Flat-tube heat exchangers are generally installed upstream of flat-bag filters in order to reduce the temperature of the gases to be cleaned to a temperature admissible for the filter fabric or to adjust the optimum process temperature.
During development of this heat exchanger special importance was attached to the objective to achieve a reliable continuous operation, combined with a constant cooling of gases, even in the case of high particle loads in the gas and a strongly adhesive character of these particles. Regular manual cleaning proved to be unnecessary for maintaining the heat transfer.
If necessary, we are taking additional measures to ensure a trouble-free continuous operation of the flat-tube heat exchanger and exceptionally long service lives of cooling tubes.
- Utilisation of a mechanically working cooling area cleaning device in case of presence of particles with adhesive features
- Avoidance of temperatures below the dew point by using pre-heated cooling air (cooling air re-circulation)
- Avoidance of temperatures below the acid dew point by means of injection of additive powders in the flue gas flow upstream heat exchanger
FLAT-TUBE HEAT EXCHANGERS ARE GENERALLY INSTALLED UPSTREAM OF FLAT-BAG FILTERS IN ORDER TO REDUCE THE TEMPERATURE OF THE GASES TO BE CLEANED TO A TEMPERATURE ADMISSIBLE FOR THE FILTER FABRIC OR TO ADJUST THE OPTIMUM PROCESS TEMPERATURE.
MODELS
The cooling takes place by means of indirect heat exchange between the gas to be cooled and the air taken in from the ambient air of the cooler. The gas to be cooled flows between the external surfaces of the horizontally located cooling tubes either from the top to the bottom and/or from the bottom to the top. A part of its heat is transferred to the cooling air flowing inside of cooling tubes. By means of re-circulation of a part of the cooling air and, if necessary, additional additive powder injection into the gas, it is, if essential, ensured that the water and/or acid dew point near the walls charged by the gas will not be undershot. Corrosion and caking are avoided.
In case the particles tend to be adhesive, the heat exchanger will be provided with a cleaning device, running in automatic operation during charging of heat exchanger. Chains are slowly moving to and fro between the flat-tube rows. In doing so, the thickness of particle layer deposited on the flat-tubes will be limited.
The length of horizontally installed flat-tube cooling elements is limited to max. 2,800 mm. They are installed in the cooler housing in such a way that they can each be exchanged separately.
The cooling tubes are installed in perforated plates located on both sides of the cooler housing. Special sealing between the flat-tubes and the perforated plates help to avoid leakage between the gas to be cooled and the cooling air. The design of sealing allows the trouble-free compensation of a temperature-related expansion of cooling tubes.
CONSTRUCTION
HEAT
RECOVERY /
TRANSFER
On request, various possibilities of heat utilisation are available, e.g. in the form of hot water production. If required, the gas purified in the filter arranged after the heat exchanger can be used as cooling gas. This form of heat displacement around a filtering separator is used, for example, if a catalyst for NOx reduction is installed downstream of the filtering separator.
LÜHRFILTER
IN BRIEF
LÜHRFILTER develops products and procedures for sustainable air pollution control worldwide. The family-owned company founded in 1938 offers efficient and intelligent solutions for the plant construction in nearly all fields of industry.