Method for preparing a sorbent

Abstract

A method is described for preparing a sorbent including the steps of: (i) mixing together a particulate copper sulphide material, a particulate support material and one or more binders, (ii) shaping the mixture, and (iii) drying the shaped mixture to form a dried sorbent.

Claims

1. A method for preparing a sorbent comprising the steps of: (i) mixing a particulate copper sulphide material, a particulate support material and one or more binders to form a mixture, (ii) shaping the mixture by granulating the mixture in a granulator, and (iii) drying the shaped mixture to form a dried sorbent, and wherein the shaping comprises granulating the mixture in a granulator using a liquid and the amount of liquid is 0.1 to 0.5 mL/g of mixture.

2. The method according to claim 1 wherein the particulate copper sulphide material is manufactured by roasting copper or a copper compound with elemental sulphur, precipitating copper sulphide from solution, sulphiding a copper compound using hydrogen sulphide, or mixing powdered copper metal with elemental sulphur under conditions that cause the elemental copper and elemental sulphur to react to form one or more copper sulphides.

3. The method according to claim 1 wherein the copper sulphide comprises one or more copper sulphides that are copper (II) sulphide, CuS, or substoichiometric copper sulphides of formula Cu.sub.2-xS where x is 0-1.

4. The method according to claim 1 wherein the particulate copper sulphide has an overall S:Cu atomic ratio of 0.8.

5. The method according to claim 4 wherein the particulate copper sulphide has an overall S:Cu atomic ratio of 0.9.

6. The method according to claim 4 wherein the particulate copper sulphide has an overall S:Cu atomic ratio of 0.95.

7. The method according to claim 1 wherein the particulate copper sulphide material is in the form of a powder with an average particle size, [D.sub.50], in the range 5-100 m.

8. The method according to claim 7, wherein the particulate copper sulphide material is in the form of a powder with a D.sub.50 in the range of 10-50 m.

9. The method according to claim 1 wherein the copper content of the dried sorbent is in the range 10-75% by weight, expressed as CuS.

10. The method according to claim 9 wherein the copper content of the dried sorbent is in the range of 15-50% by weight.

11. The method according to claim 1 wherein the particulate support material is alumina, hydrated alumina, titania, zirconia, silica, aluminosilicate, or a mixture thereof.

12. The method according to claim 1 wherein the dried sorbent comprises 20-60% by weight of the particulate support material.

13. The method according to claim 1 wherein the binder is a clay binder, cement binder, or organic polymer binder.

14. The method according to claim 1 wherein the binder is a combination of a cement binder and a clay binder.

15. The method according to claim 14 wherein the relative weights of the cement binder and clay binder is in the range of 1:1 to 3:1.

16. The method according to claim 1 wherein the total amount of the binder in the dried sorbent is in the range of 5-30% by weight.

17. The method according to claim 1 wherein the total metal sulphide content of the sorbent, other than copper sulphide, is 5% wt.

18. The method according to claim 1 wherein the sorbent is dried at a temperature up to 120 C.

19. The method according to claim 1 wherein the total metal sulphide content of the sorbent, other than copper sulphide, is 1% wt.

Description

EXAMPLE 1. PREPARATION OF SORBENT

(1) A dry powder mix was prepared according to the following recipe (all parts by weight).

(2) 139 parts copper sulphide, (reagent grade 99.8% CuS, D.sub.50 42 m)

(3) 233 parts aluminium trihydrate (D.sub.50 10 m)

(4) 64 parts Ciment Fondu (calcium aluminate)

(5) 64 parts Attagel 50 (attapulgite clay)

(6) The dry powders were mixed to ensure homogeneity before employing a granulation technique where the mixed powder was combined with a little water and mixed to form granules in an Eirich mixer. The granules were dried immediately in a laboratory fluid bed drier at 105 C. The resulting dried sorbent product (Sorbent F) contained 27% wt copper sulphide (18% wt copper).

EXAMPLE 2. PREPARATION OF SORBENT

(7) A dry powder mix was prepared according to the following recipe (all parts by weight).

(8) 139 parts copper sulphide, (CuS produced by reacting basic copper carbonate with hydrogen sulphide gas)

(9) 233 parts aluminium trihydrate (D.sub.50 10 m)

(10) 64 parts Ciment Fondu (calcium aluminate)

(11) 64 parts Attagel 50 (attapulgite clay)

(12) The dry powders were mixed to ensure homogeneity before employing a granulation technique where the mixed powder was combined with a little water and mixed to form granules in an Eirich mixer. The granules were dried immediately in a laboratory fluid bed drier at 105 C. The resulting dried sorbent product (Sorbent G) contained 27% wt copper sulphide (18% wt copper).

