Optimized Usage of Energies in Large
Size Laundry Industry
Preface:
We all easily relate to the laundry
process, but still very few of us really understand what is involved
in the equipment and the chemicals used.
The laundry equipment industry is very
cost-effective; as a result, it has produced well-engineered equipment at a
very reasonable cost to the user. In the present day, the laundry equipment has
to be reliable and cost-effective.
Efforts of reducing the consumption of energy should be aimed at
reducing the amount of hot water used in the washing machine. Hot water
accounts to be more than 90% of energy entering the washing machine and more
than 60% of the total energy utilized in laundry business.
Increases in chemical dosing and
increase in the washer cycle time can be substituted for thermal energy, that
is the energy required to heat the water and produce equally clean laundry,
saving both the energy and finance for the user.
A heat exchanger to pre-heat the water entering the washers can increase the efficiency of the washer. Increased efficiencies of the motors used in the operations of washers and offer break-even economics over the life of the appliances.
Automatic Washer Extractor:
Typical
washer-extractors operate in cycles composed of wash cycles, rinse cycles
and washer extraction cycle. As the washer-extractors will be handling
different types of chemicals and different types of contaminated clothes, it
has to be versatile in operation and help the user to easily program the
machine as per the specific requirement.
An
ideal washer-extractor is one which operates at minimum cost and gives the
maximum cleanliness as expected.
Although it has shown that the hot water is able to do much better laundry compared to cold water washing. Hot water wash consumes more energy compared to cold water wash.
The Process of Removing Soil: Cleaning Process
There
are three methods available to accomplish the task of removing soil from the
fabric. They are Mechanical, Thermal, and Chemical.
The mechanical method involves bending and
squeezing of clothing inside the drum, hydraulic pressure on the garments
exerted by the water and the rubbing of the garments with each other and
itself.
The thermal method helps increase the
solubility of the soil in warm water.
The third method always complements each
other, agitation at high temperature accelerates the chemical reaction on the
soil.
The purpose of laundering is not only cleaning the soil but also keeping intact the shape, color, and strength of the fabric. The nature of fabric imposes a limitation on the use of warm water, the strength of the chemical, and the strength of agitation. Also, the laundry should smell pleasant and should be relatively disinfected.
Soiling Agent:
Substances
that turn clean laundry into dirty laundry are called soiling agents. Clay,
dead body cells, oils, and food stains are some of the substances. These
substances penetrate into the fiber of the fabric, bond themselves with the
fabric by electrostatic attraction or surface tension force, and even sometimes
chemically reacts with the fabric. As the soiling agents come in many forms, it
becomes very difficult to remove this with a simple cleaning process.
Water:
The
rainwater picks up many pollutants in the atmosphere on its path to the ground.
Though it is abundant, it is very difficult to get pure water. Water is a good
solvent, hence dissolves all types of minerals. Iron, calcium, and magnesium
are the principal concerns in the laundry process. Most municipal water supplies
deliver water at acceptable concentrations. In places where iron is a problem,
their iron exchangers are fitted in filtration plants. Calcium and magnesium are the
substances responsible for hard water.
Hardness
greater than 6mg/liter, which is the concentration of calcium and magnesium,
reacts noticeably with the soap to form scum. Most municipal water is delivered
with the hardness of more than 100 mg/liter. Hence hard water is an issue to
be tackled in the laundry process.
In hard water, the color turns dull and whites turn grey, the hardness of water will cause the fabric to lose their softness and will wear out faster.
Fabrics and Finishes:
Detergents:
Detergents are referred to as surface-active agents, Detergent is commonly used to refer to both the surface active cleaning agent and the finishing cleaning agent including the surfactant. Some detergents contain chemicals to control suds action and enzymes for stubborn stain removal. Other laundry aids are bleaches and fabric softeners. Being an oxidizing agent bleaches whitens the clothes.
Cold water wash:
Cold
temperature washing with gentle agitation is the recommended process in some of
the fabrics like polyester and synthetic fiber. Cold water laundering saves tremendous energy over the hot water
process. However, some powdered detergents do not dissolve properly in cold
water laundering.
