Classifications

• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
  • C02F5/02—Softening water by precipitation of the hardness
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D1/00—Evaporating
  • B01D1/26—Multiple-effect evaporating
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/02—Treatment of water, waste water, or sewage by heating
  • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/02—Treatment of water, waste water, or sewage by heating
  • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
  • C02F1/042—Prevention of deposits
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F2001/007—Processes including a sedimentation step
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
  • C02F2001/5218—Crystallization
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2101/00—Nature of the contaminant
  • C02F2101/10—Inorganic compounds
  • C02F2101/101—Sulfur compounds
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
  • C02F2103/08—Seawater, e.g. for desalination
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
  • Y02A20/124—Water desalination

Definitions

• This invention relates to desalination systems and methods, in particular a method using multi-effect evaporators.
• Distillation of water being a commonly used method of desalination, is a process in which various soluble materials such as salt, contaminants etc. are eliminated from water containing these materials, leaving clean, usually drinkable water.
• One known method for achieving such distillation relies on water evaporation, much like salt and scale being accumulated on the bottom of an electric kettle after water has evaporated. In this process during evaporation of the water, soluble materials that are not volatile remain in a solid state residue, usually in the form of salt and scale, and are disposed of. The vapor can then be condensed back into the state of liquid, resulting in contaminant free water.
• ZLD zero liquid discharge
• a system for desalination of seawater W having an original water salinity and a original water concentration of scale forming components comprising: - a pre-treatment sub-system for at least partial removal from said water W of said scale forming components, producing thereby a pre-treated feed water having a first concentration of scale forming components lower than said original concentration of scale forming components;
• a forward feed flow multi-effect evaporator adapted for distillation of said pre- treated feed water, producing thereby main desalted water product WM having a desalted water salinity lower than said water salinity, and main brine having a salt concentration of approximately 10%.
• a concentrator adapted for receiving therein said main brine and concentrating it, producing thereby more concentrated brine with an increased salt concentration of approximately 20%-22%, and releasing a first additional desalted water product W 1 ; and a crystallizer for receiving said more concentrated brine, adapted for crystallization thereof to obtain at least solid salt products and releasing a second additional desalted water product W 2 .
• the scale forming components are at least sulfate ions.
• the pre-treatment system may further comprise at least de-carbonization columns adapted for removing said sulfate ions.
• the scale forming components are at least calcium ions.
• the pre-treatment system may further comprise a reactor adapted for creating calcium carbonate by reacting said calcium ions with soda ash.
• the pre-treatment system may further comprise a clarifier adapted for removing said calcium carbonate.
• the concentrator may further constitute a part of a single multi-effect evaporator/concentrator installation.
• the concentrator may further constitute a part of a single multi-effect concentrator/crystallizer installation.
• a method of desalination of a seawater having a original water salinity and a concentration of scale forming components comprising: - at least partial removal from said seawater of said scale forming components and producing a pre-treated feed water having a first concentration of scale forming components lower than said feed water concentration of scale forming components;
• the method may further comprise removing said scale forming components by means of de-carbonization columns.
• the method may further comprise removing said scale forming components by means of a reactor and a clarifier.
• the method may further comprise producing said main brine by said evaporator.
• the method may further comprise providing a concentrator.
• the method may further comprise producing said more concentrated brine by said concentrator.
• FIG. 1 schematically illustrates one example of a system according to the present invention.
• Fig. 2 schematically illustrates another example of a system according to the present invention.
• Figs. 1 and 2 schematically show two examples of a system for seawater desalination according to the present invention, designated as 10 and 30, respectively.
• the system 10 comprises a pre-treatment sub-system 11, a multi-effect evaporator 13 with its associated feed heater 21, a concentrator 17 (not shown) combined with a crystallizer 19 (not shown) in one common multi-effect concentrator/cry stallizer installation 15, which has a succession of corresponding primarily concentrating (PC) effects and primarily crystallizing (PCR) effects.
• the concentrator 17 and the crystallizer 19 may further be two distinct separate installations.
