DE202021002328U1 - Device for water treatment by means of ion exchangers with regeneration with CO2 - Google Patents

Abstract

Device for softening and / or desalination of water by means of ion exchangers, wherein the device has at least one ion exchange filter (3, 12) through which raw water flows forwards in filter operation and wherein and the raw water to be treated is partially softened and / or partially desalinated by means of the ion exchanger, wherein A regeneration of the ion exchanger filter (3, 12) is carried out regularly by means of a backward flow through the ion exchanger filter (3, 12) with at least CO ₂ -containing water, characterized in that the device is followed by a downstream ion exchange filter (3, 12) in regeneration mode with backward flow _{Has regeneration water membrane desalination (6), by means of which the CO 2} -containing wastewater occurring during the regeneration of the ion exchanger filter (3, 12) is treated, in particular that regeneration water membrane desalination (6) is a nanofiltration and / or reverse osmosis .

Description

The invention relates to a device for softening and / or desalination of water by means of ion exchangers, the device having at least one ion exchange filter through which raw water flows forward in filter operation and wherein and the raw water to be treated is partially softened and / or partially desalinated by means of the ion exchanger, whereby regularly a regeneration of the ion exchanger filter is carried out by means of a backward flow through the ion exchanger filter with water containing _{at least CO 2.}

Such methods and devices are from DE 198 01 174 A1 and the DE 10 2006 050 608 A1 known.

Ion exchangers or ion exchange resins, which are synonymous with them, are plastic balls with a diameter of, for example, 0.8 mm, on which immobile ions are permanently chemically attached. The terms ion exchanger and ion exchange resin are used synonymously for the purposes of the invention. This ion is part of the resin structure and is called the active group. In order for the resin to maintain its electrical neutrality, each of these immobile ions must be balanced by a counterion. These counterions can migrate back and forth within and between the resin spheres and the surrounding water. The ion exchange resins are filled into pressure vessels and the water flows through them from top to bottom. In the so-called loading process, the resins exchange these freely movable ions for the higher-valued cations (Ca, Mg) and anions (SO4, NO3, Cl) from the raw water. If all the places on the exchanger are occupied, this process must be reversed by means of a regeneration. The regeneration of the ion exchange resins can advantageously be carried out with the product carbon dioxide CO 2 formed during loading.

During regeneration, raw water is pumped into a regeneration storage tank via a regeneration pump and enriched with CO2 under a certain overpressure. This regeneration solution is pressed from the bottom up through the ion exchanger from the regeneration storage tank. The salty wastewater (eluate) is then atomized in the eluate gas under atmospheric or negative pressure. In the gas phase of the Elau degasser, approx. 80 to 98% of the CO2 is sucked in with an oil-free compressor and returned to the regeneration storage tank.

The disadvantage here is the very high amount of energy required to recover the carbon dioxide CO ₂ contained in the salty waste water from the regeneration.

The object of the invention is to provide an improved method and an improved device in order to enable an energy-saving operation for the recovery of the carbon dioxide CO ₂ contained in the salty waste water from the regeneration.

This object is achieved according to the invention by the device according to claim 1. Advantageous further developments of the invention are given in the dependent claims.

Particularly advantageous in the method for softening and / or desalination of water by means of ion exchangers, with raw water flowing through at least one ion exchanger filter containing ion exchangers in filter operation and the raw water to be treated being partially softened and / or partially desalinated by means of the ion exchanger, with regular regeneration of the ion exchanger filter by means of a regeneration operation Backward flow through the ion exchanger filter _{is carried out with at least CO 2 -containing water, it is that the CO 2} -containing wastewater occurring during the regeneration of the ion exchanger filter is treated by means of a regeneration water membrane desalination connected downstream in the regeneration operation and the CO ₂ -containing water on the pure water side of the regeneration water membrane is desalination returned to the raw water side of the regeneration and the CO ₂ not consumed during the regeneration is recycled with the CO ₂ -containing water will.

