[China Glass Network] The glass industry is a large energy consumer. There are thousands of glass furnaces in China. The thermal efficiency and thermal energy utilization rate are relatively low, and the product consumption is large; the cost is high. It can be said that the competition in the glass market mostly depends on energy. Therefore, energy conservation has become the central task of kiln renovation, and has been included in the “Eleventh Five-Year†national energy conservation and environmental protection key projects.
Reviewing the development history of China's glass industry, it is not difficult to find that oxygen-enriched combustion-supporting technology was proposed as early as the early 1950s, but in view of the fact that oxygen-making technology itself consumes a large amount of electrical energy, this technology and electric fluxing Compared with the "excessive move". Therefore, before the problem of oxygen source is completely solved, the indirect energy-saving approach of “electricity-oxygen-oxygen-enriched combustion†is not easy to accept. In the 1970s, with the advent of new polymers, membrane-forming technology The improvement of foreign countries has done a lot of work in the field of oxygen-enriched combustion, and has made many gratifying progress, laying a favorable foundation for the promotion and application of this technology.
I. Application of oxygen-enriched combustion-supporting technology in foreign industries
As early as 1982, the United States, Japan, the United Kingdom, France and other countries engaged in the development and application of membrane oxygen enrichment technology. They carried out research work on product trial production, production amplification, process design, process optimization and combustion application from membrane materials, film forming technology, components and devices, and carried out analysis and testing methods and development of analytical instruments. The oxygen concentration is 28%-40% oxygen-enriched air, the device, the gas production from several liters / min to 1000m3 / h different specifications of the product, and industrial test, in the gas, fuel and coal burning different occasions The test confirmed that 30% concentration of oxygen-enriched air can be used for industrial combustion support, and combustion with 23% oxygen-enriched air can save energy by 10%-25%. By the end of the 1980s, nearly 20 large and small companies in Japan have introduced membrane oxygen enrichment devices. In terms of oxygen-enriched combustion, Japan Osaka Gas Company and Matsushita Electric Co., Ltd. have cooperated in the slab heating test furnace, ceramic firing furnace, and glass kiln, and achieved good energy-saving effects. A glass factory in the United States increased the oxygen content of combustion air to only 23%, which resulted in a good result of saving 8%-10% of fuel, and the yield increased by 3%-10%, and the output increased from 106t/d to 119t/ d, the number of ash bubbles decreased by 40%, and the furnace age was extended by 5-6 months. In France, a glass factory used oxygen-enriched combustion on the pool furnace, which increased the flame temperature in the lower part of the furnace by 1000C and the top temperature by 300C. The output increased from 120 t/d to 150 t/d.
Second, the basic characteristics of local aeration technology
At present, the introduction of oxygen into the glass melting furnace has four basic methods: an oxygen-fuel spray gun, an air-oxygen-fuel spray gun, a secondary air premixing, and a partial spray of oxygen under the spray gun. The first three are the overall gas-enhancing measures, and the latter one is the local aeration.
When designing a combustion system for a glass melting furnace, the following five factors must be considered.
(1) transferring the thermal energy of the fuel to the glass to a greater extent;
(2) transferring the heat of combustion to the upper structure of the furnace less;
(3) The combustion of the fuel is limited only to the melting zone in the furnace;
(4). Try to avoid the flame from scouring onto the surface of the refractory material;
(5). Effective mixing of fuel and combustion air to reduce heat loss due to excess air in the flue.
Third, the mechanism of energy saving and pollution control of oxygen-enriched combustion technology
1. Increase the flame temperature:
After the oxygen-enriched air is burned, the amount of nitrogen is relatively reduced, so that the oxygen molecules are rapidly mixed with the combustibles to achieve full combustion, so that the flame temperature increases with the proportion of oxygen molecules in the oxygen-enriched air, and the radiation is accelerated. Three forms of heat transfer rate of conduction and convection.
2. Speed ​​up the burning speed
The reason why the fuel burns faster in oxygen-enriched air is that it increases the flame temperature by increasing the oxygen content. For example, natural gas can be burned 10 times faster in oxygen than in normal air. An increase in the rate of combustion results in rapid and complete combustion of the fuel in the furnace.
3. Reduce the ignition temperature of the fuel
The ignition temperature is significantly affected by the reaction rate and heat loss. Oxygen-enriched air helps reduce the "burning point" temperature characteristics and increases the heat release per unit volume of the flame. The effect on poor quality fuel is more prominent.
4. Reduce the amount of exhaust after combustion
Oxygen-enriched air with an oxygen content of 29% is used for combustion. Compared with ordinary air combustion, when the excess air ratio a=1, the exhaust volume is reduced by 20%, and the exhaust heat loss is also reduced by 20%, thereby improving thermal efficiency. And energy saving.
5. Increase heat utilization
When the heating temperature is 1300 ° C, it is burned with ordinary air. Its heat utilization rate is 42%, and when it is burned with oxygen-enriched air containing 26% oxygen, the utilization rate is increased to 56%. As the heating temperature increases, the energy saving effect is more remarkable.
6. Reduce the air excess coefficient
Oxygen-enriched combustion can effectively reduce the air excess coefficient and greatly reduce the heat loss of the exhaust gas, thereby improving the thermal efficiency of the furnace and saving energy.
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