EP0573885B1 - Rapid packager drier dor drying sludge with a filtering arrangement - Google Patents

Abstract

A rapid package dryer for drying sludges, pastes and other air-permeable substances is proposed, in which the material to be dried, e.g. the sludge, is applied to a conveyor belt, which runs sealed through a closed housing and which has one or more drying zones, each drying zone being composed of at least one fan and possibly one heat source through which the flow from the fan passes and the air transported by the fan being injected into a pressure space from which it permeates through recesses to the sludge to be dried and the conveyor belt and is received by a suction space on the opposite side of the conveyor belt, from which suction space the air, after an appropriate treatment, is returned to the pressure space. In order to remove as far as possible the dust produced during drying, it is provided that the air, after flowing through the sludge to be dried, flows through a filter belt, which is continuously driven and to which are assigned one or more cleaning units for cleaning the filter belt. <IMAGE>

Description

The invention relates to a through-flow dryer for drying sludge according to the preamble of patent claim 1.

Flow-through dryers of this type are used for drying sludges of all kinds, and it is a continuous process. The sludge to be dried is placed on a conveyor belt and is moved into the housing of the drying system, the inlet area and the outlet area of the housing being sealed.

In the housing, pressure spaces are distributed in a manner known per se, spaced apart from one another in the transport direction, into which heated air is blown, which air passes through the sludge stored on the belt and enters an underlying suction space. The air is sucked out of this suction space again and led again in the circuit into the pressure space.

In the previously known through-flow dryers, however, there is the disadvantage that an undesirable dust development occurs during drying. This dust is deposited in poorly flowed places in the pressure chamber and in the suction chamber, pollutes the fan and there is also a risk of dust explosion.

For this purpose, it is known to provide dust cleaning in the exhaust air, the exhaust air being conducted in a cyclone separator, and for the most part being separated there. A separation is also in the Exhaust air flow known in that the exhaust air flow is passed through a stationary filter.

Both the cyclone separation and the separation by stationary filters have the disadvantage that the efficiency of the separation is insufficient and that the arrangement of cyclone separators with a sufficient separation performance is relatively complex.

The invention has for its object to develop a through-flow dryer with a filter arrangement of the type mentioned in such a way that a higher efficiency of dust separation is achieved with relatively low manufacturing and maintenance costs.

To achieve the object presented, the invention is characterized by the technical teaching of claim 1.

An essential feature of the invention is that below the conveyor belt on which the sludge to be dried is guided in the housing in the longitudinal direction, at least one filter belt is arranged in the suction space, which is traversed by the dust-laden air that flows through the conveyor belt for the sludge to be dried becomes.

It is essential here that the filter belt is driven, and there are different embodiments for the type and design of the drive.

In a first, preferred embodiment of the invention it is provided that the filter belt is driven at a continuous speed, the speed being approximately equal to the speed of the conveyor belt for the sludge.

In another embodiment of the invention it is provided that the Filter belt is driven counter to the running direction of the overhead sludge conveyor belt and in a third embodiment it is provided that the drive of the filter belt - in one direction or the other - is not continuous, but intermittent.

Driving the filter belt at approximately the same speed as the sludge drying belt is only a preferred embodiment, the present invention encompassing all drive speeds of the filter belt.

The present invention therefore provides for the first time a through-flow dryer, in the suction space of which an air stream contaminated with dust passes through a movably driven filter belt.

In the following description, the various cleaning options of the filter belt are described, it being preferred that the filter belt is penetrated by a cleaning air stream, whereby a blow box is arranged below the filter belt at mutual intervals in the running direction of the filter belt, one approximately perpendicular to the Level of the filter belt directed air flow directed against a suction box arranged above the filter belt. This removes the dust on the filter belt, removes it from the pores and meshes of the filter belt and takes it into the suction box.

It is preferred here if the underside of the suction box is not formed in a plane parallel to the plane of the filter belt, but if the underside of the suction box is chamfered, ie the filter dust initially runs into a conically narrowing space on the underside of the suction box. The dust can accumulate on the filter belt at a certain height; the upper layers are then only taken up by the flared, first area on the underside of the suction box. The dust is thus gradually removed so that the thinner layers of dust then reach the conically narrowed area on the underside of the suction box and can be extracted with high efficiency.

The filter belt can be designed as a plastic sieve belt with a certain sieve opening; however, it can also be designed as a filter fleece, which consists either of paper, plastic, textile material or the like. It is also possible to design the filter band as a metal band.

For cleaning the filter belt, only the suction box, which is arranged above the filter belt, is in itself necessary for the solution, because a blow box arranged below the filter belt is not absolutely necessary. This is because the air sucked in by the suction box could also be taken directly from the suction space of the entire dryer housing, which, however, has the disadvantage that this air has to be supplied additionally and has to be warmed up accordingly in the subsequent delivery.

