Negative energy steelmaking and gas recovery techn

Converter negative energy steelmaking and gas recovery technology

1 negative energy steelmaking can be achieved by the energy consumption of converter steelmaking process

in the converter, the process of turning molten iron into steel is mainly high-temperature physical and chemical reaction processes such as carbon reduction, temperature rise, dephosphorization, desulfurization, deoxidation and alloying. Its technical operation is to control oxygen supply, slag making, temperature and alloy addition, so as to obtain the required liquid steel and cast it into steel ingot or continuous casting billet. One of the characteristics of oxygen top blowing converter steelmaking method is that it does not need external heat sources. According to the calculation of material and heat balance, the physical heat and chemical heat of molten iron are the main heat income, which offset the heat content of metal and slag and various heat losses, as well as the residual heat. Therefore, scrap steel, iron ore and limestone are often added into the furnace as coolant to balance the heat and prevent the furnace temperature from being too high

1.1 energy consumption of steel-making process

the steel-making process can be completed only with sufficient energy input, which usually consumes electricity, oxygen, gas, inert gas, condensed air, water, steam, etc. Taking Baosteel Phase I project as an example, see Table 1 for details

1.2 energy release in steelmaking process

electronic universal experimental machine in the testing industry, carbon oxygen reaction is an important reaction that always exists in the smelting process. The product of the reaction is mainly C0 gas (the concentration is about 85%~90% of 30 national enterprise technology centers), but a small amount of carbon and oxygen directly interact to generate CO2, Its chemical reaction formula is

2c+o2 2co

2c+2o2 2co2

2co+o2 2co2

in the smelting process, the furnace is at high temperature, and the CO gas formed by carbon oxygen reaction is also called converter gas, and the temperature is about 1600 ℃. At this time, the energy of high-temperature converter gas is about 1gj/t, of which the sensible heat energy of gas accounts for about 1/5, and the remaining 4/5 is potential (converted into heat energy when burning, and chemical energy when not burning), which is the main energy released in the converter smelting process. Therefore, the recovery and utilization of converter gas is an important way to save energy and reduce consumption in steelmaking. See Figure 1 for the self balance of oxygen top blowing converter steelmaking process

1.3 negative analysis of energy consumption in steel-making process

energy consumption in steel-making process is calculated by deducting the corresponding recovered energy (standard coal) from the sum of various energies used to produce a ton of qualified products (ingots or continuous casting billets)

when consuming energy to recover energy, the energy consumption is positive

when consuming energy - recovering energy =0 (called zero energy steelmaking)

when consuming energy to recover energy, the energy consumption is negative (called negative energy steelmaking)

1 It is estimated that the annual compound growth rate of domestic BDO capacity in 2014 (2) and 2016 will reach 37% 4. It is possible to realize negative energy steelmaking

the energy released during converter steelmaking is carried by high-temperature gas. If measured and analyzed by thermal energy, the specific performance is that latent heat accounts for 83.6% and sensible heat accounts for 16.4%. See Figure 3 for details. Obviously, the energy of gas accounts for the vast majority of the total heat. Figure 2 also shows the role of recovered gas in reducing energy consumption in the steelmaking process. Therefore, to achieve negative energy steelmaking, gas must be recovered, and the quantity and quality of recovered gas should be improved as much as possible

see Table 2 for the recovery part of the process energy consumption calculation of Baosteel Phase I project. Baosteel designed to produce 3.18 million tons of molten steel, 3.12 million tons of ingots and 1 iron steel ratio in phase I. combined with table 1 and table 2, the design value of energy consumption in Baosteel's phase I process is

(8..822) 312=6kg/t

Baosteel scientifically applied measures such as target management and improvement of labor skills in 1989. The energy consumption per ton of steel decreased by 4.31kg, making the energy consumption of converter process reach -1.05kg/t, as shown in Table 3. It has achieved negative energy steelmaking and entered the ranks of the world's advanced steelmaking technology

under the action of mechanical force, degradable material products are produced by extrusion, molding, blow molding or injection molding with appropriate molds. 1.5 to realize negative energy steelmaking in converter, gas must be recovered.

