With the forward development of ceramic industrial production, kiln built the increase of the amount, in kiln construction technology and effect will be put forward higher request, to the improvement of construction technology and improvement. Depended on the kiln design, development, of course, the construction technology of refractory material and the progress of construction equipment.
1, look from the recent primary stage: large-scale appropriate to make brick, so can reduce mortar joint, increase the overall strength, improve the efficiency of foot building; Gradually increase the bulk of refractory materials such as refractory concrete application, so that we can realize mechanization instead of manual, to speed up the construction progress, with the progress of particulate refractories production technology, improving quality, expanding the scope of its use; Combined with actual situation application construction method and work with other departments, as material of the conveyor belt, with pump fire clay, brick cutting with diamond cutter, etc., so as to reduce the labor intensity, improve work efficiency.
2, look from the forward advanced stage: with the development of the refractory materials and advanced heat insulation materials, kiln body laying construction will also like the ancient QinZhuanHanWa factory batch production instead of pre-cast component replaced; Like building a skyscraper built as quickly, implement the building blocks kiln (especially the tunnel kiln, etc.) instead of laying in the system of prefabricated construction method of realization kiln lining machine, the production, so as to reduce the cost and quality. So this will require kiln body gradually realize standardization, seriation.
The choice of modern ceramic kiln fuel
As a result of the need of environmental protection, modern ceramic kiln should be considered in choosing its fuel use clean fuel.
Clean fuels include: diesel, kerosene, gas, liquefied petroleum gas. Cold coke oven gas, water gas and producer gas.
1, diesel oil and kerosene
, diesel oil is used as A clean fuel its advantages are: transportation and storage is easier, less equipment investment, high calorific value and stable, viscosity is small, easily atomization, heating temperature of 2080 ~ 2100 ℃.
The disadvantage is that: the price is high, high solidifying point diesel when used in a cold environment to be heated. It should be paid attention to when choosing diesel sulfur content, such as high sulfur content, will influence the quality of product of pottery and porcelain, environmental pollution and corrosion of equipment and pipes.
B, kerosene is used as clean fuel its advantages are: low calorific value was a little higher than light diesel oil is about 42.8 ~ 43.5 MJ/kg. It is the top grade in clean fuels, solidify, smaller than the light diesel oil viscosity, easier to spray.
Defect is: flash point not below 40 ℃, otherwise use unsafe, and price is too high.
2, natural gas and liquefied petroleum gas (LPG)
A, natural gas as A fuel its combustion characteristics are as follows:
(1) because of its main composition is methane, so depends on methane combustion characteristics. Ignition of methane and air mixture concentration range is very narrow, in 5% ~ 15%. Therefore, in the process of combustion is sensitive to oxygen, but also reduces the risk of tempering.
(2) methane flame propagation velocity is small. Under the normal temperature, atmospheric pressure maximum visible flame propagation speed is less than 1.0 m/s. Thus burning more slowly. Natural gas belongs to the low gas flame propagation speed. More prone to dehydration.
(3) the gas heating temperature of about 2000 ~ 2040 ℃, for all kinds of ceramic products almost can meet the requirements of sintering temperature, using room temperature air.
(4) when its natural gas and air mixture good flame blackness is very small, for half of the liquefied petroleum gas, black density than the liquid fuel is much lower. But for modern ceramic kiln, the flame radiation heat transfer is not important. Commonly used high speed burner for flameless combustion, almost no flame.
(5) the theory of natural gas air quantity is big, about 7.8 ~ 11.2 Nm3 / Nm3, therefore the burner mixed high performance requirements, that is to say 1 Nm3, gas well with more than 7.8 ~ 11.2 Nm3 air mix.
(6) of natural gas carbon/hydrogen mass ratio (3.0 ~ 3.2) than that of liquid fuel (6.0 ~ 7.4) or solid fuels (10 ~ 30) is much lower. So the combustion product contains more H2O.
B, liquefied petroleum gas as a fuel has the following features:
(1) a high calorific value, is the highest of fuel gas.
