EP2754500B1 - Method for jet milling and jet mill for the same - Google Patents

Description

The present invention relates to a method for jet grinding according to the preamble of claim 1 and a jet mill therefor according to the preamble of claim 5.

In many processes, a product to be ground is obtained in a pre-process (precipitation, flotation, washing) in a wet suspension. If the ground end product is to be dry, the desired residual moisture must be set in a complex process, for example by mechanical pre-drainage, e.g. in filter presses, and then thermal drying. The grinding to the required final fineness often takes place in jet mills. Typical applications are e.g. the production of talc, silica, magnesium hydroxide or ceramic ink-jet pigments.

Disadvantages here are the overall expenditure in terms of equipment and time in order to ultimately obtain a product to be ground from a wet suspension with the desired residual moisture and final fineness.

It is the aim of the present invention to simplify the previous method and make it cheaper.

JPH0824702A discloses a method for jet grinding and a jet mill according to the preamble of claim 1 and claim 5.

This object is achieved with a method for jet grinding according to claim 1 and a jet mill according to claim 5.

According to the invention, it is therefore provided that grinding and drying are carried out in a common process step. This means that the entire process can be carried out much more easily and with less energy.

In the method according to the invention for the jet grinding of moist or wet grinding stock in a jet mill, moist or wet grinding stock is fed to the jet mill for grinding. At least one operating parameter, inlet pressure, expansion pressure and inlet temperature in the jet mill is selected in such a way that grinding-drying takes place. To obtain an end product with a specified final fineness and specified residual moisture content, the moist or wet ground material is simultaneously ground in the jet mill to the specified final fineness by grinding and dried to the specified residual moisture content. In this case, through a suitable selection of the at least one operating parameter inlet pressure, expansion pressure and inlet temperature, the specific operating resource requirement for grinding is selected so that it is greater than or equal to the specific operating resource requirement for drying. Finally, the end product with the specified final fineness and the specified residual moisture is discharged from the jet mill.

It can also preferably be provided that the actual residual moisture of the ground material is measured or monitored before it is discharged from the jet mill or the actual residual moisture of the end product. According to a preferred development of this, it can additionally be provided that the at least one operating parameter of the jet mill is performed once or repeatedly over time Intervals or at least approximately continuously for the mill drying depending on the one hand the actual residual moisture of the ground material before it is discharged from the jet mill or the actual residual moisture of the end product and on the other hand the predetermined residual moisture of the end product is suitably set, controlled or regulated.

In a further preferred embodiment of the method according to the invention, gases or superheated vapors are used as operating media.

• zur Einstellung, Steuerung oder Regelung wenigstens eines der Betriebsparameter Vordruck, Entspannungsdruck und Eintrittstemperatur bei der Strahlmühle Einstellungs-, Steuerungs- oder Regelungseinrichtungen vorgesehen sind, mittels denen der wenigstens eine Betriebsparameter Vordruck, Entspannungsdruck und Eintrittstemperatur bei der Strahlmühle geeignet so gewählt wird, dass eine Mahltrocknung erfolgt, bei der das feuchte oder nasse Mahlgut zum Erhalten eines Endproduktes mit vorgegebener Endfeinheit und vorgegebener Restfeuchte gleichzeitig in der Strahlmühle durch die Mahlung auf die vorgegebene Endfeinheit gemahlen und durch die Trocknung auf die vorgegebene Restfeuchte getrocknet wird,
• die Einstellungs-, Steuerungs- oder Regelungseinrichtungen so ausgestaltet sind, dass durch geeignete Wahl des wenigstens einen Betriebsparameters vordruck, Entspannungsdruck und Eintrittstemperatur der spezifische Betriebsmittelbedarf der Mahlung so gewählt wird, dass dieser größer oder gleich dem spezifischen Betriebsmittelbedarf der Trocknung ist, und
• der Endproduktauslass der Strahlmühle so ausgelegt ist, dass das Endprodukt mit der vorgegebenen Endfeinheit und der vorgegebenen Restfeuchte durch den Endproduktauslass aus der Strahlmühle ausgeleitet wird.

