Pottery firing process based on reverse-flame charcoal-fired dragon kiln

Abstract

This invention discloses a pottery firing process based on a downdraft wood-fired dragon kiln, including the steps of kiln construction, kiln loading, firing in the first kiln chamber, preheating of subsequent kiln chambers, firing in the second kiln chamber, preheating of subsequent kiln chambers, firing in the remaining kiln chambers, and opening the kiln. This invention employs a sequential firing method, concentrating firepower and heat on the pottery in one kiln chamber, increasing the rate of temperature rise within the kiln chamber during firing. The remaining heat is used to preheat subsequent kiln chambers, ensuring sufficient temperature and heat for each chamber, improving the consistency of pottery quality. A flame channel is used to divert flame and smoke, allowing for a more even distribution of flame and smoke within the kiln chamber, improving firing quality and yield, and enhancing the applicability of the dragon kiln. This invention has the advantages of good pottery quality consistency, rapid kiln chamber heating, high yield, and good applicability.

Description

Technical Field

[0001] This invention relates to the field of pottery firing technology, specifically to a pottery firing process based on a downdraft wood-fired dragon kiln. Background Technology

[0002] Wood-fired dragon kilns are a type of ceramic kiln in my country. They are mostly built into mountainsides, typically in a semi-subterranean style. A sloping trench is dug into the hillside, and then a long, narrow kiln is constructed, resembling a reclining dragon, hence the name "dragon kiln." Firing typically takes three to five days, requiring continuous shifts to add firewood. Subtle factors such as the speed and method of adding firewood, weather conditions, and airflow all affect the glaze and color of the pottery inside the kiln. The down-draft kiln refers to a kiln where the flames from burning firewood rise from the combustion chamber's nozzle to the top of the kiln. Because the top of the kiln is sealed, the flames cannot continue to rise and are pulled downwards by the draft of the chimney. After passing through the clay body, they enter the flue through the bottom fire intake hole and are finally discharged through the chimney. Because the density of hot gas is relatively low, it always floats on top. Therefore, people are accustomed to calling the flames moving from bottom to top "forward" and the flames moving from top to bottom "downward". This is the origin of the down-draft kiln. The ash glaze is formed by the natural falling ash from firewood onto the surface of the pottery and melting at a temperature of about 1400℃. Due to its uniqueness, pottery fired in the dragon kiln still has a place in the market that pursues individuality.

[0003] In current downdraft wood-fired dragon kilns, all unfired pottery pieces are placed inside the kiln chamber and fired simultaneously with firewood. This presents several problems: First, due to the long length of the kiln, the heat from the flames and smoke generated by the burning firewood is continuously absorbed by the unfired pottery pieces and kiln walls as it flows towards the chimney, while simultaneously dissipating to the outside. This causes the temperature of the flames and smoke to continuously decrease, resulting in poorer glaze formation and firing quality for the unfired pottery pieces closer to the chimney. This reduces the yield rate and makes it difficult to ensure consistent quality after firing. Second, the kiln typically comprises multiple chambers. To raise the temperature of the kiln chambers located at the rear of the kiln, firewood is fed into each chamber through the feeding ports on both sides of the kiln. This process is time-consuming, the kiln chambers heat up slowly, and the kiln workers' labor intensity is high. Thirdly, the uneven distribution of flames and smoke as they flow towards the chimney within the kiln chamber leads to significant temperature differences between different areas, frequently resulting in overfiring or underfiring, thus reducing the yield of fired pottery. Fourthly, dragon kilns are suitable for firing large quantities of pottery simultaneously. If only a small number of pottery pieces need to be fired, a smaller kiln is required, increasing the manufacturer's construction costs and causing the dragon kiln to be idle. Therefore, it is objectively necessary to develop a pottery firing process based on a downdraft wood-fired dragon kiln that offers good consistency in finished product quality, rapid kiln chamber heating, high yield, and broad applicability. Summary of the Invention

[0004] In order to solve the problems existing in the background art, the purpose of this invention is to provide a pottery firing process based on a downdraft wood-fired dragon kiln, which has good consistency in the quality of fired pottery, fast kiln heating speed, high yield, and good applicability.

[0005] A pottery firing process based on a downdraft wood-fired dragon kiln includes the following steps:

[0006] ① Kiln construction: Select a suitable slope to build a dragon kiln. The dragon kiln includes a kiln head, kiln body, kiln tail and chimney connected in sequence. The kiln body is divided into several kiln chambers along its length by the kiln wall. The kiln chambers are successively named the first kiln chamber, the second kiln chamber, the third kiln chamber, the fourth kiln chamber, etc., from the kiln head to the kiln tail. Each kiln chamber has a kiln door on its side wall. The bottom of the kiln wall is processed with several flame channels connecting two adjacent kiln chambers. A firewood burning area is set on the side of each kiln chamber facing the kiln head. A firewood feeding port is set on the side wall of the kiln chamber on the side of the firewood burning area.

[0007] ② Loading the kiln: Load the prepared ceramic blanks into each kiln chamber as required. After loading, seal the kiln door with refractory bricks and smooth it with yellow mud.

[0008] ③ Firing of the first kiln chamber: Firewood is put into the first kiln chamber for combustion, so that the temperature in the kiln chamber rises to 1200-1280℃ within 30 hours. During the firing process, the flames and smoke generated by the firewood combustion first flow upward, and then flow downward under the obstruction of the corresponding kiln walls and the suction of the chimney to fire the clay blanks. The temperature is maintained for 12 hours, and then the addition of firewood is stopped, thus completing the firing of the clay blanks in the first kiln chamber.

