China Ceramic Kiln new technologies and new processes

Sustainable development of ceramic industry is facing severe challenges the natural ecological environment , energy shortages gave the development of ceramic industry made increasingly stringent requirements. Saving energy and reducing pollution is a ceramic kiln ceramic production trend, ceramic industry is an important condition for sustainable development . In this year''''s " Third International Ceramics Industry Development Forum", South China University of Technology Ph.D. advisor Professor Zeng Lingke of Chinese ceramics kiln development of new technologies and new processes specified in the direction. This article is an outline of his speech , and I hope the industry inspiration .
A furnace structure
● intermittent kilns
Energy consumption, low yield , the exhaust gas temperature at 600 ℃ ~ 860 ℃.
Affect shuttle kiln temperature field uniformity of key factors:
① The new burner , such as: isothermal burner, pulse burner , high-speed burner .
② to adjust the layout of the burner ,
③ improve the placement of the code blank ,
④ reasonable layout flue ,
⑤ For the shuttle kiln , waste heat utilization ,
⑥ Select the appropriate temperature measurement points and control methods.
● Continuous furnaces
① tunnel kiln
Temperature, especially preheating zone ; kiln walls, kiln car heat storage capacity , high energy consumption 2400-12000 × 4.18kJ/kg products ; adopting some new technology energy consumption can be reduced to 1100-5200 × 4.18kJ/kg . Adoption of new technologies : no box naked burning , light insulation , lightweight kiln car . There key issues: reducing firing atmosphere detection and control
② roller kiln
       ● Lower power consumption : low as 200-300 × 4.18kJ/kg products ;
● yield : more than 220m long kiln , ceramic tile production 10000m2 / d or more ;
● reasonable control of atomization air pressure and combustion air volume
● reasonable adjustment exhaust fan , pumping hot air extraction volume
● reasonable set of baffle wall , retaining the fire board
● Extend the length of the flame burner or extended , " Fire into heart"
● In the structure, the whole kiln kiln built flat or full arch structural transformation of firing zone building arch structure, can effectively reduce the cross-sectional temperature .
Two insulation technology
● heavy firebrick : quality, heat capacity, thermal conductivity heat storage , thermal capacity, the kiln wall surface temperatures up to 300 ℃ ~ 400 ℃.
● lightweight insulation tiles,
● mullite brick,
● High Alumina Brick ,
● lightweight ceramic fiber , light weight , low thermal conductivity , lightweight material weighs only 1/ 6, the bulk density of the traditional brick 1/25 , heat storage capacity of only brick -type lining of 1/30 to 1/10 the kiln wall temperature dropped to 30 ℃ ~ 60 ℃. The use of lightweight ceramic fiber , lower quality than products and kiln furniture .
● fiber energy , 20.6% of the total energy consumption dropped to 9.02% , up 16.67% energy saving .
● fiber powder,
● chalking research,
● anti- chalking
● kiln wall structure more reasonable , better energy-saving effect .
Three firing technology
● using the new burner : isothermal burner, pulse burner , high-speed burner .
● Adjust the burner layout .
Four coating technology
● a wide range of coating technology , wherein the infrared radiation layer and multi- layer application in the furnace of concern .
● Infrared heating the coating process is simple , low cost, infrared emission rate with significant energy savings.
● Protect the kiln wall is not subject to chalking : the kiln off the dirty, fiber powder
● Increase the infrared radiation heat transfer and thermal efficiency : at high stage, its painted walls in the kiln refractory , material radiation rate of 0.7 liters 0.96 per square meter per hour energy 33087 × 4. 18kJ, while at low temperature phase coated HRC , the kiln wall emissivity from 0.7 to 0.97 liters per square meter per hour energy 4547kcal.
● avoid secondary drop dirty .
Five harmful gas generation mechanism
● ceramic kiln flue gas harmful components : NOx, SOx, CO, CO2, ROx dust
● NO formation mechanism :
① Thermal type NOx: nitrogen in the air is oxidized , primarily due to the flue gas temperature and oxygen concentration in the flue gas temperature of 15000 ℃ above , NOx increase exponentially .
② Fuel type NOx: N in the fuel is oxidized , and the N content in the fuel .
③ fast-type NOx: content of less than 5% in general , mainly in the fuel-rich flame section .
● SOx generation
① sulfate decomposition of the raw material body , such as: pyrite, sulfate oxidation.
② oxidation of sulfur in the fuel , such as: organic sulfur , pyrite, sulfate, etc. oxidation .
Six suppression technology
● Reduction : Selective catalytic reduction SCR, adding a reducing agent such as NH3 reduction in catalyst NOx, reduction rate of 90% ; selective non- catalytic reduction SNCR, adding a reducing agent such as NH3 under high temperature reducing NOx, reduction rate of 30 % -70 % . Easily cause secondary pollution , catalyst deactivation , corrosion of equipment .
● Plasma Technology : Plasma process flue gas NOx control technology is the core through a certain way in the flue gas to generate plasma , NOx and other polluting gases in the plasma zone is decomposed or oxidized. The cost of equipment is still in the experimental stage.
