Improving the Performance of the Roasting Machines at AO SSGPO

Transcription

1 ISSN , Steel in Translation, 2008, Vol. 38, No. 5, pp Allerton Press, Inc., Original Russian Text A.A. Butkarev, A.P. Butkarev, V.N. Ashcheulov, P.A. Zhomiruk, V.V. Martynenko, 2008, published in Stal, 2008, No. 5, pp Improving the Performance of the Roasting Machines at AO SSGPO A. A. Butkarev, A. P. Butkarev, V. N. Ashcheulov, P. A. Zhomiruk, and V. V. Martynenko OAO VNIIMT OAO SSGPO DOI: /S To permit more efficient production of iron-ore pellets, AO SSGPO has considered various reorganization proposals. The proposal of OAO VNIIMT (Yekaterinburg) was adopted, including study of the technology and equipment, the development of an optimal heating system, the design and automation of roasting machines, the manufacture and supply of economical injection burners, and inspection and adjustment of the new technology on introduction. With minimum expenditures and maximum utilization of existing equipment, the OAO VNIIMT proposal increases the productivity by 24.6%, reduces natural-gas consumption by 56.3%, and reduces power consumption in the blower drives by 21.3%. These results are made possible by OAO VNIIMT s methodology for developing heating systems in roasting machines, based on the mathematical models and approaches in [1 3]. These measures significantly reduce energy consumption and increase the productivity of the equipment. As an example, consider the application of this methodology to AO SSGPO s roasting machine 5. Machine 5, which went into operation in 1964, is an OK-108/116 conveyer roasting machine. It was one of the first such machines in the Soviet Union. Its characteristics are as follows: it has no collector for transporting high-temperature gases from the cooling zone to the heating zone; 30 double-line turbulent burners are employed, rather than economical injection burners; hot air from the cooling zone is diluted to a temperature permitting its transportation by the existing draft unit (below 400 C), with corresponding increase in fuel and power consumption and emissions; the high maximum pellet temperature at discharge (mean temperature 350 C, maximum temperature 600 C) complicates its transportation and use in the blast furnace and increases fuel costs; thanks to ineffective sealing of the gas air chambers and lack of sealing in the hearth, pellet quality is unstable on account of air suction into the hearth of the roasting machines, copious gas flows for heat treatment, and consequently waste of fuel and power and overloading of the flues that carry gas to the smokestack; the relatively small width of the roasting truck (2 m) impairs performance relative to machines with a width of 3 4 m, mainly on account of the greater gas leakage; the equipment is very worn and out of date; sulfur compounds are present in the raw materials; the automatic systems are out of date. (They have not been modernized since they went into operation.) The heating system of roasting machine 5 is analogous to that described in [4]: useful area 116 m 2 ; 29 gas air chambers, with seven draft units (D1 D7); roasting truck of width 2 m; pellet output 99.5 t/h or 0.86 t/m 2 h. To develop integrated measures for improving the productivity of the unit and considerably reducing energy costs, the operation of roasting machine 5 is studied, with appropriate measurements. Then the operational efficiency of the technological zones is estimated, and their relative areas and operating parameters are optimized by means of mathematical models, using the method in [1]. According to the classification in [1], the heating system of machine 5 must comply with general requirements: reversible drying (injection/suction), a directflow system; injection burners; and an irreversible cooling system based on cold (atmospheric) air. Customized design solutions are derived analogously to the procedures in [5, 6]. It is found that the direct-flow system must include a single flux (fluxed pellets of basicity 1.1). The pellets must be cooled by cold (atmospheric) air. According to the data in [1], the heating system does not include inefficient processes whose use is not recommended: drying of the layer with suction of the hot gas; laminar pellet charging, with intermediate drying by suction of the hot gas; a fan transfer system with dilution of the heat carrier; two-line burners; or reversing of the coolant on cooling, cooling in external coolant, or cooling by hot air (up to 300 C) in the first stage. 378

