Method for loading particulate sorbent material

Abstract

A method for loading an adsorbent material, comprising the step of forming a bed of particulate copper sulfide adsorbent in a reaction vessel in an oxygen-containing atmosphere, the particulate copper sulfide adsorbent having a D in the range of 5 to 100 μm 50 and containing more than 5% by weight of copper sulfide powder having an average particle size and an average CuS crystallite size in the range of 25 to 60 nm determined by XRD, is described.

Description

Technical Field

[0001] The present invention relates to a method for loading a particulate copper sulfide sorbent into a container in which it is to be used.

Background Art

[0002] Heavy metals such as mercury are found in small amounts in fluid streams such as hydrocarbon or other gas and liquid streams. Mercury, in addition to its toxicity, can cause failure of aluminum heat exchangers and other processing equipment. Therefore, it is necessary to efficiently remove these metals from fluid streams. Copper sulfide-containing sorbents are commercially used to remove heavy metals from fluid streams such as hydrocarbon streams in refineries and natural gas. The reaction for capturing mercury using a copper sulfide sorbent can be represented as follows. 2CuS + Hg → Cu2S + HgS

[0003] Copper sorbents have conventionally been extruded compositions formed by impregnating a copper salt on a carrier, or particulate compositions containing copper oxide or basic copper carbonate, which are sulfided to form copper sulfide. For example, International Publication No. 2009 / 101429 (A1) discloses a method for producing an absorbent comprising: (i) forming a composition comprising a particulate copper compound capable of forming copper sulfide, a particulate carrier material, and one or more binders; (ii) forming the composition into an absorbent precursor; (iii) drying the absorbent precursor material; and (iv) sulfiding the precursor to form the absorbent. The final sulfiding step may be carried out on-site, i.e., in the reaction vessel in which the adsorbent is used, or off-site in a sulfiding vessel, and the sulfided adsorbent containing copper sulfide is then loaded into the reaction vessel in which it is to be used.

[0004] Loading a reaction vessel with a pre-sulfurized sorbent has the drawback that copper(II) sulfide can react with oxygen and moisture to form copper sulfite and copper sulfate even under ambient conditions. This reduces the effectiveness of the sorbent and can potentially lead to dangerous self-heating during the loading of the copper sulfide sorbent into the reaction vessel. As a result, the loading of copper sulfide sorbents is routinely carried out using an inert atmosphere, typically a nitrogen atmosphere. This requires the operator to have a reliable source of an appropriate inert gas for loading the adsorbent into the reaction vessel and has the drawback that the operator engaged in the loading operation within the reaction vessel is required to wear a breathing apparatus. Alternative methods of in-situ sulfidation also have disadvantages as they require a reliable source of an appropriate sulfiding compound and an additional step for the operator to perform before bringing the reaction vessel online. Therefore, there is a need for a loading method that overcomes these problems.

Summary of the Invention

[0005] The applicant has surprisingly found that when the copper(II) sulfide crystals in the sorbent exceed a certain size, the reaction with oxygen and moisture is suppressed and self-heating can be completely avoided.

[0006] Accordingly, the present invention provides a method for loading a sorbent material, the method comprising forming a bed of particulate copper sulfide sorbent in a reaction vessel in an oxygen-containing atmosphere, the particulate copper sulfide sorbent comprising more than 5 wt% of copper sulfide powder having an average particle size in the range of 5 - 100 μm and an average CuS crystallite size in the range of 25 - 60 nm as determined by XRD. 50 The method advantageously enables the operator to load the particulate copper sulfide sorbent into the vessel under air.

[0007]

[0008] ​This method relates to loading a particulate copper sulfide sorbent into a reaction vessel to form a bed. Such a bed, also known as a fixed bed, may be configured for axial or radial flow. The method can be applied to any axial or radial flow reaction vessel. The reaction vessel in this method is a vessel in which an adsorbent is used to remove heavy metals from a process fluid. The reaction vessel may be of any shape, but is typically a cylindrical vessel with a domed end. The vessel can have a length in the range of 1 to 15 meters, more typically 2 to 10 meters. The diameter can be in the range of 0.5 to 6 meters. Thus, the bed can have a volume in the range of about 1.5 to 300 m 3 The self-heating is particularly a problem for large beds exceeding 10 m 3 .

