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Why iron and steel industry calls for waste heat recovery

Release date：2018-01-19

The utilization of resources in the iron and steel industry is low, and a large amount of energy loss can not be fully utilized, resulting in a large amount of loss.

How to make full use of resources in today's competitive society is particularly important. Hefei ENT energy conservation research and development center has made a detailed analysis of the energy use distribution in the steel industry and put forward the optimization solution.

1. Waste heat of sinter line

The sintering production line has two parts of waste heat, one is the hot air produced by the cooling machine and the two is the high temperature flue gas at the end of the sintering machine. The residual heat of the two parts is generated by the waste heat boiler, and then the steam turbine is generated by the steam turbine. According to the experience data, the sintered area per 10m2 can produce 1.5t/h steam, which can generate 300kW and the 120kg/h of the standard coal.

2. Waste heat of converter

The steam generated by converter vaporization cooling flue is changed into a continuous saturated steam through accumulator. Every 1t steel can produce 80kg saturated steam, and the saturated steam per ton can generate 150kWh, which is equivalent to 60kg of standard coal.

Converter gas after gasification cooling flue after cooling temperature is up to 800 ~ 900 DEG C, after Hefei ENT energy R & D center to a factory design example showed that the use of our design, through the drop tube flue, quench heat exchanger heat recovery steam production, how to use according to your requirements.

3. Waste heat of electric furnace

During the smelting process of the electric furnace, the high temperature dust gas is produced at 200~1000 C, and the waste heat boiler is used to recover the waste gas.

4. Waste heat of heating furnace

There are two residual heat in the furnace: one is the vaporization cooling system of the supporting beam in the furnace and the other is the flue gas of the flue. According to the different furnace types, the flue gas volume of the heating furnace is 7000 ~ 300000Nm3/h. If it is used to generate electricity, the flue gas volume is 100 thousand Nm3, and the flue gas temperature is 400 degrees. The electricity output is about 2000kWh, which is equivalent to the standard coal 0.8t. The vaporization cooling system can be produced.

0.4~1.0Mpa saturated steam, a ton of steam (0.5Mpa) can generate 120kWh, the same as the standard coal 48kg.

5, blast furnace slag water

A large amount of slag and hot water will be produced in the process of rapid cooling and granulation of the slag with high speed water flow. Each ton of iron is discharged about 0.3T slag. Every ton of slag can produce 80~95 degrees of temperature and 5 to 10t of slag water. This part of the hot water will be decompressed to produce low pressure steam and then enter the saturated steam condensing steam turbine to generate electricity. Hot water at 90 degrees centigrade per ton can generate 1.5kWh, 0.6kg of standard coal and 1kWh for hot water at 80 C, 0.4KG of standard coal.

Significance of waste heat recovery in iron and steel industry

The iron and steel industry is the focus of China's energy consumption, energy consumption accounted for about 15% of national energy consumption, iron and steel production process, process, and the high temperature smelting and processing, produce a lot of heat energy in the production process, it mainly comes from the sintering machine flue gas sensible heat, red coke sensible heat, converter the flue gas heating furnace and the heat recovery device, a variety of waste heat resources accounted for about 68% of production energy consumption, in the current energy above 2/3 steel production process is to exhaust gas and waste residue and waste heat consumption in the form of products.

With the universally recognized social and energy saving benefits generated by the technology of waste heat recovery, the technology of waste heat recovery has been widely applied in domestic iron and steel enterprises. Hefei ENT energy conservation research and development center technology, the design of the scheme has been very mature, now concentrating on further improving the efficiency of waste heat recovery.

Sinter Plant Heat Recovery

With good returns the value of the sintering waste heat refers to the waste heat generated in the cooling machine front is cooled by air exhaust gas and hot sinter discharged from the sintering machine tail bellows after the temperature can reach 300-400 degrees Celsius, the two part of the waste heat and the heat of sintering ore accounted for the entire energy consumption of around 23%-28%, has the characteristics of high temperature the large number of stable operation, is the key of sintering process energy saving and recycling.

The domestic iron and steel enterprises mostly use the sintering waste heat to fuel air, preheat mixture or use waste heat recovery unit to produce steam, and the efficiency of recycling is not high. In particular, with the large-scale sintering machine at the present stage, the traditional way of waste heat utilization is unable to make full use of the waste heat resources to maximize the benefit. Therefore, from the perspective of the efficiency and economy of the energy cascade utilization, how to make use of the waste heat to achieve the most economical. Hefei ENT energy conservation research and development center has shown that it needs to be determined according to the characteristics of the region and the enterprise.

In the total energy consumption of the sintering process, nearly 50% of the heat energy is discharged into the atmosphere in the form of the explicit heat of the flue gas and the exhaust gas of the cooler. Because the temperature of the exhaust gas of the sintering cooler is not high, only 150~450 C and the limitation of the waste heat recovery technology, the waste heat recovery project is often ignored. The recovery of the waste heat of the sintering cooler is to recover the low taste waste heat energy by recovering the waste heat boiler of the tail gas of the sintering machine tail and the flue gas heated by the closed cooling section.

From the angle of energy utilization, the heat energy of about 24% of the original production line is discharged into the atmosphere with the exhaust gas, which not only causes the waste of energy, but also produces the greenhouse effect. It is not conducive to the development of the needs of all aspects.

In addition to the above waste heat resources, a lot of low pressure saturated steam is produced in steelmaking and rolling processes during the production process of iron and steel enterprises. According to the production system, it is divided into intermittent steam and relative continuous steam, which has relatively low utilization value compared with coking and sintering processes.

Discontinuous steam, this part mainly refers to the afterheat steam produced in the steelmaking process. In the process of converter blowing, a large number of high temperature flue gas above 1200 degrees Celsius is generated, which can reduce flue gas temperature and recover residual heat in high temperature flue gas, and create conditions for converter gas dedusting machine gas recovery. It can be treated with air source heat pump, which is economical and economical.

The production of saturated steam in iron and steel enterprises is large, but the utilization efficiency is low, especially in the iron and steel plants in most areas in the south which are not heating in winter. The air source heat pump can be used, not only to supply hot water and temperature, but also to save resources. Produce new benefits.

In the process of ironmaking in the blast furnace, the slag temperature is about 1000 degrees Celsius, and the slag is flushing.

The high-speed water slag box provided by slag flushing pump cooling water into slag and granulated, this process can produce a large number of temperature at low temperature 80-95 degrees Celsius hot water, hot water volume reached thousands of tons / hour, long-term emissions not only a waste of energy, but also caused the loss of environmental pollution and water resource. Therefore, the trend of energy-saving transformation and transformation is unstoppable, but how to achieve the best effect, the Hefei ENT energy conservation research and development center will discuss with you for your plan.