Declining per ton of energy consumption of China's iron and steel industry during the past decade, energy conservation has made remarkable achievements, but some problems still exist, is facing tough challenges in the next stage of development, a very important aspect is the use of waste heat and energy problem.
The steel industry is a large-scale manufacturing process energy circulatory system between the various processes within the processes that constitute the system energy consumption, conversion, regeneration, transport, and iron and steel process has a strong thermal management features.
Approximately 40% of primary energy consumption by iron and steel production, the release of some form of heat, its temperature to 1500 ℃, under a wide range to near ambient temperature. The current production of 1 ton of steel produced by waste heat and energy resources about 8GJ ~ 9GJ, is divided into product gas, the exhaust waste heat, solid waste heat and waste gas waste heat.
The product gas of blast furnace gas, coke oven gas and converter gas, generally classified as I can, but the sensible heat and pressure to belong to the waste heat; exhaust waste heat discharged as kiln exhaust gases away the heat, accounting for the total waste heat about half the temperature range of 250 ℃ to 1000 ℃; solid waste heat to sinter, red coke, blast furnace slag, converter slag and slab such as waste heat, usually in more than 500 ℃; waste heat of exhaust steam, including steam condensate, boiler steam package sewage water (90 ℃ ~ 100 ℃), blast furnace slag in water (70 ° C to 90 ° C) of the waste heat.
Waste heat and energy use for large-scale development
The waste heat I can take advantage of the technology is widely applied. In recent years, the iron and steel industry waste heat and energy use of technology to be widely applied. Dry TRT with the rate of key large and medium-sized enterprises has exceeded 90%, generating capacity of tons of iron have more than 50kWh; CDQ proportion of key large and medium-sized enterprises reached 42.3%, tons of coke recovery steam up more than 570kg; tons of sinter recovery steam more than 70kg; gas - steam combined cycle generating units (CCPP) as the most efficient energy conversion devices, the rapid diffusion in the industry, nearly 20 iron and steel enterprises in Baotou Steel, Laiwu Steel, TISCO, Shagang built of CCPP.
In addition, the saturated steam power generation, regenerative reheating furnace to burn low calorific value of blast furnace gas, billet hot charging, blast furnace red residue water waste heat utilization, converter to vaporization cooling steam Supplying RH and other widely used technology in the industry, coal tune wet technology, coke oven rise pipe waste heat recovery, thermal conductivity of oil Ammonia technology breakthrough.
Gas loss rate year by year. In recent years, the blast furnace, coke oven, BOF gas utilization has gradually increased and the loss rate year by year. Compared with 2006, 2010, the coke oven gas loss rate lower by 0.96 percentage points, blast furnace gas loss rate reduced by 2.65 percentage points, converter gas loss rate reduced by 11.25 percentage points.
Since the power ratio continues to increase. Iron and steel industry waste heat and energy utilization level and since the power ratio of continuous improvement, since the proportion of electricity generation increased from 21.6% in 2006 to 31.9 percent in 2010 to 10.3 percent. Handan Iron & Steel, Tangshan Iron and Steel and other companies since generating more than 70%.
Traditional recovery issues to be resolved
Although the residual heat of the iron and steel industry in recent years can take advantage of some success, but the waste heat and energy itself has a scattered layout and uneven quality features, resulting in the recycling of energy there are certain problems in the traditional way. Total secondary energy production is always greater than the consumption, energy demand and supply do not match in a certain extent. At present, the residual heat of the iron and steel industry can take advantage of the prevalence of the following questions:
First, often the emphasis on recycling of waste heat and energy and neglects the use efficiency, resulting in a serious invalid recovery. Such as the recycling of the product gas pressure after gas dust removal facilities and gas transmission and distribution facilities, consume a certain cost, such as recycled gas did not find the right users and diffuse, and this is a serious invalid recovery phenomenon.
Second, traditional energy recycling commonly used long-distance transmission, resulting in flow propagation in high energy consumption and transmission loss. Such as long-distance transmission of low-temperature saturated steam, will cause a lot of heat loss, not only wasted energy recovery, will result in the formation of a new loss of soft water loss.
