Patent Description:
Typically, the O2 <NUM> is injected into the conduit <NUM> used through a single pipe and the EnNG <NUM> is injected through several pipes laid out circumferentially. These pipes <NUM>,<NUM> are self-cooled by the flowing gas alone, unless water-cooled pipes are used. The O2 <NUM> and EnNG <NUM> are injected at different locations along the conduit <NUM> to ensure the stable and safe combustion of the O2 <NUM>, as the cooling effect of the EnNG <NUM> may impair the combustion and/or ignition. An inert gas purge <NUM> is fluidly coupled to the O2 injection pipe <NUM>. Generally, the single O2 injection pipe <NUM> incorporates one or two O2 injection nozzles, while the EnNG injection pipe <NUM> is coupled to a circumferential header <NUM> that includes four to eight circumferential injection holes, for example.

In general, this configuration suffers from several important problems:.

Document <CIT> discloses another oxygen injection system for a direct reduction process, where oxygen and natural gas are injected in common ports axially disposed around a conduit.

Thus, an improved O2 and EnNG injection system that solves these problems is needed for DR processes.

In various exemplary embodiments, the present disclosure improves the flow rate flexibility for an O2 injection pipe without applying water-cooling. The number of O2 injection points is increased, such that the O2 and EnNG can be distributed more uniformly in the bustle gas stream. Further, the present disclosure makes it possible to safely inject O2 very close to the point of EnNG injection, such that the partial combustion of the EnNG is enhanced and the temperature of the reducing gas entering the SF is reduced as compared to with a full oxidation configuration.

The present disclosure optimizes the O2/EnNG ratio at the O2 injection location to maximize partial combustion and minimize C deposition. This is achieved by:.

In one exemplary embodiment, the present disclosure provides an oxygen injection system for a direct reduction process, including: a common circumferential gas injection header adapted to be coupled to an oxygen source and an enrichment natural gas source and adapted to deliver oxygen from the oxygen source and enrichment natural gas from the enrichment natural gas source to a reducing gas stream flowing through a conduit axially disposed within the common circumferential gas injection header through a plurality of circumferentially disposed ports to form a bustle gas stream; wherein the common circumferential gas injection header includes a circumferential oxygen injection header adapted to deliver the oxygen from the oxygen source to the reducing gas stream through the plurality of circumferentially disposed ports and a circumferential enrichment natural gas injection header adapted to deliver the enrichment natural gas from the enrichment natural gas source to the reducing gas stream through the plurality of circumferentially disposed ports. The circumferential oxygen injection header and the circumferential enrichment natural gas injection header are axially disposed. The circumferential enrichment natural gas injection header is axially disposed within the circumferential oxygen injection header. The circumferential oxygen injection header includes a plurality of circumferentially disposed pipes adapted to be disposed through the circumferential enrichment natural gas injection header and a plurality of circumferentially disposed nozzles coupled to the plurality of circumferentially disposed pipes adapted to be collocated with the plurality of circumferentially disposed ports. The oxygen flow rate through each of the plurality of circumferentially disposed pipes is variable. Optionally, the enrichment gas flow rate through each of the plurality of circumferentially disposed ports is variable. The oxygen injection system further includes an inert gas purge coupled to the oxygen source. The oxygen injection system further includes a brick orifice circumferentially disposed about the conduit upstream of the common circumferential gas injection header. Optionally, the oxygen injection system further includes another circumferential enrichment natural gas injection header disposed about the conduit downstream of the common circumferential gas injection header and adapted to deliver additional enrichment natural gas from the enrichment natural gas source to the reducing gas stream through an additional plurality of circumferentially disposed ports.

