GB2038309A

GB2038309A - Manufacture of brickmaking compositions

Info

Publication number: GB2038309A
Application number: GB7940966A
Authority: GB
Original assignee: Haendle & Soehne Maschf Karl
Current assignee: Haendle & Soehne Maschf Karl
Priority date: 1978-11-28
Filing date: 1979-11-27
Publication date: 1980-07-23
Also published as: FR2442806B3; FR2442806A1; IT7969292A0; DE2851412A1; IT1119538B; DE2851412B2

Abstract

In the manufacture of brickmaking compositions using coal mining waste material containing carbon and clay comminuted mine waste is separated into two portions. One is mixed with additives such as clay, brickearth, lime or the like and the other is heat treated to remove combustible constituents which are used to generate useful energy. The two portions are then mixed together again.

Description

SPECIFICATION Process and apparatus for the manufacture of brickmaking compositions The invention relates to a process for the manufacture of brickmaking compositions using waste material containing clay and carbon which is derived from the mining of coal, in which process the precomminuted mine waste is mixed with additives, such as clay, brick earth, lime or the like and is then plasticised.

Processes for the manufacture of bricks have already been developed, in which mine waste from the preparation of coal is thoroughly mixed with the customary clay raw materials, plasticised and moulded into shapes by means of extruders. In these processes, the mine waste serves as a so-called unenriched base material, and its content of combustible or gas-emitting substances reduces the thermal energy which has to be provided on baking. Furthermore, if the amount of the mine waste is appropriately matched - taking into account its combustible and/or gas-emitting constituents -to the amount of aluminous minerals employed, the porosity of the bricks can be controlled during baking.A further advantage achieved by the use of mine waste is that the mouldings used are heated more uniformly during the baking process, since the gases liberated in the interior of the raw moulding cause exothermic reactions. However, problems can arise if the combustible or gas-emitting constituents in the mine waste exceed a certain amount, since in that case the reactions which take place during the baking process are too intense and have an adverse effect on the quality of the bricks to be produced.

Further, a process for the manufacture of ceramic compositions from plastic freshly mined unburned clay and granular base materials is known (German Auslegeschrift 1,095,188), in which a particular proportion of the unburned clay is separated off and separately heated to temperatures of between 400 and 600 C. The remaining proportion of unburned clay is mixed with the granular base materials. In a subsequent process stage, the hot unburned clay portion is compounds with a mixture of original freshly mined unburned clay and granular base materials, with or without further specific additives.Heating the separated off portion of the unburned clay to the above mentioned temperature range is intended, by expelling the superficial water, the interstitial water and, in part, the chemically bonded water, to reduce the shrinkage of the mixture after it has been moulded by extrusion, and at the same time to achieve an advantageous effect through the strong hydraulic binder properties of the dried unburned clay component.

However, an advantageous effect on the energy balance or heat balance cannot be achieved with this known process.

It is an object of the invention to provide a process for the manufacture of ceramic compositions using carbon-containing solids, which process at the same time provides useful energy for the process sequence and allows the maximum influence to be exerted on the internal exothermic reactions on baking.

The present invention provides a process for the manufacture of brickmaking compositions using mine waste containing carbon and clay and derived from the preparation of coal, in which process comminuted mine waste is mixed with additives, such as clay, brick earth, lime or the like, and is then plasticised, characterised in that a predetermined portion of pre-comminuted solids is separated off, combustible constituents contained in the separated portion are burnt or gasified by heat treatment and used to generate useful energy, and the hot degassed solid portion is remixed with the thermally untreated solid portion, which has been mixed with the additives.

The heat treatment of the separated off portion of the solids can be carried out in a gas reactor, with the object of generating fuel gas, the fuel gases produced being converted to electrical energy. Alternatively, there is also the possibility of combusting the pre-comminuted solids, for example in a fluidised bed furnace, and of converting the liberated thermal energy into useful heat and/or electrical energy via a steam circuit. It is essential in this process that as a result of the heat treatment a variable amount of the solids employed has been inactivated, whilst at the ame time useful energy for the individual process stages is obtained.The percentage of solids to be separated off depends on the content of combustible substances in the solids, on their gasification properties, on the nature and amount of the additives and on the nature and properties of the ceramic compositions to be produced, and can be determined from case to case by means of simple experiments.

