MX2008001905A - Method for preheating cement raw meal, and method for carrying out said method - Google Patents

Abstract

Disclosed is a method for preheating raw meal used for producing cement clinker. According to said method, the raw meal is conveyed to the input end of a clinker kiln (1) counter to the flow of hot gases in at least one heat exchanger leg (3, 4), the hot gases being discharged via at least one first heat exchanger (2) that is connected to the input end of the clinker kiln (1) and heat exchanger legs (3, 4) which adjoin said first heat exchanger (2) and are disposed parallel to each other. The inventive device used for carrying out the disclosed method is characterized in that heat exchanger legs (3, 4) that are arranged parallel to each other are connected to at least one first heat exchanger (2) which is joined to the input end of the clinker kiln (1).

Description

METHOD FOR PRE-SALE OF PURE CEMENT DUST AS WELL AS A DEVICE TO CARRY OUT SUCH METHOD The invention relates to a method for the preheating of pure cement powder for the production of cement-clinker, in which the pure cement powder is transported to the feed side of a hydraulic cement clinker furnace (1) at less a line of heat exchangers in counterflow to hot gases as well as a device for carrying out said method.

In the production of hydraulic cement clinker of pure cement powder it has already been proposed to preheat at least one line of heat exchangers and, in particular, in cyclonic / fluidized-bed heat exchanger systems which is traversed by the malodorous gases of a rotary kiln, in which preheating and, at an appropriate temperature, also precalcining can be carried out. In this way, the hot malodorous gases from the rotary kiln can be used thermally whereby the cyclonic / fluidized bed exchangers normally used for this purpose have dimensions for defined amounts of the treatment capacity. It is known that a plurality of such cyclonic / fluidized-bed heat exchangers is connected in series so that the hot process gas leaving the rotary kiln at temperatures of plus or minus 1100 ° C is cooled in several stages to temperatures of 350 ° C or even at 290 ° C, depending on the number of steps. The number of steps in turn usually depends on the drying requirements of the material respectively used so that the efficiency of the heat transfer is generally determined by the dispersion of the pure powder in the stream and an appropriately high degree of separation in the the Cyclon. The temperature gradient as well as, as the case may be, the losses from the radiation and the actual contact time in each case have a natural influence on the heat transfer.

With large rotary kilns or appropriately larger production capacities, appropriately larger preheater is required in order to protect the continuous feed of the rotary kiln. For this purpose, it has already been proposed to operate two lines of heat exchangers in parallel to protect the feeding of the material in the rotary kiln through appropriate gutters. When the required amount of treatment capacity is further increased such a concept necessarily leads to natural limits. Although the conventional lines of fluidized bed heat exchangers have dimensions for a treatment capacity of 3500 to 4000 t per day and can be operated with cyclones established in a large appropriate separation and with an appropriately low pressure drop, the excessive placement in parallel of such installations leads to problems as to the space that is needed in the rotary kiln feeding section. When more such lines are used, a logistical complication occurs at the feed end of the rotary kiln since, in addition to the more than two feed gutters, other feed gutters are needed for the lifting of the clinker kiln that is connect equally in this place. Therefore, when larger amounts of treatment capacity are demanded, this would necessarily lead to appropriately larger fluidized bed heat exchangers in dimensions and, in particular, to larger cyclones with diameters of 12 meters or more, which would have to be used, so the enlargement is necessary in order to keep the pressure drop limited for an economic operation. However, heat exchangers of this great magnitude are not stable in their operation, like the established standard size heat exchangers that are used up to now. An appropriate enlargement of the number of heat exchanger lines runs in parallel to one another, however, it leads to problems in the design of the feeding gutters, as mentioned initially, and in particular, due to the need to continuous and correct need, the feeding has to be carried out at specific angles in order to protect the passage of the material to the rotary kiln.

Therefore, it is an object of the invention to increase the amount of treatment capacity of the heat exchanger without the occurrence of a greater pressure drop and, therefore, a higher power consumption in this stage so at the same time The separation properties of the known installation must be maintained to the greatest extent unchanged. To solve this object, the method of the invention which leaves the initially mentioned method normally consists in it, in that the hot gases are extracted through at least one heat exchanger connected to the feed end of the clinker furnace of Hydraulic cement and through the heat exchanger lines follow this first heat exchanger and they are placed in parallel with each other. By making a division in the following heat exchanger lines that are placed in parallel with each other after at least a first heat exchanger connected to the feed end of the hydraulic cement clinker furnace, it is possible to operate the respective branches with falls of generally equal pressure and reduce the number of feed gutters at the feed end of the rotary kiln appropriately. The duplication of the branches after the first heat exchanger allows the duplication in the amount of treatment capacities with heat exchangers in the individual lines normally have the same dimensions without the occurrence of complex construction problems at the feed end of the rotary kiln .

