DK176553B1 - Process and plant for the manufacture of cement clinker - Google Patents

Description

in DK 176553 B1

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for the production of cement clinker in which cement flour is preheated and burned to clinker in a furnace system and cooled in a subsequent clinker cooler, wherein process waste 5 is heated in a separate chamber where the gas generated by the waste is heated to the furnace system. heating the cement barrel and where the solid portion is directed away from the chamber.

The invention further relates to a plant for carrying out the method.

Examples of combustible waste include car tires, railway sleepers, furniture, carpets, wood waste, garden waste, 15 kitchen waste, paper sludge, biomass, petcoke, sewage sludge and pale words.

EP-1200778 discloses both a method and an apparatus of the above-mentioned kind, in which the waste is burned in the separate chamber while supplying hot air from preferably the clinker cooler. The flue gas from the combustion is conducted from the chamber into the preheater of the furnace system, where it is used to heat the cement raw material. In practice, the process and the plant have proved particularly suitable for waste incineration and 25 provide a significant heat contribution that improves the overall operating economy of the plant. However, it has also been found that the NOx emission from this known plant can be high because in the chamber there is no reduction of the NOx formed in the furnace by the burning of the cement clinkers.

In EP-1756502, this problem is solved by introducing NOx containing flue gas, preferably from the furnace of the furnace system, into the chamber so that the NOx content of the flue gas by various NOx reducing reactions is substantially reduced.

At both of the plants described above, the amount of waste that can be treated in the separate chamber is limited by the heat demand in the heater of the furnace system to which the combustion gas is discharged from the chamber. Furthermore, the waste incineration in the chamber cannot completely substitute the fuel needed in the preheater 5 because in practice it has proved difficult to control the temperature in the waste incineration chamber and therefore there is a need to feed at least a small amount of fuel. directly in the preheater. In the known plants, the size of the waste pieces treated in the 10 separate chamber is also limited by the given residence time in the chamber, because any unburned waste that is discharged from the chamber into the preheater system can cause operating problems due to coating formation and increased emissions. of CO and SO2. This problem is traditionally solved by ensuring that the waste has a sufficiently small particle size to achieve complete combustion in the chamber at the given residence time. However, much of the waste that can be used as fuel in cement manufacture is in relatively large size, such as rail sleepers, furniture and car tires, which necessitates a relatively expensive comminution process before the waste can be used as fuel.

The object of the present invention is to provide both a method and a plant for the production of cement clinker, in which the amount and size of waste treated in the separate chamber is independent of the actual cement production in the plant and the comminution of the waste is considerably less resource consuming.

30

This is achieved according to a first aspect of the present invention by a process of the kind set forth in the preamble, characterized in that the waste is heated to a temperature of at least 150 ° C in the separate chamber, and that the discharged solid part of the chamber is comminuted in smaller quantities. particle sizes in a comminution device.

DK 176553 B1 3

According to another aspect of the invention, there is provided a plant for the manufacture of cement clinkers comprising an oven system, a clinker cooler and a separate waste heating chamber, which chamber comprises inlet for introducing waste into the chamber and outlet respectively for feeding it in the heating. gas generated from the waste to the furnace system and to discharge the solid portion, characterized in that it comprises means for heating the waste to a temperature of at least 150 ° C in the separate chamber, and a comminution device for comminuting the solid portion discharged from the chamber. smaller particle sizes.

Hereby it is achieved that waste in the separate chamber can be treated with substantially larger unit sizes and further in larger quantities than heretofore, because the temperature the waste is heated to in the separate chamber can be adjusted so that the amount of fuel contained in the gas which is conducted is from the separate chamber to the furnace system preheater, substantially corresponds to the heat demand in the preheater, and because the solid portion of the heated waste containing the remaining amount of fuel in the waste is diverted from the chamber and comminuted in a comminution device. Furthermore, by heating the waste to at least 150 ° C, the subsequent comminution process is much less resource-consuming, which is primarily because the conversion that occurs during the heating makes the heated waste considerably brittle and thus easier to comminute than the untreated waste. and that the absolute mass of the heated waste is less because volatile components of the waste are released during the heating. The heated and finely divided waste can then be used as fuel in all places in the cement-making plant, where there is a need for introduction of fuel, such as in the oven or the calciner.

Thus, it will be possible to substitute the entire 35 fuel demand in cement manufacturing plants with relatively inexpensive waste fuels.

