DD259800A1 - METHOD FOR CONTINUOUS MEASUREMENT OF THE DISPERSITIVE CONDITION OF DISPERSER SOLIDS SYSTEMS - Google Patents

Abstract

Method for the continuous measurement of the state of dispersity of dispersed solid systems for use in the monitoring and / or control of production processes. The object is achieved according to the invention in that the loaded gas is at least two series-connected devices for current classification with known Abscheidecharakteristiken and continuously operating Feststoffaustragsorganen before, between and behind which is ever a Meßfuehler whose measured values by the concentration and by the average grain size of disperse solids system are influenced in a known manner, and that the measured values are processed in a process computer for the simultaneous determination of the grain size distribution and the concentration of the particulate solids system according to a suitable algorithm.

Description

with i = 1, 2, ..., n + 1 and ^ ⁰ ) «0 ·. -

at the same time the m parameters of the distribution function h ₃ ⁽¹⁾ (x), where m <n, and the concentration c ^{(1) of} the disperse solid system are determined in the measuring line.

2. The method according to item 1, characterized in that for the calibration of the probe (5, 6,7,3), the determination of the constant k ⁽ⁱ⁾ before the first operation measurement by evaluating at least one calibration test, which while maintaining the usual measuring measurements for operating measurements , but with one of the last unit for stream classification additionally downstream absolute filter and weighing the deposited in the individual units for stream classification and in the absolute filter over a certain period of solids amount is performed.

3. The method according to item 1 and 2, characterized in that the sensors (5,6,7,8) before, between and behind the units for stream classification are preferably carried out as triboelectric and optical optical probe, the corresponding measuring methods both separately and combined can be used.

For this 1 page drawing application of the invention

The invention relates to a method for the continuous measurement of the dispersity state of disperse solid styrene - in particular the particle size distribution - and the dust concentration for the application for monitoring and / or control of production processes in which the product quality or the effectiveness of technical facilities by the particle size distribution and / or by the solids concentration in flowing gases is determined, such as in the chemical industry, in the building materials industry, in metallurgy, in the food and beverage industry, in the brewing and malting industry and in the textile industry.

Characteristic of the known technical solutions

To characterize the dispersity state and the solids concentration, processes are usually used which realize a proportionate mass distribution to the individual particle size classes and / or determine the integral mass concentration. If both solids concentration and particle size distribution of disperse solid systems are to be determined, this is often done by gravimetric sampling in a gas or gas stream and subsequent granulometric analysis of the Haufwerksproben.

Other measuring techniques such as cascade impactors (SU-PS 479995) allow a combined in situ determination of solids concentration and particle size distribution.

A disadvantage is the discontinuous mode of operation of such methods and the considerable amount of time involved in the gravimetric determination of the separated particle masses.

For on-line determination of the in-situ particle size distribution of disperse solid systems optical counting methods are often used. These require a rather high expenditure on equipment for carrying out and evaluating the measurements and, because of their complexity, are not suitable for universal use, for example under harsh operating conditions.

Various methods are known in which the disperse solids system is separated into certain particle size fractions with the aid of devices for stream classification.

In the process described in US-PS 371 9089 method, the particle size distribution of a dispersed in a flowing medium solid is determined by the ode to the accumulation of a certain mass of a certain volume r

at least one grain size fraction of the solid to be examined in a collecting container time is measured over a series of time intervals. However, this process is quasi-continuous and is therefore only partially suitable for process monitoring or process control.

A measuring system is known for the continuous measurement of the change in the particle size distribution of disperse solids, in which the grain size dependence of the triboelectric effect is utilized (DE-OS 2854657). Measurement errors due to changes in the solids concentration are hereby eliminated by comparing the measured values of a plurality of triboelectric probes which are upstream, downstream and / or intermediate of one or more units for selective grain size differentiation and / or separation. In this method, however, only qualitative statements about the change in the particle size distribution can be made. The determination of the actual particle size distribution as well as the concentration of the dispersed solids system in the flowing gas are not possible.

Object of the invention

The aim of the invention is to enable a continuous measurement of the dispersity state of disperse solid systems, primarily for operational measurements under practical conditions for monitoring and / or optimal control of production processes. ,

Explanation of the essence of the invention

The object of the invention is to ensure continuous measurement of the particle size distribution and of the concentration of solid systems dispersed in flowing gases using measurement techniques that can be used under practical conditions. If the solids in question are not in dispersed form, they are appropriately dispersed by conventional means.

The object is achieved in that the disperse solids system by at least two series-connected devices for current classification with known Abscheidecharakteristiken and with continuous devices for dust removal before, between and behind which is ever a sensor whose measured values by the solids concentration and by the mean grain size the continuously dispersed measured values of the sensors are processed in a process computer for determining the particle size distribution and concentration of the disperse solid system in the flowing gas according to a suitable calculation algorithm of the disperse solid system in a known manner. ...

The stream classification units have known fractional separation curves previously determined by calibration studies and are equipped with continuous discharge means for the solid collected during the measurements so that periodic interruptions of the measurements for emptying solids collection containers are unnecessary.

Before the first, behind the last and between the units for current classification is ever a sensor. The sensors used are those devices which, based on certain physical principles of action, provide measured values which correspond to the total surface area A _{p of} all particles detected by the sensor in a specific, differentially small period of time or according to the principle of measurement at a particular point in time in a known functional relationship stand. , ^ ._ '

^x tnax With A ^ a / -HE. c * vJ x ~ ¹ . c h. (x) dx

can this functional relationship for the sensor at the measuring point i in the following general form:

^x tnax.

