In this section we present a case study of technological gas emissions solutions that we created for a company called Exoterm-It d.o.o.
družba za proizvodnjo, inženiring, zastopstvo in trgovino,
Struževo 66, 4000 Kranj.
ABOUT THE CLIENT
EXOTERM-IT is one of the leading and largest manufacturers and suppliers of supply material for foundries and metallurgy active predominately in south-eastern Europe. With the help of computer simulation of lithium hardening moulds are hardened into castings, enabled by the MAGMASOFT software suite. Their products and services that are the result of expertise, research and creativity, guaranteeing the optimal solutions in their production of high-quality metallurgy and foundry products. Customers have the option of contacting technical support as well.
PROCESNI INŽENIRING podjetje za inženiring procesnih in energetskih naprav d.o.o., Gregorčičeva ulica 22, 1230 Domžale.
ABOUT THE CONTRACTOR
Procesni Inženiring deals with the use of gas in industries relying on energy efficiency: steelworks, foundries, ceramics industry, the mineral wool industry. Our devices are robust, technologically advanced, and characterized by optimal energy efficiency as a result of utilizing BAT technology, in addition to being safe to use and environmentally friendly. In our design we follow the wishes of buyers and the demands of concrete technological processes.
“Caring for the environment is an investment in all of our futures. Let’s keep our environment safe from harmful emissions coming from dryers!”
INTRODUCING THE PROBLEM
Exoterm-it company was looking for a solution for drying products that are sold to foundries and steel companies.
These are the so-called insulation caps made up of substances such as silica sand, mineral wool fibres etc., mixed together in a liquid form together with binders. Thus substances gain a form, with the help of moulds of different shapes, that is unstable until the water evaporates, whereby the binders also need to build networks around the structure.
These are the are the so-called insulation moulds, made up of refractory fillers and binders. The substances are moulded with the help of moulds into their final form as products, being unstable in the initial phase until the binder reacts and creates a network around the structure.
Different organic compound mixtures are used as binders that are polymerized at increased temperatures. This is why wet half-products are led through the dryer, where polymerization takes place.
Problems may arise as the binder evaporates into the dryer atmosphere, and later through the chimney into the environment – the emissions are saturated with harmful organic compounds (OC) and ammonia.
“When energy efficiency, drastic reduction in energy use and a healthy environment go hand in hand.”
PRESENTING THE SOLUTION
Based on the demands of dryers at Procesni Inženiring we have manufactured a dryer with the following technical specifications:
Evaporated water mass: 150 kg/h
Mass of the evaporated binder: 10 kg/h
Mass of products: 600 kg/h
Dryer heat load: 397 kW
Savings with a heat transmitter: 70 kW
Savings with binder oxidation: 65 kW
Dryer net weight: 23 T
The problem of pollution arising from emission gases is solved via thermal oxidation. Such systems have been in use since the beginnings of environmental legislation, which is why for the past 20 years we have been installing oxidation chambers to existing devices (for more information see: www.procesni.si) that are set up independently from the existing systems. The change being that the gas emissions are not led directly into the chimney, but through a channel – into the oxidation chamber heated at above 800°C, where all organic compounds dissolve into non-harmful CO2 and H2O.
One of the shortcomings of these devices is a higher net gas use, as higher temperatures need to be maintained in the oxidation chamber.
Part of the useful heat is undoubtedly compounded in the transmitter or the regenerator and is later on dissolved into gas emissions arising for combustion, while the rest travels into the chimney presenting energy loss.
The system that we have developed at Procesni Inženiring, based on our experience of doing updates on previously mentioned systems, increases energy efficiency and drastically reduces energy use as a result of:
- the compactness of the product, everything is in one place, doing away with the long exhaust channels to the oxidation chamber
- a thought-out energy scheme, making use of the heat going into the chimney, but ensuring it returns back into the process
- making use of the calorific value of organic carbons that emit heat during combustion.
“The compactness of products. A thought-out energy scheme. Making use of the calorific values of organic carbon. And a new design concept.”
The above mentioned key points have been successfully incorporated into the design of the described dryer. We were given free reign during the design process. We started the project by creating a scheme with the optimal energy-efficiency. By doing this we created a design based on an existing oven, a heating system with 4 burners in 4 zones, and a brand new concept of ovens.
We have developed an oven design with central hot air preparation, meaning a burner for each of the 4 zones.
As we are bound by the new legislation on gas emission with our new device, this by extension means that the previously used system would not meet the legislative requirements – the emissions would exceed the allowed limits or an independent oxidation chamber would need to be placed next to the dryer. This would double the investment costs.
“When saving on costs means caring for the environment.”
We have decided on a model where the oxidation chamber is simply part of the dryer set up, built into its ceiling. This is the same zone where the hot processed air is prepared and where the combustion in the oxidation chamber takes place simultaneously. The zone where most binders exit the products and the processed air is led to the combustion chamber, and where with the help of the burner the temperature is raised high enough to allow for oxidation. The treated hot emissions are then led through the dividing channel and regulation flaps so they can be blown into individual zones. At the same time we are making use of heating value of solvent emissions in the combustion chamber. The heating value from the emissions is different with every dryer, depending on the solvents/binders being used, and their mass fraction in the air.
In our case savings just from burning organic binders amount to 16 % or 65 kW!
The air behind the combustion chamber is not led into the chimney, but is blown back into the drain for drying. The device, however, still requires a chimney and for part of the air to be channelled through it, as with each dryer moisture needs to be removed, or saturation occurs. The difference being, however, that with traditional dryers the amount of transported air is linked to the concentration of emissions, solvents/binders, as the LEL (lower explosive limit) needs to be maintained. LEL is maintained by keeping the percentage of the solvents in the dryer atmosphere sufficiently low so combustion or even an explosion can occur.
Solvents were partially burned in our dryer, which is why large amounts of air no longer need to be sucked into the chimney. This consequently reduces heat loss.
The third part of savings comes from the heat transmitter. All the air being sent to the chimney needs to be replaced by surrounding fresh air.
To maximize energy efficiency we have built a transmitter into the dryer that extracts the heat from the gas emissions and adds it to the fresh air being sent to the dryer.
“Because we breathe with you.”