INTERNATIONAL JOURNAL OF ENERGY RESEARCH
Int.J.Energy Res.,22,1049—1054(1998)
ENERGY ANALYSIS OF THE STEEL MAKING INDUSTRY
思想工作情况汇报MOUSA S.MOHSEN*AND BILAL A.AKASH
Department of Mechanical&Industrial Engineering,Applied Science Uni v ersity,Amman,11931,Jordan
SUMMARY
婴儿红疹Steel making is an energy intensive industry.This work prents and identifies heat loss of the main components of this industry in Jordan.The heat loss are considerable and range from17to36%of the total energy input.Some heat loss are considered to be recoverable,especially in the furnace and the crucible and mould.Specific energy consumption was found to be6)0MJ per ton of steel for the Jordanian steel industry. 1998John Wiley&Sons,Ltd.
KEY WORDS energy in steel industry;electric arc furnace;SEC
INTRODUCTION
Steel making involves different cycles such as heating,cooling,melting and solidification.It is a highly energy intensive industry.The reduction of energy consumption in this kind of industry is of a special concern.The specific energy consumption(SEC)of steel plants for different countries was reported in literature(Bhak-tavatsalam and Choudhury,1995,Choudhury and Bhaktavatsalam,1997).In general,energy savings can be achieved by cutting down direct energy consumption,increasing energy recovery,and adopting the policy of replacing oil products and natural gas in primary steel making with coal and coal-by-products.According to Perlov(1987),increasing the energy efficiency of the most consuming facilities is achieved by improving the u of condary energy sources such as minimizing the heat lost in hot waste gas,minimizing the heat radiated through refractory linings of metallurgical furnaces,and cooling the highly thermally stresd components.
ALTERNATIVE TECHNOLOGIES AND ENERGY CONSERVATION
In a recent study it was reported that the developments in iron and steel making took two parate lines (Zervas et al.,1996).Thefirst line was concerned with the blast furnace as the principal process for production,and the cond was bad on the direct reduction and smelting in which iron oxide feedstocks were reduced by gas to metallic iron.The different technologies are summarized in Figure1.
Energy consumption in the different stages of steel production is about70%for iron and steel production, 20%for rolling,and10%for miscellaneous(Eketorp,1987).Therefore,the primary step is the main energy consumer in steel making,and most efforts have been directed towards the blast furnace.Energy efficiency in the blast furnace can be improved by improving iron-ore benefaction,removing rawfluxes from the blast furnace burden,reducing the ash content of coke,reducing the sulphur content of coke and iron-ore materials,reducing the output fraction of cast iron and ferroalloys,using larger fractions of partly reduced *Correspondence to:Dr.M.S.Mohn,Department of Mechanical&Industrial Engineering,Applied Science University,Amman, 11931,Jordan.Email:jo
CCC0363-907X/98/121049—06$17.50Recei v ed9February1998
Figure 1.Summary of different technologies
metallized raw materials,improving the blending,classification and mechanical strength of iron-ore raw material,increasing the internal pressure in the blast furnace,increasing the blast temperature,and introducing external desulphurization.The scrap charging electric arc furnace (EAF)route of steel making requires considerably less energy than the integrated route.It has been reported,that EAF route is en to be 40%less energy intensive than the open hearth furnace (OHF)route and less than 50%as energy intensive as the basic oxygen furnace (BOF)route (Lyakishev and Perlov,1987).It has been shown that as the percentage of scrap in the charge increas,the energy efficiency of the BOF and OHF will increa,since about 90%of the total energy u is associated with the smelting of pig iron.
World-wide steel plants switched over to BOF route from OHF route of steel making due to energy conrvation considerations.Also,the ingot casting route was replaced by the continuous casting technology (Bhaktavatsalam and Choudhury,1995).马云的励志故事简短
THE SCRAP CHARGE EAF ROUTE
The EAF is widely ud in many countries for refining the quality of steel for industry.The technologies ud in steel making in different countries are summarized in Figure 2(Bhaktavatsalam
and Choudhury,1995).The scrap-bad EAF route of steel production required less energy than the integrated route.Ross (1987)reported that melting involves the transfer of 1)1MBtu to each ton of scrap (1)16GJ ton \ ),and in average practice about 2)4MBtu is consumed per ton of liquid steel (2)53GJ ton \ ).For example,the scrap remelting is playing an important role of reducing energy consumption in steel making industry in Italy,it was reported that the production of new steel requires about 18GJ ton \ of liquid steel,while the production of remelted steel from scrap requires 6)5GJ ton \ of liquid steel (Bisio,1993).The theor-etical quantity of heat necessary to melt the scrap and to bring the steel to the tapping temperature is about 345kW h ton \ (Scotti,1990).Although,in practice,the amount needed is higher due to non-homogeneity of the scrap,heat is lost during charging pha of the scrap.Heat is also lost through the fettlings,the walls and the water-cooling crown,the outlet of hot gas from the clefts of the crown,and reactance of the electric furnace and conquent lower exploitation of the active energy and increa of electric loss.