In another exemplary embodiment, the present disclosure provides an oxygen injection method for a direct reduction process, including: providing a common circumferential gas injection header adapted to be coupled to an oxygen source and an enrichment natural gas source and adapted to deliver oxygen from the oxygen source and enrichment natural gas from the enrichment natural gas source to a reducing gas stream flowing through a conduit axially disposed within the common circumferential gas injection header through a plurality of circumferentially disposed ports to form a bustle gas stream; wherein the common circumferential gas injection header includes a circumferential oxygen injection header adapted to deliver the oxygen from the oxygen source to the reducing gas stream through the plurality of circumferentially disposed ports and a circumferential enrichment natural gas injection header adapted to deliver the enrichment natural gas from the enrichment natural gas source to the reducing gas stream through the plurality of circumferentially disposed ports. The circumferential oxygen injection header and the circumferential enrichment natural gas injection header are axially disposed. The circumferential enrichment natural gas injection header is axially disposed within the circumferential oxygen injection header. The circumferential oxygen inj ection header includes a plurality of circumferentially disposed pipes adapted to be disposed through the circumferential enrichment natural gas injection header and a plurality of circumferentially disposed nozzles coupled to the plurality of circumferentially disposed pipes adapted to be collocated with the plurality of circumferentially disposed ports. The oxygen injection method further includes varying an oxygen flow rate through each of the plurality of circumferentially disposed pipes. Optionally, the oxygen injection method further includes varying an enrichment gas flow rate through each of the plurality of circumferentially disposed ports. The oxygen injection method further includes providing an inert gas purge coupled to the oxygen source. The oxygen injection method further includes providing a brick orifice circumferentially disposed about the conduit upstream of the common circumferential gas injection header. Optionally, the oxygen injection method further includes providing another circumferential enrichment natural gas injection header disposed about the conduit downstream of the common circumferential gas injection header and adapted to deliver additional enrichment natural gas from the enrichment natural gas source to the reducing gas stream through an additional plurality of circumferentially disposed ports.

Again, in various exemplary embodiments, the present disclosure improves the flow rate flexibility for an O2 injection pipe without applying water-cooling. The number of O2 injection points is increased, such that the O2 and EnNG can be distributed more uniformly in the bustle gas stream. Further, the present disclosure makes it possible to safely inject O2 very close to the point of EnNG injection, such that the partial combustion of the EnNG is enhanced and the temperature of the reducing gas entering the SF is reduced as compared to with a full oxidation configuration.

Referring now specifically to <FIG>, in one exemplary embodiment, the common O2 and EnNG inj ection system <NUM> of the present disclosure utilizes coaxial O2 <NUM> and EnNG <NUM> injection at the same location, through a common circumferential injection header <NUM> disposed around the reducing gas conduit <NUM>, thereby forming bustle gas <NUM> that is delivered to the SF. The common circumferential injection header <NUM> includes an outer circumferential O2 injection header <NUM> and an inner circumferential EnNG injection header <NUM> that collectively utilize a plurality of common circumferential gas injection ports <NUM>. In this exemplary embodiment, each of the O2 injection pipes <NUM> is disposed along a radius of the common circumferential injection header <NUM> through the inner circumferential EnNG injection header <NUM>, and collocated with and protruding through one of the circumferential EnNG injection ports <NUM>. An inert gas purge <NUM> is coupled to the O2 <NUM> as before.

Thus, the O2 pipe <NUM> is cooled by the EnNG shroud gas coming out of the circumferential holes <NUM> of the EnNG header <NUM> installed on the bustle gas duct <NUM>. This allows more flexibility and turndown capability (including zero flow) of the O2 flow rate for each O2 injection pipe <NUM>.

The flexibility of this O2 flow makes it possible to increase the number of O2 and EnNG injection points circumferentially and distributes O2 and EnNG more uniformly in the bustle gas stream <NUM>. Further, it provides the flexibility to stop the O2 flow to some of the O2 injection pipes <NUM> without removing them from the system <NUM>.

By applying smaller diameter O2 injection pipes <NUM> inside the larger diameter EnNG shroud gas hole <NUM> to maintain higher gas velocity for the O2 than that of the EnNG, stable O2 combustion can be achieved without being influenced by the cooling effect of the EnNG. This makes it possible to safely inject the O2 close to the injection point of the EnNG in the reducing gas duct <NUM>.

The EnNG shroud gas coming out of the shroud gas hole <NUM> protects the refractory-lined duct wall around the O2 pipes <NUM> from the radiation heat of the O2 flame, even though the projection of the O2 pipes <NUM> from the refractory wall is minimal. Such minimal projection thereby extends the life of the O2 injection pipes <NUM>.

A brick orifice <NUM> or the like is disposed upstream of the common circumferential header <NUM> and prevents turbulent flow around the O2/EnNG injection location. This coaxial O2/EnNG injection configuration coupled with the brick orifice <NUM> disposed upstream significantly enhances the partial combustion of the EnNG <NUM>.

