CA2360135A1

CA2360135A1 - Device for taking samples from a process flow

Info

Publication number: CA2360135A1
Application number: CA 2360135
Authority: CA
Inventors: Luis Arenas; Guillermo Droguett; Ricardo Garay; Jorge Montero; Jorge Letelier
Original assignee: Outokumpu Oyj
Current assignee: Outokumpu Oyj
Priority date: 2000-10-26
Filing date: 2001-10-25
Publication date: 2002-04-26
Also published as: FI20002349A0; FI20002349A; FI113698B; AU7829101A; CN1202424C; AU780996B2; CN1351260A; RU2279656C2

Abstract

The invention relates to a device for taking samples from a slurry process flow using the kinetic energy of the process flow in a two-stage sampler system provided with a cutter (2) positioned in the process flow (1 ) for a primary sample flow and a sampler member (5) for a secondary sample flow and a duct (3) for directing the primary sample flow towards the sampler member (5). According to the invention the duct (3) is positioned in essentially vertical position, and the duct (3) is provided with an opening (7) for leading primary sample flow back to main process flow.

Description

DEVICE FOR TAKING SAMPLES FROM A PROCESS FLOW
The invention relates to a device for taking samples from a slurry process flow using the kinetic energy of the process flow.
In many processes ,where the processed material is in the form of slurry composed of solid particles and liquid, there is a need to analyse the characteristics of the material. In a few cases it is possible to analyse slurry directly and, therefore, a representative sample is taken by a sampler and this to sample is brought to the analyser. Such an analyser is for instance an x-ray fluorescence analyser or a particle size analyser. One of the most important properties of the sampler is to take a representative sample with a flow rate suitable for the analyser in question. In practise, the flow rate is in the range of litreslmin to 1000 litreslmin. Further, the sampler has to be so constructed Is that the sampler is not blocked by slurry or trash in the flow in order to assure a reliable operation.
In large process flows a small nozzle or cutter cannot in one stage cut a representative sample because of the heterogeneity of the sample and the 2o segregation effect of the edge. The conventional solution to this problem is to take the sample in two stages. In a two-stage sampler a sample is first taken by using a large cutter and, thereafter, a secondary sample is taken from the primary sample process flow. This secondary sample has generally a flow rate suitable for an analyser. The whole sampler system contains two separate 2s samplers which are connected to each other. A problem of this two-stage sampler system is in returning the primary sample process flow back to the main process flow.
The object of the present invention is to obviate some of the drawbacks of the 3o prior art and to realise an improved device for taking a sample from large process flows in two-stage sampling system. The essential novel features of the invention are apparent from the appended claims.

In accordance with the invention the device for sampling is based on a tube or a similar profile provided with an essentially 90 degrees bend. The tube or the similar profile is positioned in the process flow to be analysed in a position s where the bend 'is a direction essentially perpendicular to the direction of the process flow. The first end of the tube or the similar profile when seeing from the direction of the process flow is provided with a sampler cutter. The second end of the tube when seeing from the direction of the process is attached to an essentially 90 degrees bend which is directed to a duct for the primary sample.
to The duct causes the primary sample flow to achieve a level essentially different from the level of the process flow. The duct is provided with a sampler member which will take a part of the primary sample flow as a secondary sample flow in order to conduct it to an analyser. The duct is also provided with an opening for leading the rest of the primary sample flow back to the main process flow. In Is order to cause the primary sample flow to achieve a level different from the level of the process flow the duct is advantageously installed in an essentially vertical position and hence the process flow to be analysed is essentially horizontal.
2o The change in the level of the primary sample flow in the duct is a result of kinetic energy of the sample process flow changing into potential energy. Some of the kinetic energy is also lost for friction. When the process flow is coming to the cutter it has kinetic energy because of the flow. When the primary sample flow reaches the essentially vertical wall of the duct it is obliged to change the 2s direction and to rise to a higher level than the process flow. This requires potential energy that is taken from the kinetic energy and thus the flow velocity is reduced. The change in the direction will cause turbulence as well as friction in the primary sample flow. Friction will further decrease the kinetic energy of the primary sample flow.
The sampler member in the device of the invention for taking secondary sample process flow is installed in the duct so that an opening in the sampler member for the sample flow is positioned between the opening formed in the wall of the duct for returning the primary sample flow back to the original process flow and the bend of the tube.
s The invention is explained in more detail with reference to the appended drawing, which is a side-view illustration of a preferred embodiment of the invention.
In accordance with the drawing, slurry process flow to be analysed flows to the to direction illustrated by an arrow 1. A cutter 2 for taking a sample from the slurry process flow is installed in the flow 1. The cutter 2 is attached to a duct 3 v~rhich is placed in an essentially vertical position essentially perpendicular to the flow 1. In a wail of the duct 3 an opening 7 has been formed. In order to take a sample for an analyser the duct 3 is provided with a sampler 5 which is placed is at least partly inside the duct 3. A sieve 4 is installed in front of the sampler 5 in order to prevent the blocking of the sampler 5 of harmful impurities from the process flow. The sampler 5 is further connected to a tube 6 in order to conduct the sample to the analyser:
2o When the device of the invention is operated, the cutter 2 cuts a part of slurry process flow and that part, primary sample flow, flows in the cutter 2 until the flow reaches the wall of the duct 3. Because the sample is lifted to a higher level and because of friction, the flow velocity of the sample is reduced.
This means that part of kinetic energy of the flow is changed into potential energy 2s and some is lost to friction. This change in energy causes a change in the flow level of the primary sample flow inside the duct 3.
The sampler 5 is placed in a position where there is always a sample to be taken. Depending on the velocity of the flow the height of the sampler 5 intake 3o is at the flow level of the process flow just above the bend between the cutter 2 and the duct 3. When the primary sample flow reaches the sampler 5, the sampler 5 takes a secondary sample flow from the primary sample flow. The rest of the primary sample flow is returned through the opening 7 of the duct back to the main process flow 1. The secondary sample flow 6 in the sampler 5 is fed to an analyser.

Claims

1. Device for taking samples from a slurry process flow using the kinetic energy of the process flow in a two-stage sampler system provided with a cutter (2) positioned in the process flow (1) for a primary sample flow and a sampler member (5) for a secondary sample flow and a duct (3) for directing the primary sample flow towards the sampler member (5), characterised in that the duct (3) is positioned in essentially vertical position, and the duct (3) is provided with an opening (7) for leading primary sample flow back to main process flow.

2. Device according to claim 1, characterised in that the inlet of the sampler member (5) is placed in the duct (3).

3. Device according to claims 1 or 2, characterised in that a sieve (4) is installed in front of the secondary sampler (5).

4. Device according to claims 1, 2 or 3, characterised in that the secondary sampler member (5) for the sample flow is positioned between the opening (7) formed in the wall of the duct (3) for returning the sample process flow back to the original process flow and the bend of the duct (3).

5. Device according to any of preceding claims, characterised in that part of the duct (3) is outside the process flow and is provided with a return (7) to the process flow.