EP2935203A1 - Continuous method for separating salts in the production of dimethylacetamide - Google Patents
Continuous method for separating salts in the production of dimethylacetamideInfo
- Publication number
- EP2935203A1 EP2935203A1 EP13815464.6A EP13815464A EP2935203A1 EP 2935203 A1 EP2935203 A1 EP 2935203A1 EP 13815464 A EP13815464 A EP 13815464A EP 2935203 A1 EP2935203 A1 EP 2935203A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- solid
- evaporation
- product mixture
- forced circulation
- dimethylacetamide
- 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.)
- Withdrawn
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C231/00—Preparation of carboxylic acid amides
- C07C231/22—Separation; Purification; Stabilisation; Use of additives
- C07C231/24—Separation; Purification
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C231/00—Preparation of carboxylic acid amides
- C07C231/02—Preparation of carboxylic acid amides from carboxylic acids or from esters, anhydrides, or halides thereof by reaction with ammonia or amines
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/06—Flash distillation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/42—Regulation; Control
Definitions
- the invention relates to a continuous process for the separation of salts in the production of dimethylacetamide.
- DMAC Dimethylacetamide
- polar solvent especially for polymers and gases, as a paint stripper, extractant and crystallization aid. Due to its high boiling temperature, DMAC is used in the coatings industry for special coating materials based on polymers, in particular polyamides and polyurethanes. DMAC is also used for the production of fibers and films and as a reaction medium. When spandex® fibers are spun, DMAC can be used as an auxiliary and subsequently at least partially recovered.
- WO 2006/061 159 A1 discloses a continuous process for the preparation of N, N-dimethylacetamide (DMAC) by continuous reaction of methyl acetate (MeOAc) with dimethylamine (DMA) in the presence of a basic catalyst.
- DMAC N, N-dimethylacetamide
- the catalyst is homogeneous and / or suspended in the reaction mixture.
- poly-THF polytetrahydrofuran
- by-products may also be present. These by-products may in particular be tetrahydrofuran (THF) and / or dimethyl ether.
- the liquid reaction product of the process can be expanded for further work-up in a distillation column.
- the basic catalyst contained in the reaction effluent is neutralized. This is done by adding in particular water, an aqueous or anhydrous protic acid, in particular sulfuric acid, methanesulfonic acid, carboxylic acid, phosphoric acid and the like.
- a disadvantage of this method is the incrustations that increase with increasing operating time, in particular crystallization fouling and caking, especially on heated walls, which results in lower heat transfer performance, as well as blockages of pipelines and ultimately a time- and material-intensive replacement of System elements result.
- the Exchange of system elements requires maintenance downtime with production downtime and a high cost of materials and the associated costs.
- Another disadvantage is the cleaning and processing of the replaced system elements.
- time-consuming cleaning produces saline wastewater, which may in particular also contain residual amounts of DMAC, which, in addition to a discontinuous accumulation of highly concentrated wastewater in a wastewater treatment plant, can lead to further problems.
- the object is achieved by a continuous process for discharging a solid, salt-containing phase containing alkali metal and / or alkaline earth metal acetates from the product mixture of the preparation of ⁇ , ⁇ -dimethylacetamide (DMAC) by reacting methyl acetate (MeOAc) with dimethylamine (DMA) in the presence a catalyst comprising ⁇ , ⁇ -dimethylacetamide (DMAC), methyl acetate (MeOAc), dimethylamine (DMA) and a catalyst with the following process steps: level-controlled feeding of the product mixture as feed stream into an evaporation vessel of a forced circulation evaporator, wherein the forced circulation evaporator in the flow direction at least an evaporation tank, a pump, a first heat exchanger and a return line into the evaporation tank as a forced circulation evaporation circuit, wherein the return line has a throttle element and arranged downstream in the flow direction an inlet piece, wherein on the level-controlled Zuf the
- Solid / liquid phase of the discharged partial stream comprising the solid, saline phase containing alkali metal and / or alkaline earth metal acetates in at least one separating apparatus in a solid, saline phase containing alkali metal and / or alkaline earth metal acetates and a liquid phase,
- Level-controlled feeding of the product mixture in the sense of the present invention is understood to mean feeding of the product mixture into the evaporation container, which is regulated as a function of a predetermined level in the evaporation container. As long as the level in the evaporation tank is below the predetermined level, in particular product mixture is supplied until reaching the predetermined level.
- a forced circulation evaporator is understood to mean a circulation evaporator which in particular uses a pump in order to force the product mixture containing volatile components to flow through the circulation evaporator.