2 IMPROVING THE PERFORMANCE OF THE ROASTING MACHINES AT AO SSGPO 379 In synthesis of the heating systems, it is established that, since the initial material contains sulfur, it is inexpedient to send the hot gas from the roasting and recuperation zones to the drying zone. Therefore, the hot gas for drying must be supplied from cooling section 2. Thus, the optimal structure of the heating system is structure 2 in [1]. Then, on the basis of the research data for roasting machine 5, the optimal design and operating parameters are determined, including the pressure in the gas air chambers and their distribution; the temperature of the coolant (heat carrier) on entering the bed and its distribution over the length of the technological zones; the temperature and consumption of the air used for combustion and dilution (in the fuel-combustion zones); the useful area of the roasting machine and its distribution by zones; and the height of the pellet bed and the base areas. Calculations yield a modernized heating system for the OK-124 roasting machine, as shown in the figure, and permit the determination of its basic characteristics. In this system, the following operations permit increase in productivity, decrease in energy consumption, and reduction in environmental impact: increase in useful area of the machine (cooling zone) by 8 mm 2 (two gas air chambers); introduction of a flow line for transmitting hot air ( C) from the cooling zone to drying zone 2 and for heating and roasting by the direct flow without the need for a draft unit or dilution by atmospheric air; replacement of the two-line turbulent burners by more economical OAO VNIIMT injection burners (above gas air chambers 11 17); and replacement of the existing extraction pumps D1 and D2 (of type D21.5 2U) by a single more productive and economical pump (GD-26 2), with convergence of the two lines to one; boosting of the D4 fan channel by connecting free fan D6 of GD type; modernization of the D7 fan channel (increase in diameter of the suction line from 1.6 to 2.4 m; installation of a suction guide system, and modification of the fan rotor [4]); division of the line in the D7 fan channel into two: L4 (gas air chambers 21 24) and L5 (gas air chambers 25 31), served by fans D8 and D7, respectively; introduction of additional fan D8 (of type VVN- 18K), for cooling the pellets; two additional low-speed fans (D9 and the backup D9') to supply air for combustion to the injection burners; barriers in the hearth between gas air chambers 5 and 6, 18 and 19, and 28 and 29, respectively; side seals between the hearth and pellet trucks; gas purification in all the internal and discharge gas fluxes; and correction and refinement of the operating temperature and aerodynamic conditions; integrated automation of the process. These measures enhance the performance of the machine: Characteristic Productivity of roasting machine, t/h (%) Natural-gas consumption, m 3 /t (%) Power consumption at draft unit, kw-h/t (%) Existing unit (OK-116) The new heating system may be analyzed on the basis of data in [2]. The nonoptimal elements are identified, and the remaining scope for improvement in performance is estimated. The nonoptimal components are due to the use of the existing draft units, difficulty in siting the additional equipment, minimization of the modernization expenses, and other factors. As a result, the following principles have been violated [2]: principle 7.2: elimination of gas purification in the internal lines by introducing fans resistant to abrasive wear (with protection of the rotor) in the D3 and D5 channels [2]. Compliance with this principle entails replacement of fans D5 and D3 by a single fan, with protection of the rotor against dust abrasion; principle 11.1: elimination of gas flows from the hearth and aspirational units to the high-pressure fans sucking gas from the gas air chambers [2]. To implement this principle by evacuation of gas from the dome of drying section 1, it is expedient to use a single lowpressure (up to 3 kpa) fan. This permits additional power savings, reduction in the load in the D1 channel, and increase in productivity of the heating zones. These measures not only reduce natural-gas consumption and increase productivity but also reduce power consumption by as much as 2.35 kw-h/t. CONCLUSIONS After modernization (OK-124) Improvement (24.6) ( ) (21.3) The modernization of the heating system for roasting machine 5 at AO SSGPO, with specified pellet quality, increases the productivity by 24.5 t/h (24.6%), reduces the natural-gas consumption by 56.3% (19.3 m 3 /t), and reduces fan power consumption by 9.9 kw-h/t (21.3%). Thus, with improvement of the heating system and modernization of the OK-108/116 roasting machines, their performance approaches current global levels. STEEL IN TRANSLATION Vol. 38 No

3 380 BUTKAREV et al. Air Natural gas D9' D9 Ch2 Ch5 D3 GS 3 D5 GS 5 AU 70 Ch5 Ch4 Ch6 DGP3 Ch7 Ch Drying 1 Drying 2 Heating 1 Heating 2 Heating 3 Roasting 1 Roasting 2 Recuperation Cooling 1 Cooling AU 69 K2 K2 K3 K4 K5 To flue GS1 DGP2 Ch10 D1 GD 26 2 To flue Ch9 DGP2 Ch8 GS4 D6 D8 D7 GS6 GS8 GS7 D4 VVN-18K VM 160/850 U Heating system for AO SSGPO OK-124 roasting machine 5 after modernization by OA VNIIMT: D, draft unit; GS, guide system of draft unit; DGP, dry gas purification; ) burner; ) burner aperture; AU, aspiration unit; Ch, choke. Currently, the heating system of roasting machine 5 is being modernized at AO SSGPO. REFERENCES 1. Butkarev, A.A., Methodology for Integrated Study and Optimization of the Heating Systems in Conveyer Roasting Machines, Stal, 2008, no. 4, pp Butkarev, A.A., Design of Optimal (Energy-Efficient) Heating Systems of Roasting Machines, Stal, 2007, no. 9, pp Butkarev, A.A. and Butkarev, A.P., Determining the Parameters of Pellet Heat Treatment on Conveyer Machines, Stal, 2000, no. 4, pp Butkarev, A.A., Butkarev, A.P., Ashcheulov, V.N., et al., Optimizing the Parameters of Roasting Machines 1 8 at AO SSGPO, Stal, 2007, no. 12, pp Butkarev, A.A. and Butkarev, A.P., Optimizing the Parameters of the Flow System in Conveyer Roasting Machines, Stal, 2005, no 3, pp Butkarev, A.A., Butkarev, A.P., and Zhilin, S.N., Efficient Utilization of Hot Gases in Cooling Pellets in Conveyer Roasting Machines, Stal, 2005, no. 3, pp STEEL IN TRANSLATION Vol. 38 No

