated with the test of a complete stop of the injection during the duration of this test, while the determination of the combustion characteristics is based on the calculation of the change in measurements of the specified characteristic parameter, carried out before and after the complete stop of injection in each of the tested baffle lines, in order to reveal one or several baffle lines in a situation of incomplete combustion, if the specified change exceeds x% of the value of the specified characteristic parameter at the beginning of the specified test to stop the injection, while x% preferably comprise from about 5% to 10%, while the value of x depends, in particular, on the number of partitions in one chamber, on threshold values detected and the accuracy of the measurement of at least one sensor of the specified characteristic parameter.

Thus, by testing the complete stop of fuel injection in the partition line only for a period of time sufficient to stabilize the measurement of the characteristic parameter, and without changing anything on the other partition line, thanks to the method in accordance with the present invention, it is possible to identify the partition line operating in the situation incomplete combustion, on which later it will be possible to measure combustion optimization.

In order to limit the number of injection stop tests and allow the system to quickly identify a baffle or baffle in an incomplete combustion situation, the method in accordance with the present invention further comprises at least one previous step, called the step of preselecting baffle lines that may be in an incomplete combustion situation , allowing to limit the number of injection stop tests at the indicated stage of sequential tests of complete stop of injection only by pre-selected partition lines and consisting in the fact that for each line of partitions of row n, a combustion index is calculated equal to the ratio of the amount of combustion air present to the amount of fuel injected into the specified line of partitions of row n, the so-called stoichiometric limit ratio is empirically determined based on measurements of the specified parameter characterizing the content underfiring in the flue gases collected at the output of the standard partition line, reflecting the best condition of the furnace partition lines, so that iometricheskoe ratio threshold corresponds to a measured characteristic of said parameter below which the combustion is incomplete, the rate of combustion baffles lines is compared with the stoichiometric ratio and is considered incomplete combustion in each line a number of partitions n, wherein the respective combustion index lower than the stoichiometric ratio.

Thus, the identification of the partition lines in a situation of incomplete combustion using the test of complete stopping of injection is preferably preceded by the preliminary selection of the partition lines, which may be in this situation of incomplete combustion, due to the calculation, on the one hand, of the combustion index for each of all the partition walls of the furnace and, on the other hand, the specified stoichiometric ratio, determined empirically based on the measurement of the characteristic parameter in the reference line of the partitions, selected as reflecting the best condition of the partition lines, and finally, by comparing each combustion index with a stoichiometric ratio in order to establish which partition line or which partition lines can be considered a line or lines in which combustion is incomplete.

In a preferred embodiment of the inventive method for determining the combustion characteristics at the indicated stage of preliminary selection of the lines of partitions with incomplete combustion, the combustion index (RCcln) in the line of partitions of row n can be calculated as proportional to the square root of the static negative suction pressure measured in the preheating zone for the partition line in question , and inversely proportional to the sum of the values of the fuel injection power from the heating ramp nozzles operating on the same and t the same line of partitions of row n.

In particular, during this pre-selection stage, the combustion index of the line of partition walls of row n can be easily calculated using the following formula:

, $$(\mathrm{one})R{C}_{c\ln }=10\times \sqrt{\left|P_{\mathrm{one}}-{\mathrm{<figure-callout\; id="7"\; label="P"\; filenames="00000008.png"\; state="\{\{state\}\}">P</figure-callout>}}_7\right|}\times \left(\frac{N}{{\displaystyle \sum _{i=\mathrm{one}}^{N}InjHRi}}\right)$$

,

where P ₁ and P ₇ are the pressure values measured in the partitions of a number of n chambers communicating respectively with the suction ramp and with the so-called “zero point” ramp in the free cooling zone, N is the number of heating ramps, usually equal to 2 or 3, and InjHRi is the total injection power in the partition of the row of n nozzles of the heating ramp of row i, where i varies from 1 to N.

