GB2111854A

GB2111854A - An apparatus for the thermal protection of a filtering unit

Info

Publication number: GB2111854A
Application number: GB08230401A
Authority: GB
Inventors: Vaclav Svatos
Original assignee: Stavby Silnic A Zeleznic N P
Current assignee: Stavby Silnic A Zeleznic N P
Priority date: 1981-10-30
Filing date: 1982-10-25
Publication date: 1983-07-13
Also published as: IT1153329B; DD252079A3; CS230308B1; GB2111854B; IT8224015A0; FR2515527A1; DE3240227A1

Abstract

An apparatus for the thermal protection of a filtering unit for filtering dust laden hot air, the unit comprising a filtering chamber (30) containing a filtering medium damageable by excessive temperature. The filtering chamber has an outlet, communicating through a suction pipe (31), via a suction valve (32), with a suction fan (33), and an inlet, communicating, via a hot-air pipe (22) closable at its outlet end by a protective valve (25) with the outlet of a source of dust laden hot air. The hot-air pipe is provided with two spaced apart thermometers (23,24). A closable bypass pipe (50) is provided between the suction pipe and the hot-air pipe. <IMAGE>

Description

SPECIFICATION An apparatus for the thermal protection of a filtering unit The invention relates to an apparatus for the thermal protection of a filtering unit.

Apparatus of this kind is designed for dust removing systems, and particularly for bitumen composition precoating plants, wherein stoneware is heattreated in hot-air driers. Downstream of the outlet of such a drier is situated a cyclone separator which communicates via a hot-air piping with the inlet of the filtering unit proper containing a filtering filling, mostly a textile fabric.

A disadvantage of the hitherto used plants of this type consists in that the thermal regime upstream of the filtering chamber is almost uncontrollable so that the filtering fabric, due to overheating, becomes damaged, or even burnt. This results not only in the failure of the expected filtering effect but also in a pollution of the environment of such plant, which may be so extensive that its further operation must cease. Needless to say that this adversely influences the productivity of such plants to a considerable extent or that they have to be moved to sparsely inhabited territories, which cause further complications. Apart from this, the filling of the filtering unit, i.e. the textile fabric, deteriorated by burning has to be removed and replaced with a fresh one.

Another disadvantage of the well-known apparatus of this kind is in that the thermal regime upstream of the filtering chamber cannot be interfered with so as to prevent the filtering chamber filling from being damaged by temperature fluctuations of the hot air blown thereinto, and particularly by an unexpected temperature rise at the outlet of the hot-air drier to which stoneware is supplied from outside. Decisive is the temperature of air downstream of the cyclone separator and upstream of the inlet to the filtering chamber.

It is an object of the present invention to eliminate, or at least alleviate, the disadvantages of prior art as hereinabove set forth and to provide an improved apparatus for the thermal protection of filtering units.

In accordance with the invention, there are installed at two opposite ends of the hot air piping, i.e. the piping which connects the outlet of the cyclone separator with the inlet of the filtering chamber, two spaced apart thermometers, viz. an inlet thermometer and a protective thermometer, respectively.

The inlet into the filtering chamber is disposed downstream of said protective thermometer. The outlet of the filtering chamber communicates, through a suction piping and via a suction valve, with a suction fan, a closable bypass pipeline being provided between said suction piping and the hot-air piping.

To increase the total technical effect, the apparatus comprises several additional features. According to the first one, there is provided a controllable cooling connection which enters the intake of the hot-air piping into the filtering chamber and which is designed for conveying fresh cool air from the exterior into the system.

Other additional features make it possible not only to improve the operational control of the entire plant but also to automate the operation thereof. These features include: - An evaluating unit which is coupled to electric al outputs of the two thermometers, - The outputs of said evaluating unit are con nected to a control unit.

- The outputs of the latter are operationally coupled to at least some of the controlling valves employed in the apparatus.

- At least one of the above-mentioned thermo meters is equipped with a transmitter of the measured values.

A preferred embodiment of an apparatus according to the invention will hereinafter be described, by way of example, with reference to the accompanying diagrammatic drawing.

