Module 13. Estimation of cost and energy in product manufacture in food processing plant, sources for setting up of milk plants
Lesson 30
ESTIMATION OF ENERGY UTILIZATION FOR MANUFACTURING MILK PRODUCTS
30.1 Introduction
Dairy industry consumes considerable amount of energy in processing of milk and milk products. The developing nations of the world will quadruple their energy consumption by 2025. With the increase in demand for energy, 80 percent will still be met by the non-renewable sources like oil, coal and natural gas whereas only 20 per cent by renewable sources and nuclear power. India has the highest cost of energy in the world and is one of the very few countries, which pay more than 1 USD per litre of petrol (Hattangady, 2005). There are wide variations in the specific energy consumption by different dairy plants in India. Due to present energy crisis and limitation of the non-renewable energy sources, the price of all kinds of fuels is increasing rapidly which increases the cost of processing. Therefore, economic and judicious use of energy is an urgent need of the day for realizing high returns from manufacturing milk products.
The continuous estimates with respect to energy utilization for manufacturing dairy products are essential and useful for the management to take right decisions for product manufacturing, policy and planning purpose. The present lesson is based on a empirical study conducted in a dairy plant in North-eastern part of Haryana.
30.2 Sections of Milk Plant
The service block of the plant comprises of boiler section, generator room, electrical sub-station, refrigeration section, water supply, water softening plant, compressed air supply system, quality control section, workshop and an effluent treatment plant for removal of pollutants from waste disposal water from the plant.
30.2.1 Boiler section
Boiler is an essential and integral part of the utility section as it produces and supplies steam for performing different operations like heating of milk and cream, heating water for cleaning and sanitation, ghee manufacturing, heating of ice-cream mix and for heating water for general cleaning purposes. Boiler is separately installed in the utility section.
30.2.2 Power generation
It is essential to have a Diesel Generating (DG) set for a milk plant keeping in view the perishable nature of milk and milk products. The milk plant has its own generating set (250 KVA) to meet the requirement of power by generating electricity during the power failure from the State Electricity Board.
30.2.3 Electrical sub-station
Electricity is the most essential input to the dairy industry. State Electricity Board supplies electricity to dairy plant. At the sub-station, High voltage (11 KVA) is supplied and is stepped down through a step down transformer to low voltage (440 volts) to avoid line losses.
30.2.4 Refrigeration section
Refrigeration, which is a process of extraction of heat from a substance to lower down the temperature to the desired level than that of the surroundings, is one of the most important operations in dairy industry. Milk and milk products are highly perishable in nature and need lower temperature for storage in order to restrict the microbial growth and action. The refrigeration unit is equipped with four ammonia vapour reciprocating compressors. Chilled water is supplied through the ice bank unit to the production block for different cooling operations.
30.2.5 Workshop
The plant has its own workshop near the production block equipped with all the facilities required for day to day maintenance. The function of the workshop is to provide services of mechanics for repairing and regular maintenance of the equipments and machinery.
30.3 Data and Methodology of the Study
30.3.1 The data
The actual observation method was used to obtain information on consumption of water in different sections of the plant, steam condensation recovery during products manufacturing, , temperature on various stages of production. The personal discussion and interview method was used to get information on electricity consumption in different sections of the plant, offices and consumption in streetlights. Discussions were held with the machine operators and incharge of different sections. fuel used in boilers, generators and other sections, spare parts, sundry items, electricity bills, telephone bills Interest paid on loans other recurring expenditures of the plant, chemicals used for testing of sample in the quality control section, running hours of different machines, capacity of the motors, current and voltage drawn by the motors fitted with different equipments from the log book maintained by different section or units.
30.3.2 Estimation procedure for energy and refrigeration load
Steam requirement, Electrical energy, Coefficient of Performance and Refrigeration use, were worked out as below:
Steam requirement
Where,
M = quantity of the product to be heated (kg.)
S = Specific heat of product
T = Temperature difference (T1–T2, initial and final temperature of the product in centigrade)
L = Latent heat of steam (Ahmed, 1997)
Electricity
Consumption
Electricity power under single-Phase system:
Electricity power under three Phase system:
Where,
VL = Line voltage, IL = Line Current, Cos ∅ = power factor assumed 0.8 (Theraja, 1992)
Refrigeration load
Refrigeration load = M×S×T
Where,
M = Quality of product to be cooled
S = Specific heat of the product
T = Temperature differences in centigrade (T1-T2)
30.4 Energy Utilization
30.4.1 Electricity consumption
The electricity consumption in different sections of the milk plant was estimated and is summarized in Table 30.1. Among different sections of milk plant, half of the electricity (50.47%) was estimated to be consumed in the refrigeration section. However, Hattangady, (2005) reported that 70 per cent electricity is consumed in the refrigeration section of a plant. The possible reason for less electricity consumption in the refrigeration section reported in the present study may be due to the coefficient performance (COP) of the compressors of refrigeration section being found excellent. After the refrigeration section, the highest electricity was consumed in pasteurization section (21.39%) followed by Effluent Treatment Plant (7.25%), Miscellaneous (6.92%), Boiler section (6.10%), Water supply (3.83%), Ghee (2.12%), Sweet Flavoured Milk Section (1.70%) and less than one per cent was observed in rest of the sections of milk plant.
