Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/54—Nitrogen compounds
  • B01D53/58—Ammonia
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D1/00—Evaporating
  • B01D1/28—Evaporating with vapour compression
  • B01D1/2803—Special features relating to the vapour to be compressed
  • B01D1/2818—Cleaning of the vapour before compression, e.g. demisters, washing of the vapour
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D1/00—Evaporating
  • B01D1/28—Evaporating with vapour compression
  • B01D1/284—Special features relating to the compressed vapour
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/38—Removing components of undefined structure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/72—Organic compounds not provided for in groups B01D53/48 - B01D53/70, e.g. hydrocarbons

Definitions

• the present invention relates to a method for cleaning vapour of gaseous impurities by scrubbing the vapour in several steps at different pH values, preferably in at least one acid step and one alkaline step.
• acid step and alkaline step refer to steps in which an acid reaction, respectively an alkaline reaction, takes place. Thus, they do not refer to specific pH-value sizes in the acid and alkaline area, respectively.
• the invention also relates to an apparatus for use by said method.
• the method and the apparatus may be used for cleaning and separating polluted liquids during their evaporation.
• industrial waste water degreasing water
• organic liquids such as manure, food production wastes etc.
• impurities refer to elements that are undesirable in the clean condensed liquid fraction, which is generally water.
• the impurities may e.g. be alcohols, ammonia, acetic acid, etc.
• vapour is conducted from the evaporation location, the boiler, via a compressor to the condensation location, a heat exchanger, in which the vapour is condensed.
• the vapour being conducted from the boiler to the heat exchanger will con ⁇ tain the same gases or vapours in gaseous form as those present in liquid form in the polluted liquid in the boiler.
• the combination of impurities in the gas or the vapour will depend on the substances present in the polluted liquid being evaporated. Impurities in the gas will also depend on their being miscible, finitely miscible or non-miscible. Furthermore, the partial pres ⁇ sures of the various components at the evaporation temperature in question will also influence the composition of the impurities in the gas.
• a number of different principles are known for using scrubbers to clean a polluted gas of undesirable gaseous pollutions. This is known e.g. from the disclosures of FR 2,666,330. These methods are based on conducting the polluted gas through a liquid absorbing as much as possible of the polluted gas in liquid or ion form. It is important to use liquid with acid addition if the polluted gas has an alkaline reaction and, contrarily, with alkaline addition if the polluted gas has an acid reaction. In this process it is neces ⁇ sary to remove steam from the gas before scrubbing is performed.
• the method according to the present invention is characterised in that the vapour is produced by preceding evaporation of polluted fluids, that polluted vapour is formed by boiling in a boiler, that the vapour is conducted to a compressor where it is compressed, and thereafter to a heat exchanger in which clean vapour is con- densed, that the scrubbing of the vapour is performed between the boiler and the heat exchanger, and that the scrubbing is performed in a scrubbing media with a basic fluid corresponding to the condensate and at the boiling point temperature of said fluid.
• the apparatus of the invention is designed for cleaning vapour of gaseous impurities by said method and with the use of a scrubber having several steps that comprise scrubbing media with different pH values, preferably at least one acid and one alkaline step, said cleaning being performed during evaporation of polluted liquids, the apparatus being characterised in comprising a boiler in which the vapour is formed by boiling the pol- luted liquid, a compressor for compressing the vapour, and a heat exchanger in which clean vapour is condensed, and that said scrubber is arranged in a conduit between the boiler and the heat exchanger.
• the vapour formed during evaporation is conducted through two adjacent liquid steps in a position between boiling and condensation, and when operating at the boiling point temperature, it is possible to form a mechanically simple scrubber that will remove the gaseous impurities from the vapour for condensation.
• the gas which is clean after the scrubber, may be conducted into the heat exchanger and be condensed so that the condensate is clean without contents of acid or alkaline substances.
• the scrubber a balance of the liquid level of each scrubbing step is established automatically, and there is no need for preceding cleaning of the vapour before it is let into the scrubber.
• the method of the apparatus according to the invention is particularly suitable for use in evaporation of pig manure, in which polluted gases are present in the shape of ammo- nium and acetates.
• polluted gases are present in the shape of ammo- nium and acetates.
• the method will not just be suitable for manure but also for other polluted liquids such as freons, cutting oils, etc., in which impurities are present that may be cleaned out of the gas by a method known per se in a scrubber having alkaline and acid reaction. If vapour is cleaned during the evaporation of manure, only two steps will be required, but it is possible to use several steps having different pH values. Thereby it is possible to obtain savings in the consumption substances used. During evaporation, the pH is kept relatively constant in order to maintain the same efficiency in cleaning.
• scrubbing is performed in an insu ⁇ lated cabinet in which boiling and condensation also take place so that the entire system is energy neutral as there is no interaction with the surroundings.
• boiling and condensation also take place so that the entire system is energy neutral as there is no interaction with the surroundings.
• figure 1 shows a schematic plant with an apparatus according to the invention, said ap- paratus being particularly suited for evaporation of pig manure;
• figure 2 shows a specific embodiment of the apparatus according to the invention.
• Figure 1 illustrates schematically a plant with an apparatus according to the invention.