[0009] ④ Preheating of subsequent kiln chambers: The flames and smoke in the first kiln chamber are discharged into the second kiln chamber through the flame channels at the bottom of the corresponding kiln wall. The flames and smoke first flow upward, and then flow downward under the obstruction of the corresponding kiln wall and the suction of the chimney to preheat the clay body. In this way, the flames and smoke enter the third kiln chamber, the fourth kiln chamber and so on until the kiln tail. After the preheating of the remaining kiln chambers is completed, they are discharged from the chimney.

[0010] ⑤ Firing in the second kiln chamber: Firewood is added to the second kiln chamber for combustion, raising the temperature inside the kiln chamber to 1200-1280℃ within 6 hours. During the firing process, the flames and smoke generated by the burning firewood first flow upwards, and then flow downwards under the obstruction of the corresponding kiln walls and the suction of the chimney to fire the clay blanks. The temperature is maintained for 6 hours, and then the addition of firewood is stopped, completing the firing of the clay blanks in the second kiln chamber.

[0011] ⑥ Preheating of subsequent kiln chambers: The flames and smoke in the second kiln chamber are discharged into the third kiln chamber through the flame channel at the bottom of the corresponding kiln wall. The flames and smoke first flow upward, and then flow downward under the obstruction of the corresponding kiln wall and the suction of the chimney to preheat the clay blanks. In this way, the flames and smoke enter the fourth kiln chamber, the fifth kiln chamber and other subsequent kiln chambers in sequence. After completing the preheating of the remaining kiln chambers, they are discharged from the chimney.

[0012] ⑦ Firing of the remaining kiln chambers: The third, fourth, and subsequent kiln chambers are fired in sequence, so that the temperature in each kiln chamber rises to 1200-1280℃ within 6 hours. During the firing process, the flames and smoke generated by the burning firewood first flow upwards, and then flow downwards under the obstruction of the corresponding kiln walls and the suction of the chimney to fire the clay blanks. The temperature is maintained for 6 hours, and then the addition of firewood is stopped, thus completing the firing of the clay blanks in each kiln chamber. At the same time, the subsequent kiln chambers are preheated when each kiln chamber is fired.

[0013] ⑧ Opening the kiln: When the temperature in each kiln chamber drops below 70℃, remove the refractory bricks used to seal the kiln door, and then enter the kiln to take out the fired pottery.

[0014] Furthermore, in step ①, the slope of the hillside is 10 to 30°.

[0015] Furthermore, in step ①, the number of kiln chambers is 4 to 6.

[0016] Furthermore, in step ①, the projected length of the kiln body on the horizontal plane is 1520cm, the width of the kiln body is 230cm, the height is 220cm to 250cm, the angle between the kiln body and the horizontal plane is 20°, and the height of the chimney is 1000cm.

[0017] Furthermore, in step ①, there are 7 flame channels, and their width gradually increases from the middle of the kiln wall to both sides.

[0018] Furthermore, in step ①, temperature sensors are installed in each chamber of the dragon kiln.

[0019] Furthermore, in step ①, a damper is installed on the chimney.

[0020] Furthermore, in step ①, the top of each kiln chamber is an arched structure.

[0021] The beneficial effects of this invention are:

[0022] I. This invention employs a sequential firing method for pottery production. Firewood is added to only one kiln chamber at a time, concentrating the heat on the pottery within that chamber. The remaining flames and smoke then sequentially enter subsequent kiln chambers, drying and preheating the pottery there, gradually increasing its temperature. This sequential firing method ensures optimal pottery firing regardless of the kiln's length or the number of chambers. It guarantees sufficient temperature within each kiln chamber, effectively ensuring the formation of the glaze and overall firing quality, thus increasing the yield rate and maintaining consistent post-firing quality. This addresses the problem of lower temperatures in kiln chambers closer to the chimney due to the long length of traditional dragon kilns, thereby improving the overall firing quality of the pottery.

[0023] Second, this invention only requires feeding firewood into one kiln chamber at a time, and the heat generated by the combustion is relatively concentrated, which can quickly raise the temperature inside the kiln chamber. At the same time, fewer kiln workers are needed to feed firewood, which can reduce labor costs and reduce the labor intensity of kiln workers.

[0024] Third, when the flames and smoke from burning firewood enter the next kiln chamber from the previous one, they need to pass through the flame channels at the bottom of the corresponding kiln wall, so that the flames and smoke can enter the next kiln chamber more evenly, and then flow downwards more evenly to the clay blanks. This reduces the temperature field difference between different areas in the kiln chamber, solves the over-firing or under-firing phenomenon that often occurs in the traditional dragon kiln chamber, and improves the yield of pottery.

[0025] Fourth, when firing pottery, the dragon kiln described in this invention can simultaneously place pottery blanks into all kiln chambers for firing in succession when the quantity of pottery to be fired is large. Conversely, when the quantity of pottery to be fired is small, only one or a few adjacent kiln chambers can be used, and the remaining kiln chambers can be left empty, without the need to build a smaller kiln. This reduces the manufacturer's construction costs, prevents the dragon kiln from being idle, and improves the applicability of the dragon kiln.

