WO2006010218A1 - Method of catalytic wet oxidation of organic contaminants of alkaline solutions - Google Patents
Method of catalytic wet oxidation of organic contaminants of alkaline solutions Download PDFInfo
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- WO2006010218A1 WO2006010218A1 PCT/AU2005/001114 AU2005001114W WO2006010218A1 WO 2006010218 A1 WO2006010218 A1 WO 2006010218A1 AU 2005001114 W AU2005001114 W AU 2005001114W WO 2006010218 A1 WO2006010218 A1 WO 2006010218A1
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- WIPO (PCT)
- Prior art keywords
- alkaline solution
- concentration
- agent
- ratio
- organic contaminants
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/46—Purification of aluminium oxide, aluminium hydroxide or aluminates
- C01F7/47—Purification of aluminium oxide, aluminium hydroxide or aluminates of aluminates, e.g. removal of compounds of Si, Fe, Ga or of organic compounds from Bayer process liquors
- C01F7/473—Removal of organic compounds, e.g. sodium oxalate
- C01F7/476—Removal of organic compounds, e.g. sodium oxalate by oxidation
Definitions
- the present invention relates to a method of catalytic wet oxidation of organic contaminants of alkaline solutions.
- the application of the present invention will be discussed in the context of the catalytic wet oxidation of organic contaminants of Bayer process solutions, although the scope of the invention encompasses the catalytic wet oxidation of organic contaminants of any alkaline solution.
- the Bayer process is widely used for the production of alumina from aluminium containing ores, such as bauxite. The process involves contacting alumina-containing ores with recycled caustic aluminate solutions, at elevated temperatures, in a process commonly referred to as digestion. In some cases, a significant amount of organic material accompanies the bauxite, a portion of which is responsible for the presence of a range of organic compounds in the resulting solution.
- aluminium hydroxide is added as seed to induce the precipitation of further aluminium hydroxide therefrom.
- the precipitated aluminium hydroxide is separated from the caustic aluminate solution, with a portion of the aluminium hydroxide being recycled to be used as seed and the remainder recovered as product.
- the remaining caustic aluminate solution is recycled for further digestion of alumina containing ore.
- organic contaminants in Bayer process solutions reduces productivity largely through two effects. Firstly, organic contaminants reduce the amount of soda available to dissolve gibbsite and form sodium aluminate in solution. Secondly, the presence of organic contaminants reduces the hydrate precipitation rate, due to crystallization poisoning. Other benefits associated with removal of organic contaminants from Bayer process solutions include a reduction in the amount of soda in the alumina product, reduced liquor viscosity and improved, hydrate agglomeration. Subsidiary disadvantages associated with organic contaminants of Bayer process solutions include reduced boiling point, foaming, liquor and hydrate absorbance and liquor density.
- One method of reducing the levels of organic contaminants in alkaline solutions is to oxidise the contaminants.
- complex organic compounds may be oxidised to simpler compounds and, in turn, to carbon dioxide.
- One technique for oxidizing organic contaminants is catalytic wet oxidation, where the alkaline solution is exposed to an oxidizing agent and a catalyst, typically under conditions of elevated temperature and pressure.
- solution or variations such as “solutions”, will be understood to encompass slurries, suspensions and other mixtures containing undissolved solids.
- a method for the catalytic wet oxidation of organic contaminants of an alkaline solution including the step of:
- Conditions suitable for the catalytic wet oxidation of organic contaminants are known to those skilled in the art and typically involve exposing the solution containing the organic contaminants to the oxidising agent and the catalyst at elevated temperatures and/or pressures.
- Specific examples of the catalytic wet oxidation of alkaline solutions are provided in the preceding discussion of the Background Art. More generally, Brown, N., "Kinetics of copper catalysed oxidation of Bayer liquor organics", Light Metals (1989), pp. 121-130, provides an overview of the effects of temperature, catalyst concentration, oxygen charge and level of agitation on the degree of destruction of organic contaminants, and the contents of such are incorporated herein by reference.
