Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
  • F23J15/00—Arrangements of devices for treating smoke or fumes
  • F23J15/02—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material
  • F23J15/04—Arrangements of devices for treating smoke or fumes of purifiers, e.g. for removing noxious material using washing fluids
• • 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
  • B01D53/48—Sulfur compounds
  • B01D53/50—Sulfur oxides
  • B01D53/501—Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
• • 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
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S261/00—Gas and liquid contact apparatus
  • Y10S261/09—Furnace gas scrubbers

Definitions

• the invention relates to a method for the cleaning and desulphurization of flue gas from the combustion of. sulphurous fuels, and the recovery of heat from said gas, whereby the flue gas is conducted from a boiler through a heat exchanger, and also a plant for use in the execution of the method.
• a flue gas arises which in accordance with the relevant environmental regulations must maintain stipulated norms in order to be able to be discharged into the atmosphere.
• the flue gas also contains a certain amount of thermal energy, even from boiler plants with economizers, whereby the feed water is heated by the flue gas before it is fed to the boiler plant. For reasons of economy, it is therefore desirable to recover as great an amount of the thermal energy as possible from the flue gas.
• a smoke cleaner in which a scrubber fluid, e.g. lime water, is used to remove acids and particles from the smoke, after which the flue gas can be conducted to the chimney and out into the atmosphere.
• a scrubber fluid e.g. lime water
• the smoke is cooled down considerably by using a flue- gas-air heat exchanger after the economizer, thus re ⁇ ducing the temperature of the flue gas to below the dew point of the acid, so that the acid is condensed and settles in the heat exchanger.
• This must there ⁇ fore be made of an acid-resisting material, e.g. acid-resisting steel or glass, which results in a very expensive heat exchanger.
• the flue gas from fossil fuels contains a smaller amount of lime connections, the result being that the particles in the flue gas become chalky and, in connection with the acid, thus form a gypsum paste which quickly blocks the heat exchanger.
• the heat exchanger must therefore be frequently cleaned, which is difficult.
• Known systems use vigorous flushing with water in or ⁇ der to clean the heat exchanger, but this gives rise to a ⁇ idiferous water which must be neutralized before it can be led away.
• the object of the invention is to provide a method and a plant which are not encumbered with the above- mentioned drawbacks.
• the dry process has the disadvantage that the consumption of lime is quite large and increases progressively with increased re ⁇ duction of the content of acid in the flue gas, to which must be added a greater amount of reject which has to be deposited.
• the dry/wet process reduces the consumption of lime and the reject in comparison to the dry process, but gives rise to cleaning problems between the dry and the wet zone because of the un- avoidable formations of gypsum.
• the wet process's consumption of lime is linearly related to the amount of acid it is desired to remove, which means that the lime consumption and the reject is less than with the two other processes.
• the difficulties with the wet process are that the undissolved particles of lime result in the formation of gypsum crystals in the plant, which must therefore be cleaned very frequent ⁇ ly.
• the turning-shield en ⁇ sures that the speed of the water in the reactor im ⁇ mediately after the turning-shield is almost uniform throughout the whole of the cross-section of the high-speed reactor, except for the area along the wall. Finally, the clearance between the wall of the reactor and the turning-shield results in the sludge being able to pass down the inner wall of the high ⁇ speed reactor, past the turning-shield and down into the base cone of the reactor under the turning- shield.
• claims 3-5 present advan ⁇ tageous means of regulation, whereby the whole of the process can be fully automated, e.g. by using the means as presented in claims 9-11.
• the flue gas is led through an econo ⁇ mizer (not shown in the drawing) where it is cooled to approx. 80°C, which is above the acid dew point for the flue gas, after which the flue gas is led through a possible filter where most of the particles in the flue gas are removed.
• the flue gas is conveyed through the smoke suction apparatus RS and further to the scrubber tower(s) ST with scrubbing elements 79.
• the flue gas is pressed vertically down through the tower and then passes horizontally through a sedimen ⁇ tation tank 75 and led to the chimney S.
• the smoke is washed by means of jets 78, scrubbing elements 79 and drip-catchers 86.
