ABSORBENT IN PULP PROCESS

AGENT D'ABSORPTION POUR LE TRAITEMENT DE LA PATE

English Abstract

ABSTRACT

In a carbon in pulp process carbon granules and pulp are transferred
between vessels and out of the system by means of a vacuum lift system.
The vessels are formed with sumps recessed into their tops from which
pulp flows. Screens pivoted in the bases of the sumps keep the carbon
granules in the vessels.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-


1.
An absorbent in pulp process in which absorbent granules are passed in
countercurrent to a pulp through a series of vessels in which the
granules and pulp mixture is agitated, loaded granules are removed from
the first vessel in the series and barren pulp flows from the last
vessel, the granules being held back in each vessel by a screen, and in
which granules and pulp are transferred from one vessel to a preceding
vessel and out of the system by means of a vacuum lift system.

2.
The process claimed in claim 1 in which granules are separated from the
pulp in a sump recessed into the top of a vessel, the floor of the sump
being formed by a horizontal screen and the outflow from the sump going
to the next vessel.

3.
The process claimed in claim 2 in which the screen is pivoted in the base
of the sump so that it can be lifted into a vertical position for
cleaning purposes.

4.
The process claimed in claim 1 in which the absorbent granules are carbon
granules.

5.
The process claimed in the claim 4 in which the pulp is a gold ore and
cyanide solution pulp.




6.
Apparatus for treating a pulp with absorbent granules comprising a series
of vessels, means for agitating the contents of the vessels, connections
between vessels allowing pulp to flow from a first vessel through the
series to the last vessel and out of the last vessel, a screen in each
vessel holding back the granules, and a vacuum lift system for
transferring granules and pulp from the last vessel to the preceding
vessel, through the series to the first vessel and out of the first
vessel.

7.
The apparatus claimed in claim 6 in which each vessel has a sump recessed
into its top, the floor of the sump being formed by a horizontal screen
and the connection leading from the sump.

8.
The apparatus claimed in claim 7 in which the screen is pivoted in the
base of the sump so that it can be lifted into a vertical position for
cleaning purposes.

Description

BACKGROUND TG THE INVENTION

This invention relates to an absorbent in pulp process.

In one process of the kind in question carbon granules are passed in
countercurrent to a pulp through a series of vessels in which the carbon
S and pulp mixture is agitated. Loaded carbon is removed from the first
vessel in the series and barren pulp flows from the last vessel.

The usual way of transferring carbon ;s to transfer a quantum of carbon
and pulp by means of an air lift pump. This causes problems because
important parts are immersed in the pulp and prone to attrition. Also
10 air accelerates calcium scaling on the carbon granules.
.
Another way of achieving it is to pump the carbon and pulp mixture on to
a screen which holds back the carbon and allows the pulp to flow to the
next vessel. Carbon caught on the screen is transferred to the previous
vessel. The power and maintenance costs for this system is high.

15 Where external screen transfer of carbon is not practised it is usual to
have vertical screens inside the vessels to hold back the carbon from the
pulp flowing to the next vessel. In order to clean a screen its vessel
has to be taken off-line. This is obviously a drawback.

5~
--3-

In another process of the kind in question resin beads or granules are
passed in countercurrent to a pulp through a series of vessels in the
same way as discussed above. The resin gets loadecl with gold or aranium
complex. Much the same problems are encountered in this case.

5 In this specification the term "absorbent" is interlded to mean a
substance such as activated carbon, a resin or the like which absorbs or
adsorbs substances from a solution.

SUMMARY OF THE INVENTION

In an absorbent in pulp process according to the invention absorbent
10 granules are passed in countercurrent to a pulp through a series of
vessels in which the granules and pulp mixture is agitated, loaded
granules are removed from the first vessel in the series and barren pulp
flows from the last vessel, the granules being held back in each vessel
by a screen, and in which granules and pulp are transferred from one
15 vessel to a preceding vessel and out of the system by means of a vacuum
lift system.

Apparatus according to the invention comprises a series of vessels, means
for agitating the contents of the vessels, connections between vessels
allowing pulp to flow from a first vessel through the series to the last
20 vessel and out of the last vessel, a screen in each vessel holding back
the granules, and a vacuum lift system for transferring granules and pulp
from the last vessel to the preceding vessel, through the series to the
first vessel and out of the first vessel.

DESCRIPTION OF THE DRAWINGS
. _

25 Figure 1 is a plan view o~ a few adsorption tanks,
Figure 2 is a section on the line 2-2 in Figure 1, and
Figure 3 is a diagrammatic view of a carbon granule transfer system.

DESCRIPTION OF AN EMBODIMENT
,,
The illustrated embodiment is used to recover gold from ore and cyanide
30 solution pulps by means of granules of activated carbon.

~%~
--4--

Figure 1 shows four tanks S, 6, 7 and 8 arranged for pulp to flow in that
order from tank to tank and onwardly. Let into the top of each tank is a
sump 10 with a screen 11 in its base.

As can be seen from Figure 2 the screen 11 is pivoted around a pivot axis
5 12 to be able to move to the vertical chain line position 13 shown in
Figure 2 for cleaning purposes.

Pulp from the surnp 10 flows into a channel 14 over the edge 15 so that
the screen 11 is always submerged in pulp in accordance with the flow
rate desired. Below the screen 11 there is an adjustable baffle 16 for
10 causing a stillwell immediately below the screen 11.

The system of carbon transfer is shown in Figure 3. In this view the
sumps 10 are not shown and it is largely diagrammatic. Attached to each
of the tanks 5 to 8 there is a container 20 from which a leg 21 projects
into the tank. The container 20 has two valves 22 and 23 which may be
15 opened and closed, but not for them to be in the same state at any given
time. When a valve 23 is closed and its counterpar~ 22 is open the
container 20 is connected to a vacuum line 2~. The valve 22 is closed
when pulp and carbon coming up the leg 21 fills the container to the
level marked High Level in Figure 3. Then the valve 23 is opened for the
20 contents of the container to discharge through the valve 23 into the
preceding tank or out of the system. The valve 23 is held open until the
level marked Low Level in the drawing is reached which initiates a new
cycle.

In the result during each cycle the same volume of pulp is transferred
25 via the container 20.

Air does not come into contact with the carbon and working parts are all
situated above the level o~ the pulp.



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