EP0509964B1 - Process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products - Google Patents
Process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products Download PDFInfo
- Publication number
- EP0509964B1 EP0509964B1 EP92830030A EP92830030A EP0509964B1 EP 0509964 B1 EP0509964 B1 EP 0509964B1 EP 92830030 A EP92830030 A EP 92830030A EP 92830030 A EP92830030 A EP 92830030A EP 0509964 B1 EP0509964 B1 EP 0509964B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- caustic soda
- treatment
- purification
- washing
- spent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 title claims description 79
- 235000011121 sodium hydroxide Nutrition 0.000 title claims description 25
- 238000011282 treatment Methods 0.000 title claims description 21
- 238000000034 method Methods 0.000 title claims description 19
- 230000008569 process Effects 0.000 title claims description 18
- 239000007864 aqueous solution Substances 0.000 title claims description 16
- 238000000746 purification Methods 0.000 title claims description 11
- 239000003209 petroleum derivative Substances 0.000 title claims description 10
- 238000005406 washing Methods 0.000 title claims description 10
- 239000000243 solution Substances 0.000 claims description 15
- 238000007254 oxidation reaction Methods 0.000 claims description 11
- ZKQDCIXGCQPQNV-UHFFFAOYSA-N Calcium hypochlorite Chemical compound [Ca+2].Cl[O-].Cl[O-] ZKQDCIXGCQPQNV-UHFFFAOYSA-N 0.000 claims description 9
- 150000002989 phenols Chemical class 0.000 claims description 9
- 238000000926 separation method Methods 0.000 claims description 7
- 239000007791 liquid phase Substances 0.000 claims description 6
- 239000007790 solid phase Substances 0.000 claims description 6
- 230000015572 biosynthetic process Effects 0.000 claims description 4
- 230000003647 oxidation Effects 0.000 claims description 4
- 238000003825 pressing Methods 0.000 claims description 4
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 3
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 239000004571 lime Substances 0.000 claims description 3
- 239000012071 phase Substances 0.000 claims description 3
- 239000005708 Sodium hypochlorite Substances 0.000 claims description 2
- 238000005119 centrifugation Methods 0.000 claims description 2
- 238000001914 filtration Methods 0.000 claims description 2
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 claims description 2
- 239000000725 suspension Substances 0.000 claims description 2
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 6
- 239000002253 acid Substances 0.000 description 6
- 150000001875 compounds Chemical class 0.000 description 6
- 239000002699 waste material Substances 0.000 description 6
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 5
- 239000005864 Sulphur Substances 0.000 description 5
- 230000035943 smell Effects 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 229910001868 water Inorganic materials 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 4
- 239000003518 caustics Substances 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 3
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 229910052785 arsenic Inorganic materials 0.000 description 2
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 2
- 229910052793 cadmium Inorganic materials 0.000 description 2
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 125000005608 naphthenic acid group Chemical group 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 150000003568 thioethers Chemical class 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical class OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000002518 antifoaming agent Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000002894 chemical waste Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 239000010779 crude oil Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 231100001231 less toxic Toxicity 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 235000010755 mineral Nutrition 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- IEQIEDJGQAUEQZ-UHFFFAOYSA-N phthalocyanine Chemical compound N1C(N=C2C3=CC=CC=C3C(N=C3C4=CC=CC=C4C(=N4)N3)=N2)=C(C=CC=C2)C2=C1N=C1C2=CC=CC=C2C4=N1 IEQIEDJGQAUEQZ-UHFFFAOYSA-N 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 239000013049 sediment Substances 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 159000000000 sodium salts Chemical class 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 239000004291 sulphur dioxide Substances 0.000 description 1
- 235000010269 sulphur dioxide Nutrition 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G19/00—Refining hydrocarbon oils in the absence of hydrogen, by alkaline treatment
- C10G19/08—Recovery of used refining agents
Definitions
- the present invention relates to a process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products ("spent caustics"), based on the synergical use of ozone and calcium hypochlorite.
- the treatment according to the invention allows reduction of the pollution load of the spent solutions of caustic soda, obtaining two final streams which, as they are or after further routine treatment, are compatible with the ecological specifications of national and international laws regarding emission of substances into the atmosphere, water discharge and final solid waste destined for disposal in authorized waste disposal centers.
