GB2139332A

GB2139332A - Method of and apparatus for producing hydraulic binding agents

Info

Publication number: GB2139332A
Application number: GB08406882A
Authority: GB
Inventors: Dr Albrecht Wolter; Horst Herchenbach; Gunter Romelt
Original assignee: Kloeckner Humboldt Deutz AG
Current assignee: Kloeckner Humboldt Deutz AG
Priority date: 1983-03-21
Filing date: 1984-03-16
Publication date: 1984-11-07
Also published as: DK105684A; IT8447874A0; FR2543132A1; BR8401282A; DK105684D0; DE3310129C2; GB8406882D0; JPS59227749A; DE3310129A1

Abstract

The method comprises preheating raw material up to at least 450 DEG C and then dividing the flow into at least two component streams, of which one steam is burnt or roasted to form cement clinker in a kiln (2) and the other stream is branched off and used to produce a lightly burnt hydraulic binding agent. The branched stream consisting of gas and solids is taken from the part of the plant, operating in the temperature range between 450 DEG C and 950 DEG C, and is separated into solids and gas and the solids are cooled and further processed to form hydraulic binding agents (31). In the apparatus utilised, gas and solids are branched off in a conduit (5) which leads to a separator (6), the solids from which are supplied to a suspension-type cooler (8) and then pass to a slaking and mixing unit (18) where they are mixed with water and other substances to form the hydraulic binding agents. <IMAGE>

Description

SPECIFICATION Method of and apparatus for producing hydraulic binding agents This invention relates to a method of and apparatus for producing hydraulic binding agents.

The subject of an earlier invention according to DE-OS 28 15 161 is a method and an apparatus for producing different hydraulic binding agents from common raw materials in a burning or roasting process, wherein a mass flow of raw material in fine-grained form is heated at least up to dehydration temperature and the mass flow is then divided into at least two component streams of which the one component stream is burnt or roasted to form cement clinker in the further course of the burning or roasting process and the other component stream is branched off from the burning or roasting process, cooled in a separate cooling zone and used for the production of a more lightly burnt hydraulic binding agent.

A plant suitable for this was hitherto developed and operated so that a proportion of the preheated and at least partially calcined material was branched off, by using a proportioning adjusting valve or a volumetrically or gravimetrically proportioning extraction device, from a conduit through which the finegrained solids flowed at the discharge from a separating cyclone belonging to the preheating zone or the calcining zone, through a material routing means.

In this case, difficulties arose, because a proportioning adjusting valve often does not make it possible to divide a stream of solids into two component streams with the necessary accuracy. In addition, the use of other volumetrically or gravimetrically proportioning extraction devices is made more difficult by the fact that the stream of material have temperatures between 450 and 950"C. Also, such an extraction device must be completely enclosed because there are pressure differences of the order of a few hundred millibars between the extraction point and the surrounding atmosphere. Consequently, the use of an open extraction device is automatically prohibited.

The cooling of the branched-off component stream of fine-grained material gives rise to a further difficulty, particularly since recycling of the amount of heat surrendered in the course of this to the plant system is desirable.

The invention seeks to develop the known method and the corresponding apparatus in such a manner that the difficulties referred to and technical limits are reduced or substantially obviated.

According to a first aspect of the invention, there is provided a method of producing hydraulic binding agents from raw materials in a burning or roasting process comprising preheating the raw material in fine grain form to at least 450"C, dividing the preheated material into two flows oneof which is burnt or roasted to form cement clinker and the other of which is used for producing an hydraulic binding agent wherein the said other flow is branched off at a position in which the flow being branched has a temperature between 450"C and 950 C, the branched off flow is separated into solids and gas in a separate separating stage and the separated solids are cooled and further processed to form hydraulic binding agents.

In contrast to the difficulties in the precise separation of a component stream of finegrained solids out of an undivided stream of solid material in the given temperature range, the division of a stream of gas laden with solids and its quantitative control does not involve any important difficulties. Thus, an extremely accurate quantitative division can be successfully'achieved within the closed plant by the branching off of the component stream from the stream of gas and solids of the plant and subsequent separation, in a separate separating stage, into solids and gas.

The branching off of the component stream may be carried out from the stream of waste gas and solids from the calcinator.

The material occurring there has the highest state of activation and consequently also a temperature situated at the upper limit of the temperature range.

The solids may be cooled in a suspension typecooler with air in counter-current.