Keeping this in mind, new cold water detergents were formulated to improve low-temperature water performance. Another problem with the use of cold water is that disinfection does not happen in cold water.
Detergents and Germs:
Bacteria
and viruses are referred to as germs. The virus is smaller than bacteria.
Viruses are capable of causing diseases in men, plants and animals. Both
bacteria and viruses are present in water used to wash the laundry. Ideal
laundry is to wash and dry germ-free clothes. However, effective bacteria
removal is attended by the use of hot water temperature, strong detergent
concentration, longer washing time, and higher drying temperature.
The
general trend is that if cold water is used for washing clothes in the laundry
then, either the concentration of the chemicals or the washing agitation time
has to be increased to obtain the appropriate cleaning power. The total cost of
the wash cycle decreases as the temperature of the water is reduced. The net
result of this is positive, the energy is saved and the consumers get equally
clean clothes spending less money.
Warm water washing with more agitation and moderate chemical use appears to be the best combination for washing clothes.
Rinse Cycle:
To
remove excess detergent from the washing load process of rising is done. It is
observed that a warm water rinse gives better results compared to a cold water rinse.
Also, warm water rinse gives better water extraction compared to cold water
rinse, so also it delivers the preheated load to the dryer, further conserving
dryer energy.
Experiments
have shown that a cold water rinse is more energy-efficient than hot water
rinse even when the dryer gets the advantage of warm clothes in the feed when
used in conjunction with washer.
Extraction Process:
There
is an extraction done after washing and rinse cycle in all the modern automatic
washer-extractors. The left out moisture in the load after the wash and rinse
cycle is removed during extraction, where no external heating is applied.
The
factors that affect the extraction are spin speed, the diameter of the drum,
thickness, and the physical structure of the fabric, temperature and the
surface tension of the water. The punched holes (perforation) in the drum also
plays a vital role in the percentage of extraction.
The
surface water is removed in the wash load, the water in the twisted fiber is
removed in the extraction and the moisture contained in the pores is usually
removed in the dryer.
The higher the spin speed, the more the extraction. The spin speed of say 600 rpm
retains the moisture in the fabric equal to the weight of the fabric.
Increase
in the spin speed would result in the extraction of water, but the cost of the
operation increases significantly and the wrinkles would form on the clothes.
Development of additives to use in the extraction cycle to decrease the capillary forces between the fabric and water may increase water action in the conventional washing machines without causing wrinkles in the fabric.
Energy consumption in Dryers:
The mechanical tumbling action of the tumbler and the airflow,
which is heated, enables the laundry load to dry in the dryer. The hot air flow
is either axial, radial, or both. The dryers are designed to match the washing
cycle of the washing machine, in order to minimize the waiting time.
The rate of evaporation
is somewhat fairly constant at the completion of 70% of the cycle time, compared
to the rate at the beginning and at the end of the cycle.
Three types of
controllers are used to terminate the drying cycle.
Manual set timer
It is the least expensive timer and it is set manually by the
operator by setting the approximate time required to dry the load as per his
experience. This timer is difficult to set precisely.
Exhaust temperature actuated controller
These timers are used in
conjunction with manual timers. It shuts down the cycle when the dryer attains
the pre-set exhaust temperature.
Moisture sensing devices
It is the most expensive
of all the timers. It measures the conductivity of the fabric down to about 30%
of moisture level.
Observations say that
automatic termination controllers do not save more energy on the manual control
device.
In many cases, it is observed that when small loads are dried in
large capacity dryers, automatic control tends to over-dry the clothes. As the
load increases compared to the drum size, the automatic control device becomes a
more effective energy conserving device.
If the dryer is loaded with mixed fabric then the synthetic
clothes will dry faster than the cotton clothes and the drying efficiency will
be reduced.
For most dryers, exhaust heat has a temperature of
about 55 degrees centigrade. The most convenient way to use the exhaust is to preheat the inlet air, which would reduce the energy consumption of
the dryer to further 5 to 10 %.
Present-day laundry equipment is well designed and will not change
much in near future in the techniques used in cleaning and drying the laundry.
Modern laundry equipment is reliable and cost-effective.
