A method for heating up a dry coke quenching oven and a method for starting the oven

Abstract

The present invention discloses a method for heating up a dry coke quenching oven and a method for starting up the oven, and belongs to the field of coking technology. The oven heating method comprises the following steps: step S1, determination of the expansion curve of a key refractory brick sample: testing the cumulative thermal expansion rate and the average thermal expansion coefficient; step S2, determination of the daily expansion rate: controlling the heating rate with the daily expansion rate; step S3, formulation of an oven heating chart and curve, and calculation of the oven heating interval days and the daily temperature rise. Among them, the key refractory bricks are the mullite-silicon carbide bricks used in the ramp brackets and the mullite bricks used in the pre-storage chamber annular air ducts. According to the thermal expansion properties of key refractory materials, the present invention theoretically studies a oven heating method with a scientific basis to ensure the reasonable expansion of the refractory materials during the dry quenching oven, ensure the reasonable expansion of the refractory materials during the start-up of the dry quenching oven, and support the safe, long-lasting and efficient operation of the dry quenching oven.

Description

Technical Field

[0001] The present invention belongs to the technical field of coking, and more particularly relates to a temperature raising method and a start-up method for a dry quenching coke oven. Background Art

[0002] After the CDQ system is built, the refractory materials within the CDQ furnace and the coke layer at the bottom of the furnace contain a significant amount of moisture due to the short natural drying period. If this moisture is not removed properly, when the CDQ furnace is loaded with red coke, the moisture within the masonry will rapidly vaporize under the high temperatures, affecting the bond strength of the refractory mortar, resulting in poor masonry tightness and cracking of the refractory bricks. Furthermore, the water vapor reacts with the hot red coke to produce large amounts of H2 and CO, which can cause a sharp increase in the concentration of combustible components in the circulating gas, endangering the safe production of CDQ. Therefore, newly constructed CDQ units must undergo warm air drying and gas furnace baking stages to completely remove moisture from the CDQ furnace.

[0003] The current CDQ oven method is based on the Japanese CDQ oven model and lacks theoretical research. my country has over 200 CDQ units, and the first-generation CDQ system is already undergoing major or medium-term overhauls. Therefore, theoretical research on CDQ oven curves is essential.

[0004] After searching, patent CN106967448A discloses a drying method for a dry coke quenching system after a large-scale replacement of refractory materials, comprising the following steps: warm air drying, with the dry quenching furnace inlet temperature T2 as the main management temperature, raising the temperature T5 of the dry quenching furnace pre-storage section from room temperature to 100°C to 120°C; installing a dry coke quenching furnace gas burner, introducing air to assist the coke oven gas combustion and drying the furnace by adjusting the emergency relief valve of the primary dust collector, with the dry quenching furnace pre-storage section temperature T5 as the main management temperature, raising it to 500°C to 600°C; using N2 to replace the gas in the dry quenching furnace to control the content of combustible gas components within a safe range, adding red coke drying furnace into the dry quenching furnace, and finally raising the dry quenching boiler inlet temperature T6 to 800°C to 960°C, and the dry quenching furnace pre-storage section temperature T5 to 800°C to 1050°C. Patent CN102304369A discloses a dry quenching furnace start-up process for a coke dry quenching system, comprising the following steps: step 1, drying the dry quenching furnace with warm air; step 2, drying the dry quenching furnace with coal gas; step 3, after step 2, loading red coke into the dry quenching furnace to heat the refractory material to 950-1050°C at a rate of ≤30°C / h, completing the furnace baking operation; in the coal gas drying stage, by reasonably controlling the coal gas-air ratio and the heating rate, the refractory material is heated according to the temperature-increasing crystal transformation curve.

[0005] However, none of the above solutions effectively optimizes the thermal expansion of the refractory material, which causes the refractory material to crack easily when heated. Summary of the Invention

[0006] 1. Problem to be solved

[0007] Aiming at the problem that refractory bricks are prone to cracking during the heating process of the existing CDQ furnace, the present invention provides a CDQ furnace heating method and a start-up method. The heating method can ensure the reasonable expansion of the key refractory materials in the CDQ furnace.

