求翻译：高炉煤气发热值较低，要达到风温1250℃，需预热空气、煤气。采用换热器预热煤气、助燃空气技术，预热后煤气温度可达到180℃ ；为了达到1250℃风温，需要将助燃空气预热到400～600℃左右，采用常规的热管换热器无法达到此要求；采用热风炉自身预热法可以实现1250℃风温，但投资成本较高。是什么意思？

Blast furnace gas heating value is lower, to achieve the air temperature of 1250 ° C, need to preheat the air and gas. Preheat gas heat exchanger, combustion air technology, preheat the gas temperature can reach 180 ° C; in order to reach 1250 ° C air temperature, combustion air preheated to about 4

The blast furnace coal gas heat value is low, must achieve wind warm 1250℃, needs the preheated air, the coal gas.Uses the heat interchanger preheating coal gas, the combustion air technology, after the preheating coal gas temperature may achieve 180℃; In%

Lower heating value of blast furnace gas to achieve temperature 1250 ° c, need to preheat air and gas. Using heat exchangers Preheat gas and combustion air technology, after the preheat gas temperatures up to 180 ° c; for up to 1250 ° c air temperature, combustion air needs to be preheated to about