(2) theoretical air volume up to 24 ~ 30 Nm3 / Nm3, therefore, the combustion air mixed with the complete more difficult than natural gas. Can use the air or flue gas first blunt dilute liquefied petroleum gas (LPG), and then use. But when diluted with air, shall not be within the scope of the concentration of fire explosion in case. Usually prescribed liquefied petroleum gas volume concentration must be 1.5 times higher than fire concentration range limit.
(3) the flame propagation speed is low, the combustion is slow, but faster than natural gas.
(4) purity. Is generally less sulfur, calcined high-grade ceramic products of high quality fuel.
(5) the density is bigger, which is about the same temperature and pressure of 1.5 ~ 2.0 times that of air leakage when sinking, easy to mix with air to fire concentration range, meet the fire explosion.
(6) general LPG vapor pressure is higher. At 37.8 ℃ about 0.9 ~ 1.5 Mpa. This is good as fuel gas. But in use must demand gasification station pressure reducing valve is good, to ensure safety.
3, coke oven gas, water gas and producer gas
Coke oven gas, water gas and producer gas, the synthetic gas fuel is made from coal gasification, and collectively called coal gasification.
A, coke oven gas
The average composition of coke oven gas as follows:
CO, H2 46% ~ 61% 4.0% 8.5% ~ 21% ~ 8.5% CH4 CmHn 1.5% ~ 3.0%
CO2 by 1.0% ~ 4.0% N2 3.6% ~ 26% O2 0.3% ~ 1.7%
Dry gas of low calorific value is 13.2 ~ 19.2 MJ/Nm3, belong to the calorific value of gas, its high heating temperature of about 2100 ~ 2130 ℃. Due to their high hydrogen, so the flame propagation speed is greater than natural gas and liquefied petroleum gas, under the normal temperature, atmospheric pressure maximum flame propagation speed is about 1.5 m/s. Ignition of coke oven gas range is bigger also, the lower limit of about 6%, the cap is about 31%. Coke oven gas can meet the requirements of modern various sintering temperature of ceramic kiln, and fast burning, not easy to dehydration, but tempering explosion danger some larger.
B, water gas,
The carbon in the water gas is water vapor with red coke produces the following reaction and the generated gas
H2O + CO + H2 2 H2O + C = C = CO2 + 2 H2
The generation of CO, CO2 and produce the following reaction
CO + H2O = CO2 + H2 and CO, CO2 + C = 2
Can be seen by the reactionary, water vapor is generated after carbon reduction on the number of CO and H2 molecules are equal, therefore, the theory of water gas composition was: 50% CO, H2 50%, the theory of low calorific value is 11.78 MJ/Nm3, water gas and calorific value of gas, the heating temperature up to 2200 ℃.
C, the producer gas
In the present stage in our country, the atmospheric fixed bed gasifier cold gas is very suitable for ceramic kiln, because although the coal gas belongs to the low calorific value gas, but for general sintering temperature is not too high firing of ceramic products, and fully able to meet.
Atmospheric fixed bed belongs to low calorific value gas producer gas, cold gas calorific value generally within the range of 4.49 ~ 7.62 MJ/Nm3, the heating temperature is 1650 ℃ ~ 1750 ℃, if you take air coefficient is 1.10, high temperature coefficient of 0.83, the combustion air temperature can be obtained and the relationship between the actual combustion temperature, the sintering temperature is 1280 ℃ of ceramic products, the actual combustion temperature is higher than the firing temperature about 50 ~ 100 ℃, which is about 1350 ℃, when using cold gas calorific value is 5.70 MJ/Nm3, combustion-supporting air you just need to room temperature. Such as sintering temperature of 1300 ~ 1350 ℃, the actual combustion temperature to about 1400 ℃, the combustion air temperature to 200 ℃ or so, this for general tunnel kiln, roller kiln and intermittent kiln with a heat exchanger is not difficult to do. Lower sintering temperature of 1100 ~ 1200 ℃ ceramic products, more can use of producer gas.