- aqueous solutions of NaOH are usually used, in concentrations of between 5 and 15% by weight (fresh caustic).
- the spent caustic soda solution obtained has a different composition dependent on whether it has been used for purification of LPG (propane and butane), of petrols obtained from thermal and/or catalytic "cracking", or of "straight-run” petrols (obtained from distillation of crude oil at atmospheric pressure), bearing in mind the conventional treatments which these products undergo.
- LPG propane and butane
- petrols obtained from thermal and/or catalytic "cracking"
- straight-run petrols obtained from distillation of crude oil at atmospheric pressure
- the spent caustic soda solutions have pH values ranging from 12,5 to 13,5 and the following composition expressed in percentage by weight:
- GB-A 859 286 suggests the regeneration of a solution of sodium or potassium hydroxide which has been used for the treatment of liquid or gaseous organic compounds to remove acidic components therefrom, particularly a thus used aqueous solution of sodium or potassium hydroxide, which comprises subjecting said solution to an oxidizing treatment by contacting with air or other free-oxygen containing gas in the presence of a catalyst comprising a metal or metal-free phthalocyanine or a derivative thereof and thereafter separating the oxidation products of said acidic components from the solution.
- the process according to the invention is based, generally speaking, on the synergical action of ozone and calcium hypochlorite on the undesired products found in spent caustics.
- the process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products is characterized in that the spent solutions of caustic soda are subjected essentially to the following operations:
- the first oxidization is accompanied by a strong oxidating demolition of the phenolic ring and by a partial oxidation of the compounds containing sulphur, until obtaining much less toxic molecules (for example oxalic acid, carbon dioxide, oxygen, water and sulphur).
- the second oxidation stage promotes the breakage of the R-SH bond and the formation of sulphur molecules in the form of a flaky aggregate which is subject to sedimentation.
- the liquid phase produced by this separation is of a reddish colour and has a slight smell of phenols; it is suitable for routine treatments.
- the solid phase obtained after separation of the pulp is dark yellow in colour, flaky in aspect, and a slight smell of compounds containing sulphur; it is suitable for final disposal in waste disposal dumps and/or for controlled recovery as inert re-cycled material.
- the calcium hypochlorite can be added as it is or formed on site, for example by means of a reaction between sodium hypochlorite and lime.
- Phase separation in the process according to the present invention, can be obtained using an operation chosen from the group comprising: centrifugation, optionally under vacuum; filtering, optionally under vacuum; filter pressing; and band-pressing.
- the spent aqueous solution of caustic soda which is to undergo treatment according to the present invention was obtained from the washing of " straight-run" refinery petrol.
- This solution cannot be disposed of as it is, because its pH value is 13 and it contains a high pollution load. In particular, it contains the following: (by “other chemical compounds” are intended carbonates, sulphites, sulphates and heavy metals such as lead, arsenic, copper and cadmium).
- this solution is subjected to a first oxidization step with 2 kg of O3/kg of total phenols.
- a progressive change in colour of the solution can be seen, turning from dark brown to a lighter shade of brown; at the same time the intense and pungent smell of phenol and organic substance tends to grow less.
- the pH value goes down from 13 to approximately 10.
- the process is accompanied by an increase in temperature up to 38-40°C and by an intense physiological foaming, which grows noticeably less on the controlled addition of an antifoaming agent.
- the second oxidization step is then performed, adding 6% by weight of calcium hypochlorite, with reference to the ozonized spent aqueous solution of caustic soda.
- the formation of dark yellow flakes can be noted, and these tend to sediment, generating a pulp of a colour tending towards dark yellow. There is no emanation of particular smells.
- the flakes are characterized by a high level of sedimentation.
- the pulp is made to undergo centrifugal separation by means of an horizontal mechanical two-way decanter.
- a liquid phase and a solid phase are obtained.
- red in colour with a not particularly intense smell of phenol, a reduction of the content in phenols, sulphides and mercaptans is registered of about 90% with respect to the starting values.
- This stream as it is or after further treatment, is suitable for disposal using current refinery and petrol-chemical waste disposal technology.
- the centrifuged solid phase results easy to shovel and is compatible with the other factory waste, as it can be integrated in the pre-treatment system to be adopted for said waste, before final disposal.
