Patent ID: 9739476
Date: 2017-08-22
CPC Classifications: F22B

Claim:
1. An evaporator apparatus for receiving liquid water from a steam drum and providing at least one of steam and heated liquid water to the steam drum, the evaporator apparatus comprising: a first evaporator having a first inlet for receiving liquid water, and having at least one first evaporator conduit, each first evaporator conduit defining at least one first evaporator passageway extending from the first inlet through a gas duct to a first outlet for transferring heat from gas to water within the first evaporator passageway, a length of the first evaporator passageway extending through the gas duct being substantially perpendicular to a gas flow axis along which the gas will flow through the gas duct during operation; a first feed conduit extending from the steam drum and connecting to the first inlet for transporting the liquid water from the steam drum to the first inlet; a second evaporator having a second inlet for receiving liquid water, and having at least one second evaporator conduit, each second evaporator conduit defining at least one second evaporator passageway extending from the second inlet through the gas duct to a second outlet for transferring heat from the gas to water; a second feed conduit extending from the steam drum and connecting to the second inlet for transporting the liquid water from the steam drum to the second inlet; an output conduit in communication with the first outlet of the first evaporator and the second outlet of the second evaporator, and with the steam drum, the output conduit being configured for outputting at least one of steam and heated liquid water from both the first and second evaporators to the steam drum; wherein the first feed conduit and the second feed conduit are separate flow lines that extend from the steam drum to the first inlet and the second inlet, respectively, such that no portion of the liquid water from the steam drum passing along the first feed conduit can mix with the liquid water from the steam drum passing along the second feed conduit; wherein a number of passes of each second evaporator passageway through the gas duct is greater than a number of passes of each first evaporator passageway through the gas duct; wherein the second evaporator is positioned in the gas duct above the first evaporator; and wherein the greater number of passes of each second evaporator passageway through the gas duct relative to the number of passes of each first evaporator passageway through the gas duct, and the location of the second evaporator above the first evaporator, ensures that the steam forms more quickly in the first evaporator than the second evaporator and exits the first evaporator and enters the output conduit prior to exiting the second evaporator and entering the output conduit during a startup operation to reduce instability during the startup operation.