The invention also provides a jet mill for jet grinding moist or wet grist to an end product, wherein

• To set, control or regulate at least one of the operating parameters pre-pressure, expansion pressure and inlet temperature in the jet mill, setting, control or regulation devices are provided, by means of which the at least one operating parameter pre-pressure, relief pressure and inlet temperature in the jet mill is suitably selected so that grinding drying takes place, in which the moist or wet ground material to obtain an end product with a specified final fineness and specified residual moisture is simultaneously ground in the jet mill by grinding to the specified final fineness and dried by drying to the specified residual moisture,
• the setting, control or regulating devices are designed in such a way that, through a suitable selection of the at least one operating parameter pre-pressure, expansion pressure and inlet temperature, the specific operating resource requirement for grinding is selected so that it is greater than or equal to the specific operating resource requirement for drying, and
• the end product outlet of the jet mill is designed in such a way that the end product with the specified final fineness and the specified residual moisture is discharged from the jet mill through the end product outlet.

Residual moisture detection or monitoring devices are preferably assigned to the end product outlet of the jet mill to determine or monitor the actual residual moisture of the ground material before it is discharged from the jet mill or the actual residual moisture of the end product obtained by grinding and drying the ground material in the jet mill.

It can also be provided with preference that the setting, control or regulation devices are designed in such a way that, through a suitable selection of the operating parameter (s) pre-pressure, expansion pressure and / or inlet temperature, the specific operating resource requirement of the grinding is selected in such a way that this is greater than or equal to the specific operating resources required for drying. It can further preferably be provided that the setting, control or regulating devices are designed so that the at least one operating parameter pre-pressure, expansion pressure and inlet temperature of the jet mill once or repeatedly at time intervals or at least approximately continuously for the grinding drying depending on the one hand on the actual residual moisture of the ground material before it is discharged from the jet mill or the actual residual moisture of the end product and on the other hand the predetermined residual moisture of the end product is suitably set, controlled or regulated.

Another preferred embodiment is that gases or superheated vapors are used as operating media. Preferred and / or advantageous embodiments of the invention and its individual aspects emerge from the dependent claims and their combinations as well as from all of the present application documents.

Fig. 1

in einer schematischen Schnittansicht ein Ausführungsbeispiel einer Fließbettstrahlmühle veranschaulicht ist,

Fig. 2

in einer graphischen Darstellung den spezifischen Betriebsmittelbedarf in Abhängigkeit von der erzielten Mahlfeinheit für einen Betriebsmitteldruck von 8 bar(abs) und 4 bar(abs) mit Talkum als Mahlgut zeigt, und

Fig. 3

in einer graphischen Darstellung die spezifische Trocknungsleistung in Abhängigkeit vom spezifischen Betriebsmittelbedarf (hier: Wasserdampf) zeigt.

The invention is explained in more detail below using exemplary embodiments with reference to the drawing, in which

Fig. 1

an exemplary embodiment of a fluidized bed jet mill is illustrated in a schematic sectional view,

Fig. 2

shows in a graphical representation the specific resource requirement as a function of the grind fineness achieved for an operating pressure of 8 bar (abs) and 4 bar (abs) with talc as the ground material, and

Fig. 3

shows in a graphic representation the specific drying performance as a function of the specific resource requirements (here: water vapor).

The invention is explained in more detail using the exemplary embodiments and application examples described below and shown in the drawings, i.e. it is not limited to these exemplary embodiments and application examples. Process and device features also result in an analogous manner from device and process descriptions.

Individual features that are specified and / or shown in connection with a specific exemplary embodiment are not related to this exemplary embodiment or the combination with the others Features of this exemplary embodiment are limited, but can be combined with any other variants within the framework of what is technically possible, even if they are not dealt with separately in the present documents.

Identical reference symbols in the individual figures and illustrations of the drawing denote identical or similar components or components that have the same or similar effect. On the basis of the representations in the drawing, those features that are not provided with reference numerals also become clear, regardless of whether such features are described below or not. On the other hand, features that are contained in the present description but are not visible or illustrated in the drawing can also be readily understood by a person skilled in the art.

In the Fig. 1 a fluidized bed jet mill 10 is shown by way of example as an exemplary embodiment for a jet mill 1 in general. A few essential and common components of the fluidized bed jet mill 10 are designated for orientation purposes only: feed connection 2 for moist or wet grinding stock (not shown), grinding chamber 3, grinding gas nozzles 4, classifying wheel 5, motor 6 and end product outlet 7.