[0026] In summary, this invention, based on a downdraft wood-fired dragon kiln, employs a sequential firing method. This concentrates heat and firepower on the pottery within a single kiln chamber, accelerating the temperature rise within that chamber. The remaining heat is used to preheat subsequent chambers, drying the clay pieces and increasing their temperature, thus improving firing efficiency. This ensures sufficient temperature and heat in each chamber, enhancing the consistency of the fired pottery's quality. The use of a flame channel to separate the flame and smoke ensures a more even distribution within the kiln, improving firing quality and yield. Finally, the dragon kiln described in this invention is suitable for both large-scale and small-scale pottery production, increasing its versatility. This invention offers advantages such as consistent pottery quality, rapid kiln temperature rise, high yield, and broad applicability. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the dragon kiln structure in this invention;

[0028] Figure 2 This is a schematic diagram of the structure of the kiln wall 5 in this invention;

[0029] In the diagram: 1-Kiln head, 2-Kiln body, 3-Kiln tail, 4-Chimney, 5-Kiln wall, 6-Kiln chamber, 7-Kiln door, 8-Flame passage, 9-Firewood burning area, 10-Firewood feeding port, 11-Sluice gate. Detailed Implementation

[0030] The present invention will be further described below with reference to embodiments, but this is not intended to limit the present invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the protection scope of the present invention. Example

[0031] The pottery firing process based on a downdraft wood-fired dragon kiln described in Example 1 includes the following steps:

[0032] ① Kiln construction: Select a suitable slope to build a dragon kiln. The dragon kiln includes a kiln head 1, a kiln body 2, a kiln tail 3 and a chimney 4 connected in sequence. The kiln body 2 is divided into several kiln chambers 6 along its length by kiln walls 5. The kiln chambers 6 along the direction from the kiln head 1 to the kiln tail 3 are successively named the first kiln chamber, the second kiln chamber, the third kiln chamber, the fourth kiln chamber, and so on. Each kiln chamber 6 has a kiln door 7 on its side wall. The bottom of the kiln wall 5 is processed with several flame channels 8 that connect two adjacent kiln chambers 6. Each kiln chamber 6 has a firewood burning area 9 on the side facing the kiln head 1. The side wall of the kiln chamber 6 on the side of the firewood burning area 9 has a firewood feeding port 10.

[0033] Preferably, the slope of the hillside is 10 to 30°. In the actual construction of the kiln in this invention, the selected hillside slope was 20°.

[0034] Preferably, the number of kiln chambers 6 is 4 to 6. The specific number of kiln chambers 6 should be determined according to parameters such as the length of the kiln body 2 and the length of the kiln chamber 6. The dragon kiln described in this invention adopts a structure with 5 kiln chambers 6.

[0035] Preferably, when the dragon kiln described in this invention is actually built, the projected length of the kiln body 2 on the horizontal plane is 1520cm, the width of the kiln body 2 is 230cm, the height is 220cm to 250cm, the angle between the kiln body 2 and the horizontal plane is 20°, and the height of the chimney 4 is 1000cm. The specific dimensions of the dragon kiln are determined according to the actual situation. The height of the chimney 4 is increased to about 3 times that of a typical dragon kiln chimney 4. This is to increase the suction force and ensure that the flames can be discharged smoothly in the event of backflow.

[0036] Specifically, there are seven flame channels 8, whose width gradually increases from the center of the kiln wall 5 towards both sides. The number of flame channels 8 can be determined according to the actual situation. Considering that in traditional dragon kiln firing of ceramics, there is a problem of high temperature in the middle and low temperature on both sides, which easily leads to over-firing or under-firing, which is not conducive to the firing of pottery, in order to solve this problem, the width of the flame channels 8 gradually increases from the center of the kiln wall 5 towards both sides. This allows some of the high-temperature flames in the middle to flow to both sides, thereby increasing the temperature on both sides of the kiln chamber 6, averaging the temperature field in the kiln chamber 6, improving the firing quality of pottery, and increasing the yield of fired pottery.

[0037] To facilitate real-time monitoring of the temperature in each kiln chamber 6, temperature sensors are installed in each kiln chamber 6 of the dragon kiln. The temperature sensors are existing temperature measuring instruments, and a display is usually installed on the outside of the dragon kiln to display the temperature measured by the temperature sensors. By setting up the temperature sensors, it is easy to control the temperature changes in the kiln chamber 6 and meet the temperature requirements during pottery firing.

[0038] A damper 11 is installed on the chimney 4. The damper 11 is existing technology and is used to adjust the flow area inside the chimney 4. According to the working principle of the dragon kiln, when the pottery is fired, the chimney 4 generates a suction force. Under the action of this suction force, outside air enters the kiln body 2 from the kiln head 1 to meet the oxygen demand of the firewood combustion. However, in the actual firing process, in order to meet the firing needs of various pottery and improve the firing quality of the pottery, it is sometimes necessary to form an oxidizing atmosphere in the kiln chamber 6, and sometimes a reducing atmosphere is needed. This can be achieved by the damper 11. When the flow area of ​​the chimney 4 is reduced by the damper 11, the amount of air entering the kiln body 2 is reduced. After the firewood is burned, a reducing atmosphere with no oxygen or very low oxygen content will be formed in the kiln body 2. Conversely, when the flow area of ​​the chimney 4 is increased by the damper 11, the amount of air entering the kiln body 2 will be increased. An oxidizing atmosphere with a higher oxygen content will be formed in the kiln body 2. The oxidizing atmosphere and the reducing atmosphere can be determined according to the actual firing needs of the pottery.

[0039] Each kiln chamber 6 has an arched top. In this invention, the flames and smoke generated after the firewood burns rise to the top of the kiln chamber 6 first, and then flow downwards due to the obstruction of the kiln wall 5. During the firing process of pottery, it was found that some smoke would stagnate in the corners or areas where it was difficult to flow at the top of the kiln chamber 6, causing uneven temperature distribution. To solve this problem, the top of the kiln chamber 6 is set in an arch shape. The arc of the arch structure has a better guiding effect, allowing the flames and smoke to flow smoothly along the arch, thereby eliminating the problem of smoke stagnation at the top of the kiln chamber 6 and improving the firing quality of the pottery. In addition, compared with the kiln top structure with corners, the arched structure of the kiln chamber 6 is less prone to stress concentration, cracking and damage under high temperature conditions, which can improve the service life of the kiln top, reduce the frequency of inspection and maintenance, and reduce the operating cost of the dragon kiln.

