Method for producing basic products from ash, in particular paper ash

Abstract

A method for producing basic products from ash, which includes the provision of a starting material in particle form, crushing the particles of the starting material by high-frequency pressure impulses and the in situ separation of at least two fractions with different average particle sizes, where the energy-efficient production of a basic product with a defined particle size and high reactivity is effected, such that the produced basic products can be used directly for further product production, e.g. as alkalizing agent, for ground stabilization or as filler.

Claims

1. A method for producing basic products from ash, comprising the following steps: i. providing a device structured to crush and to separate particles of a starting material; ii. providing ash as starting material in particle form; iii. crushing the particles of the starting material by pressure waves; and iv. directly subsequent to the crushing, separating the crushed particles into at least two fractions with different average particle sizes so that there is no procedural gap between the crushing of the particles and the separation and so that the crushing and the separating of the crushed particles occur in the same device, wherein the step of crushing the particles of the starting material by pressure waves is carried out using a high frequency pressure impulse (HFPI) crusher, and wherein the high frequency pressure impulse (HFPI) crusher is a HFPI crusher with in situ separator.

2. The method according to claim 1, wherein the crushing is carried out in a dry state in air or in an air/gas mixture, wherein an airflow generated in the particle crushing is used in situ to separate the fine particles in a subsequent separation in a cyclone.

3. The method according to claim 1, wherein the produced basic product has an average particle size of 0.1 to 100 m.

4. The method according to claim 1, wherein at least one of the two fractions of the basic product is directly used as product for ground stabilization as soda lye substitute, as adsorption agent and/or as filler.

5. The method according to claim 1, in which due to the separation in step (iii) at least a first fraction with an average particle size in the range from 0.1 to 8 m and a second fraction with an average particle size in the range from 8 to 100 m result.

6. The method according to claim 5, in which each individual fraction is independently further used directly as basic product and/or is subjected to a further process.

7. The method according to claim 6, in which the further process comprises a further modification of the particle size.

8. The method according to claim 1, in which one or more solid, liquid or gaseous additives are added before, during or after the crushing of the particles of the starting material (step (iii)) and/or before, during or after the separation of the fractions (step (iv)).

9. The method according to claim 8, in which one or more carbon dioxide containing gases and/or concentrated carbon dioxide containing gases are used as additives.

10. The method of claim 1, wherein for an in situ separation of particles crushed in a wet manner, gravity separators are used which make use of centrifugal or gravitational forces.

11. The method of claim 1, wherein the ash is paper ash.

12. The method of claim 1, wherein the high frequency pressure impulse (HFPI) crusher is operated at a frequency greater than 8 kHz.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a test set-up of a plant for carrying out the method according to the invention.

(2) FIG. 2 schematically shows possible workflows of the method according to the invention for the production of basic products.

EMBODIMENT EXAMPLES

Ash

(3) The ash, on which the following examples are based, is obtained in a 56 MW thermal power station with a fluidized-bed boiler by incineration of fiber residues (fibers yielded as loss in the waste paper recycling system) as well as waste wood and sawdust. Furthermore, removed color particles and sorted-out synthetic materials from the waste paper are contained in the material to be incinerated. The ash essentially consists of approximately 48% CaO (free lime content approximately 8%), 5% MgO, 14% Al.sub.2O.sub.3, 1% Na.sub.2O, 0.2% K.sub.2O, 35% SiO.sub.2 and the typical minor components of ash.

Example of the Method According to the Invention

(4) The starting material ash is supplied from a silo (1) as starting material for temperature setting in an ash cooler. The ash is circulated with a blower in the ash cooler (2) and, if necessary, the temperature is reduced from approximately 140 C. to 70 C. by means of cooling water. The thus whirled up and cooled ash is supplied via a rotary feeder into the tube chain conveyor (5). The exhaust air is purified of finest particles via a reverse flow cartridge filter (3). The finest particles are supplied to the finest fraction (8), which is downstream of the crushing, via a valve.

(5) The supply to the HFPI crusher (6) is carried out consistently via chain conveyor (5). The entire system is closed, pressure variations are compensated by a filter element at this point.

(6) The crushing in the HFPI crusher (6) is carried out by means of counterrotating rotors with specific internals adapted according to the required basic or end product in an air atmosphere under high airflow.

(7) The ash crushed in a non-contact manner is separated in a subsequent step into a fine fraction (8) (Cinerit) and a finest fraction (9) (Elurit) without a procedural gap, i.e. in situ. The separation into fine fraction and finest fraction is carried out via a cyclone. In the finest fraction (9), there is an air recycling (7) to the HFPI crusher. In the recirculation line, a further filter element is located which can be optionally connected to the existing exhaust air filter system and serves for pressure compensation.

