Chemistry of inorganic compounds – Nitrogen or compound thereof – Carbon containing
Reexamination Certificate
2001-05-02
2003-11-18
Langel, Wayne A. (Department: 1754)
Chemistry of inorganic compounds
Nitrogen or compound thereof
Carbon containing
C422S187000, C422S198000, C422S202000, C422S221000, C423S374000, C423S375000, C423S376000, C423S659000
Reexamination Certificate
active
06649137
ABSTRACT:
This invention relates generally to high-temperature industrial processes, and more particularly, to a reactor apparatus and its use in associated processes.
The production of chemicals such as hydrogen cyanide and nitric acid using a reactor has been known for some time. For example, the one-stage synthesis of hydrogen cyanide from ammonia and a hydrocarbon gas in which heat is supplied by simultaneous reactions with air in the presence of a platinum metal catalyst was disclosed by Andrussow in U.S. Pat. No. 1,934,838. Numerous modifications and improvements relating to this process have been described in other patents.
To promote efficiency, often an insulator is added to the exterior of the reactor to prevent heat loss. However, the materials comprising the reactor limit the temperatures at which it can safely operate. Sometimes a water jacket is incorporated with the reactor to prevent overheating of the reactor and a potential failure of the vessel. In the event of an interruption of service to the water jacket, temperatures may rise in the externally-insulated reactor to a level which causes the reactor or the flanged connections or other vessel-components to fail, allowing hazardous chemicals to be released into the atmosphere. The external insulator, while increasing efficiency, may also increase the likelihood of a reactor failure. There have been some attempts to insulate reactors internally with refractory materials, but typically refractory materials are very susceptible to cracking in response to thermal and mechanical shocks, which makes it difficult or impossible to start and stop the processes or remove the reactor head for maintenance without damaging the refractory. It is also extremely difficult to maintain a refractory in suspension, such as on the inside surface of a domed or conical reactor head, because refractories have relatively low tensile strength.
In addition, conventional reactor designs such as the system shown in
FIG. 1
exhibit a poor flow distribution characterized by flow separations. As shown in
FIG. 1
, a poor flow distribution entering reactor
2
with a refractory
4
may cause an upflow on the left side of reactor
2
, resulting in decomposition and soot accumulation
6
on wall
8
. The jet effect of turbulent flow as shown in
FIG. 1
may also result in shorter catalyst life as the flow may utilize only a limited portion of catalyst
9
. Additionally, in processes containing highly flammable feed mixtures, such as oxygen-enriched HCN or oxygen enriched ammonia oxidation reactors, the flow distribution depicted in
FIG. 1
creates a significant potential for flashbacks and detonations.
Further, reactor heads typically include a large weld-neck or lap joint flange for connection to a barrel, exchanger, or other apparatus which may support the reactor head. The large weld neck or lap joint flange is often very expensive to design and produce and the sealing surface must be carefully maintained to ensure a proper seal between the reactor and, for example, the barrel. The maintenance of the connection surface is very important when the reactor is in operation and contains potentially hazardous, high temperature chemicals such as the HCN present in the Andrussow process. When it becomes necessary to move the reactor head for maintenance or other reasons, operators must be extremely careful to protect the flange from damage so that the reactor can be quickly put back into service. Often an operator will simply set the reactor on a block of wood, a pad, or some other material to protect the flange; and although a block of wood or other pad may sometimes be sufficient to protect the flange from damage when properly placed, if the operator fails to block the flange and sets the reactor head directly onto typical plant grating, the weight of the reactor head on the flange surface will most likely render it unusable (if the flange surface is scratched or warped, it will not seal properly).
Finally, the physical elevation of a typical barrel upon which the reactor head rests creates a difficulty in inserting and removing items such as catalysts, distributors, supports, or any other assemblies intended to be placed inside the barrel. Often the wall of the barrel is four feet high or more, requiring an operator to climb onto a platform, over the wall, and physically enter the barrel to install or exchange the catalyst. Not only does it take time to climb into and out of the barrel, but the barrel is classified as a confined space, and entry into a confined space requires the acquisition of permits, a supply of breathing air, availability and attention of another worker to serve as hole watcher, and sometimes other expensive and time-consuming safety precautions. There is a perceived need for a design that eliminates the need for these precautions and eases the installation of the catalyst.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the issues set forth above.
In one embodiment an apparatus for a high-temperature industrial process includes at least one flanged connection, with at least one flange of the at least one flanged connection protected from mechanical damage by at least one support lug attached to the at least one flange is disclosed. The apparatus of may further include a cooling jacket attached to the at least one flange, the cooling jacket being made of a ½ pipe.
In another embodiment there is described an apparatus for a high-temperature industrial process including at least one flanged connection, wherein the flange is cooled by an attached ½ pipe cooling jacket.
In some embodiments an apparatus for a high-temperature industrial process includes an inlet piping section with a first cross-sectional dimension, a downstream process section with a second cross-sectional dimension, and an inlet transition section connecting the inlet piping section and downstream process section, with the transition section including internal insulation made of refractory ceramic fiber. The second cross-sectional dimension may be larger than the first cross-sectional dimension, and the internal insulation may form a conical interior surface. In addition, the inlet transition section may be formed to a domed geometry. The transition section may be a reactor head including a flanged connection to the downstream process section.
In some embodiments there is included one or more sight glass nozzles. A laminar velocity profile may also achieved in the downstream process section using at least one of: a sufficient length of straight pipe comprising the inlet piping section to provide laminar flow at an upstream end of the inlet transition section; at least one CRV disposed within the inlet piping section; an LAD at the upstream end of the inlet transition section; and an EHD at the upstream end of the inlet transition section.
Another embodiment for a high temperature industrial process includes a process section having a first cross-sectional dimension, outlet piping having a second cross-sectional dimension smaller than the first cross-sectional dimension; and an outlet transition section connecting the outlet piping section and the process section with an internal surface of the outlet transition section which is conical.
Still another embodiment for a high-temperature industrial process includes a reactor head having a bottom flange, and a downstream process section with a top flange where a working elevation of the downstream process section top flange is between about 2.0 and 3.5 feet.
Another embodiment of the present invention includes an inlet piping section, an inlet transition section, a process section, an outlet transition section, and an outlet piping section where internal insulation is included in one or more of the apparatus sections, and where the insulation comprises refractory ceramic fiber. In this embodiment the inlet transition section further includes a conical interior surface, and the outlet transition section further includes a conical interior surface. The appara
Bergeron David Mark
DeCourcy Michael Stanley
Quintanilla Aaron Angel
Valerio Paul Francis
Vinson, Jr. James Woodrow
Langel Wayne A.
Rohm and Haas Company
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