DE4104873A1 - Gas purifier moulding compsn. prodn. for dry removal of hydrogen sulphide - comprises mill drying, classifying and granulating ferric hydroxide slurry from water works - Google Patents

Abstract

Prodn. of gas purifier moulding compsn. for dry sepn. of H2S from gas mixts., esp. from biogases, is carried out by milling drying a slurry contg. Fe(OH)3 from water works, with internal classification, then mixing with binder and granulation. The mill drying-classification stage is carried out in a heated hammer mill (with twin rotors) or pug mill, pref. in a single stage. The fine prod. has a d80 particle size not exceeding 0.3 mm and max. moisture content of 12% and is free-running. It is mixed with 3-8 wt.% binder, pref. in a trough mixer, and granulated on a pelletising disc with a min. dia. of 1.6 m, speed of rotation of 0.70-0.78 n crit and disc angle of 48-52 deg. USE/ADVANTAGE - The compsn. is useful for purifying small and medium amts. of gas esp. CH4-rich biogas from anaerobic fermentation of communal, industrial and agricultural sewage or slurry, which is used in energy generation; and for purifying all fuel and gases (both useful and waste) contg. H2S from the energy and chemical industries which are generated under low pressure. It consists of a sec. raw material and satisfies the requirements for H2S absorption capacity and activity and mechanical and flow properti

Description

The invention relates to a process for the preparation of Gasreinigerformmassen in which as the starting material Fe (OH) ₃haltiger Waterworks sludge is used. These gas cleaner molding compounds find for the dry separation of hydrogen sulfide from gas mixtures of small and medium quantities Application, in particular from methane-rich biogases, in the anaerobic fermentation of municipal, industrial and agricultural sewage or sludge and an energetic use.

In addition, all can accumulate under low pressure hydrogen sulfide-containing mixtures, fuel and useful gases and waste gases from the energy and chemical industries be cleaned with this gas cleaning compound.

It is known to remove hydrogen sulfide from gases, by passing this through gas cleaning mass, consisting of iron oxides or hydroxides mixed with loosening agents, be directed. The cleaning mass binds the hydrogen sulfide chemically as iron sulfide and is with air or Oxygen, which is proportional to the amount of raw gas and H₂S content is mixed, regenerable, with iron oxide and form elemental sulfur, which in the pores of the Mass is stored. The mass can be used as long until the progressive enrichment of sulfur whose revival no longer permits. As active masses serve lawn iron ore, Lux and waterworks masses. It is furthermore been proposed as a desulfurizing mass use mechanically or thermally activated gravel burns (DD-PS 21 712, DD-PS 29 361 and DD-PS 35 940).

Compared to the known embodiment of the method, this Gas purifying masses in loose bulk on hordes in To arrange flat or tower cleaners, it is advantageous use shaped gas cleaning masses in the moving bed (DE-PSD 8 25 871).

A known technical solution of this kind is the "gas technology process" (see, for example, GB-PS 4 33 823 and GB-PS 6 83 432 and DE-PS 11 40 662). In this process, the desulfurization takes place in one or more cascaded built-in towers, with the granulated cleaning mass are filled. By continuous withdrawal of used  Mass and recovery of an equivalent part Regenerated or fresh mass becomes a counter to the gas flow Generates granulate circulation that is variable and the gas-side load of the plant can be adjusted. The use of a molded feedstock and the Circulation principle avoid the disadvantages of the tray cleaning method, by favorable kinetic and fluidic Conditions a high specific gas throughput with continuous operation and a high degree of mechanization is reached. The movement of the ground bed avoids its hardening and thus the horde cleaning process typical and very significant work problems at the discharge of the consumed mass. The apparatus dimensions and thus the construction and investment costs are reduced considerably.

For shaping the cleaning mass are methods of pelleting and / or sintering with the addition of binders and possibly pore-forming agents have been proposed (see, for example GB-PS 4 06 495 and GP-PS 4 00 387). It is also known that by Pelleting of mechanically and / or thermally activated Kiesabbränden with cement additive as a binder in the technical Scale granules can be produced, which is the mechanical and fluidic requirements of desulfurization in tower cleaning systems corresponds. The special application activated gravel burns is procedural very expensive and thus economically ineffective.

The invention is therefore the object of a method to develop in which by certain processing technology Processes from suitable secondary raw materials, one molded cleaning masse, which is sufficient in Absorbance and activity against hydrogen sulphide the mechanical and fluidic requirements of the Use in a gas purification system, eg. B. a tower circulation desulphurisation plant, equivalent.

In particular, the sorption mass must meet the following requirements fulfill:

Grain size composition: 5. , , 20 mm
Compressive strength: <100 N
Porosity: <50%
Absorption capacity for H₂S: <20% by mass

This object is achieved in that a special conditioning technology has been developed that out a combination of crushing, classifying, mixing and agglomeration-technical processes and the following process steps includes:

• - Impact drying with internal classification
• - Mixing process in tray mixers
• - Shaping by build-up granulation

As a suitable secondary raw material was high-moisture Fe (OH) ₃-containing Wasserwerksschlamm (Fe (OH) ₃ content: at least 80%; Discharge moisture between 30. , , 50%, upper grain size of the Feed material / filter cake: <30 mm) found in one Grind drying classifier with impact beater and inner classification is processed. This creates a mechanically discharged coarse material and one with the hot gas discharged, classified fines content with the for the Pelleting at least required fineness of 80% by mass < 300 μm.

