http://www.cheresources.com/invision/topic/9116-moderating-steam/
"Lp steam to air & acid gas chambers used for sudden s/d in sulphur plant to protect this cchambers from back heating of combustion chamber.it use also when combustion chamber is higher than 400 C and there is no flow of air & acid gas when startup burner is on service.you know that it's recommend not use carbon steel over 400C ."

"During start-up of a SRU, it is very important to maintain proper air: acid gas ratio(which is 2:1 in the tail gas of H2S: SO2, more sepcific: final claus reactor outlet). To avoid temperature soot-up in a reaction furnace during start-up / SD ,LP Steam line is provided. Mainly it is using to control temperature and also to maintain a good flame color, as in a SRU acid gas is burn in a deefficiency of air. When reaction furnace temperature is low( less than LP Steam temperature)N2 is is used and when it is more LP steam is used as it is cheap to produce. We call this type of steam as Tempering Steam.
Is it a CBA process or 3 stage claus process."

По контексту пар охлаждающий. Возможно, есть более точный термин (гасящий, смягчающий)?

Контекст: производство серы методом Клауса