[0009] Preferably, the sorbent is loaded into the vessel as one or more fixed beds by this method. Two or more beds may be loaded into the reaction vessel, and the beds may have the same or different compositions.

[0010] The reaction vessel is typically installed vertically such that there are upper and lower ends. The loading can be done by pouring the particulate copper sulfide sorbent through the upper opening or by transporting the sorbent through an opening from outside the vessel. The loading may be by sock loading, pneumatic loading, loading via CHEP bins, loading from bags or drums, or loading via a loading tube or chute. Such loading techniques are known, but unlike conventional methods, the method of the present invention does not require the reaction vessel to be initially filled with an inert gas such as nitrogen.

[0011] The loading is carried out in an oxygen-containing atmosphere. This includes an atmosphere containing air or air diluted with an inert gas such as nitrogen, or consisting of them. The method also typically includes loading the plant with nitrogen having an oxygen content of 1 to 5 volume %. This method can also be used for an oxygen-enriched air atmosphere. Preferably, the oxygen content of the oxygen-containing atmosphere is in the range of 1 to 25 volume %.

[0012] The filling method may be carried out at an ambient temperature, for example, a temperature in the range of 5 to 40 °C, but more preferably it can be carried out in the range of 10 to 30 °C.

[0013] The relative humidity may be up to 100%.

[0014] This method requires a particulate copper sulfide sorbent. The "sorbent" includes both "absorbent" and "adsorbent". The copper sulfide sorbent used in this method has a relatively large copper(II) sulfide (CuS) crystallite size. The present applicants have found that this crystallite size is larger than that of conventional copper sulfide sorbents formed using a pre-sulfidation step as described, for example, in the aforementioned International Publication No. WO 2009 / 101429. Rather, the sorbent useful in this method is produced using pre-formed copper sulfide.

[0015] The pre-formed copper sulfide used to prepare the adsorbent may be commercially supplied or may be prepared by many methods. Suitable methods include roasting of copper or copper compounds with elemental sulfur, solvothermal methods, hydrothermal methods (e.g., microwave irradiation), electrodeposition techniques, precipitation of copper sulfide from solution, sulfidation of copper compounds with hydrogen sulfide, those by electron irradiation, or by mechanochemical methods in which powdered copper metal is mixed with elemental sulfur under conditions to react elemental copper and elemental sulfur to form one or more copper sulfides. Such methods are described in Materials Research Bulletin, vol 30, no 12, p1495 - 1504, 1995. Examples of copper sulfide include copper(II) sulfide, CuS, (covellite), and for example, those of the formula Cu where x is from 0 to 1 such as Cu9S5 (digenite) 2-xIt may contain stoichiometric copper sulfide of S. Copper sulfide with more CuS is preferred, and the overall S:Cu atomic ratio of particulate copper sulfide in the sorbent is preferably ≥0.8, more preferably ≥0.9, and most preferably ≥0.95. Desirably, essentially all of the copper sulfide in the sorbent is in the form of copper(II) sulfide, CuS. The copper sulfide in the sorbent is provided as a powder combined with other components of the sorbent. The copper sulfide powder in the sorbent has an average particle size in the range of 5 - 100 μm, preferably 5 - 50 μm, that is, D 50 has. The term average particle size, or volume median diameter D[v,0.5], may also be referred to as D50 or D0.5 and is defined by Dr. Alan Rawle in the paper "Basic Principles of Particle Size Analysis" available from Malvern Instruments Ltd (Malvern, UK) (www.malvern.co.uk). For example, it can be conveniently calculated from particle size analysis achieved by laser diffraction in accordance with ISO13320 using a Malvern Mastersizer (registered trademark).