[0008] 2. Technical solution

[0009] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0010] The CDQ oven operation typically consists of three phases: warm air drying, gas oven baking, and red coke feeding. The warm air drying phase ensures the smooth removal of moisture from the masonry. When the pre-chamber temperature reaches 120°C, the CDQ system transitions to the gas oven baking phase. During the gas oven baking phase, an appropriate heating rate is selected based on the properties of the refractory bricks to ensure a slow and even expansion of the masonry, ensuring the lifespan of the CDQ oven's refractory materials. When the pre-chamber temperature reaches 800°C, red coke feeding can begin.

[0011] Since the heating rate of the furnace during the gas furnace baking stage affects the masonry performance in the dry quenching furnace, in order to formulate a reasonable furnace heating method, the present invention improves the furnace heating method during the gas furnace baking process. The technical solution is as follows:

[0012] Step S1: Determination of expansion curve of key refractory brick samples

[0013] The cumulative thermal expansion rate (%) and average thermal expansion coefficient (10 -6 / K). The thermal expansion coefficient measured experimentally is the cumulative thermal expansion coefficient of the material, and the interval thermal expansion coefficient of each temperature interval is the difference between two adjacent cumulative thermal expansion coefficients. The expansion curve is drawn based on the thermal expansion experimental data.

[0014] Since the expansion of AM and AT bricks is closely related to the crystal transformation of alumina, the expansion of the two refractory bricks is relatively uniform, so the heating rate during furnace baking is required to be uniform.

[0015] Step S2: Selection of daily expansion rate

[0016] The CDQ furnace masonry is primarily constructed with AM (AM) mullite bricks and AT (AT) mullite silicon carbide bricks. The AT mullite silicon carbide bricks used in the corbels are particularly important. During the heating process, thermal expansion creates significant thermal stress between the AM and AT mullite silicon carbide bricks, potentially causing cracks or pulling the masonry apart, compromising its tightness. A rapid heating rate and a greater temperature difference between different parts of the masonry increase the likelihood of thermal stress. To prevent this destructive expansion, the heating rate is controlled by the daily expansion rate. Based on practical experience, the present invention sets the temperature of the annular air duct in the AM pre-chamber to 90% of the temperature of the AT ramp corbels. The daily expansion rate is 0.03% below 100°C, 0.0025% between 100-125°C, 0.03% between 125-300°C, and 0.04% between 300-1000°C.

[0017] Step S3: Preparation of oven temperature rise chart and curve

[0018] According to the formulation of the heating plan, first calculate the number of baking days for each temperature range based on the expansion curve of the bricks, the temperature ratio of each part of the dry quenching furnace and the daily expansion rate specified in step S2, then calculate the daily temperature rise of each temperature range based on the number of days, and use this to list the baking furnace heating plan.

[0019] Determine the interval thermal expansion rates of AT and AM in each temperature interval. The larger of the two values ​​is selected as the maximum interval thermal expansion rate, which serves as the basis for determining the number of days for each temperature interval. Divide the maximum interval thermal expansion rate by the daily expansion rate selected in step S2 to obtain the number of days for the interval. Calculation days less than 0.5 days are rounded to 0.5 days, and those exceeding 0.5 days are rounded to 1 day to obtain the number of days for the interval. The daily temperature rise is calculated as the temperature interval divided by the number of days for the interval.

[0020] 3. Beneficial effects

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention theoretically studies a scientifically based method for heating the furnace based on the thermal expansion properties of the refractory material used in the furnace body, thereby ensuring the reasonable expansion of the refractory material during the dry quenching furnace heating period and improving the service life of the refractory material;

[0023] (2) The CDQ furnace heating method of the present invention is applied to the CDQ furnace start-up to ensure the reasonable expansion of the refractory material during the CDQ furnace start-up, and support the safe, long-lasting and efficient operation of the CDQ furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise specified, these drawings are intended only to conceptually illustrate the structures described herein and are not necessarily drawn to scale.

