METHOD AND SYSTEM FOR SAMPLING IN A MATERIAL MIXTURE

Abstract: A method and a system for continuous sampling for the analysis of a material mixture. A small portion of the material mixture is tapped from a space (1) through a sample tapping point (2), which is connected to a pipe coil (3). This pipe coil (3) comprises a pump (5) and a feed pipe (6) for controlled supply of dilution liquid for dilution to desired concentration. The pipe coil (3) opens (4) at the sample tapping point (2), and an adjustable portion of the flow in the coil is recycled to the space (1). Analysis equipment (9) is intended to be connected to the pipe coil (3).

Description: Method and system for sampling in a material mixture This invention relates to a method and system for continuous sampl¬ ing for analyzing material mixtures. Examples of such material mixt¬ ures are particles in liquid such as fiber suspensions of the type of papermaking pulp. The invention, however, can be applied also to other mixtures of particles, liquids and gases. The sampling can be carried out from a space, for example a conveying pipe or a tank for the material mixture. At the analysis of properties of papermaking pulp it is normally of great importance for obtaining accurate measuring results, that the concentration is constant and known. Examples of properties to be an¬ alyzed are the content of different kinds of impurities, shives cont¬ ent, dewatering capacity (freeness) / fiber appearance and properties. Certain methods of analysis require very low concentrations compared with the pulp concentration in the process. One example thereof is image analysis of fiber properties where the dilution demand can be 1:1000 or higher. At continuous sampling this has implied very long conveying times and, thereby, delayed measuring results or a large consumption of clean dilution water. One method of successfully dealing with these problems would be to reduce the pipe diameter in the sampling equip¬ ment. This possibility, however, is restricted by the risk of plugg¬ ing, especially when both the concentration and the dilution demand are high at the same time. More problems arise due to the fact, that the sample taken, besides being diluted, also must be mixed to a uniform concentration, before it can be analyzed. The present invention offers a solution for the aforesaid problems. According to the invention, a portion of the material mixture is directed in a continuous flow into a pipe coil while simulaneously being diluted to desired concentration for analysis, and at the same time an adjustable portion of this flow is recycled to the material mixture. The partial recirculation in the coil yields a high dilution factor at a small dilution liquid flow, at the same time as the flow in the coil can be high and, thereby, causes a short delay in conveying. The plugging risk is small, because the concentration in the entire coil is low, and the net flow runs from the coil into the material mixture. The characterizing features of the invention are apparent from the attached claims. The invention is described in greater detail in the following, with reference to an embodiment thereof illustrated in the accompanying Figure. A material mixture, for example a pulp suspension, in a process pipe is to be analyzed. A sample tapping point 2 communicating with the pipe 1 for diverting a portion of the pulp is connected to the pipe. This tapping point 2 preferably is formed as a short pipe extending some distance into the pipe 1 , so that the sample shall be represent¬ ative, and corner effects at the analysis shall be avoided. The tapp¬ ing point 2 is connected to a pipe coil 3, the other end of which opens 4 at the tapping point 2. The pipe coil 3 comprises a pump 5 for circulating the sample taken in the coil. A feed pipe 6 for dil¬ ution liquid is connected to the pipe coil 3. A valve 7 controls the dilution liquid supply so as to vary and control the concentration in the coil which is measured continuously. The pump 5 can be, for example, a simple centrifugal pump, which sucks in a portion of the pulp from the pipe 1 and causes it to circ¬ ulate and be mixed to uniform concentration in the pipe coil 3. The flow in the pipe coil 3, thus, is determined by the pump 5, but can also be controlled by means of a valve 8 in the pipe coil. The mouth 4 of the pipe coil 3 at the sample tapping point 2 prefer¬ ably is adjustable for determining the reflux to the pipe 1. Depend¬ ing on the configuration and location of the sample tapping point 2 and mouth 4 in relation to each other, the yield, i.e. the tapped pulp and its recirculation can vary from no yield at all, i.e. merely recirculation in the pipe coil, to complete yield, i.e. no recircul¬ ation in the pipe coil. The degree of yield, i.e. the amount of new pulp supplied to the pipe coil, can also be controlled by the flow rate in the coil. It is possible to calculate the yield degree, as it is in direct rel¬ ation to the concentration in the coil and the dilution liquid flow, when the system is in balance. At the embodiment shown, the mouth 4 of the pipe coil is vertically adjustable. It extends upward in the sample tapping point 4 and is located immediately below the opening of the sample tapping point in the pipe 1. Alternatively, the adjustable mouth 4 can be directed down¬ ward from above to the sample tapping point 2 and can be raised or lowered or be laterally movable above the edge of the sample tapping point 2. The mouth also can be directed obliquely in relation to the sample tapping point 2. Owing to the adjustability of the mouth 4 in relation to the sample tapping point 2, as described above, the yield, i.e. the amount of new material mixture supplied to the pipe coil 3,can be adjusted. The analysis of the material mixture can be carried out anywhere in the pipe coil, but preferably takes place immediately after the pump. The analysis equipment 9 can be of a type known per se for measuring different properties of the material mixture. The properties of a pulp suspension are analyzed with different meters at different con-r centrations. The impurities content, for example, can be measured at a pulp concentration of about 1%, the freeness at about 0,3%, the shives content at about 0,01% and the fiber appearance at about 0,0005%. As it is desired to carry out the measurings approximately simultaneously, it is necessary £o change the concentration in the pipe coil rapidly, which is possible with the controls and adjustments described above. For analyses to be carried out batchwise, for example the freeness measuring of a pulp suspension, a portion of the content in the coil is diverted into an analyzer and locked in for analysis. The sample is then recycled to the material mixture or discharged. When the sample tapping point 2 is connected to a sampling tank in¬ stead of to a pipe, analyses which cannot be made directly in a flow of the material mixture are made batchwise, for example samples supplied batchwise to a sampling tank of a pulp suspension. The sampling equipment according to the invention also can be con¬ trolled and utilized for control and calibration of the analyzers by connecting the sample tapping point to a vessel containing a mat¬ erial mixture with known properties. Owing to the fact that the sampling system according to the invention renders it possible to adjust the desired concentration for analysis very rapidly, the length of the pipe coil is not critical, but the place of analysis can be located at a distance from the sample tapp¬ ing point when this is preferred in view of local conditions. The invention, of course, is not restricted to the ebodiments ment¬ ioned above, but can be varied within the scope of the invention idea.