- the evaporation vessel, the pump, the first heat exchanger and the return line into the evaporation vessel form the forced circulation evaporation circulation.
- a return line is understood to mean a line which in the forced circulation evaporation cycle leads back in the direction of flow from the first heat exchanger into the evaporation container.
- the return line may in particular be a pipe, a hose.
- Throttle element in the sense of the present invention is understood to mean any device which generates a pressure difference in the return line upstream of the throttle element in the flow direction, the pressure in the return line in the flow direction upstream of the throttle element being higher than the pressure downstream of the throttle element Throttling element, so that takes place in the flow direction after the throttle element, a pressure relief.
- An introduction piece in the sense of the present invention is understood to mean any device via which volatile components of the product mixture obtained after flash evaporation, optionally unevaporated components of the product mixture in a liquid phase and a solid, salt-containing phase containing alkali metal and / or alkaline earth metal acetates via the return line the evaporation tank to be initiated.
- the inlet piece may in particular be a pipe piece, a nozzle, a hose.
- the recirculation of components of the product mixture from the forced circulation evaporation circuit into the evaporation container is understood in the context of the present invention as recycling of the volatile components of the product mixture obtained after flash evaporation.
- the recycling can be carried out in particular after the throttle element in the return line through the inlet.
- Recirculation of the liquid phase obtained after the solid / liquid run means in the context of the present invention the recycling of the liquid phase obtained after the solid / liquid separation into the evaporation vessel.
- a return of components in the evaporation tank basically also affects the level of the evaporation tank.
- a predetermined filling level is understood to mean a predetermined filling level in the evaporation container.
- the predetermined level is influenced in particular by the feeding of the product mixture, the removal of the vapor phase and the discharge of a partial flow.
- the specification of the Grestand level is determined by the distance between the level surface of the level and the Einleit ceremoniess.
- the level surface is understood at the level in the evaporation vessel.
- the level surface may in particular be the outer surface of a liquid phase, a foam phase at the level in the evaporation tank.
- Under separation apparatus in the context of the present invention is basically any device for the separation of liquid and solid phases to understand.
- the separation can be carried out in particular by means of filtration, in particular cake-forming filtration, candle filtration, membrane filtration, ultrafiltration, surface filtration, depth filtration, centrifugal, sieving, sedimentation in Erdgravitations- or centrifugal field.
- a continuous process is advantageous in which the product mixture in the return line in the flow direction downstream of the throttle element has flow velocities in a range of 0.5 to 4 m / s. Flow rates of 1 to 3 m / s are preferred, more preferably in the range of 1.5 to 2.5 m / s.
- the product mixture in the return line after the throttle element in the continuous process to a temperature in the range of 50 to 300 ° C. Preference is given to temperatures in the range from 80 to 250 ° C., particularly preferably in the range from 100 to 250 ° C.
- the product mixture leaving the inlet has a flow with a Reynolds number of greater than 10 4 .
- the product mixture containing N, N-dimethylacetamide (DMAC) in the return line in the flow direction downstream of the throttle element has a pressure-temperature ratio such that ⁇ , ⁇ -dimethylacetamide (DMAC) is in the vapor phase.
- the discharged vapor phase is distilled by cooling in at least one second heat exchanger to give ⁇ , ⁇ -dimethylacetamide (DMAC).
- the throttling element is a pressure-maintaining member, a valve, a control valve, a spool, an orifice, a ring orifice, a nozzle, a flap, a pipe constriction, a bore and a combination thereof.
- the throttle element is adjusted in a continuous process so that a differential pressure in the flow direction in a region upstream of the throttle element to a region downstream of the throttle element is preferably greater than 0.1 bar.
- the evaporation for the separation of salt in the evaporation vessel has a pressure in the range of 0.01 to 5 bar, particularly preferably in the range of 0.1 to 2 bar.
- the vapor phase removed from the evaporation vessel preferably has a proportion in the continuous process of from 30 to 99% by weight of N, N-dimethylacetamide (DMAC), based on the total weight of the feed stream.
- DMAC N, N-dimethylacetamide
- the process is preferably carried out continuously and has in particular an average residence time of the desired product in the range from 1 to 60 minutes, particularly preferably in the range from 30 to 60 minutes.
- the flash evaporation of the continuous process comprises a plurality of evaporators arranged in series, in parallel, or in combinations thereof.