Advantageously, the method in this case is, however, carried out in such a way that the hot gases are extracted through cyclone / fluidized-bed heat exchanger lines in which the first cyclonic / fluidized-bed heat exchanger in Each case has a larger volume compared to the heat exchangers of the subsequent lines of cyclonic / fluidized-bed heat exchangers, by means of which it is protected from the currents of a pure powder coming from the heat exchanger lines in parallel to each other, can be processed reliably in the first stage and can be transmitted without interruption.

The device of the invention for the heating of the pure cement powder for the production of hydraulic cement clinker, which has at least one line of heat exchangers to feed the pure powder of cement in counter current with the hot gases that are extracted through the line of heat exchangers it is generally characterized that the heat exchanger lines placed in parallel with each other are connected to at least a first heat exchanger attached to the hydraulic cement clinker furnace feed end. Such construction allows to have the overall height of the preheater appropriately low and to employ in a uniform manner the heat exchangers that are distinguished by the standardization and appropriate reliability. The only construction modification in such a device is generally limited to the fact that the first heat exchanger has a larger volume than the heat exchangers that run in the direction of the flow of the heat gases. At present, the construction of the feed gutter and the feed end of the rotary kiln need not be modified so that at present it can also become a resource for the established constructions. The slightly higher pressure drop that comes with the enlargement of the first heat exchanger can be balanced through the following heat exchanger lines placed in parallel with each other whereby the embodiment of the invention is advantageously conferred so that The heat exchangers are formed as cyclonic / fluidized-bed heat exchangers.

In order to avoid the problems initially mentioned with the construction of the feed gutter, the embodiment is advantageously designed in such a way that at most two cyclonic / fluidized-bed heat exchangers are connected to the feed gutter for the precalciner and / or the clinker furnace, for which two lines of heat exchangers are connected in each case, so that the cyclones connected to the feed gutter of the clinker furnace preferably have a larger diameter than the cyclones that run along the length of the furnace. line derived in the direction of flow of hot gases that are extracted. The derivative line leaves the respective manifold of the heat exchanger lines connected to the feed gutter or the clinker furnace through the first heat exchanger.

The invention will now be described in greater detail through an exemplary embodiment illustrated in the drawing. The schematic drawing shows a rotary kiln 1 to which two cyclonic / fluidized-bed heat exchangers are connected. These two first cyclonic / fluidized-bed heat exchangers are connected in each case with two lines 3 or 4 of standard cyclonic / fluidized-bed heat exchangers 5 by means of which above the cyclonic / fluidized-bed heat exchangers 2 an appropriate derivative line, which is indicated schematically with the number 6, is provided. The individual cyclonic / fluidized-bed heat exchangers 5 can have the dimensions set and a construction by which by doubling the lines the overall construction height is appropriately reduced and the energy consumption can be minimized by an appropriate choice of number of stages.

Claims (7)

1. Method for preheating pure cement powder for the production of cement-clinker, where the pure cement powder is transported to the feed side of a hydraulic cement clinker furnace (1) in at least one line of exchangers of heat in backflow with the hot gases characterized in that the hot gases are extracted through two first heat exchangers (2) connected to the feed end of the hydraulic cement clinker furnace (1) and through two lines of heat exchangers (3,4) which run along these first heat exchangers (2) in each case and which are parallel to each other, wherein the first two heat exchangers (2) have a greater volume in comparison with the heat exchangers (5) that follow in the direction of the flow of hot gases.

2. Device for preheating pure cement powder for the production of hydraulic cement clinker that has at least one line of heat exchangers (3,4) formed by cyclonic / fluidized-bed heat exchangers to feed pure powder of cement in countercurrent with the hot gases extracted through the line of heat exchangers (3,4), characterized in that at least the first two heat exchangers (2) connected to the feed end of the hydraulic cement clinker furnace (1) connect two lines of heat exchangers (3,4) placed in parallel with each other in each case, whereby the first two heat exchangers (2) have a higher volume compared to heat exchangers (5) ) that follow the direction of the flow of hot gases.

3. Device according to claim 2, characterized in that the first two cyclonic / fluidized-bed heat exchangers (2) are connected to the feed gutter for the precalciner and / or the clinker oven, to which two are connected. lines of cyclonic / fluidized-bed heat exchangers (3,4) in each case.

4. Device according to claim 2 or 3, characterized in that the cyclones (2) connected to the feed gutter of the clinker furnace have a larger diameter than the cyclones (5) that follow the line derived in the direction of flow of the hot gases that are extracted.

5. Device according to claim 3 or 4, characterized in that the heat exchangers (2.5) are formed as cyclonic / fluidized-bed heat exchangers (2,5).

6. Device according to claims 3, 4 or 5, characterized in that at most two first cyclonic / fluidized-bed heat exchangers (2) are connected to the feed gutter for the precalciner and / or the clinker furnace, to which two lines of cyclonic / fluidized-bed heat exchangers (3,4) are connected in each case.

7. Device according to any of claims 3 to 6, characterized in that the cyclones (2) connected to the feed gutter of the clinker furnace have a larger diameter than the cyclones (5) that follow the line derived in the direction of flow of hot gases that are extracted.