[0016] The average crystallite size of CuS in the particulate copper sulfide sorbent is in the range of 25 - 60 nm, preferably 30 - 55 nm. The average crystallite size can be determined by X-ray diffraction (XRD) using known methods. A particularly suitable method is to use a Bruker D8 Advance XRD instrument equipped with a Lynxeye PSD detector at a CuK wavelength of 1.5406 Å. The Rietveld method and Scherrer's line broadening are common methods for XRD crystallite size determination. Either method may be used, but the Rietveld method takes into account the entire pattern and is preferred.

[0017] The copper sulfide content of the sorbent is 5 wt% or more. The copper sulfide content can be in the range of 5 - 55 wt% (expressed as CuS), but the inventors have found that materials with low levels of copper sulfide can be as effective at capturing heavy metals as conventional sorbent materials. Thus, the copper sulfide content of the sorbent may be in the range of 5 - 45 wt%, preferably 5 - 25 wt%, more preferably 5 - 20 wt% (expressed as CuS). This may have been expected to produce sorbents with lower performance as a result of the smaller CuS surface area despite the large CuS crystallite size.

[0018] The sorbent may further comprise a carrier material and / or one or more binders. The carrier material provides a surface on which the copper sulfide particles can be dispersed, and the one or more binders hold the particles together and provide the desired strength to withstand the loading process and subsequent use.

[0019] The particulate copper sulfide sorbent may contain 20 - 60 wt% of a particulate carrier material to disperse the copper sulfide particles. The particulate carrier material, if present, may be any inert carrier material suitable for use in the preparation of the sorbent. Such carrier materials include alumina, metal aluminates, silica, silicon carbide, titania, zirconia, zinc oxide, aluminosilicates, zeolites, metal carbonates, carbon, or mixtures thereof. The particulate carrier material is preferably an oxide material such as alumina, titania, zirconia, silica, and aluminosilicates, or a mixture of two or more thereof. Hydrated oxides such as alumina trihydrate or boehmite can also be used. Particularly preferred particulate carrier materials are alumina and hydrated alumina, especially alumina trihydrate. The particulate carrier material may have a D 50 particle size in the range of 1 - 100 μm, particularly 5 - 20 μm.

[0020] The particulate copper sulfide sorbent may contain one or more binders for binding the copper sulfide particles and, optionally, may also contain a carrier material in the sorbent. The binders may include clay binders such as bentonite, sepiolite, attapulgite clay, cement binders, particularly calcium aluminate cements such as cement fondu, organic polymer binders such as cellulose binders, or mixtures thereof. Particularly strong sorbent particles can be formed when the binder is a combination of a cement binder and a clay binder. In such materials, the relative weight of the cement binder to the clay binder may be in the range of 3:1 to 1:5.

[0021] Alternatively, the binder may consist of particulate fired rehydratable alumina, which can function usefully as both a binder and a carrier material. The term "fired rehydratable alumina" means a fired amorphous or low-crystalline transition alumina containing one or more of ρ-alumina, χ-alumina, and pseudo-γ-alumina. Such alumina can be rehydrated and can retain a significant amount of water in a reactive form. Fired rehydratable alumina is commercially available, for example, as "CP alumina powder" available from BASF AG. They can be prepared, for example, as described in U.S. Patent No. 2,915,365, by grinding gibbsite (Al(OH)3) to a particle size of 1 to 20 microns and subsequently flash-firing for a short contact time. In addition to gibbsite, amorphous aluminum hydroxide and other naturally occurring inorganic crystalline hydroxides (e.g., bayerite and nordstrandite) or monohydroxides (e.g., boehmite (AlOOH) and diaspore) can also be used as sources of fired rehydratable alumina.

[0022] The copper sulfide in the sorbent may be distributed throughout the sorbent particles or may be provided as a coating on the surface of a particulate carrier formed as a so-called eggshell layer. This method has been found to be particularly suitable for eggshell sorbents, despite the fact that more copper sulfide is exposed to an oxygen-containing atmosphere.

[0023] Particularly preferred methods for preparing particulate copper sulfide sorbents that can be used in the loading method of the present invention are disclosed in WO 2015 / 092359 (A1), WO 2015 / 092360 (A1), WO 2016 / 193659 (A1), and WO 2016 / 193660 (A1).