• the system 30 comprises a pre-treatment sub-system 31, a multi- effect evaporator 33 with its associated feed heater 41, the evaporator 33 (not shown) incorporating a concentrator 37 (not shown) in one common multi-effect installation 35, having a succession of corresponding primarily desalinating (PD) effects and primarily concentrating (PC) effects, and a crystallizer 39.
• a pre-treatment sub-system 31 a multi- effect evaporator 33 with its associated feed heater 41
• the evaporator 33 (not shown) incorporating a concentrator 37 (not shown) in one common multi-effect installation 35, having a succession of corresponding primarily desalinating (PD) effects and primarily concentrating (PC) effects
• PD desalinating
• PC primarily concentrating
• Each of the systems 10 and 30 further comprises three condensers 12, 14 and 16.
• the condenser 12 is a falling film condenser and the condensers 14 and 16 are forced circulation condensers.
• the construction of the condensers 12, 14 and 16 is known per se.
• the systems 10 and 30 further comprise a steam supply system 50 (not shown) for supplying vapor to the systems, as will be explained below.
• seawater W first enters the pre-treatment sub-system 11 where predetermined scale forming components, such as carbonate, are removed therefrom and it is fed as feed water W F , via the condenser 12 and the feed heater 21, to the multi-effect evaporator 13, where main desalination process takes place and three main products are produced: main desalted water W M (not shown) which constitutes a majority of total water product W TOTAL outcoming from the multi-effect evaporator 13, main brine B M proceeding to further treatment in the desalination system, and a first condensate return Ri flowing back to the steam supply system 50 and then is supplied as a vapor V 1 to the multi-effect evaporator 13.
• main desalted water W M (not shown) which constitutes a majority of total water product W TOTAL outcoming from the multi-effect evaporator 13
• main brine B M proceeding to further
• the condensers 12 and 14 produce additional desalted water W AI2 and W A14 , which is produced from a vapor V 1 ' and withdrawn as a part of the total water product W TOTAL -
• salts generally designated S and a bitterns solution BS which are then withdrawn from the system as products having a potential of being used in the desalination plant or outside thereof;
• W A1 which is a majority of the additional desalted water W A is obtained as a result of the concentration process which takes place in the concentrator 17 [or PC effects 17 of the of the multi-effect concentrator/crystallizer installation 15], during which a brine Bc (not shown) more concentrated than the main brine B M is produced.
• the brine Bc is then used in the crystallization process, resulting in the production of the salts S, the bitterns solution BS and some more additional desalted water W A2 .
• the multi-effect evaporator 13 has evaporator inlets 13a to 13c.
• the inlet 13a is adapted for receiving therein the feed water Wp
• the second inlet 13b is adapted for receiving therein the vapor Vi for use in the desalination process
• the third inlet 13c is adapted for receiving therein the additional desalted water W A coming from the multi-effect concentrator/crystallizer installation 15.
• the evaporator 13 further comprises four evaporator outlets, namely, the outlet 13d for discharging therefrom the main product W TOTAL , the outlet 13e for discharging therefrom the main brine B M , the outlet 13f for discharging therefrom the first condensate return R 1 and the outlet 13g for discharging therefrom vapor Vi' to the condensers 12 and 14.
• the concentrator/crystallizer installation 15 has two inlets, 15a and 15b, for receiving therein the main brine B M and the vapor V 2 , respectively. It further has five outlets 15c to 15g, for discharging therefrom vapor V 2 ' that goes to the condenser 16, the additional desalted water W A , the bitterns solution BS, salts S and the second condensate return R 2 , respectively.
• the outlet 15f refers to a group of outlets for discharging therefrom of different kinds of salts.
• salts S produced as a result of the crystallization process in the multi-effect concentrator/crystallizer installation 15 from the brine product Bc are industrial salt NaCl and calcium sulfate CaSO 4 .
• the pre-treatment sub-system 11 is adapted to remove from the seawater W mostly sulfate ions SO 4 2" .
• the pre-treatment system 11 may comprise de-carbonization columns 18, where acid is added to the seawater feed W and most of the sulfate ions SO 4 2" are removed.
• the sulfate ions may be substituted with anions such as chloride Cl " .
• the sulfate may be regenerated with a salt, such as Potash KCl or common salt NaCl. In this case, the solution of the respective sulfate will be created, from which a saleable commodity may be recovered by means known per se.
• the alkalinity is further removed from the seawater feed together with the sulfate.
• One particular example of the multi-effect evaporator 13 that may be used in the system 10 is of so-called 'forward feed flow 1 type, in which the feed water and the vapor both move downstream during the process.
• the evaporator may for example be of the kind described in detail in PCT/IL2006/000302, which in its entirety is incorporated herein by reference.
• This evaporator 13 in the described example is adapted to desalt the water flowing therethrough so that the main brine B M released from the evaporator 13 has a salt concentration of approximately 10%.
