GB2119351A - A method for the simultaneous production of combustion gas and argillaceous articles - Google Patents

Abstract

Argillaceous articles, such as breeze blocks, are produced simultaneously with combustion gas in the same, indirectly heated, closed vessel (A) by placing in the vessel stacks (3) of blocks, each comprising 10 - 60% by mass of a gas-producing constituent such as coal. The material (3) is progressively raised in temperature to not more than 900 DEG C maximum and a gasification medium (e.g. H2O) introduced as the temperature rises above 700 DEG C (8). Throughout this time an internal pressure in excess of 100 pa is maintained in the vessel by controlling the discharge of gas through pipe 5 by valve 6 and, when valve 6 is closed during cooling, controlling the outflow of cooling medium by valve 7. Gas from the pipe 5 is burnt in the indirect-heating means for the vessel. <IMAGE>

Description

SPECIFICATION A method for the simultaneous production of combustion gas and argillaceous articles This invention relates to a method for the simultaneous production of combustion gas and argillaceous articles, such as light-weight bricks or breeze blocks or ceramic articles, preferably using a hyd rothermal firing process.

A method is already known for the production of building materials and ordinary ceramic objects, operating at relatively low firing temperatures and using steam (DDR Patent Specification No. 72487).

The energy required for the drying and firing process is supplied wholly from an extraneous energy source for the indirect heating of the apparatus.

Processes are also known in which solid fuels are converted into combustion gas in a separate gas generator. Combustion gas, suitable for combustion in high temperature units, is produced, for example, from brown coal briquettes or pit coal in special gas generators. As by-products ash and slag containing contaminants are produced.

Owing to the fact that high-grade energy sources such as fuel oil and natural gas are becoming scarce the problem arises, particularlyforthe production of building materials in large quantities, of proposing technical solutions which, while utilising low-grade energy sources, of which there is a sufficiency, will ensure reliable operation of the production equipment.

West German Patent Specification No. 2,851,412, for example, describes the use of washing waste as an essential constituent of the ceramic paste to be produced. In the process proposed about 70% of the washing waste used is employed in a separate gas generating plant, the gas produced being conveyed to a kiln or steam generator and the degasified washing waste to a mixer via a preparation plant.

This solution, while no longer needing any highgrade fuel does involve the use of a separator gas generator and also a number of additional units, such as dust removers, sorters and conveyors.

Gas generators have recently come back into use for the production of gas for high-temperature installations in the ceramic industry. On pp. 26-28 of the "Brick and Clay Record" 171 (1977)11,for example, a description is given of how the gas required for the operation of a continuous brick kiln is produced from anthracite coal of a given grain size range in a special gas generator with an agitator apparatus.

In this method too a separate gas generator has to be used and the considerable quantities of ash occurring as a by-product have to be removed.

An object of the present invention is to avoid additional outlay on separate gas generators, prevent the creation of ash and slag as undesirable by-products and to make use of raw materials hitherto unusable.

Another object of the invention is to provide a process whereby the use of a separate gas generator can be dispensed with, so that the high-temperature installation can be heated mainly without an extraneous gas supply and light weight, heatinsulating building materials can be produced in the same process.

According to the present invention there is provided a method for the simultaneous production of combustion gas and argillaceous articles, in which argillaceous material having a water content in the range 2 - 3% by weight and 10 - 60% by mass of a gas-producing, combustible constituent is placed in a closed vessel provided with gas-burning indirect heating means, a valve-controlled gas discharge duct, a gasification-medium inlet, a cooling medium inlet and a valve-controlled heating cooling medium outlet duct, the method comprising progressively raising the temperature of the material in the vessel to a maximum of not more than 900"C so that the material is first dried and then gasified, a gasification medium being introduced into the vessel through said inlet therefor as the temperature of the material rises above 700 C, maintaining the material in the vessel art a temperature in excess of 700 C for a time period sufficient for consolidation and degasification of the material to be completed and thereafter progressively cooling the material to a temperature in the range 50"C - 1500C by the controlled passage through the vessel of the cooling medium, the valve of the gas discharge duct being closed during the cooling phase, each said valve being regulated during the heating, degasification and cooling phases to maintain throughout said phases an internal pressure in the vessel of at least 1 00pa, gas discharged from the gas discharge duct when the valve thereof is open being burnt in said indirect heating means Preferably the gasification medium employed is water which is introduced into the vessel through nozzles as the material rises to and while it is maintained at a maximum temperature in the region of 800"C until the material is fully degasified and hydrothermally consolidated.The material in the vessel is preferably first dried by progressively raising it in temperature to about 200"C over a period of approximately 2 hours, gasified by raising its temperature to approximately 800"C over a period of 7 hours, degasified by maintaining it at a temperature of approximately 800"C for approximately 8 hours and cooled from approximately 800"C to a temperature of approximately 1 OO"C over a period of 6 hours.

