Development of the hottest 1800 energy-saving oil

Development of 1800 ℃ energy-saving oil fired high-temperature drawer kiln

Abstract: 1800 ℃ high-temperature drawer kiln is an advanced kiln type for calcining ceramic products. At present, it is still in the development and exploration stage in China. We have completed the construction of the kiln in Shenyang Ceramic Research Institute on the basis of investigation, investigation, demonstration, design and other work at home and abroad. For this reason, all indicators meet the design requirements. Because the kiln adopts advanced kiln structure and the kiln body of light and low heat storage refractory materials; Fuel system with high-speed nozzle; The heating and heat exchange device of combustion air using the waste heat of flue and the unique cooling mode of kiln car, kiln body and flue seal have reduced the energy consumption index by 80%, increased the output index by 50% and significantly improved the quality compared with the ceiling guided flame kiln currently used. The restriction of this kind of kiln on the development of products has been fundamentally reversed

key words: energy saving high-temperature drawer kiln

1 Introduction

the development idea of 1800 ℃ high-temperature drawer kiln in China came into being in the late 1980s, when it was designed to replace the industrial porcelain ceiling flame guide kiln with high energy consumption, low output and poor quality. The main purpose of the development is:

1.1 by using advanced high-temperature lightweight refractory as the kiln lining, we can solve the problems of too thick wall, too large heat storage capacity and too high energy consumption of the ceiling flame guide kiln. The thickness of the traditional kiln wall is up to one meter, and the heat storage capacity of the kiln wall is up to 40%; The thickness of drawer kiln wall is only 0.4m, and the heat storage of kiln wall is less than 20%

1.2 by improving the loading and unloading of products inside the kiln to the loading and unloading of products outside the kiln, the burned products in the kiln can be pushed into the kiln immediately after they leave the kiln with the kiln car at about 200 ℃, so that the heat energy in the kiln can be maximized, so as to solve the problems of too long loading and unloading cycle of the kiln, serious waste of heat energy, and excessive labor intensity of operators. This can reduce the heat loss by 5%

1.3 by adopting advanced high-speed nozzles to solve the problems of uneven temperature in the kiln, poor fuel atomization, excessive energy consumption and poor product quality, this can improve product quality by 5 ~ 10 percentage points and save fuel consumption by more than 5%

1.4 increase the combustion temperature by heating the combustion air with the waste heat of the flue through the heat exchanger, which can also reduce the fuel consumption by 5 ~ 10%

1.5 by using advanced kiln furniture to increase the kiln density by more than 50%, the product to kiln furniture ratio of traditional kiln is 1:7, while the product to kiln furniture ratio of drawer kiln is only 1:2.5

through the adoption of the above measures, the fuel consumption index has decreased significantly, taking the production of corundum protective tubes as an example; In the past, the fuel consumption of traditional kilns was 10.42kg/m diesel oil, but now the drawer kiln is reduced to 2kg/m, saving 8kg/m diesel oil. At present, dozens of existing production enterprises in China are still using traditional kilns for production, with an annual output of more than 3 million linear meters. According to the current calculation of 3 yuan per kilogram of diesel, the annual fuel cost savings alone will be about more than 70 million yuan. In addition, increasing the kiln density and shortening the firing cycle will increase the output and quality benefits, as well as the potential benefits of reducing environmental pollution, which will be very significant

2 composition and characteristics of high-temperature drawer kiln

through extensive investigation and demonstration at home and abroad, the drawer kiln we designed consists of a rectangular kiln external protective metal frame and kiln car, kiln furniture, fuel oil, atomizing air, combustion supporting air (including heat exchanger), control and other systems. The following will introduce the prominent problems involved in these systems