- this residual solid stream can be classified, e.g. according to the Italian Law (DPR 915/82 and the deliberation by the C.I. dated 27/7/84), as special waste. It can therefore be disposed of, after solidification/stabilization by the addition of lime and silicates, as such or together with the pool of special refinery waste, deriving from purification sludge of a chemical-physical and biological nature.
Landscapes
- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Paper (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Physical Water Treatments (AREA)
Description
- The present invention relates to a process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products ("spent caustics"), based on the synergical use of ozone and calcium hypochlorite. The treatment according to the invention allows reduction of the pollution load of the spent solutions of caustic soda, obtaining two final streams which, as they are or after further routine treatment, are compatible with the ecological specifications of national and international laws regarding emission of substances into the atmosphere, water discharge and final solid waste destined for disposal in authorized waste disposal centers.
- As is known, many intermediate and final streams from plants for the processing of petroleum products contain a variety of acid compounds such as hydrogen sulphide (sulphydric acid), mercaptans, phenols, thiophenols and naphthenic acids. These substances must be removed or brought down to specific concentrations. The compounds containing sulphur must be reduced to low concentrations in order to satisfy customs and merchant specifications, or to improve the "octane number" of the petrol. Sulphydric acid and phenols must be removed to prevent them from interfering with successive processes for reduction of mercaptans. Naphthenic acids must be removed to obtain the clearly defined specifications regarding acidity of certain fuel products.
- For the removal of the above undesired compounds, aqueous solutions of NaOH are usually used, in concentrations of between 5 and 15% by weight (fresh caustic).
- The spent caustic soda solution obtained has a different composition dependent on whether it has been used for purification of LPG (propane and butane), of petrols obtained from thermal and/or catalytic "cracking", or of "straight-run" petrols (obtained from distillation of crude oil at atmospheric pressure), bearing in mind the conventional treatments which these products undergo.
- In general the spent caustic soda solutions have pH values ranging from 12,5 to 13,5 and the following composition expressed in percentage by weight:
- free caustic soda
- 5,0-7,5
- total oils
- 0,5-2,0
- total sulphides
- 0,1-3,0
- cyanides
- 0,05-0,3
- ammonia
- 0,05-0,4
- phenols
- 0,2-10
- lead
- 2.10⁻⁴-10.10⁻⁴
- arsenic
- 1.10⁻⁴-5.10⁻⁴
- copper
- 5.10⁻⁴-50.10⁻⁴
- cadmium
- 1.10⁻⁴-5.10⁻⁴
- The oxidative treatment of spent caustic soda solutions is already known from the prior art. GB-A 859 286 suggests the regeneration of a solution of sodium or potassium hydroxide which has been used for the treatment of liquid or gaseous organic compounds to remove acidic components therefrom, particularly a thus used aqueous solution of sodium or potassium hydroxide, which comprises subjecting said solution to an oxidizing treatment by contacting with air or other free-oxygen containing gas in the presence of a catalyst comprising a metal or metal-free phthalocyanine or a derivative thereof and thereafter separating the oxidation products of said acidic components from the solution.
- From the state of the art of this specific field it is further known that the conventional technology relating to treatment of "spent caustics" from the petroleum and petrol-chemical industry is based on their neutralization using mineral acids (for example sulphuric acid and hydrochloric acid) or using gases containing carbon dioxide and sulphur dioxide.
- According to this technology, when the solution of spent caustic soda is neutralized (or "sprung", as this operation is commonly known), two distinct layers are formed: a lower aqueous layer containing the sodium salts of the neutralizing acid, called "sprung-water", and an upper oily layer containing phenolic compounds which are given various names in this sector, the commonest of which is "sprung-acid".
- This technology, although amply consolidated, is not entirely satisfactory from an environmental point of view. In fact, it involves highly exothermic reactions, accompanied by a notable pH jump (from pH 12-13 to pH 4-5) and the production of gaseous effluents which require the use of successive thermo-destructive processes. Furthermore, this is an extremely costly technique due to the special nature of the metallic materials to be employed in the processing plants and due to the need for final sour-water stripping interventions and consequent final thermodistruction of the stripping residue.
- Given the above, there is in this field a need for a process which makes it possible to overcome the above mentioned drawbacks.
- The process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products according to the present invention makes it possible to avoid all the disadvantages found in the state of the art, furthermore offering other advantages which will be made clear in the following.