Steam system is not used efficiently. Iron and steel enterprises that currently prevails steam a large number of diffuse phenomenon, especially in summer, a lot of recycling space; At the same time, often thermoelectric with Pressure Reducer for the steam pipe network, the intermediate links without any external acting process, energy depreciation very large.
The fourth part of the energy-consuming equipment media unreasonable, did not do the level matching and temperature counterparts. Some enterprises lack a unified energy management and economic adjustment measures, making the energy processes have to compete for high-quality energy, often end up causing a high-energy low with low energy efficiency, from a global perspective.
Address the challenges of the new situation
The steel industry is faced with new developments, the waste heat and energy use is also facing new challenges.
The gas loss to be further reduced. Although the gas emission rate of the steel industry is declining, but still too large to lead to the absolute amount of gas loss due to increased scale of production, the product gas use energy-saving potential has yet to fully play out. This has brought new challenges to the iron and steel industry energy conservation, depending on the gas resources quantity, quality and user needs, rational distribution and use of gas, perfect gas buffer system to further reduce the emission loss rate of the gas.
Gas use to be a fundamental shift. With the era of low-carbon economy, the traditional business of waste heat and energy conversion of a single use of electricity will be faced with restructuring, comprehensive utilization will further improve the energy efficiency of key resources - energy - recycling ". Coke oven gas as a quality secondary energy can produce hydrogen, methanol, dimethyl ether, etc., to be a mature technology, direct injection into the blast furnace, the use of H2 and CH4 in the coke oven gas, blast furnace smelting, and ultimately carbon utilization of high-carbon energy.
The thermoelectric conversion efficiency is further improved.
Thermoelectric units of major companies should be gradually to high temperature and pressure parameters of unit, the memory industry, a considerable number of temperature and pressure units, hindering further increases in efficiency of energy conversion. Enterprises should be combined with their own development planning, integrated out of small units, the construction of large, high-parameter generator sets will be able to more substantial increase in the level of self-generating.
To further deepen and expand low-temperature waste heat utilization. Steel, high-temperature waste heat has basically recovered in the low temperature and parameters of heat and comprehensive utilization of resources become the key to further tap the energy-saving potential, including the blast furnace red residue water waste heat, steam turbine cooling water waste heat, coke and the beginning of cold water waste heat, although the temperature is low, But the total resources is considerable. Energy-saving workers should be based on the concept of distributed energy cascade utilization, and improve the quality of waste heat, the construction of a regional style of certain economies of scale heat utilization system; focus on the utilization of waste heat of the expanded function, the waste heat for seawater desalination, sludge treatment.
A harmonious and Urban Development. Iron and steel enterprises has been shown to high energy consumption and emission image, the face of new energy saving and emission reduction situation, iron and steel enterprises should strive to promote the green transformation, and strive to become an integral part of urban development and harmonious urban development. I can use the waste heat of the iron and steel enterprises as the core build metallurgical furnaces - the byproduct gas - a common fire - power back for metallurgical furnaces - low-temperature cooling water - urban heating water recycling economy industrial chain, and reached with the social large circulation, and the true circular economy.
Policies and measures to further improve. The final form of waste heat and energy use for the recovery of power, China's current power generation Internet there is a certain policy barriers, such as grid-approval difficulties, many over the net costs, impacts and limit the iron and steel enterprises to use the waste heat and energy of enthusiasm. This gives policy makers the challenge to develop reasonable policies and the price system of the iron and steel enterprises power and network (Internet), to encourage steel mills using waste heat and energy to build the power plant, residual heat utilization project to further increase the financial incentives .
Further improve the energy efficiency services market mechanism. The energy efficiency of major energy-saving measures in the iron and steel enterprises has been generally built with, but some small energy-saving projects to promote the existence of certain obstacles. This is mainly because of the type of the project's payback period is relatively long, the energy efficiency relatively obvious, is reluctant to spend money and manpower during the operating difficulties. At this point, we shall give full play to the advantages of energy efficiency services market, and contract energy management approach to solve the problem of enterprise technology, capital, operation and management, to achieve win-win.
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