_v (i). -, "(i) _h Ci -) / _ s _ (i) Γ -1 _Λ (ί) _h (i) f. ^ A ~ \ u / 1 = r (M j π ™ (xj jc _Q , ι χ c ru (, α; αχ;

P Λ / A ν A

where i · = 1, 2, ..., n + 'l

M ^{01 are} the measured values at the measuring point i, h ₃ ⁽ⁱ⁾ the mass-related particle size distributions at the measuring point i, x _min and x _max the minimum or maximum grain size of the distribution, c ^(il the solids concentrations at the measuring point i, η the number the units to the power classification, A _op / v is the volume-based particle surface. the values of M ₀ ⁽ⁱ⁾ h ₃₀ ^(il and c ₀ ⁽ⁱ⁾ denote the measured values, the grain size distributions and the solids concentration at the measuring points i under calibration conditions. This value Constants are and prior to the first operation measurement in evaluation of at least one calibration test, which while maintaining the methodology described above, but with one of the last unit for stream classification additionally downstream absolute filter and under weighing the individual units for stream classification and absolute filter over a period of time deposited masses of the dispersed solids system s is performed. From the deposited solid matter and the well-known '.

Fractional separation efficiency curves of the flow classification units can be determined similarly to the procedure for evaluating measurements with multi-cycle equipment.

The above-mentioned non-linear equation system can then be simplified

= f (k⁽ⁱ⁾ ₅ f ϊ ± -. h ₃ ^ hx)dx)

where k ⁽ⁱ⁾ includes the values denoted M ₀ (i), H ₃₀ " ¹ and c _o ^w under calibration conditions, with the definition of the fractional efficiencies T ^(l) according to

T ^U} (x) = 1 - ° _TTT ~. ^ 3 ^UJ

then follows

^x max ^ ₁

J X

= f / k ⁽ⁱ⁾ , f £ ~ i TT Pl - T ⁽ ^ (x) |. h ₃ ⁽ⁱ ^ (x) dx

i. = 1, 2, ..., nf 1

with T ^(o) = 0, which is a n-order nonlinear system of equations (n + 1) with m + 1 independent variables, where m denotes the number of distribution parameters of the desired particle size distribution h ₃ ^l1l (x).

In the case m = η, this equation system is uniquely solvable for each m-parameter distribution function by suitable iterative methods. If, on the other hand, the number of units for stream classification is chosen to be larger (n> m), then it is possible to select the most favorable distribution function from a series of predetermined m-parameter distribution functions by the application of known nonlinear optimization methods and, moreover, to provide information about the analysis errors that occur to meet. The solution of the above equation system is carried out by means of a coupled via transducer process computer. The particle size distribution and concentration of the dispersed solids system are available as output variables of the process computer for process monitoring and further processing in the devices for process control.

embodiment

1 shows an embodiment of the method according to the invention is shown, which will be described in more detail below.

According to FIG. 1, three small-cell clones 1-3 connected in series with flow-reducing sizes and known fractional separation efficiency curves T ¹¹¹ , T ¹²¹ and T ⁽³ ') serve as units for stream classification.

The Feststoffaüstragsorgane be formed by rotary valves 4. The sensor used are four friction or light-optical sensor 5-8, which are arranged in the flow channels before the first Kleinzyklon 1, between the first Kleinzyklon 1 and second Kleinzyklon 2, between the second Kleinzyklon 2 and the third Kleinzyklon 3 and behind the third Kleinzyklon 3.

The currents I removed at the sensors 5-8 are proportional to the total surface area of the particulate solid system, which contacts the triboelectric probes 5-8 in a different small time interval, or, when using photometric probes 5-8, proportional to that resulting from the particulate solid state system Light attenuation .and are as follows:

max I = k. / - h- (x) dx with

_k .

^ max

- · ♦ 1ι _ΟΛ (χ) - dx

wherein the constant k and the corresponding current I _{0 are determined} in at least one calibration test for the relevant substance system.

This results in the equation system:

^x max / _Λ ν. (1) _ f ^ ^r ~ ^nj

¹⁾ . J

Qi a .χ

ni-in

χ max

[iT ⁽²⁾ ( _X )]. fi-T ^C3) (.-o] .b3 ⁽¹⁾ (x) clx

If one chooses two parametric distribution functions as h ₃ ⁽¹⁾ (x), the two parameters of the distributions as well as c ^{| 1> are} to be determined as independent variables from the system of equations. This is done iteratively, using known multi-parameter, nonlinear optimization methods.

Claims (1)

1. A method for the continuous measurement of the dispersity state of disperse solid systems, wherein the loaded gas by at least two series-connected units for stream classification, before, between and behind which is a sensor whose Meßwerte d.urch the solids concentration and by the mean grain size of im Measuring channel located disperse solids system are influenced in a known manner, characterized in that in a directly coupled process computer (9) from the known Fraktionsabscheidegradkurven T ⁽ⁱ⁾ (x) of the η units for current classification and from the measured values M ^(l) of calibrated η + 1 sensor (5, 6, 7, 8) and the constants k ^(l) determined from calibration tests by solving the system of equations · * ·, - ^X aiax _t ^