The Sichterfeingut will improve the strength of the Shaped body with a solid or liquid binder, according to a preferred embodiment of the invention, with cement, intense mixed. The optimum binder content is about 3. , , 8% by mass, preferably 5% by mass. Be as mixing units continuous trough mixer used.

The mixed classifier cake is used to produce moldings subjected to an agglomeration process. According to the invention this is done by build-up granulation on a pelletizing plate achieved because of the capillary action of liquids based pelleting is particularly good for the production of Moldings with high porosity is suitable. To achieve a high pellet strength are pelletizing discs with a diameter 1.6 m.

For the Aufbaugranulierung on Pelletiertellern plays the during the agglomeration added amount of water a process-determining Role. In the case of the invention is the specific water addition 0.25-0.35 l / kg, preferably 0.3 l / kg Solid.

The pelleting process proceeds under the conditions underlying the invention particularly favorable at a plate speed of n = 0.72. , , 0.78 n _crit , preferably 0.75 n _crit , and a pitch angle of 48. , , 52 °, preferably 50 °, from.

Under the conditions described moldings are produced, in terms of their material and physical Properties meet the requirements of an effective sorption mass for dry gas desulphurisation, to a high degree. By the invention Application of developed technology is the secondary raw material Waterworks mass as a sorption mass in the first place Can be used tower circulation method. Of particular advantage is that thus a qualitatively compared to previously used raw materials better and constantly available sorption mass provided can be.

The invention will be explained in more detail by way of example become.

The technology for dry treatment of the high-moisture water sludge shows at an hourly throughput of 120 to 200 kg, the technological process scheme, Fig. 1.

The single-rotor impact dryer 300 × 100 mm, combined with a blindsetter operating in the inner cycle, worked on the following test conditions:

Feed grain size | 0. , , 30 mm feed moisture  35% Rotor peripheral speed 60 m / s gap width 2 mm Total air volume 650 m³ / h Hot gas temperature at the crusher inlet 700 ° C Venetian blind position on the sifter steep

The following mill-drying results were achieved:

throughput 160 kg / h Mechanical discharge ~ 1% fine material ~99% Mass fraction <0.315 mm in the fine material 15. , , 20% Mass fraction <0.063 mm in the fine material 12% Final moisture fines  10% Temperature at the baffle dryer outlet 170 ° C Impact loading factor 0.25 kg / m³

The ground-dried water sludge with a d₈₀ grain size of 0.3 mm and a humidity of around 10% was in one Double-shaft trough mixer with 5 mass% cement PZ 7/35 approx. 30 min mixed intensively. The waterworks mass-cement mixture was then placed on a pelletizer with a diameter of 1.6 m of a built-up granulation. The Pelletizing plate worked with the following parameters:

Sheet inclination: 50 °
Plate speed: 22 min ^-1
spec. Water addition: 0.3 l / kg

The moldings produced in this way have the following Properties on:

Pellet size composition: 5. , , 16 mm
d₅₀ pellet size ~ 9.2 mm
Compressive strength: 135 N
Bulk density: 1.32 g / cc
Pure density: 2.95 g / cm³
Porosity: 55%
Humidity: 13.6%

Explanation of the reference numbers

1, 4 task or intermediate bunker
2 baffles with internal classification
3 cyclone separator
5 trough mixer
6 pelletizing plates
7 pellets

Claims (9)

1. A process for the preparation of gas cleaning molding compounds for the dry separation of hydrogen sulphide from gas mixtures, in particular from biogases, in which Fe (OH) ₃-containing Wasserwerksschlämme a Mahltrocknung with inner Classification, followed by mixing with Binder and a final build-up granulation be subjected. 2. The method of claim 1, wherein the Mahltrocknungs-Klassierstufe as impingement drying in heated impact mills with internal classification. 3. The method of claim 1, wherein the Mahltrocknungs- and Classification stage in heated racket mills with inner Classification is performed. 4. The method of claim 1, which only with a single-stage Mahltrocknungs- and Klassierstufe is executed. 5. The method of claim 1, wherein the fines discharge of Grind-drying with internal classification a d₈₀ grain size of 0.3 mm and a maximum Moisture content of 12% has. 6. The method of claim 1, wherein the from the mill drying discharged, fine-grained, free-flowing water mass mixed with 3-8% by weight of binder. Occurs 7. The method of claim 1, wherein the build-up granulation in a pelletizing pan with a minimum diameter of 1.6 m, a speed of 0.70-0.78 n _crit and a disc tilt of 48 to 52 °. 8. The method of claim 1, wherein the mixing process in a trough mixer takes place. 9. The method of claim 1 and 2 wherein the baffle dryer doppelrotorig is executed.