The grist is fed to the fluidized bed jet mill 10 via the feed connection 2 above the grinding gas nozzles 4. The gas jets emerging from the grinding gas nozzles 4, preferably gases or overheated vapors, form a material fluidized bed (not shown) in the grinding chamber 3, from which the grinding material enters the gas jets, where it (more precisely, the particles contained therein) accelerates to high speeds will. The accelerated particles meet in the gas jets and in the center of the grinding chamber and are crushed in the process. Relaxed grinding gas loaded with particles of different sizes rises in the center of the grinding chamber 3 to the classifier wheel 5, which is driven by the continuously variable speed motor 6. The particles which correspond to the set conditions reach the end product outlet 7. Too coarse / large / heavy particles are rejected by the classifying wheel 5 and fall back into the fluidized bed.

The end product outlet 7 is assigned residual moisture detection or monitoring devices 8 for determining or monitoring the actual residual moisture of the ground material before it is discharged from the jet mill or the actual residual moisture of the end product obtained by grinding and drying the ground material in the jet mill.

Setting, control or regulating devices 9 are provided for setting, controlling or regulating at least one operating parameter of the fluidized bed jet mill 10. By means of the setting, control or regulation devices 9, the at least one operating parameter of the fluidized bed jet mill 10 can be suitably selected such that grinding drying takes place. In the present documents and in the present invention, grinding drying is a process in which the moist or wet ground material to obtain an end product with a specified final fineness and specified residual moisture is simultaneously in the jet mill, such as the fluidized bed jet mill 10, by grinding to the specified The final fineness is ground and dried to the specified residual moisture.

As the at least one operating parameter which can be set, controlled or regulated by means of the setting, control or regulating devices 9, in particular the admission pressure, the expansion pressure or the inlet temperature is provided. The setting, control or regulating devices are preferred 9 designed in such a way that, through a suitable choice of the operating parameter (s) pre-pressure, expansion pressure and / or inlet temperature, the specific operating resource requirement for grinding is selected so that it is greater than or equal to the specific operating resource requirement for drying.

The end product outlet 7 of the fluidized bed jet mill 10 is designed in such a way that the end product with the specified final fineness and the specified residual moisture is discharged from the fluidized bed jet mill 10 through the end product outlet 7.

Further details of the invention are explained in more detail below.

Grinding and drying are actually two separate procedural operations.

The grinding is characterized by the adiabatic energy input. The adiabatic energy describes the energy that is released in the form of kinetic energy during adiabatic expansion of pressurized gases or vapors.

mit

κ =

Isentropenexponent

m =

Gasmasse

R =

Gaskonstante

T0 =

Gaseintrittstemperatur

p1 =

Entspannungsdruck

p0 =

Gasdruck vor Entspannung

berechnen.It can be calculated for ideal gases according to the equation $${\mathrm{E.}}_{\mathit{ad}}=\frac{\kappa }{\kappa -1}\cdot m\cdot \mathrm{R.}\cdot T_0\cdot \left[1-{\left(\frac{p_1}{p_0}\right)}^{\frac{\kappa -1}{\kappa }}\right]$$

with

κ =

Isentropic exponent

m =

Gas mass

R =

Gas constant

T0 =

Gas inlet temperature

p1 =

Relaxation pressure

p0 =

Gas pressure before relaxation

to calculate.

For vapors, this energy is obtained in the case of isentropic expansion from the h-s diagram as the enthalpy difference between the inlet and relaxed state, again depending on the steam pressure, steam inlet temperature and expansion pressure (see e.g. Water and Steam, Springer Verlag Berlin Heidelberg 2000).

As can be seen from equation 1 (the same applies to vapors), the adiabatic energy input will change with constant operating medium mass and with varying inlet temperature or changing pressure conditions.

This also changes the mass throughput of the product to be ground to a desired final fineness. In other words, through a suitable selection of the operating parameters, the ratio of ground material and operating medium mass (-specific operating medium consumption in kg / kg) is variable. In the Fig. 2 is graphically illustrated in a diagram of the specific resource requirement as a function of the grind fineness achieved for a resource pressure of 8 bar (abs) and 4 bar (abs) with talc as an exemplary grist.

x (Fig. 2):

spez. Luftbedarf [m³/kg]

y (Fig. 2):

d50 [③m]

A:

Luft 8 bar(abs), 160°C

B:

Luft 4 bar(abs), 168°C

The specific information in the Fig. 2 are:

x (Fig. 2):

spec. Air requirement [m ³ / kg]

y (Fig. 2):

d50 [③m]

A:

Air 8 bar (abs), 160 ° C

B:

