A METHOD FOR THE SUPPRESSION OF SOOT FORMATION IN AN ATR OR POX REACTOR

Abstract

A method for the suppression of soot formation during the partial oxidation of a hydrocarbon-containing gaseous feed, in the presence of steam and in an ATR reactor or in a POX reactor, the method comprising the addition of gaseous carbon dioxide to the hydrocarbon-containing gaseous feed before entry into the reactor. A method for determining a minimum steam to carbon ratio required for scot-free operation is also disclosed.

Claims

1. A method for the suppression of soot formation during the partial oxidation of a hydrocarbon-containing gaseous feed, in the presence of steam and in an ATR reactor or in a POX reactor, the method comprising the addition of gaseous carbon dioxide to the hydrocarbon-containing gaseous feed before entry into the reactor.

2. The method according to claim 1, wherein the ratio m.sub.CO2/m.sub.C of moles of added carbon dioxide over moles of carbon contained in the feed prior to addition of CO2 is at least 0.25.

3. The method according to claim 2, wherein said ratio m.sub.CO2/m.sub.C is in the range 0.25 to 2 and preferably 0.25 to 1.

4. The method according to claim 1, wherein CO2 is added to the hydrocarbon-containing gaseous feed before or after addition of steam.

5. The method according to claim 1, further comprising the step of determining a minimum steam to carbon ratio for soot free operation of the partial oxidation process, according to the following relationship:
(S/C).sub.lim,CO2=(S/C).sub.lim−ζ.Math.(m.sub.CO2/m.sub.C) wherein: (S/C).sub.lim is the minimum steam to carbon ratio for soot-free operation of the process when performed with the gaseous feed without addition of CO2; (S/C).sub.lim,CO2 is the minimum steam to carbon ratio for soot-free operation of the process when performed with addition of CO2 to the gaseous feed; (m.sub.CO2/m.sub.C) denotes the ratio of moles of CO2 added to the feed over the moles of carbon contained in the feed before addition of CO2; ζ is in the range 0.4 to 0.6.

6. The method according to claim 5 wherein the concentration in volume of the soot in the effluent of the partial oxidation process is not greater than 5 ppb.

7. A method for determining a minimum steam to carbon ratio required for soot-free operation in a process of partial oxidation of a hydrocarbon-containing gaseous feed, wherein said process of partial oxidation is carried out in the presence of steam in an ATR reactor or in a POX reactor, and wherein said gaseous feed is added with carbon dioxide before entry into the reactor, wherein the minimum steam to carbon ratio for soot-free operation in the presence of added CO2 is determined as:
(S/C).sub.lim,CO2=(S/C).sub.lim−ζ.Math.(m.sub.CO2/m.sub.C) wherein: (S/C).sub.lim is the minimum steam to carbon ratio for soot-free operation of the process when performed with the gaseous feed without addition of CO2; (S/C).sub.lim,CO2 is the minimum steam to carbon ratio for soot-free operation of the process when performed with addition of CO2 to the gaseous feed; (m.sub.CO2/m.sub.C) denotes the ratio of moles of CO2 added to the feed over the moles of carbon contained in the feed before addition of CO2; ζ is in the range 0.4 to 0.6.

8. The method according to claim 7 wherein the concentration in volume of the soot in the effluent of the partial oxidation process is not greater than 5 ppb.

9. A method for controlling a partial oxidation process in an ATR or POX reactor, the process being carried out in the presence of steam and with addition of carbon dioxide to a hydrocarbon-containing gaseous feed of the process, the method including the determination of a minimum steam to carbon ratio for soot free operation according to claim 7.

Description

[0036] The benefit of the invention is elucidated by FIG. 1 and FIG. 2, wherein:

[0037] FIG. 1 is a plot of soot concentration Vs. steam to carbon ratio for a process of partial oxidation performed at 15 bar pressure, using methane (CH4) as fuel and in the presence of oxygen to carbon (O2/C) ratio of 0.5;

[0038] FIG. 2 is a plot of soot concentration Vs. steam to carbon ratio for a process of partial oxidation as in FIG. 1 with oxygen to carbon (O2/C) ratio of 0.6.

[0039] In FIG. 1, the plot I relates to a base case without addition of CO2 to the feed and the plot II relates to the same process as in the base case, with addition of CO2 to the feed gas in an amount such that m.sub.CO2/m.sub.C is 0.25.

[0040] In FIG. 2, the plot I relates to a base case without addition of CO2 to the feed; the plot II relates to addition of CO2 such that m.sub.CO2/m.sub.C=0.25 and plot III relates to m.sub.CO2/m.sub.C=0.66.

[0041] All plots of FIG. 1 and FIG. 2 illustrate that the comparative base case starts to form soot at higher S/C values. In other words, the addition of CO2 reduces the soot critical S/C, which means the process can be operated at a lower S/C to save steam without incurring in the soot formation. FIG. 2 illustrates that adding more carbon dioxide further reduces the critical S/C, as can be seen from a comparison of plots II and III.