In addition, preferably, in the framework of the claimed method of characterization, the step of preselecting the lines of partitions with incomplete combustion can also include a stage in which the lines of partitions with incomplete combustion are classified in the order starting from the line where combustion is the most incomplete and to the line where combustion is the least incomplete, using the partition line designation system, according to which any partition line of row n is assigned the classification symbol NC _cln , obtained using the following formulas s:

$$(2)N{C}_{c\ln }=\mathrm{twenty}-10(\frac{R{C}_{c\ln }}{RS})$$

In addition, in order to quickly obtain pre-selection information that can be easily used, the step of classifying partition line lines can be carried out, preferably assuming that for a partition line of row n in good condition, combustion is complete if NC _cln <10, combustion is incomplete if 10 <NC _cln <12, and combustion is very incomplete and therefore critical if NC _cln > 12.

To ensure the application of this method of characterization, which is of particular interest from the point of view of the simplicity of the means for detecting and processing signals emitted by these means, the content of carbon monoxide (CO), which is measured to determine the specified stoichiometric ratio, in the suction pipe of the specified suction ramp, which is connected to the partition of the reference line of the partitions in the first chamber before itelnogo heating, wherein said threshold of this characteristic parameter, which corresponds to the stoichiometric ratio of approximately 500 ppm CO in the measurement in said suction tube, in normal operating conditions the furnace of this type corresponds to a level of 1000 ppm CO ignition point.

Thus, since in such known furnaces the carbon monoxide sensor may already be present in the collectors of the suction ramp, the method in accordance with the present invention can be applied without installing special detection and / or measurement devices, but only using the existing measurement data, which are received from the sensors measuring instruments already installed on such furnaces, and the method in accordance with the present invention is applied only with the help of a software module that can be simply and easily gently set in modern management programs such furnaces.

In addition, the method claimed in this application can be supplemented by the fact that after the steps of determining the characteristics, allowing to identify and select the lines of partitions with incomplete combustion, at least one subsequent step, called the combustion optimization step, can be applied.

Preferably, such combustion optimization consists in automatically changing the control parameters in the preheating, heating and / or free cooling zones of the furnace in order to balance the stoichiometric ratio RS combustion air / fuel in order to achieve a complete combustion situation, which can be determined by simply passing the value of the specified characteristic parameter below parameterizable threshold.

However, during this optimization step, as specified in the previous paragraph, or in any other way, the method described in this application can preferably be carried out in such a way that after this optimization step, at least one additional step of determining the combustion characteristics is activated, as it was determined above, in partition lines not selected by the method described above among partition lines presumably in a state of incomplete combustion, if the aforementioned at least one n optimization stage combustion is not possible to reach a situation of complete combustion.

Other features and advantages of the present invention will be more apparent from the following description, presented by way of non-limiting example, with reference to the accompanying drawings.

Figure 1 (already described) schematically shows the design of the furnace with two rotating torches and open chambers, a plan view;

figure 2 (already described) shows the furnace depicted in figure 1, a partial perspective view and in cross section with a break;

figure 3 is a double graph showing the change, on the one hand, of the measured CO (in parts per million) and, on the other hand, the percentage of residual oxygen in the fumes collected in the suction pipe of one line of baffles, depending on the total injection power in the line of partitions, expressed as a percentage of the established maximum power, according to three different values of the static negative suction pressure, measured at the level of the preheating measurement ramp associated with the first chamber tion heating furnace;

figure 4 shows a curve for determining the characteristics of combustion in the line of partitions of row n, showing the measured CO content (in parts per million) in one line of partitions depending on the ratio of combustion R _Ccln ;

figure 5 is a diagram showing the abscissa value of the combustion value NC _cln in the line of partitions of row n, obtained as a result of applying the classification system of combustion according to the claimed method, and on the ordinate axis, the measured CO content (in parts per million) in each line of partitions in the appropriate suction pipe;

6 shows a diagram corresponding to an example of a test of a complete stop of fuel injection sequentially in three lines of baffles α, β and γ and showing on the ordinate axis the value of the total CO content (in parts per million), measured in the suction ramp, depending on time ( expressed in minutes), and allowing to detect for the first checked line of partition walls α a decrease in the total measured CO content associated with the test, exceeding a threshold indicating the state of incomplete combustion in this line of partition walls α.