The method can be used in particular for drinking water treatment or for process water treatment in industrial processes as well as in food production.

The wastewater (eluate) with a high _{concentration of CO 2 that occurs} during regeneration is treated by means of a regeneration water membrane desalination. These membranes hold back dissolved ions, but allow dissolved gases such as CO ₂ to pass freely. Therefore, the CO ₂ contents on the raw, pure water and concentrate side are roughly the same. The permeate is returned to the raw water side of the regeneration and thus the CO ₂ not consumed during the regeneration is circulated. The concentrate of the membrane system is passed over the eluate gas and for this then much smaller partial flow, the CO _{2 is} returned to the regeneration storage unit by means of oil-free compressing units.

_{Thus, the CO 2} -containing that accumulates during the regeneration of the ion exchanger filter becomes Wastewater (eluate) is treated by means of a regeneration water membrane desalination connected downstream in the regeneration operation and the CO ₂ -containing water on the pure water side of the regeneration water membrane desalination, which acts as a salt sink and thus prevents an accumulation of salts during the regeneration, is returned to the raw water side of the regeneration and thus the Regeneration of unused CO2 from the eluate in a cycle.

Since the provision and recovery of CO _{2 is} very costly, it is particularly advantageous that while a regeneration of the ion exchanger is being carried out from the _{eluate which is still highly CO 2} -containing, CO _{2 is} circulated or recovered from a small partial flow.

Since only a significantly smaller partial flow of CO _{2 has to} be recovered by means of oil-free compressing units and returned to the regeneration store, this results in considerable energy savings compared to the prior art. Compared to conventional regeneration with CO ₂ according to the state of the art, the amount of waste water is reduced by up to 70%, the CO ₂ consumption is reduced by up to 30% and the energy consumption is reduced by up to 40%.

The wastewater from the regeneration water membrane desalination is preferably degassed by means of a downstream eluate degasser, with at least part of the CO _{2 being} sucked in by means of a compressor in the gas phase of the eluate degasser and fed into a regeneration reservoir

A weakly acidic cation exchanger or a strongly basic anion exchanger or a mixture of a weakly acidic cation exchanger and a strongly basic anion exchanger is preferably used as the ion exchanger.

If a mixture of weakly acidic cation exchangers and strongly basic anion exchangers is used, the mixing ratio can be in the range from 100: 1 to 1: 100. This makes it possible to adapt the ion exchanger to the respective requirements, i.e. to adapt the mixing ratio between weakly acidic cation exchanger and strongly basic anion exchanger to the raw water quality and, in particular, to the load of the raw water with trace elements.

The regeneration water membrane desalination is preferably a nanofiltration and / or a reverse osmosis. These membranes hold back dissolved ions, but allow dissolved gases such as CO ₂ to pass freely.

The raw water used for the regeneration is preferably enriched _{with CO 2} before it is introduced into the ion exchange filter, in particular under an overpressure in a regeneration store. The enrichment with CO ₂ improves the regeneration effect of the ion exchange resins. The term ion exchange filter denotes that assembly which comprises a flow-through container containing ion exchange resins.

Preferably, several ion exchange filters are connected in parallel and at least one ion exchange filter is flowed through forwards by raw water in the filter operation and at least one other ion exchange filter is simultaneously flowed through and regenerated by CO ₂ -containing water in the regeneration operation.

Several, in particular two or three or four or more ion exchange filters each containing an ion exchange bed can thus be connected in parallel. In particular, at least one ion exchange filter can be used for water treatment, while at the same time at least one other ion exchange filter is being regenerated and / or backwashed.

By arranging several ion exchange filters connected in parallel, the continuous operation of the system can be guaranteed by, for example, with the arrangement of three ion exchange filters connected in parallel, one ion exchange filter is in use while another ion exchange filter is being regenerated and backwashed and the third ion exchange filter is on hold after regeneration and backwashing has been carried out is.