Air 4 bar (abs), 168 ° C

mit

• Q = spezifische Trocknungsenergie
• c_p = spezifische Wärmekapazität
• h_verdunstung = spezifische Verdunstungsenthalpie
• ϕ = relativer Flüssigkeitsgehalt
• ΔT = Temperaturdifferenz Ein-/Austritt

Thermal energy is required for the drying process. It is made up of the energy for heating the moist feed material to the outlet temperature and the enthalpy of evaporation of the liquid contained: $$Q={\mathrm{C.}}_{p,\mathit{Solid}}\cdot \mathit{\Delta T}+c_{p,\mathit{Fluid}}\cdot \phi \cdot \mathit{\Delta T}+H_{\mathit{evaporation}}\cdot \phi$$

with

• Q = specific drying energy
• c _p = specific heat capacity
• h _evaporation = specific enthalpy of evaporation
• ϕ = relative liquid content
• ΔT = temperature difference inlet / outlet

The unit of the specific energy calculated in this way is kJ / kg _solid .

As has now been recognized as the basis of the invention, this energy is introduced into the process by the operating resources: $${\mathrm{E.}}_{\mathit{spec},\mathit{Operating\; m}.}=\frac{{\mathrm{E.}}_{\mathit{therm},\mathit{Operating\; m}.}}{m_{\mathit{Operating\; m}.}}={\mathrm{C.}}_{p,\mathit{Operating\; m}.}\cdot \left(T_{\mathrm{B.}etriebsm\mathrm{.},\mathit{a}}-T_{\mathit{the\; end}}\right)$$

If you divide the specific drying energy according to equation 2 by the thermal energy according to equation 3, you get the specific resource requirements for the entire process: $$\frac{m_{\mathit{Operating\; m}.}}{m_{\mathit{product}}}=\frac{Q}{{\mathrm{E.}}_{\mathit{spec},\mathit{Operating\; m}.}}$$

In the Fig. 3 the specific drying performance depending on the specific use of resources (superheated steam) is shown as an example.

The specific information in the Fig. 3 are: x ( Fig. 3 ): spec. Steam consumption mD, spec [kg / kg] y ( Fig. 3 ): Drying capacity [kgH2O / kgAG] C: delta T = 40 ° D: delta T = 70 °

The application of the method is particularly advantageous in connection with e-Jet (low pressure, hot gas: see EP 2 024 093 B1 by the same inventor) or s-Jet (superheated steam).

Correspondingly, in the method according to the invention for the jet grinding of moist or wet grinding stock in a jet mill 1, such as the fluidized bed jet mill 10, provision is made that moist or wet grinding stock is fed to the jet mill for grinding through the feed nozzle 2 into the grinding chamber 3, that at least one operating parameter of the jet mill 1 is suitably selected via the setting, control or regulation devices 9 so that grinding drying takes place in which the moist or wet grist to obtain an end product with a predetermined final fineness and predetermined residual moisture is simultaneously in the jet mill 1 by grinding to the predetermined final fineness is ground and dried by drying to the predetermined residual moisture, and that finally the end product with the predetermined Final fineness and the predetermined residual moisture is discharged through the end product outlet 7 from the jet mill 1.

As the at least one operating parameter, pre-pressure, expansion pressure or inlet temperature in the jet mill 1 is selected to be suitable for the grinding-drying, namely in such a way that the specific operating resource requirement of the grinding is selected through a suitable choice of the operating parameter (s), pre-pressure, expansion pressure and / or inlet temperature that this is greater than or equal to the specific operating resource requirements of the drying process.

It can also preferably be provided that the actual residual moisture of the ground material before it is discharged from the jet mill 1 or the actual residual moisture of the end product is measured or monitored, such as in particular with the residual moisture detection or monitoring devices 8 assigned to the end product outlet 7, and that the at least one operating parameter of the jet mill 1 once or repeatedly at time intervals or at least approximately continuously for the. Mill drying is suitably set, controlled or regulated depending on the one hand the actual residual moisture of the ground material before it is discharged from the jet mill or the actual residual moisture of the end product and on the other hand the predetermined residual moisture of the end product, such as in particular by means of the setting, control or regulation devices 9.

In the jet milling according to the invention, gases or superheated vapors are preferably used as operating media.

The invention is shown only by way of example based on the exemplary embodiments in the description and in the drawing and is not restricted thereto, but includes all variations, Modifications, substitutions and combinations that the person skilled in the art can take from the present documents, in particular within the scope of the claims and the general representations in the introduction to this description and the description of the exemplary embodiments, and combine them with his expert knowledge and the state of the art. In particular, all of the individual features and design options of the invention can be combined.