- the method includes the step of:
- carbon dioxide is produced by oxidation of organic contaminants of alkaline solutions. Carbon dioxide reacts with free caustic to form water and carbonate ions. Thus, although the oxidation process may be reducing the concentration of organic contaminants, the significant concurrent consumption of free hydroxide by the carbon dioxide means that the overall effect is to reduce the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants. This process is represented by equations
- the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution is at least approximately 5. In one form of the invention, the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution is at least approximately 6. In one form of the invention, the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution is at least approximately 7. In one form of the invention, the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution is at least approximately 8.
- the preferred ratio of the concentration of free caustic in the alkaline solution (expressed in grams per litre equivalent of sodium carbonate) to the concentration of organic contaminants (expressed as grams per litre equivalent of carbon) is largely determined by balancing the economics of increasing the ratio with the economics of selecting other conditions favourable to destruction of organics, such as elevated temperatures.
- the free caustic concentration generally depends on the total caustic concentration at which the refinery operates, the state of evaporation/dilution of the solution, and the amount of dissolved aluminium in the solution.
- the concentration of organic contaminants is largely related to the organic content of the bauxite used, but also to the state of evaporation/dilution of the stream. The concentration can vary significantly between refineries around the world, perhaps from 2-40g/L.
- alkaline solutions including Bayer process solutions, having lower concentrations of organic contaminants are more amenable to economic elevation of the ratio of free caustic to organic contaminant ratio.
- alkaline solutions having higher concentrations of organic contaminants are those for which it is more desirable to utilise catalytic wet oxidation.
- any upper threshold for the ratio of free caustic to organic contaminants in accordance with any aspect of the present invention is largely of an economic nature.
- the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution is between about 4 and about 20.
- the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution is between about 5 and about 12.
- the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution is between about 5 and about 10.
- the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution is between about 6 and about 10.
- Alkaline solutions may contain sodium carbonate. Increasing the concentration of total sodium in the alkaline solution decreases the solubility of sodium carbonate. In certain circumstances the precipitation of sodium carbonate may be problematic. In such circumstances, the preferred ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution of the method of the present invention may take account of the effect of the concentration of total sodium on the solubility of sodium carbonate.
- Some alkaline solutions may possess a sufficiently high ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution.
- the method may include the preliminary step of:
- the step of elevating the ratio of the concentration of free caustic in the alkaline solution may be performed prior to the step of exposing the alkaline solution to the oxidising agent and catalyst under conditions suitable for the catalytic wet oxidation of organic contaminants, concurrently with the step of exposing the alkaline solution to the oxidising agent and catalyst under conditions suitable for the catalytic wet oxidation of organic contaminants, or both prior to and concurrently with the step of exposing the alkaline solution to the oxidising agent and catalyst under conditions suitable for the catalytic wet oxidation of organic contaminants.
- the step of elevating the ratio of the concentration of free caustic to the concentration of organic contaminants in the alkaline solution may comprise the step of:
- the first causticising agent is selected from the group: sodium hydroxide, lime, slaked lime and mixtures thereof.
- the step of at least maintaining the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants at at least approximately 4 while the alkaline solution is exposed to the oxidising agent and catalyst under conditions suitable for the catalytic wet oxidation of organic contaminants may be performed by the step of:
- the second causticising agent may be added whilst the alkaline solution is exposed to the oxidising agent and catalyst under conditions suitable for the catalytic wet oxidation of organic contaminants.
- the step of adding a second causticising agent to the alkaline solution more specifically comprises the step of:
- the alkaline solution with a quantity of the second causticising agent prior to exposure to the oxidising agent and catalyst under conditions suitable for the catalytic wet oxidation of organic contaminants, said quantity of second causticising agent being sufficient to at least maintain the ratio of the concentration of free caustic in the alkaline solution (expressed in grams per litre equivalent of sodium carbonate) to the concentration of organic contaminants in the alkaline solution (expressed as grams per litre equivalent of carbon) at at least approximately 4.
