o Furnace walls of modern combustors are lined with metal tubing through which water is circulated.This water wall is then part of the boiler or heat recovery system.The water tubes protect the combustion chamber housing by transferring the heat into the water o production of steam drops dramatically with increases in moisture in the fuel as in well as the fraction of noncombustible UNEP Furnace walls of modern combustors are lined with metal tubing through which water is circulated. This water wall is then part of the boiler or heat recovery system. The water tubes protect the combustion chamber housing by transferring the heat into the water  production of steam drops dramatically with increases in moisture in the fuel as in well as the fraction of noncombustible