The method in accordance with the present invention relates to a cycle for determining the combustion characteristics in the line of partitions 6 of the furnace 1 by analyzing the total carbon monoxide (CO) content or any other parameter characterizing the unburned content in the fumes collected in the suction ramp 11 of the furnace 1 furnace, where this is the total content CO is measured using a CO 14 analyzer sensor in the collector of the suction ramp 11 (see FIG. 2), and the method for determining the combustion characteristics in the lines of the partitions 6 contains the first stage of evaluating the quality of combustion in one of the partition line 6 and preliminary selection of the partition line determined as an estimate of the line in the incomplete combustion state, then classification of the partition line using a notation system that allows the selection of partition line presumably with incomplete combustion and determined depending on the ratio of combustion air to fuel present in each line of the partitions 6, and from the stoichiometric ratio RS, determined empirically by measuring in the reference line of the partitions 6 reflecting the best condition of the furnace partition lines.

This first step of the method for determining the combustion characteristics allows you to pre-select the line of partitions 6, which are considered in a state of incomplete combustion, if their so-called combustion ratio RC, which is the ratio of combustion air to fuel, present in each considered line of partitions 6 is less than the above stoichiometric ratio RS.

After this stage of preliminary selection of the partition line, which is estimated to be in a state of incomplete combustion, immediately follows the step of selecting the partition line 6, considered as a line in the state of incomplete combustion, by classification in accordance with the system of designation of the quality of combustion in the partition line, which is based, as was indicated above, on the principle of the stoichiometric ratio of the air flow for combustion and fuel consumption present in each line of partitions.

Indeed, the maximum amount of fuel that can currently be injected into the partition line 6 depends on the air flow in this partition line or on the level of static depression measured in this partition line at the same moment. Below the stoichiometric ratio, combustion is incomplete, and part of the fuel present in the partition line does not burn completely, resulting in carbon monoxide (CO).

This threshold phenomenon is more clearly seen from FIG. 3, where the three solid curves show the CO content, expressed in parts per million, measured by the CO analyzer 14 in the suction pipe Na (see FIG. 2) of the partition line under consideration, depending on the amount of fuel injected , expressed as the total injection power into the indicated line of baffles under consideration and estimated as a percentage of the installed maximum power, while each of the three solid curves of the measurement of CO is constructed respectively for three different values of negative negative suction pressure in the line of baffles under consideration, corresponding to three dashed lines showing the percentage of residual oxygen in the flue gases collected in the suction pipe of the suction ramp in question 11, and these three different static vacuum values are measured using pre-heating ramp 15 at first preheating chamber 2.

Thus, curves 23, 24 and 25 of the CO content (in parts per million), measured in the indicated suction pipe Na, with a change in the total injection power from about 10% to 30% of the set maximum power with a static negative suction pressure, respectively, -140 Pa , -120 Pa and -70 Pa correspond to the dashed curves 26, 27 and 28, showing the corresponding change (continuous decrease) in the percentage of residual oxygen, as shown on the ordinate axis on the right in figure 3, respectively, at the same negative values suction pressure.

It should be noted that with a total injection power of 6 in the line of partitions 6 ranging from 10% to 15% of the set maximum power, the CO measurement curves 23, 24 and 25 in the suction pipe On this line of partitions 6 differ little from each other and show a low content СО (essentially below 500 ppm), corresponding to combustion, which is considered complete, while for values of the total injection power exceeding 15% of the set maximum power, the three curves 23, 24, and 25 of the CO measurements diverge first, gradually increasing scheysya, then at a substantially constant slope, which is greater the smaller the negative pressure suction in magnitude. In addition, with a total injection power in one line of partitions exceeding approximately 25% of the installed maximum power, three CO measurement curves 23, 24 and 25 give results in excess of 1000 ppm, which corresponds to combustion, which is all the more incomplete than lower negative suction pressure in absolute value. At the same time, curves 26, 27 and 28, showing the change in the percentage of residual oxygen, decrease essentially with a constant negative slope, not much different from one curve to another.

Based on this conclusion, for each line of partition walls 6 of row n, the combustion index RC _{cln is determined} , which expresses the ratio of the amount of fuel injected into the specified line of partition walls of row n to the amount of combustion air present in the same line of partition walls of row n. The amount of combustion air present in the line of partitions of row n corresponds to the air flow in this line of partitions of row n, which can be determined by calculating the square root of the static negative suction pressure in this line of partitions of row n, measured in the preheating zone A using ramp 15 pre-heating (see figure 1).