● microbiological method : a suitable carbon source, denitrification bacteria are applied in the case , the use of nitrogen as NOx , the NOx oxidation basic harmless N2, the denitrification bacteria growth and reproduction of its access , removal efficiency 99%. Anaerobic environment is difficult to guarantee .
● electrochemical method : the use of electronic as an intermediate oxidation or reduction NOx, removal rate of 90%. Process temperature is low , the electrolyte is not easy to transport . China Insulation Materials Network
● acid oxidation method : the use of strong oxidizing properties of acid treatment, NOx and SOx removal rate of 95 % or more.
● Microwave Technology :
① pyrolytic carbon ( or activated carbon ) is both an excellent radio frequency energy absorbers, but also a good performance of the reducing agent. When the activated carbon is placed in the radio frequency energy field , the gas phase of the SO2, NOx and RF energy field in contact with the coke , carbon can quickly capture these oxides in oxygen than the speed of which is deprived of oxygen there is no RF fields exist faster.
② process is simple, high treatment efficiency , no secondary pollution , small investment , installation is simple , low energy consumption .
● multifunctional coating removal NOx:
① in the sunlight and ultraviolet light on the multifunction coating irradiation , NOx photocatalytic degradation rate of up to 55%.
② In the beginning of the reaction , NOx soon degradation rate reached 50 % or more , 6h after little change , to the saturation value of 80 % or so.
③ When the NOx flow rate of 0.1L/min, a contact time of the reactants the NOx degradation rate 76.3s maximum , 40.2 % or more.
④ The coated glass plate light catalytic coating placed outdoors , every 10 days, washed with water 1, test 1 month degradation effect on NOx results show that , in the outdoor for 6 months after the coating on the oxidative degradation of the NOx little effect reduction , decrease only about 2% 3% , the coating appearance change.
Seven microwave-assisted sintering technique
● microwave and conventional sintering firing difference.
● Microwave-assisted gas fired technology (MAGF) is a more practical and reasonable environmentally clean burning technologies.
● completely avoided by microwave sintering techniques produce CO, CO2, SO2 and NOx emissions, such as thermal efficiency ? Gou Yun- chu line and Aye Aye Farmer bear ?
● In China, the microwave sintering technology in high-performance ceramics and porcelain firing has been tried , but in daily-use ceramics , architectural ceramics is still blank .
● In other countries, such MAGF technology has been successfully in a variety of refractory materials , ceramics and sanitary ceramics firing has been applied and from the laboratory stage to the small-scale production .
● According to foreign sources, using MAGF firing technology can yield four times , saving more than 70% , down 40% in energy costs , the amount of harmful substances evaporate a significant reduction in the mechanical properties also improved.
Eight measurement and control technology
● Fuzzy Control :
Advantages : For the nonlinear ceramic kiln , it is difficult to model regarded as a good control object control method .
Disadvantages : The control accuracy is not high , adaptive capacity is limited , there is a steady-state error , it may cause oscillation , the lack of effective learning mechanism .
● Single point of fuzzy control : control object is usually the furnace temperature , the ceramic kiln firing process control characteristics under the influence , resulting in the design of fuzzy control rules inappropriate or incomplete affect its control effect.
● Multivariable Fuzzy Control:
① For having a diverse, random , continuous , highly uncertain and other characteristics of the control object , to a multi-level , multi-objective integrated results. China Insulation Materials Network
② core technology : soft embedded multivariable model-free self-learning fuzzy controller.
● sectional flow control :
① In the preheating chamber with the specific position of the lower kiln burner installation of certain speed , increase the agitation of the upper and lower air flow , reducing the cross section of the upper and lower temperature .
② in the firing zone and cooling zone of the kiln a distance from the top of each set hanging refractory fiber " barrier ."
③ In the top of the kiln burning zone and the burned products between the upper edge of the upper burner reasonable choice of the best locations.
④ In the cooling zone , the top and bottom products, a plurality of discharge air into the drum to quench with cold or hot temperature .
⑤ kiln for a wide cross-section should be appropriate to extend the length of the flame , avoiding cross-section of the hump temperature distribution .
Nine computer simulation technology
● entity model : Water model , the flame model , the aerodynamic model
● FLUENT software values:
① simulated wood kiln convective heat transfer process ,
② simulated roller kiln burner layout perspective on the impact of the flow field inside the kiln ,
③ Analog shuttle kiln flow field, convection heat transfer coefficient on the law and uniformity of kiln heat exchanger ,
④ Analog ceramic firing process the various factors affecting NOx formation .
Ceramic kiln direction of development :
● in the kiln structure, the continuous development of the longitudinal direction of the furnace ,
● In the kiln , kiln furniture materials , use of lightweight ceramic fiber ,
● the use of coating materials, save energy and reduce the emission of pollutants ,
● In the firing technology , the high temperature uniformity , low pollution direction, such as microwave sintering technology,
● In the detection method , using multivariable control technology,
● the research method , the thermal furnace combined theoretical and computational fluid dynamics ,
● green ceramic kilns kiln workers is the task of the new century