EXAMPLE 3. PREPARATION OF SORBENT

(13) A dry powder mix was prepared according to the following recipe (all parts by weight).

(14) 139 parts copper sulphide, (CuS produced by mechanochemical reactive milling of elemental copper and elemental sulphur, (CuS D.sub.50 11 m)

(15) 233 parts aluminium trihydrate (D.sub.50 10 m)

(16) 64 parts Ciment Fondu (calcium aluminate)

(17) 64 parts Attagel 50 (attapulgite clay)

(18) The dry powders were mixed to ensure homogeneity before employing a granulation technique where the mixed powder was combined with a little water and mixed to form granules in an Eirich mixer. The granules were dried immediately in a laboratory fluid bed drier at 105 C. The resulting dried sorbent product (Sorbent H) contained 27% wt copper sulphide (18% wt copper).

EXAMPLE 4. GAS-PHASE TESTING

(19) Sorbent F and a comparative sorbent prepared according to the 2-step post-sulphiding method described WO2009/101429 were tested. Granules of each sorbent (2.80-3.35 mm size fraction, volume 25 ml) were placed in a stainless steel reactor (21 mm ID). A flow of 100% vol natural gas was passed through a bubbler containing elemental mercury to allow the gas to pick up the mercury. The mercury-laden gas was then passed downwards through the reactor under the following conditions.

(20) Pressure: 10 barg

(21) Temperature 30 C.

(22) Gas flow 110.2 NL.Math.hr.sup.1

(23) Contact time 8 seconds

(24) Test duration 690 hours

(25) Samples from the reactor inlet and exit were periodically analysed for mercury content by atomic fluorescence detection. The inlet gas had a mercury concentration of about 1100 g/m.sup.3. The sorbents reduced the mercury content of the exit gas to below detectable limits throughout the test. At the end of each test the 25 ml sorbent bed was discharged as 9 discrete sub-beds which were ground completely and analysed by acid digestion/ICP-OES to determine total mercury content. The amount of mercury captured by each sorbent bed is shown in Table 1.

(26) TABLE-US-00001 TABLE 1 Comparative Sorbent F Sorbent Mercury Bed 1 (inlet) 2.13 1.98 Loading, Bed 2 1.15 1.56 wt % Bed 3 0.53 0.95 Bed 4 0.37 0.46 Bed 5 0.15 0.14 Bed 6 0.06 0.05 Bed 7 0.02 0.03 Bed 8 <0.01 <0.01 Bed 9 (exit) <0.01 <0.01

(27) All sorbent F was surprisingly as effective for the removal of mercury as the sorbent prepared with a separate sulphiding step.

EXAMPLE 5. LIQUID-PHASE TESTING

(28) Sorbents G and H and a comparative sorbent prepared according to the 2-step post-sulphiding method described WO2009/101429 were tested; Granules of each sorbent (1.00-2.00 mm size fraction, volume 25 ml) were placed in a glass reactor (19 mm ID). N-hexane liquid saturated with elemental mercury to ca. 1 ppm (w/v) was passed through the bed at ambient temperature (about 25 C.), at a Liquid Hourly Space Velocity (LHSV) of 7.0 hr.sup.1. Samples were taken from the reactor exit line and analysed by atomic fluorescence on a PSA-modified Hewlett Packard 6890 GC to monitor mercury levels. At the end of the test (750 hours), the bed was discharged into 9 equivalent discrete sub-beds by vacuum, which were analysed for total mercury content (w/w) by ICP-Optical Emission Spectroscopy.

(29) TABLE-US-00002 Comparative Sorbent G Sorbent H Sorbent Mercury Bed 1 (inlet) 2.89 3.38 4.57 Loading, Bed 2 1.23 1.52 1.28 wt % Bed 3 0.27 0.30 0.24 Bed 4 0.07 0.07 0.03 Bed 5 0.02 <0.01 <0.01 Bed 6 <0.01 <0.01 <0.01 Bed 7 <0.01 <0.01 <0.01 Bed 8 <0.01 <0.01 <0.01 Bed 9 (exit) <0.01 <0.01 <0.01

(30) Sorbents G and H were surprisingly as effective for the removal of mercury as the sorbent prepared with a separate sulphiding step.