The amount of fuel injected into the line of partition walls of row n can be determined directly by adding the capacities of the nozzles that operate on the same line of partitions.

Thus, formula (1), which expresses the ratio or index of combustion in this line of partitions of row n, i.e., RCcln, can have the following form:

, $$(\mathrm{one})R{C}_{c\ln }=10\times \sqrt{\left|P_{\mathrm{one}}-{\mathrm{<figure-callout\; id="7"\; label="P"\; filenames="00000008.png"\; state="\{\{state\}\}">P</figure-callout>}}_7\right|}\times \left(\frac{N}{{\displaystyle \sum _{i=\mathrm{one}}^{N}InjHRi}}\right)$$

,

where P ₁ and P ₇ are the pressure values measured in the partitions of row n at the level of the chambers 2, communicating respectively with the suction ramp 11 for P1 in the preheating zone A and with the ramp of "point 0" in the free cooling zone C, and where N is the number of heating ramps 16 is usually 2 or 3, and InjHRi is the sum of the injection power of the nozzles of the heating ramp 16 for row i, where i varies from 1 to N (2 or 3), in the line of partition walls of row n. In addition, it should be noted that, as a rule, each heating ramp 16 contains two nozzles per partition 6 of one corresponding chamber 2 in such a way that if N = 3, as in the example shown in Fig. 1 (with three ramps 16 heating), then six nozzles provide fuel for the line of partition walls of row n Thus, the combustion ratio RC _cln in the line of partitions of row n is proportional to the square root of the static negative suction pressure measured in the preheating zone A for this line of partitions 6 in question and is inversely proportional to the sum of the fuel injection power of the nozzles of the heating ramps 16 operating on the same partition line 6 row n.

For this line of partition walls 6 of row n, FIG. 4 shows a shaded and curved zone 29, which corresponds to the envelope of the various measurement points of CO measured in parts per million in the corresponding suction pipe 11a, depending on the change in the corresponding combustion ratio RCcln. The threshold value RC, below which combustion is considered incomplete, that is, the value of the indicated stoichiometric ratio RS is determined empirically by observing the CO value in the line of the partitions, reflecting the best condition of the furnace partitions.

In excess of the value of 1000 ppm of undiluted CO, which approximately corresponds to the value of 500 ppm measured on the CO 14 sensor in the suction pipe Na (Fig. 2) taking into account the dilution in furnace 1, combustion is considered incomplete.

Thus, in Fig. 4, the incomplete combustion threshold is shown to be 500 ppm of the measured CO, which corresponds to a stoichiometric ratio RS of about 6 at the intersection of the hatched region 29 of the envelope of the CO measurement points and the incomplete combustion threshold of 500 ppm.

Thus, a preliminary selection is made of the lines of the partitions 6, which may be in a situation of incomplete combustion, it is also clarified that the CO content selected in this embodiment as a parameter characterizing the total content of underburning in house gases is measured to determine the stoichiometric ratio RS in that of the suction pipes On the suction ramp 11, which is connected to that of the partitions 6, which is at the intersection of the reference line of the partitions and the first pre-heating chamber 2 va, with the threshold of CO, which corresponds to the stoichiometric RS ratio is approximately 500 ppm CO, measured in the intake pipe on that under standard operating conditions of the furnace 1 of this type corresponds to a level of 1000 ppm CO ignition point.

Based on the calculation of the combustion index RCcln, it is also derived, at least for the partition lines 6, which are assigned to the lines in the incomplete combustion state when comparing their combustion index RCcln with the stoichiometric ratio RS, and preferably for all the partition lines 6 of the furnace 1, a sign allowing classify the partition lines in descending order, starting from the line with the most incomplete combustion to the line with the least incomplete combustion and even with the most complete combustion, if all the partition lines are indicated, for example, at power notation system from 0 to 20, defined thereby that the excess of the stoichiometric value 10 limit has been exceeded and is incomplete combustion in the respective line partitions.