- the second causticising agent is selected from the group: sodium hydroxide, lime, slaked lime and mixtures thereof.
- the second causticising agent may be identical to the first causticising agent.
- Some alkaline solutions such as Bayer process solutions, contain alumina in the form of the aluminate ion.
- the ratio of total caustic to alumina must be maintained.
- the oxidation of organic contaminants results in the consumption of free caustic, decreasing the total caustic concentration.
- maintaining the ratio of total caustic to alumina allows the increased oxidation of organic contaminants enabled by the method of the present invention to occur without destabilising the Bayer process solution.
- the method includes the step of:
- the step of decreasing the alumina to total caustic ratio of the alkaline solution more specifically comprises the step of decreasing the ratio of alumina in the alkaline solution (expressed as grams per litre AI 2 O 3 ) to total caustic (expressed as grams per litre sodium carbonate) to less than approximately 0.4.
- the step of decreasing the alumina to total caustic ratio of the alkaline solution more specifically comprises the step of decreasing the ratio of alumina in the alkaline solution to total caustic to less than approximately 0.35. Further and still preferably, the step of decreasing the alumina to total caustic ratio of the alkaline solution more specifically comprises the step of decreasing the ratio of alumina in the alkaline solution to total caustic in the alkaline solution to less than approximately 0.3.
- the step of decreasing the alumina to total caustic ratio of the alkaline solution may more specifically comprise the step of:
- the third causticising agent is selected from the group: sodium hydroxide, lime, slaked lime and mixtures thereof.
- the third causticising agent may be identical to one or both of the first and/or second causticising agents.
- the outcome of the oxidation of the organic contaminants is the consumption of free caustic.
- the ratio of alumina to total caustic ratio is also affected by the oxidation of the organic contaminants.
- the method may comprise the step of:
- the step of maintaining the alumina to total caustic ratio below approximately 0.4 comprises the step of maintaining the alumina to total caustic ratio below approximately 0.35. Further and still preferably, the step of maintaining the alumina to total caustic ratio below approximately 0.4 comprises the step of maintaining the alumina to total caustic ratio below approximately 0.3.
- the step of maintaining the alumina to total caustic ratio below approximately 0.4 while exposing the alkaline solution to an oxidising agent and catalyst under conditions suitable for the catalytic wet oxidation of organic contaminants may comprise the step of:
- the fourth causticising agent may be added whilst the alkaline solution is exposed to an oxidising agent under conditions suitable for the oxidation of organic contaminants.
- the step of adding a fourth causticising agent to the alkaline solution more specifically comprises the step of:
- the fourth causticising agent is selected from the group: sodium hydroxide, lime, slaked lime and mixtures thereof.
- the fourth causticising agent may be identical to one or more of the first and/or second and/or third causticising agents.
- first and/or second and/or third and/or fourth causticising agents is dependent on other properties of the alkaline solution, most notably sodium balance.
- Two or more of the steps of: adding a first causticising agent to the alkaline solution, adding a second causticising agent to the alkaline solution, adding a third causticising agent to the alkaline solution and adding a fourth causticising agent to the alkaline solution may be performed concurrently by the addition of a one or more quantities of a causticising agent selected from the group: sodium hydroxide, lime, slaked lime and mixtures thereof.
- Alkaline solutions may contain silica.
- the method may include the step of:
- the step of desilicating the alkaline solution is preferred where the concentration of SiO 2 in the alkaline solution exceeds approximately 0.1 grams per litre.
- the step of desilicating the alkaline solution more specifically comprises the step of:
- the desilicating agent is selected from the group: lime, slaked lime and mixtures thereof.
- the desilicating agent is provided in the form of a solid silica-containing phase.
- the step of adding a desilicating agent to the alkaline solution to induce the precipitation of a silica-containing solid may be performed concurrently with at least one of the steps of: adding a first causticising agent to the alkaline solution, adding a second causticising agent to the alkaline solution, adding a third desilicating agent to the alkaline solution and adding a fourth causticising agent to the alkaline solution by the addition of one or more quantities of a causticising agent selected from the group: lime, slaked lime or mixtures thereof.