[0025] Figure 1 are the expansion curves of mullite-silicon carbide bricks and mullite bricks, where AT is the expansion curve of mullite-silicon carbide bricks and AM is the expansion curve of mullite bricks;

[0026] Figure 2 This is the CDQ furnace heating curve. DETAILED DESCRIPTION

[0027] The following describes exemplary embodiments of the present invention. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the invention, it should be understood that other embodiments may be implemented and that various changes may be made to the invention without departing from the spirit and scope of the invention. The following more detailed description of the embodiments of the invention is not intended to limit the scope of the claimed invention, but is merely for illustrative purposes and does not limit the description of the features and characteristics of the invention, in order to set forth the best mode for carrying out the invention and to enable those skilled in the art to implement the invention. Therefore, the scope of the invention is limited only by the appended claims.

[0028] The CDQ oven operation typically consists of three phases: warm air drying, gas oven baking, and red coke feeding. The warm air drying phase ensures the smooth removal of moisture from the masonry. When the pre-chamber temperature reaches 125°C, the CDQ system transitions to the gas oven baking phase. During the gas oven baking phase, an appropriate heating rate is selected based on the properties of the refractory bricks to ensure a slow and even expansion of the masonry, ensuring the lifespan of the CDQ oven's refractory materials. When the pre-chamber temperature reaches 800°C, red coke feeding can begin.

[0029] The warm air drying stage primarily ensures that the rate of moisture diffusion from the new masonry is coordinated with the rate of moisture evaporation from the masonry surface. The length of the drying period depends on the moisture content of the masonry, the season of construction, the fuel used for drying, and the initial excess air coefficient. For example, a newly constructed 125t / h CDQ furnace has a total weight of approximately 1200t of refractory materials and a total moisture content of approximately 50t. In contrast, a 125t / h CDQ furnace with a replacement chute and annular air duct typically has a total weight of approximately 400t of refractory materials and a total moisture content of approximately 16t. Therefore, sufficient time and carrier gas are essential. If the drying period is too short, the joints between the refractory bricks will become weak, compromising the integrity of the entire masonry. Therefore, during the warm air drying stage, the temperature before 100°C is rapidly increased, with the temperature rising by 30-40°C per day. The temperature between 100°C and 125°C is slowly increased. The warm air drying period is generally suitable for approximately 3-4 days.

[0030] Since the heating rate of the furnace during the gas furnace baking stage affects the masonry performance in the dry quenching furnace, in order to formulate a reasonable furnace heating method, the present invention improves the furnace heating method during the gas furnace baking process, specifically comprising the following steps:

[0031] Step S1: Determination of expansion curve of key refractory brick samples

[0032] The cumulative thermal expansion rate (%) and average thermal expansion coefficient (10 -6 / K) was tested experimentally, as shown in Table 1 below. The AM sample length L0 is 49.6 mm, the starting temperature T0 is 25.1°C, and the test temperature is 1000°C. The average thermal expansion coefficient α in the temperature range of 25.1°C-1000°C is 6.6×10 -6 ·K -1 ; AT sample length L0 = 49.1mm, starting temperature T0 = 25.6℃, test temperature is 1000℃; the average thermal expansion coefficient α in the temperature range of 25.6℃-1000℃ is measured to be 5.3×10 -6 ·K -1 The thermal expansion rate measured experimentally is the cumulative thermal expansion rate of the material, and the interval thermal expansion rate of each temperature interval is the difference between two adjacent cumulative thermal expansion rates.

[0033] Table 1 Experimental data on thermal expansion of main masonry refractory materials for CDQ furnace

[0034]

[0035] According to the refractory thermal expansion test data in Table 1, the expansion curves of mullite-silicon carbide bricks and mullite bricks are drawn as follows: Figure 1As shown in the figure, the average thermal expansion coefficient of AM mullite bricks is slightly higher than that of AT mullite-silicon carbide bricks.

[0036] Since the expansion of AM and AT bricks is closely related to the crystal transformation of alumina, the expansion of the two refractory bricks is relatively uniform, so the heating rate during furnace baking is required to be uniform.

