Liquid heaters and vaporizers – Miscellaneous
Reexamination Certificate
2000-04-19
2001-05-29
Wilson, Gregory (Department: 3749)
Liquid heaters and vaporizers
Miscellaneous
C165S104160
Reexamination Certificate
active
06237541
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process chamber in connection with a circulating fluidized bed reactor for utilizing internal or external circulation of solid material or both in heat transfer purposes. Said process chamber is located inside the furnace of the circulating fluidized bed reactor adjacent to at least one of the furnace walls, and the interior of said process chamber is provided with fluidized bed heat exchanger means for heat transfer from the solid material to heat transfer medium inside the heat exchanger means.
Fluidized bed heat exchangers (later on abbreviated as FBHE's), which transfer heat between bed of fluidized particulate solids and heat transfer medium, have been in use for many years and in many appliances.
A circulating fluidized bed reactor (later on abbreviated as CFB) comprises a furnace and at least one particle separator which are connected together. A particle separator separates solid particles from flue gas—solid particles suspension entering the separator from the upper part of the furnace. Separated solids are recycled back to the lower part of the furnace via separator and loopseal. This solid circulation is called external circulation, later on EC. In addition to vertical upflow of flue gas and solid particles in the furnace entering the separator inlet, there is a vertical downflow of particles near the furnace walls. This solids circulation is called internal circulation, later on IC.
FBHE's in circulating fluidized bed reactors can be either internal or external type or both, depending on whether the FBHE is utilizing the particles of internal and/or external circulation. A typical CFB process feature is that external circulation of solid material decreases rapidly when load decreases, with the result that heat transfer in the FBHE can become inadequate. Systems with FBHF's in contact with both internal and/or external particle flow streams have been developed to solve that problem.
In CFB reactors, FBHE process chambers can be integrated with the furnace walls and FBHE can be constructed by using bent tubes. The location of an integrated FBHE process chamber can be anywhere from the lower part to the upper part of the reactor furnace, and may be either inside or outside of the furnace walls.
FBHE process chambers located inside the lower part of the furnace can be open in the top part to allow internally refluxing particles to flow into the FBHE process chamber downwards along the furnace walls as suggested by Chambert according to U.S. Pat. No. 5,060,599. Further it is possible according to Chambert to arrange the site of the construction so that particles from the cyclone outlet loop seal can also spill into the same FBHE process chamber.
Furthermore, Hyppanen in accordance with U.S. Pat. No. 5,332,553 suggests a FBHE process chamber in which the roof of said FBHE process chamber is provided with holes or screens for classifying particles before they can enter the FBHE process chamber. However, this kind of roof construction with hole s or screens has the disadvantage that screens can be blocked (or eroded) by heavy solids flow, and especially by fuel and coarse particles splashing from the main fluidized bed because said FBHE process chamber is located inside the reactor furnace at the lower part of the same.
SUMMARY OF THE INVENTION
According to the present invention a FBHE process chamber in connection with a circulating fluidized bed reactor, i.e. CFB, is provided for utilizing internal or external circulation of solid material or both in heat transfer purposes, wherein said process chamber is located inside the furnace of the circulating fluidized bed reactor adjacent to at least one of the furnace walls, the interior of said process chamber being provided with heat exchanger means for heat transfer from the solid material to heat transfer medium inside the heat exchanger means, wherein the process chamber comprises a top closed barrier wall forming the roof of the process chamber, and wherein the inlet of the solid material into the process chamber is arranged to the lower part of the wall of the process chamber and the outlet of the solid material out of the process chamber is arranged to the upper part of the wall of the process chamber.
The main object of the present invention is that by using totally particle tight barrier wall forming the roof of the process chamber above the FBHE, the following improvements with respect to relevant prior art presented hereabove can be achieved:
There are no such open areas above the FBHE which are:
liable to plugging,
liable to erosion,
complicated to manufacture, and
falling particles cannot impact FBHE tubes, so that there is no need of any additional shields for the FBHE tubes inside the process chamber.
Further according to a very important feature of the invention prior to the said process chamber in the direction of the flow of said solid material an inlet chamber is provided inside the furnace of the circulating fluidized bed reactor for directing the solid material to the inlet of the process chamber.
With reference to the foregoing it is further the object of the present invention to overcorhe the drawbacks of the prior art constructions by the above mentioned combined system of at least one process and inlet chambers. Said combination provides sophisticated possibilities to control over the overall heat transfer rate in a FBHE process chamber. In accordance with the above mentioned advanced system the heat transfer of a FBHE process chamber can be controlled by various manners such as:
1. by guiding a variable portion of the circulating solid material to pass the FBHE process chamber, or
2. differential fluidization within the FBHE process chamber and the inlet chamber (for instance possibility to vary fluidizing velocity in the inlet chamber without fear of erosion),
3. sectioning the FBHE i.e. the total area of heat transfer surfaces into separately controllable process chambers, or/and
4. by combinations of at least two of the manners 1-3
Further according to the present invention said inlet chamber is arranged in vertical direction inside the furnace of the circulating fluidized bed reactor for directing the solid material to the inlet of the process chamber, wherein the inlet of the inlet chamber located at the top of the same is open for receiving flow of solid material and wherein the top closed barrier wall of the process chamber is inclined so as to guide the solid material flowing down onto the top closed barrier wall to the inlet of the inlet chamber.
Thus, additionally the combined system of at least one process and inlet chambers provides following advantages:
the internal circulation of solid material tend to trap into the inlet chamber because of slope or inclined closed barrier wall forming the roof of the process chamber
occasionally possible unintended stalling of the flow of solid material through the FHBE does not interfere the total CFB process i.e. the internal or external circulation of solid material can be maintained. The excess of the flow of solid material passes by the inlet of the inlet chamber into the reactor furnace.
REFERENCES:
patent: 5060599 (1991-10-01), Chambert
patent: 5181481 (1993-01-01), Dietz
patent: 5332553 (1994-07-01), Hyppanen
patent: 5345896 (1994-09-01), Hyppanen
patent: 5463968 (1995-11-01), Abdulally
patent: 5526775 (1996-06-01), Hyppanen
patent: 6029612 (2000-02-01), Wietzke et al.
patent: WO 89/05942 (1989-06-01), None
Alliston Michael G.
Kokko Ari
Luomaharju Tero
Mero Timo
Connolly Bove Lodge & Hutz
Kvaerner Pulping Oy
Wilson Gregory
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