DD290438A5 - METHOD FOR RECOVERY OF COAL-STAIRED TARES FROM SOLIDS-CONTAINING TARIFF PREPARATIONS - Google Patents

Abstract

The invention relates to a process for the recovery of carbonaceous tars from dust / tar mixtures for the purpose of subsequent material use. The objective is to increase the economics of lignite carbonization and coking as well as lignite gasification by increasing the amount of karbochemical liquid products. The object of the invention is the recovery of coal tar by a pyrolysis preceded by a matched mixture of solid-containing tarrüberstaenden with the coal flow at Gewaehrleistung a sufficiently good mixing of the two components. According to the invention, the admixture of the dust / tar mixture to the coal stream takes place in two stages and metered. In a separate pre-mixing stage, the dust / tar mixture is mixed with an adjusted amount of coal to form a surface-dry, crumbly and meterable mixture. This is added to the briquetting zuflieszenden coal stream in such an amount that the recycled tars amount to a maximum of 2.5 * based on the total coal. The addition of the mixed material to the total carbon is carried out optionally or after the drying step. {Recovery; Tar, carbonaceous; Dust tar mixture; carbonization tar; admixture; Einsatzbrikett; pyrolysis; Method; two stages; Mixed, surface-dry, crumpled}

Description

For this 1 page drawings

Field of application of the invention

The invention relates to a Verfahron for the recovery of coal-based tars (mainly smurfs) from dust-tar mixtures for the purpose of subsequent material use.

Characteristic of the known state of the art

Most of the known processes for lignite carbonization or coking as well as lignite gasification require the coal in briquetted form. The economic goal in the case of lignite smoldering is to produce the maximum amount of carbochemical liquid products from which paraffins, lubricants, electrode coke, fuels and other chemical recyclables can be obtained. In the context of o.g. As a result of the process, tar residues in the form of different dust tar mixtures are to a considerable extent accessible to the previously only energetic use or to corresponding landfills. In this case, the amount of tar contained in these waste products in the order of 50 to 80Ma .-% is withdrawn, despite its significant proportion, its actual intended use and thus affects the economic outcome of the pyrolysis process. Attempts to recover the tar components in question by recycling the liquid residues in the hot state in the pyrolysis process so far failed. Thus, GOEDICKE (Freiberger Forschungsheft A327 [1964] p.7 to 99) had to produce a very high loss of strength in the subsequent experiments in his attempts to recycle the dust-tar mixtures obtained as carbonized pulp and centrifuge residue in the smoldering process by admixture with the briquetting flow of dry coal Notice smoldering briquettes. This resulted in impermissibly high degrees of deficiency in the subsequent drying and pyrolysis process, which significantly hindered the actual carbonization process. The causes were obviously in an insufficient mixing of the two components. The derived technical solution proposed fine atomization of the liquid dust-tar mixture over a variety of special nozzles remained limited in its effect and found because of the unreal high number of nozzles and the problems of spraying high-solids media no practical application.

The known principles of liquid product recovery used in other carbochemical processes, such as flash distillation or separate devolatilization (as in the case of hot separation residue in high pressure hydrogenation

of fine coal) or the known possibilities of extraction (such as, for example, supercritical gas phase extraction) require additional and complicated process stages which, moreover, can generally not be classified in the technology scheme of a pressureless coal pyrolysis.

Object of the invention

The object of the invention is to increase the efficiency of existing lignite carbonization processes and lignite gasification by increasing the amount of carbochemical liquid products.

Explanation of the essence of the invention The object of the invention is the recovery of kohlestämmiger tars by a Pyrolysoprozeß

upstream, coordinated mixture of solids-containing tar residues with the coal flow while ensuring a sufficiently good mixing of the two mixing components.

Using lignite and dust-tar mixtures, the following relationship between the Concentration of free tar and the strength of the pyrolysis briquettes essential for the subsequent pyrolysis process

found:

Teer concentration ·) (% by mass) 0.6 0.9 1.2 1.5 1.8 2.1 2.1 Compressive strength (MPa) 11.2 12.0 12.3 11.9 11.0 9 , 8 8,3

·) ... related to anhydrous conditions

At compressive strengths below 10 MPa progressively increasingly observed the process-disturbing decay phenomena of Pyrolysis briquettes in the subsequent process steps of drying and pyrolysis. Therefore, according to the invention, the guarantee of a uniform tar distribution in the narrow range below 2.5Ma .-%

(especially 1.2Ma .-%) essential for the usability of the pyrolysis briquettes.

