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Contenu archivé le 2022-12-27

CONSTRUCTION AND OPERATION OF A BROWN COAL DRYING PLANT ACCORDING TO THE WTA PROCESS

Objectif

Construction of a brown coal drying plant according to the WTA process (fluidized bed drying with internal waste heat utilization)
The main characteristics of the WTA process are :
- Drying of brown coal in a steam fluidized bed;
- Use of the steam obtained from brown coal by application of the heat pump principle;
- Two stage supply of the energy required for drying.
Innovative aspects : New drying process. Recovery of all waste heat. Two energy utilisation stages.
Within some 4000 operating hours until the end of August 93 the test operation and the guarantee test runs were successfully completed. Operation of the individual components - except the raw coal preheaters and the overall plant has demonstrated the fundamental operational viability of the WTA process and has shown that the demonstration plant can be reliably controlled both in terms of production and safety. Compared with the reference process the emissions from the WTA are only 10% of those from the rotary tube drier and the energy savings without preheaters are 42.5% related to the rotary tube drier. The expected energy savings for the WTA process with preheater are some 53%.
The demonstration plant will have a capacity of 20t/h of product (12% moisture dried brown coal), which corresponds to 44t/h of feedstock (60% moisture raw brown coal). First, the raw brown coal should be preheated in a coal preheater. But the WTA-demonstration plant was mainly operated without raw coal preheaters, because the operational behaviour of this component was not satisfactory. Therefore, it was decided to develop a new type of preheater within the scope of a follow-up project.
After passing the preheaters the raw brown coal is subsequently fed to a continuously operating fluidized-bed drier.
The major part of the energy required for drying is supplied by heat exchangers insalled in the fluidized-bed drier. The dried brown coal is continuously discharged from the drier bottom at approx. 110 deg. C and then cooled to approx. 60 deg. C in a cooler.
During the drying process, 24t/h of dust-laden steam is discharged at the top. In an electrostatic precipitator, 99.98% of thecoal dust is separated and recirculated to the product flow. The cleaned, almost dust free steam is partly supplied to a circulation blower to serve as a fluidizing medium in the fluidized bed and partly fed to the steam turbo-compressor which has the function of a heat pump. The recompressed steam (4-5 bar) leaving the compressor is then conveyed to the drier heat exchangers where it releases its heat while condensing.
After having passed through the flash chamber, the steam condensate is partly supplied to an injection pump for direct cooling of the recompressed steam and partly fed to the coal preheater to preheat the brown coal. In the final cooler, the condensate (approx. 24 m3/h) leaving the preheater is cooled to a temperature of approx. 30 deg. C.
The WTA process takes place in an inert steam atmosphere and produces almost no emissions. Except for the start-up operation, no external steam supply is necessary to meet the energy requirements.

Appel à propositions

Data not available

Régime de financement

DEM - Demonstration contracts

Coordinateur

Rheinbraun AG
Contribution de l’UE
Aucune donnée
Adresse
Stüttgenweg 2
50935 Köln
Allemagne

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Coût total
Aucune donnée