Referring now specifically to <FIG>, in another exemplary embodiment, the common O2 and EnNG injection system <NUM> of the present disclosure again utilizes coaxial O2 <NUM> and EnNG <NUM> injection at the same location, through a common circumferential injection header <NUM> disposed around the reducing gas conduit <NUM>, thereby forming bustle gas <NUM> that is delivered to the SF. The common circumferential injection header <NUM> includes an outer circumferential O2 injection header <NUM> and an inner circumferential EnNG injection header <NUM> that collectively utilize a plurality of common circumferential gas injection ports <NUM>. In this exemplary embodiment, each of the O2 injection pipes <NUM> is disposed along a radius of the common circumferential injection header <NUM> through the inner circumferential EnNG injection header <NUM>, with an O2 nozzle <NUM> collocated with and protruding through one of the circumferential EnNG injection ports <NUM>. An inert gas purge <NUM> is coupled to the O2 <NUM> as before.

Thus, the O2 pipe <NUM> is cooled by the EnNG shroud gas <NUM> coming out of the circumferential holes <NUM> of the EnNG header <NUM> installed on the bustle gas duct <NUM>. This allows more flexibility and turndown capability (including zero flow) of the O2 flow rate for each O2 injection pipe <NUM>.

The flexibility of this O2 flow <NUM> makes it possible to increase the number of O2 and EnNG injection points circumferentially and distributes O2 and EnNG more uniformly in the bustle gas stream <NUM>. Further, it provides the flexibility to stop the O2 flow <NUM> to some of the O2 injection pipes <NUM> without removing them from the system <NUM>.

The EnNG shroud gas <NUM> protects the refractory-lined duct wall around the O2 nozzle <NUM> from the radiation heat of the O2 flame, even though the projection of the O2 pipe <NUM> from the refractory wall is minimal. Such minimal projection thereby extends the life of the O2 injection pipe <NUM>.

Again, a brick orifice <NUM> or the like is disposed upstream of the common circumferential header <NUM> and prevents turbulent flow around the O2/EnNG injection location. This coaxial O2/EnNG injection configuration coupled with the brick orifice <NUM> disposed upstream significantly enhances the partial combustion of the EnNG <NUM>.

Here, a separate downstream circumferential EnNG injection header <NUM> is also coupled to the EnNG supply <NUM> and utilized, injecting the EnNG into the bustle gas stream <NUM> within the duct <NUM> through a plurality of separate circumferential EnNG injection ports <NUM>. In the first embodiment, with the O2/EnNG coaxial injection configuration, C deposition may occur around the O2 injection points if the amount of heavies in the EnNG is high or if the EnNG/O2 flow ratio is high. Dividing the EnNG injection into two locations (one around the O2 injection location and another at a location downstream) allows to O2/EnNG ratio at the O2 injection location to be optimized to maximize the partial combustion and minimize the C deposition. The optimum ratio is O2/EnNG = <NUM> ~ <NUM>, or preferably <NUM> ~ <NUM>, on a molar/volume basis.

Thus, again, the present disclosure improves the flow rate flexibility for an O2 injection pipe without applying water-cooling. The number of O2 injection points is increased, such that the O2 and EnNG can be distributed more uniformly in the bustle gas stream. Further, the present disclosure makes it possible to safely inject O2 very close to the point of EnNG injection, such that the partial combustion of the EnNG is enhanced and the temperature of the reducing gas entering the SF is reduced as compared to with a full oxidation configuration.

Claim 1:
An oxygen injection system for a direct reduction process, comprising:
a common circumferential gas injection header adapted to be coupled to an oxygen source and an enrichment natural gas source and adapted to deliver oxygen from the oxygen source and enrichment natural gas from the enrichment natural gas source to a reducing gas stream flowing through a conduit axially disposed within the common circumferential gas injection header through a plurality of circumferentially disposed ports to form a bustle gas stream;
characterized in that the common circumferential gas injection header is formed by a circumferential oxygen injection header adapted to deliver the oxygen from the oxygen source to the reducing gas stream through the plurality of circumferentially disposed ports and a circumferential enrichment natural gas injection header adapted to deliver the enrichment natural gas from the enrichment natural gas source to the reducing gas stream through the plurality of circumferentially disposed ports; and
wherein the circumferential enrichment natural gas injection header is axially disposed within the circumferential oxygen injection header.