So far, the procedures for tar recycling have been able to increase local concentrations via the o.g. Limit could not avoid and therefore had to fail. According to the invention, a uniform distribution of the low tar constituents in a comparatively large coal stream

made by the existing dust-tar mixture is first premixed in a separate device with a suitably selected amount of coal so that a crumbly surface-dry and thus well transportable and metered tar-containing mixed material is formed. Experience has shown, for example, that can be achieved by the following composition:

40% by weight of briquette

40% by weight Schwelertassenrückstand

20 mass% centrifuge residue

The tar content of this mixture is about 20% by mass. Instead of Brikettabriebes other operationally incurred coal qualities corresponding structure, such as dry coal, filter dusts u.a. be used. It is essential that these solid components have a sufficient sorption capacity with respect to the added tar portion and that the resulting mixed material is sufficiently well briquetted in admixture with the feed coal. Depending on the quality of such alternative solid components, the composition of the mixed material may change in this case. This separately prepared tar-containing mixed material is added to the total coal stream in a proportion that an average tar concentration of max. 2.5Ma .-% (especially about 1.2Ma .-%), based on anhydrous ratios results. The admixture of the tar-containing mixed material can be done in different ways.

According to variant 1, the addition of the mixed material to the uncut or pre-shredded raw coal takes place before the drying process stage. In addition to the intimate mechanical mixing of coal stream and mixed material while passing through the comminuting and drying devices, according to the invention, the temperature influence in the drying step achieves additional concentration equalization by transfer of viscosity-reduced tar fractions in particle-to-particle grain boundary regions. The drying temperature should be limited to values which preclude a thermally induced release of tar. Experience has shown that such leakage of tar vapor at temperatures below 170 ° C is excluded. The grain size of the metered mixture containing tar is irrelevant in this form of admixture because of the subsequent common comminution and should be limited only to the grain size of the actual coal stream at the point of admixture. By applying this procedure according to the invention, the briquette strength could be increased from 12.3 to a maximum of 17.2 MPa compared with a simple mechanical admixture of the mixed material as a consequence of the described thermal effect.

In addition to the described form of adding the mixed material, the metered addition may also be added to the stream of dry coal, i. between the drying process steps and the drying of dry coal (variant 2). To ensure the inventively named thermally induced concentration compensation by Teerübertritte in the field of direct grain contacts, the addition is carried out in the drying after drying still hot Trockenkohlestrom, d. H. even before possibly existing Kühlkettenfördororn or other cooling devices. In any case, it must be ensured that the mixture of total carbon and mixed material passes through a mechanical mixing process at temperatures of at least 60 ° C. The grain size of the supplied mixture should in the FaI! Variant 2, which do not exceed the Trockenkohlestromes at the point of admixture.

In addition to the admixture of operationally incurred dust / tar mixtures and the addition of other tars (or pitches) or solid / tar mixtures is possible.

Exemplary embodiments

The details of the process according to the invention will be explained in more detail for two variants with reference to the flow diagrams shown in FIGS. 1 and 2. The flowcharts show only the essential parts of the process to explain the process.

Process Variant 1: Dosing of the Mixture for Raw Lignite (see Figure 1)

The raw lignite coal required for the production of the smolder briquettes is initially stacked in the raw coal high bunker (1) before being processed further, and conveyed from the latter by means of bunker discharge carriages (8) onto the discharge belt. The raw coal bunkers are divided into bunker ships and bunker bags. In one or more bunker pockets now only the separately generated tar-containing mixed material is retracted. The discharge is metered by a Bunkeraustragswagen (8), wherein the mixed material is applied to the raw lignite. The operation of the two bunker emptying cars is coupled by electrical interlocks. In large-scale bunkers in which the separation is missing in individual bunker pockets, if necessary, a corresponding partition wall is installed. Instead of the above-mentioned use of existing bunkers also the establishment of a corresponding stacking container (5) for the mixed fuel is possible, with the supply and discharge of metered via a suitable discharge system to be taken mixed material and its allocation to the raw coal stream via conveyor belts or similar transport technologies. The addition of mixed material to the raw lignite is a maximum of about 7Ma .-% (based on dry coal). The raw lignite goes through with the tar-containing mixed material existing in the briquette factories and known operating sections of the