Table 30.1 Section-wise Electricity Consumption in Milk Plant
|
Sections of milk plant |
Electricity consumption (Units) |
Electricity consumption (%) |
|
Refrigeration section |
747135.20 |
50.46 |
|
Milk Pasteurization and packaging |
316569.67 |
21.39 |
|
Effluent Treatment Plant |
107259.26 |
7.25 |
|
Miscellaneous* |
102479.92 |
6.92 |
|
Boiler section |
90297.70 |
6.10 |
|
Water supply |
56693.84 |
3.83 |
|
Ghee section |
31412.77 |
2.12 |
|
Sweet Flavoured Milk (SMF) |
25098.22 |
1.70 |
|
Dahi section |
1051.00 |
0.07 |
|
Lassi section |
949.00 |
0.06 |
|
Quality Control section |
829.09 |
0.06 |
|
Paneer section |
525.60 |
0.04 |
|
Total Units consumed during the financial year 2003-04 |
1480301.27 |
100 |
Miscellaneous* include electricity consumption in streetlights, canteen, security room, seminar room, toilets and common stores.
30.4.2 Refrigeration and steam requirement
The information in Table 30.2 revealed that the refrigeration requirement during the manufacturing process of pasteurized milk was estimated as 61.35 kilocalories/ litre, followed by, Lassi (46.90 kilocalorie/1000ml), Dahi (46.70 kilocalorie/1000ml) and Paneer (45.49 kilocalorie/kg). The steam requirement was calculated during the process of product manufacturing. However, the steam used for miscellaneous operations like cleaning of equipments and washing of trays etc. was calculated separately distributed among the products on the basis of fat contents in the products. The steam requirement for manufacturing products in the plants where recycling of condensate steam is there, the requirement of steam is lower than that of the plant operating without recycling technology. The stream requirement depends on the temperature of milk received at the time of manufacturing products and process of production. In the present study, the actual temperature at which the milk was received, temperature of semi finished material and temperature of the milk or material heated for manufacturing different products was recorded by taking the personal observations. As evident from, table 30.2, the steam during the pasteurization of milk was estimated to be 0.12kg/ litre, and for manufacturing of products was observed 0.26/ kg for Ghee followed by Sweet Flavoured milk (0.21kg/1000ml), Paneer 0.16kg/kg, Dahi (0.15kg/1000 ml) and Lassi (0.15kg/1000ml).
Table 30.2 Refrigeration and steam utilization during product manufacturing
|
Product
(1) |
Refrigeration utilization (kilocalorie/unit) (2) |
Steam utilization (kg / unit) (3) |
|
Pasteurized Milk (lit.) |
61.35 |
0.12 |
|
Ghee (kg.) |
- |
0.26 |
|
Sweet Flavoured Milk (1000ml) |
- |
0.21 |
|
Paneer (kg) |
45.49 |
0.16 |
|
Dahi (1000ml) |
46.70 |
0.15 |
|
Lassi (1000ml) |
46.90 |
0.15 |
30.4.3 Condensate recovery
Condensate recovery is the flow of hot water which is left after the steam is circulated in the double jacketed equipments during products manufacturing. Condensate recovery was estimated by taking actual observations for milk pasteurization process, Paneer and Ghee manufacturing process. Due to the non-availability of space under the unit, it was not possible to take the observations and estimate the condensate recovery for manufacturing Sweet Flavoured Milk. During pasteurization of milk, the average quantity of condensate recovery was observed to be 118.63 kg/hour at an average temperature of 71°C, in case of Paneer manufacturing, the quantity to be 237.24 kg./ hour at an average temperature of 70°C followed by Ghee making( Condensate recovery was 68 kg. /hour at an average temperature of 90.5°C.
Table 30.3 Steam condensate recovery during manufacturing of milk product
|
Production |
Av. Quantity of process Condensate (kg/hour) during process |
Av. Temperature of Condensate |
|
Milk pasteurization |
118.63 |
71.00°C |
|
Paneer manufacturing |
237.24 |
76.00°C |
|
Ghee manufacturing |
68.00 |
90.50°C |
Conclusions
Among different sections of milk plant, about 50% of the electricity was consumed in the refrigeration section only. The pasteurization and pouch filling section was the next major section, which consumed 21.39% electricity followed by effluent treatment plant (7.25%). The study further pronounced that 37,925 units of electricity were estimated to be consumed during financial year 2003-04 due to the lights provided in different sections of the plant, streetlights and the other surrounding the plant. There is a scope to reduce the electricity consumption by the replacing the incandescent lamps, sodium vapour lamps and fluorescent tubes fitted in the plant with the Compact Fluorescent Lamps (CFL) as a 15 watt CFL consumes 75 % less electricity than the incandescent lamp (Bureau of Energy Efficiency). The findings revealed that the condensate recovery in milk Pasteurization, Paneer manufacturing and Ghee manufacturing process was 118.63, 237.24 and 68 kg/hour, respectively ranging between 71°C to 90°C, which was not being recycled and drained. If the waste condensate is reutilized, there will be saving in soft water as well as thermal energy.
Selected references
Ahmed, Tufail 1997. Dairy plant engineering and management, IVth Edition., Allahabad: Kitab Mahal, 48-51.
Chauhan, A.K. , Singh Rajvir, Sirohi Smita, Lal Girdhari 2007 .Cost of product manufacture and energy utilization in milk plant – A methodological study, Research Bulletin , NDRI Publication No.30/2007 :1-43.
Hattangady Hema 2005. Energy efficiency in the dairy industry. Indian Dairyman, 57 (12):151-153.
Theraja, B.L. and Theraja, A.K.1992. A text book of electrical technology. S. Chand and Company Ltd, New Delhi, p-469.