direct-fired furnace

例句：

1. 1. The direct-fired furnace is a type of furnace that uses direct combustion to heat the material being processed.
   直接燃烧炉是一种使用直接燃烧来加热正在加工材料的炉子。
2. 2.Direct-fired furnaces are often used in industries that require high temperatures and energy efficiency.
   直接燃烧炉通常用于需要高温和能源效率的行业。
3. 3. The direct-fired furnace has become increasingly popular in recent years due to its ability to produce high-quality steel without the need for expensive alloys.
   由于其无需昂贵合金即可生产高质量钢材的能力，直接燃烧炉近年来越来越受欢迎。