[0040] ② Kiln loading: The prepared clay blanks are loaded into each kiln chamber 6 as required. After loading, the kiln door 7 is sealed with refractory bricks and smoothed with yellow mud. During kiln loading, the temperature and airflow will be different in different locations. Placing the appropriate clay blanks in the appropriate locations has a significant impact on the quality of the fired pottery. In order to reduce or prevent the loss of heat in the kiln, the kiln door 7 is sealed with refractory bricks or other materials during the firing of the pottery, and smoothed with yellow mud and other materials to improve the sealing performance of the kiln door 7.

[0041] ③ Firing of the first kiln chamber: Firewood is put into the first kiln chamber for combustion, so that the temperature in the kiln chamber 6 rises to 1200℃ within 30 hours. During the firing process, the flames and smoke generated by the firewood first flow upwards, and then flow downwards under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to fire the clay blanks. The temperature is maintained for 12 hours, and then the addition of firewood is stopped, thus completing the firing of the clay blanks in the first kiln chamber.

[0042] ④ Preheating of subsequent kiln chambers: The flames and smoke in the first kiln chamber are discharged into the second kiln chamber through the flame channel 8 at the bottom of the corresponding kiln wall 5. The flames and smoke first flow upward, and then flow downward under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to preheat the clay blanks. In this way, the flames and smoke enter the third kiln chamber, the fourth kiln chamber, and so on in sequence. After completing the preheating of the remaining kiln chambers 6, they are discharged from the chimney 4.

[0043] ⑤ Firing in the second kiln chamber: Firewood is added to the second kiln chamber for combustion, causing the temperature in the kiln chamber 6 to rise to 1200℃ within 6 hours. During the firing process, the flames and smoke generated by the burning firewood first flow upwards, and then flow downwards under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to fire the clay blanks. The temperature is maintained for 6 hours, and then the addition of firewood is stopped, completing the firing of the clay blanks in the second kiln chamber.

[0044] ⑥ Preheating of subsequent kiln chambers: The flames and smoke in the second kiln chamber are discharged into the third kiln chamber through the flame channel 8 at the bottom of the corresponding kiln wall 5. The flames and smoke first flow upward, and then flow downward under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to preheat the clay blanks. In this way, the flames and smoke enter the fourth kiln chamber, the fifth kiln chamber, ... in sequence, and are discharged from the chimney after completing the preheating of the remaining kiln chambers 6.

[0045] ⑦ Firing of the remaining kiln chambers 6: The third, fourth, ... kiln chambers are fired in sequence, so that the temperature in each kiln chamber 6 rises to 1200℃ within 6 hours. During the firing process, the flames and smoke generated by the burning firewood first flow upwards, and then flow downwards under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to fire the clay blanks. The temperature is maintained for 6 hours, and the feeding of firewood is stopped to complete the firing of the clay blanks in each kiln chamber 6. At the same time, when firing in each kiln chamber 6, the subsequent kiln chambers 6 are preheated.

[0046] ⑧ Opening the kiln: When the temperature inside each kiln chamber 6 drops below 70℃, remove the refractory bricks used to seal the kiln door 7, and enter the kiln door 7 to take out the fired pottery. The opening time and temperature should be determined according to the actual situation, so as to facilitate the kiln workers to enter the kiln chamber 6.

[0047] After the construction of the down-draft wood-fired dragon kiln described in this invention, multiple ceramic firings were conducted. Practical verification has shown that the down-draft wood-fired dragon kiln based on this invention has a more scientific and rational structure, better adapting to the current needs of firing large quantities and small quantities of pottery, meeting the firing requirements of manufacturers. Simultaneously, it facilitates the uniform distribution of flames and smoke within kiln chamber 6, improving the firing quality and yield of the pottery. The sequential firing method concentrates firepower and heat on the pottery within one kiln chamber 6, increasing the rate of temperature rise within kiln chamber 6 during firing. The remaining heat is used to preheat subsequent kiln chambers 6, drying the clay blanks within them, increasing the temperature of the clay blanks and improving subsequent firing efficiency. This ensures that each kiln chamber 6 has sufficient temperature and heat during firing, improving the consistency of the fired pottery quality. Example

[0048] The pottery firing process based on a downdraft wood-fired dragon kiln described in Example 2 includes the following steps:

[0049] ① Kiln construction: Select a suitable slope to build a dragon kiln. The dragon kiln includes a kiln head 1, a kiln body 2, a kiln tail 3 and a chimney 4 connected in sequence. The kiln body 2 is divided into several kiln chambers 6 along its length by kiln walls 5. The kiln chambers 6 along the direction from the kiln head 1 to the kiln tail 3 are successively named the first kiln chamber, the second kiln chamber, the third kiln chamber, the fourth kiln chamber, and so on. Each kiln chamber 6 has a kiln door 7 on its side wall. The bottom of the kiln wall 5 is processed with several flame channels 8 that connect two adjacent kiln chambers 6. Each kiln chamber 6 has a firewood burning area 9 on the side facing the kiln head 1. The side wall of the kiln chamber 6 on the side of the firewood burning area 9 has a firewood feeding port 10.

[0050] Preferably, the slope of the hillside is 10 to 30°. In the actual construction of the kiln in this invention, the selected hillside slope was 20°.

[0051] Preferably, the number of kiln chambers 6 is 4 to 6. The specific number of kiln chambers 6 should be determined according to parameters such as the length of the kiln body 2 and the length of the kiln chamber 6. The dragon kiln described in this invention adopts a structure with 5 kiln chambers 6.

