Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D47/00—Separating dispersed particles from gases, air or vapours by liquid as separating agent
  • B01D47/06—Spray cleaning

Definitions

• the present invention relates to a method for removing predominantly solid impurities from a scrubber liquid as described in the preamble of Claim 1.
• the invention also relates to an apparatus for carrying out the method according to the preamble of the first apparatus claim.
• the invention is mainly, but not solely, intended for use in processes and plants for manufacturing of fibre board, particle board and similar products.
• wood particles usually in the form of fibres
• a binder usually a resin
• a drying transport gas and steam evaporated from the particles during the drying process
• the transport gas is then led to a scrubber where it is cleaned.
• the thus cleaned gas may be reused in the process, partly or wholly.
• the concentration of impurities in the scrubber liquid is increased by the removal of particles and fumes from the transport gas.
• the increasing concentration mainly of solid particles, causes problems by clogging in the scrubber, especially as usually most of the scrubber liquid is recirculated and only the surplus, due to condensation of steam in the gas, is removed.
• the objective of the invention is therefore to create the conditions for taking charge of, first of all, the solid impurities in the gas which is to be cleaned, so that at least most of the particles are prevented from being recirculated in the scrubber and moreover are being removed there ⁇ from easily and efficiently.
• Another objective of the invention is to improve the technique in various ways within this area.
• Figure 1 shows a vertical section of a scrubber comprising a first embodiment of the invention and figure 2 shows in a similar perspective the lower part of a scrubber comprising a second embodiment of the invention.
• a scrubber in figure 1, comprises two cleaning ramps 2 at the top, with spray nozzles 3, the cleaning ramps being fed with cleaning or scrubber liquid via feeders 4, with a pump 5 sucking liquid from the lower part of the scrubber at an extraction level 6.
• the scrubber To the scrubber 1, preferably in the lower part, is connected an inlet pipe 7, for the gas that is to be cleaned. At the top the scrubber has an outlet pipe 8 for cleaned gas. At the bottom, which preferably is tapered, the scrubber is provided with a drainage outlet 9, at the lowest level, comprising a drainage valve 10.
• a collecting device 11 below the inlet pipe 7 but above the extraction level 6.
• the collecting device 11 opens into a passage 12, which runs centrally downwards to a level above the drainage outlet 9 but below a separation device 13, which is located on a level below the extraction level 6.
• the separation device 13 can be a strainer screen, a suitable sieve or a perforated plate.
• the holes can, in a practical design, have a diameter of 0.1 to 3 mm, preferably about 0.5 mm.
• the separation .device 13 covers the whole cross section of the scrubber.
• the separation device is replaceable and possibly vertically dirigible, so that for example a pressure shock may be absorbed without any damage to the apparatus. It should though be in a fixed position at the time of back flow cleansing.
• the collecting device 11 is preferably designed to follow the contour of the inside of the scrubber so that there is a surrounding gap 14 between the inner wall of the scrubber and the collecting device.
• This gap 14 works as an overflow means and as a pressure balance means.
• a high-level control sensor 15 Just below the gap 14 there is a high-level control sensor 15 and further down there is a low-level control sensor 16.
• the mentioned sensors 15, 16 are connected to a control unit 18 which is regulating the drainage valve 10.
• a differential pressure sensor 17 Between the levels of the separation device 13 and the low-level control sensor there is a differential pressure sensor 17.
• the control valve 19 should preferably be controlled by the same control unit 18 as the drainage valve 10.
• the function of the apparatus is as follows. Polluted gas, e.g. air at a temperature of 60-90 deg. C, containing fibres with binder, dust and fumes of phenol and formaldehyde, is fed through the inlet pipe 7 and moves upwards through the scrubber 1.Through the feeders 4, cleaning liquid is supplied to the cleaning ramps 2 from the pump 5. The cleaning scrubber liquid is sprayed through the moving polluted gas by the nozzles 3 and thereby absorbing solid, liquid and gaseous impurities. The cleaned gas leaves the scrubber through the outlet pipe 8.
• Polluted gas e.g. air at a temperature of 60-90 deg. C
• the cleaning scrubber liquid is sprayed through the moving polluted gas by the nozzles 3 and thereby absorbing solid, liquid and gaseous impurities.
• the cleaned gas leaves the scrubber through the outlet pipe 8.
• the scrubber liquid together with captured impurities is collected in the collecting device 11 and led through the passage 12 to the bottom area 21 of the scrubber, below the separation device 13, e.g. a sieve.
• the polluted liquid then rises through the separation device, where most of the solid impurities remains, to a middle chamber 22 filled with clean scrubber liquid around the extraction level 6 where liquid continuously is sucked to the pump 5 for recirculation.
• the liquid level in the middle chamber 22 is kept between the level of the high-level control sensor 15 and the level of the low-level control sensor 16. .
• the control unit 18 will open the drainage valve 10 for a predetermined period of time or until the liquid level reaches the low-level.
• liquid is flowing downwards through the separation device 13 to the drainage outlet 9 removing the solid impurities, which have gathered underneath the separation device and carrying these solid impurities out through the drainage outlet.
• Surplus fluid is normally derived from condensation of the humidity in the incoming polluted gas if this has a high water vapour content and if it has a temperature significantly higher than the temperature of the scrubber liquid, which should be kept at 25-40 deg. C. In cases, where the amount of surplus liquid is insufficient, fresh water is added regularly and the draining interval is determined by experience or by measuring of a differential pressure by the sensor 17.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Treating Waste Gases (AREA)
• Gas Separation By Absorption (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20373876

Family Applications (1)

Country Status (4)

Cited By (9)

Citations (3)

• 1988
  • 1988-11-07 SE SE8804025A patent/SE464220B/sv unknown
• 1989
  • 1989-11-03 WO PCT/SE1989/000628 patent/WO1990005015A1/en active Application Filing
  • 1989-11-03 DE DE19893991314 patent/DE3991314T/de not_active Withdrawn
  • 1989-11-03 AU AU45020/89A patent/AU4502089A/en not_active Abandoned

Patent Citations (3)

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