As a result of the use of a suspension-type cooler following the separating stage, a cooling of the fine-grained solids by direct heat exchange with cooling air can be achieved without difficulties. In the course of this, the greater part of the heat content is transferred from the solids to the cooling air and introduced into the system of the plant again at a suitable point. In this manner, the amount of heat given up to the cooling medium is advantageously returned to the plant.

As a result, the advantage is achieved that the amount of heat in the material branched off from the calcinator is mainly returned to the plant on the way through the following suspension-type cooler. Consequently, the heat economy of the plant is not affected disadvantageously and this results from the desired high activation and temperature state of the solids branched off..

The burnt gas from the branched-off solids may be introduced into a downstream stage of the heat-exchanger or be drawn off in a bypass in the case of a high content of harmful substances.

The proportion of the component stream from the stream of gas and solids may amount to between 1% and 30%, preferably between 5% and 20%. Adhering to such precise proportions is possible for the first time. The surprising accuracy with which the separation of a component stream of solids from the mass flow of the fine-grained solids travelling through the plant system is rendered possible by means of the division of the stream of gas. This is one of the important advantages of the present method.

A further advantage is that the volumetric control can be achieved in a very advantageous and simple manner, if the volumetric control is effected by indirect means, by volume control or throttling of the stream of gas from the separator, recycled to the plant or to the by-pass.

Gas drawn off in the by-pass and laden with harmful substances may be cooled by air and, possibly, the addition of water, at least until the harmful substances condense. By-pass dusts contained therein are separated out, the gas is removed from the plant. The by-pass dusts are added to the hydraulic binding agent, thrown away or used elsewhere.

It is true that it is known, exclusively in order to reduce the circulation of harmful substances and/or the content of harmful substances in the cement clinker, to branch off a component stream of gas from the internal circuit of a cement burning plant system, for example from the region of the calcining zone, to cool it quickly with cooling air, possibly with the addition of water, and to separate out the alkalis, chlorine compounds and sulphates, which condense in the course of this operation as dusts, and to remove the purified gas from the plant. In this case, the elimination or further use of the dust which is separated out in the by-pass device and which has to be eliminated from the production process, causes difficulties, (Zement-Kalk Gips, No. 5 (1962), page 203, Figure 11 and description right-hand column).Such a bypass device to reduce the content of harmful substances in cement clinker can also be seen, for example, from the DE-AS 21 61 411.

Whereas the by-pass dusts not only cause a material lossin the known methods and plants, but also involve dumping and utilization problems, in the present method, these can be added, without disadvantage, to the hydraulic binding agents produced by light burning and so be put to a logical use.

The spent air from the suspension-type cooler may be introduced into the calciner as tertiary air. Thus a recuperation of the heat extracted from the branched-off solids takes place and at the same time a logical supply of additional hot tertiary air is supplied to the reaction section of the calciner. This is particularly advantageous in plants which do not have any separate tertiary air conduit and which thus have to draw the combustion air for the calciner as air excess through the kiln.

In order to process the substantially caicined solid component, not burnt to form clinker, to form hydraulic binding agents, additives with hydraulic or pozzolanic properties may be added and mixed together to form a homogeneous mixture, the free lime cornpo- nent of the mixture being slaked with water and the mixture then being further cooled.

In this case, cement and/or ground blastfurnace slag may be provided as additives with hydraulic properties and power-station flue dust, pozzolana and similar substances may be added as additives with pozzolanic properties.

According to a second aspect of the invention, there is provided a method as claimed in claim 9 or 10, wherein the separated dusts are added to the hydraulic branching agent.

The invention will now be described in greater detail by way of example with reference to the drawings, in which: Figure 1 is a circuit diagram of a burning or roasting plant for the production of hydraulic binding agents having a conduit branched off from the calciner, a separating unit, a suspension-type cooler for the branched-off material and a gas conduit leading from the separator to a heat exchanger; and Figure 2 shows a circuit diagram of the same plant as shown in Figure 1 but with the branched-off component stream of gas drawn off via a by-pass.

Figure 1 shows a burning or roasting plant comprising a group of cyclones I, lí, Ill forming a preheating zone, with a calciner having a reaction section 1 and a separating cyclone IV, a rotary kiln 2 and a following cooler 3. A tertiary-air conduit 4 bridges the rotary kiln.

Branched off from the waste-gas conduit 1' of the calciner, is a branch conduit 5 which leads into a separator 6. The separator 6 separates the branched-off component stream into gas and solids. The latter are supplied to a suspension-type cooler 8 by the conduit 7.

