40-Thumb rules for sugar Cogeneration plant design

 

Objective: Design of Cogeneration plant for 5000 TCD Sugar and 60 KLPD Molasses based Distillery plant

Thumb rules for power plant design

Sl.No.	Particular	Capacity as per Thumb rule
1	Capacity of the Sugar plant	5000 TCD
2	Distillery plant capacity	60 KLPD
3	Steam required to Sugar process	Cane crushing capacity X 40% = 5000X 40% =2000 MT/day =85 TPH
4	Steam required for distillery process	Steam required for distillery process plant =Distillery plant capacity X 3.5                                                                                             = 60 KLPD X 3.5 = 210 TPD = 8.75 TPH
5	Total steam demand for sugar and distillery process	85 + 8.75 = 93.75 TPH
6	Sugar plant auxiliary Power consumption	The auxiliary power consumed per hour by any sugar plant as a Thumb rule = Cane crushing capacity X 80% X 110% =5000X80%110%=4.4 MWH
7	Employee & labour Colony power consumption	Sugar plant power consumption X 4 to 5%  =   4400 X 4 to 5% = 170-220 KWH = 0.17 to 0.22 MW
8	Power consumption of distillery plant	Sugar plant power consumption X 20-25% = 4400 X 20-25% = 0.88 to 1.1 MW
9	Total power consumption of Sugar process and related auxiliaries	Total power consumption= 4.4 + 0.22 +1.1=5.72 MWH
10	Turbine extraction steam flow	Extraction steam flow = Process steam flow + Deaerator steam flow Deaerator steam flow=Process steam flow X 10%
11	Boiler capacity	Boiler capacity = Turbine extraction steam/0.7 = = 85 + 85 X 10% = 93.5 TPH/0.7 =133.5 =135 TPH
12	Boiler fuel (Bagasse) consumption	At the average SFR (steam to fuel ratio) 2.4 Boiler bagasse consumption = 135 / 2.4 =56.25 TPH
13	Bagasse saving per day	= (Sugar mill bagasse generation-Boiler fuel consumption) X 24  = (60.42-56.25) X 24 = Appx. 100 MT/day
14	% of Bagasse saving	% of bagasse saving = 100 X 100/(60.42 X 24) =6.9%
15	Turbine capacity	Power generation in Turbine = (Bleed-1 steam flow X (Main steam Enthalpy-Bleed-1 enthalpy) + Bleed-2 steam flow X (Main steam Enthalpy-Bleed-2 enthalpy) + Extraction steam flow X (Main steam Enthalpy-Extraction enthalpy) + Exhaust steam flow X (Main steam Enthalpy-Exhaust enthalpy)) / 860   Power generation in Turbine = (8 X (828-738) + 20 X (828-703) + 93.45 X (828-645) + 14 X (828-611)) / 860 Power generation in Turbine = 720+2500+17110.5+3038 =27.17 MW Net Power generation = 27.17 X 98% X 95% = 25.29 MW = 25 MW Therefore, Turbine power generation capacity = 25 MW
16	Specific steam consumption (SSC)	SSC=Steam consumption / Power generation = 135 / 25 = 5.4
17	Specific fuel consumption (SFC)	SFC= SSC / SFR = 5.4 / 2.4 = 2.25 Kg/Kw
18	Alternator capacity/size	Alternator capacity = Turbine Power generation capacity/Power factor = 25/0.8 = 31.25 MVA
19	Lube oil system capacity calculation
19a	Lube oil pump capacity	Lube oil pump capacity in M3/Hr = Turbine capacity in MW X 2.0 That is AOP/MOP capacity = 25 MW X 2.0 = 50 M3/hr each
19b	Capacity of EOP pump	Capacity of EOP pump = Lube oil pump (AOP or MOP) capacity X 25% = 50 X 25% = 12.5 M3/hr
19c	Capacity of COP pump	Capacity of COP pump = Lube oil pump capacity (AOP or MOP) X 10% = 50 X 10% = 5 M3/hr
19d	MOT storage capacity	As a thumb rule, MOT storage capacity = Quantity of oil flow (Lube & control oil) X 225                  = (50+5) X 225 =12375 litre, can be rounded up to 12500 Litres
19e	OHOT storage capacity	As a thumb rule, Storage capacity of Overhead oil tank (OHOT) is = Main Oil tank (MOT) tank capacity X 35% = 12500 X 35% = 4375 liters, can be taken up to 4500 liters
19f	Oil cooler capacity	Oil cooler heat load = 50 M3/hr X 10 = 500 KW = 500 X 860 = 430000 kcal/hr.   Quantity of Cooling Water circulation = Heat load / Cooling water temperature difference                                                                     = 500 X 860 kcal/hr / 4 deg C X 1000 = 107.5 M3/Hr.