- the method comprises the step of adding a desilicating agent to the alkaline solution to induce the precipitation of a silica-containing solid, after this step and before the step of exposing the alkaline solution to an oxidising agent and catalyst under conditions suitable for the catalytic wet oxidation of organic contaminants while the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution is at least approximately 4, the method comprises the step of:
- Conditions suitable for the catalytic wet oxidation of organic contaminants frequently include elevated temperatures. Conveniently, these elevated temperatures are attained by way of heat exchange apparatus. Aluminosilicate scale formation rates become increasingly significant as temperature rises, and heat exchange apparatus are typically provided with extensive surface areas, making desilication prior to temperature elevation advantageous.
- the method includes the steps of separating the silica-containing solid from the alkaline solution and at least maintaining the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants at at least approximately 4 while the alkaline solution is exposed to the oxidising agent and catalyst under conditions suitable for the oxidation of organic contaminants by adding the second causticising agent to the alkaline solution, the step of adding a second causticising agent to the alkaline solution occurs after the step of separating the a silica-containing solid from the alkaline solution.
- the method includes the steps of separating the silica-containing solid from the alkaline solution and at least maintaining the ratio of the concentration of alumina in the alkaline solution to the total caustic concentration in the alkaline solution at or below approximately 0.4 while the alkaline solution is exposed to the oxidising agent and catalyst under conditions suitable for the catalytic wet oxidation of organic contaminants by adding the fourth causticising agent to the alkaline solution
- the step of adding the fourth causticising agent to the alkaline solution occurs after the step of separating the silica-containing solid from the alkaline solution.
- the method comprises the steps of:
- the degree of oxidation of organic contaminants of alkaline solutions facilitated by the method of the invention enables rapid and efficient oxalate destruction, and the method of the present invention is intended to encompass the destruction of oxalate, which may be oxalate inherently present or formed in the solution, or additional oxalate concentrated by some other oxalate removal process.
- a first quantity of lime and sodium hydroxide (relative amounts being dependent on the soda balance) is added to the Bayer process solution to (i) elevate the ratio of the concentration of free caustic to the concentration of organic contaminants to at least 4, (ii) decrease the alumina to total caustic ratio to at most 0.4 and (iii) desilicate the Bayer process solution by inducing the precipitation of a silica- containing solid.
- the first quantity of lime and sodium hydroxide comprises (i) the first causticising agent, (ii) the third causticising agent and (iii) the desilicating agent.
- the silica containing-containing solid is separated from the Bayer process solution, before heating then charging the Bayer process solution with a second quantity of lime or sodium hydroxide (depending on the soda balance), the second quantity of lime or sodium hydroxide being sufficient to (i) at least maintain the ratio of the concentration of free caustic in the Bayer process solution to the concentration of organic contaminants in the Bayer process solution at at least approximately 4 and (ii) at least maintain the ratio of the concentration of alumina in the alkaline solution to the total caustic concentration in the Bayer process solution at or below approximately 0.4 while the Bayer process solution is exposed to an oxidising agent and catalyst under conditions suitable for the catalytic wet oxidation of organic contaminants.
- the second quantity of lime or sodium hydroxide comprises (i) the second causticising agent and (ii) the fourth causticising agent.
- the Bayer process solution is then exposed to a catalyst and an oxidising agent under conditions suitable for catalytic wet oxidation of the organic contaminants of the Bayer process solution. While the Bayer process solution is exposed to the catalyst and oxidising agent under conditions suitable for catalytic wet oxidation of the organic contaminants, the ratio of the concentration of free caustic in the alkaline solution to the concentration of organic contaminants in the alkaline solution is maintained at least approximately 4 and the ratio of the concentration of alumina in the alkaline solution to the total caustic concentration in the alkaline solution is maintained at or below approximately 0.4.
- the best method of performing the invention may include one or more steps to avoid or manage the precipitation of sodium carbonate.