Preferably, a partial or full flow of the pure water is processed in filter operation by means of a pure water membrane desalination downstream of the ion exchange filter, the CO ₂ -containing wastewater from this pure water membrane desalination being used to regenerate an ion exchange filter, in particular being introduced into a regeneration tank.

The raw water is desalinated by means of an ion exchanger (use of cation and anion resin) or softened (use of cation resin). This loading creates carbon dioxide CO ₂ . A partial or full flow of this pre-desalinated or softened water then goes to a pure water membrane desalination. The pure water (permeate) of this membrane system is fed into the pure water flow of the entire system and that Wastewater (concentrate) is reused, for example, to regenerate an ion exchanger connected in parallel in the system that is in regeneration mode.

The pure water membrane desalination is preferably a nanofiltration and / or a reverse osmosis.

The ion exchanger is preferably used in the form of an ion exchanger bed, by means of which solids are filtered from the raw water, which are rinsed out during regeneration and backwashing of the ion exchanger and discharged as waste water.

The electrical conductivity of the pure water of the ion exchanger filter is particularly preferably monitored and a regeneration of the ion exchanger filter is triggered when a definable limit value for the electrical conductivity of the ion exchanger drain is exceeded.

The term “ion exchanger drain” means the water exiting from the ion exchanger filter on the pure water side after the treatment of the raw water with the ion exchanger.

In a preferred embodiment of the process according to the invention, the raw water to be treated is divided into two or more substreams.

A first partial flow of the raw water to be treated is preferably treated by means of the ion exchanger, with a second partial flow of up to 90% of the raw water being passed through a bypass and the two partial flows being mixed on the pure water side, the proportion of the partial flow passed through the bypass depending on the electrical conductivity of the raw water and / or as a function of the electrical conductivity of the ion exchanger flow and / or as a function of the electrical conductivity of the pure water after the mixing of the two partial flows is regulated.

This enables regulated bypass operation. The proportion of the raw water which is passed through the bypass is regulated within a closed control loop as a function of the water quality of the raw water and / or the ion exchanger drain and / or the pure water. In this way, depending on the raw water quality, a corresponding energy optimization of the entire system operation is possible, in that only a partial flow of the raw water to be treated is treated by means of the ion exchanger if the raw water quality is good, while a second partial flow of up to 90% of the raw water is routed via a bypass.

Depending on the raw water quality, the first partial flow can be up to 100% corresponding to a complete treatment of the raw water to be treated. The second substream, which is passed via the bypass and mixed with the ion exchanger outlet, can contain up to 10%, in particular up to 20%, in particular up to 30%, in particular up to 40%, in particular up to 50%, in particular up to 60% %, in particular up to 70%, in particular up to 80%, in particular up to 90% of the raw water mass flow.

Furthermore, a purge air fan can be provided to loosen up the ion exchange resin bed and to restore a homogeneous mixed bed. A mixture of weakly acidic cation exchangers and strongly basic anion exchangers is preferably used. The anion exchanger is a resin with functional cationic groups. The cation exchanger is a resin with functional anionic groups.

A regeneration of the ion exchanger is particularly preferably triggered by backwashing the ion exchanger filter with _{water containing CO 2} when a definable limit value for the electrical conductivity of the ion exchanger drain is exceeded.

This means that the electrical conductivity of the treated water on the pure water side of the exiting water is monitored, with a regeneration of the ion exchanger being triggered if necessary if a definable limit value is exceeded. It is particularly advantageous that the regeneration is not carried out on a regular basis after a certain number of bed volumes, but is only regenerated and / or backwashed as required if the quality of the water treatment declines and a regeneration of the ion exchanger filter is therefore necessary. This means a great saving in energy, since the regeneration is very energy-intensive. The electrical conductivity of the ion exchanger drain is a measure of the salt content in the ion exchanger drain and is thus directly correlated with the ability of the ion exchanger filter to carry out the partial desalination of the water. By triggering the regeneration as required, considerable energy savings can be achieved instead of a regular implementation after a certain number of bed volumes has been reached.