• the flue gas thereafter leaves the sedimen ⁇ tation tank 75, it is cooled down to 45-50°C. S0 2 and solid contents are reduced by 85-90% in relation to the amounts at the outlet from the filter.
• the water for jet system is taken from the sedimenta ⁇ tion tank 75 and is pressed by means of a pump 76 to nozzles or jets 78 in the scrubber tower(s) ST, after which it runs back to the sedimentation tank 75.
• a pump 36 is connected which forces water and sediment up into a downpipe 32 of a high-speed rea ⁇ - tor 30.
• the high-speed reactor 30 has increasing cross-sectional dimensions, so that one achieves a constantly decreasing water velocity.
• the high-speed reactor is in the form of a cone with the apex downwards.
• the turning-shield 33 is disposed in the vicinity of the pointed bottom, and is shaped in such a way that it fills out a relatively large part of the cross-sectional area, but not more than par ⁇ ticles etc. are able to sink down between the turning-shield and the wall of the reactor and are collected in the bottom of the cone.
• the water/sediment from the sedimentation tank 75 will be acid with a pH value of approx. 6.
• the sulphurous acid is neutra ⁇ lized with Ca (OH) 2 by means of a lime dosage system which is described in more detail in the following.
• Ca(0H) 2 is dispensed from a silo 22 to the mixing vessels 1 and 2 where it is mixed with water supplied via the valves 13 and 14. This is carried out under constant stirring by, for example, the mechanical stirrers 3 and 4, until an approx. 10% suspension is obtained, depending on the sulphur content of the fuel.
• a float 7 * switches the system to vessel 2, in that the solenoid valves 10 and 12 are opened and 9 and 11 are closed.
• a damper 20 is then reversed to vessel 1, whereby vessel 1 is filled with Ca(0H) 2 .
• a worm 21 conveys the Ca(0H) 2 to vessel 1.
• the solenoid valve 13 adds water to vessel 1.
• a float 5 halts the supply of water by closing the valve 13.
• vessel 2 is manoeuvred during filling by the floats 6 and 8.
• the amount of Ca(0H) 2 to be added is determined by a revolution counter on the shaft of the worm 21.
• a system with one or more collection vessels 40 is provided between the high-speed reactor 30 and the scrubber system.
• the water from the chamber RK surrounding the high- speed reactor 30 runs through a pipe 39 to the col ⁇ lection vessels 40.
• the water from the collection vessels runs over into a tank 47.
• This tank is provided with a pH sensor which controls a smoke throttle 46 for the supply of clean gas to the vessels 40. This is effected in such a way that the pH value is held at 7.0.
• the tank 47 is provided with a float 49. When the float 49 is in the uppermost position, a valve 51 is closed and a valve 50 is opened. When the float 49 is in the lower position, valve 51 opens and valve 50 closes.
• the water from the tank 47 runs down into the sedi ⁇ mentation tank 75.
• the amount which runs down into the sedimentation tank 75 is regulated by means of a pH sensor 80, in that a valve 81 opens when the pH value in the sedimentation tank 75 is below 6.0.
• Both the clean water through the valve 84 and the water from the tank 47 through the valve 81 are fed into the tank 75 via a funnel element 83.
• the sediment is separated from the water in the de- canter centrifuge 60.
• the sediment which is of a consistency which enables it to be shovelled, is col ⁇ lected in a container 63, while the reject runs down into a vessel 62 and is fed back into the system.
• the thermal energy in the scrubber fluid which ab ⁇ sorbs residual heat from the flue gas, can be re ⁇ covered by letting the scrubber fluid circulate through a water/air heat exchanger, for example a calorifier, which heats the combustion air before this is blown into the boiler plant.
• a calorifier instead of a calorifier, one can extract the thermal energy from the scrubber fluid by means of a heat pump arrange ⁇ ment.
• the high-speed reactor 30, the collection vessels 40 and the sedimentation tank 75 are filled with water to their normal levels.
• the plant will then start-up with the exception of the lime dosing pump 18 and the clean gas blower 45.
• the flue gas is fed through the scrubber tower ST and elements 79.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Environmental & Geological Engineering (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Treating Waste Gases (AREA)

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• 1986
  • 1986-06-04 DK DK265686A patent/DK160599C/da not_active IP Right Cessation
• 1987
  • 1987-06-03 AU AU75805/87A patent/AU7580587A/en not_active Abandoned
  • 1987-06-03 JP JP62503686A patent/JPS63503477A/ja active Pending
  • 1987-06-03 EP EP87903865A patent/EP0268655B1/en not_active Expired
  • 1987-06-03 WO PCT/DK1987/000067 patent/WO1987007701A1/en active IP Right Grant
  • 1987-06-03 US US07/148,510 patent/US4860670A/en not_active Expired - Fee Related

Patent Citations (5)

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