To save energy, a separate blow box is therefore arranged below the filter belt, through which a separate, unheated air flow is directed against the filter belt.

As a cleaning device in addition to the mentioned suction cleaning other devices are also considered, such. B. compressed air cleaning, or brush cleaning. The cleaning methods described can also be combined with one another.

It is also possible to clean with a high-pressure water jet.

The advantage of a moving filter belt is the automatic cleaning of this filter belt, which is not the case with static filters.

The subject matter of the present invention results not only from the subject matter of the individual patent claims, but also from the combination of the individual patent claims with one another. All of the information and features disclosed in the documents - including the summary -, in particular the spatial design shown in the drawings, are claimed to be essential to the invention, insofar as they are new to the prior art, individually or in combination.

The invention is explained in more detail below with the aid of drawings which illustrate only one embodiment. Here, from the drawings and their description, further features and advantages of the invention that are essential to the invention emerge.

Figur 1:

schematisiert einen Schnitt durch einen Durchström-Trockner nach der Erfindung;

Figur 2:

der Schnitt gemäß der Linie II-II in Figur 1.

Show it:

Figure 1:

schematized a section through a through-flow dryer according to the invention;

Figure 2:

the section along the line II-II in Figure 1.

The through-flow dryer essentially consists of a hermetically sealed housing 1, which is correspondingly thermally insulated in order to avoid heat losses. The housing 1 has a front inlet area 2 and a rear outlet area 3.

The housing 1 is divided into different dryer zones, each dryer zone being designed identically, after which it is sufficient to use only one to describe only dryer zone. It goes without saying that only a small number of dryer zones are shown in the drawing shown; any number of dryer zones can be arranged in a row in the housing 1.

Each dryer zone consists of a fan 4 (see FIG. 2) attached to the side, which is flanged to the side of the housing 1 in a separate housing part 5. According to FIG. 2, this housing part 5 can be moved away from the housing 1 in order to make the fan more accessible.

The fan generates compressed air, which it blows into a pressure chamber 35 of the housing 1 via an inflow funnel 6. The air then flows in the direction of arrow 9 from the inflow funnel 6 into the pressure chamber 35 and exits via recesses 25 on the underside of the pressure chamber 35 and thus flows directly through the sludge 22 to be dried and guided along a conveyor belt 18 below the recess 25.

The pressure chamber 35 is formed by the blow box 24.

The conveyor belt 18 is guided over an inlet-side tension roller 26 and an outlet-side drive roller 27. In the area of the housing 1, the conveyor belt 18 runs over a series of support rollers 23.

In order to avoid an undesired bypass of the heated air from the pressure chamber 35 into the suction chamber 36, lateral partition walls 33 are provided on the support rollers 23.

The air then flows through the filter band 28 to be described later, where the dust discharged from the sludge to be dried is deposited as filter dust 37.

After the air has flowed through the filter belt 28 in the direction of the arrow 34, the air thus enters the suction space 36 and is sucked off into the fan via a return flow channel 7. A heat source 8, which heats the air, is arranged in the return flow channel 7.

The sludge to be dried is fed in the direction of arrow 20 into a feed device 19 which is designed as a twin-screw discharge device. In this way, the sludge to be dried is applied to the conveyor belt 18 at a uniform height. Air must be able to flow through the sludge to be dried, therefore it is provided that the sludge is pelletized in order to create flow-through spaces.

For the air-side sealing of the housing in the inlet area 2, a cellular wheel sluice 21 is arranged there, which engages sealingly with its cellular wheel in the sludge to be dried.

In a further development of the present invention it can be provided that a turning wheel 10 is arranged between the individual dryer zones of the through-flow dryer, which receives and turns the sludge. Here, the turning wheel has shovel-like arms which are rotated counter to the transport direction of the sludge 22 so that each shovel arm picks up a portion of the sludge, turns it over and places it back on the conveyor belt in the transport direction.

A blowing duct 11 is arranged on the underside of the turning wheel 10, through which the air is blown in the direction of the arrow 12 against the underside of the conveyor belt 18.

The space enclosed by the turning wheel 10 is in this case hermetically sealed by a suction duct 13 through which the air generated in the blowing duct 11 is extracted.

The cleaning of the filter belt 28 is described in more detail below.

It is first noted that the filter band extends through the entire housing; However, it can also be provided that the filter band 28 does not extend through the entire length of the housing 1, but is only arranged at the points where dust is to be expected.

The cleaning of the filter dust 37 on the filter belt 28 is carried out by a cleaning unit 14, which is essentially formed from a blow box 15 arranged below the filter belt 28 (which is arranged in the suction chamber 36), the air box in the blow box 15 generating a separate air flow from the main air flow Flows through the filter belt in the direction of the arrow 12 from below and, after the filter belt has passed through, is received by a suction box 16 arranged above the filter belt but still in the suction chamber 36.