In principle, the waste can be heated in any suitable manner in the separate chamber, such as by means of electricity, hot gas, by burning of fuel or by introducing preheated, calcined or burnt raw flour. However, it is preferred that the waste be heated by process gas from the plant itself, in which case the process gas may be hot air from the clinker cooler or hot flue gas from the furnace system. The waste in the separate chamber can be heated by direct and indirect contact between the gas and the waste. Furthermore, the heating of the waste in the separate chamber can take place in co-current, counter-current or in cross-flow to the gas supplied, depending on what is most optimal.

The heated and comminuted solid can be introduced directly from the comminution device or from an intermediate storage at the optimum location for subsequent combustion.

For example, if the waste is heated to such a temperature, typically higher than 300 ° C, in the separate chamber, that the solid portion mainly consists of coke, this coke according to the invention may advantageously be introduced into the furnace system where the oxygen content is high, e.g. 10% or higher, thereby ensuring a rapid burnout of the coke.

In connection with the following detailed description 25 of various exemplary embodiments of systems according to the invention, this aspect of the invention will be explained in more detail.

Furthermore, in order to optimize the plant's capacity and control of the temperature in the separate chamber, it is preferred that cement flour can be supplied to the chamber via a cement raw inlet. The feedstock will act as a heat reservoir that helps keep the temperature at the desired level, even when the process conditions fluctuate.

The chamber may comprise an inlet for introducing feedstock from the preheater, calciner and / or feedstock.

DK 176553 B1 5

In one embodiment, the plant comprises means for heating the waste in the separate chamber in the form of a channel for introducing process gas into the chamber which is connected to either the clinker cooler or the furnace system.

5

The waste heating chamber may be formed in any suitable manner. In one embodiment, it may be configured as a housing containing a substantially horizontal turntable supporting and transporting the waste through the chamber from its inlet to its outlet, the chamber comprising a suitable arrangement for discharging the solid portion of the heated waste.

In an alternative embodiment of the invention, the chamber 15 may be constituted by a drum, the center axis of which is preferably disposed at a slight angle to the horizontal, and which is rotated about its center axis where the waste is introduced at one end of the drum and discharged at the other end. The advantage of using a drum is that the surface of the waste hereby is continuously crushed by blows and blows and falls off as the waste from the outside and towards the core is made brittle.

The comminuting device may be any suitable device for comminuting crisp material, such as a pipe mill, a rolling mill or a rolling press.

The system according to the invention may further advantageously comprise one or more devices for removing metal parts and other undesirable components from the solid part. These 30 devices may comprise magnetic separators and may be disposed both before and after the comminution device.

Because the amount of waste treated in the separate chamber may be independent of the current cement production DK 176553 B1 6 in the plant, at times much more waste fuel can be produced than is needed in the cement production plant. Therefore, it is preferred that the plant comprises a waste fuel storage silo 5 which is heated and comminuted according to the above.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained in more detail with reference to the drawings, which are schematic and in which FIG. 1 shows a general process diagram of a plant for carrying out the method according to the invention,

FIG. 2 shows a preferred embodiment of a plant for carrying out the method according to the invention, 15

FIG. 3 shows a modified embodiment of the embodiment shown in FIG. 2, and

FIG. 4 and 5 show alternative embodiments of systems for carrying out the method according to the invention.

In the process diagram shown in FIG. 1 shows a plant for the manufacture of cement clinker. The plant comprises an oven system with a preheater system comprising a preheater 25 1 and a calciner 3, and an oven 5, a clinker cooler 7 and a separate waste heat chamber 9 introduced through an opening 11 in chamber 9. During plant operation For example, cement raw material from a raw material not shown is fed to the preheater inlet of preheater 1. In the furnace 5, the calcined raw flour is burnt to cement clinker, which in the subsequent clinker cooler 7 is cooled by atmospheric air. Part of DK 176553 B1 7 of the thereby heated air is conducted from the clinker cooler 7 via a channel 15 to the calciner 3. As seen in the process diagram, the separate chamber 9 for supplying the energy needed for the heating of the waste via channels 25 may be connected to one or more sources, such as one of the plant's process units comprising the clinker cooler 7, the furnace 5, the calciner 3 or the preheater 1, or a separate energy unit 6 in the form of, for example, an electric or fuel-driven heat generator. Furthermore, for conveying the gas generated by the heating of the waste to the furnace system, the separate chamber 9 can be connected via ducts 4 to the furnace 5, the calciner 3 and the preheater 1, respectively.