- The process according to the invention is based, generally speaking, on the synergical action of ozone and calcium hypochlorite on the undesired products found in spent caustics.
- More specifically, the process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products, is characterized in that the spent solutions of caustic soda are subjected essentially to the following operations:
- a first oxidization with 0,5-3,5 Kg of O₃/Kg of total phenols, at a temperature in the range of 38-42°C;
- a second oxidization with 5-10% by weight of calcium hypochlorite, with reference to the previously ozonized spent aqueous solution of caustic soda, at a temperature selected from the range of 25-35°C, with the formation of a pulp with a flaky suspension; and
- separation of the pulp into two phases, a liquid phase and a solid phase, each of which can be eliminated in a much easier and safer way, from an ecological point of view, than the initial solution of spent caustic soda.
- It has been seen that the first oxidization is accompanied by a strong oxidating demolition of the phenolic ring and by a partial oxidation of the compounds containing sulphur, until obtaining much less toxic molecules (for example oxalic acid, carbon dioxide, oxygen, water and sulphur). The second oxidation stage promotes the breakage of the R-SH bond and the formation of sulphur molecules in the form of a flaky aggregate which is subject to sedimentation. The liquid phase produced by this separation is of a reddish colour and has a slight smell of phenols; it is suitable for routine treatments. The solid phase obtained after separation of the pulp is dark yellow in colour, flaky in aspect, and a slight smell of compounds containing sulphur; it is suitable for final disposal in waste disposal dumps and/or for controlled recovery as inert re-cycled material.
- In the process according to the present invention, the calcium hypochlorite can be added as it is or formed on site, for example by means of a reaction between sodium hypochlorite and lime.
- Phase separation, in the process according to the present invention, can be obtained using an operation chosen from the group comprising: centrifugation, optionally under vacuum; filtering, optionally under vacuum; filter pressing; and band-pressing.
- In the above, a description of a general nature has been given of the process object of the present invention. There will now be given, with the aid of an example, a more detailed description of a preferred form of realization, with the aim of rendering objectives, characteristics, advantages and function more clear.
- The spent aqueous solution of caustic soda which is to undergo treatment according to the present invention was obtained from the washing of " straight-run" refinery petrol. This solution cannot be disposed of as it is, because its pH value is 13 and it contains a high pollution load. In particular, it contains the following:
(by "other chemical compounds" are intended carbonates, sulphites, sulphates and heavy metals such as lead, arsenic, copper and cadmium). - After homogenization in a suitable homogenizing container, this solution is subjected to a first oxidization step with 2 kg of O₃/kg of total phenols. A progressive change in colour of the solution can be seen, turning from dark brown to a lighter shade of brown; at the same time the intense and pungent smell of phenol and organic substance tends to grow less. The pH value goes down from 13 to approximately 10. The process is accompanied by an increase in temperature up to 38-40°C and by an intense physiological foaming, which grows noticeably less on the controlled addition of an antifoaming agent. The second oxidization step is then performed, adding 6% by weight of calcium hypochlorite, with reference to the ozonized spent aqueous solution of caustic soda. The formation of dark yellow flakes can be noted, and these tend to sediment, generating a pulp of a colour tending towards dark yellow. There is no emanation of particular smells. The flakes are characterized by a high level of sedimentation.
- The pulp is made to undergo centrifugal separation by means of an horizontal mechanical two-way decanter. A liquid phase and a solid phase are obtained. In the liquid phase, red in colour, with a not particularly intense smell of phenol, a reduction of the content in phenols, sulphides and mercaptans is registered of about 90% with respect to the starting values. This stream, as it is or after further treatment, is suitable for disposal using current refinery and petrol-chemical waste disposal technology.
- The centrifuged solid phase, with a dryness of 35% by weight, results easy to shovel and is compatible with the other factory waste, as it can be integrated in the pre-treatment system to be adopted for said waste, before final disposal. In particular this residual solid stream can be classified, e.g. according to the Italian Law (DPR 915/82 and the deliberation by the C.I. dated 27/7/84), as special waste. It can therefore be disposed of, after solidification/stabilization by the addition of lime and silicates, as such or together with the pool of special refinery waste, deriving from purification sludge of a chemical-physical and biological nature.
the balance being water.
