CS258234B1 - A method of continuous drying of the penteerythrotol - Google Patents

Abstract

The solution concerns a method of continuous drying of pentaerythritol in a fluidized bed dryer. Drying is carried out in a stream of hot air with a temperature in the range of 140 to 175 °C through a layer of dried material with a height of 0 to 150 mm at a variable frequency of shaking of the vibrating grid in the range of 5 to 30 Hz and an amplitude in the range of 0.5 to 2.5 mm.

Description

258234 2

BACKGROUND OF THE INVENTION The present invention relates to a process for the continuous drying of pentaerythritol and similar chemical substances which are susceptible to abrasion during fluidization or more intense mixing with airflow and contain a variable proportion of dust particles.

The prior art drying and heat treatment units are generally characterized by a control of the drying process that does not provide optimum process parameters and maximum utilization of the drying equipment. This is an obvious consequence of the underestimation of the importance of this operation in the development and modernization of manufacturing and technological processes. In particular, the application of the drying process and the drying apparatus must be based on the first characteristic of the characteristics of the material to be dried.

Thermal degradation of material, wiping, agglomeration of particles, event. the cracking of materials is an important characteristic of the drying process and the selection of a suitable drying device. These properties must be adapted to the drying process in the selected facility to optimally dry the drying. These questions are elaborated and, for specific examples, also discussed in the literature, such as in Processing, May 1985, pp. 12-14 and 16, 21.

Similar is the drying of crystalline pentaerythritol. The disadvantages of the prior art pentaerythritol drying are of a dual nature. Bud is an insufficient drying efficiency of the orbiting large loss of product due to the increase in the workload of high dust particles.

When the product is poorly dried, it not only adversely affects its quality, but also causes great difficulties in handling the product, from the transport of the devices. In pneumatic transport, the poorly dried material adheres to the walls and causes clogging of transport routes and handling fittings.

The relatively high drift of pentaerythritol dust particles is characterized mainly by the application of fluid-type drying devices. Fluid driers provide good drying of the product, but at the expense of increased pentaerythritol losses due to drift and increased abrasion that occurs during intensive and long-term mixing of the dried material in the fluid bed.

The required relatively long drying time results from the property of wet crystal pentaerythritol. The drying rate is high from the initial humidity, usually from 8 to 15% by weight. to a moisture of 1% wt. But drying the substance to the desired final value of not more than 0.2% by weight. already requires a very long drying time. In addition, there is a high demand for air, which makes the drying operation even more expensive.

An important parameter is the drying temperature. At a higher temperature, the pentaerythritol magnesium is melted, and on hot metal grates it can seal the air intake openings, thereby significantly deteriorating the drying process.

Also, the clumping that occurs in wet material is a phenomenon deteriorating the process of drying pentaerythritol.

These drawbacks are eliminated by the continuous drying process of pentaerythritol in a fluid dryer, in which the pentaerythritol is dried in a hot air inlet layer at a temperature in the range of 140-175 ° C, preferably in the range of 160-169 ° C, with a drying of 20-150 mm high, preferably 90 to 110 mm, at variable frequencies, within a range of 5 to 25 Hz and an amplitude of 0.5 to 2.5 mm, determined by drying the dust to the same moisture value as the dried product.

In this method of drying pentaerythritol, more surprising positive effects have been found. In particular, it has been shown that a higher drying efficiency is achieved at a lower flow rate of 3,282,334 air compared to the value determined from the fluidization requirement. It is of interest here that the admission of air flow decreases the amount of lump fraction. Dryer operation even more stable at lower airflow, which points to a uniform drying process.

This result is apparently the result of the complex influence of the new drying parameters on the agitation of the dried material on the vibrating grate, whereby the heat and mass flow between the solid and gaseous phases is intensified, but the rubbing and shrinkage is reduced by reducing the number of solids. The natural consequence of this is to reduce drift and prolong the contact of the dust particles with the drying air, thereby significantly improving the drying efficiency and the reliability of the operation, since the practical whole drift is also perfectly dried, respectively. to the same value as the main bulk of the dried material leaving the dryer. At higher airflows, it is dry-dried, so it clogs the routes into cyclones as well as the cyclone separator itself and the fitting for dust collection from the separators. In addition, the non-dried drift cannot be combined with the dried major portion of the product leaving the dryer because it would increase the moisture of the product above the allowable limit. An important element of the new method of drying pentaerythritol is the frequency and amplitude of the grating. Among the average moisture-dried product after having missed the major proportion of the dust-laden drier from the cyclone and the properties of the dried-material layer on the vibration meter is a functional link that is used to control the drying process by controlling the frequency and amplitude of the vibration. In this way, a system of polydisperse particles is formed which limits the clumping of the dried material particles.

Smaller, scored particles remaining in the layer are likely to have a beneficial effect on the formation of more suitable conditions for improving the contact of all solids by air, such as a more homogeneous layer formed at a higher air velocity.This results in a perfect drying of the material leaving the dryer and perfect drying pentaerythritol dust drift, with lower thermal energy consumption.

Examples which illustrate but do not limit the scope of the novel pentaerythritol stimulation are given. Přikladl

The pentaerythritol drying was carried out on a device schematically shown in Fig. 1. The apparatus consists of a vibrofluid drier 7, to which a dry dust drift separator is connected from a drier and a wet separator 9, which serves to remove dust residue from the outgoing air. The air is sucked in by the fan 10 and extruded into the atmosphere. The air to the dryer is fed through line 1. It is first heated in the steam heater 2 and the desired temperature is heated in the electric heater. entrained crumbled in the disintegrator 6. The dried oven material is connected to the dried powder dust on the sieve 11, separated from the air in a dry separator of the cyclone type. Fig. 1 is not plotted. The screened dried pentaerythritol is continuously discharged via the packaging path 12.

The moisture content of the pentaerythritol to be dried is 8.1 wt%. Its quantity is 750 kg.h -'3 -1 after conversion to dry material. The supply air is 3,900 m .h. The temperature and the oven grate are 163 ° C. The pressure difference on the oven is 1 630 Pa. The drying is carried out at a layer height of 100 mm, formed at a grate frequency of 14 Hz and at a grating amplitude of 2.2 mm.

In this way of drying, the permanently low humidity was achieved in the long-term operation of the apparatus

Claims (4)

OBJECT OF THE INVENTION Process for the continuous drying of pentaerythritol in a fluidized-bed dryer, in which the cyclone dust off after separation from the drying air is combined with the dried product leaving the dryer, characterized in that the drying of the product in the dryer is carried out in a hot air stream of temperature 140 to 175 ° C, preferably in the range of 155 to 165 ° C, through a layer of dried material of a height of 20 to 150 mm, preferably of a height of 90 to 110 mm, at a variable shaking frequency of the vibrating grate of 5 to 30 Hz with a shaking amplitude in the range 0.5 to 2.5 mm, where the shaking frequency is continuously varied such that the dried dust drift has the same moisture value as the dried product coming out of the dryer.