[0024] Thus, sorbents suitable for use in the loading method of the present invention can be prepared by one of the following methods.

[0025] Method 1 (i) Mixing together a particulate copper sulfide material, a particulate carrier material, and one or more binders; (ii) Shaping the mixture; and (iii) Drying the shaped mixture to form a dried sorbent.

[0026] Method 2 (i) Mixing a particulate copper sulfide material with particulate calcined rehydratable alumina; (ii) Shaping the mixture; and (iii) Drying the shaped mixture to form a dried sorbent.

[0027] Method 3 (i) Mixing together a particulate carrier material and one or more binders to form a carrier mixture; (ii) Shaping the carrier mixture by granulating in a granulator to form aggregates; (iii) Coating the aggregates with a powder of a coating mixture comprising particulate copper sulfide and one or more binders to form coated aggregates; and (iv) Drying the coated aggregates to form a dried sorbent.

[0028] Method 4 (i) Forming aggregates containing particulate carrier material; (ii) Coating the aggregates with a powder of a coating mixture comprising particulate copper sulfide and particulate calcined rehydratable alumina to form coated aggregates, and (iii) Drying the coated aggregates to form a dried sorbent.

[0029] The copper sulfide sorbent used in this process is particulate. The sorbent particles may be by pelletization, extrusion or granulation. Thus, sorbent pellets can be formed by shaping a powder composition generally containing a material such as graphite or magnesium stearate as a molding aid in a mold of appropriate size, for example as in a conventional tableting operation. Alternatively, sorbent extrudates can be formed by passing an appropriate composition, often with a small amount of water and / or a molding aid as described above, through a die and subsequently cutting the material emerging from the die into short lengths. For example, the extrudates may be made using a type of pellet mill used for pelletizing animal feed, where the mixture to be pelletized is filled into a rotating perforated cylinder and through its perforations the mixture is pushed forward by a rod or roller within the cylinder. The resulting extruded mixture is cut from the surface of the rotating cylinder by a doctor knife arranged to give extruded pellets of the desired length. Alternatively, sorbent granules in the form of aggregates may be formed by mixing a powder composition with a liquid such as a small amount of water insufficient to form a slurry and then aggregating the composition into substantially spherical granules in a granulator. Suitable granulators are commercially available.

[0030] The particulate copper sulfide sorbent preferably has a length and width in the range of 1 to 25 mm and an aspect ratio (the value obtained by dividing the longest dimension by the shortest dimension) of less than 4. Spherical granules having a diameter in the range of 1 to 15 mm are most preferred.

[0031] When copper sulfide is present in the eggshell layer, the thickness of the layer on the surface of the carrier can be in the range of 1 to 2000 μm (micrometers), preferably in the range of 1 to 1500 micrometers, more preferably in the range of 1 to 500 micrometers. A thinner layer utilizes the applied copper more efficiently.

[0032] A particularly preferred sorbent is a 1 to 1000 μm thick surface layer on the surface of an aggregate formed from a particulate hydrated alumina carrier material bound together with a cement binder and a clay binder, and coated with particulate preformed copper sulfide together with the clay binder and optional alumina or alumina trihydrate.

[0033] The method used to prepare the sorbent does not require a sulfiding step since the copper sulfide on the sorbent is preformed with the desired properties. The Applicant has found that prior art preparation methods using a sulfiding step produce copper sulfide materials that have a smaller CuS average crystallite size than those suitable for the present invention and thus are more prone to undesirable side reactions and self-heating in an oxygen-containing atmosphere.

[0034] The sorbent used in the method of the present invention is less prone to self-heating than prior art sorbents that are formed and then pre-sulfided. The sensitivity of the material to self-heating can be established using many methods. There is a large body of available published literature regarding a methodology suitable for testing the self-heating properties of copper sulfide-based materials that can pose a significant risk of fire and toxic SO2 gas generation in the worst case. See, for example, F. Rosenblum, J. Nesset and P. Spira, CIM Bulletin vol. 94, No 1056, pp. 92-99. Specialized tests for self-heating are commercially available.