1.6 the main technical ways to realize negative energy steelmaking.

(1) adopt new technology system integration to improve the quality and quantity of gas recovery

(2) adopt the new technology of AC variable frequency speed regulation to reduce the power consumption of high-power motors in the steelmaking process

(3) improve the operation level of steelmaking (including continuous casting) and reduce material and fuel consumption

(4) improve the management level and personnel quality to ensure safe, normal and stable production

2 the current situation of domestic converter gas recovery technology and its great potential for energy saving

2.1 the main representative process of converter gas purification and recovery

China first realized gas recovery on a 30t converter in the first plant of Shanghai Iron and Steel Corporation in 1966. It is a wet process, abbreviated as og method. It mainly adopts two-stage venturi gas precipitator, and the gas storage is a wet gas holder. So far, all enterprises that have recovered gas in China are wet processes (Figure 4). This process has low capital technology, simple and safe operation, but the operation cost is relatively high, so dust removal and sewage treatment facilities should be attached

another dry process, called LT process for short (Figure 5), is a gas recovery unit built by introducing VAI technology into Baosteel's phase III 250t converter. Dry electrostatic precipitator is used for converter gas purification, and dry gas holder is used for gas storage. This process has high capital investment, low operation cost, complex operation, and no sewage treatment facilities. It will be put into operation at the same time with Baosteel 250t converter

2.2 comparison between China's converter gas recovery technology level and foreign advanced level (see table 5-6)

in 1986, three 30t converters in the third plant of Shanghai Iron and Steel Co., Ltd. adopted relatively complete sets of domestic gas recovery technology and equipment, mainly including: ① linear rectangular adjustable throat venturi dust collector; ② Adjustable throat hydraulic servo device; ③ Automatic regulation system of micro differential pressure at furnace mouth; ④ Quick three-way switching valve; ⑤ Large diameter venturi gas flowmeter; ⑥ Automatic control device for gas recovery; ⑦ Automatic analysis device of gas composition

2.3 the energy-saving potential of recovered gas is huge

it has been 30 years since China began to recover converter gas in 1966. By 1996, 20 enterprises had recovered gas (Table 4), accounting for 51% of the enterprises that should recover gas. The average recycling rate of converter gas in the whole industry is 51%, that of key steel enterprises is 70%, and that of small and medium-sized backbone enterprises is only 6%. If the 19 enterprises that have not recovered gas at present add recovery facilities as soon as possible and adopt new technology and equipment, the initial recovery will be based on the medium level requirements, that is, 65m3 per ton of steel will be recovered, and the calorific value of gas will be 18004.18kj/m3. The annual recovery of gas equivalent to standard coal can reach 340000 tons. The 17 enterprises that have achieved low-level recycling have carried out technological transformation with new technology to raise the recycling level to a higher level, that is, 70m3 per ton of steel is recycled, and the calorific value of gas is 1950.4 kj/m3, so the annual additional recovered gas can be converted into standard coal of 160000 tons. The sum of the above two will achieve an annual energy recovery of about 400000 tons. The energy consumption (standard coal) of the converter steelmaking process of the above 36 enterprises will decrease by an average of 9.2kg/t, and the energy-saving potential is huge

converter negative energy steelmaking is one of the important symbols of advanced steelmaking technology, the comprehensive embodiment of the advanced level of steelmaking process, equipment, operation and management, and the main technical measures to save energy, reduce consumption, reduce production costs and improve the competitiveness of enterprises. Realizing negative energy steelmaking is also a difficult scientific and technological breakthrough system project, which requires the integration and matching of many advanced technologies, especially the modern scientific management and production of enterprises. We must do everything possible to improve the quantity and quality of converter gas recovery