At present, our country faces a very severe situation of energy saving and emission reduction, and thesteel industry is the energy consumption of our country, its total energy consumption accounted for about 15% of the country's total industrial energy consumption. Compared with the international advanced level,comprehensive utilization of resources and energy indicators of China's iron and steel industry gap. Therefore, the utilization of heat energy in the steel industry, has a huge role in promoting energy saving and emission reduction work.

Reheating processes, for example, emissions of waste heat resource consists of physical heat, Shui Liangand upright cooling of flue gas heat, furnace wall and hearth opening heat, open oven and heat, burningloss of billet physical heat, iron oxide physical heat. Among them, the cooling of the furnace wall, furnace openings at the end of the heat sink, open the oven and cooling, iron oxide burning physical heatdue to less emission and dispersion, it is difficult to concentrate on recovery. However, accounting for about 42% of energy consumption in heating furnace flue gas heat in physics, Shui Liang and post heat accounts for 92% of low-quality heat sources, energy consumption is equivalent to 724MJ/t. Meanwhile, bothsensible heat is relatively concentrated, easy to recycle.

Utilization of layer-by-layer analysis

Evaporation cooling in heating furnace (ECS) recovery of walking beam heating furnace heat. After 2000,the technology in the rapid promotion of domestic metallurgical enterprises, now almost all newly built orrebuilt for walking-beam heating furnace using evaporative cooling. Evaporative cooling low vapourpressure of domestic heating furnace, mainly used to supply industrial users and heating and so on. Waste heat of heating furnace heat, evaporative cooling (ECS) in the recovery boiler temperature of about 1000℃ high temperature flue gas heat, which belongs to the high-temperature waste heat recovery.

Sets of air preheater heating furnace flues, heating furnace with high temperature flue gas that heats theair to about 600 degrees, hot air is fed into the furnace wife burning. This way is taken from the angleof technology in heating furnace for energy-saving measures for heating technology is directly effective,saves fuel consumption. Can recover waste heat of air preheater, 60%~70% in flue gas waste heat can beused for recycling, saving 20%~30% fuel consumption. In theory, the combustion air preheating 100 â„ƒ,heating furnace energy saving of about 5%. Therefore, the higher air preheat temperature energy-savingeffect is better. This method has been widely used in a variety of furnace. Air preheater recovery of heating furnace flue gas at the outlet of heat, and flue gas temperature 700 â„ƒ and above, belongs to medium-temperature waste heat recovery. Comprehensive utilization of waste heat recovery of heatingfurnace temperature is currently's most energy-efficient way.

Waste heat boiler flue gas at low temperature waste heat recovery. After preheater of heating furnace flue gas temperature of 300 c ~500 c, lower temperatures, can be recycled using heat recovery boiler, which belongs to the low temperature waste heat recovery. Some developed countries attached great importance tolow-quality heat recovery, advanced this heat waste heat recovery boilers commonly used by steelmakers, were all in the 70%, Japan Nippon Steel, gold and even 92%. At present, the reheating furnace with waste heat boiler flue gas waste heat recovery method is not common, but in support of the national energy-saving emission reduction policies, recovery and utilization of low temperature heat source has been taken seriously. SG type flue gas waste heat recovery heat exchangers are ideal for the taste.

Evaporative cooling can not meet the needs of lower heating furnace flue gas temperature, both at home and abroad by air and flue gas waste heat recovery of gas preheater, but cooling is also restricted. Furnacewaste heat boiler furnace flue gas temperature can be reduced, but an earlier auxiliary burner must beused to produce steam, energy consumption is large, and most of them equipped with by-pass flues project covers an area of and the initial heavy investment. Combining the characteristics of existing furnaces,high temperature and medium temperature and low temperature waste heat of heating furnace for a unifiedorganization, forming modular cascade recycling process of waste heat system, input-output ratio furtherimproved its energy consumption is inevitable. Cisdi for waste heat recovery of heating furnace of steel rolling production processes in China use proposed cascade of waste heat recovery of a compositionoptimized and well structured processes and procedures, and related core technology research.

Cascade developed into one

Cascade of waste heat recovery of heating furnace systems are high and low depending on the nature of heat sources of heat and temperature, evaporative cooling, air heaters and boilers, organically combined intoone reasonably to maximize heating process waste heat recovery, substantially reducing flue gastemperature to minimize engineering investment, greater economic and social benefits.

Level (high temperature) recovery process research and development. Cooling of water beam in heatingfurnace is divided into water cooling and evaporative cooling. At present, the evaporative cooling withgood water and effectively protect water beam, extended longevity, saving water and electricity andrecyclable water beam steam advantage is in cooling mode, been adopted by most of the heating furnace. Athome, the technicians carried out a study on heat load of beams and columns of water, through theestablishment of water beam in heating load model determined control measures of the water cycle,evaporation cooling design developed by software engineering, meet the thermodynamic calculation,equipment calibration calculation the calculation of hydrodynamic circulation water beam of a variety ofengineering requirements.

Class II (moderate temperature) recovery process research and development. Secondary recovery process isdirect measures of energy saving, energy-saving effect is obvious. Our technicians building experimentalplatform for efficient heat exchanger, experimental study of the key technology and equipment, hasachieved fruitful results, multiple products. Its main advantages are high heat transfer coefficient,simple structure, long life, good flexibility and rigor.

Three levels (low temperature) recovery process research and development. According to heating furnace process forced row smoke and natural row smoke, and single smoke road and double smoke road of different features, technicians for natural cycle and forced cycle heat boiler of characteristics, on traditional smoke road heat boiler for has match sex research, and according to this on General heat boiler for has structure optimization, development out metallurgical heating furnace smoke road built-in type steam heat boiler, solution has heating furnace safety and heat boiler coordination run of major problem. Meanwhile,researchers developed based on engineering test results correspond to the design software, realized with adesign requirement calculations, three-dimensional output of waste heat boiler and other functions,provides a platform for structural design of waste heat boiler.

Then dig for combinatorial optimization potential

Technicians using clip points theory on combined heat recycling processes for has energy optimization, development out metallurgical heating furnace vaporization cooling and smoke road built-in type heat boiler of joint device system; on heat cascade recycling system may appeared of with mass subsystem and function same of equipment for has combination optimization; on engineering Shang reflect of repeated investment, and accounted for to big, and based inputs more of problem for has layout optimization.Meanwhile, work has developed a modular product to find investment, quick-impact projects applicationentry point.

Cascade of waste heat recovery system for the effective control of heating furnace temperature, pressureand other indicators, combining subsystems into a single organism, and achieve efficient recycling and useof waste heat resources, technical personnel of each process automatic control system and processoptimized linkage between systems, which developed the United and stable running of automatic control technology.

Combined recycling benefits

Cascade of waste heat recovery system of the heating furnace furnace exit gas temperature can be reducedto below 200 â„ƒ. To waste heat of the Handan iron and steel have been produced for the project, for example, the cascade of waste heat recovery system of a one-time investment of only separate evaporationcooling and heat recovery boiler of two-thirds, independent works about 13 million Yuan. Throughtechnological innovations of this project, which was about 8 million Yuan, and through the system andlayout optimization, reduced operating costs, and maintenance costs, cost saving over 25%, with obviouseconomic benefits. In addition, evaporation cooling and heat recovery boiler to generate steam directlybenefit about 5 Yuan/tons of steel, payback period can be shortened to 1 year ~2 year.

Cascade of waste heat recovery system of the heating furnace technology support project in Handan iron and steel, Baosteel and other large-scale iron and steel enterprise won the practical application of heatingfurnace, flue gas temperature, and other indicators have reached the expected results.