• the plant is constructed for separation of polluted liquids by mechanical vapour com ⁇ pression.
• the plant is run according to a known principle for separating a polluted liquid part, preferably water, and concentrate the polluted part.
• the primary liquid part to be cleaned may consist of water but may also consist of other liquids such as freon polluted by oil.
• the plant comprises an evaporator 1.
• a distributor system 2 is arranged, and at the bottom a vessel 3 containing the polluted liquid 4 is arranged.
• the vessel 3 is connected with a circulation pump 5 and a conduit 6 pumping the heated and polluted liquid 4 to the distributor system 2 in the evaporator top.
• the vessel 3 has an inlet 7 for feeding polluted liquid 4, and a discharge conduit 8 used for emptying the concentrated and polluted part out of the boiler 3.
• a vapour outlet 9 which is connected via a conduit 10 and a compressor 11 to a heat exchanger 12 positioned in the evaporator 1.
• In the bottom of the heat exchanger 12 is an outlet 13 for condensate.
• a scrubber 14 is inserted in the conduit 10, where the compressor 11 is mounted, too. In the situation shown, the scrub ⁇ ber 14 is located upstream of the compressor 11. This is preferred, but it is also possible to position the scrubber 14 downstream of the compressor 11.
• the polluted liquid 4 is added in portions at the inlet 7 and let out via the discharge conduit 8 after a concentration has taken place.
• the condensate or distillate is removed via the outlet 13.
• the illustrated level 21 is obtained. This causes a level switch 22 to shift so that a heating member (not shown) and the circulation pump 5 are turned on. Thereafter, the temperature is brought to a temperature and pressure state lying immediately below the boiling point of the liquid to be cleaned (the condensate). Thus, in the case of water, the temperature is brought to nearly 100°C.
• the circulation pump 5 is turned on when starting the plant in order to ensure that all components have the same temperature.
• the compressor 11 When the temperature has reached approxi ⁇ mately 100°C, the compressor 11 is turned on.
• the compressor 11 creates a low pressure in the vessel 3, thus forcing the vapour present over the polluted liquid 4 through the scrubber 14, whereupon vapour is conducted via the conduit 10 to the compressor 11 and then into the heat exchanger 12, where there is a heat exchange of the vapour on one side of the heat exchanger and the heated polluted liquid 4 on the other side of the heat exchanger.
• This will cause the vapour having been compressed in the compressor 11 to deliver its energy, which is transferred to the circulated polluted liquid 4 on the other side of the heat exchanger. This will make the liquid to be cleaned evaporate.
• This va ⁇ pour travels through the heat exchanger 12 via its first side and thus flows into the top of the vessel 3 and will flow via the vapour outlet 9 and through the scrubber 14, the con- duit 10 and the compressor 11 into the heat exchanger 12. While delivering its energy, the vapour is condensed and may subsequently be removed as condensate via the outlet 13.
• the scrubber 14 comprises a first and a second scrubber 15, 16.
• the scrubber 15 con- tains an acid 17, and the scrubber 16 contains a base 18.
• Either scrubber 15, 16 is pro ⁇ vided with an inlet line 19, 20 for feeding acid and base, respectively. Thus, it is possi ⁇ ble on the basis of measurements to replace liquids 17, 18 so the pH is kept substantially constant during evaporation.
• the scrubber 14 will preferably be arranged with the acid step 15 upstream of the alkaline step 16. This order is important as the acids are more volatile than the bases. In order to retain what remains in the latter step of the scrubber
• the entire system is contained within a closed and insulated cabinet 21.
• an energy-neutral process is obtained as there is no interaction with the surroundings.
• this will also mean that the vapour is prevented from undesirable con ⁇ densing in a step having a lower temperature. If there were "cold steps", the process would come to a halt as the vapour would just condense in such a cold step in stead of the desired condensing in the heat exchanger 12.
• the scrubbers 15, 16 are provided with fillers 23 for damping the formation of bubbles, splashing and the like, which gives rise to sprays of liquid and thus the risk of drops being thrown out into the vapour conduit 10.
• These fillers will preferably be stones. In this manner it will be possible to prevent too violent dashing of liquid as the vapour bubbles up through the liquids 17, 18 in the scrubbers 15, 16.
• FIG. 2 shows an embodiment of a scrubber 14 being provided with more than two steps.
• the scrubber comprises three acid steps 17A, 17B and 17C.
• the scrubber further comprises an acid (should read “alkaline", confer e.g. line 23. Translator's note) step 18.
• the scrubber 14 has a substantially cylindrical shape with conduits etc. posi ⁇ tioned within a cylindrical sleeve 24.
• the scrubber is connected with an inlet for acid 19, an inlet 25 for water formed in the apparatus, and an inlet 20 for base.
• the scrubber comprises an outlet 25 for used acid and an outlet 26 for used base.
• the outlet is con ⁇ nected with overflow pipes 27, 28, respectively, and the outlet takes place when a liquid surface 29 reaches an upper end of the outlet pipes 27, 28.
• the acid step 17C gases bubble up through a central stub 30 and are forced down through the liquid contained therein, which consists of water that is acidified very slightly due to the volatile character of acid.
• these volatile acids form an acid so- lution, which runs via an overflow pipe 31 down into the first step 17A in order to ob ⁇ tain an initial cleaning of the gas flowing into the first step, a stub 32.
• the second step 17B in which acid is added via the inlet 19, the gas enters via a stub 33. After passage in the liquid contained therein, there may still, as mentioned above, appear certain acid remnants which are caught in the subsequent step 17C.
• the liquid in the acid step 17B is let via an overflow 34 into the first step 17 A with the liquid from the overflow pipe 31.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Analytical Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Biomedical Technology (AREA)
• Treating Waste Gases (AREA)
• Gas Separation By Absorption (AREA)
• Cleaning By Liquid Or Steam (AREA)
• Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