The cooler 8 comprises two heat-exchanger stages constructed in the form of cyclones 9 and 10 and an interposed blower 11 as well as a fresh-air suction conduit 12 constructed like a siphone. A tertiary-air conduit 4, which is fed with hot spent cooler air, is provided to introduce the heated fresh air into the reaction section 1 of the calcinator in the region of the fuel introduction device 14. The gas separated from the solids in the separator 6 is conveyed back into the cyclone stage II for example, by a conduit 1 5. In this conduit 1 5 there is a remote-controlled throttle member 16 by means of which the mass flow of the recycled gas can be adjusted as desired and so the amount of the component stream of gas and solids branched off from the calcinator 1 through the branch conduit 5 can be adjusted also.

The fine-grained material cooled in the suspension-type cooler 8 is introduced from the cyclone 10 by the conduit 1 7 into a cooling, slaking and mixing unit 18 by way of conduit 1 7 and there it is mixed with the addition of water from the conduit 1 9 and possibly with the addition of substances having hydraulic properties such as cement and/or ground blast-furnace slag or additives with pozzolanic properties such as power-station flue dust, pozzolana or the like. Also the free lime contained in the mixture is slaked by the addition of water. Connected to this cooling, slaking and mixing unit 18 and to a homogenizing unit 20 which may follow it and which may serve for the final after-treatment, is a conduit 21 for removing dust and vapour. This leads to a gas cleaning means 22 (Figure 2).

The plant shown in Figure 2 differs from that shown in Figure 1 in that gas from the separator 6 is drawn out of the plant via a mixing chamber 23, a by-pass conduit 24, a by-pass gas cleaning device 22 and an exhaust fan 25.

Connected to this mixing chamber 23, to cool the gas which obtained at about 800"C in the separator 6, is a fresh-air cooling-gas conduit 27 equipped with blower 26. Also leading into the mixing chamber 23 is a water injection device 28. By-pass dust collecting in the gas cleaning device 22 and separated out of the gas is introduced into the cooling, slaking and mixing unit 18 by conduits 29, 294. By-pass dust may possibly be partially or wholly admixed with the finished material indicated at 31 by the branch conduit 30, for which purpose the dust is introduced into the feed side of the homogenizing unit 20. Of course, external use of the by-pass dust is also possible, for example as fertilizer, for which purpose it is removed from the plant, as is known, and can be further processed according to its sales value.

A substantial improvement and perfection of the older method and of the apparatus according to the DE-OS 28 1 5 161 is successfully achieved as described above in a simple and surprising manner.

The difficulties arising during the splitting up of a hot stream of fine-grained solids, with regard to precise adherence to the quantitative proportions, are overcome in a surprising manner. At the same time, means are shown for cooling the branched-off component stream without difficulty and for recycling the amount of heat transferred to the coolant, e.g.

air, at least mainly into the plant system in a logical manner. At the same time, a way is shown of preventing a feared concentration of harmful substances in the internal circuitry of the burning or roasting plant, while the disadvantages which are usually present in the course of this, such as losses of material and energy, are almost completely avoided. As a further advantage, there is a possibility of using the by-pass dusts, collecting in a bypass gas cleaning device and generally enriched with alkali-chloride and/or sulphate compounds, in a logical manner, in that these may possibly be added, wholly or partially, to the lightly burnt hydraulic binding agents provided for the preparation of mortar.

And finally, with it, it is possible to produce two different products of hydraulic binding agents, namely cement and binding agent for the preparation of mortar, in one and the same burning plant, without problems, and to do so with the optimum use of materials and energy.

Claims

1. A method of producing hydraulic binding agents from raw materials in a burning or roasting process comprising preheating the raw material in fine grain form to at least 450 C, dividing the preheated material into two flows oneof which is burnt or roasted to form cement clinker and the other of which is used for producing an hydraulic binding agent wherein the said other flow is branched off at a position in which the flow being branched has a temperature between 450"C and 950on, the branched off flow is separated into solids and gas in a separate separating stage and the separated solids are cooled and further processed to form hydraulic binding agents.

2. A method as claimed in Claim 1, wherein the branching off of the component stream is effected from the waste-gas/solids stream of the calciner.

3. A method as claimed in Claim 1 or 2, wherein a suspension-type cooler is used to cool the solids and air is used as a cooling medium.