(8) Ash, which corresponds to the properties of the fine fraction and is yielded in a filter (3) during ash cooling, can optionally be directly supplied to the Cinerit container (8). Subsequent to the above-described process, it is possible to supply the separated fractions to a silo (12) via an ash dispenser (10) and (11) and store these temporarily for further use. There is also the option to fill the fine fraction (Cinerit) and the finest fraction (Elurit) in separate silos (13) or (14) (Cinerit/Elurit). For recycling in industrial processes, ash eluates can be produced with the individual fine and finest fractions in that the particles are suspended with water and dispersed in a dissolution plant.

Example 1

(9) Ash Recycling According to the Method According to the Invention

(10) Recycling the ash according to the above-described example of the method according to the invention.

Comparative Example 1

(11) Ash Recycling According to Conventional Methods

(12) Recycling the ash according to the conventional wet milling of coarse boiler ash or Ca(OH).sub.2 by means of a wet ball mill or disk (vibration) mill (MW 2 m particle size).

(13) Comparison of the Required Energy

(14) The energy required to crush 1 ton of ash according to Example 1 and according to Comparative Example 1 is given in Table 1.

(15) TABLE-US-00001 TABLE 1 Required Energy (90% < 2 m) kWh/t Ash Example 1 10 Comparative Example 1 100
Properties of the Produced Basic Products

(16) The properties of the produced basic products were determined as follows:

(17) The degree of whiteness was determined after reaction of the product with air and the CO.sub.2 contained therein. The optical properties of the degree of whiteness R457 were determined by means of an L&W Elrepho/pulsed xenon lamp with D65 diffuse standard illuminant and 10 viewing.

(18) Determination of the specific surface (BET) of solids according to DIN 66132, according to BET method, DIN EN ISO 18757 (previously: DIN EN 725-6) with AREA-meter II (Strhlein Instruments) according to Haul and Dmbgen.

(19) Cation exchange capacity according to DIN 19684 Part 8.

(20) Acid capacity according to DIN 38409-7.

(21) Acid neutralization capacity according to the Directive LAGA EW 98 2002 [LAGA: Bund-Lnder-Arbeitsgemeinschaft Abfall=joint working group of Federation and States on waste; EW 98 relates to aqueous eluates]trough method.

(22) The properties of the basic products from Example 1 as compared to the basic product produced according to Comparative Example 1 are listed in Table 2.

(23) TABLE-US-00002 TABLE 2 Example 1 Fine Finest Comparative fraction fraction Example 1 BET [m2/g] 6.6 8.2 4.4 Cation exchange 2800 3100 2000 capacity [mmol/kg] Acid neutralization 21000 24000 16500 capacity [mmol/l] Acid capacity 42.2 44 36.6 [mmol/l] Degree of whiteness 72.5 72.5 70.1 D65/10 [%]

(24) It is apparent from Table 2 that due to the HFPI crushing starting from the starting material a significant increase of the specific surface and thus also an increase of the specific reactive surface is achieved, which is apparent here from the exchange capacity, the acid neutralization capacity, the acid capacity and the increased degree of whiteness.

Examples of Use

(25) Use of Ash as Soda Lye Substitute

(26) The eluate produced in Example 1 is subsequently suspended with water and dispersed in a dissolution plant. The eluate is used as an alkaline component produced according to the method according to the invention and can replace the use of soda lye e.g. in the paper and wood production.

(27) Use of Fine Particle Ash for Use in Ground Stabilization

(28) The prerequisite for the use of ash in ground stabilization is a defined degree of particle size, which can only be achieved with the method according to the invention, but not with conventional methods such as ball mills. The finest fraction (14) is used for this.

(29) In addition to the method described in Example 1, a mixing screw is used for manipulation for a binder adjusted to the respective ground material.

(30) The ash product according to the invention replaces burnt lime (CaO) here in ground stabilization, as a result of which it is possible to reduce the amount of energy required from conventionally 1250 kWh/t to only 20 kWh/t according to the invention.

(31) Use of Ash as Filler in Paper Production

(32) The ash according to the invention can be used directly as filler in paper production by direct substitution of chalk/kaolin or indirectly by substitution of burnt lime in PCC processes (precipitated calcium carbonate).

(33) Use of Ash in a Further Process

(34) The ash according to the invention is particularly suited for use in a further process, which comprises an in situ modification and, simultaneously, setting significantly lower sizes.