The gas discharge ducts of a plurality of similar vessels are preferably connected to a common gas supply line which in turn supplies the indirect heating means of all the vessels, the sequence of operations of the vessels being desynchronised so that after start-up heating of a first vessel the gas discharge duct valve of at least one of the vessels will be open when that of another is closed. In this arrangement the respective cooling medium outlet ducts of the vessels are preferably connected to a common supply line and the arrangement is preferably such that cooling of the material in one vessel commences before that in another vessel is completed to maintain a substantially constant supply of heated cooling medium throughout operation of the vessels. Said common supply line preferably con ducts heated cooling medium from the vessels to an extraneous consumer unit.

The cooling medium used may be air.

A preferred embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a temperature-time curve for a single vessel, Figure2 is a schematic diagram of a battery of vessels interconnected to form an installation which has consumer units connected up to it, Figure 3 is a side sectional elevation of a vessel, and Figure 4 is a graph in which the temperature and time curves for four individual vessels connected up to form a battery are superimposed.

The method of the invention comprises the following steps: Residual drying, at a temperature of up to 200"C, of the material used (a-b).

Heating up to 900"C of the material, the combustible constituents being gasified at the same time (b-d).

Introduction when the temperature of the material is rising between 700-900"C of a gasification agent through a nozzle (c-d).

Maximum temperature, once reached, to be maintained until the completion of the hydrothermal consolidation and degasification (d-e).

Cooling, from the maximum temperature of up to 900"C to about 50"C, of the material.

The gasification of the combustible constituents is controlled by the quantity of gasification agent (e.g.

water) supplied per unit of time and by the prevailing temperature. The water is proportioned in accordance with the ratio of the combustible constituents to the argillaceous material and with the mineralogical composition of the latter. The rule applies that the quantity in which the gasification agent has to be added will be the greater, the higher the proportion of the material represented by the combustible constituents.

The use of a degasification agent can be dispensed with when a material is used in which the combustible constituents only represent a low proportion (e.g.10% by mass) of the material and in which the chemico-mineralogical composition of the mineral constituent is such that the dehydroxylation of the clay minerals and the gasification of the carbonate releases the amount of water and Co2 required for degasification.

The selected excess pressure in the sealed vessel of at least 100 Pa is regulated, up to the commencement of cooling, by regulating the rate of discharge of combustion gas from a vessel via its pipe 5 by regulating the valve 6, a valve 7 of a cooling air pipe of the vessel being closed. Starting with the drying process the steam occurring and the combustion gas is discharged from the sealed vessel via the combustion gas pipe 5 to an indirect heating means for the same and/or other vessels A - D, while surplus quantities of combustion gas are conveyed to extraneous consumer installations 2.

After the end of the "temperature maintenance period" d-e the gas exit pipe 5 is closed by closing valve 6 and the cooling phase is commenced by the introduction of air from nozzles of an air supply pipe 10 or of water via a water supply pipe 8. The resulting heated cooling air or steam is discharged through the pipe controlled by valve 7 to consumer units such as drying or space heating installations (not shown). After the termination of the cooling phase the completely fired argillaceous products, cooled down to 150 - 500C, are extracted from the vessel and a fresh cycle can commence.

To facilitate start-up, in the event of damage or as an auxiliary fuel for the gas consuming units, extraneous gas is introduced, as necessary, into the combustion gas piping system 4.

A particularly advantageous use of the invention is obtained if a number of vessels, at least three, are interconnected and operated in such a way as to ensure an almost continuous operation with approximately uniform production of combustion gas and heated cooling air or water as well as finished products in which case at least one vessel is operated in phase d-e (degasification) and at least one further vessel is at the same time operated in the phase e-f (cooling).

Besides enabling a separate gas generator to be dispensed with the advantages obtained with the invention enable the ash and slag occurring in the degasification and gasification processes to be bound into the products (light-weight bricks). Furthermore, the application of the invention enables use to be made of raw materials which hitherto proved unusable, with considerable economic benefits.

According to Figure 1, the duration of the cycle of an individual vessel A - D is 24 hours. One hour is accounted for by the introductin of raw material and removal of cooled articles, 2 hours by the residual drying a-b, seven hours by the heating b-d, the gasification by heat alone being carried out within the stage b-c and gasification by heat and with the addition of a gasification medium within the stage c-d. Eight hours are accounted for by the degasification phase d-e, which in the example illustrated is carried out at 800 , water being introduced into the vessel through nozzles, and six hours being accounted for by the cooling e-f, which is carried out by blowing cold air into the vessel from a pipe 10. In the example illustrated the temperature of the material, when the cooling is terminated, is 1 OO"C.