List of reference symbols

1

Jet mill

2

Feed nozzle

3

Grinding room

4th

Grinding gas nozzles

5

Classifying wheel

6th

engine

7th

End product outlet

8th

Residual moisture detection or monitoring devices

9

Setting, control or regulation devices

10

Fluidized bed jet mill

Claims (8)

1. Method for jet milling moist or wet material that is to be ground in a jet mill (1), wherein moist or wet material that is to be ground is supplied to the jet mill (1) for milling, characterised in

   that at least one of the operating parameters preliminary pressure, release pressure and admission temperature in the case of the jet mill (1) is suitably selected in such a manner that a milling and drying procedure is performed in which in order to obtain an end product having a predetermined end product fineness and predetermined residual moisture the moist or wet material that is to be ground is simultaneously milled in the jet mill (1) by means of the milling procedure to the predetermined end product fineness and is dried by means of a drying procedure to the predetermined residual moisture,

   that by means of suitably selecting the at least one operating parameter preliminary pressure, release pressure and admission temperature the specific operating means requirement of the milling procedure is selected in such a manner that this operating means requirement is greater than or identical to the specific operating means requirement of the drying procedure, and

   that the end product is discharged from the jet mill (1) with the predetermined end fineness and the predetermined residual moisture.
2. Method according to claim 1,
   characterised in
   that the actual residual moisture of the material that is to be ground prior to the discharge of said material from the jet mill (1) or the actual residual moisture of the end product is measured or monitored.
3. Method according to claim 2,
   that characterised in
   the at least one operating parameter of the jet mill (1) is suitably set, controlled or regulated once or repeatedly in temporal intervals or at least almost continuously for the milling and drying procedure in dependence upon on the one hand the actual residual moisture of the material that is to be ground prior to the discharge of said material from the jet mill (1) or the actual residual moisture of the end product and on the other hand upon the predetermined residual moisture of the end product.
4. Method according to one of the preceding claims, characterised in
   that gases or superheated steams are used as operating means.
5. Jet mill (1) for jet milling moist or wet material that is to be ground to an end product,
   characterised in

   that setting, control or regulating devices (9) are provided so as to set, control or regulate at least one of the operating parameters preliminary pressure, release pressure and admission temperature in the case of the jet mill (1) and the at least one operating parameter preliminary pressure, release pressure and admission temperature in the case of the jet mill (1) is suitably selected by means of said setting, control or regulating devices in such a manner that a milling and drying procedure is performed in which in order to obtain an end product having a predetermined end product fineness and predetermined residual moisture the moist or wet material that is to be ground is simultaneously milled in the jet mill (1) by means of the milling procedure to the predetermined end product fineness and is dried by means of the drying procedure to the predetermined residual moisture,

   that the setting devices, control devices or regulating devices (9) are embodied in such a manner that the specific operating means requirement of the milling procedure is selected by means of suitably selecting the at least one operating parameter preliminary pressure, release pressure and admission temperature in such a manner that this operating means requirement is greater than or identical to the specific operating means requirement of the drying procedure, and

   that the end product outlet (7) of the jet mill (1) is embodied in such a manner that the end product having the predetermined end product fineness and the predetermined residual moisture is discharged from the jet mill (1) through the end product outlet.
6. Jet mill (1) according to claim 5,
   characterised in
   that devices (8) for determining and monitoring the residual moisture are allocated to the end product outlet (7) of the jet mill (1) so as to determine or monitor the actual residual moisture of the material that is to be ground prior to the discharge of said material from the jet mill (1), or to determine or monitor the actual residual moisture of the end product that is obtained by means of milling and drying the material that is to be ground in the jet mill (1).
7. Jet mill (1) according to claim 6,
   characterised in
   that the setting, control or regulating devices (9) are embodied so that the at least one operating parameter preliminary pressure, release pressure and admission temperature of the jet mill (1) is suitably set, controlled or regulated once or repeatedly in temporal intervals or at least almost continuously for the milling and drying procedure in dependence upon on the one hand the actual residual moisture of the material that is to be ground prior to the discharge of said material from the jet mill (1) or the actual residual moisture of the end product and on the other hand upon the predetermined residual moisture of the end product.
8. Jet mill (1) according to one of claims 5 to 7, characterised in
   that gases or superheated steams are used as operating means.

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