The process according to the invention is particularly suitable for the manufacture of brickmaking compositions, to serve as the starting material for bricks which are pressed in extruders, using a semi-rigid or rigid process. Where, in particular, the proportion of gasified or combusted solids is high, it is also possible to press the brickmaking compositions by the dry pressing process.

The invention also provides apparatus for carrying out the aforesaid method of the invention which apparatus comprises a first comminuter for carbon-containing solids, a proportioning device for separating a portion of the solids, a reactor for the continuous heat treatment of the portion of the solids which has been separated off, sizing means for hot material, mixing means for mixing the portion of solids which has not been heat-treated, and the additives, with the heat-treated portion of solids, and an extruder for the combined solids mixture.

The apparatus for the manufacture of brickmaking compositions, using carbon-containing solids, such as, for example, wash waste and flotation waste from the preparation of coal, oil shales, settling basin sludges or the like may contain, according to the invention, a pre-comminuter, which is preferably in the form of a beater bar unit, and which discharges into a proportioning device. This may be followed by a thermal reactor for the heat treatment of a proportion of the solids, and, parallel thereto, a mixer for the admixture of the additives, for example binder clay, to the other portion of the solids. In addition, a hot sizing means, if necessary with a cyclone, and a further mixer with a downstream plasticiserforthe mixture of heat-treated and non-treated solids and the additives is provided.These units are followed, for the purpose of manufacturing blocks and/or bricks from the plasticised ceramic compositions, by an extruder, a cross-cutting device and a kiln, which, where appropriate, is heated with the combustion gases and/or the gases which have been generated.

The text which follows describes, by way of example, an apparatus for the manufacture of brickmaking compositions in accordance with the invention, with reference to a schematic flow diagram.

Solids, which in this case comprise mine wastes B, pass, from bunkers or from a tip, via suitable conveying devices into a metal separator 1, in which, in particular, iron objects are removed. This metal separator 1 is followed by a pre-comminuter, which preferably consists of a beater-bar roll mill 2. The amount of pre-comminuted mine waste which the latter discharges is divided, for example by means of pan feeders, into two parts respectively accounting for, for example, 30 and 70% by weight, and in the illustrative embodiment the larger proportion of the mine waste is fed to a gas generator 3 or a combustion unit. In this gas generator a combined degassing and gasification of these substances takes place by external heating or by incomplete partial combustion of the combustible substances contained in the mine waste.The gas generated is combusted in a unit 4, which drives a generator to convert the energy, in a conventional manner, to electrical current. The hot combustion gases can also be led directly from the gas generator 3 into a kiln 13 and be combusted in the latter, as is indicated in the drawing by the line drawn in dashes separated by groups of three dots. If instead of the gas generator a combustion unit is employed, its hot emitted gases can, entirely or in part, be fed to a steam generator 4 or the kiln 13. Fluidised bed furnaces are particularly suitable as combustion units for such solids.

The degassed mine waste is transferred from the gas generator 3, via a discharge mechanism, into a fine comminuter 5, for example an impeller pulveriser, and is finely comminuted therein at as high a temperature as possible, for example 200"C. The material discharged from the fine comminuter 5, that is to say the degassed and comminuted mine waste, is passed, at a temperature of about 200"C into a mixer 7.

The other pre-comminuted portion of the mine waste, in the present illustrative embodiment 30% by weight, is intimately mixed, in a mixer 8, with binder clay, with or without further additives, and this mixture is also fed to the mixer 7, in which it is mixed with the hot, dry mine waste from the fine comminuter 5 and is at the same time heated. This substantially homogenous mixture of suitable particle size distribution enters, at an optimum intermediate temperature, the extruder 9, which is advantageously constructed as a vacuum unit. The extruded strand 10, which is at about 1 50 C, is divided by means of a conventional chopper 11, into raw mouldings, which are then used to charge a downstream kiln 13.

If an impeller pulveriser is employed as the fine comminuter 5, the air stream generated therein can be introduced, via the line 6 and a dust precipitator 14, into the gas generator 3, as a pre-heated oxygen carrier for incomplete combustion of the carbon constituent. Instead of using the gas generator 3, which is advantageously constructed as a fluidised bed unit, the combustible constituents of the given proportion of the mine waste can also be combusted, and for this heat treatment, again, a fluidised bed unit is suitable. The heat thereby generated is converted in a downstream steam circuit, which may comprise a steam turbine and electrical generator as well as a waste heat utilisation unit, or is utilised in the kiln 13 for baking the raw mouldings 12.