2.1 kiln body frame and kiln car

because this kind of kiln adopts light refractory materials, the wall thickness of its composite kiln wall verified according to the unstable heat transfer calculation is only 400mm, and its own strength is low. Whether the kiln body bears the transverse force of the kiln arch, or the gravity and the expansion force generated in the process of heating up, it needs to set a metal frame on the outer wall of the kiln body to bear, and connect the refractory materials with the frame through some heat-resistant steel hooks, In order to improve the overall strength of the kiln, but also limit the expansion and contraction of the kiln body in a certain range. The frames around the kiln body should be set independently with adjustment allowance

the selection of steel structural materials for the kiln frame and the design of structural form should take into account the weight of the kiln body and the air and oil pipelines that need to be supported and suspended by the kiln frame, and also take into account the beautiful appearance to improve the overall image of the kiln

because the 1800 ℃ high-temperature drawer kiln is easy to fracture at high temperature, and the internal pressure is large, it is necessary to seal the staggered joint at the expansion joint of the kiln body; Under the condition of meeting the expansion amount, the expansion joint should be as small as possible. For some small kilns of about 2m3, the expansion joint can not be set, but the expansion amount should be considered in the insulation layer between the kiln frame and the kiln body. For kilns with vault, attention should also be paid to the setting of arch foot beam, which is the guarantee of kiln arch quality

the quality of the kiln body is mainly determined by the refractory materials. At present, the lightweight refractory materials used in the lining of such 1800 ℃ high-temperature kilns, such as alumina hollow ball bricks, corundum lightweight bricks, etc., have a service temperature limit of 1800 ℃, which requires careful selection of manufacturers with guaranteed quality to purchase, so as to ensure the quality of this kiln

the difference between this kind of kiln car and the traditional kiln car is that a smoke exhaust outlet is set in the center of the kiln car, which is connected with the flue under the car. Due to the high temperature of this kiln, the normal working temperature between the upper surface of the flue and the lower part of the kiln car's smoke exhaust outlet can reach more than 1000 ℃ at the clearance (1~2cm), which requires that the fire must be separated by refractory materials in the inner layer of the flue to prevent the flame from directly contacting the heat-resistant steel structure of the kiln car. At the same time, because the heat-resistant steel structure is welded on the kiln frame and close to the kiln wheel shaft, its heat is directly transmitted to the bearing in the wheel, which is very easy to cause the kiln car to lock in the kiln due to the high temperature of the bearing. Therefore, we have taken a set of corresponding cooling measures to reduce the temperature under the vehicle from above 500 ℃ without cooling to below the normal working temperature of 200 ℃

the application of this set of cooling scheme solves a major obstacle in the development of such high-temperature kilns

2.2 fuel system

the fuel system is mainly composed of oil storage tank, filter, oil flowmeter, gear oil pump, pressure regulating valve, pressure stabilizing tank, nozzle, regulating valve and pipeline

the key problem of this system is to choose a reasonable nozzle, which is also the key to whether it can burn to a high temperature of 1800 ℃. Since such kilns change from low temperature to high temperature, the high-speed nozzle needs to have a large adjustment range, and the fuel atomization is always good in the large oil volume adjustment, so that the fuel can be fully burned. In addition, the high-speed fire-burning injection performance of the nozzle makes the temperature difference within the injection range very small, and has a large stirring effect, so that the temperature at all points in the kiln is very uniform. When selecting the nozzle, its thermal energy should also be considered to meet the requirements of heating rate in the range of 1600 ~ 1800 ℃

2.3 application of combustion supporting air system and heat exchanger

the key problem of this system is to use the waste heat of flue to heat the combustion supporting air through the heat exchanger. Its purpose is to make the atomization effect of nozzle fuel oil better, and reduce the influence of combustion supporting air cooling air on temperature when entering the kiln, so as to speed up the heating rate, improve the combustion quality, reduce environmental pollution and save energy consumption

the heat exchanger of the high-temperature drawer kiln we developed is installed in the flue under the kiln, because the exhaust temperature here is high and easy to install. The temperature of combustion supporting air after heat exchange is about 300 ℃, because 400 ℃ to 600 ℃ is better from the perspective of nozzle atomization, but smoke exhaust equipment, heat exchanger, and air supply pipeline need special treatment. For example, the general heat-resistant smoke exhaust fan is only 350 ℃, which is lower than 350 ℃, and some auxiliary equipment can meet it without special treatment

