JPH038400B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of carbonizing coal while preventing excessive carbon from adhering to the walls of a coke oven. More specifically, the present invention relates to a method for carbonizing coal while preventing excessive carbon from adhering to the walls of a coke oven. This invention relates to a method for suppressing carbon dioxide by properly mixing coal, thereby enabling normal operation of a coke oven. Generally, coke is obtained by charging raw coal into the carbonization chamber of a coke oven constructed by stacking bricks in fine grade, and heating the raw coal through the oven wall made of bricks. In the carbonization of coal as described above, the raw material coal charged into the carbonization chamber at room temperature is rapidly heated by the heat from the furnace wall, and the coal is mainly separated from the complex aromatic compounds in the coal. The organic matter is thermally decomposed and recovered as so-called coke oven gas and coal tar.
Because it is heated to a high temperature of around 30°F, decomposition products consisting of hydrocarbon compounds generated in the coking chamber come into contact with the high-temperature furnace wall while moving through the chamber, causing further thermal decomposition, resulting in fine particles. Carbon is liberated.
Most of such melted carbon is led out of the system along with the coke oven gas, but some of it adheres to the oven wall and grows as so-called carbon deposit carbon. By the way, if there is not much carbon attached to the furnace walls, there will be no major problem in the operation of the coke oven, but if it grows and increases to a certain extent, the width of the coking chamber sandwiched between the furnace walls, the so-called furnace Since the width becomes substantially smaller and the internal volume of the coking chamber decreases, the amount of raw material coal charged into the coking chamber decreases, which reduces productivity. When extruding and discharging the coke outside, the adhering carbon acts as a resistance, requiring excessive power, or in the worst case, a so-called jam occurs in which the coke cannot be pushed outside. In order to eliminate this inconvenience, conventionally, once the carbon adhesion to the furnace wall has grown to a certain extent, the coal is not charged into the carbonization chamber, but it is heated with air circulating inside the chamber. An operation called so-called carbon burn-off was being carried out. Conventionally, this carbon burning operation was carried out once per carbonization chamber for about two months, although this operation differs depending on the state of carbon adhesion. However, in recent years, as the raw material situation has worsened, additives such as pitch, asphalt, and artificial caking coal, which is a modified form of inferior coal, have been added to and mixed with inferior quality coal, which was previously thought to be unsuitable for coke production. The raw material is charged into a coke oven and carbonized, or the raw material mixed with the above-mentioned binder is pressurized to form briquette coal, and this briquette is mixed into blended pulverized coal. New technologies for coke production, such as post-carbonization, were adopted, but these binders contained more aromatic organic compounds than coal, so these were mixed in. When coking coal is carbonized, more carbon adheres to the furnace walls than before, and as a result, a new problem arises in that the coke oven cannot operate normally unless the carbon burn-off operation described above is performed more frequently. It has been raised. By the way, with regard to the above-mentioned carbon adhesion to the furnace wall, research has been conducted on the relationship between the volatile content in raw coal and it has been found that as the volatile content increases, the carbon adhesion to the furnace wall also increases. However, the value displayed as the volatile content of coal includes hydrogen, methane, ethane, propane obtained by carbonization, other hydrocarbons, carbon monoxide, carbon dioxide, tar, light oil, water, etc. It is not fully understood which component of the total amount contributes to carbon adhesion to the furnace wall, and therefore, even if the volatile content value is the same, the carbon adhesion situation may differ. Therefore, even if we use the volatile content value as an index to create a coal blend that suppresses the amount of adhesion as much as possible, we cannot obtain the expected results.
As a result, there was a problem in that it was not possible to perform control that could withstand on-site operations using only such volatile content values. Therefore, the present inventors conducted extensive research, clarified the factors that cause carbon formation in volatile matter, and found out what factors can be used as indicators to accurately predict carbon adhesion to the furnace wall.As a result, the present invention has been developed. The gist of this method is to carbonize coal while suppressing carbon adhesion to the walls of coke ovens. The effective carbon content in volatile matter is determined by subtracting the carbon content that becomes carbon monoxide and carbon dioxide during carbonization from the total carbon content, and the blended coal is calculated based on the volatile content value and effective carbon content of each single coal. The blending ratio of raw coal is determined so that the product of the volatile content value and the effective carbon content is less than a predetermined value, and blended coal is prepared at this blending ratio and charged into a coke oven.
