DD219787A1

DD219787A1 - PROCESS FOR COOLING FACTIS

Info

Publication number: DD219787A1
Application number: DD25788183A
Authority: DD
Inventors: Juergen Gisbier; Manfred Schoenfeld; Guenther Marotz; Dietmar Blase
Original assignee: Wittol Wittenberg Veb
Priority date: 1983-12-14
Filing date: 1983-12-14
Publication date: 1985-03-13

Abstract

Das erfindungsgemaesse Verfahren bezieht sich auf die Herstellung von weissem Faktis in einer anwendergerechten Form, wobei die Gefahr der Selbstentzuendung beseitigt wird, und gleichzeitig eine Homogenisierung des aufgemahlenen, elastischen Produkts stattfindet. Als wesentliches Merkmal wird dazu eine Wirbelschicht mit dem Kuehlmedium Luft benutzt, die infolge der mechanischen Instabilitaet der Waermeaustauschzone durch einen mechanischen Ruehrer in kurzen Zeitintervallen regeneriert werden muss. Die Regenerierzyklen sind dabei durch FROUDE-Zahlen zwischen 0,025 und 0,442 charakterisiert. Mit veraenderter Dimensionierung, die empirisch aus den Materialeigenschaften (Korngroessenverteilung, Elastizitaetsmodul, Habitus, Kohaesion) ermittelt werden kann, ist das Verfahren auf andere Systeme zwecks Waermeuebertragung anwendbar.The process of the invention relates to the production of white factite in a user-friendly form, eliminating the risk of self-ignition and, at the same time, homogenizing the ground elastic product. An essential feature of this is a fluidized bed with the cooling medium air used, which must be regenerated due to the mechanical instability of the heat exchange zone by a mechanical stirrer in short time intervals. The regeneration cycles are characterized by FROUDE numbers between 0.025 and 0.442. With modified dimensioning, which can be determined empirically from the material properties (particle size distribution, elasticity modulus, habit, cohesion), the method can be applied to other systems for the purpose of heat transfer.

Description

η — Rühfdrehzahl [s"¹] >η - Stirring speed [s " ¹ ]>

d — Rührerdurchmesser [m]d - stirrer diameter [m]

g — Erdbeschleunigung [m-s~²]g - gravitational acceleration [ms ~ ² ]

Wird das Verfahren in einer Wirbelschicht ohne Rührwerk praktiziert, so kommt es zu Kanalbildungen und die Kühlung und Homogenisierung des Produktes ist nach sehr kurzer Zeit nicht mehr nach dem Wirbelschichtprinzip möglich.If the method is practiced in a fluidized bed without agitator, it will lead to channeling and the cooling and homogenization of the product is no longer possible according to the fluidized bed principle after a very short time.

Bei FROUDE-Zahlen unter 0,025 kommt es in einer Wirbelschicht mit Rührer ebenfalls zu den erwähnten Kanalbildungen. Zwar werden die Kanäle beim Durchtritt des Rührers durch den entsprechenden Teil der Wirbelschicht wieder zerstört, sie bilden jedoch nach kurzer Zeit in fast der gleichen Form wieder, so daß es zu keiner stabilen Wirbelschicht kommen kann. Außerdem bilden sich in den Kanälen Agglomerate.With FROUDE numbers below 0.025, the formation of channels in a fluidized bed with stirrer also occurs. Although the channels are destroyed by the passage of the stirrer through the corresponding part of the fluidized bed again, but they form after a short time in almost the same shape again, so that it can not come to a stable fluidized bed. In addition, agglomerates are formed in the channels.

Bei FROUDE-Zahlen über 0,442 wird auf Grund der erheblichen Turbulenz ein großer Teil des Produktes aus der Wirbelschicht ausgetragen, zudem treten auf Grund der erhöhten mechanischen Beanspruchungen große, metastabiie.Agglomerate auf, die nicht erwünscht sind. Hinzu kommt die Tatsache, daß nach relativ kurzer Betriebszeit der Wirbelboden verklebt sein kann und erneuert werden muß.Due to the considerable turbulence, a large part of the product is discharged from the fluidized bed at FROUDE numbers above 0.442. In addition, due to the increased mechanical stresses, large, metastable agglomerates occur which are undesirable. In addition, there is the fact that after a relatively short period of operation, the fluidized bed can be glued and must be renewed.

Unter den erfindungsgemäßen Kühl- und Homogenisierbedingungen resultiert ein Produkt, welches frei von störenden Aggiomeraten und sehr homogen ist. Darüber hinaus ist es durch eine gleichmäßige Temperatur charakterisiert mit einer mittleren örtlichen Abweichung von weniger als ± 1 K. Die gewünschte Kühitemperatur kann entsprechend der zugeführten Wirbelluftmenge durch Wahl der Verweilzeit auf jeden Werts der Lufttemperatur eingestellt werden. Der Apparat, in welchemThe cooling and homogenizing conditions according to the invention result in a product which is free of interfering agglomerates and very homogeneous. In addition, it is characterized by a uniform temperature with an average local deviation of less than ± 1 K. The desired cooling temperature can be adjusted according to the supplied fluidized air volume by selecting the residence time at each value of the air temperature. The apparatus in which

das Verfahren praktiziert werden kann, ist in seinen Abmessungen klein, somit kann er auch nachträglich in die_vmeisten bereits bestehenden Anlagen zur Herstellung von Faktis eingebaut werden.The method can be practiced is small in size, so it can also be retrofitted in the _v already existing plants for the production of Faktis.