[0052] Preferably, when the dragon kiln described in this invention is actually built, the projected length of the kiln body 2 on the horizontal plane is 1520cm, the width of the kiln body 2 is 230cm, the height is 220cm to 250cm, the angle between the kiln body 2 and the horizontal plane is 20°, and the height of the chimney 4 is 1000cm. The specific dimensions of the dragon kiln are determined according to the actual situation. The height of the chimney 4 is increased to about 3 times that of a typical dragon kiln chimney 4. This is to increase the suction force and ensure that the flames can be discharged smoothly in the event of backflow.

[0053] Specifically, there are seven flame channels 8, whose width gradually increases from the center of the kiln wall 5 towards both sides. The number of flame channels 8 can be determined according to the actual situation. Considering that in traditional dragon kiln firing of ceramics, there is a problem of high temperature in the middle and low temperature on both sides, which easily leads to over-firing or under-firing, which is not conducive to the firing of pottery, in order to solve this problem, the width of the flame channels 8 gradually increases from the center of the kiln wall 5 towards both sides. This allows some of the high-temperature flames in the middle to flow to both sides, thereby increasing the temperature on both sides of the kiln chamber 6, averaging the temperature field in the kiln chamber 6, improving the firing quality of pottery, and increasing the yield of fired pottery.

[0054] To facilitate real-time monitoring of the temperature in each kiln chamber 6, temperature sensors are installed in each kiln chamber 6 of the dragon kiln. The temperature sensors are existing temperature measuring instruments, and a display is usually installed on the outside of the dragon kiln to display the temperature measured by the temperature sensors. By setting up the temperature sensors, it is easy to control the temperature changes in the kiln chamber 6 and meet the temperature requirements during pottery firing.

[0055] A damper 11 is installed on the chimney 4. The damper 11 is existing technology and is used to adjust the flow area inside the chimney 4. According to the working principle of the dragon kiln, when the pottery is fired, the chimney 4 generates a suction force. Under the action of this suction force, outside air enters the kiln body 2 from the kiln head 1 to meet the oxygen demand of the firewood combustion. However, in the actual firing process, in order to meet the firing needs of various pottery and improve the firing quality of the pottery, it is sometimes necessary to form an oxidizing atmosphere in the kiln chamber 6, and sometimes a reducing atmosphere is needed. This can be achieved by the damper 11. When the flow area of ​​the chimney 4 is reduced by the damper 11, the amount of air entering the kiln body 2 is reduced. After the firewood is burned, a reducing atmosphere with no oxygen or very low oxygen content will be formed in the kiln body 2. Conversely, when the flow area of ​​the chimney 4 is increased by the damper 11, the amount of air entering the kiln body 2 will be increased. An oxidizing atmosphere with a higher oxygen content will be formed in the kiln body 2. The oxidizing atmosphere and the reducing atmosphere can be determined according to the actual firing needs of the pottery.

[0056] Each kiln chamber 6 has an arched top. In this invention, the flames and smoke generated after the firewood burns rise to the top of the kiln chamber 6 first, and then flow downwards due to the obstruction of the kiln wall 5. During the firing process of pottery, it was found that some smoke would stagnate in the corners or areas where it was difficult to flow at the top of the kiln chamber 6, causing uneven temperature distribution. To solve this problem, the top of the kiln chamber 6 is set in an arch shape. The arc of the arch structure has a better guiding effect, allowing the flames and smoke to flow smoothly along the arch, thereby eliminating the problem of smoke stagnation at the top of the kiln chamber 6 and improving the firing quality of the pottery. In addition, compared with the kiln top structure with corners, the arched structure of the kiln chamber 6 is less prone to stress concentration, cracking and damage under high temperature conditions, which can improve the service life of the kiln top, reduce the frequency of inspection and maintenance, and reduce the operating cost of the dragon kiln.

[0057] ② Kiln loading: The prepared clay blanks are loaded into each kiln chamber 6 as required. After loading, the kiln door 7 is sealed with refractory bricks and smoothed with yellow mud. During kiln loading, the temperature and airflow will be different in different locations. Placing the appropriate clay blanks in the appropriate locations has a significant impact on the quality of the fired pottery. In order to reduce or prevent the loss of heat in the kiln, the kiln door 7 is sealed with refractory bricks or other materials during the firing of the pottery, and smoothed with yellow mud and other materials to improve the sealing performance of the kiln door 7.

[0058] ③ Firing of the first kiln chamber: Firewood is put into the first kiln chamber for combustion, so that the temperature in the kiln chamber 6 rises to 1240℃ within 30 hours. During the firing process, the flames and smoke generated by the firewood first flow upward, and then flow downward under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to fire the clay blanks. The temperature is maintained for 12 hours, and then the addition of firewood is stopped, thus completing the firing of the clay blanks in the first kiln chamber.

[0059] ④ Preheating of subsequent kiln chambers: The flames and smoke in the first kiln chamber are discharged into the second kiln chamber through the flame channel 8 at the bottom of the corresponding kiln wall 5. The flames and smoke first flow upward, and then flow downward under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to preheat the clay blanks. In this way, the flames and smoke enter the third kiln chamber, the fourth kiln chamber, and so on in sequence. After completing the preheating of the remaining kiln chambers 6, they are discharged from the chimney 4.

[0060] ⑤ Firing in the second kiln chamber: Firewood is added to the second kiln chamber for combustion, causing the temperature in the kiln chamber 6 to rise to 1240℃ within 6 hours. During the firing process, the flames and smoke generated by the burning firewood first flow upwards, and then flow downwards under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to fire the clay blanks. The temperature is maintained for 6 hours, and then the addition of firewood is stopped, completing the firing of the clay blanks in the second kiln chamber.

