Furnace suited for chemiluminescent sulphur detection

Abstract

The invention is directed to a furnace suited for oxidation of a gaseous starting mixture comprising one or more sulphur compounds to obtain an oxidized gas mixture and reduction of the oxidized gas mixture to obtain a gaseous mixture of reduced sulphur compounds comprising an interior furnace space, an inlet conduit for the gaseous starting mixture, an inlet for supply of an oxygen comprising gas, a ceramic comprising outlet conduit provided with an inlet opening for the mixture of reduced sulphur compounds, an inlet for hydrogen and heating means, wherein the inlet opening of the outlet conduit is comprised of more than one opening which openings fluidly connect the interior furnace space and the interior of the outlet conduit.

Claims

1. A furnace suited for oxidation of a gaseous starting mixture comprising one or more sulphur compounds to obtain an oxidized gas mixture and reduction of the oxidized gas mixture to obtain a gaseous mixture of reduced sulphur compounds comprising: an interior furnace space, an inlet conduit for the gaseous starting mixture, an inlet for supply of an oxygen comprising gas, a ceramic comprising outlet conduit provided with an inlet opening for the mixture of reduced sulphur compounds, an inlet for hydrogen, and a heating element, wherein the inlet opening of the outlet conduit is comprised of more than one opening which openings fluidly connect the interior furnace space and the interior of the outlet conduit.

2. A furnace according to claim 1, wherein the inlet opening of the outlet conduit is comprised of at least four openings.

3. A furnace according to claim 2, wherein the inlet opening of the outlet conduit is comprised of at least five openings and at most 50 openings.

4. A furnace according to claim 1, wherein the outlet conduit is a tube tubular outlet conduit which is provided with a circular end wall at its end and wherein the more than one opening of the inlet opening of the tubular outlet conduit are openings in said circular end wall.

5. A furnace according to claim 1, wherein the inlet conduit for the gaseous starting mixture is fluidly connected to an inlet for a make-up gas defining a mixing zone for the gaseous starting mixture and the make-up gas upstream the inlet conduit for the gaseous starting mixture and wherein the inlet for make-up gas is provided with a constant pressure valve to achieve a constant pressure in the mixing zone.

6. A furnace according to claim 1, wherein the inlet conduit for the gaseous mixture co-axially protrudes into one end of a larger conduit and the outlet conduit for the mixture of reduced sulphur compounds protrudes into the opposite end of the larger conduit such that the facing ends of the inlet conduit and the outlet conduit are spaced away from each other defining an intermediate zone separating an oxidation zone from a reduction zone and wherein the heating element is positioned at the exterior of the larger conduit.

7. A furnace according to claim 6, wherein a first annular space is present between the interior of the larger conduit and the exterior of the inlet conduit and wherein the inlet for supply of the oxygen comprising gas is positioned at one end of the first annular space such that in use a stream of oxygen comprising gas flows from the inlet for supply of the oxygen comprising gas through the first annular space towards the intermediate zone and wherein a second annular space is present between the interior of the larger conduit and the exterior of the outlet conduit for the mixture of reduced sulphur compounds and wherein the inlet for hydrogen is positioned at one end of the second annular space such that in use a stream of hydrogen flows from the inlet for hydrogen through the second annular space towards the intermediate zone.

8. A furnace according to claim 7, wherein the outlet conduit is a tubular outlet conduit which is provided with a circular end wall at its end and facing the intermediate zone and wherein the more than one opening of the inlet opening of the tubular outlet conduit are openings in said circular end wall.

9. A furnace according to claim 6, wherein at least two heating elements are present along the length of the larger conduit, and wherein the heating elements are configured to independently from each other heat the exterior of the larger conduit such that the temperature in the oxidation zone is different from the temperature in the reduction zone.

10. A furnace according to claim 1, wherein the ceramic of the ceramic comprising outlet conduit is silica, alumina, zirconia, silica-alumina, alumina-silicate or magnesium-alumina-silicate.

11. A furnace according to claim 10, wherein the ceramic of the ceramic comprising outlet conduit is magnesium-alumina-silicate.

12. A furnace according to claim 1, wherein the ceramic of the ceramic comprising outlet conduit is cordierite.

13. A system for chemiluminescent sulphur detection comprising a gas chromatograph, a furnace according to claim 1, an ozone generator and an optical detector.

Description

(1) FIG. 1 shows a furnace according to the invention having a steel inlet tube (1) for the gaseous starting mixture, an inlet (2) for supply of an oxygen comprising gas, a ceramic outlet tube (3) for the mixture of reduced sulphur compounds, an inlet (4) for hydrogen, heating means (5). The steel inlet tube (1) for the gaseous starting mixture is co-axially protruding one end (7) of a larger tube (8). The outlet tube (3) protrudes the opposite end (9) of the larger tube (8) such that the facing open ends (10, 11) of the inlet tube (1) and the outlet tube (3) are spaced away from each other defining an intermediate zone (12) separating an oxidation zone (13) from a reduction zone (14) and wherein the heating means (5) are positioned at the exterior of the larger tube (8). An inlet (6) for supply of a make-up gas and hydrogen is shown which fluidly connects at a mixing zone (17) upstream the steel inlet tube (1) for the gaseous starting mixture. The arrows indicate the flow direction.