19g	Oil Vapour extraction fans capacity calculation	As a Thumb rule Oil vapour extraction fan capacity in m3/sec = Total oil flow (Lube & Control oil) X 9 OVEF capacity = (50+5) X 9 = 495 M3/sec and static pressure will be 250-300 mmwc
20	Capacity of export Transformer	Capacity = (Total maximum power generated-Cogen Auxiliary power consumption)  = 25 MW-(25 X 8%) = 23 MW Therefore, export transformer capacity will be 23 MW/Power factor =23/0.8 =28.75 or 30 MVA
21	Auxiliary Transformer capacity	Auxiliary Transformer capacity = Cogeneration Maximum Home Load X 120% / Power factor                                                    =25 X 12% X 120% / 0.8 = 4.5 =4.5 MVA X 2 Nos Note: Maximum APC considered is 12% and total transformers considered -2 Nos (2 X 100%) Capacity of Transformers= 4.5 MVA Out of two transformers one transformer can be used as converter (For VFD) and one as distribution transformer for other auxiliaries.
22	Boiler feed pumps capacity	Capacity of Operating Boiler feed pump = Boiler MCR X 135% So, total capacity of the feed pumps = 135 X 135% = 182.25 M3/hr   Capacity of each pump = 182.25/2 = 91.12 or 92 M3/hr Head of the pump = Boiler operating pressure X 140% = 110 X 140% = 154 Kg/cm2 or 1540 meter (Appx).
23	ID fans capacity	Capacity of the ID fan in m3/sec = Boiler capacity X / 2 = 135 / 2 = 67.5 m3/sec & Static pressure: 250-300 mmwc
24	Total combustion air required	Capacity of FD & SA fans = ID fan capacity X 80% Therefore, capacity of FD & SA fans = 67.5 m3/sec X 80% = 54 m3/sec
25	Capacity of FD fan	Capacity of FD fan = 60% of total combustion air required Capacity of FD fan = 60% X 54 m3/sec = 32.4 m3/sec & Static pressure: 250-280 mmwc
26	Capacity of SA fan	Capacity of SA fan = 40% of total combustion air required Capacity of SA fan = 40% X 54 m3/sec = 21.6 m3/sec & Static pressure: 600-650 mmwc
27	DM plant capacity	Capacity = Total losses in Power plant = 2 X 22 M3/Hr.
28	RO plant capacity	RO plant capacity = 22 X 110% = 24.2 or 25 M3/hr 2 X 25 M3/Hr
29	Main circulating cooling water	MCW water = Maximum exhaust from condensate X 70 Maximum exhaust from Turbine= Turbine inlet steam in season operation X 75% X 70% Maximum exhaust = 135 X 75% X 70% = 70.87 = 71 TPH Main circulating water (MCW) = 71 X 70 = 4970 M3/hr
30	Auxiliary Cooling water	Auxiliary cooling water required = 4970 X 8% =397.6 = 400 M3/hr.
31	Total circulating water	Total circulating water = MCW + ACW water = 4970 + 400 = 5370 M3/hr
32	Cooling tower storage capacity	Cooling tower storage capacity = Total circulating water X 25% = 5370 X 25% =1342.5 = 1345 M3.
33	Capacity of MCWP pumps	Capacity of each (3 Nos-2W+1S) main cooling water pumps (MCWP) : 4970 X 50% = 2485, can take 2500 M3/each pump
34	Capacity of ACWP pumps	Capacity of ACWP pumps = 400 M3/hr -2 Nos (1-working + 1-standby)
35	Capacity of instrumentation air compressor	As a Thumb rule: Capacity of instrumentation air compressor in m3/min = Power plant capacity in MW/4 So, Compressor capacity = 25/4 =6.25 M3/min X 2 Nos (1-Working + 1-Stand by)
36	Capacity of Service air compressor	Service air Compressor capacity = 25/4.2 =5.8 M3/min X 2 Nos (1-Working + 1-Stand by)
37	Capacity of fuel handling plant.	Capacity of the fuel handling plant would be = Bagasse generated from mill X 120% Therefore, capacity of the fuel handling plant = 60.42 TPH X 120% =72.50, can be rounded up to 75 TPH. Or Bagasse handling capacity = Boiler fuel consumption at SFR 2.4 X 130%  = (135/2.4) X 130% = 73.125, can be rounded up to 75 TPH
38	Stack or Chimney size	Stack height = 75 ID : 3.3 M OD: 3.9 M
39	ESP sizing	AS a thumb rule, ESP collection area = Flue gas flow in M3/hr / 67 ESP collection area = 270576 M3/hr /67 = 4038 M2 Specific collection area = 4038 / 75.16 =53.73, can be rounded up to 54 m2/m3/sec Flue gas velocity in ESP = 0.9 to 1 m/sec Migration velocity =8 to 9 cm/sec

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