The separate chamber 9 further comprises a suitably formed solid outlet 8 for draining the heated solid portion.

According to the invention, the waste is heated to a temperature of at least 150 ° C in the separate chamber 9, so that the solid part is made brittle and thus less resource consuming 20 to comminute. The heated solid portion is then extracted via the solid state outlet 8 of the chamber 9 and passed to a comminuting device 10, where the solid portion is comminuted to a smaller particle size, preferably a particle size suitable for blow-in via conventional burners. From the comminution device 10, the comminuted solid having a high fuel value can be fed directly through the ducts 12 directly to the furnace 5 for firing via its main burner or to the calciner 3 for firing therein. Alternatively, the finely divided solid can be fed to a silo 16 for storage for later use. A magnetic separator or the like may be disposed immediately before or after the comminution device for sorting out unwanted material components.

The temperature to which the waste is heated in the separate chamber 9 can be adjusted in various ways, inter alia, by controlling the amount of gas introduced into the chamber 9 and DK 176553 B1 8 using gas of different temperature from the plant's process units. In this way, the amount of fuel that is fed with the gas from the separate chamber to the heater of the furnace system can be adjusted to the heat demand in the preheater, at the same time that the solid part of the heated waste contains the remaining amount of fuel in the waste. Thus, in the separate chamber 9, wastes of substantially larger size can be treated and, moreover, in larger quantities than hitherto.

10 In FIG. Figure 2 shows a preferred embodiment of the system for carrying out the method according to the invention. The plant shown comprises a cyclone preheater 1, a calcinator 3, a rotary kiln 5, a clinker cooler 7 and a waste heat chamber 9 which is introduced into the chamber 9 via an inlet opening 15 11. During the operation of the plant, cement raw material is introduced into the preheater 1 via a raw material inlet. F and flow from here to the rotary furnace 5 through the cyclones of the preheater 1 and the calciner 3, thereby being heated and calcined by means of hot flue gas. In the rotary kiln 5, the calcined raw flour is burned to 20 cement clinkers, which in the subsequent clinker cooler 7 are cooled by atmospheric air. A portion of the thereby heated air is conducted from the clinker cooler 7 via a channel 15 to the bottom of the calciner 3. The chamber 9 is shown in this embodiment as a stationary chamber disposed 25 between the rotary furnace 5 and the calciner 3. The chamber 9 is provided with hot flue gas. from the rotary furnace 5 via a channel 2. From the chamber 9, the flue gas generated by the heating of the waste is fed into the calciner 3 via an opening / channel 4 located on the side of the calciner 3. In the embodiment shown, the waste is transported during the heating through the chamber 9 towards the solid outlet 8 of the chamber by means of a turntable 20. However, the transport of the waste through the chamber 9 can take place in many other conceivable ways, just as the chamber 9 itself can be formed in other ways, for example as a drum.

Typically, the flue gas introduced through the duct 2 into the separate chamber 9 from the rotary kiln 5 will typically have a temperature of between 1000 and 1200 ° C and because all the flue gas from the rotary kiln 5 is passed through the chamber 9, the waste in this embodiment will typically 5 is heated to above its ignition temperature. In this embodiment, therefore, an almost complete burnout of the smaller particles of the waste can be obtained, so that the solid part extracted via the outlet 8 comprises mainly coke and larger, brittle 10 scrap pieces.

A significant advantage of the one shown in FIG. 2, the calciner 3 is provided with a lower portion provided with preheated, oxygen-rich air from the clinker cooler 7. Hereby, the heated and finely divided solid portion comprising coke and coke-like constituents which, in order to achieve good burnout, requires a relatively long residence time in oxygen-rich environments, is fired at the bottom of the calciner 3 where these conditions are met. Furthermore, a significant NOx reduction in the flue gas is obtained from the furnace 5 in the separate chamber 9, as a result of the reducing conditions prevailing here.

The system shown in FIG. 3 is substantially similar to that shown in FIG. 2 except that the chamber 9 has moved away from its 25 position on the side of the calciner 3. Hereby, the chamber 9 can in principle be placed at any location, such as, for example, directly on the ground. Such placement of the chamber 9 will be particularly advantageous in cases where the amount of waste desired to be treated in the chamber 9 30 contains more energy than is immediately needed in the cement-making process and where the excess fuel in the form of heated and comminuted waste either thought to be stored in the silo 16 or disposed of. Furthermore, in this embodiment, there is no need to provide space in the preheater tower itself for the separate chamber, which is often cumbersome, and in addition, the need for transport equipment for conveying the waste to the separate chamber is less. As with the embodiment shown in FIG. 2, a significant NOx reduction in the flue gas is obtained from the furnace 5 in the separate chamber 9, as a result of the reducing conditions prevailing here.

