Food-Processing-Plant-Design-layout

Food Processing Plant Design & layout
5.2 Food plant utilities
The principal plant utilities in a food plant are process water, process steam, electric
power for motors and lighting, and fuel.
5.2.1 Process Water
Process water is required for washing the raw materials and for various cooling operations.
In fruit and vegetable processing plants, water may be used for transportation (fluming) of
the raw materials from receiving to processing areas. Water used in steam boilers may
require ion exchange treatment to reduce its hardness. Total water requirement in fruit and
vegetable processing may range from 5 to 15 m3 / ton of raw material.
5.2.2 Steam
Steam boilers are needed in most food processing plants to provide process steam, used
mainly in various operations, such as heating of process vessels, evaporators and dryers,
sterilization, blanching, and peeling. A medium size food plant (80 tons / day raw material)
may require a boiler producing about 10 tons/h of steam at 18 bar pressure.
Two principal types of steam boilers are used in the food processing industry, i.e. the firetube
and the water-tube boilers. The fire tube boilers operate at relatively lower pressure
(1–24 bar) and produce cleaner steam. The water- tube units operate at higher pressures
(100–140 bar) and they are suited for co- generation, i.e. electrical power and exhaust steam
of lower pressure for process heating. Co-generation is economical in large food plants,
requiring large amounts of low-pressure steam, e.g., beet sugar plants.
A standby steam boiler of proper capacity may be necessary to provide process steam
during any boiler failure or breakdown.
Steam boilers are rated in Btu/h, kW or boiler HP (1 Btu/h = 0.293 W, 1 boiler HP = 9.8
kW). The heat flux in the boiler heating surface is about 0.75 kW/ m2. The boiler efficiency
is about 85% with most of the thermal losses in the dry gases and the moisture. Steam
generation is about 1.4 t/h per MW.
In order to maintain the concentration of accumulated dissolved solids in steam boilers
below 3500 ppm, periodic discharge of hot water (blow down) is practiced.
Fuel is used in food plants mostly for generating process steam and process drying. Natural
gas and liquefied propane (LPG) are preferred fuels in food processing, because their
combustion gases are not objectionable in direct contact with food products. Fuel oil and
coal can be used for indirect heating, i.e. through heat exchangers.
Culinary steam of special quality is used when steam is injected in food products. The
steam must be free of objectionable chemicals used in boilers, which may be carried into the
food being heated. Culinary steam is usually produced from potable water in a secondary
system of a heat exchanger heated with high pressure industrial steam.
5.2.3 Electricity
Electrical power in food processing plants is needed for running the motors of the
processing, control, and service equipment, for industrial heating, and for illumination. For
a medium size food plant processing about 100 tons/day raw materials, the power
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