The present invention relates to a method for carbonizing coal, which is characterized by carrying out carbonization. The present invention will be explained in more detail below. The present inventors first conducted the following tests in order to investigate what factors affect the attachment of free carbon generated when coal is carbonized to the furnace wall. Figure 1 is a schematic flowchart of the test equipment used at that time. 1 is a test furnace, with an inner diameter of approximately 150 mm,
A metal inner cylinder 2 with a height of approximately 1500 mm, an outer cylinder 3 for heating the upper part of the inner cylinder, which is equipped with an electric heating element for heating the upper half of the inner cylinder 2 to maintain a constant temperature at all times, and the above-mentioned outer cylinder 3. It consists of an outer cylinder 4 for heating the lower part of the inner cylinder, in which an electric heating element is installed to heat the lower half of the inner cylinder 2 over time. The inside of the inner cylinder 2 is partitioned into two upper and lower chambers by a metal screen 5, and the lower chamber contains a coal sample 6 for testing.
A plurality of alumina balls 7 each having a diameter of 15 mm are loaded in the upper chamber of the inner cylinder 2 so that the total weight is approximately 3.3 kg. Note that the gas generated during carbonization of the coal sample 6 is passed through a suction blower 14, which will be described later.
is drawn out from the upper part of the inner cylinder 2 by the suction force of There is an ammonia trap 11 filled with sulfuric acid, ammonia, and finally a light oil trap 12 filled with circulating refrigerant below zero.
The light oil components are recovered and stored in a gas holder 15 via a valve 13 and a suction blower 14. Coal samples of various brands and alumina balls 7 were loaded into such a test furnace 1 as described above, and the alumina balls 7 were heated to 750°C by the upper heating outer cylinder 3.
Coal sample 6 was heated to 900°C at a heating rate of 5°C/min by the lower heating cylinder.
After heating the sample coal to a temperature of 45 minutes, the alumina balls were taken out and the amount of carbon adhering to the alumina balls 7 was weighed to determine the amount of carbon attached to the sample coal. The reason why the constant-temperature alumina ball 7 was placed above the coal sample 6 as described above was to reproduce the phenomenon in which the volatile matter generated during carbonization comes into contact with the furnace wall and the carbon content therein is deposited. By measuring the amount of carbon attached to the alumina balls 7, it is possible to know the degree of deposits in the coal sample at that time. As a precaution, when the carbon adhered to the alumina balls 7 was observed using a polarizing microscope, it was confirmed that it was of the same quality as the carbon adhered to the furnace wall. The properties and test results of the sample coal (including some asphalt and pitch) used in the test are shown in Table 1.

[Table] In the above table, % is the weight ratio to the sample coal. In addition, the effective carbon content in the volatile matter is calculated by subtracting the amount of oxygen contained in the volatile content of the sample coal, which becomes carbon monoxide and carbon dioxide during the carbonization process and is derived together with the generated gas, from the volatile content value above. The reason we focused on this value is because among the volatile components derived in gaseous form during the carbonization process, those that become carbon monoxide and carbon dioxide do not contribute to carbon adhesion at all. Therefore, the value of available carbon in the volatile matter is calculated by first subtracting the coke yield value from the carbon content in the sample coal (the value obtained as a result of the subtraction is the volatile matter), then adding the ash content value. Calculating the carbon content in the coke (adding the ash content) is because the obtained coke also contains the same absolute amount of ash as in the coal, and simply subtracting the coke yield value will not reach that amount. The ash value is added to compensate for the carbon content in the sample coal), and the amount of oxygen in the volatile matter that converts to carbon monoxide and carbon dioxide is subtracted from that value. It can be obtained by Note that the description of how to derive the amount of oxygen in the volatile matter converted to carbon monoxide and carbon dioxide is omitted since it is complicated, but it may be derived by a method well known to those skilled in the art. The amount of effective carbon in the volatile matter obtained in this way is mainly converted into methane, ethane, and other hydrocarbons and is extracted in gaseous form during the carbonization of coal. It is extremely reasonable to think that it contributes greatly to adhesion. Figure 2 proves this. Figure 2 is a graph in which the vertical axis shows the ratio of carbon adhesion to the volatile content value, that is, the carbon adhesion rate (carbon adhesion amount/volatile content value), and the horizontal axis shows the value of available carbon in the volatile content. The data in Table 1 and the carbon adhesion rate calculated from the data are plotted on a graph, and it can be seen from this graph that the amount of effective carbon in the volatile matter influences carbon adhesion. Here, if the carbon adhesion amount is CD (%), the volatile content value is VM (%), and the carbon adhesion rate is R, then R=CD/VM... Furthermore, if the amount of effective carbon in the volatile matter is expressed as CU (%), as can be seen from Figure 2, there is the following relationship between R and CU. R=.alpha..CU+.beta.. This equation can be obtained by analyzing the data plotted in FIG. 2 using a statistical method. In FIG. 2, α is 0.175, β is −0.024, and the correlation coefficient r is 0.891. From the formula and formula, CD=VM・(α・CU+β)... can be obtained, and if the volatile content value of coal and the amount of effective carbon in the volatile content are known in advance, the amount of carbon adhesion can be predicted based on the formula. By the way, if we pay attention to the right side of the above equation, we can see that there are VM and VM factors that predict the amount of carbon attached.
