{HEAD ~ The above embodiment} has described {TAIL ~ the use} of the vapor produced in the final evaporation stage, but also vapor generated in other evaporation stages may be used, if the properties of the vapor are suitable for the purpose 
{ HEAD ~ The above embodiment } has described { TAIL ~ the use } of the vapor produced in the final evaporation stage , but also vapor generated in other evaporation stages may be used , if the properties of the vapor are suitable for the purpose
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