A mixture of natural talc and borax is obtained via surface mining techniques an

Question

A mixture of natural talc and borax is obtained via surface mining techniques and is delivered in open-top trunks to the plant site. At the plant side it is crushed by large jaw crushers into pieces no larger than 10-15cm. The material then goes to a roller mill to further reduce the size. After passing through the roller mill, the material is screened; material smaller than 1 cm is stored for drying and larger material is recycled for further crushing.

The material that passes the screening step is conveyed to storage silos; from there is goes to alarge rotary kiln dryer where it is dried from 8% moisture to 0.2%. The moist solids feed rate to the dryer is 50,000 kg.hr. The rotary kiln is fired with a low sulfer fuel oil at a rate of 6.0 liters of fuel per 1000kg of feed.

The dried product is passed through an air contact cooler, and is then stored before shipment. The exhaust gases leave the dryer at 650 degrees F. The dusty gases exciting the dryer must be treated by approprate control equipment before being exhausted to the atmosphere.

For the more problems answered I can add more points to this question.

Any help on any or all of the problems will be very much appreciated. Thanks!

First Requirement Complete the following material balance table and answer the question that follow. Some additional data are given as follows: fuel oil specific gravity = 0.90 fuel oil composition (weight percent): C = 88%; H = 11.7%; S = 0.3% Kiln particulate emissions = 2.0% of dry solids feed rate combustion air supplied per Kg of fuel = 18 Kg/Kg auxiliary air supplied per kg of moist solids feed = 0.30 kg/kg inlet air composition (mole percent): N2 = 78% 02 = 21% Ar = 1% 1. Calculate the mass emission rate of particles from the dryer, in kg/hr. 2. Calculate the percentages of the raw feed that are lost in the crushing step and in the drying step. 3. Calculate the mass emission rate of SO2 from the dryer, in kg/hr. 4. Calculate the concentration of particles emitted from the dryer, in microg/std m3. 5. Calculate the concentration of S02 in the exhaust, in microg/std m3 and in ppm. 6. If emission limits require that less than 10 kg/hr of particles be emitted, calculate the required efficiency of the collection system. 7. Calculate the volume percent of moisture in the exhaust gases. 8. Calculate the exhaust gas flow rate, in dry std m3/hr and in acfm. 9. Calculate the volume ,percentages of C02 and O2, in the exhaust gases on a dry basis.

Explanation / Answer

Material balance table :

1.)Dry solids : 52-4.17 = 47.83kg/hr

2.)Complete

3.)0.9*6000/1000*52*0.003 = 0.8424kg/hr

4.) Inlet air : wt % : N2 = 0.78*28/(0.78*28+0.21*32+0.01*40) = 0.754, O2 = 0.232, Ar = 0.014

Feed rate : N2 = 0.754*18*52= 705.744 kg/hr, O2 = 217.15200kg/hr. = 13.104 kg/hr

Total = 18*52 = 936 kg/hr

5.) Auxillary air = 0.3*50000 = 15000kg/hr

6.)2% of dry solids => 0.02*46 =0.92 kg/hr and division similar to Inlet air by wt. %.

a.) Fuel oil specific gravity = 0.9=> fuel oil rate = 6000 * 0.90 = 5.4 kg/1000kg of feed.

Everything else is just calculations, hope you can proceed from here.

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