Agitating – Having specified feed means – Material introduced so as to cause rotary motion in mixing...
Patent
1987-03-10
1989-05-30
Hornsby, Harvey C.
Agitating
Having specified feed means
Material introduced so as to cause rotary motion in mixing...
366150, 366171, 366176, 55203, B01F 1502
Patent
active
048345474
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for mixing chemicals in fibre suspensions, particularly in high consistency cellulose pulps. The chemicals to be mixed in the pulp can be in a gaseous or liquid form.
Various devices are used in pulp industry for mixing chemicals in pulps. When the consistency is low, i.e. up to approximately 5%, mixing does not usually cause problems. At higher consistencies, e.g. 5-15%, mixing is, however, more difficult as the gas content, mostly air content, of the pulp increases with the rise of the consistency and only little liquid remains between the fibres. The air in the pulp interferes with the reaction of the chemicals and aggravates pumping of the pulp with a centrifugal pump.
BACKGROUND ART
Swedish patent application No. 7909781-2 discloses an apparatus for mixing treatment chemicals in suspensions. The apparatus comprises a mixing means consisting of a cylindrical portion provided with axial ribs, and of a larger discshaped portion provided with radial ribs. The housing of the apparatus is provided with corresponding stationary ribs. When the mixing means rotates the pulp flowing through the passages between the mixing means and the housing is fluidized and chemicals are efficiently mixed in the pulp.
U.S. Pat. No. 4,410,337 discloses an apparatus for separating gas from a fibre suspension, in which the fibre suspension is caused to rotate by a rotor provided with blades and disposed in the inlet channel of the apparatus so as to bring about a core of gas surrounded by fibre suspension, gas being discharged from the core to a separate gas space.
Further, Finnish patent application No. 823279 discloses an apparatus for mixing chemicals in fibre suspensions. The apparatus comprises a rotor provided with external protrusions and disposed in the casing in the inlet channel of the centrifugal pump in front of an impeller. The casing is provided with an opening or openings through which chemicals can be supplied to the space between the inlet channel and the rotor.
Until now at least two devices provided each with its own drive have been required for pumping pulp, removing the harmful gas and mixing chemicals in the pulp.
DISCLOSURE OF THE INVENTION
The primary object of the present invention is to provide an apparatus the construction of which is simple and by which gas can be removed from a high consistency pulp, chemicals can be mixed in the pulp and the pulp can be pumped.
The apparatus makes use of the advantages provided by fluidization in pumping of a pulp and in mixing chemicals in a pulp.
An apparatus according to the invention comprises a rotor provided with blades and mounted to rotate in the casing, an inlet and an outlet for the fibre suspension, and an inlet or inlets for chemicals. It is a characteristic feature of the apparatus that the rotor comprises a fluidizing and gas separating section, a pumping section and a section for mixing chemicals; and that at least one of the inlets for chemicals leads to the space between the pumping section and the mixing section or to the pumping section after the gas separating section or to the mixing section.
As removal of gas from the pulp and mixing chemicals in the pulp can be carried out as consecutive steps in the apparatus used for pumping the pulp, considerable savings are gained in investment, operation and maintenance costs and in the requirement of space when compared to known devices.
As chemicals are mixed in the pulp after gas has been removed, also gaseous and gasifiable chemicals can be mixed in the pulp with this apparatus. Expensive chemicals are thus not lost in connection with the gas removal. If chemicals are added to the pulp after pumping, e.g. gaseous chemicals do not disturb pumping.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in detail below with reference to the accompanying drawings in which
FIG. 1 is a cross section of an embodiment of the invention,
FIG. 2 is a section on line A--A in FIG. 1, and
FIG. 3 is a section on line B--B in FIG. 1.
BES
REFERENCES:
patent: 1683500 (1928-09-01), Thordarson
patent: 3290864 (1966-12-01), Harker et al.
patent: 4093506 (1978-06-01), Richter
patent: 4172668 (1979-10-01), Thompson et al.
patent: 4339206 (1982-07-01), Ahs
patent: 4410337 (1983-10-01), Gullichsen et al.
patent: 4435193 (1984-10-01), Gullichsen et al.
patent: 4671665 (1987-06-01), McIntire
PCT Publication WO81/00815.
International Technology Disclosures article entitled "Mixing Steam and/or Chemicals into a Fiber Suspension", vol. 1, No. 9, dated Jul. 25, 1983.
A. Ahlstrom Corporation
Hornsby Harvey C.
Peterson Christine A.
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