[0037] Step S2: Selection of daily expansion rate

[0038] The CDQ furnace masonry is primarily constructed with AM (AM) mullite bricks and AT (AT) mullite silicon carbide bricks. The AT mullite silicon carbide bricks used in the corbels are particularly important. During the heating process, thermal expansion creates significant thermal stress between the AM and AT mullite silicon carbide bricks, potentially causing cracks or pulling the masonry apart, compromising its tightness. A rapid heating rate and a greater temperature difference between different parts of the masonry increase the likelihood of thermal stress. To prevent this destructive expansion, the heating rate is controlled by the daily expansion rate. Based on practical experience, the present invention sets the temperature of the annular air duct in the AM pre-chamber to 90% of the temperature of the AT ramp corbels. The daily expansion rate is 0.03% below 100°C, 0.0025% between 100-125°C, 0.03% between 125-300°C, and 0.04% between 300-1000°C.

[0039] Step S3: Preparation of oven temperature rise chart and curve

[0040] According to the formulation of the heating plan, first calculate the number of baking days for each temperature range based on the expansion curve of the bricks, the temperature ratio of each part of the dry quenching furnace and the daily expansion rate specified in step S2, then calculate the daily temperature rise of each temperature range based on the number of days, and use this to list the baking furnace heating plan, as shown in Table 2.

[0041] Columns 3 and 4 in Table 2 show the interval thermal expansion rates for AT and AM in each temperature range, respectively. The larger of the two values ​​(column 5) is selected as the maximum interval thermal expansion rate, which serves as the basis for determining the number of days calculated for each temperature range. The maximum interval thermal expansion rate (column 5) is divided by the daily expansion rate selected in step S2 to obtain the number of days calculated for the interval (column 6). Calculation days less than 0.5 days are rounded to 0.5 days, and those exceeding 0.5 days are rounded to 1 day, resulting in the number of days (column 7). The daily temperature rise is calculated as the temperature range / interval days.

[0042] Table 2 Oven heating schedule

[0043]

[0044] According to Table 2, the CDQ temperature rise plan curve can be drawn, such as Figure 2 As shown, the temperature is increased according to the oven heating schedule.

[0045] The following shows the specific calculation process of the oven heating schedule:

[0046] Example 1

[0047] As shown in Table 2, when the temperature range of the ramp bracket mullite silicon carbide brick (AT) is 225-250℃, and the temperature range of the pre-storage chamber annular airway grade A mullite brick (AM) is 202.5-225℃, the interval thermal expansion rate of AT is 0.01% (column 3), and the interval thermal expansion rate of AM is 0.009% (column 4). The larger value of the two is selected and recorded as the maximum interval thermal expansion rate, which is 0.01% (column 5). The maximum interval thermal expansion rate (column 5) is used as the calculation day. / daily expansion rate, where both AT and AM are within the range of 125-300°C, and the temperature increase is planned according to a daily expansion rate of 0.03%, the calculated number of days is 0.01% / 0.03% = 0.33 days (column 6). If the interval is less than 0.5 days, it is calculated as 0.5 days (column 7). The daily temperature increase of AT is (250-225) / 0.5 = 50°C (column 11), and the daily temperature increase of AM is (225-202.5) / 0.5 = 45°C (column 12).

[0048] Example 2

[0049] As shown in Table 2, when the temperature range of the inclined channel corbel mullite silicon carbide brick (AT) is 300-350℃, and the temperature range of the pre-storage chamber annular airway grade A mullite brick (AM) is 270-315℃, the interval thermal expansion rate of AT is 0.03% (3rd column), and the interval thermal expansion rate of AM is 0.023% (4th column). The larger value of the two is selected and recorded as the maximum interval thermal expansion rate, which is 0.03% (5th column). The number of days is calculated as the maximum interval thermal expansion rate (5th column) / daily expansion rate. Among them, AT is within 300-1000℃, according to The temperature is planned to increase at a daily expansion rate of 0.04%, and the calculated number of days is 0.03% / 0.04% = 0.75 days (column 6). Intervals exceeding 0.5 days are counted as 1 day (column 7). When the AM temperature is within the range of 125-300°C, the temperature is planned to increase at a daily expansion rate of 0.03%, and the calculated number of days is 0.03% / 0.03% = 1 day (column 6). Therefore, the daily temperature increase of AT is (350-300) / 1 = 50°C (column 11), and the daily temperature increase of AM is (315-270) / 1 = 45°C (column 12).