- the concentration of organic contaminants in the Bayer process solution may be managed, reactors capable of managing or purging solids may be used or the chemical composition of the Bayer solution may be adjusted to increase solubility of sodium carbonate.
- Figure 1 is a plot of organic contaminant destruction as a function of time for wet oxidation at 265°C, 100OkPa O 2 and 1g/L CuO of Bayer process solutions having differing free caustic levels;
- Figure 2 is a plot of oxalate formation and destruction as a function of time for wet oxidation at 265°C, 100OkPa O 2 and 1g/L CuO of a range of Bayer process solutions;
- Figure 3 is a schematic flow sheet showing how an embodiment of the method of the present invention might be utilised
- Figure 4 is a plot of % organic contaminant destruction as a function of the initial free caustic to organic contaminant ratio of the Bayer process solution, for wet oxidation undertaken at 265 0 C, 100OkPa O 2 and 1g/L CuO; and
- Figure 5 is a plot illustrating consumption of the sodium salts of acetate, formate and succinate as a function of time, for wet oxidation undertaken at 265 0 C, 100OkPa O 2 and 1g/L CuO.
- Bench trials were conducted by adding 2 L of liquor to an lnconel 600 alloy autoclave with a stirring rate of 500 rpm. After the target temperature of 265 0 C was reached, catalyst and oxygen were added to the liquor. Oxygen gas was injected into the headspace and maintained at a set partial pressure for the duration of the test. Nitrogen gas was also injected at an equal partial pressure for safety reasons
- TOC (organic contaminant) reductions of up to 94% after four hours treatment time were measured at 265°C, 100OkPa O 2 and 1g/L CuO. TOC reductions were calculated by the drop in total organic carbon concentration of the treated Bayer process solutions relative to the start Bayer process solutions, measured by an oxidation/infrared technique.
- Oxalate is both formed and destroyed, hence there is the potential to utilise high temperature catalytic wet oxidation as an oxalate destruction process.
- the presence of catalyst is important for achieving oxalate destruction at practical temperatures and residence times. As can be seen from Figure 2, tests were run where an extra 30 g/L oxalate was added to the liquor and the results showed that all the additional oxalate was consumed, whilst maintaining high liquor TOC reduction.
- Acetate, formate and succinate are also consumed under these conditions.
- An example of their destruction as a function of time is illustrated in Figure 5.
- TOC reduction can be increased by increasing the level of free caustic in the feed liquor or maintaining the free caustic by addition of lime solids.
- the free caustic can be elevated by the addition of sodium hydroxide and this method has the advantage of reducing the final A/TC of the treated liquor, thus reducing the potential for hydrate scaling issues.
- Lime addition also has the benefit of reducing final A/TC, but not to the same extent as sodium hydroxide.
- Figure 1 is a plot of organic contaminant destruction as a function of time for wet oxidation at 265°C, 100OkPa O 2 and 1g/L CuO in Bayer process solutions, demonstrating the efficacy of the addition of the addition of lime and/or sodium hydroxide (FC) in the facilitation of the oxidation of organic contaminants.
- Figure 4 clearly demonstrates the importance of the ratio of the concentration of free caustic to organic contaminants to the achievable %oxidation of the organic contaminants, with a ratio of 4 and above offering marked improvements.
- Figure 2 demonstrates the efficacy of the method of the present invention in the oxidation of sodium oxalate.
- Figure 5 demonstrates consumption of the sodium salts of acetate, formate and succinate as a function of time.
- Table 1 shows the effect of the elevation of the free caustic to organic contaminant ratio, and the reduction of the alumina to total caustic ratio on wet oxidation efficiency at 265degC, 100OkPa 02 and 1g/L CuO catalyst.