[0061] ⑥ Preheating of subsequent kiln chambers: The flames and smoke in the second kiln chamber are discharged into the third kiln chamber through the flame channel 8 at the bottom of the corresponding kiln wall 5. The flames and smoke first flow upward, and then flow downward under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to preheat the clay blanks. In this way, the flames and smoke enter the fourth kiln chamber, the fifth kiln chamber, ... in sequence, and are discharged from the chimney after completing the preheating of the remaining kiln chambers 6.

[0062] ⑦ Firing of the remaining kiln chambers 6: The third, fourth, ... kiln chambers are fired in sequence, so that the temperature in each kiln chamber 6 rises to 1240℃ within 6 hours. During the firing process, the flames and smoke generated by the burning firewood first flow upwards, and then flow downwards under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to fire the clay blanks. The temperature is maintained for 6 hours, and the feeding of firewood is stopped to complete the firing of the clay blanks in each kiln chamber 6. At the same time, when firing in each kiln chamber 6, the subsequent kiln chambers 6 are preheated.

[0063] ⑧ Opening the kiln: When the temperature inside each kiln chamber 6 drops below 70℃, remove the refractory bricks used to seal the kiln door 7, and enter the kiln door 7 to take out the fired pottery. The opening time and temperature should be determined according to the actual situation, so as to facilitate the kiln workers to enter the kiln chamber 6.

[0064] After the construction of the down-draft wood-fired dragon kiln described in this invention, multiple ceramic firings were conducted. Practical verification has shown that the down-draft wood-fired dragon kiln based on this invention has a more scientific and rational structure, better adapting to the current needs of firing large quantities and small quantities of pottery, meeting the firing requirements of manufacturers. Simultaneously, it facilitates the uniform distribution of flames and smoke within kiln chamber 6, improving the firing quality and yield of the pottery. The sequential firing method concentrates firepower and heat on the pottery within one kiln chamber 6, increasing the rate of temperature rise within kiln chamber 6 during firing. The remaining heat is used to preheat subsequent kiln chambers 6, drying the clay blanks within them, increasing the temperature of the clay blanks and improving subsequent firing efficiency. This ensures that each kiln chamber 6 has sufficient temperature and heat during firing, improving the consistency of the fired pottery quality. Example

[0065] The pottery firing process based on a downdraft wood-fired dragon kiln described in Example 3 includes the following steps:

[0066] ① Kiln construction: Select a suitable slope to build a dragon kiln. The dragon kiln includes a kiln head 1, a kiln body 2, a kiln tail 3 and a chimney 4 connected in sequence. The kiln body 2 is divided into several kiln chambers 6 along its length by kiln walls 5. The kiln chambers 6 along the direction from the kiln head 1 to the kiln tail 3 are successively named the first kiln chamber, the second kiln chamber, the third kiln chamber, the fourth kiln chamber, and so on. Each kiln chamber 6 has a kiln door 7 on its side wall. The bottom of the kiln wall 5 is processed with several flame channels 8 that connect two adjacent kiln chambers 6. Each kiln chamber 6 has a firewood burning area 9 on the side facing the kiln head 1. The side wall of the kiln chamber 6 on the side of the firewood burning area 9 has a firewood feeding port 10.

[0067] Preferably, the slope of the hillside is 10 to 30°. In the actual construction of the kiln in this invention, the selected hillside slope was 20°.

[0068] Preferably, the number of kiln chambers 6 is 4 to 6. The specific number of kiln chambers 6 should be determined according to parameters such as the length of the kiln body 2 and the length of the kiln chamber 6. The dragon kiln described in this invention adopts a structure with 5 kiln chambers 6.

[0069] Preferably, when the dragon kiln described in this invention is actually built, the projected length of the kiln body 2 on the horizontal plane is 1520cm, the width of the kiln body 2 is 230cm, the height is 220cm to 250cm, the angle between the kiln body 2 and the horizontal plane is 20°, and the height of the chimney 4 is 1000cm. The specific dimensions of the dragon kiln are determined according to the actual situation. The height of the chimney 4 is increased to about 3 times that of a typical dragon kiln chimney 4. This is to increase the suction force and ensure that the flames can be discharged smoothly in the event of backflow.

[0070] Specifically, there are seven flame channels 8, whose width gradually increases from the center of the kiln wall 5 towards both sides. The number of flame channels 8 can be determined according to the actual situation. Considering that in traditional dragon kiln firing of ceramics, there is a problem of high temperature in the middle and low temperature on both sides, which easily leads to over-firing or under-firing, which is not conducive to the firing of pottery, in order to solve this problem, the width of the flame channels 8 gradually increases from the center of the kiln wall 5 towards both sides. This allows some of the high-temperature flames in the middle to flow to both sides, thereby increasing the temperature on both sides of the kiln chamber 6, averaging the temperature field in the kiln chamber 6, improving the firing quality of pottery, and increasing the yield of fired pottery.

[0071] To facilitate real-time monitoring of the temperature in each kiln chamber 6, temperature sensors are installed in each kiln chamber 6 of the dragon kiln. The temperature sensors are existing temperature measuring instruments, and a display is usually installed on the outside of the dragon kiln to display the temperature measured by the temperature sensors. By setting up the temperature sensors, it is easy to control the temperature changes in the kiln chamber 6 and meet the temperature requirements during pottery firing.

[0072] A damper 11 is installed on the chimney 4. The damper 11 is existing technology and is used to adjust the flow area inside the chimney 4. According to the working principle of the dragon kiln, when the pottery is fired, the chimney 4 generates a suction force. Under the action of this suction force, outside air enters the kiln body 2 from the kiln head 1 to meet the oxygen demand of the firewood combustion. However, in the actual firing process, in order to meet the firing needs of various pottery and improve the firing quality of the pottery, it is sometimes necessary to form an oxidizing atmosphere in the kiln chamber 6, and sometimes a reducing atmosphere is needed. This can be achieved by the damper 11. When the flow area of ​​the chimney 4 is reduced by the damper 11, the amount of air entering the kiln body 2 is reduced. After the firewood is burned, a reducing atmosphere with no oxygen or very low oxygen content will be formed in the kiln body 2. Conversely, when the flow area of ​​the chimney 4 is increased by the damper 11, the amount of air entering the kiln body 2 will be increased. An oxidizing atmosphere with a higher oxygen content will be formed in the kiln body 2. The oxidizing atmosphere and the reducing atmosphere can be determined according to the actual firing needs of the pottery.