4. A method as claimed in any one of Claims 1 to 3, wherein the gas separated from the solids is again supplied to a downstream stage of the heat exchanger.

5. A method as claimed in any one of Claims 1 to 3, wherein the gas separated from the solids is drawn off in a by-pass in the case of a high content of harmful substances.

6. A method as claimed in any one of Claims 1 to 5, wherein the proportion of the component stream of the gas/solids stream amounts to between 1 % and 30%.

7. A method as claimed in Claim 6, wherein the proportion amounts to between 5% and 20%.

8. A method as claimed in any one of Claims 1 to 7, wherein the volumetric control of the branched-off stream of solids is effected by volumetric control of the stream of carrier gas.

9. A method as claimed in Claim 5, wherein gas drawn off in the by-pass is cooled by air at least until condensation of the harmful substances and by-pass dusts contained therein are separated out.

10. A method as claimed in Claim 9, wherein the drawn off gas is additionally cooled by the addition of water.

11. A method as claimed in Claim 9 or 10, wherein the separated dusts are added to the hydraulic binding agent.

12. A method as claimed in Claim 3, wherein the spent air from the cooler is introduced into the calciner as tertiary air.

1 3. A method as claimed in any one of Claims 1 to 9, wherein, in order to process the substantially calcined solids component which is not burnt into clinker, to form hydraulic binding agents, additives with hydraulic or pozzolanic properties are added and mixed together to form a homogeneous mixture, the free-lime component of the mixture is slaked with water and this is then further cooled.

14. A method as claimed in Claim 13, wherein cement and/or ground blast-furnace slag are used as additives with hydraulic properties and power station flue dust, pozzolana and similar substances are used as additives with pozzolanic properties.

1 5. An apparatus for producing hydraulic binding agents from raw materials in a burning or roasting plant for fine-grained material comprising a preheater, a calciner, a clinker burning unit, a clinker cooler and a dividing device for drawing off thermally pretreated solids between the preheater and the clinker burning unit wherein the dividing device comprises at least one conduit branched off from the region of the calciner for drawing off a component stream of gas and solids, a separating unit for separating the gas and solids and a cooler for fine-grained solids.

16. An apparatus as claimed in Claim 15, wherein the cooler is a counter-current suspension-type cooler.

1 7. An apparatus as claimed in Claim 1 5 or 16, wherein a conduit connects the solids discharge of the separating unit to the cooler.

1 8. An apparatus as claimed in Claim 1 7, wherein a gas shut-off member is disposed in the conduit connecting the separating unit to the cooler.

19. An apparatus as claimed in any one of Claims 1 5 to 18, wherein a tertiary-air conduit connects the gas outlet of the cooler to the calciner.

20. An apparatus as claimed in any one of Claims 1 5 to 19, wherein a waste-gas conduit leads from the gas outlet of the separator to the heat exchanger or to the by-pass.

21. An apparatus as claimed in Claim 2G, wherein a throttle member is disposed in the waste-gas conduit.

22. An apparatus as claimed in Claim 21, wherein the throttle member is remotely controlled.

23. An apparatus as claimed in any one of the Claims 1 5 to 22, wherein the countercurrent suspension-type cooler comprises two cyclone stages with a connecting conduit in which a blower is disposed, and wherein the conduit from the separator leads into the part of the connecting conduit which connects the pressure side of the blower to the first cyclone stage.

24. An apparatus as claimed in any one of Claims 1 5 or 23, wherein a mixing chamber is connected to the gas outlet of the separating unit, the mixing chamber comprising a device for the controllable supply of cooling air and for the spraying in of water, to which device a by-pass conduit with a by-pass gas cleaning means is connected.

25. An apparatus as claimed in any one of Claims 1 5 to 24, wherein units are provided following the cooler, to slake and homogenize the hydraulic binding agent, the units comprising at least one mixer and a device for the after-treatment of the binding agent to which units is connected a removal conduit for removing dust from vapour, which leads into the by-pass conduit and is equipped with a regulating member and conduits which connect the dust collecting chamber of the bypass gas cleaning means to the said units.

26. An apparatus as claimed in Claim 25, wherein the said units also comprise a water spraying device.

27. An apparatus as claimed in Claim 25 or 26, wherein the regulating member in the removal conduit is remote controlled.

28. A method of producing hydraulic binding agents substantially as described herein with reference to the drawing.

29. An apparatus for producing hydraulic binding agents substantially as described herein with reference to the drawing.