The fact that the regeneration of the ion exchanger filter is required as a function of the If the water quality of the ion exchanger is carried out and at least a partial flow of _{water containing CO 2 is} circulated during the regeneration, the energy and CO ₂ requirements are significantly reduced. In this case, permanent monitoring of the electrical conductivity of the ion exchanger process preferably takes place not only for the automatic resolution of a regeneration, but also for the purpose of permanent quality monitoring of the drinking water treatment.

The same measured value of the electrical conductivity of the ion exchanger drain can be used to control the bypass mode in a closed control loop. Such a bypass mode of water treatment, in which up to 100% of the raw water mass flow is treated by means of the ion exchanger filter, or up to 90% of the raw water mass flow is conducted via a bypass, depending on requirements, further energy savings can be achieved.

Particularly advantageous in the device for softening and / or desalination of water by means of ion exchangers, the device having at least one ion exchange filter through which raw water flows forwards in filter operation and wherein and the raw water to be treated is partially softened and / or partially desalinated by means of the ion exchanger, whereby regularly a regeneration of the ion exchanger filter is carried out by means of a backward flow through the ion exchanger filter with at least CO ₂ -containing water, it is that the device has a regeneration water membrane desalination downstream of the ion exchanger filter in regeneration operation with reverse flow, by means of which the CO ₂ -containing during regeneration of the ion exchanger filter Wastewater is treated, in particular that regeneration water membrane desalination is a nanofiltration and / or reverse osmosis.

The wastewater (eluate) with a high _{concentration of CO 2 that occurs} during regeneration is treated by means of a regeneration water membrane desalination. These membranes hold back dissolved ions, but allow dissolved gases such as CO ₂ to pass freely. Therefore, the CO ₂ contents on the raw, pure water and concentrate side are roughly the same. The permeate is returned to the raw water side of the regeneration and thus the CO ₂ not consumed during the regeneration is circulated. The concentrate of the membrane system is passed over the eluate gas and for this then much smaller partial flow, the CO _{2 is} returned to the regeneration storage unit by means of oil-free compressing units.

The device preferably has a regeneration pump and a regeneration reservoir, raw water being pumped into the regeneration reservoir by means of the regeneration pump.

A connecting line is preferably arranged from the pure water side of the regeneration water membrane desalination, which is connected downstream in the regeneration mode with reverse flow, to the suction side of the regeneration pump, via which the CO ₂ -containing pure water of the regeneration water membrane desalination can be circulated to the regeneration storage tank.

The device particularly preferably has an eluate degasser downstream of the regeneration water membrane desalination and a CO _{2 compressor, at least part of the carbon dioxide CO 2 being} sucked in by means of the compressor in the gas phase of the eluate degasser and fed into a regeneration storage tank via a connecting line.

The device preferably has at least one pure water membrane desalination downstream of the ion exchanger filter in filter operation, by means of which a partial or full flow of the pure water is processed, the CO ₂ -containing wastewater from this pure water membrane desalination being used to regenerate an ion exchange filter and being introduced into a regeneration tank via a connecting line. In particular, the pure water membrane desalination can be a nanofiltration and / or a reverse osmosis.

• 1 Ein vereinfachtes Fließschema einer Wasseraufbereitungsanlage mit mehreren parallelgeschalteten Ionenaustauschern nach dem Stand der Technik;
• 2 eine schematische Darstellung der Regeneration eines Ionenaustauschers mit im Regenerationsbetrieb nachgeschalteter Regenerierwassermembranentsalzung;
• 3 eine schematische Darstellung des Filterbetriebs eines Ionenaustauschers mit im Filterbetrieb nachgeschalteter Reinwassermembranentsalzung.

