Cleaning the Air in Your Factory can Save Operational Costs – and the Environment
Parisa Javadian Namin has a master's degree in media management from the University of Siegen.
Since April 2012 she is responsible for all of KMA's global marketing activities. KMA Umwelttechnik GmbH produces filtration systems for the use in many different industrial sectors.
KMA filters and controls show low energy consumption as well as an ability to remove pollutants completely. Over the years this techniques have been awarded with several environmental prices. The head office of KMA is located in Koenigswinter, Germany.
Since 2012 KMA has an office in Shanghai, China. www.kma-filter.de
A new World Health Organization report, which was released in March 2014, stated that in 2012 around 7mn people died as a result of air pollution exposure. This means that a staggering one out of eight global deaths were caused by air pollution. Awareness of and a sense of responsibility for air pollution is needed more than ever, especially in the industrial sector, and especially in the People´s Republic of China, where smog hangs heavy over the megacities and millions of children grow up with asthma and other respiratory illnesses.
In many factories the exhaust air is captured and transported to the outside without being filtered. This slightly improves the air quality inside the hall, but only by moving the pollutants outdoors. In addition, letting polluted air disperse in the hall before being filtered allows aerosols to be deposited on products and expensive machinery. This results in high maintenance costs, and, in most cases, short life expectancy for the machinery. The large amount of exhaust air movements consumes large amounts of energy for the exhaust and inlet ventilation systems. At the same time, this method causes increased heating costs during the winter, because the air transported outdoors must be replaced with the same amount of fresh air from outside. These facts increase the company´s operation costs and carbon CO2 emissions. The use of energy efficient air filtration systems can lead to a significant improvement in the company's balance sheet. Besides, clean air at the workplace increases the productivity, motivation and overall health of employees.
Methods of Exhaust Air Treatment
An interesting aspect of modern solutions for air purification is their energy efficiency. Air treatment systems with a disadvantageous layout necessitate enormous investment and running costs. A modern solution can, however, help to reduce energy consumption and operating costs significantly, permitting a quick return on investment. To provide a better idea of differences in the energy demands of different exhaust air treatments, we will use the example of an imaginary die casting foundry in Changchun. Die casting machines create highly greasy and polluted smoke. Changchun has a median daytime temperature of -4.4 degrees during the winter period (October to the end of April), while the desired indoor temperature is 17 degrees, or around room temperature. The manufacturing hall of the foundry has a total volume of 78,000m3 and is equipped with 20 die casting machines in several sizes (from 640 tons up to 2500 tons). The management has now several options for air treatment.
First Method: Conventional Exhaust Air Ventilation System
A conventional exhaust ventilation system works very simply: the waste air is led outside through complex exhaust ducts and chimneys at the roof of the building and fresh air from outdoors is led inside through the inlets. This method ensures clean air at the workplace but creates high follow-up costs. The main reason for these costs is that allowing fumes to get dispersed in the hall first creates a nonessential increase in exhaust air, which then needs to be purified. A high volume of air always means high energy consumption. Practical examples show that generally the ambient air inside the hall has to be exchanged with outside air by a conventional ventilation system 10 to 12 times per hour to keep the indoor environment clean. In our example this means an air volume exchange of at least 781,200m3 per hour, plus high pressure loss (generated by the exhaust air ducts) and high heating costs of the incoming air. This results in an annual operation cost of RMB 19,056,770 and carbon dioxide emissions of about 3,500 tons per year.
Second Method: Exhaust Air Filtration System in a Recirculating Air Mode
Today´s most energy-efficient principle of exhaust air treatment is the recirculating air mode. In the exhaust air mode, the waste air is led outside, either with or without air purification. This method ensures clean air at the workplace but creates high follow-up costs, especially during cold winters or hot summers. The reason: the same amount of air that is led outside has to be replaced by incoming fresh air from outdoors, which has to be heated up first or cooled down first before it is led inside. Heating up or cooling down the fresh air to room temperature will cause high amounts of energy consumption and operation costs for the company. At the same time the environment gets polluted by high CO2 emissions caused by energy consumption processes. On the other hand, in a recirculating air mode the exhaust air will be filtered very effectively by the use of highly efficient electrostatic filter units. After the filtration the purified air will be led back into the production hall via an integrated vent lation system which works with a frequency converter. Whenever the filter is in operation, the energy-efficient ventilator starts working and creates a bit of air movement, so that the exhaust air and later purified air is led to the right direction through the filtration system up to the air outlet of the filter. As the purified air is led back into the manufacturing hall, there is no need for maintenance-intensive exhaust air ducts, which cause high pressure loss and increase the energy demand.