车险全险包括什么1050M.S.MOHSEN AND B.A.AKASH
ENERGY ANALYSIS OF THE STEEL MAKING INDUSTRY1051
三毛片Figure2.Routes ud in steel making in different countries
The main measures for saving energy in the EAF steel making are:recovery of heat from offgas with its u to preheat scrap,using oxygen,increasing the voltage of the transformer,installing electrodes with protective coatings,reducing furnace downtimes,automatic controls for the voltage and power factor,and for the position of the electrodes,water cooling of the sides and insulation,and i
ncreasing the volume of metal treated in the ladle.
The production of liquid steel in the electric furnace absorbs the highest proportion of the total energy consumption in the scrap charge EAF route.A proportion of67%has been reported(Poggi,1990).
A mathematical model which integrates the electrical model with the thermal model has been developed for the performance of an electric arc furnace(Chirattananon and Gao,1996).The influence of operational parameters on the overall energy performance and productivity of an arc furnace operation has been demonstrated.
The most prominent change in shaping technology is the continuous casting since it offers important benefits in product quality for most products becau of its uniformity and reduction of defects during solidification.Continuous castings has large immediate energy benefits.It was reported that the direct savings are about1688MJ ton\ of rough shaped steel(Ross1987).About0)17ton more liquid steel per ton of shaped steel is required with the ingot casting than for continuos casting.The savings due to this requirement are about3060MJ ton\ of rough shaped steel.
Energy can be saved in the hot rolling stage,in current practice,almost4220MJ ton\ of hot rolled prod
uct is ud for reheating(Ross,1987).Improvements in the reheat furnace through automatic control bad on nsing the surface temperatures of the slab and parately controlling different zones of the furnace heat recovery including waste heat boilers,improved insulated water-cooled skids,and improvements in the envelope will reduce energy consumption.
STEEL INDUSTRY IN JORDAN
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The steel making industry in Jordan is bad on recycling of iron and steel.It involves melting of scrap in the electric furnace.This type of process takes place as a result of the electric arc which is generated between
the electrode and the scrap.As an example,the Jordanian Iron &Steel Industry Co.facility plant has been investigated and analyd.The 120ton-per-day capacity production line consists mainly of the smelting by EAF and the shaping part.Block diagrams of the production line are shown in Figures 3and 4.Electricity is primarily ud to operate the rolling mill and electric arc furnace.The electric arc furnace us 700kW h ton \ to melt the scrap,which consists of about 62%of the total energy consumption.The energy content of each stream entering and leaving the unit in the smelting ction,was calculated from the appropriate site of measurement.Magnitudes of all heat loss were
calculated and prented in Figures 5—7.Bad on energy balance of each unit,it is found that 914MJ ton \ (36%of total heat input)are lost in the furnace.Heat loss in the crucible and mould add up to 439MJ ton \ (17%of total heat input).On the other hand,651MJ ton \ is lost in the cooler (26%of total heat input).Recovery of the heat content of the cooling water can be accomplished by steam generation and preheating the scrap.From heat content difference in the cooler,the initial temperature of the scrap can be raid approximately to about 800°C.The shaping involves casting the liquid steel into rough shapes,then the rough shapes are reheated and rolled into reinforcement steel bars.The casting,reheating furnace and rolling mills for steel rods absorb approximately 65%of the total energy consumption of the production line as shown in Table 1.The energy consumption of this stage is 70kW h ton \ (0)25GJ ton \ )of electricity and 70)5kg of fuel oil per each ton of steel (3)00GJ ton \ ).
SEC of the Jordanian steel making industry is thus obtained by the procedure described by Choudhury and Bhaktavatsalam (1997).It is found to be equal to 6.0GJ ton \ of steel.It is prented in Figure 8as compared to SEC of other countries.It is lower than tho values of other countries,since steel industry in Jordan is bad on remelting or recycling of scrap.However,steel making in other countries prented in Table 1is bad from manufacturing of steel from raw materials.Therefore,energy consumption and thus,SEC is lower for Jordanian steel making
industry.
Figure 3.Block diagram of scrap-bad EAF
route.
动词不定式的用法总结Figure 4.Block diagram of temperature distribution of EAF
route
Figure 5.Energy balance in
EAF
Figure 6.Energy balance in crucible and mould 1052M.S.MOHSEN AND B.A.AKASH
Figure 7.Energy balance in cooler
Table 1.Energy consumption (GJ ton steel \ )
Electricity
Fuel oil Gas oil Total EAF
2)52——2)52Casting,reheating furnace and
0)253)000)053)25rolling mill
Others
0)18——0)18Total 2)953)000)056)
00
Figure 8.Specific energy consumption
CONCLUSION
Heat loss occur along the line of production of the steel making industry.About 36%of total heat input is lost in the furnace.This is a recoverable heat which should not be wasted.17%of total heat input is lost in the crucible and mould.Some of it can be recovered or ud in processing of steam.Over 26%of heat is rejected in the cooler.The recovery of heat of last process could be difficult to achieve,except for space heating or ENERGY ANALYSIS OF THE STEEL MAKING INDUSTRY 1053
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