[0050] Example 3

[0051] As shown in Table 2, when the temperature range of the ramp bracket mullite silicon carbide brick (AT) is 500-600℃, and the temperature range of the pre-storage chamber annular airway grade A mullite brick (AM) is 450-540℃, the interval thermal expansion rate of AT is 0.05% (column 3), and the interval thermal expansion rate of AM is 0.062% (column 4). The larger value of the two is selected and recorded as the maximum interval thermal expansion rate, which is 0.062% (column 5). The calculation days are the maximum interval thermal expansion rate (column 5). / daily expansion rate, where both AT and AM are within the range of 300-1000°C, and the temperature increase is planned based on a daily expansion rate of 0.04%, the calculated number of days is 0.062% / 0.04% = 1.55 days (column 6). If the interval exceeds 0.5 days, it is counted as 1 day, that is, 2 days (column 7). Therefore, the daily temperature increase of AT is (600-500) / 2 = 50°C (column 11), and the daily temperature increase of AM is (540-450) / 2 = 45°C (column 12).

Claims

1. A method for heating a gas oven in a dry coke quenching oven, characterized in that: The following steps are involved: Step S1, determination of expansion curve of key refractory brick samples: testing cumulative thermal expansion coefficient and interval thermal expansion coefficient; the interval thermal expansion coefficient of each temperature interval is the difference between two adjacent cumulative thermal expansion coefficients; the key refractory brick samples are mullite silicon carbide bricks and mullite bricks, and the average thermal expansion coefficient of the mullite brick in the temperature range of 25.1℃-1000℃ is 6.6×10 -6 ·K -1 The average thermal expansion coefficient of the mullite silicon carbide brick in the temperature range of 25.6℃-1000℃ is 5.3×10 -6 ·K -1 ; Step S2, determining the daily expansion rate: controlling the heating rate according to the daily expansion rate; the daily expansion rate is 0.03% before 100°C, 0.0025% at 100-125°C, 0.03% at 125-300°C, and 0.04% at 300-1000°C; the mullite silicon carbide bricks are located at the ramp bracket, the mullite bricks are located at the annular air duct of the pre-storage chamber, and the temperature of the annular air duct of the pre-storage chamber is 90% of the ramp bracket temperature; Step S3, formulate a baking oven temperature rise chart and curve: calculate the interval days of baking oven and the daily temperature rise; The calculation method of the interval days is as follows: within the temperature range, the larger value of the thermal expansion rate of the mullite silicon carbide brick and the mullite brick is selected as the maximum interval thermal expansion rate, and the maximum interval thermal expansion rate is divided by the daily expansion rate to obtain the calculated days of each temperature range, and the interval days are based on the calculated days; if the calculated days are less than 0.5 days, the interval days are recorded as 0.5 days, and if the calculated days are more than 0.5 days, the interval days are counted as 1 day; The daily temperature increase is the temperature increase / interval days.

2. A method for starting a dry quenching coke oven, comprising the following steps: The warm air drying stage, the gas oven stage, and the red coke feeding operation are characterized by adopting the temperature increasing method of the gas oven in the dry quenching coke oven according to claim 1.

3. The CDQ oven startup method according to claim 2, characterized in that: When the temperature of the pre-storage chamber reaches 125℃, the CDQ furnace enters the gas baking stage; when the temperature of the pre-storage chamber reaches 800℃, it enters the red coke feeding operation.

4. The CDQ oven startup method according to claim 3, characterized in that: During the warm air drying stage, the temperature before 100℃ is a rapid heating stage, and the dry quenching furnace rises 30-40℃ every day. The temperature between 100℃ and 125℃ is a slow heating stage, and the warm air drying stage lasts for 3-4 days.

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