In this system, each die casting machine is equipped with specially adapted extraction hoods. These extraction devices capture fumes efficiently and directly from the die casting machines, preventing fumes from being dispersed into the production hall and therewith, no high air volumes for the exhaust air treatment. In our example the exhaust air volume decreases to 215,400 m3 per hour. Low air volume always means less energy consumption. Each die casting machine is also equipped with one decentralized compact filter system. The filter units are electrostatic precipitators, which ensure highly effective separations of smoke, dust, and fine mist whilst using little energy. Unsuitable filter types can quickly clog and become ineffective, leading to excessive costs associated with filter replacement and disposal. However, changing the electrostatic filter cells is not necessary and they never obstruct the air flow through the exhaust system. The electrostatic filter is an economical and durable filter medium for many applications. In our model case the exhaust air filter system with a recirculating air mode leads to very low energy consumption. Hence, the foundry in Changchun now has operation costs of only RMB 1,098,791. That’s more than 90% less than the costs of using a conventional ventilation system. Additionally, carbon dioxide emissions are reduced to 416 tons per year.
According to these statistics, the recirculating air mode has the most energy-saving potential. Although this principle is used in many modern and new-built foundries, in some foundries the demand for exhaust air mode systems still exists. For these cases there is an energy-efficient exhaust air alternative, explained below.
Third Method: Centralized Exhaust Air Filtration with Heat Recovery System
On some winter days in Changchun the ambient median temperature goes down to -16°C. Using a conventional exhaust ventilation system will also bring down the temperature inside the hall. Therefore, many foundries in the region have to heat up the production halls to keep productivity high, but due to the high energy costs that are caused by heating systems, some foundry managers see this as an untenable solution. What often is not considered is the fact that in most production processes high amounts of heat and energy are created which can be used for follow-up processes. The centralized exhaust air filtration system, equipped with an integrated heat recovery system, enables an energy-efficient heating or cooling of the hall by performing in an exhaust air mode.
In this system, the multiple machines are connected to one centralized large exhaust air filter system. That means the waste air from the machinery is extracted through exhaust ducts and led to the centralized filter system, which is equipped with electrostatic precipitators as well as integrated in-tube heat exchangers. After filtering aerosols out of the exhaust air, the heat pump, which is connected to the filter system, extracts the energy out of the purified air. The energy is transferred in the condenser of the heat pump to a heating water circuit. Afterwards, the heating water is led to a second heat exchanger, which is installed in the incoming air duct. With this method the incoming cool air is heated up in an energy-efficient and economical way before it flows into the production hall. With the help of a highly efficient heat pump, the foundry in Changchun increases the temperature inside the hall up to room temperature just by using the heat recovered out of the exhaust air. With an energy demand f 352 kW per hour, the heat pump creates almost 1,500 kW per hour for follow-up processes.
In this scenario the foundry in Changchun would have annual operation costs of RMB 4,235,717, which goes along with an annual carbon dioxide emission of almost 1000 tons. These energy savings are less than the foundry in Changchun would achieve with the recirculating air mode, but the savings are still much higher than those of a conventional exhaust ventilation system with a simple and energy-intensive heating system.
Take Action on Air Pollution
The energy consumption in foundries depends heavily on the energy input of the exhaust and supply air systems. High energy consumption always means high amounts of CO2 emissions. Through the use of energy-efficient exhaust air filtration systems the air is cleaned and significant reductions in carbon dioxide emissions can be made. Die casting foundries and other metal processing entities can easily improve the company´s “Carbon Footprint” and make an important contribution to climate protection. Therefore, a change in thinking for each factory is worthwhile.