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AU2005266853A AU2005266853B2 (en) | 2004-07-30 | 2005-07-29 | Method of catalytic wet oxidation of organic contaminants of alkaline solutions |
BRPI0513772-1A BRPI0513772A (en) | 2004-07-30 | 2005-07-29 | method for wet catalytic oxidation of organic contaminants from alkaline solutions |
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AU2004904247 | 2004-07-30 | ||
AU2004904247A AU2004904247A0 (en) | 2004-07-30 | Method for the Oxidation of Organic Contaminants of Alkaline Solutions |
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Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7678268B2 (en) | 2006-03-08 | 2010-03-16 | Siemens Water Technologies Corp. | Wastewater treatment system |
US8114297B2 (en) | 2006-10-03 | 2012-02-14 | Siemens Industry, Inc. | Wet oxidation of soot |
US8501011B2 (en) | 2007-01-22 | 2013-08-06 | Siemens Energy, Inc. | Wet air oxidation process using recycled catalyst |
US8501149B2 (en) | 2011-02-18 | 2013-08-06 | Siemens Energy, Inc. | H2S conversion to sulfur using a regenerated iodine solution |
US9193613B2 (en) | 2006-10-03 | 2015-11-24 | Siemens Energy, Inc. | pH control to enable homogeneous catalytic wet air oxidation |
US9315401B2 (en) | 2007-01-22 | 2016-04-19 | Siemens Energy, Inc. | Wet air oxidation process using recycled copper catalyst |
US9630867B2 (en) | 2007-09-11 | 2017-04-25 | Siemens Energy, Inc. | Treatment of spent caustic waste |
Citations (3)
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GB2037722A (en) * | 1978-11-10 | 1980-07-16 | Magyar Aluminium | Removal of organic compounds during the Bayer alumina process |
US4215094A (en) * | 1978-02-17 | 1980-07-29 | Sumitomo Aluminum Smelting Company, Ltd. | Method for the removal of organic substances from alkali metal aluminate solution |
US4668486A (en) * | 1985-04-04 | 1987-05-26 | Vereinigte Aluminium-Werke Atkiengesellschaft | Method for removing organic substances from caustic aluminate liquors |
-
2005
- 2005-07-29 WO PCT/AU2005/001114 patent/WO2006010218A1/en active Application Filing
- 2005-07-29 BR BRPI0513772-1A patent/BRPI0513772A/en not_active IP Right Cessation
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
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US4215094A (en) * | 1978-02-17 | 1980-07-29 | Sumitomo Aluminum Smelting Company, Ltd. | Method for the removal of organic substances from alkali metal aluminate solution |
GB2037722A (en) * | 1978-11-10 | 1980-07-16 | Magyar Aluminium | Removal of organic compounds during the Bayer alumina process |
US4668486A (en) * | 1985-04-04 | 1987-05-26 | Vereinigte Aluminium-Werke Atkiengesellschaft | Method for removing organic substances from caustic aluminate liquors |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7678268B2 (en) | 2006-03-08 | 2010-03-16 | Siemens Water Technologies Corp. | Wastewater treatment system |
US8114297B2 (en) | 2006-10-03 | 2012-02-14 | Siemens Industry, Inc. | Wet oxidation of soot |
US8460557B2 (en) | 2006-10-03 | 2013-06-11 | Siemens Energy, Inc. | Catalytic wet oxidation systems and methods |
US9193613B2 (en) | 2006-10-03 | 2015-11-24 | Siemens Energy, Inc. | pH control to enable homogeneous catalytic wet air oxidation |
US8501011B2 (en) | 2007-01-22 | 2013-08-06 | Siemens Energy, Inc. | Wet air oxidation process using recycled catalyst |
US9315401B2 (en) | 2007-01-22 | 2016-04-19 | Siemens Energy, Inc. | Wet air oxidation process using recycled copper catalyst |
US9630867B2 (en) | 2007-09-11 | 2017-04-25 | Siemens Energy, Inc. | Treatment of spent caustic waste |
US8501149B2 (en) | 2011-02-18 | 2013-08-06 | Siemens Energy, Inc. | H2S conversion to sulfur using a regenerated iodine solution |
US8828351B2 (en) | 2011-02-18 | 2014-09-09 | Siemens Energy, Inc. | H2S conversion to sulfur using a regenerated iodine solution |
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