For example, when classifying partition line preliminarily selected as incomplete combustion lines, as mentioned above, these partition lines are classified in order from the line in which combustion is most incomplete to the line in which combustion is the least incomplete, using the system designations of partition lines, according to which any partition line 6 of row n is assigned the classification symbol NCcln, obtained using the following formula (2):

$$(2)N{C}_{c\ln }=\mathrm{twenty}-10(\frac{R{C}_{c\ln }}{RS})$$

where RCcln and RS are the ratios defined above, that is, the combustion index in the partition of row n and the stoichiometric ratio.

Since the partition lines are denoted from 0 to 20 depending on their respective ratio RCcln / RS, it is believed that if the combustion sign NCcln is less than 10, combustion is complete, whereas if this combustion sign NCcln is from 10 to 12, combustion is incomplete, while combustion is very incomplete and, therefore, critical if the sign of NCcln exceeds 12.

The result of such a notation is presented as an example in FIG. 5, in which the signs of NCcln are shown as round dots on a solid curve that intersects three shaded rectangular zones, of which one zone 30 is between the signs 0 and 10 along the abscissa and between 0 and the threshold of incomplete combustion of 500 ppm of measured CO for partition lines with complete combustion, the second zone 31 is located on the abscissa between the signs 10 and 12 and the ordinate between the values of 500 and 1000 parts per million of measured CO for the line or partitions with incomplete combustion, and finally, the third zone 32 is located with signs above 12 along the abscissa axis and with a measured CO of more than 1000 ppm along the ordinate for any line of partitions with very incomplete, i.e. critical combustion.

Thus, using this designation, the partition lines are selected that are considered to be incomplete combustion with signs above 10 and each of which is then subjected to the step of identifying the partition lines with incomplete combustion using the test to stop the fuel injection for a certain time and sequentially on the selected lines partitions, starting from the line with the highest sign, and performing the test sequentially on the lines of partitions, the combustion signs of which are arranged in decreasing order.

6 schematically shows the progress of the test of a complete stop of fuel injection sequentially on three lines of partitions of a row α, β and γ, the combustion values of NC of which gradually decrease. 6, the ordinate axis shows the total CO content measured in parts per million in the collector of the suction ramp 11 using the CO sensor 14 (see FIG. 2), and the time in minutes is shown on the abscissa axis. Curve 33 shows the time variation of the total CO content measured in the collector of the suction ramp 11. At time t1, the fuel supply line through the nozzles 6 of the row a completely stops the fuel supply through the nozzles of the heating ramps 16 operating on this line of the bulkheads a by almost instantaneous shutdown, starting from the initial value (during the full stop test) of the fuel injection flow rate to zero flow rate, which corresponds to the left side with the falling arrow of the rectangle "α", symbolically representing the fuel supply command th nozzles of the line of partitions and during this test a complete stop injection. The injection is stopped during the time interval t1 t2 sufficient for the measurement of the CO content to stabilize until t2 at the end of the complete shutdown of the injection. CO 33 curve 33 shows a drop to a stabilized value, for example, 500 ppm during the interval t1 t2 so that the ΔCO value corresponding to the difference between the initial value at time t1 and the final value at time t2 of CO as a result of this termination can be measured nutrition. Then, at time t2, the fuel supply to this line of baffles is resumed at the initial value, which is shown on the right side of the rectangle “α” in Fig.6 with a rising arrow. Then passes the time interval t2 t3 with a duration slightly exceeding or essentially equal to the interval t1 t2, which is about 2 minutes, to start at the time t3 the same test of complete stop of fuel injection on the line of partition walls of the row β, knowing that during implementation the full stop test on a particular line of partitions does not make any changes to the course of the firing process in all other lines of partitions. The duration of the second test on the septum line β, corresponding to the interval t3 t4, is the same as the duration t1 t2, and the CO content curve, which, after completion of the test on the septum line a, has returned to normal, shows as a result of the test on the septum line β only a limited decrease in the CO content measured after a complete stop of fuel injection in the partition line β during the interval t3 t4. The third test stops the injection completely, conducted on the septum line γ during the interval t5 t6 of the same duration of about 2 minutes as the duration of the other tests t1 t2 and t3 t4, so each time the measurement of CO content during each test can stabilize after this shutdown of the fuel injection, and it can again stabilize after the shutdown of the fuel supply for the time interval separating two consecutive tests.