- the evaporation comprises a plurality of forced circulation evaporators, which are arranged in series connection, in parallel connection or in a combination thereof.
- the interconnection of the forced circulation evaporator may comprise, for example, two to twelve, preferably two to ten and in particular two, three, four, five or six identical or different forced circulation evaporators.
- the forced circulation evaporators can each be operated with or without feedback.
- the discharge from a forced circulation evaporator may also be at least partially conducted into an upstream forced circulation evaporator.
- the flash evaporation takes place in one stage or in several successive stages, for example in two, three, four, five or six stages connected in series.
- the solid-liquid separation in the continuous process is a filtration, in particular a cake-forming filtration, a candle filtration, a membrane filtration, an ultrafiltration, a surface filtration, a depth filtration, a centrifugal process, a sieving process, a sedimentation method in the earth gravity and / or centrifugal field and Combinations thereof.
- the solid-liquid separation in the continuous process is continuous or discontinuous.
- the catalyst in the continuous process is a basic catalyst, an alkali metal hydroxide, alkaline earth metal hydroxide, alkali metal alcoholate, alkaline earth metal alcoholate, alkali metal carbonate, alkaline earth metal carbonate, alkali metal hydrogencarbonate, alkaline earth metal bicarbonate, an amine, especially a tertiary amine, and combinations thereof and the alkali metal Li, Na, K, Rb, Cs and combinations thereof.
- the evaporation in the continuous process has a specific Thompson inhabitbelastung in the range of 1 - 100 kW / m 2 , based on the transferred heat output and the evaporator surface of the evaporator.
- the heat exchanger is heated by means of heating steam or heat transfer medium.
- the method according to the invention has the following advantages: No or reduced deposits on the walls of the evaporation tank.
- the evaporation vessel is heated from the outside, and there is heating of the walls of the evaporation vessel and the direct transfer of heat energy from the walls to the product mixture in the evaporation vessel.
- deposits on the wall surfaces, which are in contact with the product mixture are formed by phase transitions.
- a heating of the product mixture takes place in the first heat exchanger and thus outside of the evaporation tank.
- the subsequent flash evaporation of the heated product mixture then takes place according to the invention in the flow direction downstream of the throttle element, ie only when the heated product mixture is returned to the evaporation tank.
- the continuous process according to the invention has no direct heat energy transfer from the heated walls of the evaporation vessel to the product mixture and no or only minor deposits form on the wall surfaces of the evaporation vessel, which are in contact with the product mixture.
- a foam layer may initially form on the surface of the surface due to the phase transition of the liquid phase of the product mixture to the adjacent atmosphere in the evaporation vessel.
- the recycling of the components of the product mixture obtained after flash evaporation into the evaporation tank is carried out according to the invention such that it takes place at least partially in the area of the level surface.
- a pipeline which is partially above the level surface and partially located directly at or below the level surface, be arranged.
- the phase transition between the liquid phase of the product mixture to the adjacent atmosphere in the evaporation tank is continuously disturbed and at least a part of the level surface is in motion, for example, so that foaming is disturbed and / or prevented.
- foaming as a precursor to crust formation, encrustation and / or cake formation is prevented, the crust can no longer form on the surface surface.
- the inventive method can be operated continuously and there are no production stoppages due to crust formation at the level surface required.
- the feed stream is enriched with the liquid phase obtained after the solid / liquid run.
- the cleaning of the evaporation tank is inevitable because, as already stated above, due to the process, deposits, caking and encrustations form on the walls of the evaporation tank.
- the tendency to deposit can be actively influenced as described above.
- the heating of the product mixture takes place outside of the evaporation vessel in a first heat exchanger, whereby no direct heat transfer, for example, from heated walls of the evaporation vessel takes place on the product mixture, which is on the wall surfaces, which are in contact with the product mixture, no and / or only minor Form deposits by phase transitions.
- the amount of depositable salts in the process of the invention can be actively influenced by removal of partial streams from the product mixture of the evaporation vessel and separation of the solid in a separation process.
- inventive possibility of combining these two influencing possibilities is particularly advantageous for a continuous, trouble-free and economical process management with high throughput rates.
- FIG. 1 shows a schematic overview of the method according to the invention. The following reference symbols are used:
- FIG. 1 The schematic overview in Figure 1 with a forced circulation evaporator, a downstream distillation column and a solid-liquid separation apparatus T shows a preferred embodiment of the method according to the invention.
- the continuous process is fed via a feed stream 1.
- a fill level N with a level surface O is formed in an evaporation vessel V of the forced circulation evaporator.