A hot-air drier 10 is provided at one end with a burner 11 having a fuel supply 12 and at the other end with a rest chamber 13 below or through which extends a stoneware supply conveyor 14. A lateral outlet of said stilling chamber 13 opens into an outlet piping 15 by which the chamber 13 communicates with a cyclone separator 20; downstream of the outlet 21 of which is situated a hot-air piping 22. In this piping 22 is installed a protective valve 25, downstream of which is situated the inlet of a filtering chamber 30. The outlet of said filtering chamber 30 communicates through a suction piping 31, a suction valve 32 and a suction fan 33 with the inlet of a chimney 40. This arrangement is known from prior art.

In accordance with the invention, there are additionally provided two thermometers situated, respectively, at the beginning and at the end of the hot-air piping 22 namely an inlet thermometer 23 and a protective thermometer 24 which are connected within the circuit of an evaluating unit 70.

Apart from this, the hot-air piping 22 and the suction piping 31 are interconnected by a bypass pipeline 50 provided with a bypass valve 51 and a bypass controller 52, the latter being adapted to be remotely controlled from a control unit 80. Also the protective valve 25 installed in the hot-air piping 22 is controlled from said control unit 80. Downstream of the protective valve 25 is installed in the hot-air piping 22 a cooling connection 60 comprising a cooling valve 61 together with a cooling controller 62 the latter being also coupled to the control unit 80. In case of unexpected outage of the supply mains, the apparatus can be manually controlled according to the readings on the two thermometers 23 and 24 installed in the hot-air piping 22.

At the beginning of operation, the two valves 25 and 32 are open while the bypass valve 51 in the bypass pipeline 50 is closed. Also the cooling valve 61 in the cooling connection 60 is closed. The suction fan 33 is continuously in operation.

If the temperature of air exceeds the value set on the inlet thermometer 23 the apparatus allows the following modes of intervention to prevent any malfunction thereof: Through the cooling connection 60, via the cooling valve 61, which latter is opened by the control unit 80 in dependence upon the reading on the inlet thermometer 23, the hot-air piping 22 is supplied immediately with ambient cool air. If such sucked-in cool air is sufficient to cool the hot air flowing through the hot-air piping 22, then the protective valve 25 remains open and the cooled airflows into the filtering chamber 30.

If, however, the cool ambient air sucked-in through the cooling connection 60 does not suffice to cool the hot air in the hot-air piping 22 to a temperature harmless for the filtering textile fabric, the temperature will reach the value preset in the evaluating unit 70 for the protective thermometer 24 (i.e. a temperature critical for said fabric) whereupon the protective valve 25 is completely closed by the control unit 80.

Simultaneously with the closing of the protective valve 25, the bypass valve 51 in the bypass pipeline 50 is opened.

If necessary, the above interventions can be, both as to their intensity and duration, appropriately combined with one another, depending upon the values picked up by the evaluating unit 70, the relevant factors being the temperature and the temperature gradient in the hot-air piping 22.

The evaluating unit 70 can be stored also with other factors which may influence the operation of the complete plant, such as temperature, pressure and humidity of air and temperature in the hot-air drier 10.

Claims

1. An apparatus for the thermal protection of a filtering unit for filtering dust laden hot air, the unit comprising a filtering chamber containing a filtering medium damageable by excessive temperature, the filtering chamber having an outlet, communicating through a suction pipe, via a suction valve, with a suction fan, and an inlet, communicating, via a hot-air pipe closable at its outlet end by a protective valve with the outlet of a source of dust laden hot air, wherein the hot-air pipe is provided with two spaced apart thermometers, a closable bypass pipe being provided between the suction pipe and the hot-air pipe.

2. An apparatus according to Claim 1, wherein the hot-air pipe additionally communicates with a controllable cooling connection for introducing ambient air.

3. An apparatus according to Claim 1 or 2, wherein the two thermometers have electric outputs interconnected within the circuit of an evaluating unit.

4. An apparatus according to Claim 3 wherein the valves are controlled by controlling elements and the evaluating unit has outlets connected to a control unit the outputs of which are connected to at least some of the controlling elements of the valves.

5. An apparatus according to any one of the preceding claims, wherein at least one of the thermometers is equipped with a transmitter of the measured temperature values.

6. An apparatus for the thermal protection of a filtering unit, constructed, arranged and adapted to operate substantially as herein described with reference to, and as shown in, the accompanying diagrammatic drawing.