Claims: Claims 1. A method of continuous sampling for the analysis of a material mixture where a small portion of the material mixture is tapped, c h a r a c t e r i z e d i n that the tapped portion is dir¬ ected in a continuous flow in a pipe coil, in which dilution with dilution liquid to desired concentration takes place for analysis, and that an adjustable portion of the flow in the coil is recycled to the main portion of the material mixture at the sample tapping point. 2. A method as defined in claim 1, c h a r a c t e r i z e d i n that the tapping and recycling of the material mixture, i.e. the yield between the main portion of the material mixture and the flow in the pipe coil, are adjustable. 3. A method as defined in claim 1 or 2, c h a r a c t e r i z e d i n that the concentration of the flow in the pipe coil is measur¬ ed continuously and utilized for controlling the dilution liquid supply and the yield. 4. A system for continuous sampling for the analysis of a material mixture, comprising a sample tapping point (2)communicating with a space (1.) for the. material mixture, c h a r a c t e r i z e d i n that the sample tapping point (2) is connected to a pipe coil (3) com¬ prising a pump (5) and feed pipe (6) for controlled supply of dilut¬ ion liquid, that the pipe coil (3) opens (4) at the sample tapping point (2) , and that an analyzing equipment (9) is intended to be connected to the pipe coil (3) . 5. A system as defined in claim 4, c h a r a c t e r i z e d i n that the mouth (4) of the pipe coil (3) is adjustable in relation to the sample tapping point (2) . 6. A system as defined in claim 4 or 5, c h a r a c t e r i z e d i n that the mouth (4) of the pipe coil is arranged movable in the sample tapping point (2) . 7. A system as defined in any one of the claims 4-6, c h a r a c t¬ e r i z e d i n that the pipe coil (3) comprises a valve (8) for controlling the flow in the coil.

Inventors: SUNDH GOERAN, SUNDH, GOERAN
Applicants: SUNDH GOERAN, SUNDS DEFIBRATOR IND AB, SUNDH, GOERAN, SUNDS DEFIBRATOR INDUSTRIES AB
Application year: 1995
Main classification: G01N1
IPC codes: G01N1, G01N33