Industrial coal-fired boilers how to save energy?

Industrial boiler is an important thermal power equipment, generally refers to the capacity of less than or equal to 65 steam tons / hour, the pressure is less than or equal to 3.82 MPa, the temperature is less than or equal to 450 ° C boilers of various capacities and parameters, which are widely used in plant power, heating and ventilation, combined heat and power and domestic hot water supply, the demand for a large number of end of 1998, the country's industrial boilers in use totaled At the end of 1998, the total number of industrial boilers in use nationwide was 501,200 units, or 1,256,900,000 steam tons, with an annual consumption of about 300 million tons of coal. Due to the small capacity of the unit, mixed manufacturers, product quality varies, coupled with the supply of raw coal without washing and processing of coal supply is dominated by a large proportion of fine-grained coal, combustion equipment and fuel characteristics are not adapted to the mismatch of auxiliary equipment and operation of low level of operation, the boiler efficiency is generally low.

Because of the product technology level and operation level is not high, low boiler efficiency, coupled with a large amount of wide-ranging, the national industrial boiler annual emissions of greenhouse gases carbon dioxide carbon dioxide of about 160 million tons of carbon, 3.8 million tons of soot, carbon dioxide 5.3 million tons and a large number of nitrous oxides, is the main source of atmospheric environmental pollution emissions one of the sources.

So with energy-saving technology for industrial boiler units to carry out the necessary transformation to eliminate boiler defects and improve the combustion equipment and auxiliary systems, so that it matches the characteristics of the fuel and the working conditions, so that the boiler performance and efficiency to reach the design value or the international advanced level, so as to achieve substantial energy savings and to achieve environmental protection targets. For example, Beijing Lugu Heating Plant invested 200,000 yuan, with stratified combustion technology on two 40-ton / hour hot water boiler renovation, after the transformation of the boiler efficiency reached 83%, the boiler output increased, the heating capacity of 800,000 square meters to 1.31 million square meters, and dust emissions decreased, the entire investment in a heating period will be fully recovered. If the stand-alone capacity of 10 tons / hour as the basis for calculating the boiler efficiency from 62% to 80%, to run 5,000 hours a year, the annual savings of 218 tons of coal, equivalent to 156 coal equivalent, energy saving rate of 22.5%, 109 tons of carbon dioxide emissions. If 30% of the national industrial boilers for energy-saving renovation, according to the efficiency of 15 percentage points, the country can save 12.9 million tons of coal equivalent standard coal, carbon dioxide emission reduction of 9.03 million tons. Therefore, the market potential is huge, economic and social benefits are good.

Double zigzag energy-saving furnace arch

Most of the industrial boilers in operation in our country are chain furnaces of less than 35 tons/hour, and the furnace arch is only adapted to the typical design coal. In actual operation, due to the complexity of China's coal, the quality of varying, thus often resulting in poor boiler combustion, low efficiency. The energy-saving furnace arch technology of Shanghai Jiao Tong University effectively solves the common boiler problems.

Shanghai Hudong Shipyard is China Shipbuilding Industry Corporation's large-scale backbone enterprises, the plant's power center boiler room has two 10-ton / hour chain coal-fired steam boiler, to the whole plant to supply the production and living steam. When the quality of coal is poor and the moisture content of coal is large after rain, the boilers burn poorly, resulting in insufficient output and affecting production. Later, the plant adopted the "double zigzag wide coal type energy-saving furnace arch technology" of the Department of Energy Engineering of Shanghai Jiaotong University, and successively reformed the two boilers, which achieved good adaptability of the boiler coal type, high output, low carbon content of the slag, and strongly ensured the production operation.

(1) double-shaped wide coal type energy-saving furnace arch technology

Boiler in the actual operation of often encountered poor quality coal or rain-drenched wet coal ignition difficulties, difficult to burn out the problem, resulting in a reduction in the thermal efficiency of the boiler, the evaporation does not reach the rated value, and the chimney from time to time black smoke, causing environmental pollution. This has a lot to do with the structural design of the furnace arch, because the arch is usually designed according to the selected coal type, poor adaptability to different coal types. To parabolic front arch and horizontal rear arch of the fast-loading boiler, for example, such a furnace arch structure is often in the rear arch temperature is low, difficult to ignite poor quality coal or rain wet coal due to the flame burning range is short and difficult to burn, resulting in poor combustion of the boiler, low efficiency, insufficient output and other phenomena.

The key to solving the above problems is to improve the furnace arch to increase the furnace temperature and extend the combustion range. The "double-herringbone wide coal energy-saving furnace arch technology" is based on the principle of aerodynamics, the use of radiation heat transfer theory of the front arch, creative front and rear arches designed to guide the high temperature of the furnace flue gas flow direction of the herringbone, so as to solve the general boiler coal adaptability of the common disease of poor.