In Figure 2 four individual vessels A - D are interconnected to form a "battery" in order to ensure the continuity of the production process. Continuity of production results from the periods ofthetreat- ment cycles and the number of vessels in the installation. In the example illustrated start-up has to be initiated every six hours by commencing the heating of a first vessel by an extraneous gas supply through pipe 4.

Figure 4 shows the battery of vessel A - D of Figure 2 in operation. At the time represented by the line E in Figure 4 the vessel D is starting up, the vessel C is in the heating/gasification phase b-d, while the vessel B is in the degasification phase d-e and the vessel A in the cooling phase e-f.

This method of conducting the process ensures that at every moment there will be a vessel operating in the cooling phase e-f, so that continuous waste heat is available for other installations (not shown). It also ensures that there is at any moment at least one vessel emitting combustion gas. Owing to the fact that the gasification phases of successive vessels overlap by a total period of about eight hours the continuity of the flow of the combustion gas is ensured in sufficient quantity.

In Figure 3, gasification and degasification during phase c-e is effected by the introduction into the vessel of water via a water supply pipe 8. Water is fed into the vessel through nozzles which are inserted between stacks 3 of the material used, while combustion gas released by the material is taken away through pipe 5 to other vessels which are being heated and, if there is a surplus, to extraneous installations 2. By the respective adjusting and regulating valve 6 the combustion gas pipe 5 of a given vessel A - D is sealed off in a gas tight manner throughout the entire cooling phase e-f-a and rendered safe. During the cooling phase e-f, however, cooling air is introduced into the vessel via an air connection pipe 10 and discharged through a cooling air discharge pipe having a valve 7.

Combustion gas obtained from the vessels which have open valves 6 is fed into the common combustion gas pipeline 5 and conveyed by a blower 9 to the indirect heating means 11 of those vessels undergoing heating, surplus gas passing to extraneous gas consuming installations 2, such as tunnel kilns for the production of hard-burned bricks (Figure 2), via a branch of the pipeline 5 controlled by a valve 13.

In the example shown the parameters for the material and the method are as follows: Humidity of material used: 3.0% by mass Proportion of combustible constituents, mainly brown coal: 34% by mass Excess pressure maintained in a unit throughout gasification, degasification and cooling: 210 pa.

Claims (8)

1. A method for the simultaneous production of combustion gas and argillaceous articles, in which argillaceous material having a water content in the range 2 - 3% by weight and 10 - 60% by mass of a gas-producing, combustible constituent is placed in a closed vessel provided with gas-burning indirect heating means, a valve-controlled gas discharge duct, a gasification-medium inlet, a cooling medium inlet and a valve-controlled heated cooling medium outlet duct, the method comprising progressively raising the temperature of the material in the vessel to a maximum of not more than 900"C so that the material is first dried and then gasified, a gasification medium being introduced into the vessel through said inlet therefor as the temperature of the material rises above 700"C, maintaining the material in the vessel at a temperature in excess of 700"C for a time period sufficient for consolidation and degasification of the material to be completed and thereafter progressively cooling the material to a temperature in the range 50"C - 1500C by the controlled passage through the vessel of the cooling medium, the valve of the gas discharge duct being closed during the cooling phase, each said valve being regulated during the heating, degasification and cooling phases to maintain throughout said phases an internal pressure in the vessel of at least 100 pa, gas discharged from the gas discharge duct when the valve thereof is open being burnt in said indirect heating means.

2. A method as claimed in claim 1, wherein the gasification medium employed is water which is introduced into the vessel through nozzles as the material rises to and while it is maintained at maximum temperature in the region of 800"C until the material is fully degasified and hydrothermally consolidated.

3. A method as claimed in either preceding claim, wherein the material in the vessel is first dried by progressively raising it in temperature to about 200"C over a period of approximately 2 hours, gasified by raising its temperature to approximately 800"C over a period of 7 hours, degasified by maintaining it at a temperature of approximately 800"C for approximately 8 hours and cooled from approximately 800"C to a temperature of approximately 1 00'C over a period of 6 hours.

4. A method as claimed in any one of the preceding claims, wherein the gas discharge ducts of a plurality of similar vessels are connected to a common gas supply line which in turn supplies the indirect heating means of all the vessels, the sequence of operations of the vessels being desynchronised so that after start-up heating of a first vessel the gas discharge duct valve of at least one of the vessels will be open when that of another is closed.

5. A method as claimed in claim 4, wherein the respective cooling medium outlet ducts of the vessels are connected to a common supply line and the arrangement is such that cooling of the material in one vessel commences before that in another vessel is completed to maintain a substantially constant supply of heated cooling medium throughout operation of the vessels.

6. A method as claimed in claim 5, wherein said common supply line conducts heated cooling medium from the vessels to an extraneous consumer unit.

7. A method as claimed in any one of the preceding claims, wherein the cooling medium used is air.

8. A method for the simultaneous production of combustion gas and argillaceous articles substantially as described in the Description with reference to the Drawings.