- the forced circulation evaporator has downstream of the evaporation tank V, a pump P, a first heat exchanger W1 and a return pipe R into the evaporation tank V as a forced circulation evaporation circuit.
- a stream of the product mixture is discharged on the bottom side and supplied to the first heat exchanger W1 with the pump P.
- the product mixture is heated in the first heat exchanger W1 and returned to the evaporation vessel V via the return line R and an inlet piece E arranged at the end in the flow direction.
- the pumping of the product mixture in the flow direction through the first heat exchanger W1 against the throttle element D builds up a pressure in the first heat exchanger W1, which pressure can be regulated in particular via the throttle element D.
- a flash evaporation of volatile Components of the product mixture in the flow direction downstream of the throttle element D, there is a flash evaporation of volatile Components of the product mixture to form a vapor phase F containing ⁇ , ⁇ -dimethylacetamide (DMAC) and precipitation of a solid, salt-containing phase instead.
- the volatile components of the product mixture obtained after flash evaporation, optionally unevaporated components of the product mixture in a liquid phase and a solid, salt-containing phase are recycled through the return line R via the inlet E into the evaporation vessel.
- the vapor phase F is removed from the evaporation vessel V as discharge stream 2 and condensed in a second heat exchanger W2.
- the solid, saline-containing phase in the evaporation vessel V is concentrated.
- a partial stream 3 is discharged from the evaporation vessel V and fed to the solid-liquid separation apparatus T, such as a filter chute.
- the liquid phase obtained is returned to the evaporation, in particular to the evaporation vessel V.
- a preferred plant for carrying out the method according to the invention may comprise a plurality of forced circulation flash evaporators, which are arranged in a cascade connection.
- the forced circulation expansion evaporators are arranged such that a residue of a first forced circulation vent evaporator is passed into a second forced circulation flash evaporator and the second forced circulation flash evaporator is passed to a third forced circulation flash evaporator, which is further continued with a further number of forced circulation flash evaporators.
- the vapors from the upstream evaporator stage are used to heat the downstream evaporator stage.
- the vapors can also be fed to a distillation column.
- the product mixture when the product mixture is heated in the first heat exchanger W1, there is no formation of vapor bubbles. As a result, a failure and the caking of tendency to encrustation solids on heated walls can be avoided.
- the vapor bubble formation takes place in the flow direction only after the throttle element D, in particular a pressure-holding valve instead.
- a separation in the separation apparatus T according to the usual methods, in particular with candle filters.
- an open filter fabric of Teflon with an air passage of 150 L / dm 2 / min can be preferably used. If the filter cake resistance is too high, the feed is interrupted and the filter cake is further purified by blowing nitrogen or steam away from organic residues before either discarding the filter cake or dissolving the salt with water and feeding it to a wastewater treatment plant.
- An advantage of using steam for dry blowing is the ability to condense the resulting vapor with the organics.
- the resulting water could then be used for catalyst decomposition and allows a return of the organics.
- the electricity would have to be disposed of via a torch.
- the effluent evaporated from the solid and partially or totally condensed discharge is worked up by distillation under the usual distillation conditions, e.g. in one or more columns interconnected.
- the pilot plant included a forced circulation evaporator, a downstream distillation column and a solid-liquid separation apparatus.
- an evaporation tank V In the circulation of the forced circulation evaporator, an evaporation tank V, a centrifugal pump P, a first heat exchanger W1 and a return line R were arranged in the flow direction of the evaporation vessel V.
- As feed stream 1 a product mixture was fed level-controlled into the evaporation vessel V.
- the product mixture was prepared according to WO 2006/061 159 A1, consisting of 15% by weight of methanol, 3% by weight of dimethylamine, 6% by weight of methyl acetate, 75% by weight of DMAC and about 1% by weight of sodium methoxide ,
- the product mixture based on the feed stream 1, continuously added 1 wt .-% of water to neutralize sodium methoxide and the product mixture level-controlled fed to the evaporation vessel V to form a level level N in the evaporation vessel with a level surface O.
- the product mixture was pumped by a centrifugal pump P in the first heat exchanger W1 and heated to a temperature in the range of 120 ° C to 150 ° C.
- the heating of the first heat exchanger W1 was carried out by means of a heat transfer oil.
- the specific heating surface load was 20 kW / m 2 .
- a pressure was built up in the first heat exchanger W1.