In each test, the decrease in CO content resulting from it, i.e., ΔCO, is compared with the initial value of X in percentage of CO at the beginning of this test, and, as in the case of the line of partitions α, if ΔCO exceeds X% COi, the line of partitions α is identified as a line in incomplete combustion state, which cannot be said about the lines of the partitions β and γ, if we consider the curve 33 in Fig.6.

Thus, a test of a complete stop of fuel injection is carried out, line by line, on the lines of the partitions pre-selected by their NC combustion designation. It is important that no other actions are carried out on the lines of the partitions 6, except for the test of a complete stop of injection, during the entire duration of this test, so as not to violate the characterization of combustion. Indeed, this definition of characteristics depends on calculating the change in the CO content measured between the initial moment of the test and the final moment, and it should be noted that measurements of the CO content always remain common. A sharp change in the direction of the curve 33 downward and then its rise in FIG. 6 reflect the effect of a complete stop of fuel injection in the line of the partitions and on the CO content in the collector of the suction ramp 11, where flue gases removed from all lines of the furnace partitions are taken into account.

As for the threshold X% of the value of the COi content at the beginning of each test to stop the injection completely, this value of X depends, in particular, on the number of partitions 7 for each chamber 2 of the furnace, as well as on the accuracy of the measurement and the threshold values of detection by the CO 14 sensor. As a rule X% is selected in the range of 5% to 10%. Typically, for a furnace 1 with 9 baffles 6 per chamber 2, a characterization system using the inventive method should be able to detect at least one baffle of row n from 9 baffles 6 in which combustion tends to become incomplete. If we assume that the flows circulating in each line of the partitions, that is, in each partition, are equivalent, the decrease in CO content as a result of stopping the fuel injection in the partition of row n will be at least ΔCon = 500 ppm / 9 = 56 parts per million taking into account dilution, that is, approximately X = 10% of the CO content measured in the collector of the suction ramp 11, where this content is at least 500 ppm.

Thus, choosing the partition lines that are considered to be incomplete by using the stoichiometric ratio RS, the combustion parameters of the RC partition lines, comparing the combustion indicators with the stoichiometric ratio and assigning the NC signs to the partition lines, then after identifying the partition lines with incomplete combustion using the test of a complete stop of fuel injection, you can apply the next stage, called the stage of optimization of combustion.

Such a step may consist in changing, preferably in automatically changing the control parameters, in at least one of the free cooling zones C, heating B and preheating A, so that, as far as possible, the combustion parameters are balanced according to the stoichiometric ratio of combustion air / fuel in order to return to the situation of complete combustion in the maximum possible number of lines of partitions, and this transition to the situation of complete combustion can be determined by the transition of the measured value of the content of CO or by passing the value of at least one other parameter characterizing the total content of underburning in flue gases to a value below a parameterizable threshold.

However, if the stage or stages of combustion optimization, outlined above, did not return to the situation of complete combustion for all lines of the walls of the furnace 1, then the claimed method provides at least one additional step for determining the combustion characteristics, which is carried out using the test complete stop of the injection on those of the partition lines not previously selected according to the claimed method, among the partition lines, presumably in a state of incomplete combustion, only because their combustion index RC was calculated below a stoichiometric ratio of RS. In addition, this additional step of characterization makes it possible to identify partitions with satisfactory stoichiometric conditions having an NC combustion designation below 10 in the example of the designation system described above, but whose physical conditions create combustion problems, since the partitions were deformed, pinched or more or less completely blocked. .

Claims (16)

