Practical Examples of Heat Regenerative System at Steelmaking Works

Transcription

1 2nd India-Japan Energy Forum Practical Examples of Heat Regenerative System at Steelmaking Works On Monday 4 February 2008 in Delhi Nisshin Steel Co., Ltd. Yukio Tomita 1

2 Structure of the Regenerative Burner The regenerative burner is the burner where a pair of two burners having the built-in heat storage unit are installed, and one unit exhausts combustion gas and accumulates heat, while another burner is combusting. Heat is accumulated by alternating between combustion and exhaust every 20 to 60 seconds, preheating combustion air to high temperature. Heat storage unit Regenerative burner (heat storing burner) Switching valve Fuel By repeating the above cycle, 50 to 90% of the exhaust heat recovery can be acquired. (Source: NEDO) 2

3 Heat Account of the Regenerative Burner Furnace NEDO carried out the High Performance Industrial Furnace Field Project for various 167 units. As a result, 74% of exhaust heat recovery rate was obtained on an average and the energy saving rate exceeding 30% was obtained. Homogenizing the temperature distribution improves crystalloid property and yield, extends the life of the radiant tube, shortens the length of the continuous, and enables to pursue the reduction of the metal loss in the non-ferrous metal melting. 51% Exhaust gas 61%10% 100% 51% 49 % Heat loss :13% Product: 26% (Source: NEDO) 3

4 Energy Saving Rate of the Regenerative Burner Furnace Energy saving rate (%) Field test project 167 units Heating (continuous) Heating (batch) Ladle Heat treating (continuous) Heat treating (batch) Gas treatment Smelting ,000 1,500 Treatment temperature ( C) Energy saving rate Average 30% (Source: Japan Industrial Furnace Manufacturers Association) 4

5 Introduction Status of the Regenerating Furnace by Furnace Type 12 TJ/year/unit 21 TJ/year/unit Firing 9% Smelting 12% 540 units (2003) Heating 27% Amount of energy saving amount: 83TJ/year/unit Heat treating 52% 12 TJ/year/unit Amount of energy saving effect 18PJ/year (P:10 15 ) 36TJ/year /unit Source: Industrial heating, Vol.41, No.4, p.19, ) 5

6 Temperature of Preheated air and Amount of NOx Emission Without heat recovery Fuel: Gaseous by-product Furnace temperature: 1350 C Conventional combustion technique NOx 1000 Amount of used gas [ ] Conventional exchanger (metal) heat Concentration of emitted NO (ppm, at 11%O 2 ) Regenerating burner Temperature of preheated air [ C] Low NOx combustion technology is required. (Source: Document for Japan-China Environmental Energy Technology Meeting in 2005) 6

7 High Temperature Air Combustion Technique Burner Fuel Temperature of preheated air [ C] Air Uncombustible region Low NOx combustion (High temperature air combustion technique) Development goal Oxygen concentration at the combustion field [%] DeNOx is required Conventional technology Gas temperature [ C] Formation of hot section Conventional technique: High NOx ~ 500ppm (experimental value) High temperature air combustion Very low NOx to 40ppm (experimental value) (Source: Document for Japan-China Environmental Energy Technology Meeting in 2005) Distance [m] 7

8 Production Process Adopted by Nisshin Steel Nisshin Steel: 3.73 million tons (steel products in 2005) Outline of the production process Ordinary steel and special steel products: 0.99 million tons Stainless steel sheet: 0.56 million tons Surface-treated steel sheet : 2.19 million tons Converter Blast Electric Continuous casting Heating Hot rolling * * Continuous annealing Cold rolling Bell annealing Galvanizing line Coating line 8

9 Application Status of the Regenerative Burner at Nisshin Steel Converter Under consideration (1) Continuous annealing Blast Drying apparatus for the pig iron and steel pan Electric Continuous cast Heating Continuous annealing Heating device for the annealing Bell annealing Galvanizing line (2) Deodorization equipment in the coating drying Coating line 9

10 Application at Toyo Works of Nisshin Steel Cold rolling Cold rolling Galvanizing line Works Names of facilities Specifications of facilities Yearly production capability (thousand tones/ year) Product Toyo Works Picking and cold rolling Pre-rolling type pickling and cold-rolling mill Sextuple type (1 unit) + shallow bath type Sextuple type: 4 units 1 set 1,080 Cold-rolled steel Surface treatment process Galvanizing facility Horizontal radiant tube Vertical direct reduction 1 set 480 Surface-treated steel sheet 10

11 Facilities Used at Toyo Works: Horizontal Radiant Tube Furnace Tension leveler Galvanizing center section Cooling section Horizontal radiant tube After treatments Oiler Vertical direct reduction Preheating Steel sheet Shipment Exit-side looper Tension reel Payoff reel Pretreatment Two-stand type skin path mill Plating pot To the galvanizing facility Welder Entry-side looper 11

12 Outline of the Horizontal Radiant Tube Furnace Object part Second heating zone in the annealing (No.1 to 4 zones) Dimensions of the material Thickness: 2.3mm, Width: 1,350mm Processing material Ordinary steel Processing temperature 750 C Processing capacity Max.140t/h Fuel LPG FOG cooling facility Alloying Cooling zone Soaking zone First heating zone Second heating zone Preheating zone Steel sheet Galvanizing facility Modification range 12

13 Comparison of Radiant Tube Systems Conventional recuperator type radiator Regenerative radiant tube Ceramic honeycomb Switch Recuperator Maximum combustion capacity Number of installed units Exhaust heat recovery rate Emission value 150,000 Kcal/h 52sets 25 to 30% 150 ppm Maximum combustion capacity Number of installed units Exhaust heat recovery rate No emission value Switching time 120,000 Kcal/h 52 sets More than 70% Less than 140 ppm 32 seconds 13