CU product is accepted. Therefore, we newly added (VM・
Figure 3 is a graph that considers CU) as a factor (independent variable) of carbon adhesion amount (dependent variable), and the vertical axis is the carbon adhesion amount CD itself.
The horizontal axis is the product of the volatile content value and the effective carbon amount in the volatile content, that is, (VM·CU). Expressing the relationship between CD and (VM・CU) as a formula, CD=γ・(VM・CU)+δ... where γ and δ are the regression coefficient and regression constant, respectively, and they are the statistical coefficients of the data. What is obtained through processing is the same as in the case of expressions. In Figure 3, γ is 0.015, δ is -0.413, and the correlation coefficient r
is 0.982. Therefore, by comparing the scatter plots in Figures 2 and 3, it is clear that the graph shown in Figure 3 has less variation from regression and can predict the amount of carbon attached more accurately. . That is, in the present invention, the product of the volatile content value of coal and the effective carbon content in the volatile content, which is obtained by subtracting the carbon content that becomes carbon monoxide and carbon dioxide during carbonization from the total carbon content in the volatile content, is calculated as follows: , i.e. (VM・CU)
This is why we adopted this as a blending index to prevent carbon from adhering to the furnace walls. In addition, so-called binders such as improved pitch (brand name Y in Table 1) and propane deasphalt (brand name Z in Table 1) are also considered to be single coal (in Figures 2 and 3, respectively). Y, Z
The above-mentioned test was conducted, and since all of the results are on the regression line, it can be seen that these can also be treated as one brand of coal. The above tests and analysis were conducted using each of the single coal brands A to Z listed in Table 1 above, but the blended coal obtained by blending these single coals In order to find out whether additivity holds true for the above test results, the test furnace 1 actually measures the amount of carbon deposited using blended coal as a sample, while also measuring the amount of carbon deposited on plain coal based on the blending ratio. Calculate the amount of carbon adhesion by calculating the (VM・CU) value of the above blended coal by weighting the average of the (VM・CU) values of the above blended coal, and then substituting it into the formula to calculate the carbon adhesion amount and compare the measured value with the calculated value. However, since the two were found to be in good agreement, it was determined that the formula can also be used for blended coal. Next, the inventors conducted the following test using an actual furnace in order to find out whether the above test and research results could be applied to actual coke oven operation. The actual furnace used in the test was a 120-gate large coke oven with a width of 450 mm and a height of 6.5 m. First, the blending ratio of the blended coal to be charged into the coke oven was calculated on a weekly basis and used as the blending ratio for that week. Next, using this blending ratio as a weight, calculate the (VM・CU) of each single coal.
The weighted average of the values was calculated to determine the (VM・CU) value of the blended coal for that week. On the other hand, we actually prepare blended coal with the above blending ratio and operate the coke oven for that week.
The extrusion failure rate E was calculated when the coke was discharged from the furnace chamber to the outside after carbonization. This extrusion failure rate E is the percentage of the total number of coke discharged even though the power (electricity) required for extrusion exceeds a predetermined value when discharging coke outdoors in that week. The larger the value, the more carbon is attached to the oven wall, which is inconvenient for coke oven operation. This kind of test operation continued for 6 months (26 weeks),
Figure 4 is a graph of the (VM・CU) value and extrusion failure rate E of blended coal over this period. No particular relationship can be seen between them. This is probably because the coal composition has an effect on carbon adhesion to the furnace walls because there is a certain amount of time delay after the coal is charged into the coke oven. Therefore, as a result of conducting a separate statistical time series analysis, we found that the extrusion failure rate E was 4% for the (VM・CU) value.