[0035] When the sorbent is loaded into the reaction vessel according to the method of the present invention, the sorbent can be used to treat both liquid and gaseous fluid streams containing heavy metals, particularly fluid streams containing mercury and / or arsenic.

Brief Description of the Drawings

[0036] The present invention will be further described by referring to the following examples and figures.

Figure 1

Figure 2

Figure 4

Figure 3

DETAILED DESCRIPTION OF THE INVENTION

[0037] Example 1: Preparation of Sorbent Material A. A core-shell copper sulfide adsorbent was prepared on hydrated alumina aggregates according to the method of WO 2015092359 (A1) using commercially available reagent grade copper(II) sulfide powder (99.8 wt% CuS) having a D of 20.8 μm. 50 The copper sulfide content of the adsorbent was 12.6 wt%. The average CuS crystallite size of the adsorbent was 41 nm.

[0038] The copper sulfide crystallite size was determined by XRD using a Bruker D8 Advance X-ray diffractometer. The powdered sample was pushed into the sample holder and loaded into the instrument. A parallel beam (Gobel mirror) optical system was used. For the software, Bruker EVA was used for phase identification and Topas was used for Rietveld refinement. The diffractometer conditions were as follows.

[0039] Cu Kα wavelength 1.5406 Å by X-ray Lynxeye PSD detector. Start 2 theta 10° End 2 theta 130° Step 0.022° Step time, seconds 1 X-ray current, mA 40 X-ray voltage, kV 40

[0040] The crystallite size of copper sulfide was determined using the Rietveld analysis (Bruker Topas v6). The Rietveld method for powder XRD data starts with a calculated diffraction pattern based on symmetry information and an approximate structure from the ICDD PDF 4+ structure database. The Rietveld method then uses least-squares minimization to compare all observed points with the calculated plot and refine the calculated structure to minimize the differences.

[0041] Material B. For comparison, an adsorbent precursor was prepared by forming a particulate mixture of copper hydroxycarbonate, alumina trihydrate, calcium aluminate cement, and attapulgite clay according to the method of International Publication No. WO 2009 / 101429 (A1). The resulting product was then sulfided by treating it with a gas containing hydrogen sulfide until the reaction was essentially complete. The copper sulfide content of the adsorbent was 44% by weight. The average CuS crystallite size of the adsorbent was 22 nm.

[0042] Example 2: Self-heating test The self-heating test consisted of a heat storage test in a 1-liter wire basket for the classification, labeling, and packaging of substances and mixtures, corresponding to the standard test for the classification of substances according to UNECE: Recommendations on the Transport of Hazardous Goods - Model Regulations (Rev. 21) and CLP Regulation (EC) No 1272 / 2008.

[0043] The sample was filled into a 1 L cubic wire basket and heated in an oven at a temperature in the range of 120 - 220 °C for 72 hours. The sample in the oven was exposed to an air stream bubbled through water at 70 °C to ensure high humidity before air was supplied to the oven. The temperature of the sample was recorded. If the sample temperature rises more than 60 °C above the air temperature at an air temperature of 140 °C, the sample material will be classified as "self-heating" within the GHS and for transportation (Class 4.2). Other oven temperatures were also used to further quantify the sensitivity to self-heating. Higher temperatures are more likely to cause self-heating.

[0044] The test results are shown in Table 1 and Figures 1 - 3.

[0045]

Table 1

[0046] Plots of Material A when tested at 140 °C and 220 °C are shown in Figures 1 and 2 respectively. For the 220 °C test, the test was started by exposing the sample to a flow of humidified nitrogen for the first 9 hours to achieve stabilization before the gas was switched to air. The plots show that no exotherm was observed in both the 140 °C test and the 220 °C test, indicating that there was no self-heating for Material A.

[0047] For comparison, the plot of Material B is shown in Figure 3, which included an oven temperature of 120 °C. The plot shows a significant rise in the temperature of Material C at 127.3 °C when exposed to these conditions, due to self-heating. The potential for self-heating is exacerbated by higher temperatures.