14 Appearance of the Regenerative Radiant Tube Device Exhaust gas pipe Combustion air pipe Fuel pipe Switch Regenerative burner (4 units) 14

15 Inside of the Radiant Tube Furnace Radiant tube Section view of the Hearth roll 15

16 Operation Performance Operation conditions Amount of production t/h 110 Temperature at the entry side of the objective Temperature at the exit side of the objective C 640 C 752 Transit time in the sec 92 Energy saving rate (compared with the conventional type) Operation record % 26 Heat efficiency % 67 Exhaust heat recovery rate % 80 NOx value (0.11% conversion) Yearly amount of energy saving effect ppm 118 GJ/y 40,720 Amount of used fuel Combustion conditions GJ/ h 17.7 Temperature at the combustion air inlet 20 Temperature at the combustion air outlet 880 Temperature at the gas inlet 950 Temperature at the exhaust gas outlet

17 Positions for Measuring Temperature of Exhaust Gas and Preheated Air Temperature measurement Thermocouple Ceramic honeycomb Exhaust gas or combustion air 17

18 Record of Temperature of Exhaust Gas and Preheated Air 880 C 950 C Combustion Air temperature Temperature of the exhaust gas (inlet) Temperature ( C) Time (minute) Temperature of the exhaust gas (outlet) 270 C 18

19 Effect of Use of the Regenerative Burner fuel Reduction of amount of used Steel product Wall/ coolant Exhaust gas % % Energy balance [%] Reduction of NOx concentration 16% 19

20 Temperature Distribution of the Radiant Tube <Result of test equipment (Source: Industrial hearing, Vol. 41, Page No.3 Page. 32)> 850 Temperature ( C) Recuperator type Regenerative type Start of the radiant tube Length of the radiant tube End of the radiant tube 20

21 Radiant Heat Flux from the Radiant Tube <Heat flux from the radiant tube based on the combustion study that is performed with the combustion load similar to the operation performance using the test equipment (Source: Industrial hearing, Vol. 41, Page No.3 Page. 32)> The radiant heat flux rate is approximately doubled (=22.4/10.8) The life of the radiant tube will be extended when providing the same heat flux since the maximum temperature can be lowered. ) 2 Heat flux (kw/m Recuperator type 10.8kw/m 2 Regenerative type 22.4kw/m 2 Start of the radiant tube Length of the radiant tube End of the radiant tube 21

22 Application at Ichikawa Works of Nisshin Steel Works Facilities Specifications of facilities Yearly production capability (thousand tons/ year) Ichikawa Works Major Facilities at Ichikawa Works Surface treatment Galvanizing facility Horizontal direct reduction Coating Coating facility Catenary type hot air circulating direct heating Coating Coating facility Catenary type hot air circulating indirect heating Products 1 set 1,080 Galvanize d product 1 set 72 Coated steel sheet 1 set 98 Coated steel sheet 22 22

23 Ichikawa Works No.3 Continuous coating line Deodorizing Ventilation (VOC containing gas) Introduction of Regenerative Thermal Oxidizer (RTO) No.2 Water Quench No.1 Oven oven No.2 Oven No.1 coater Coater No.2 Coater Pretreatment Exit-side shear Tension Reel Exit-side Looper Tension Leveler No.1 Water Quench Chemical coater Reel Shear Welder Entry-side Looper 23

24 Flow Chart of the Exhaust Gas before Introducing the RTO Oven exhaust gas No.1 Oven No.2 Oven Auxiliary fuel (Natural gas) 160 m3/h VOC containing gas Air supply for Oven Deodorizing Primary heat exchanger Secondary heat exchanger 24

25 Characteristics of RTO Auxiliary burner Combustion Room Heat Exchanger Stack Honeycomb heat storage unit VOC containing gas Two-stage heat recovery is available using the honeycomb heat storage unit and heat exchanger Oven ventilating air is uniformly heated to high temperature to enable the dilution combustion using the honeycomb heat accumulator and performing combustion using small amount of auxiliary fuel to decompose the VOC Superior energy saving effect and high VCO removal efficiency are achieved (complying with VOC emission concentration regulation) 25

26 Flow Chart of the Exhaust Gas after Introducing the RTO Oven exhaust gas No.1 Oven No.2 Oven Auxiliary fuel (Natural gas) 50 m3/h VOC containing gas Air supply for Oven Heat exchanger Heat storage unit RTO (Regenerative Thermal Oxidizer) 26

27 Outline of Operation of the RTO Unit No. Unit No. Heat storage unit Cycle1 Combustion Chamber No.1 No.2 No.3 No.1 Gas inlet No.2 Gas exhauste No.3 Purge Clean Gas Cycle2 Combustion Chamber No.1 No.2 No.3 No.1 Purge No.2 Gas inlet No.3 Gas exhauste Clean Gas Gas Inlet Gas Inlet Cycle3 Gas Inlet Combustion Chamber No.1 No.2 No.3 Clean Gas Unit No. No.1 Gas Exhaust No.2 Purge No.3 Gas inlet 27

28 Comparison of Consumed Amount of Fuel before and after Introducing the RTO 200 Fuel consumption at deodrizing (knm3/month) Introduction of RTO '05/4 '05/10 '06/04 '06/10 '07/04 Month Effect: Approximately 1.400kl/ year of the energy consumption is reduced (crude oil equivalent) 28

29 Conclusion Nisshin Steel achieved significant energy saving by actively introducing the regenerative system. 29