- Raw coal preparation (2)

- Drying (3) and dry coal treatment (4)

- pressing,

wherein in particular in the raw coal preparation (2), the drying (3) and the drying coal treatment (4) an intimate mixture and homogenization of the two components lignite and mixed material is achieved. After pressing the mixture, the briquettes are conveyed as usual to the smoldering plant. The process outlined above allows a material use of the tar contained in the mixed fuel without additional technical effort, and the previous facilities for tar cleaning no change must be subjected. Process Variant 2: Dosing of the Mixture for Briquetting Drying Carbon (see Figure 2) In this process variant, the mixture is mixed in proportions of max. about 7% by weight of the briquetted dry coal (based on dry coal) before the operating section added dry coal treatment.

For this purpose, the finished mixed material in bunkers (5) is stacked, from these with suitable discharge devices, such. B. turntable, feeder or roller feeder metered discharged, transported by means of a delivery unit (conveyor belt, trough chain conveyor) in the operating section dry coal treatment (4) and added to the briquetting dry coal. However, it must be ensured that on the way to the operating section pressing an intimate mixture and homogenization of Brikettiertrockenkohle and mixed material takes place in the downstream systems of dry coal treatment. This is achieved by adding the mixture to the briquetting dry coal stream as close as possible to the dryer outlet. Di? Coal temperature here is about 70 ⁰ C. Thus, the inventively named concentration compensation between the teilerbenetzten grain fractions and the dry grain of Brikettierkohle is achieved. If required, a mixing unit (eg mixing screw) can additionally be installed in the area of dry coal treatment.

The mixture is then further processed according to process variant 1, i. fed to the operating section pressing, wherein subsequently the finished briquettes are transported to the carbonization plant.

Claims (6)

1. A process for recovering coal-based tars, especially smoldering, from dust-tar mixtures, the operationally incurred in processes of coal pyrolysis with briquette, by mixing these dust-tar mixtures to the briquettes for the pyrolysis process, characterized in that the admixture the dust-tar mixture to the Brikettierung flowing Kohlostrom two-stage and dosed so that the dust-tar mixture in a separate pre-mixing with coal (in the form of Brikettabrieb, fine coal, filter dust, etc.) is premixed so that a surface-dry, crumbly and meterable mixed material is produced, which is subsequently added to the briquetting flow of coal in a second stage in such an amount that the recycled tar fraction based on the total calculated anhydrous total carbon is 2.5Ma .-%, wherein the addition of the mixture to the total coal to take place that the mixture of total carbon u Mixed material jointly passes through a mechanical mixing process at temperatures of at least 60 ⁰ C, and that finally the thus prepared mixture of total carbon and mixed material is subsequently pressed in a conventional Brikettierstufe to pyrolysis briquettes. 2. The method according to claim 1, characterized in that the recycled tar fraction _f based on the anhydrous calculated total carbon / nsbesondere 1.2Ma .-%. 3. The method according to claim 1 and 2, characterized in that the addition of the mixed material to the total carbon takes place before the drying stage in the uncrushed or pre-crushed raw coal. 4. The method according to claim 1 and 2, characterized in that the addition of the mixed material to the total coal after the drying step in the still hot Brikettiertrockenkohle so that the mixture of total carbon and mixed material passes through a mechanical mixing process at temperatures of at least 60 ⁰ C. 5. The method according to claim 1 to 4, characterized in that the grain size of the mixed material is limited to a maximum of that of the total coal stream at the point of admixture. 6. The method according to claim 1 to 5, characterized in that instead of the operationally incurred dust-tar mixtures and other tars or pitches or solid-tar mixtures can be used elsewhere.