4 Open Joint Stock Company Scientific-Research Institute of Metallurgical Heat Engineering OJSC VNIIMT 16 Studencheskaya St., Yekaterinburg, Russia, Tel: +7 (343) , fax: +7 (343) website: A/c in Yekaterinburg affiliate of NOMOS-BANK (JSC) Yekaterinburg Correspondent account No , BIK , INN , KPP , OKVED OKPO OJSC Scientific-Research Institute of Metallurgical Heat Engineering (VNIIMT) established in 1930 as Ural Division of All-Union Heat Engineering Institute is widely known in Russia and the CIS. The Institute focuses on development of high-technology heat engineering units, energy efficient and ecologically friendly technologies in ferrous and non-ferrous metallurgy, machine-building and other fuel-consuming branches of industry. Highly-qualified academic researchers, unique experimental and production facilities and own research and design centre enable efficient scientific-and-research, design-and-experimental, engineering and project works, delivery of equipment, designer's supervision and commissioning works including execution of turnkey contracts in the following areas: Sintering: development of techniques and modes of metal raw material heat treatment; design of energy-efficient agglomeration hearths and agglomeration gas heat recovery circuits allowing to reduce energy consumption and dust and gas emissions. Pellet production: optimal traveling grate pelletizing furnaces for heat treatment of iron-ore pellets from various concentrates (hematite, magnetite, etc.) with optimal automatic process control system. Preparation of metallic and nonmetallic raw materials: technique of iron-ore raw material dephosphorization by roasting and leaching; installations for drying high-moisture dispersive materials of various designs; efficient techniques of magnetizing roasting and subsequent dressing; technique of rare-earth element extraction (for example, germanium from germanium iron ores). Blast-furnace ironmaking: explosion-proof near-furnace systems of blast furnace slag granulation giving a high-quality product for cement production; optimal control system for hot blast stoves; an innovative bench for drying hot metal and steel-smelting ladles; copper coolers and tuyeres of blast furnaces. DRI (direct reduction of iron) improvement of the reduction technique in shaft furnaces for radical improvement of technical and economic indicators of their operation (productivity is increased twice); technique of raw material reduction in rotary furnaces using coal as the reductant. Lime production: development of the technique and increase of lime production process efficiency: in shaft furnaces; in double-shaft furnaces; in rotary furnaces; in stacked-tower preheater - rotary furnace installations; in shaft calciner - rotary furnace installations (VNIIMT innovative technology). Granulation of metal melts: development of technologies and designs of explosion-proof plants for near-furnace granulation of metallurgical slag, molten metal, etc., including heat recovery; OJSC Scientific-Research Institute of Metallurgical Heat Engineering (OJSC VNIIMT) 16 Studencheskaya St., Yekaterinburg, Russsia, Tel: +7 (343) , fax: +7 (343) , aup@vniimt.ru,

5 Reheating furnaces: development of new and update of the existing designs of furnaces for stock heating; high-performance systems of reheating furnace firing with recovery and regeneration firing systems based on the innovative burner units designed by VNIIMT; switching the furnace firing systems to cheaper fuel types; development and implementation of optimal furnace operating parameters. Heat-treatment furnaces development of techniques and equipment for heat treatment of roll stock and metal products including those with protective atmospheres: thermochemical treatment conditions ensuring retention or directional change in chemical composition of metal surface; gas dampers for heat-treatment furnaces; spray quenching units and other elements of convective cooling systems; Furnaces with protective atmosphere and gas treatment units: development of the furnace structure, design, manufacture, delivery and commissioning works; development of a technology for treatment of articles and devices for protective gas generation; calculation, development and manufacture of endogas and exogas atmosphere generators for metal product thermochemical treatment units; gas analysis systems for monitoring and control of physico-chemical properties of protective process atmospheres. Reheating, heat-treatment and drying furnaces with convection heat transfer: development, design and manufacture using industrial heat-resistant (up to 900 о С) furnace fans designed by VNIIMT. Rolled products: techniques and units for controlled high-speed air-to-water cooling (quenching) of rolled ferrous and non-ferrous metal products including thick plate on mill 5000; replacement of oil quenching technology with VNIIMT's eco-friendly air-to-water technique; innovative technique of oily mill scale processing; line of wire rod accelerated air cooling with process improvement. Manufacturing manufacture and delivery of: high-performance burner units; heat-resistant (furnace) fans (up to 900 о С); copper coolers for blast furnaces and nonferrous furnaces based on VNIIMT technology; Pitot tubes for measuring flow rates and pressures. OJSC VNIIMT developments are widely used in metallurgical enterprises of Russia, Ukraine, Kazakhstan, China, India and others. For detailed information on institute developments, please visit OJSC VNIIMT site at Contact details: Lik Zajnullin General Director OJSC VNIIMT Tel: +7 (343) , fax: +7 (343) Studencheskaya St., Yekaterinburg, Russia, , aup@vniimt.ru, website: OJSC Scientific-Research Institute of Metallurgical Heat Engineering (OJSC VNIIMT) 2 16 Studencheskaya St., Yekaterinburg, Russsia, Tel: +7 (343) , fax: +7 (343) , aup@vniimt.ru,