Vertical Raw Mill Heat Balance Excel Sheet

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Contents

Vertical Raw Mill Heat Balance Excel Sheet

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PROCESS FILES

VRM HEAT AND MASS BALANCE
FLOW MEASUREMENTS	BEFORE MILL IDF	BEFORE MILL	AFTER MILL
Temperature, ^oC	83	200	86
Static pressure, mm H₂O	-1026	-95	-866
Barometric pressure, mm H₂O	10186	10186	10186
Dynamic pressure, Pd, mm H₂O	26.00	52.00	50.00
Gas density at std. cond., kg/Nm³	1.37	1.39	1.38
Gas density at actual cond., kg/Am³	0.945	0.795	0.960
Average ( Pd )^1/2	5.10	7.21	7.07
Flow area, m²	6.80	7.40	6.80
Pitot coefficient	0.734	0.734	0.734
Gas velocity, m/s	23.22	35.81	23.45
Vol. flow rate, Am³/h	568543	953983	574038
Vol. flow rate, Nm³/h	392074	545472	399412

HEAT AND MASS BALANCE of VRM (mill to cyclone)
	Date:
	Raw feed condition: Rate				265	mt/h
		Temperature			35	°C
		Moisture			5.0%
	Raw meal collected at cyclone: Rate				176.56	mt/h
		Temperature (after cyclone)			83	°C
		Moisture of mill product			0.8%
	Weight of H2O vapor from raw matls.				11,220	kg/h
	Dust going to bag house at cyclone efficiency of			70%	77218.90	kg/h	196.9	g/nm3
	Hot gas condition before mill
		Temperature			200	°C
		Pressure			-95	mmH2O
		Oxygen content			9.6%
		Volume at actual condition			953,983	Am3/h
		Volume at standard condition			545,472	Nm3/h
	Gas condition after the mill
		Temperature			86	°C
		Pressure			-866	mmH2O
		Oxygen content			11.5%
		Volume at actual condition			574,038	Am3/h
		Volume at standard condition			399,412	Nm3/h
		Volume of H2O vapor from raw mat’l			9,048	Nm3/h
	Gas condition at the mill fan inlet
		Temperature			83	°C
		Pressure			-1026	mmH2O
		Oxygen content			12.3%
		Volume at actual condition			568,543	Am3/h
		Volume at standard condition			392,074	Nm3/h

	HEAT AND MASS BALANCE of VRM

	Reference temp.		20	deg C
							Temp	Cp
	Input		Nm3/h	Mass, kg/h	Heat, kcal/h		°C	kcal/kg
	Raw material ( dry)			251,750.00	1,691,760.00		35	0.192
	Raw material moisture			13,250.00	463,750.00		35	1.000
	Dust suspended at gas from CT			5,646.33	216,819.23		200	0.192
	Hot gas from CT		545,472.11	758,206.23	36,546,631.22		200	0.241
	False air at mill		120,047.50	154,861.27	1,306,716.99		35	0.241
	False air after mill to fan inlet		62,029.22	80,017.70	675,188.09		35	0.241
	Grinding heat				2,067,526.03
			727,548.83	1,263,731.53	42,968,391.56
	Output
	New raw meal + kiln dust collected at cyclone, dry			180,177.43	2,990,945.40		83	0.200
	New raw meal + kiln dust going to baghouse,dry			77,218.90	1,281,833.74		83	0.200
	Raw meal moisture			1,453.04	120,602.64		83	1.000
	Exit gases: gas from preheater		545,472.11	758,206.23	14,985,755.22		83	0.238
		false air from raw mill	182,076.72	234,878.97	4,707,502.52		83	0.241
		H2O vapor from raw mat’l	9,513.67	11,796.96	7,491,631.08		83	0.288
	Heat loss by radiation & convection				1,024,813.39
			737,062.50	1,263,731.53	32,603,083.99
					-24.12%

	Grinding heat computation				Radiation & convection losses
		mill motor	2496.83	kw	Water evaporated		11,796.96	kg/h
		classifier motor	86.96	kw	R/C factor		11.95	kcal/kg H2O
		mill fan*	0	kw	Heat loss at the mill		140,977.01	kcal/h
		total	2583.79	kw	Heat loss at the cyclone		883,836.38
		assumed % efficiency	0.93		Total heat loss		1,024,813.39	kcal/h




	Heat Balance at Cyclone
							Temp	Cp
	Input		Nm3/h	Mass, kg/h	Heat, kcal/h		°C	kcal/kg

	Gases:	hot gas from preheater	545,472.11	758,206.23	15,527,409.02		86	0.238
		water vapor from raw matl	9,513.67	11,796.96	7,507,533.29		86	0.288
		false from at mill	120,047.50	154,861.27	3,215,952.37		86	0.241
		false air at cyclone	62,029.22	80,017.70	1,659,033.59		86	0.241
	R.meal	raw meal, dry		251,750.00	4,330,100.00		86	0.200
		dust suspended at gas from CT		5,646.33	97,116.95		86	0.200
		raw meal moisture		1,453.04	124,961.77		86	1.000
				1,263,731.53	32,462,106.98
	Output
	Gases:	hot gas from preheater		758,206.23	14,985,755.22		83	0.238
		water vapor from raw matl		11,796.96	7,491,631.08		83	0.288
		false air fr. mill to dust col.		234,878.97	4,707,502.52		83	0.241
	R.meal	new raw meal + dust collected at cyclone, dry		180,177.43	2,990,945.40		83	0.200
		new raw meal + kiln dust going to baghouse,dry		77,218.90	1,281,833.74		83	0.200
		raw meal moisture after cyclone		1,453.04	120,602.64		83	1.000
				1,263,731.53	31,578,270.60
		Radiation & convection loss (by bal.)			883,836.38


	Stoichiometric calculation fot verifying measured data:

	Volume of hot gas before the mill				545,472	Nm3/h
	Volume of H2O vaporized from raw materials				9,048	Nm3/h
	Volume of false air entering the mill (by O2 bal)				120,047	Nm3/h	16.3%
	Volume of gas leaving the mill				674,568	Nm3/h
	Volume of false air after mill to mill fan inlet (by O2 bal.)				62,029	Nm3/h	8.4%
	Volume of gas at the mill fan inlet (calculated)				736,597	Nm3/h
	Volume of gas at mill fan inlet (measured)				392,074	Nm3/h
	Difference of computed and measured volume				-87.9%	ok
	Note: Minimal difference validates computed and measured values

	Estimate of kiln dust:

	O2 at Ph exit				6.00%
	O2 at rm3 inlet			kg/h	9.60%
	Water vapor at cond. Tower			9963.6	8035.16	nm3/h
	False air			24.96%	134127.37	nm3/h
	Preheater gas volume				403309.58	nm3/h
	Kiln dust at assumed		30.00%	collection at CT	5646.33	kg/h	suspended in gas
			20	g/nm3	1882.11	kg/h	collected

	Specific volumes used

		Air	1.24	kg/nm3
		Combustion gas	1.29	kg/nm3
		Water vapor	1.39	kg/nm3

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