Claims (5)
- Process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products, the process comprising an oxidation treatment and a separation treatment characterized in that the spent solutions of caustic soda are subjected essentially to the following operations:- a first oxidization with 0,5-3,5 Kg of O₃/Kg of total phenols, at a temperature in the range of 38-42°C;- a second oxidization with 5-10% by weight of calcium hypochlorite, with reference to the previously ozonized spent aqueous solution of caustic soda, at a temperature selected from the range of 25-35°C, with the formation of a pulp with a flaky suspension; and- separation of the pulp into two phases, a liquid phase and a solid phase, each of which can be eliminated in a much easier and safer way, from an ecological point of view, than the initial solution of spent caustic soda.
- Process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products according to the previous claim, in which the calcium hypochlorite is added as it is to the spent aqueous solution of caustic soda.
- Process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products according to claim 1, in which the calcium hypochlorite is formed on site.
- Process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products according to claim 3, in which the calcium hypochlorite is formed on site by means of reaction between sodium hypochlorite and lime.
- Process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products according to any one of the preceding claims, in which separation of the pulp into two phases, a liquid phase and a solid phase, is obtained by means of an operation selected from the group comprising:
centrifugation, optionally under vacuum; filtering, optionally under vacuum; filter-pressing; and band-pressing.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
ITRM910118 | 1991-02-20 | ||
ITRM910118A IT1244498B (en) | 1991-02-20 | 1991-02-20 | PROCEDURE FOR THE CLEANING TREATMENT OF CAUSTIC SODA AQUEOUS SOLUTIONS EXHAUSTED BY PURIFICATION AND WASHING OF PETROLEUM PRODUCTS. |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0509964A1 EP0509964A1 (en) | 1992-10-21 |
EP0509964B1 true EP0509964B1 (en) | 1994-08-03 |
Family
ID=11399889
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP92830030A Expired - Lifetime EP0509964B1 (en) | 1991-02-20 | 1992-01-27 | Process for the treatment of spent aqueous solutions of caustic soda used for purification and washing of petroleum products |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0509964B1 (en) |
DE (1) | DE69200296T2 (en) |
ES (1) | ES2057980T3 (en) |
IT (1) | IT1244498B (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5885422A (en) * | 1997-02-26 | 1999-03-23 | Stone & Webster Engineering Corporation | Spent caustic (pre)treatment process |
IT1307285B1 (en) * | 1999-11-30 | 2001-10-30 | Ecotec Srl | DE-POLLUTANT TREATMENT AND REGENERATION OF AQUEOUS SODACAUSTIC SOLUTIONS EXHAUSTED BY PURIFICATION AND WASHING OF PETROLEUM PRODUCTS, AND |
US7713399B2 (en) | 2005-05-12 | 2010-05-11 | Saudi Arabian Oil Company | Process for treating a sulfur-containing spent caustic refinery stream using a membrane electrolyzer powered by a fuel cell |
CO6170071A1 (en) * | 2008-12-12 | 2010-06-18 | Ecopetrol Sa | PROCESS FOR THE TREATMENT OF SOLDED SODES AND THE PRODUCT OBTAINED IN THE SAME PROCESS |
CN104603242B (en) | 2012-08-14 | 2017-03-08 | 通用电气公司 | Breaking compositionss and using method |
US9260601B2 (en) | 2012-09-26 | 2016-02-16 | General Electric Company | Single drum oil and aqueous products and methods of use |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB859286A (en) * | 1958-09-19 | 1961-01-18 | Universal Oil Prod Co | Process for regenerating used alkaline reagents |
-
1991
- 1991-02-20 IT ITRM910118A patent/IT1244498B/en active IP Right Grant
-
1992
- 1992-01-27 ES ES92830030T patent/ES2057980T3/en not_active Expired - Lifetime
- 1992-01-27 EP EP92830030A patent/EP0509964B1/en not_active Expired - Lifetime
- 1992-01-27 DE DE69200296T patent/DE69200296T2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
DE69200296T2 (en) | 1995-02-09 |
ES2057980T3 (en) | 1994-10-16 |
IT1244498B (en) | 1994-07-15 |
DE69200296D1 (en) | 1994-09-08 |
ITRM910118A0 (en) | 1991-02-20 |
ITRM910118A1 (en) | 1992-08-20 |
EP0509964A1 (en) | 1992-10-21 |
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