2.4 selection of kiln furniture

at present, the kiln furniture used in drawer kilns mostly adopts brick columns with small volume and mostly hollow, shed plates with large surface but thin wall, and square hollow beams. Their products can be burned and hung according to the shape needs. Theoretically, only corundum kiln furniture is used in the large-scale production of 1800 ℃ kiln in China, but its heat storage and conductivity are far inferior to recrystallized silicon carbide kiln furniture. Although recrystallized silicon carbide kiln furniture is generally recrystallized and sintered at 2200 ~ 2300 ℃, it can be that high-temperature oxidation is serious at 1800 ℃, so the service cycle is short. However, due to the characteristics of recrystallized silicon carbide kiln furniture, such as low heat storage, high conductivity, good geometric shape, and the use of such kiln furniture can greatly improve the density of the kiln, its high added value due to the extremely weak electrical signal output by the extensometer, the products still have advantages in the relative ratio between the benefit of increased output and the cost of kiln furniture. Therefore, 1800 ℃ kilns also use such kilns in key parts

according to the practical results, it is proved that corundum brick columns and shed plates should be used for stacking and firing products in such kilns; Corundum brick columns and recrystallized silicon carbide beams should be used for hanging and burning products

2.5 control system

the control system of this kind of kiln is generally composed of temperature control, combustion air pressure control, kiln pressure control, etc. The principle of control is: send the signal (millivolt value) of the temperature measuring couple on the kiln to the temperature control display instrument in the control panel, compare it with the parameter value set in the instrument, and feed it back to the executive structure of the oil pump or valve to adjust the fuel flow and control the temperature; The change of oil quantity is fed back to the mixing regulator through the flowmeter, and the mixing regulator controls the change of combustion air according to its set proportion. Kiln pressure is that the sensor feeds back the pressure signal in the kiln to the kiln pressure controller, which controls the opening of the flue gate according to the set value

at present, the technology of automatic control of domestic kilns has been relatively mature, but the investment of control system accounts for a large proportion of kilns. An advanced automatic control system that brings reliable operation guarantee for business friends has invested nearly one million. Because the scale and volume of the kiln are different, the proportion is also different. The smaller the kiln is, the larger the investment proportion of the control system is. Therefore, the selection of the automation degree of the control system should be combined with the actual needs of the kiln. For example, for some kilns of 2 ~ 5M3, if manual control is selected, it will save a lot of investment, which generally only needs tens of thousands of yuan to complete

3 conclusion

1800 ℃ high temperature drawer kiln is still in its infancy in China, and there are still many problems that need to be improved as soon as possible; Such as kiln furniture, which has restricted the development of such high-temperature kilns, is in urgent need of further development by peers at home and abroad. With the approaching of China's entry into the WTO, the market competition will be further fierce. If enterprises do not have advanced technology and equipment as the backing, they will have endless worries

due to the limited space of this article and the scope of my grasp, there must be a lot of ominous things. I hope relevant leaders, experts and colleagues can make corrections

references

1 Yu Lida Thermal balance calculation of ceramic equipment Beijing: Light Industry Press, 1990

2 song Zhuan Thermal analysis and Simulation of ceramic kiln Beijing: Light Industry Press, 1993

about the author

Niu Zhiliang, born in October 1960. He graduated from Wuhan University of technology in 1989, majoring in silicate, and has been mainly engaged in the development and design of ceramic thermal engineering and building materials projects for many years. Now he is the deputy chief engineer of Shenyang building materials design and Research Institute. He has won many scientific and technological achievements and awards, such as the introduction of the West German project "preparation of ceramic rollers in ceramic roller kiln", the introduction of the Japanese project "development of medium and high-grade sanitary ware" and "Application of phosphogypsum to gypsum board". He has also presided over the feasibility study, expansion and demonstration design of construction drawings of dozens of projects specializing in ceramics, glass, cement and new wall materials. 1800 ℃ energy saving fuel