单项选择题
One of the main purposes of refractories in a boiler furnace is to（）
A.help preheat the air for the furnaces B.help preheat the feedwater C.protect economizer from excessive heat D.prevent excessive furnace heat losses
单项选择题 What is the first thing you would check on taking over a watch?（）
单项选择题 Soot blowers should be used in proper sequence so that（）
单项选择题 The valve that prevents water from backing out of the boiler into the feed line is the（）.
