OCR Text |
Show 12 "combustion mode" is conducted in the Heater A, while the Heater B is under the "N2 Jet mode". (Condition. 1) The lower demonstrates the reverse situation. (Condition.2) In practice, the cycle time for mode switch can be adjusted between 50 and 100 seconds so as to secure the constant supply of high-temperature nitrogen gas to the tundish, and the tundish is heated by convection heat transfer from nitrogen gas jet. As shown in Table II, the N2 Jet Heater introduced in No.4 Slab caster is designated to supply 1500'C of nitrogen gas with 1.000Nm3/Hr of supply rate. At the same time, 140°C of exhausted gas temperature out of the system is aimed to achieve the high thermal efficiency. The N2 Jet Heater consists of N2 gas heater, pipe works and their control unit, and gas exhausting fan. The N2 gas heater, whose configuration is schematically shown in Fig.22, is the combustion chamber assembled with main and pilot burners and regenerator and blowing nozzle. For the safety purposes, the flame detector with ultraviolet phototube, temperature and CO gas monitors in combustion chambers, and pressure switches in each gas pipe line are equipped. 0Q open close Combustion chamber Regenerator Exhaust gas Heater B ESS e s s- ing N2 Tundish Condition 1 Heater A ; Combustion mode Heater B ; N2 jet mode Recycling N2 • -*-^ •.. Tundish ^Measured point 1,1,1,1,1,1,1,1,1,1,1, jrr^/ Condition.2 Heater A ; N : jet mode Heater B ; Combustion mode Fig.21 Schematic diagram of N : Jet Heater Table II Specifications of N 2 Jet Heater Item N2 Jet Heater Combustion N2Jet Total weight Weight of regenerator Burner capacity Recycling N 2 gas Temp of exhaust gas Temp of N2 gas jet Flow of N'2 eas Cvcle time Specification 2.8 t 0.3 t 2500 MJ/hr £ 200NmJ/hr 140°C !500°C 1000Nm3/hr 100 sec Refractories Combustion chamber Thermocouple ^ Regenerator CO gas monitor Fig.22 The structure of N2 sas heater |