Die Erfindung soll nunmehr anhand eines Ausführungsbeispieles erläutert werden. · '..-· ·The invention will now be explained with reference to an embodiment. · '..- · ·

embodiment

In einer diskontinuierlichen Wirbelschichtapparatur mit einem Durchmesser von 0,3 m, die mit einem Blattrührer (Durchmesser 270 mm)·ausgerüstet ist, werden 10 kg weißer Faktis mit einer mittleren Temperatur von 333 K eingebracht, gekühltund homogenisiert. Dabei werden vor Beginn der Durchführung des Verfahrens im Produkt Temperaturdifferenzen von maximal 15K über dem Endwert gemessen. .In a 0.3 m diameter discontinuous fluidized bed apparatus equipped with a blade stirrer (diameter 270 mm), 10 kg of white factite having a mean temperature of 333 K are introduced, cooled and homogenized. In this case, temperature differences of a maximum of 15K above the final value are measured in the product before starting the process. ,

Die Wirbelschichtapparatur mit einem Druckverlust von 220mm WS wird mit einer Luftmenge von ca 25m³/h unter Normaldruckbedingungen und bei einer Temperatur von 291 K beaufschlagt. Der Rührer in der Wirbelschicht wird mit einer Umdrehungszahl von 70min~¹ betrieben. Das entspricht einer FROUDE-Zahl von 0,0375. Nach 20min hat das Material in der Wirbelschicht eine gleichmäßige Temperatur von 303 K.The fluidized-bed apparatus with a pressure loss of 220 mmWC is subjected to an air quantity of about 25 m ³ / h under normal pressure conditions and at a temperature of 291 K. The stirrer in the fluidized bed is operated at a speed of 70 min ^-1 . This corresponds to a FROUDE number of 0.0375. After 20 minutes, the material in the fluidized bed has a uniform temperature of 303 K.

Claims

Invention claim:

Method for cooling and homogenization of Faktis while avoiding sticking and clogging of the apparatus and use of ambient air as a cooling and homogenizing medium, characterized in that the method is carried out in an air-baffled fluidized bed with stirrer, wherein the agitator at a FROUDE number of 0.025 to 0,442 is operated.

Method of cooling factitious
Field of application of the invention

The invention relates to a method for cooling Faktis. Faktis is used as an excipient in the rubber industry; it guarantees dimensional stability in free-vulcanizing rubber compounds and is a filler which greatly increases the abrasion (production of eraser). In addition, it is used as a lightweight additive for bandages in orthopedics.

Characteristic of the known technical solutions

One differentiates

2 main varieties of factis, brown and white factis. While brown factite is prepared from fatty oils by vulcanization with sulfur at temperatures around 410K, using Dischwefeldichlorid as a crosslinker 300 K sufficient, and you get white Faktis for special applications. The reaction in the cold, however, entails that due to the high molecular weight and thus highly viscous reaction products after leaving the usually discontinuously operated reactor nor residues of the starting materials, e.g. Left over sulfur chloride, which are still able to react exothermically.

After vulcanization, the elastic, mostly lumpy product is comminuted, which is preferably carried out in toothed disk mills. In the crushing occurs, in particular by an uneven feeding of the mills, sometimes to local overheating. These overheating are due to the very poor heat conduction properties of the product very slowly and remain as a heat ester z. B. in a subsequent storage, packaged or [öse, received. If the temperature of 350 K is exceeded in this heat test, subsequent reactions in the product can lead to considerable heat developments due to the exothermic nature of these reactions, which can lead to self-ignition of the same.

From the o.g. Reasons make it necessary to cool and homogenize the product Faktis after comminution. These two operations should be carried out simultaneously for technological reasons and in one apparatus. It is known to use water-cooled mixers for cooling factitious products. However, because of adhesions to the heat transfer surfaces and the mixing tools, these apparatuses must be cleaned in very short intervals in order to maintain their functionality. In addition, the required quantity of cooling water is not available in every production situation for factice. It is also known, for the cooling of fact-like products continuously or discontinuously operated rotary drums, which are charged with cooling air to use. However, these drums must be very large due to the fact that a very large heat exchange area is required for cooling. In addition, it often leads to blockages of the internals, so that it comes to stoppages and cleaning work is required.

Object of the invention

The aim of the invention is a continuous or discontinuous cooling process with simultaneous homogenization of the product Faktis. The technological downtimes caused by sticking and blockages have been eliminated by the product properties. In addition, the dimensions of the apparatus and thus the space requirement should be reduced to a minimum, so that the process can also be implemented later in existing systems. Furthermore, air with ambient temperature for cooling as a medium should be used.

Explanation of the essence of the invention

It has now been found that fact, which is partially heated in a mill, can be cooled and at the same time homoeoperated, without causing undesirable adhesions or blockages, when the cooling and homogenization is carried out in a fluidized bed apparatus with agitator Agitator is operated with a FROUDE number of 0.025 to 0.422. As the fluidizing and cooling medium, air at ambient temperature is used. The FROUDE number is to be understood as the following relationship: