DD241461A1 - METHOD FOR DRYING SLABS - Google Patents

Abstract

The invention relates to a process for drying in particular fossil solid fuels. The aim is to achieve an optimal energetic use of the dry material. According to the invention, the object is achieved by diverting a partial flow from the exhaust gas duct of a heat generator and passing it via a convection dryer to which the fuel to be dried is fed. The partial flow with the dust or abrasion entrained from the dryer is blown into the steam generator via an induced draft and flame arrester. This creates a closed drying gas cycle.

Description

Characteristic of the known technical solutions

For the drying of bulk materials, a variety of methods and devices are known, which have in common that the dry material is introduced continuously or discontinuously into the dryer, the dryer with a heat flow to cover the drying heat input directly or indirectly charged and the resulting vapors together with spent drying agent or drying air are discharged into the atmosphere. The vapors are loaded with more or less large amounts of dust, which may be contained in the dry material or produced by abrasion in the dryer and the durcfi with a certain speed flowing through the dryer desiccant, drying air and vapor is entrained.

In general, therefore, the spent drying agent, drying air and vapors must be dedusted in complex facilities, the resulting dust is often an undesirable by-product.

The heat required for drying is generated in upstream steam or hot water generators or in hot gas systems. For this purpose, a considerable investment in equipment is also required.

In the construction and operation of these systems for generating the heat of drying and dedusting as well as in the delivery of even after passing dust removal systems with residual dust laden gas / vapor mixtures to the atmosphere, a disadvantage of the known prior art is seen, which can be solved ,

The drying systems described variously in the literature, in which waste heat from other plants, eg. B.

hot air or flue gas to be used as a drying agent, solve the identified technical disadvantage only partially.

Object of the invention

The aim of the invention is to develop a rational process for drying in particular raw lignite, which enables optimal energetic utilization of the dry material.

Explanation of the essence of the invention

The invention has for its object to dry using the flue gases of a heat generator in particular raw lignite and to use the energy generated during drying abrasion and dust. This is done according to the invention so that from the exhaust duct of a steam generator, a partial flow of the flue gas at a temperature level of about 200 ° C-300 ° C are introduced into a convection dryer via a downstream induced draft and the dryer at the same time the lumpy coal to be dried is abandoned. The resulting flue gas-vapor mixture, leaving the dryer at a temperature of 100 ⁰ C, is fed through the induced draft to the furnace. The gas velocity in the dryer is such that the coal dust contained in the bulk material and the inevitable resulting from the material movement in the dryer abrasion with the flue gas vapor stream is discharged, which is for further use of the dry coal of great advantage and the inventive solution consciously aspired to. In the firebox of the steam generator, the coal dust is burned. By this circuit, a self-contained drying gas cycle is built up over the steam generator, whereby a separation of the entrained coal dust can be omitted in dedusting.

At the indicated temperature level of the flue gases for drying a brown coal of 55% to 35% water content for the evaporation of 1 kg of water a flue gas amount of 12 to 15m ³ iN required. In the dryer, this volume is increased to 14-18m ³ iN / kg of evaporated water due to unavoidable false air infiltration and the amount of vapor resulting from water evaporation.

As at the same time about 2.3 kg of dry coal per kg evaporated water and about 10% of this dry coal are discharged as dust, there is a specific dust load of the steam generator-supplied flue gas-vapor mixture of about 16g / m ³ iN This amount of dust gives During combustion, an amount of heat of about 80 kcal, which contribute to the reheating of the flue gas and the additional supplied vapor and false air.

When dimensioning the drying system, make sure that the additional amount of gas supplied to the steam generator, consisting of recirculated flue gas, vapors and secondary air, is no greater than 10-15% of the amount of flue gas produced in the main furnace.

-2- Ζ4Ί 461 embodiment

The combustion chamber 2 of the steam or. Hot water generator fuel and combustion air 1 is supplied. The flue gases pass through the Nachschaltheizflächen 3 to the flue gas channel 4 and are discharged with the suction 5 to the chimney 6.

The partial gas stream required for drying passes via the channel 7 to the convection dryer 9. At the same time, moist raw brown coal 8 is fed to the convection dryer. The dried Rohbraunsiebkohle 10 is discharged after the continuous drying process from the convection dryer.

The resulting in the convection dryer flue gas-vapor mixture, which contains the desired proportion of dust and abrasion, is fed by means of induced draft 11 via the flame arrester 12 of a Einblasevorrichtung 13.

Claims (1)

A process for drying bulk materials, in particular solid fossil fuels, characterized in that a partial flow diverted from the Abgankanai a heat generator, passed through a convection dryer, the fuel to be dried is fed at a certain speed and the partial flow with the from the dryer entrained dust or abrasion is injected via a suction and flame arrester in the heat generator. For this 1 page drawing Field of application of the invention The invention relates to a process for drying bulk materials, in particular fossil solid fuels.