Prospekt_Preheater_en
Preheater and Calciner
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ZEMDES - Preheater and Calciner
ZEMDES cyclone preheaters and calciners are designed modular and they allow by combi-ning the different modules a consistently procedure oriented figuration. If the conditions are changing later (e.g. other raw materials and fuels or higher environmental standards) the ZEMDES cyclone preheaters and calciners can be aligned by exchanging or adding mo-dules for the respective conditions.
For example: A calciner was dimensioned for fuel oil. The conditions for the use of coal as a fuel could be created by removing standard modules and inserting Low-NOx Module for a relative simple way by concurrent reduction of the NOX contents in the exhaust gas or it shall be used for difficult inflammable alternative fuels. This requirement can also be complied by adding a combustion chamber in the available calciner.
ZEMDES cyclone preheaters could be one- or more-stringed. The one-stringed execution is used up to a throughput of 5.500 t/d. For larger throughputs, the cyclone preheaters are usually two-streamed.
The 1st stage (top stage) of each preheater is a module WEZ.D.
The module WEZ.D is a double cyclone, designed as dedusting cyclone. Characteristic features of the ZEM-DES-dedusting cyclones are:
one from the dip tube undisturbed inlet flow a long immersion depth of the dip tube a diameter ratio of cyclone and dip tube of 2: 1 270 inlet spiral with an inclined bottom surface a cyclone cone with 70 wall inclination
The dust content in the exhaust gas after preheater is max. 25 g/m. The double cyclones, including the riser ducts, are provided with a refractory lining. Therefore, a wall temperature of about 90 C will be aspired. The aspired wall temperature is independent of the used fuel. There will be no action with regard to the wall temperature with the use of alternative fuels.
ZEMDES Double Cyclone 1st Stage
ZEMDES Preheater & Calciner
Preheater and Calciner - ZEMDES
Depending on requirements of raw material drying, there are used 4-, 5- or 6-stage cyclone preheater.
For process cyclones of the stages 2 up to 6, modules of the type WPZ.X are used.
The selection of the modules is made according to each stage calculated amounts of gas out of process calculations.
The modules of the type WPZ.X are process cyclones, which are optimized in their geometry concerning high filtration efficiency and low pressure drop.
Characteristic features of the ZEMDES process cyclones are:
one from the dip tube undisturbed flow an immersion depth of the dip tube of about 50% of the height of the inlet spiral the 270 inlet spiral with an inclined bottom surface a cyclone cone with 70 wall inclination
The process cyclones, including the riser ducts, are provided with a refractory lining. In the normal case (use of standard fuels) wall temperatures of about 90 95 C will be aspired. The aspired wall temperatures are dependent of the use of fuel. There are used 4-, 5- or 6-stage cyclone preheater.
At the using of alternative fuels, it have to adapt once the used grades of refractory materials, but also the value of the wall temperatures of the cyclones on this application. At the qualities of the refractory materials, the primary intension is to avoid the destruction of the lining by diffusing pollutants. At specifying the value of the wall temperatures, the destruction of the metal shell by corrosion from the inside (below acid dew point) shall be prevented. Therefore, by using of alternative fuels, wall temperatures of about 140 170 C for the cyclones of stages 4, 5 and 6 are aspired.
ZEMDES Process Cyclones
ZEMDES - Preheater and Calciner
ZEMDES calciners ZD-C.SD are stream-duct reactors. Depending on the size of the plant, one or two calciners are used. All ZEMDES calciner can be equipped with a Low-NOx Module and / or a combustion chamber. Due to the modular design, a further upgrading can also be made by relatively little effort.
The basic concept of the flow tube reactor offers a high stage of operational safety and combining a simple design with high flexibility for changes of process parameters. The particular shape of the deflection at the top of the calci-ner provides disintegration of any remaining streak and for a complete mixing of raw meal, gas and fuel. This is the precondition for complete combustion and optimum heat transfer between gas and solids up to entering the lowest cyclone stage. Degrees of calcination of the raw meal can be achieved by up to 95%.
The Low-NOx Module operates on the principle of staged combustion. The complete Low-NOx Module consists of 2 parts. The lower section begins just above the orifice (tran-sition from the kiln inlet chamber into the calciner). In this area, a subset of fuel and for control of the temperature also a subset of raw meal of second lowest cyclone stage is offe-red. The combustion takes place substoichiometric, that means so much fuel is supplied to that in relation to the furnace exhaust gas oxygen present an air excess number () of about 0,8. There is an initial reduction of NOx-content in exhaust gas.
In the transition from lower to upper part of the Low-NOx Module, the first supply of tertiary air is carried out and the remaining task of the fuel and the raw meal of the second lowest cyclone stage. Also in the upper part of the Low-NOx Module, the combustion is substoichiometric, that means it is only so much tertiary air supplied, that a number of excess air () is about 0,8. It is a further reduction of NOx-content in exhaust gas.
At the end of the upper part of the Low-NOx Module is the second supply for tertiary air. The amount of tertiary air, which is incorporated, depends on the oxygen content which is envisaged at the end of calciner (before entering the lowest cyclone). The target is 2 3 % oxygen.ZEMDES Calciner
Preheater and Calciner - ZEMDES
To observe the limit value for the NOx- content in the exhaust gas, an additional SNCR system has to be installed mostly. The range for the injection location of the reducing agent is above the Low-NOx Module to the deflection at the top of the calciner. In this area it is expected with temperatures between 900 950 C. This temperature range is an optimum value for the SNCR process.
The complete calciner is designed so that depending on the characteristics of the fuels a gas residence time is achieved by 3,0 6,5 seconds.
The calciner is provided with a refractory lining. For the execution of the refractory lining, it is the same, which was already explained to the process cyclones. The wall temperatures should be about 160 170 C with the use of alternative fuels.
The modular whole concept of the ZEMDES preheater and calciner is designed, that at a later date an extension of the calciner or retrofit with a combustion chamber are possible options. This may be required if the characteristics of the used fuels in the future a reliab-le ignition and / or complete burn out with the original calciner-configuration is not allo-wed.
ZEMDES Preheater2 String, 4 Stage with
Low-NOX ModuleZEMDES Preheater with Tower Structure2 String, 5 Stage with Low-NOX Module
Erich-Kckert-Str. 406842 Dessau-RolauGermany
www.zemdes.com
[email protected]
+ 49 340 8704 - 290
+ 49 340 8704 - 230
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