[0048] Example 3: Preparation of the sorbent Material C. The core-shell copper sulfide sorbent was prepared on hydrated alumina aggregates according to the method of WO 2015 / 092359 (A1) using a commercially available reagent grade copper(II) sulfide powder (99.8 wt% CuS) having a D50 of 14.6 μm. The copper sulfide content of the sorbent was 16.1 wt%. The CuS crystallite size of the sorbent was 46 nm as measured by XRD.

[0049] Example 4: Self-heating test The sorbent (Material C) from Example 3 was tested in a heat storage test in a 1-liter wire basket (100 mm diameter cube) corresponding to the standard tests for the classification of substances for the classification, labeling and packaging of substances and mixtures according to UNECE: Recommendations on the Transport of Hazardous Goods - Model Regulations (Rev. 21) and CLP Regulation (EC) No 1272 / 2008. In this case, the test was carried out at ambient humidity / lower humidity.

[0050] The test results are shown in Table 2 and Figure 4.

[0051]

Table 2

[0052] The samples showed no signs of exothermic activity. This result indicates that a material with the claimed properties can be safely exposed to air during filling.

Claims

1. A method for loading an adsorbent material, comprising the step of forming a bed of particulate copper sulfide adsorbent in a reaction vessel in an oxygen-containing atmosphere, wherein the particulate copper sulfide adsorbent is in the range of 5 to 100 μm. ５０ A method for loading an sorbent material containing more than 5% by weight of copper sulfide powder having an average particle size and an average CuS crystallite size in the range of 25 to 60 nm as determined by XRD.

2. The method according to claim 1, wherein the floor is configured for axial flow or radial flow.

3. The method according to claim 1 or claim 2, wherein the reaction vessel is a cylindrical container.

4. The method according to claim 3, wherein the reaction vessel has a length in the range of 1 to 15 meters, preferably 2 to 10 meters, and a diameter in the range of 0.5 to 5 meters.

5. The aforementioned floor is 10m ３ The method according to claim 1 or claim 2, having a volume exceeding [a certain value].

6. The method according to claim 1 or 2, wherein the reaction vessel is installed vertically such that it has an upper end and a lower end, and the loading is performed by pouring the particulate copper sulfide sorbent through an opening in the upper end, or by transporting the sorbent from the outside of the vessel through the opening.

7. The method according to claim 1 or claim 2, wherein the oxygen-containing atmosphere includes air or air diluted with an inert gas such as nitrogen.

8. The method according to claim 1 or claim 2, wherein the loading method is carried out at a temperature in the range of 5 to 40°C, preferably 10 to 30°C.

9. The method according to claim 1 or claim 2, wherein the average crystallite size of CuS in the particulate copper sulfide sorbent is in the range of 30 to 55 nm.

10. The method according to claim 1 or claim 2, wherein the copper sulfide content of the particulate copper sulfide sorbent is in the range of 5 to 45% by weight, preferably 5 to 25% by weight, and more preferably 5 to 20% by weight (expressed as CuS).

11. The method according to claim 1 or claim 2, wherein the particulate copper sulfide sorbent further comprises a carrier material and / or one or more binders.

12. The method according to claim 1 or 2, wherein the copper sulfide in the particulate copper sulfide sorbent is distributed throughout the sorbent particles, or is provided as a coating on the surface of a molded particulate carrier as an eggshell layer.

13. The method according to claim 1 or claim 2, wherein the particulate copper sulfide sorbent is in the form of spherical granules having a diameter in the range of 1 to 15 mm.

14. The method according to claim 1 or claim 2, wherein the copper sulfide is present in an eggshell layer on a particulate carrier material, and the thickness of the layer on the surface of the carrier material is in the range of 1 to 2000 μm, preferably 1 to 1500 μm, and more preferably 1 to 500 μm.

15. The method according to claim 1 or claim 2, wherein the particulate copper sulfide adsorbent comprises coated particulate preformed copper sulfide, together with a clay binder and optionally selected alumina or alumina trihydrate, as a surface layer 1 to 1000 μm thick on the surface of an aggregate formed from a particulate hydrated alumina carrier material bound together with a cement binder and a clay binder.

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