- This pressure in the heat exchanger was with the throttle element, in particular a control valve in the outlet region of the heat exchanger W1 regulated and adjusted so that during the temperature control of the product mixture no vapor bubble formation and no evaporation took place in the heat exchanger W1.
- the throttle element D has been set so that a differential pressure between the pressure within the heat exchanger and the pressure in the flow direction downstream of the throttle element D in a range of 0.1 to 0.5 bar, the pressure decreases in the flow direction after the throttle element ,
- the pressure in the evaporation tank was in the range of 0.5 to 1.2 bar.
- the vapor phase F comprises in particular also components of the product mixture and may, for example, about 15% by weight of methanol, about 3% by weight of dimethylamine, about 6% by weight of methyl acetate, about 75% by weight of DMAC, 1% water, based on the total weight of the product mixture.
- the volatile components of the product mixture obtained after the flash evaporation, optionally unevaporated components of the product mixture in a liquid phase and a solid, salt-containing phase were recycled through the return line R via the inlet E into the evaporation vessel.
- the flow velocity in the return line R in the flow direction downstream of the throttle element D was 2 m / s.
- the introducing piece was set to end in a range of 30 cm immediately above to 20 cm below the level surface O of the level N of the evaporation tank.
- the vapor phase was discharged from the evaporation vessel V as the discharge stream 2 and condensed in the second heat exchanger W2. Through the evaporation process and the removal of the vapor phase, the solid salt-containing phase in the evaporation vessel V was concentrated.
- a partial stream 3 was discharged from the evaporation vessel V at a controlled level and fed to a solid-liquid separating apparatus T designed as a filter. After the separation of the solid from the liquid, the liquid was returned to the evaporation, in particular to the evaporation vessel V.
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP13815464.6A EP2935203A1 (en) | 2012-12-19 | 2013-12-18 | Continuous method for separating salts in the production of dimethylacetamide |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP12197998 | 2012-12-19 | ||
PCT/EP2013/077087 WO2014095999A1 (en) | 2012-12-19 | 2013-12-18 | Continuous method for separating salts in the production of dimethylacetamide |
EP13815464.6A EP2935203A1 (en) | 2012-12-19 | 2013-12-18 | Continuous method for separating salts in the production of dimethylacetamide |
Publications (1)
Publication Number | Publication Date |
---|---|
EP2935203A1 true EP2935203A1 (en) | 2015-10-28 |
Family
ID=47435781
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP13815464.6A Withdrawn EP2935203A1 (en) | 2012-12-19 | 2013-12-18 | Continuous method for separating salts in the production of dimethylacetamide |
Country Status (5)
Country | Link |
---|---|
US (1) | US20150329477A1 (en) |
EP (1) | EP2935203A1 (en) |
JP (1) | JP2016505583A (en) |
CN (1) | CN104981453A (en) |
WO (1) | WO2014095999A1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN114507924B (en) * | 2022-02-21 | 2023-03-03 | 恒天重工股份有限公司 | Steam recycling method for post-processing of synthetic fibers |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2176152A (en) * | 1938-03-02 | 1939-10-17 | Goslin Birmingham Mfg Company | Evaporator |
DE102004058887A1 (en) * | 2004-12-06 | 2006-06-08 | Basf Ag | Process for the preparation of N, N-dimethylacetamide (DMAC) |
DE102004058886A1 (en) * | 2004-12-06 | 2006-06-08 | Basf Ag | Process for the preparation of N, N-dimethylacetamide (DMAC) |
CN102807500B (en) * | 2012-08-13 | 2014-04-23 | 西南化工研究设计院有限公司 | Method for liquid-phase preparation of N, N-dimethylacetamide |
-
2013
- 2013-12-18 US US14/653,094 patent/US20150329477A1/en not_active Abandoned
- 2013-12-18 EP EP13815464.6A patent/EP2935203A1/en not_active Withdrawn
- 2013-12-18 CN CN201380072725.5A patent/CN104981453A/en active Pending
- 2013-12-18 JP JP2015548481A patent/JP2016505583A/en not_active Withdrawn
- 2013-12-18 WO PCT/EP2013/077087 patent/WO2014095999A1/en active Application Filing
Non-Patent Citations (1)
Title |
---|
See references of WO2014095999A1 * |
Also Published As
Publication number | Publication date |
---|---|
WO2014095999A1 (en) | 2014-06-26 |
CN104981453A (en) | 2015-10-14 |
JP2016505583A (en) | 2016-02-25 |
US20150329477A1 (en) | 2015-11-19 |
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