5

The system shown in FIG. 4 differs from that shown in FIG. 2, primarily by passing the hot air from the clinker cooler 7 into the chamber 9 rather than into the calciner 3. Thus, the air in the chamber 9 will contain substantially more oxygen and thus 10 allow combustion not only of the volatile, combustible components of the waste but also of a a substantial part of the solid combustible components. However, the embodiment has the disadvantage that it does not have a NOx reducing zone and that the NOx content of the flue gas which is passed up through the preheater 15 is thus expected to be relatively large.

The system shown in FIG. 5 differs from that shown in FIG. 2, primarily in that the chamber 9 is placed under the calciner 3 so that all the flue gas from the rotary kiln 5 and chamber 9 is led up 20 through the calciner 3 and that the hot air from the clinker cooler 7 is fed into the calciner 3 downstream thereof in the direction of flow of the flue gas. As with the embodiments shown in FIG. 2 and 3, a significant NOx reduction in the flue gas is obtained from the furnace 5 in the separate chamber 9, 25 due to the reducing conditions prevailing here. In addition, large parts, such as steel parts, can be directed to the furnace 5 for circulation herein. However, the embodiment has the disadvantage that the calciner 3 does not include a zone of high oxygen content, where the heated and finely divided solid part comprising 30 coke and coke-like constituents is ensured a good burnout.

Furthermore, in all of the embodiments shown, the temperature of the chamber 9 can be controlled by introducing cement raw material from the preheater, calciner and / or feedstock.

35

Claims (13)

A process for producing cement clinker, wherein cement raw flour is preheated and burned to clinker in an oven system * 5 (1, 3, 5) and cooled in a subsequent clinker cooler (7), wherein process waste is heated in a separate chamber (9), wherein the gas generated by heating the waste is fed to the furnace system for heating the cement raw material and the solid part is led away from the chamber (9), characterized in that the waste is heated to a temperature of at least 150 ° C in the separate chamber (9), and decomposing the dissolved solid portion from the chamber (9) into smaller particle sizes in a comminuting device (10). Process according to claim 1, characterized in that the waste is heated in the separate chamber (9) by process gas from the plant itself. Process according to claim 2, characterized in that the waste 20 is heated in the separate chamber (9) by process gas from the clinker cooler (7) or the furnace system (1, 3, 5). Process according to any one of claims 1-3, characterized in that the waste in the separate chamber (9) is heated by direct contact between the gas and the waste. Process according to any one of claims 1 to 4, characterized in that the heated and finely divided solid from the atomiser (10) or from an intermediate storage (16) 30 is introduced into the furnace system where the oxygen content is 10% or higher. Process according to any one of claims 1 to 5, characterized in that cement flour is supplied to the chamber 35 (9) via a cement flour inlet. DK 176553 B1 12 A plant for the manufacture of cement clinkers comprising an oven system (1, 3, 5), a clinker coal (7) and a separate waste heating chamber (9), which chamber (9) comprises inlet (11) for introducing waste in the chamber (9) and outlets (4, 8), respectively, for conveying the gas produced by heating the waste to the furnace system (1, 3, 5) and for discharging the solid part, characterized in that it comprises means (2, 6) for heating the waste to 10 a temperature of at least 150 ° C in the separate chamber (9), and a comminuting device (10) for comminuting the solid portion discharged from the chamber (9) into smaller particle sizes. Installation according to claim 7, characterized in that the means for heating the waste in the separate chamber (9) comprise a duct (2) connected to either the clinker cooler (7) or the furnace system (1, 3, 5). Plant according to claim 7, characterized in that the waste heating chamber (9) is designed as a housing containing a substantially horizontal turntable supporting and transporting the waste through the chamber (9) from its inlet (11) to its outlet (8). 25 Installation according to claim 7, characterized in that the chamber (9) is constituted by a drum System according to claim 7, characterized in that the comminution device (10) is constituted by a pipe mill, a rolling mill or a roller press. Installation according to claim 11, characterized in that it comprises one or more means for removing metal parts and other undesirable components from the solid part, such as a magnetic separator. Plant according to claim 12, characterized in that it comprises a silo (16} for storing waste fuel which is heated and comminuted.