[0073] Each kiln chamber 6 has an arched top. In this invention, the flames and smoke generated after the firewood burns rise to the top of the kiln chamber 6 first, and then flow downwards due to the obstruction of the kiln wall 5. During the firing process of pottery, it was found that some smoke would stagnate in the corners or areas where it was difficult to flow at the top of the kiln chamber 6, causing uneven temperature distribution. To solve this problem, the top of the kiln chamber 6 is set in an arch shape. The arc of the arch structure has a better guiding effect, allowing the flames and smoke to flow smoothly along the arch, thereby eliminating the problem of smoke stagnation at the top of the kiln chamber 6 and improving the firing quality of the pottery. In addition, compared with the kiln top structure with corners, the arched structure of the kiln chamber 6 is less prone to stress concentration, cracking and damage under high temperature conditions, which can improve the service life of the kiln top, reduce the frequency of inspection and maintenance, and reduce the operating cost of the dragon kiln.

[0074] ② Kiln loading: The prepared clay blanks are loaded into each kiln chamber 6 as required. After loading, the kiln door 7 is sealed with refractory bricks and smoothed with yellow mud. During kiln loading, the temperature and airflow will be different in different locations. Placing the appropriate clay blanks in the appropriate locations has a significant impact on the quality of the fired pottery. In order to reduce or prevent the loss of heat in the kiln, the kiln door 7 is sealed with refractory bricks or other materials during the firing of the pottery, and smoothed with yellow mud and other materials to improve the sealing performance of the kiln door 7.

[0075] ③ Firing of the first kiln chamber: Firewood is put into the first kiln chamber for combustion, so that the temperature in the kiln chamber 6 rises to 1280℃ within 30 hours. During the firing process, the flames and smoke generated by the firewood first flow upwards, and then flow downwards under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to fire the clay blanks. The temperature is maintained for 12 hours, and then the addition of firewood is stopped, thus completing the firing of the clay blanks in the first kiln chamber.

[0076] ④ Preheating of subsequent kiln chambers: The flames and smoke in the first kiln chamber are discharged into the second kiln chamber through the flame channel 8 at the bottom of the corresponding kiln wall 5. The flames and smoke first flow upward, and then flow downward under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to preheat the clay blanks. In this way, the flames and smoke enter the third kiln chamber, the fourth kiln chamber, and so on in sequence. After completing the preheating of the remaining kiln chambers 6, they are discharged from the chimney 4.

[0077] ⑤ Firing in the second kiln chamber: Firewood is added to the second kiln chamber for combustion, causing the temperature in the kiln chamber 6 to rise to 1280℃ within 6 hours. During the firing process, the flames and smoke generated by the burning firewood first flow upwards, and then flow downwards under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to fire the clay blanks. The temperature is maintained for 6 hours, and then the addition of firewood is stopped, completing the firing of the clay blanks in the second kiln chamber.

[0078] ⑥ Preheating of subsequent kiln chambers: The flames and smoke in the second kiln chamber are discharged into the third kiln chamber through the flame channel 8 at the bottom of the corresponding kiln wall 5. The flames and smoke first flow upward, and then flow downward under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to preheat the clay blanks. In this way, the flames and smoke enter the fourth kiln chamber, the fifth kiln chamber, ... in sequence, and are discharged from the chimney after completing the preheating of the remaining kiln chambers 6.

[0079] ⑦ Firing of the remaining kiln chambers 6: The third, fourth, ... kiln chambers are fired in sequence, so that the temperature in each kiln chamber 6 rises to 1280℃ within 6 hours. During the firing process, the flames and smoke generated by the burning firewood first flow upwards, and then flow downwards under the obstruction of the corresponding kiln wall 5 and the suction of the chimney to fire the clay blanks. The temperature is maintained for 6 hours, and the feeding of firewood is stopped to complete the firing of the clay blanks in each kiln chamber 6. At the same time, when firing in each kiln chamber 6, the subsequent kiln chambers 6 are preheated.

[0080] ⑧ Opening the kiln: When the temperature inside each kiln chamber 6 drops below 70℃, remove the refractory bricks used to seal the kiln door 7, and enter the kiln door 7 to take out the fired pottery. The opening time and temperature should be determined according to the actual situation, so as to facilitate the kiln workers to enter the kiln chamber 6.

[0081] After the construction of the down-draft wood-fired dragon kiln described in this invention, multiple ceramic firings were conducted. Practical verification has shown that the down-draft wood-fired dragon kiln based on this invention has a more scientific and rational structure, better adapting to the current needs of firing large quantities and small quantities of pottery, meeting the firing requirements of manufacturers. Simultaneously, it facilitates the uniform distribution of flames and smoke within kiln chamber 6, improving the firing quality and yield of the pottery. The sequential firing method concentrates firepower and heat on the pottery within one kiln chamber 6, increasing the rate of temperature rise within kiln chamber 6 during firing. The remaining heat is used to preheat subsequent kiln chambers 6, drying the clay blanks within them, increasing the temperature of the clay blanks and improving subsequent firing efficiency. This ensures that each kiln chamber 6 has sufficient temperature and heat during firing, improving the consistency of the fired pottery quality.