It is important that the underside of the suction box 16 has a conical bevel 17, this bevel having a large flow cross-section in the transport direction of the filter belt. This means that the filter dust 27 transported in the transport direction 38 into the lower region of the suction box 16 first reaches a suction chamber of larger cross-section, where the filter dust is removed in its upper regions.

With increasing transport in the direction of transport 38 in the direction of the suction spaces of smaller cross-section in the area of this incline 17, the suction on the filter dust 37 increases, which is therefore lifted off with increasing suction power. In this way, the filter belt is optimally cleaned.

The length of the suction path, ie the length of the blow and suction box 15, 16 in the transport direction 38 must be adapted to the respective conditions, ie the type and amount of the filter dust and the transport speed in the transport direction 38.

Likewise, it is not necessary for a solution that such a cleaning unit 14 must be arranged in each zone of the housing, it is sufficient if at least one cleaning unit 14 is provided.

In addition, the filter belt is circulated via a tensioning roller 29 arranged on the entry side, via intermediate support rollers 31 and via a drive roller 30 arranged on the discharge side. Incidentally, it is pointed out that there are exhaust air pipes 32 on the side walls of the housing according to FIG. 1, via which the moist air is led from the suction chamber 36 to a central exhaust air fan. Moreover, it is pointed out that the term "sludge 22" is not to be understood as restrictive in the sense of the present invention. "Sludge" means all media to be dried, ie pasty, powdery and piece-like goods that pass through the throughflow dryer mentioned.

DRAWING LEGEND

• 1 housing
• 2 entry area
• 3 outlet area
• 4 fan
• 5 housing part
• 6 inflow funnels
• 7 return flow channel
• 8 heat source
• 9 arrow direction
• 10 turning wheel
• 11 blow channel
• 12 arrow direction
• 13 suction channel
• 14 cleaning unit
• 15 blow box
• 16 suction box
• 17 slant
• 18 conveyor belt
• 19 feed device
• 20 arrow direction
• 21 rotary valve
• 22 mud
• 23 idler
• 24 blow box
• 25 recess
• 26 tension roller
• 27 drive roller
• 28 filter belt
• 29 tension roller
• 30 drive roller
• 31 idler
• 32 exhaust pipe
• 33 side partition
• 34 arrow direction
• 35 pressure chamber
• 36 suction chamber
• 37 filter dust
• 38 Transport direction

Claims (7)

1. Throughflow dryer for drying sludges, pastes and other air-permeable beds, consisting of a closed casing (1) with at least one drying zone (la), which comprises a fan (4), a heat source (8) through which drying air flows, a suction chamber (36), which is connected to a pressure chamber (35) for blowing in dry air, a return line (7) for conducting the drying air back from the suction chamber (36) via the fan (4) to the pressure chamber (35) and a circulating conveyor belt (18) for the sludge (22), which belt passes through the casing (1), characterised in that there is disposed, in the suction chamber (36), below the conveyor belt (18), at least one filter belt (28) which is actuated in circulation and which extends over the entire length of the at least one drying zone (la) and through which the drying air flows when it has flowed through the sludge (22) which is to be dried; and in that cleaning units (14) are allocated to the filter belt (28) for the cleaning thereof, which cleaning units consist of at least one suction box (16) comprising a suction channel and disposed above the filter belt (28), and a blowing box (15) disposed substantially opposite and below the filter belt (28).
2. Throughflow dryer according to Claim 1, characterised in that the filter belt (28) is shorter than the length of the casing (1).
3. Throughflow dryer according to Claim 1, characterised in that the filter belt (28) is actuated continuously or intermittently in the transport direction (38) of the conveyor belt (18) or in the direction which is opposite thereto.
4. Throughflow dryer according to Claim 1, characterised in that the blowing box (15) comprises an outflow surface which is substantially parallel to the plane of the filter belt (28); and in that the suction box (16) comprises a suction surface which is formed as a slanting part (17) angled in relation to the transport direction (38) of the filter belt (28).
5. Throughflow dryer according to Claim 1, characterised in that the air supply to the blowing box (15) and the air discharge out of the suction box (16) of the cleaning unit (14) are separated from the conducting of air through the conveyor belt (18) for drying the sludge (22).
6. Throughflow dryer according to Claim 1, characterised in that the sludge (22) to be dried is turned on the conveyor belt (18) by a turning arrangement (10, 11, 12, 13).
7. Throughflow dryer according to Claim 6, characterised in that the turning arrangement (10, 11, 12, 13) is disposed between drying zones (1a, 1b) which are adjacent one another in each case.

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