1. A method for determining the combustion characteristics in the partition lines of a multi-chamber rotary-flame furnace for burning carbon blocks (5), including analyzing the value of at least one parameter characterizing the total content of underburning in flue gases and residual air coming from these partition walls ( 6) and collected in the suction ramp (11) of the specified furnace (1), while the specified furnace (1) contains a series of chambers (2) of preheating, heating, free cooling and force cooling, sequentially located along the longitudinal axis (XX) of the furnace (1), while each chamber (2) consists of adjacent to each other transversely to the specified longitudinal axis (XX) and alternating cells (4) into which are intended firing carbon blocks (5), and from hollow heating partitions (6) that communicate and are in line with the partitions (6) of other chambers (2) parallel to the longitudinal axis (XX) of the furnace (1), while in the lines of the partitions (6 ) provide circulation of cooling and combustion air and flue gases, wherein said suction ramp (11) is connected during preheating from each of the partitions (6) of the first chamber (2), respectively, to one of the suction pipes (11a), and the necessary combustion air is partially injected by the ramp (18) of blowing the free cooling zone (C ), connected to at least one fan, and partially passes due to rarefaction through the line of partitions (6), while the fuel necessary for burning carbon blocks (5) is partially injected through at least two ramps (16 ) heating (B), each of which is suitably dressed in front of at least one of the two adjacent chambers (2) of the heating zone and each of which is configured to inject fuel into each of the partitions (6) of the corresponding chamber (2) of the heating zone (B), while controlling the combustion of the furnace ( 1), which mainly includes temperature and / or pressure control of the preheating zones (A), heating (B) and free cooling (C) along each line of the partitions in accordance with predetermined changes in the set values of temperature and / or pressure, characterized in that it includes at least one stage of sequential tests of a complete stop of fuel injection, which are carried out sequentially in each line of partitions (6), with a duration that is sufficient to stabilize the measurement of this parameter characterizing the total content of underburning in flue gases, without using this other actions on the partition lines (6), except for the action associated with the test of a complete stop of injection during the duration of this test, while determining the characteristics of the mountains The measurements are carried out by calculating the change between the measurements of the specified characteristic parameter, carried out before and after the injection is completely stopped in each of the tested partition lines (6), to identify one or more partition lines (6) in the case of incomplete combustion, if the specified change exceeds x% of the value the specified characteristic parameter at the beginning of the specified test full stop injection, while x% is preferably from about 5% to 10%, while the value of x depends, in particular, on the number the partitions (6) in one chamber (2), from the detection thresholds and from the measurement accuracy of at least one sensor of the specified characteristic parameter. 2. The method according to claim 1, characterized in that it further includes at least one preceding stage of preliminary selection of partition lines (6), which may be in a situation of incomplete combustion, allowing to limit the number of injection stop tests at the indicated stage of sequential complete stop tests injection only preselected lines of partitions (6) and consisting in the fact that for each line of partitions (6) of a number n of the combustion rate is calculated (RC _cln), equals the ratio of the amount of air for combustion is present the stoichiometric limit ratio (RS) is empirically determined to the amount of fuel injected into the specified line of partitions (6) of row n based on measurements of the specified parameter characterizing the content of underburning in the flue gases collected at the output of the standard line of partitions (6), which reflects the best condition of the lines the partition walls (6) of the furnace, so that the stoichiometric ratio (RS) corresponds to the measured threshold of the specified characteristic parameter, below which the combustion is considered incomplete, and the combustion index (RC _cln ) of all partition lines is compared with the stoichiometric ratio (RS) and combustion is considered incomplete in any partition line (6) of row n, in which the corresponding combustion index (RC _cln ) is lower than the stoichiometric ratio (RS). 3. The method according to claim 2, characterized in that at the indicated stage of preliminary selection of the partition line (6) with incomplete combustion, the combustion index (RC _cln ) in the partition line (6) of row n is calculated as proportional to the square root of the static negative suction pressure, measured in the preheating zone (A) for the partition line (6) under consideration, and inversely proportional to the sum of the fuel injection power values of the heating ramp nozzles (16) operating on the same partition line (6) of row n. 4. The method according to claim 3, characterized in that during the specified stage of the preliminary selection, the combustion index of the line of the partitions (6) of row n is calculated by the following formula:
$$(\mathrm{one})R{C}_{c\ln }=10\cdot \sqrt{\left|P_{\mathrm{one}}-P_7\right|}\cdot \left(\frac{N}{{\displaystyle \sum _{i=\mathrm{one}}^{N}InjHRi}}\right),$$

where P ₁ and P ₇ are the pressure values measured in the partitions (6) of a number of n chambers (2) communicating respectively with the suction ramp (11) and with the “zero point” ramp (17) in the free cooling zone (C), N is the number of heating ramps (16), usually equal to 2 or 3, and InjHRi is the total injection power in the partition of a row of n nozzles of the heating ramp (16) of row i, where i varies from 1 to N. 5. The method according to any one of claims 2 to 4, characterized in that said step of pre-selecting the lines of the partitions (6) with incomplete combustion also includes the stage at which the lines of the partitions (6) with incomplete combustion are classified in the order starting from the line, in which combustion is the most incomplete, and to the line in which combustion is the least incomplete, using the partition line designation system (6), according to which any partition line (6) of row n is assigned the classification symbol NC _cln , obtained by the following formula:
$$(2)N{C}_{c\ln }=\mathrm{twenty}-10(\frac{R{C}_{c\ln }}{RS})$$

