Afterburners including methods of making and operating
The present teachings provide designs and materials of construction for afterburners as well as methods of making the afterburners. More specifically, the afterburners of the present teachings can include a compressible, resilient refractory material such that thermal expansion of other adjacent components, for example, a fuel cell stack of a fuel cell unit, can be accommodated by the afterburner. The present teachings also provide methods of reducing contaminants in exhaust streams and/or generating heat.
1 . A fuel cell unit comprising:
an afterburner, the afterburner comprising:
a stack of layers, wherein each layer is a compressible, resilient refractory material comprising fibers of silica, alumina or silica-alumina mixtures and defines one or more apertures fully through the layer in a direction of a flow of exhaust from an inlet face to an outlet of the stack of layers, wherein the one or more apertures of the stack of layers define non-linear channels through the stack of layers from the inlet face to the outlet of the stack of layers, wherein the non-linear channels comprise channels perpendicular to a flow of exhaust from the inlet face to the outlet of the stack of layers, each channel perpendicular to the flow of exhaust is defined by an aperture through a corresponding layer, which aperture extends greater than 50% of a length across the stack of layers in a direction perpendicular to the direction of flow of exhaust from the inlet face to the outlet of the stack of layers and which aperture extends fully through the corresponding layer in the direction of flow of exhaust from the inlet face to the outlet of the stack of layers; and the stack of layers remains compressible and resilient; and
a combustion catalyst associated with exposed surfaces of the one or more apertures of at least one layer of the stack of layers such that the combustion catalyst is associated with an exposed surface of a non-linear channel; and
a fuel cell stack in operable fluid communication with the inlet face of the stack of layers.
2 . The fuel cell unit of claim 1 , wherein the amount of combustion catalyst associated with the exposed surface of a non-linear channel comprises a gradient.
3 . The fuel cell unit of claim 2 , wherein the gradient comprises an increase in the amount of combustion catalyst present from the inlet face of the stack of layers to the outlet of the stack of layers.
4 . The fuel cell unit of claim 3 , wherein a second gradient is present, wherein the second gradient comprises a decrease in the amount of combustion catalyst present after the increasing gradient and towards the outlet of the stack of layers.
5 . The fuel cell unit of claim 1 , wherein the exposed surfaces of the one or more apertures of the layer of the stack of layers closest to an inlet of the afterburner and/or the one or more apertures of the layer of the stack of layers closest to an outlet of the afterburner do not comprise a combustion catalyst.
6 . The fuel cell unit of claim 1 , wherein the exposed surfaces of the one or more apertures of one or more layers of the stack of layers away from an inlet and an outlet of the afterburner comprise a combustion catalyst and an increased surface area compared to the exposed surfaces of the one or more apertures of layers of the stack of layers closest to the inlet and the outlet of the afterburner.
7 . The fuel cell unit of claim 6 , wherein at least one of the layers of the one or more layers of the stack of layers away from the inlet and the outlet of the afterburner comprising a combustion catalyst and an increased surface area comprises one or more apertures designed to mount an igniter and/or a thermal sensor assembly.
8 . The fuel cell unit of claim 7 , comprising an igniter, the igniter in operable thermal communication with the combustion catalyst.
9 . The fuel cell unit of claim 7 , comprising a thermal sensor assembly, the thermal sensor assembly in thermal communication with one or more non-linear channels comprising a combustion catalyst.
10 . The fuel cell unit of claim 1 , comprising an igniter, the igniter in operable thermal communication with the combustion catalyst.
11 . The fuel cell unit of claim 1 , comprising a thermal sensor assembly, the thermal sensor assembly in thermal communication with one or more non-linear channels comprising a combustion catalyst.
12 . The fuel cell unit of claim 1 , wherein the inlet of the stack of layers is in thermal communication with a power conditioning component, the power conditioning component being in electrical communication with the fuel cell stack.
13 . The fuel cell unit of claim 1 , wherein the fibers of silica, alumina or silica-alumina mixtures are in the form of a paper, a felt, a mat, or a blanket.
14 . The fuel cell unit of claim 1 , wherein the fibers of silica, alumina or silica-alumina mixtures are in the form of a continuous strand mat, a chopped mat, or woven or knit cloth.
15 . A fuel cell unit comprising:
an afterburner, the afterburner comprising:
a contiguous stack of layers, wherein each layer is a compressible, resilient refractory material comprising fibers of silica, alumina or silica-alumina mixtures, and defines one or more apertures fully through the layer in a direction of a flow of exhaust from an inlet face to an outlet of the contiguous stack of layers, wherein the fibers of silica, alumina or silica-alumina mixtures are in the form of a continuous strand mat, a chopped mat, or woven or knit cloth, and the one or more apertures of the contiguous stack of layers define non-linear channels through the contiguous stack of layers from an inlet face to an outlet of the contiguous stack of layers, wherein the non-linear channels comprise channels perpendicular to a flow of exhaust from the inlet face to the outlet of the contiguous stack of layers and channels perpendicular to the flow of exhaust are defined by one or more apertures fully through a corresponding layer in a direction of the flow of exhaust from the inlet face to the outlet of the contiguous stack of layers, which one or more apertures extends greater than 50% of the length across the contiguous stack of layers in a direction perpendicular to the direction of the flow of exhaust from the inlet face to the outlet of the contiguous stack of layers, and the contiguous stack of layers remains compressible and resilient; and
a combustion catalyst associated with exposed surfaces of the one or more apertures of at least one layer of the contiguous stack of layers such that the combustion catalyst is associated with an exposed surface of a non-linear channel; and
a fuel cell stack in operable fluid communication with the inlet face of the contiguous stack of layers.
16 . The fuel cell unit of claim 15 , wherein the amount of combustion catalyst associated with the exposed surface of a non-linear channel comprises a gradient.