Patent Application
20130277471
This application claims the benefit of the German patent application No. 10 2011 008 967.5 filed on Jan. 12, 2011, the entire disclosures of which are incorporated herein by way of reference.
The invention relates to a plant for producing cement, having a first stage for crushing raw material to form raw powder, a second stage for calcining and sintering the raw powder to form cement clinker, a third stage for cooling the sintered cement clinker, and a fourth stage for crushing the sintered cement clinker.
To produce cement from raw material, a mixture of known composition made of lime-containing rock as raw material firstly passes through a raw powder mill in a first stage, where the raw material is crushed to form raw powder. During the crushing, the raw material undergoes first drying and, in a following second stage, the raw powder is subjected to a heat treatment, firstly CO2 being expelled from the lime-containing rock, formally from the rock powder. Then, in the methods normally used, the rock powder de-acidified in this way is sintered in a rotary kiln, desired calcium silicate phases being formed at high temperature while sintering the individual raw powder particles. In a subsequent step, as third stage, the sintered material is cooled down suddenly in order firstly to feed the heat present in the sintered material back into the process but also to assist the silicate phase formation during quenching. The cooled cement clinker is then temporarily stored and, to produce cement, the cement clinker is ground with additives in a fourth stage to form fine cement powder.
Viewed overall, the cement clinker produced from the raw state as raw material as far as the finished cement passes through crushing at at least two points. Consequently, in a plant for producing cement, it is necessary to maintain at least two grinding installations, which possibly operate differently.
Furnishing different grinding systems requires high logistical effort. Not only is it necessary for different spare parts to be stocked but it is also necessary for the different grinding systems, which not infrequently originate from various providers, to be maintained with different aids and repaired in the event of damage. The necessary stoppage of the various grinding systems during maintenance or repair results in stoppage of the plant, as a result of which the operator must accept high stoppage costs.
In order to avoid the stoppages, it is known to furnish redundant grinding systems in order that these can replace one another when a grinding system is being maintained or repaired. This leads to overcapacity in grinding output in the plant, which is associated with high costs.
It is therefore an object of the invention to avoid the necessary stoppages during maintenance and repair.
The object of the invention is achieved in that the first stage for crushing raw material to form raw powder and the fourth stage for crushing the sintered cement clinker are combined structurally.
Further advantageous refinements of the invention are specified in the sub-claims.
What is advantageous in the invention is that the grinding systems of the various stages, i.e. the first stage of grinding the raw material to form raw powder and the second stage of grinding the cement clinker with additives, are carried out in a structurally combined grinding unit. If one of the grinding systems of the grinding unit combined structurally has to be stopped, the other grinding system of the structurally combined grinding unit can continue to operate, in order to avoid a plant stoppage. During a partial stoppage of the structurally combined grinding unit, the grinding system still in use can be operated alternately, wherein the grinding system still in use grinds raw material to form raw powder in a first operating phase and grinds cement clinker with additives in another operating phase. If the structurally combined grinding unit comprises a plurality of individual grinding systems, for example a battery of mutually identical or similar grinding systems, it is also possible to connect up different grinding systems variably, depending on the required capacity, to form differently configured grinding systems which, although they operate with a lower grinding output, make it possible to avoid a plant stoppage, since the plant operation can be maintained with a lower production output.
In known plants for producing cement, operators place great value on keeping the expenditure on transport as low as possible. Therefore, in the known grinding plants, the separators which are needed for circulating grinding operation are arranged in the immediate vicinity of the grinding system respectively provided for the purpose. In order to avoid heat and pressure losses during the transport of the gases available out of the process, which are needed for separation in the circulating grinding system, in known plants both the individual mills for the raw material and the mills for the cement are therefore placed at different locations in the plant. However, the advantage obtained here of energy saving and avoiding the transport of the ground material in the grinding circuit is negated by the regular stoppages of the plant during maintenance of the individual grinding systems. Counter to the knowledge that has previously been widespread, a changed configuration of a plant for producing cement is therefore proposed.
The invention will be explained by using the following
FIGURE, in which:
The raw powder 120 emerging from the separator 130 with the waste gas 131 from the following heat exchanger 140 is introduced, via a separating stage 150 for separating raw powder and gas, into the heat exchanger 140, where it passes through the second stage 160 for calcining and sintering in gas countercurrent. The processes proceeding in the second stage 160 have been documented comprehensively and those skilled in the art are required to view the relevant literature. After the sintered cement clinker 170 has emerged from the rotary kiln 165 into the clinker cooler as third stage 180, said clinker is cooled down quickly in the cooler and the cooling air 182 heated during cooling is led back into the rotary kiln 165 as secondary air. In
According to the invention, provision is made for both the cement clinker 172 with further additives and for the raw material 110 to be crushed by mutually identical or similar high pressure roller presses 116, 212, which are structurally combined. Here, the separator 200 is separated structurally from the high pressure roller press 212 of the fourth stage 210.
If, as a result of maintenance of individual high pressure roller presses 116, 212, it is necessary to stop the latter temporarily, by means of the plant configuration presented here it is possible to switch the high pressure roller presses 116, 212 at the location thereof as needed such that a stopped high pressure roller press 116, 212 is replaced by a further high pressure roller press 116, 212 at the same location. This mutual replacement is possible only as a result of the high pressure roller presses 116, 212 such as are currently used and which are able to grind both raw material with another material property and also cement clinker with additives to form fine powder.
Provision is made for the separator 130 for crushing the raw material and the separator 200 to be arranged at different points in the plant 100. The ground material 117 from the first stage 115 to be transported in the circuit, and the ground material 175 from the fourth stage 210 to be transported in the circuit must be transported by suitable transport means as a result. Therefore, increased expenditure on transport within the plant 100 is accepted. Since the economic disadvantage of this increased transport expenditure is compensated for by the economic advantage of a reduction in the stoppage times of the plant during maintenance and repair of the grinding plant, this plant configuration has proven to be advantageous.
As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 008 967.5 | Jan 2011 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/050069 | 1/4/2012 | WO | 00 | 6/28/2013 |