Example The mine waste material employed consisted of clay, sand and marl, and had a total moisture content of 10% by weight. The content of combustible carbon corresponded to a thermal yield of 700 kcal/kg.

The proportion of the material fed to the thermal reactor was 70% by weight, and on calcination in the reaction a loss of 30% (H20 + C) was observed. The heat liberated by the calcination, namely 380 kcal/kg, was available for further process stages and for generating electrical current. The calcined material, at 200"C, was mixed with the untreated proportion of the mine waste (30 parts by weight) and with 20 parts by weight of freshly mined clay, and was plasticised to give a plastically mouldable composition.

Moisture calculation for the moulding composition: 50% (mine waste and freshly mined clay) with 40% of H2O 20.0 50% (calcined material) with 0% of H2O Moulding composition: H2O content = 20.0% Temperature calculation for the moulding composition: 50% at 150C 7.5 50% at 200"C 100.0 Moulding composition: "C = 107.5 Under these starting conditions, drying can be carried out at little expense by means of the waste heat of the tunnel kiln.

Burning calculation: 30% with 800 kcal 240.0 70% with 15 kcal 10.5 Burning composition: kcal = 250.5 If the tunnel kiln is run suitably, this composition burns away automatically and without hazard.

For 100,000 tonnes per annum of mine waste processed, and for 20,000 tonnes of mined clay, it is possible to produce about 60 million standard size bricks, depending on their porosity, and 2.0 MW of electrical energy. The burning and drying can be carried out without additional supply of energy.

Claims

1. A process for the manufacture of brickmaking compositions using mine waste containing carbon and clay and derived from the preparation of coal, in which process comminuted mine waste is mixed with additives, such as clay, brick earth, lime or the like, and is then plasticised, characterised in that a predetermined portion of pre-comminuted solids is separated off, combustible constituents contained in the separated portion are burnt or gasified by heat treatment and used to generate useful energy, and the hot degassed solid portion is re-mixed with the thermally untreated solid portion, which has been mixed with the additives.

2. A process according to Claim 1, characterised in that the hot degassed solids are finely comminuted before re-mixing.

3. A process for the manufacture of bricks according to Claim 1 or 2, characterised in that the mixture of untreated solids, additives and degassed solids is plasticised by extrusion, pressed into shapes and then baked.

4. A process according to Claim 3, characterised in that the degassed portion of the mineral materials is mixed, whilst hot, with the portion of the mineral materials which has not been heat-treated, and with binder clay, and the mixture is pressed.

5. A process according to one of the preceding claims, characterised in that the separated portion of the mineral materials is heat-treated in a fluidised bed, that the gases formed are freed from dust whilst hot, and that dust which has been precipitated is mixed with the degassed part of the mineral materials.

6. A process according to one of the preceding claims, characterised in that the gas formed during the heat treatment of a portion of the solids is combusted without purification and the heat energy is employed for generating steam.

7. A process according to Claim 3, characterised in that the gas formed during the heat treatment of a portion of the solids is fed, without purification, to a brick forming kiln.

8. Apparatus for carrying out the process according to one of the preceding claims, which apparatus is characterised by a first comminuter for carbon-containing solids, a proportioning device for separating a portion of the solids, a reactor for the continuous heat treatment of the portion of the solids which has been separated off, sizing means for hot material, mixing means for mixing the portion of solids which has not been heat-treated, and the additives, with the heat treated portion of solids, and an extruderfor the combined solids mixture.

9. Apparatus according to Claim 8, characterised in that the proportioning device is a pan feeder with corresponding belt weighers.

10. Apparatus according to Claim 8 or 9, characterised in that the reactor is a combustion reactor with a down-stream steam generator.

11. Apparatus according to Claim 10, characterised in that the combustion reactor is a fluidised bed furnace.

12. Apparatus according to Claim 8 or 9, characterised in that the reactor is a degassing and gasification reaction, and that devices are provided for introducing hot unpurified combustion gases into a kiln for the ceramic compositions.

13. A process for the production of brickmaking compositions substantially as hereinbefore described with reference to the accompanying drawing.

14. Apparatus for carrying out the process of Claim 1 which apparatus is substantially as hereinbefore described with reference to the accompanying drawing.