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Limestone Integration System

The power plant with CFB boiler always applies internal and external simultaneous desulphurization way.Our internal and external desulfurized limestone preparation integration system has been widely used power plant with CFB boiler,which can achieve the application of “one system two finished product”.

Internal And External Desulfurized Limestone Preparation Integration System

Desulphurization way of power plant with CFB boiler is diversified. WFGD desulphurization way can be used singly, but its construction cost and running cost are too high and it cannot exert the advantages of CFB boiler; internal desulphurization way can be used solely, while as the coal used in CFB boiler is inferior coal or coal gangue generally, the sulfur content is high and cannot meet worsening desulphurization emission standard.


In allusion to such situation, the power plant with CFB boiler always applies internal and external simultaneous desulphurization way. Firstly, about 80% of sulfurs will be removed in furnace by means of calcium injection; secondly, semidry shedding, wet desulphurization, ammonia-based desulphurization and other methods will be applied in order to meet desulphurization requirements under the circumstance of optimum running cost.


Limestone for internal desulphurization applies those with particle size not larger than 1mm and d50=0.35; external wet flue gas desulphurization applies the limestone with specification being -250 meshes or -325 meshes. If using traditional desulphurization way, ZMJ Column Mill System will be used to grind the limestone for internal desulphurization and ball mill or SXLM Vertical Mill or other equipment will be used to grind the limestone for external desulphurization in the meantime. Such way needs two sets of equipment systems and both investment and floor area are large, so it's not the optimum or reasonable grinding solution.


In allusion to the power plant using two desulfurizing agents at the same time, Shenxiang Machine transformed and developed internal and external desulfurizing grinding integration system on the basis of original ZMJ Column Mill System. It's able to realize the production process solution of two products with one set of system by means of adjusting the mill to increase fine powder output on the basis of original ZMJ Column Mill System and adding a Multistage Sand Separator to separate 325-mesh fine powder. At present, this solution has been applied to Huadian Shuozhou 2*300MW Power Plant and other dozen of power plants, takes on a steady production effect and saves a large number of investments and running costs.


Description on process flow:
1. First stage---raw material conveying and storage
The bar valve under feed hopper will be opened after raw material, limestone is unloaded into feed hopper via forklift or feeding truck, the limestone will fall on belt conveyor, then is transmitted to 1# elevator and finally is hoisted to buffer silo.


2. Second stage---grinding

Limestone falls to metering belt conveyor from buffer silo and then is transmitted to ZMJ Column Mill for grinding after magnetic separator by self-discharging iron remover; grinded materials will be transmitted to 2# elevator via airtight elephant trunk and then hoisted to primary classifier (PL Air Classifier).


3. Third stage---product classification

Materials transmitted to primary classifier (PL Air Classifier) will be separated with natural wind with certain strength from circulating fan; qualified powder will be transmitted to high-efficiency cyclone collector for further separation and then fall on 3# elevator. Then qualified powder will be hoisted to secondary classifier (Multistage Sand Separator) and coarse powder desulphurized internally and fine powder desulfurized externally will be separated owing to centrifugal force caused by rotors in secondary classifier (Multistage Sand Separator). Coarse powder will fall to internally desulfurized limestone powder chamber for storage and fine powder will be conveyed to externally desulfurized limestone powder chamber for storage by sealed belt conveyor.

In addition, coarse particles separated by primary classifier (PL Air Classifier) will be conveyed back to belt conveyor and then sent to feeding inlet after magnetic separator for secondary circulating grinding in ZMJ Column Mill.

Limestone powders treated with Bag Filter will be sent to externally desulfurized limestone powder silo directly via elephant trunk for storage as qualified finished products.


Characteristics and advantages:
1. Low power consumption: compared with overseas hammer or impact crusher system and domestic rod mill system, its power consumption falls by 1/3.
2. Less abrasion: compared with overseas relevant preparation system, the wear part consumption is only 1/10 and the service life of wearing parts is longer than 10000h.
3. High quality: running normally without malfunction basically, high serviceability.
4. Excellent performance: particle size of desulfurizing agent meets curve requirements of boiler basically. It's the best product at home and abroad at present.
5. Eco-friendly: noise is lower than 80dB and the system runs under negative pressure without dust.

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