Process and apparatus for continuous drying of material, especially sewage sludge.

0001The invention relates to an apparatus for continuous drying of Well, in particular sewage sludge, with a belt, in particular screen belt on which the material is conveyed. Furthermore, the invention relates to a Method for drying material, in particular sewage sludge, said Good on a belt, in particular screen belt through a dryer is promoted.

0002Belt dryers are long for different purposes used. The disadvantage here is so far the uneven distribution of the goods on the circulating belt, in particular screen belt, whereby the material at locations overdried with too low film thickness and not sufficiently dried in other places with too high bulk thickness becomes. When drying of pasty and / or sticky substances, eg. B. Sewage sludge, they have in front of a uniform application to the Band, in particular screen belt into particles of constant as possible Dimensions are formed. This takes place in facilities for sewage sludge according to the prior art in that with these substances high pressure through dies pressed. In practice it has been shown that these matrices by foreign bodies in the product to be dried for constipation tend, which has a very detrimental even to the drying effect. Furthermore, the dryer must partially once per shift for Cleaning these matrices will be decommissioned. A plant of this kind is in WO 92/00250 described. Also known from EP 0781741 B1 or EP 0889014 B1 are known such plants. Additionally, these Systems very sensitive to changes in the Schtammeigenschaften. The aim of the invention is therefore to provide a method and an apparatus, with a uniform distribution of the material to be dried, in particular pasty and / or sticky substances on the tape, in particular a belt dryer screen belt is ensured. The invention is therefore characterized in that for applying of the material on the belt, in particular screen belt at the entry a distribution screw above the belt, in particular screen belt is arranged. By these embodiments can be dried goods, such as wood chips, Biomass, grain, rejects in paper mills, as well as household waste or Sludge relatively evenly over the band, particu particular screen belt distribute the dryer. An advantageous development of the invention is characterized, that a calibrating roller above the belt, in particular screen belt is arranged, wherein the calibrating be designed height adjustable can. In addition, when in the field of distribution screw a level sensor is arranged, is a more even distribution of the achieved drying. Advantageously has proven when the calibrating against the Conveying direction of the belt, in particular screen belt rotates, the Rotational speed greater than the conveyor speed can be. Thus, the excessive amount of material to be dried back to promoted the field of distribution screw and thus a more even achieved distribution. For the drying of pasty and / or sticky substances, such as Sewage sludge, it is advantageous if the distribution screw with a Mixer for mixing Rückmischgut, especially a partial flow the dry end product, and fresh material, in particular slurry, communicates, wherein the mixer is a ploughshare mixer, may be twin-shaft mixer or paddle mixer. By backmixing of already dried well with fresh material, for example Slurry, the air permeability of the paste-like and / or sticky substances can be adjusted and it is the uniform Distribution on the tape, in particular screen belt favored. If the mixer with a discharge device for a Rückmischgut Remixing silos connected and has the Rückmischsilo a discharge, in particular discharge screw, for the accept, for example, Granules, on, a particularly cost-effective and reliable Plant to be built, in which the discharge amount of the accept, eg granules automatically controls. A particularly cost-effective variant of a dryer can be realize, if the belt, in particular a screen belt dryer hood is arranged, which extends over the entire band, in particular Screen belt including distribution screw extends, said supply lines dryer may include that of along the both sides Dryer and extending openings for the exit of the drying gas exhibit. Are the supply lines connected to each other by means of adjustable tie rods, can Trockenhaube executed in very light construction and adjusted for optimum seal with respect to the frame of the dryer will. For dryers with high throughput line results in a cost-effective Type by running the dryer covered part or all of Dryer housing in concrete. To relieve the environment by condensation of the vapors or Treatment in a biofilter, it has proven to be advantageous if below the belt, particularly filter belt distribution devices, especially injection tubes are provided. The invention also relates to a method for drying products, especially Sewage sludge, the Good on a belt, in particular Screen belt is conveyed through a dryer. It is characterized in that the material is fed via a distribution screw, wherein the level is changed by changing the belt speed, wherein with an increase of the level in the distribution screw, the tape, especially accelerated screening belt or in a lowering of Levels decreased in the distribution screw the belt speed may be, until the level has reached the target value.