. 6. The method according to claim 5, characterized in that the step of classifying the partition line lines (6) is carried out provided that for the partition line line (6) of row n in good condition, combustion is complete if NC _cln <10, combustion is incomplete if 10 <NC _cln <12, and combustion is critically incomplete if NC _cln > 12. 7. The method according to any one of claims 1 to 4 and 6, characterized in that the carbon monoxide (CO) content, which is measured to determine the specified stoichiometric ratio in the suction pipe, is selected as a parameter characterizing the total unburn in the flue gas. 11a) of said suction ramp (11), which is connected to the baffle (6) of the reference line of baffles (6) in the first preheating chamber (2), wherein said threshold of this characteristic parameter, which corresponds to the stoichiometric ratio (RS) is approximately 500 ppm CO when measured in the indicated suction pipe (11a), which under standard operating conditions of this type of furnace corresponds to a level of 1000 ppm CO at the flash point. 8. The method according to claim 5, characterized in that the carbon monoxide (CO) content, which is measured to determine the specified stoichiometric ratio in the suction pipe (11a) of the indicated suction ramp, is selected as a parameter characterizing the total unburning in flue gases. 11), which is connected to the partition (6) of the reference line of the partitions (6) in the first preheating chamber (2), while the indicated threshold of this characteristic parameter, which corresponds to the stoichiometric ratio (RS), is approximately 500 parts per million CO when measured in the indicated suction pipe (11a), which under standard operating conditions of this type of furnace corresponds to a level of 1000 parts per million CO at the flash point. 9. The method according to claim 1, characterized in that after the stages of determining the characteristics, allowing to identify and select the line of partitions (6) with incomplete combustion, at least one subsequent combustion optimization step is used. 10. The method according to any one of claims 2 to 4, 6 and 8, characterized in that after the steps of determining the characteristics, allowing to identify and select the lines of the partitions (6) with incomplete combustion, at least one subsequent combustion optimization step is used. 11. The method according to claim 5, characterized in that after the stages of determining the characteristics, allowing to identify and select the line of the partitions (6) with incomplete combustion, at least one subsequent stage of combustion optimization is used. 12. The method according to claim 7, characterized in that after the stages of determining the characteristics, allowing to identify and select the line of partitions (6) with incomplete combustion, at least one subsequent stage of combustion optimization is used. 13. The method according to claim 9, characterized in that the combustion optimization consists in automatically changing the control parameters in the zones of preheating (A), heating (B) and / or free cooling (C) of the furnace (1) in order to balance the stoichiometric ratio ( RS) combustion air / fuel to provide a complete combustion situation, which can be determined by passing the value of the specified characteristic parameter below a parameterizable threshold. 14. The method according to claim 10, characterized in that the combustion optimization is carried out by automatically changing the control parameters in the preheating (A), heating (B) and / or free cooling (C) zones of the furnace (1) in order to balance the stoichiometric ratio ( RS) combustion air / fuel to ensure that a complete combustion situation is reached, which can be determined by simply moving the value of the specified characteristic parameter below a parameterizable threshold. 15. The method according to claim 11 or 12, characterized in that the combustion optimization is carried out by automatically changing the control parameters in the preheating (A), heating (B) and / or free cooling (C) zones of the furnace (1) in order to balance the stoichiometric ratio (RS) of combustion air / fuel to achieve a complete combustion situation, which can be determined by passing the value of the specified characteristic parameter below a parameterizable threshold. 16. The method according to claim 9 or 13, characterized in that in the event that complete combustion is not achieved after the specified optimization step, at least one additional step of determining the combustion characteristics in the partition lines (6) not previously selected among the partition lines (6) is activated presumably in a state of incomplete combustion.

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