Process and device for drying solid materials in an indirectly h

Details Process and device for drying solid materials in an indirectly h Process and device for drying solid materials in an indirectly h

1993-03-18

1994-12-20

Gromada, Denise L.

Drying and gas or vapor contact with solids

Apparatus

With fluid current conveying of treated material

34 77, 34 79, 34363, 16510416, F26B 1700

Patent

active

053736486

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a process and a device for drying solid materials, such as, for example, brown coal, peat, sand, filter cakes from mechanical separation processes and sludges which contain less than 98% % by weight [sic] of an evaporable material, for example water, in which an indirectly heated fluidized bed is formed and contains solid material fluidized by a fluidizing medium, the fluidizing medium being the evaporable material in vapor form, and in which the dried material discharged from the fluidized-bed drier can be fed, if required after cooling, for further processing, utilization or disposal in a landfill, but the evaporated material can be fed to a purification, cooling, physical utilization and/or heat recovery stage and is suitable for use in industry, the building industry, agriculture and communal disposal.
2. Description of Related Art
Drying processes, in particular those which separate off water as an evaporable component from solid materials, are of considerable economic and social importance for industrial production, the building industry, energy conversion and disposal in communities and plants. In some cases, the drying is so much a matter of course and so integrated in the process sequences, as in the combustion of water-containing fuels, for example brown coal, and of sludges, that the environmental pollution caused by it through increased energy demand and increased emission are regarded as quite natural.
For the utilization of crude brown coal for energy, milling/drying plants are employed, particularly in power stations, said plants sucking back a part of the furnace gas, produced in the furnace, as a heat energy medium for the milling/drying, so that the water in the coal evaporates as a result of heat transfer by furnace gas at 800.degree. to 1000.degree. C. with crude brown coal in the stack gas stream, before or during milling of the coal to form pulverized fuel. The relevant prior art is described in detail in the book by Effenberger, H. "Dampferzeuger" [Steam generators], VEB Verlag fur Grundstoffindustrie, 1st Edition, 1987. Based on the heat energy liberated in the furnace of the boiler, this method of drying causes more than 1.5 times the minimum stack gas emission required on the basis of the laws of nature, owing to the high intrinsic fuel requirement of the drying and the proportion of steam in the stack gas.
In the brown coal enrichment, disk and tubular rotary driers indirectly heated with steam, i.e. contact driers, are predominantly used, as described in detail by Krug and Nauendorf in the book "Braunkohlenbrikettierung" [Briquetting of brown coal] Volume 1, section on Drying, VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig, 1984, 1st Edition.
By using steam from tapped turbines or back-pressure steam as a heat medium for the drying, which, through condensation, transfers its latent heat energy indirectly to the coal after it has been converted into saturated steam, for example by injection of condensate, the known principle of "Power/Heat coupling" is utilized and a reduction in the fuel requirement to be attributed to the drying is achieved. Compared with the milling/drying conventionally used in the brown coal power stations, it was therefore possible to reduce the comparable sum of the stack gas emission occurring during the individual enrichment and utilization sections to approximately 1.3 times the minimum required on the basis of the laws of nature. However, since "entrained air" is used in most cases, these advantages are not effective.
The introduction of indirectly heated disk and tubular rotary driers and hence the development of power/heat coupling, for example in brown coal and peat power stations, have been unsuccessful to date since the required fuel mass flows and the limited capacity of such driers are in contradiction with one another and have not permitted the object to be achieved in an economical manner.
East German Patent 67,770 discloses a process and a means for the pre

REFERENCES:
patent: 3790334 (1974-02-01), Cohen
patent: 3800427 (1974-04-01), Kemmetmueller
patent: 3861054 (1975-01-01), Stahl
patent: 4304049 (1981-12-01), Curtius
patent: 4563151 (1986-01-01), Vogel

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