Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L9/00—Treating solid fuels to improve their combustion
  • C10L9/10—Treating solid fuels to improve their combustion by using additives

Definitions

• the invention relates to a method for feeding coal filter sludge for combustion in a fluidized bed reactor and its application to the feeding of coal filter sludge into the circulating fluidized bed.
• the fluidized bed in particular the circulating fluidized bed, is in turn suitable for the combustion of inferior fuels.
• the prerequisite is that the fuel can be introduced into the swirl combustion chamber in a suitable form.
• the task of carbon filter sludges presents considerable difficulties in that they occur in clods up to 0.25 m2 in size and approximately 30 mm thick with thixotropic and sticky properties and are therefore difficult to handle.
• the object of the invention is to provide a method which does not have the known disadvantages, in particular the aforementioned disadvantages, and which allows carbon filter sludge to be introduced into a fluidized bed reactor in a simple, economical and reliable manner.
• the object is achieved by designing the method of the type mentioned at the outset in accordance with the invention in such a way that carbon filter sludge is mixed with fine-grained sorbent for SO x and / or fine-grained moisture-absorbing material in such a way that 20 to 40% by weight of the added carbon filter sludge with a particle size of 5 to 30 mm are distributed in the mixture and the resulting free-flowing product gives up the fluidized bed reactor.
• the mixing of carbon filter sludge with sorbent for SO x and / or moisture-absorbing material can be done in two separately working mixers.
• 60 to 80% by weight of the carbon filter sludge can be premixed to produce a largely homogeneous mixture in a mixing system equipped with knives.
• the filter sludge clumps are broken up by the knives, which rotate at about 1500 to 3000 rpm, and are distributed essentially uniformly.
• the remaining 40 to 20% by weight of the carbon filter sludge are then incorporated in such a way that sludge particles of 5 to 30 mm remain.
• This treatment process also requires mixers that can break up large chunks of filter sludge or clods of filter sludge.
• the particle formed by the separation process from the filter sludge has to be coated with the sorbent and / or moisture-absorbing substance, so that a recombination of individual particles to larger filter sludge agglomerates is prevented.
• Correctly dimensioning the treatment courses in time allows a largely homogeneous mixture to be achieved in the first stage and the required distribution with particle sizes of 5 to 30 mm in the second stage.
• a horizontal cylindrical share or blade mixer with a horizontal axis is suitable for this purpose, which has an additional cutter head with a separate drive shaft.
• the horizontal shaft should rotate at approximately 120 to 200 rpm, the drive shaft of the cutter head at approximately 1500 to 3000 rpm.
• care must be taken to avoid overly extensive distribution or even homogeneous mixing of the entire coal filter sludge. A mixing time of around one minute can be sufficient.
• Limestone, calcium hydroxide and / or calcium oxide are particularly suitable as sorbents for SO x . Since limestone splits off carbon dioxide at the prevailing combustion temperatures and changes into calcium oxide, a preferred embodiment of the invention provides for the carbon filter sludge to be mixed with limestone as a sorbent for SO x .
• the moisture-absorbing substance can be of any type, provided that it has the property mentioned.
• wood flour or coal dust are suitable.
• a particularly advantageous embodiment of the invention consists in mixing the carbon filter sludge with a fluidized bed pocket.
• One advantage is, for example, that unconverted limestone or unconverted calcium oxide present in the fluidized bed pocket can be used for the sorption of SO x .
• fluidized-bed bag with proportions of calcium oxide and / or as a sorbent for SO x calcium oxide is used as the moisture-absorbing substance, the water of the carbon filter sludge is bound not only mechanically but also by chemical reaction.
• the components of the sorbent for SO x and / or moisture-absorbing material required for the production of the free-flowing product depend in particular on the type and, if applicable, the proportion of the sulfur content of the coal contained in the coal filter sludge. Almost exclusively moisture-absorbing material can be used to mix almost sulfur-free coal. As the sulfur content increases, the proportion of sorbent will generally increase.
• the sorbent supply is to be dimensioned such that the sulfur content of the coal can be bound. When determining the required amount of sorbent, the proportion of unreacted lime present in the fluidized bed pocket, for example, must be taken into account.
• sulfur oxide content of the flue gas is e.g. used for the extraction of sulfuric acid.
• the proportion of coal filter sludge is based on the latter Total quantity in the finished product - within the range of 70 to 50 wt .-% when using fluid bed bag alone and from 30 to 50% by weight of limits formed using limestone alone.
• a further preferred embodiment of the method according to the invention consists in using the amounts of sorbent and / or moisture-absorbing substance required for the production of the free-flowing product with a grain size of 50 to 300 ⁇ m, preferably with d p50 ⁇ 180 ⁇ m. With such a grain size, the ratio of particle surface to particle volume and the absorption capacity of moisture and of SO x formed during combustion are particularly favorable.
• the free-flowing product produced by the process according to the invention is suitable for transport, for example on belts, and for storage in silos. It can be abandoned with the usual mechanical devices.
• the heat losses of the incineration plant are reduced, particularly as a result of the water evaporation required. This means that the device dimensions can be reduced and the amount of flue gas generated is reduced by about 10 to 20% with the same output.
• the free-flowing product obtained in accordance with the method according to the invention is suitable for combustion processes which are carried out in the so-called classic fluidized bed.
• it is particularly advantageous as a feed material for combustion processes that take place in the circulating fluidized bed.
• Such processes for combustion in the circulating fluidized bed are, for example, in DE-C-2 539 546 (corresponding to US-A-4 165 717) DE-C-2 624 302 (corresponding to US-A-4 111 158) EP-A-0 206 066 (corresponding to US-A-4 716 856) EP-A-0 281 165 (corresponding to US-A-4 817 563) described.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Organic Chemistry (AREA)
• Fluidized-Bed Combustion And Resonant Combustion (AREA)
• Treating Waste Gases (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6390939

Family Applications (1)

Country Status (4)

Cited By (3)

Citations (3)

Family Cites Families (1)

• 1989
  • 1989-10-06 DE DE19893933374 patent/DE3933374A1/de active Granted
• 1990
  • 1990-09-26 EP EP90202544A patent/EP0423859A1/de not_active Withdrawn
  • 1990-10-03 CA CA 2026828 patent/CA2026828A1/en not_active Abandoned
  • 1990-10-05 AU AU63826/90A patent/AU6382690A/en not_active Abandoned

Patent Citations (3)

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