The herringbone front arch ensures that the flame flows smoothly upward out of the arch area and radiates heat effectively to the new coal, improving the drying and catching ability of the coal. The depressed bottom of the front arch, in turn, prevents the flame from burning the coal gate and coal hopper. Longer than the original, and has a certain degree of anti-inclination of the herringbone back arch, can maintain the back arch area enough furnace temperature, so that the flame burning range extended, easy to coal residue burning clean, but also can guide the back of the high-temperature flue gas flow to the front arch area, to increase the temperature of the front arch area, is conducive to the poor quality of the coal and the wet coal of the rain catching fire combustion.

(2) technical and economic analysis

Through the Hudong Shipyard center boiler room in September 1994 to May 2000 steam production, coal consumption, electricity consumption and other statistics by month, combined with the Shanghai Energy Conservation Inspection Center on the 10-ton/hour boiler on-site testing. The following conclusions:

The furnace temperature increased by 80 ℃ ~ 100 ℃, slag carbon content from 15% to 19% before the transformation to 7% to 9%, the boiler's thermal efficiency from the original 69.29% to 77.64%; 2914.5 tons of coal, equivalent to 2081.83 tons of standard coal, electricity savings of 200,000 degrees, saving money 941,900 yuan, emission reduction of CO2 5639 tons.

The total investment of the project is 107,600 yuan, and the project payback period is 6 months.

Compound combustion technology

Qiqihar Brewery is a modern beer producer with an annual production capacity of 70,000 tons, integrating wheat-making, brewing and packaging. The plant's beer production process of heating, sterilization and other steam required by the power plant to provide. Power workshop boiler room original 1 10 tons / hour and 2 sets of 6.5 tons / hour chain boiler, 3 boilers with a total output of only 12 tons / hour, the thermal efficiency of 50% to 65%, of which 10 tons / hour boiler output of only 6 tons / hour, the thermal efficiency of 65%, the operating condition is poor, can not meet the requirements of production. Therefore, the plant used composite combustion technology for 10 tons / hour chain boiler renovation. After the transformation, only the output of this boiler can reach 14-15 tons / hour, thermal efficiency of 75%, and stopped two 6.5 tons / hour boiler, not only to meet the needs of the enterprise steam volume, but also according to the production demand for rapid adjustment of the load, and can adapt to different types of coal, greatly reducing production costs.

The total investment of this project is 452,000 RMB. After being put into use, it saves 1,758 tons of raw coal/year, saves electricity about 150,000 degrees/year, and the annual comprehensive benefit reaches RMB 391,000 yuan, and reduces carbon dioxide emission by 3,416 tons per year, with a payback period of 1.2 years (coal price is calculated at RMB 180 yuan/ton, and electricity price is calculated at RMB 0.5 yuan/degree). For the use of chain boilers, coal thrower chain furnace, fast-loading boilers, reciprocating push grate boiler enterprises, if the actual boiler output is insufficient or need to increase capacity, the project technology transformation, are meaningful.

Compound combustion technology chain boiler is a commonly used combustion equipment, widely used in China's industry, 75 tons / hour steam boiler and 29 megawatts below the hot water boiler more than the use of such combustion. Although the chain boiler is a better combustion equipment, but there are some shortcomings in the use, mainly when the coal varies, the coal quality is bad, resulting in insufficient output, low thermal efficiency, the operation of the actual output is generally better than the rated output of 60% to 70%, a small number of bad operation is only about 50%, the actual thermal efficiency of only about 60%.

The main purpose of the chain boiler and pulverized coal composite combustion technology is to strengthen the combustion process in the furnace, improve boiler combustion efficiency and coal adaptability. From the boiler combustion theory can be seen, to maintain a high enough temperature of the furnace is to ensure that the boiler good combustion of the first condition, high furnace temperature is the coal in the furnace drying, distillation smooth, to reach the ignition temperature of the time is short, easy to ignite. The higher the furnace temperature, the more favorable to the combustion of coal, coal adaptability is also better. In the existing coal-fired boiler combustion mode, pulverized coal furnace furnace temperature is the highest, the coal adaptability is the best, and the combustion is more complete, high thermal efficiency. Chain boiler plus pulverized coal composite combustion mechanism is the chain grate and pulverized coal combustion of these two different ways of organic combination, *** used in a furnace, mutual assistance, mutual utilization, to avoid the shortcomings. In the combustion process, pulverized coal ignited by the grate fire bed, pulverized coal combustion formed by the high temperature flame to improve the furnace temperature, for the chain grate on the coal fire provides a rich source of heat, changing the past chain furnace rely solely on the arch of the thermal radiation ignition conditions, greatly improving the chain grate on the new coal ignition conditions; at the same time, stable combustion of the fire bed is a pulverized coal airflow ignition of a reliable source of heat to ensure that pulverized coal in a timely and stable ignition. The fire bed is also a reliable heat source for the fire of pulverized coal airflow, which can ensure the timely and stable fire of pulverized coal.

The composite combustion mode not only retains the advantages of good load adaptability and convenient load adjustment of the chain furnace, but also has the advantages of good adaptability of pulverized coal furnace coal, high combustion efficiency, so that the boiler can achieve stable and efficient combustion in the case of changing loads, especially in the case of changing to burn poor quality coal in general.