• the evaporator according to the present invention may comprise tubes as described in the above publication or fluted oval tubes.
• the concentrator 17 or PC effects 17 of the multi-effect concentrator/crystallizer installation 15] used in the system 10 may be of any appropriate type known in the art, capable to concentrate the main brine BM of the above salt concentration, to the extent that the brine product Bc released therefrom has a salt concentration of approximately 20%-22%, allowing it to be further used in the production of salt products, in particular those indicated above, in the crystallizer 19.
• seawater W first enters the pre-treatment sub-system 31 where predetermined scale forming components are removed therefrom, and is fed as feed water WF, via the condenser 12 and the feed heater 41, to the combined multi-effect evaporator/concentrator installation 35.
• the feed water WF undergoes a desalination process in the PD effects 33, which results in the production of main desalted water WM constituting a majority of total water product WTOTAL outcoming from the multi-effect installation 35, and of main brine BM (not shown); and the main brine BM undergoes concentration in the PC effects 37 of the multi- effect installation 35, to produce brine Bc and additional desalted water WA 1 , which is then withdrawn as a part of the total water product WTOTAL-
• the condensers 12 and 14 produce additional desalted water WA 12 and WA 14 , which is withdrawn as a part of the total water product WTOTAL-
• the evaporator/concentrator installation 35 further produces a first condensate return Ri which flows back to the steam supply system 50 and then is supplied as a vapor V 1 to thereto.
• the brine Bc from the multi-effect installation 35 flows to the crystallizer 39, in which a crystallization process takes place, resulting in the production of: (i) salt S and bitterns solution BS, which are then withdrawn from the system as products having a potential of being used in the desalination plant or outside thereof;
• the multi-effect installation 35 has multi-effect installation inlets 35a to 35c.
• the inlet 35a is adapted for receiving therein the feed water W F
• the second inlet 35b is adapted for receiving therein the vapor V 1 for use in the desalination process
• the third inlet 35c is adapted for receiving therein the additional desalted water W A' coming from the crystallizer 39.
• the installation 35 further comprises four multi-effect installation outlets, namely, the outlet 35d for discharging therefrom the main product W JOTAL , the outlet 35e for discharging therefrom the brine product Bc, the outlet 35f for discharging therefrom the first condensate return R 1 and the outlet 35g for discharging therefrom vapor Vc that goes to the condensers 12 and 14.
• the crystallizer 39 has two crystallizer inlets, 39a and 39b, for receiving therein the brine product Bc and the vapor V 2 , respectively. It further has five crystallizer outlets 39c to 39g, for discharging therefrom vapor Vc that goes to the condenser 16, the additional desalted water W A2 , the bitterns solution BS, salts S and the second condensate return R 2 , respectively.
• the outlet 39f refers a group of outlets for discharging therefrom of different kinds of salts, is desired.
• the salt S produced by the crystallizer 39 is industrial salt NaCl.
• the pre-treatment sub-system 31 in such system 30 is adapted to remove substantially all calcium ions from the seawater W.
• the pre-treatment system 31 may comprise a reactor 43 and a clarifier 44. During the pre-treatment process calcium ions from the seawater W react with soda ash Na 2 CO 3 in the reactor 43 and hardly-soluble calcium carbonate CaCO 3 is created and then precipitates and removed from the seawater W in the clarifier 44.
• a soluble base such as caustic soda NaOH, in an amount substantially equivalent to the content of bicarbonate ion HCO 3 " in the seawater W, may be added thereto, thereby saving about one fourth of the required amount of soda ash.
• a soluble base such as caustic soda NaOH
• the multi-effect evaporator/concentrator installation 35 may have a configuration similar to that of the multi-effect evaporator 13, with a difference being mainly in that its PD effects 33 (not shown) are followed by the PC effects 37 (not shown).
• the brine B M produced by the PD effects 33 may have salt concentration of approximately 10%
• the brine Bc which produced therefrom by the PC effects 37 may have salt concentration of approximately 20%-22%.
• An additional difference between the PD and PC effects in the installation 35 may be in that at least a part of the pipes and tubes in the PC effects 37 may be made of material different from the material of the pipes and tubes in the PD effects, to better withstand increased salt concentration of the brine passing therethrough.
• Table 1 summarizes, in a non-limiting manner, parameters which the systems 10 and 30 may have, in accordance with the examples described above with reference to Fig. 1 and Fig. 2.
• Desalted water discharged from the crystallizer is calculated as follows:

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• 2009
  • 2009-09-06 CN CN200980134991.XA patent/CN102143786B/zh not_active Expired - Fee Related
  • 2009-09-06 EA EA201100433A patent/EA201100433A1/ru unknown
  • 2009-09-06 EP EP09736491A patent/EP2331224A1/de not_active Withdrawn
  • 2009-09-06 WO PCT/IL2009/000864 patent/WO2010026589A1/en active Application Filing
• 2011
  • 2011-04-04 ZA ZA2011/02466A patent/ZA201102466B/en unknown

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