An exemplary embodiment of the invention is explained below with reference to the figures. Show it:

• 1 A simplified flow diagram of a water treatment plant with several ion exchangers connected in parallel according to the prior art;
• 2 a schematic representation of the regeneration of an ion exchanger with regeneration water membrane desalination following the regeneration operation;
• 3 a schematic representation of the filter operation of an ion exchanger with downstream pure water membrane desalination in the filter operation.

1 shows a simplified flow diagram of a water treatment plant according to the prior art with several ion exchangers connected in parallel 101 , 102 , 103 . The raw water flows through the ion exchange filter 101 , 102 , 103 , in whose filter bed the partial desalination takes place (nitrate, sulfate, chloride, calcium, magnesium, carbonate hardness reduction). With the regular regeneration of the In the filter bed, the ions adhering to the exchange resins are removed and the exchange resins are returned to their original state.

In the in 1 The flow diagram shown are two ion exchangers 101 , 102 in filter operation, during one of the ion exchangers 103 is in regeneration mode

For regeneration, raw water is fed into the regeneration storage tank via a regeneration pump 107 pumped and _{enriched with CO 2} from the recovery and from a CO ₂ tank 108. From the regeneration tank 107 the regeneration _{solution (CO 2} -enriched raw water) passes through the respective filter to be regenerated at an overpressure of approx. 6 bar 103 pressed. This results in regeneration water, which is referred to as the eluate. The eluate is made using an eluate degasser 106 degassed and the eluate reservoir 109 fed.

The pure water from the ion exchangers in the filter operation 101 , 102 is via a downstream pure water trickle 104 and finally the pure water storage tank 105 fed. _{The carbon dioxide CO 2} reaction product produced during loading in the filter operation is converted into the downstream pure water trickle 104 removed from the water by air stripping.

2 shows a schematic representation of the regeneration of an ion exchanger 3 with downstream regeneration water membrane desalination in regeneration mode 6th .

The regeneration water (eluate) with a high CO ₂ content that occurs during a regeneration is desalinated by means of a membrane 6th such as nanofiltration and / or reverse osmosis processed. These membranes hold back dissolved ions, but allow dissolved gases such as CO ₂ to pass freely. Therefore, the CO ₂ contents on the raw, pure water and concentrate side are roughly the same. The permeate is returned to the raw water side of the regeneration and thus the CO ₂ not consumed during the regeneration is circulated. The concentrate of the membrane system 6th is via the eluate gas 4th driven and for this then smaller partial flow, the CO _{2 is} by means of oil-free compressing units in the regeneration storage 2 returned.

During regeneration, raw water is generated using the regeneration pump 1 in the regeneration tank 2 pumped and enriched _{with CO 2} under a certain overpressure. From the regeneration tank 2 During the regeneration, this regeneration solution becomes from bottom to top through the ion exchanger 3 pressed. The saline regeneration water (eluate) is then desalinated through a membrane 6th guided. In membrane desalination 6th the eluate is desalinated by means of nanofiltration and / or reverse osmosis membranes, the CO ₂ content on both the permeate and concentrate side of the membrane system 6th corresponds to the inlet value. The desalinated and CO ₂ -containing permeate is transferred to the suction side of the regeneration pump 1 returned. _{The CO 2} not consumed during the regeneration is thus circulated. The _{concentrate containing CO 2} is degassed in the eluate 4th atomized at atmosphere or negative pressure. In the gas phase of the eluate degasser 4th comes with an oil-free compressing unit 5 Approx. 80 to 98% of the CO _{2 is} sucked in and into the regeneration tank 2 returned.

3 shows a schematic representation of the filter operation of an ion exchanger 12th with downstream pure water membrane desalination in filter operation 13th .