It was found that the correlation was maximized if the response was delayed by a week. Fig. 5 is a graph in which the extrusion failure rate E corresponds to the (VM・CU) value with a delay of 4 weeks, and Fig. 6 is a scatter diagram thereof, and in Fig. 6, the correlation coefficient r is 0.897. As can be seen from these graphs, there is clearly a correlation between the (VM·CU) value of the blended coal and the extrusion failure rate E. Therefore, from this,
It can be seen that by controlling the (VM・CU) value of the blended coal by the blending ratio, it is possible to control the extrusion failure rate, that is, the amount of carbon deposited on the furnace wall. The present invention has been made based on the above test and research results, and the implementation method thereof will be explained below. In carrying out the present invention, it is first necessary to determine the upper limit of the (VM·CU) value of the blended coal. In the case of the above-mentioned actual furnace test, this value means that if the extrusion failure rate is 7% or less, the average number of extrusion failures will be 70 or less out of about 1000 coke tubes discharged per week. Since it can be judged that this number of defective coals will not cause any major problems in coke oven operation, the value of (VM・CU) of the blended coal corresponding to this defective rate is taken from Fig. 6 (VM・CU). ) value of 141.5, but this value depends on various equipment conditions and operating conditions of each coke oven (for example, if the coke oven is very old or if the oven is operated at extremely high temperatures). It varies depending on the various conditions of the coke oven) and cannot be determined uniformly, so it must be determined each time according to the local conditions of the coke oven group. Next, blended coal is prepared by blending the single coals so that the value is below the upper limit (VM・CU) determined as described above. VM, CU) values must be known by performing a predetermined analysis. The (VM・CU) value of blended coal is obtained by weighting the above-mentioned known (VM・CU) values of single coal using the blending ratio as a weight, but if the value is less than the upper limit (VM・CU) value. In order to mix the ingredients so as to achieve the following, it is necessary to perform trial and error calculations by varying the mixing ratio. By charging the blended coal obtained in this way into a coke oven and carbonizing it, excessive carbon adhesion to the oven wall can be prevented, and even fatal problems such as clogging can occur when discharging coke. It can be avoided. As described above, the present invention solves the problem of carbon adhesion on the walls of coke ovens, which could not be quantitatively understood in the past, from the volatile content of blended coal and the total carbon content in the volatile content. It can be quantified by using as an index the product of the effective carbon content after subtracting the carbon content that becomes carbon dioxide.
This makes it possible to avoid operational troubles caused by carbon adhesion to the furnace walls, and is of great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a schematic flowchart of a test device for testing carbon generation during coal carbonization. Figure 2 is a scatter diagram in which the vertical axis shows the ratio of carbon adhesion to the volatile content value, that is, the carbon adhesion rate (carbon adhesion amount/volatile content value) R, and the horizontal axis shows the effective carbon content CU in the volatile matter. . Figure 3 shows the carbon adhesion amount CD on the vertical axis.
It is a scatter diagram in which the product (VM·CU) of the volatile content value and the effective carbon content in the volatile content is plotted on the horizontal axis. Figure 4 is a graph showing the above-mentioned (VM/CU) value and extrusion failure rate E over time, and Figure 5 is a graph showing the (VM/CU) value and extrusion failure rate E in Figure 4.
CU) is a graph showing the extrusion failure rate E delayed by 4 weeks. FIG. 6 is a scatter diagram drawn with the (VM·CU) value shown in FIG. 5 on the horizontal axis and the extrusion failure rate E on the vertical axis. 1... Test furnace, 2... Inner cylinder, 3... Upper heating outer cylinder, 4... Lower heating outer cylinder, 5... Screener, 6...
... Coal sample, 7 ... Alumina ball, 8 ... Cooler, 9 ... Ammonium tar trap, 10 ... Filter, 11 ... Ammonia trap, 12 ... Light oil trap, 13 ... Valve, 14 ... ...Suction blower, 15...Gas holder.

Claims (1)

[Claims] 1 A method of carbonizing coal while suppressing carbon adhesion to the walls of coke ovens, in which carbon monoxide and dioxide are determined in advance from the volatile content value of each single coal and the total carbon content in the volatile content. Calculate the effective carbon content in the volatile matter by subtracting the carbon content that becomes carbon, and then calculate the product of the volatile content value and the effective carbon content of the blended coal based on the volatile content value and effective carbon content of each single coal. 1. A method for carbonizing coal, which comprises determining a blending ratio of raw coal so that the ratio is below a predetermined value, preparing a blended coal at this blending ratio, charging it into a coke oven, and performing carbonization.