| 摘要 |
<p>PURPOSE:To prevent the fluctuation of calorific value at the time of switching by a method wherein the flow rate of mixed gas for combustion is gradually increased or decreased depending on response time set by the character of flow rate-regulating valves when a plurality of hot blast stoves attached to a blast furnace are switched from combustion to draft or from draft to combustion. CONSTITUTION:Blast furnace gas (BFG) having low calorific value and converter gas (LDG) having high calorific value are mixed with liquefied natural gas (LNG) in a mixing chamber 2 to produce gas having appropriate calorific value which is then supplied to hot blast stoves HS1-3. When the hot blast stove HS1 is switched from draft to combustion and the hot blast stove HS2 is switched from combustion to draft, the calorie of the mixed gas is varied by the difference in the response time to switching of flow rate-regulating valves 14 for the mixed gas and flow rate- regulating valves 11-13 for BFG, LDG and LNG. An increase and decrease rate X of the mixed gas at the time of switching is determined by expression I. By the value obtained, the gas flow rate-regulating valves 12-14 are controlled to prevent the variation of the calorific value of the mixed gas. The imperfect combustion of the gas and the reduction in thermal efficiency can be prevented.</p> |