By desalination (use of cation and anion resin) or softening (use of cation resin) of the raw water in an ion exchanger 12th carbon dioxide CO _{2 is produced} . A partial or full flow of this pre-desalinated and CO ₂ -containing water then goes to a membrane system 13th such as nanofiltration and / or reverse osmosis. Due to the low salt content and the high content of excess CO ₂ at the same time, the inlet water of the membrane system is 13th So to speak, preconditioned, ie an additional dosage of acid or antiscalant is no longer necessary. The pure water (permeate) of the membrane 13th is added to the total pure water flow of the system and the waste water (concentrate) is used to regenerate an ion exchanger connected in parallel. As a result, the amount of waste water from the ion exchange system is not increased and at the same time the high pressure on the concentrate side of the membrane can 13th can be used directly to regenerate an ion exchanger without a further increase in pressure by means of a pump, which results in considerable energy savings.

The water to be treated can contain ingredients that are inadequate or not at all with an ion exchanger 12th can be reduced. This is a further advantage of the arrangement of a downstream pure water membrane desalination during filter operation 13th . This further increases the quality of the water treatment.

The raw water 11 is made by means of a first ion exchanger 12th desalinated (use of cation and anion resin) or softened (use of cation resin). This loading creates carbon dioxide CO ₂ . A partial or full flow of this pre-desalinated or softened water then goes to a membrane desalination 13th in the form of nanofiltration and / or reverse osmosis. That Pure water (permeate) of the pure water membrane desalination 13th is fed to the pure water flow of the entire system and the waste water (concentrate) is used for regeneration of one of the first ion exchangers 12th further ion exchanger connected in parallel and reused via the line 16 directed to the regeneration of this further ion exchanger. Which does not have the pure water membrane desalination 13th The partial flow of pure water (permeate) that is directed is passed directly through a bypass 14th the pure water flow 15th fed to the entire system.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 19801174 A1 [0002]
• DE 102006050608 A1 [0002]

Claims (5)

Device for softening and / or desalination of water by means of ion exchangers, wherein the device has at least one ion exchange filter (3, 12) through which raw water flows forwards in filter operation and wherein and the raw water to be treated is partially softened and / or partially desalinated by means of the ion exchanger, wherein A regeneration of the ion exchanger filter (3, 12) is carried out regularly by means of a backward flow through the ion exchanger filter (3, 12) with at least CO ₂ -containing water, characterized in that the device is followed by a downstream ion exchange filter (3, 12) in regeneration mode with backward flow _{Has regeneration water membrane desalination (6), by means of which the CO 2} -containing wastewater occurring during the regeneration of the ion exchanger filter (3, 12) is treated, in particular that regeneration water membrane desalination (6) is a nanofiltration and / or reverse osmosis t. Device according to Claim 1 , characterized in that the device has a regeneration pump (1) and a regeneration storage tank (2), raw water being pumped into the regeneration storage tank (2) by means of the regeneration pump (1). Device according to Claim 1 or 1 , characterized in that a connection line is arranged from the pure water side of the regeneration water membrane desalination (6) connected downstream in the regeneration mode with reverse flow to the suction side of the regeneration pump (1), via which the CO ₂ -containing pure water of the regeneration water membrane desalination (6) in a circuit to the regeneration storage tank (2 ) can be performed. Device according to one of the Claims 1 until 3 , characterized in that the device has an eluate degasser (4) connected downstream of the regeneration water membrane desalination (6) and a CO ₂ compressor (5), with at least a part in the gas phase of the eluate degasser (4) by means of the CO _{2 compressor (5)} of the carbon dioxide CO _{2 is} sucked in and introduced into a regeneration storage tank (2) via a connecting line. Device according to one of the Claims 1 until 4th , characterized in that the device has at least one pure water membrane desalination (13) downstream of the ion exchanger filter (3, 12) in filter operation, by means of which a partial or full flow of the pure water is processed, the CO ₂ -containing wastewater for this pure water membrane desalination (13) Regeneration of an ion exchanger filter is used and is introduced into a regeneration store (2) via a connecting line (16), in particular that the pure water membrane desalination (13) is a nanofiltration and / or reverse osmosis.

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