(2) FIG. 1 also shows a first annular space (15) present between the interior of the larger tube (8) and the exterior of the inlet tube (1) and wherein the inlet (2) for supply of an oxygen comprising gas is positioned at one end of the first annular space (15) such that in use a stream of oxygen comprising gas flows from the inlet (2) for supply of an oxygen comprising gas through the first annular space (15) towards the oxidation zone (13) and intermediate zone (12). A second annular space (16) is present between the interior of the larger tube (8) and the exterior of the outlet tube (3) for the mixture of reduced sulphur compounds. The inlet (4) for hydrogen is positioned at one end of the second annular space (16) such that in use a stream of hydrogen flows from the inlet (4) for hydrogen through the second annular space (16) towards the reduction zone (14) and intermediate zone (12).

(3) FIG. 2b shows the upstream end of the ceramic outlet tube (3) of FIG. 1. Open end (11) is provided with a circular end wall (18). This circular and ceramic end wall (18) is provided with 19 openings (19) (not exactly drawn to scale). These openings (19) fluidly connect the interior furnace space and the interior (20) of the outlet conduit (3). Further shown is the axially extending side wall (21) of tube (3). FIG. 2a shows view A of FIG. 2b. In this Figure the 19 openings (19) can be clearly seen as present in circular and ceramic end wall (18). The end wall (18) faces the intermediate zone (12). The hydrogen flowing via second annular space (16) towards end (11) will contact the oxidized gas mixture while entering openings (19). The design as shown in FIGS. 2a and 2b ensures that a substantially evenly divided stream of hydrogen and oxidized gas mixture enters openings (19). The evenly distribution of flow may even be further improved by combining openings (19) with different sized openings. The larger sized openings are positioned such that the flow path from the annular space (16) for hydrogen to these openings is larger than the flow path for hydrogen flowing through the smaller sized openings (19).

(4) FIG. 3 shows a sulphur detection system for detecting sulphur in a sample (27) to be analysed. Shown is a gas chromatograph (GC)(28) to which a sample (27) is fed. The sample (27) may be a liquid sample, like for example a sulphur containing crude oil derived fraction, which will be quickly heated in the GC to fully evaporate. The different components will be separated in the capillary column of the GC (28) and in time be supplied as the starting mixture (29) to a furnace (30) according to the present invention. Furnace (30) may be a furnace as shown in FIG. 1. In the furnace steps (a), (b) and (c) of the method according to the invention will take place. An effluent (22) comprising sulphur compound is fed to an optical detector (23) in which step (d) takes place. To optical detector (23) ozone is fed as generated in ozone generator (24). In the optical detector (23) the sulphur compounds react with ozone to sulphur compounds in excited state which create chemiluminescence which in turn is detected by a photo sensitive device as part of detector (23). The output of detector (23) is an electrical signal (25) being a measure for the sulphur concentration in the injected liquid sample (18). The reaction products are continuously discharged from optical detector (23) by means of a vacuum pump (26). The invention is also directed to a system for chemiluminescent sulphur detection as illustrated in FIG. 3 comprising a gas chromatograph, a furnace according to the invention, an ozone generator and an optical detector.

EXAMPLE

(5) In a test set-up as shown in FIG. 3 two alumina outlet tubes (B,C) were compared. Outlet tube B is an outlet tube according to the prior art and has a single opening which fluidly connects the interior furnace space and the interior of the outlet tube B. Outlet tube C is an outlet tube according to the present invention as illustrated in FIG. 2 wherein 21 openings (19) fluidly connect the interior furnace space and the interior (20) of the outlet tube C. The dimensions of the outlet tube B and C are given in the below Table, wherein OD is the tube outer diameter and ID is the diameter of the opening or openings fluidly connecting the interior furnace space and the interior of the outlet tube interior of the outlet tube. The different outlet tubes B and C were tested in the same furnace using the same test samples for a comparable period of time. The Stability, Sensitivity, Equimolarity, Selectivity and Linearity were measured and the results are provided in the below Table. One “+” means a result equal to the results for the prior art tubes A and B. A “+++” means an improvement in that properties as compared to the results for the prior art tubes A and B.

(6) TABLE-US-00001 Design B C OD (mm) 5.0 5.0 Number of Openings 1 21 Diameter opening (mm) 1.5 0.5 Results Stability + +++ Sensitivity + ++ Equimolarity + + Selectivity + ++ Linearity + +++