[0082] Using the methods described in Examples 1-3 above for pottery firing, practical statistics show that the yield rate of pottery can be increased by about 10% to 20% on the existing basis, reaching more than 50%. By improving the qualified rate and yield rate of pottery, the firing quality of pottery can be improved, and the economic benefits of manufacturers can also be increased. It has the advantages of good consistency of fired pottery quality, fast kiln heating speed, high yield, and good applicability, making it easy to promote and use.

Claims

1. A pottery firing process based on a downdraft wood-fired dragon kiln, characterized in that, Includes the following steps: ① Kiln construction: Select a suitable slope to build a dragon kiln. The dragon kiln includes a kiln head (1), kiln body (2), kiln tail (3) and chimney (4) connected in sequence. The kiln body (2) is divided into several kiln chambers (6) along its length by kiln walls (5). The kiln chambers (6) along the direction from kiln head (1) to kiln tail (3) are arranged in the order of first kiln chamber, second kiln chamber, third kiln chamber and fourth kiln chamber. Each kiln chamber (6) has a kiln door (7) on its side wall. The bottom of the kiln wall (5) is processed with several flame channels (8) connecting two adjacent kiln chambers (6). Each kiln chamber (6) has a firewood burning area (9) on the side facing the kiln head (1). The side wall of the kiln chamber (6) on the side of the firewood burning area (9) has a firewood feeding port (10). ② Loading the kiln: Load the prepared ceramic blanks into each kiln chamber (6) as required. After loading the kiln, seal the kiln door (7) with refractory bricks and smooth it with yellow mud. ③ Firing of the first kiln chamber: Firewood is put into the first kiln chamber for burning, so that the temperature in the kiln chamber (6) rises to 1200-1280℃ within 30 hours. During the firing process, the flames and smoke generated by the firewood first flow upward, and then flow downward under the obstruction of the corresponding kiln wall (5) and the suction of the chimney to fire the pottery blanks. The temperature is maintained for 12 hours, and the addition of firewood is stopped to complete the firing of the pottery blanks in the first kiln chamber. ④ Preheating of subsequent kiln chambers: The flames and flue gas in the first kiln chamber are discharged into the second kiln chamber through the flame channel (8) at the bottom of the corresponding kiln wall (5). The flames and flue gas first flow upward, and then flow downward under the obstruction of the corresponding kiln wall (5) and the suction of the chimney to preheat the clay body. In this way, the flames and flue gas enter the subsequent kiln chambers in sequence until the kiln tail (3). After the preheating of the remaining kiln chambers (6) is completed, the flames and flue gas are discharged from the chimney (4). ⑤ Firing in the second kiln chamber: Firewood is added to the second kiln chamber for combustion, so that the temperature in the kiln chamber (6) rises to 1200-1280℃ within 6 hours. During the firing process, the flames and smoke generated by the firewood combustion first flow upward, and then flow downward under the obstruction of the corresponding kiln wall (5) and the suction of the chimney to fire the pottery blanks. The temperature is maintained for 6 hours, and the addition of firewood is stopped to complete the firing of the pottery blanks in the second kiln chamber. ⑥ Preheating of subsequent kiln chambers: The flames and flue gas in the second kiln chamber are discharged into the third kiln chamber through the flame channel (8) at the bottom of the corresponding kiln wall (5). The flames and flue gas first flow upward, and then flow downward under the obstruction of the corresponding kiln wall (5) and the suction of the chimney to preheat the clay body. In this way, the flames and flue gas enter the subsequent kiln chambers in sequence, and after completing the preheating of the remaining kiln chambers (6), they are discharged from the chimney. ⑦ Firing of the remaining kiln chambers (6): The kilns are fired in sequence, with firewood added for combustion, so that the temperature in each kiln chamber (6) rises to 1200-1280℃ within 6 hours. During the firing process, the flames and smoke generated by the firewood combustion first flow upward, and then flow downward under the obstruction of the corresponding kiln wall (5) and the suction of the chimney to fire the clay blanks. The temperature is maintained for 6 hours, and the addition of firewood is stopped to complete the firing of the clay blanks in each kiln chamber (6). At the same time, when firing in each kiln chamber (6), the subsequent kiln chambers (6) are preheated. ⑧ Opening the kiln: When the temperature inside each kiln chamber (6) drops below 70°C, remove the refractory bricks used to seal the kiln door (7), and enter the kiln door (7) to take out the pottery after firing.

2. The pottery firing process based on a downdraft wood-fired dragon kiln according to claim 1, characterized in that: In step ①, the slope of the hillside is 10 to 30°.

3. The pottery firing process based on a downdraft wood-fired dragon kiln according to claim 1, characterized in that: In step ①, the number of kiln chambers (6) is 4 to 6.

4. The pottery firing process based on a downdraft wood-fired dragon kiln according to claim 1, characterized in that: In step ①, the projected length of the kiln body (2) on the horizontal plane is 1520cm, the width of the kiln body (2) is 230cm, the height is 220cm to 250cm, the angle between the kiln body (2) and the horizontal plane is 20°, and the height of the chimney (4) is 1000cm.

5. The pottery firing process based on a downdraft wood-fired dragon kiln according to claim 1, characterized in that: In step ①, there are 7 flame channels (8), and their width gradually increases from the middle of the kiln wall (5) to both sides.

6. The pottery firing process based on a downdraft wood-fired dragon kiln according to claim 1, characterized in that: In step ①, each kiln chamber (6) of the dragon kiln is equipped with a temperature sensor.

7. The pottery firing process based on a downdraft wood-fired dragon kiln according to claim 1, characterized in that: In step ①, a gate (11) is installed on the chimney (4).

8. The pottery firing process based on a downdraft wood-fired dragon kiln according to claim 1, characterized in that: In step ①, the top of each kiln chamber (6) is an arched structure.

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