Priority Applications (8)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8098435

Family Applications (1)

Country Status (10)

Cited By (1)

Families Citing this family (13)

Citations (5)

Family Cites Families (7)

• 1994
  • 1994-07-22 DK DK086894A patent/DK86894A/da unknown
• 1995
  • 1995-07-19 CA CA002195298A patent/CA2195298C/en not_active Expired - Fee Related
  • 1995-07-19 WO PCT/DK1995/000310 patent/WO1996003191A1/en active IP Right Grant
  • 1995-07-19 JP JP8505371A patent/JPH11503959A/ja active Pending
  • 1995-07-19 DE DE69501897T patent/DE69501897T2/de not_active Expired - Fee Related
  • 1995-07-19 US US08/765,728 patent/US5928412A/en not_active Expired - Fee Related
  • 1995-07-19 DK DK95926376T patent/DK0773820T3/da active
  • 1995-07-19 AU AU30743/95A patent/AU3074395A/en not_active Abandoned
  • 1995-07-19 ES ES95926376T patent/ES2117432T3/es not_active Expired - Lifetime
  • 1995-07-19 EP EP95926376A patent/EP0773820B1/en not_active Expired - Lifetime
• 1996
  • 1996-01-16 TW TW085100451A patent/TW351681B/zh active

Patent Citations (5)

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