0003For pasty and / or sticky substances to be dried, it is particularly advantageous when the material to be dried, the fresh Good, particularly slurry and rückgemischtem Good, especially Granules, there, and back mixed Good quantitative control of a Reservoir, in particular Rückmischsilo is withdrawn, the excess dried material, in particular granular, as accept from the reservoir can be removed. This allows an automatic Control the discharge amount of the accepted stock particularly reliable be achieved. To relieve the environment, it is advantageous if, below the belt particular screen belt is sprayed in the dryer and the water Vapors condensed respectively. be saturated. The invention will now be described by way of example with reference to the drawings, wherein Fig. 1 is a schematic diagram of a belt dryer according to the invention, FIG. 2 is a diagram of a band dryer invention, Fig. 3 is a longitudinal view, and Fig. 4 is a cross view of an inventive show dryer. Fig. 1 represents a scheme of a dryer 1 having a belt, in particular Screen belt 2 is in which an astringent to Good 3 via a distribution screw applied to the belt, in particular screen belt 2 and is then evened out by a calibrating. 5 The Band, in particular screen belt can consist of plastic or Woven metal. In the field of distribution screw 4 is a level sensor 6 is arranged, which controls the tape speed, whereby at an increase of the level in the distribution screw, the tape, in particular Screen belt is accelerated or when a drop of the level in the Distribution screw, the tape speed is reduced until the level has reached the setpoint. by by tossing back the goods the sizing roll 5 on the one hand after calibrating a uniform reached distribution, on the other hand is at a higher feed rate, this led into the region of the sensor, whereby the control of the Belt speed responds quickly. Drying takes place by convection via line 7 supplied hot air, here by way of example in a heat exchanger 8 by means of waste heat utilization is for example heated by steam, flue gas or hot water. The air can be heated directly or indirectly by a burner will. The coupled-loaded from the air circuit with moisture Air (vapor) is partially withdrawn via line 9, a Capacitor / saturator 10 and optionally supplied to a biofilter 11, before the exhaust air 12 is released to the environment. Before the dried material 14 emerges from the dryer it is advantageously still cooled by cooling air. 13 This cooling air can flow through a possibly existing dry vacuum from the environment respectively be drawn as exhaust air from the peripheral components. In FIG. 2, the same parts are provided with the same reference numerals as in Fig. 1. In addition, here is the possibility of supply of hot air in two or a plurality of heating zones through line 7 and 7 'are shown. The warming in the heat exchanger 8 is carried by the flue gases of a burner 15th Besides there is the possibility of warming also eg by hot water, Steam or thermal oil. The dried material, such as granules by means of a feed screw 14 'and a conveyor element 14 "a Rückmischsilo 16 which from where the accept and the final product is discharged 17th The will return mixed product by means of metering screws 18 to the mixer 19 supplied with fresh material or slurry from a reservoir container 20 mixed. The mixer may, as shown here from a Conveying zone 19 'and an actual mixing zone 19 "exist and leads the mixed 3 Well the distribution screw 6 to. The product dispensing of dried product from the dryer 1 is carried into the silo 16. The excess The final product is processed via the top of the silo 16 arranged discharge screw discharged 21 and then different Process steps, such as stacking the silo, packing in Big Bags, combustion or the like. Fed. This arrangement provides a particularly inexpensive and reliable variant is because the discharge amount regulates itself automatically. The more dried material obtained, the more material is discharged. Smaller in less good, so long as nothing is discharged to return to the level of the discharge is achieved 21st Thus it is also ensured that there is always enough material for remixing is available. If the volume is appropriately selected is sufficient even in a shutdown of the plant material for returning the tool available. Furthermore, also sufficient space should be to the Stopping the plant to completely empty the dryer. Further are the spray tubes 22 recognizable by means of which water condensation resp. Saturation of the vapors is sprayed. Fig. 3 shows a longitudinal view of the dryer 1 in which in the background the mixer 19 and the silos 16 and 20 are visible. In FIG. 4 is a cross view of a dryer according to the invention 1 to see. Here you can see also the Nassgutsilo 20 and the mixer 19 and the air supply pipe 7, including heat exchanger 8 and burner 15th Furthermore, the drying hood 23 above the belt 2 is in this view recognize.