Since 2008, the Studiogest group expanded its business outside Switzerland, especially in the Middle East, in countries such as Lebanon, Dubai, Iraq, India and many more.
With the growing environmental and energy problems on a global level, which exert high pressure on the economies of the world’s most countries, SG Contract is continuously involved on developing program solutions for the recycling of solid and liquid waste, who is based on the following points:
- Reducing the cost of recycling,
- Preventing environmental pollution,
- Waste-to-energy generation, the process of generating energy from burning waste,
- Local and remote IT-control, based on the latest and most sophisticated technologies.
The in-depth steps for reaching our target:
- Sorting metal from the general waste; recycling all other recyclable materials; burning just the remaining waste;
- Using the latest generation filters on the market to prevent toxic and polluting emissions;
- Efficient burning of liquid waste materials by using a ultrasonic industrial process;
- Waste burning at very high temperatures, causing self-ignition and exhaustion preventing most of the fuel needed, which reduces the cost of recycling;
- Exploiting the heat generated from the waste burning in the production of energy, such as electricity and desalination.
Those methods combined, make us one of the most advanced players in the field of recycling machinery, ever since our solution has the lowest side effects on the environment and depends on very low running costs thanks to the process of generating free electrical energy.
During the entire cycle of our operations, we use the latest technologies available in the market in order to reach the best production capacities without harming the environment.
Among our services, we also provide financial assistance to fund the building of integrated solutions, through a strong collaboration with both European and global banks and financial institutions specialized in the field of energy production and global development.
The waste management of the last few decades has left to us and to the following generations a hardly deﬁnable number of ecological time bombs.
In future depositing untreated waste will be stopped while the time has come for ecologically and economically sensible thermal waste treatment. So the way to sustainability starts right now. The biogene parts in waste amount to more than 60%, thus contributing indirectly to the reduction of CO2-emissions.
These plants are an important and valuable contribution to climate protection providing for safe waste management and accurately obeying the law.
For incineration they mainly use two systems, typical of the Hafner technology: grates and rotary kilns.
SG Contract SA collaborates directly with the independent subsidiary based in Winnweiler (Rheinland-Pfalz, Germany) and is mainly engaged in projects in Germany but also in the new accession countries and overseas.
SG Contract SA offers cost-effective solutions which allow energy recovery from as waste, biomass, sludge etc.
Its biomass power stations put the SG Contract SA Group right in the middle of a growing ﬁeld of interest: it keeps concentrating on the realization of facilities ready for putting into operation for the thermal treatment of municipal solid waste as well as industrial and medical waste, also sewage sludge and biomass, usually by means of water-cooled grates and rotary kilns.
Based on our experience and in cooperation with our partners we have developed a system for the thermal recovery of waste and biomass that complies with the situation new European directives.
SG Contract SA develops individual thermal plants tuned to the clients’ demands. The facilities are equipped with proven and sure technology, based on “incineration grate” or “rotary kiln”. The plants are also characterized by low operational costs and reasonable investment costs. We produce facilities for the thermal treatment of:
- household waste
- hazardous waste
- hospital waste
- sewage sludge
- liquid waste
Flow diagram of a thermal treatment plant
The material is tipped from the delivery vehicles into the bunker. Thanks to a rolling gate with light barrier controlled by a key-operated switch fuel can be delivered also when the facility is not being operated.
For the bunker management and the feeding of the kiln a bridge crane is used. With its runways and trolley the crane can reach over the entire bunker area. The grab is moved by the lifting gear and can be operated manually, by radio or automatically.
A hydraulic slide conveys the material through the feeding duct onto the incineration grate.
The feeding grate has four parts. It is driven hydraulically via proportional valves, just as it hap-pens in the feeding cylinder. The feeding changes from one grate segment to the other by tuning the cycles. First the combustion-ﬂue gases are pushed upwards.
The gases are then diverted and pushed downwards to the evaporator, the superheaters 1 and 2 and ﬁnally to the 5 economizers. The evaporator heat exchange surfaces work according to the natural circulation ﬂow.
The boiler consists of various membranes in order to produce saturated steam.
Planning and production of boilers
SG Contract SA calculates, plans and produces complete steam boilers of 5 – 150 tons with a pressure of 10 -110 bar and a temperature of up to 450°C.
Boiler and steam drum
The feedwater ﬂows ﬁrst through the economizer heat exchange tube bundles and then through the economizer air pre-heaters, where it is heated before ﬁ nally ﬂowing into the steam drum. The steam drum is placed on the boiler roof.
Flowing through draught tubes the water reaches the membranes where water is transformed from liquid to gas.
The resulting saturated steam is conveyed from the steam drum directly to the superheater.
Recirculation of ﬂue gases
By means of correction factors the number of cycles per grate segment against slag production is being adjusted in a declining manner, the feeding speed thus decreasing towards the end of the grate.
The aim is, to guarantee the constant covering of the grate with waste and slag as a protection against overheating. The number of cycles of the grate segments is managed by the kiln master controller.
By its movement the feeding grate has a poking effect which improves the burn-out. Part of the stream of ﬂue gases is being mixed with primary air which helps to reduce the NOX emissions and to lower the grate temperature.
The recirculation air blower is being put into manual operation mode, the amount of air being deﬁned by speed pre-selection.
Generally speed regulation can also occur automatically in relation to kiln temperature.
This view shows the back coolers on the roof of the boiler.
The steam coming out of the turbine is being changed from gas into the liquid state of matter by being cooled and transformed by the condenser. The steam passes through various bundles of ﬂuted tubes which are streamed on with air by fans from outside.
In the feed water tank (with deareator) the condensed water at a temperature of 50°C – 55°C is heated up to 104°C before being led back to circulation.
Burner *(Dumeco ultrasonic burner)
Function of the boiler
Saturated steam purged from the boiler drum reaches the ﬁrst and then the second superheater.
Between the two superheaters the steam is cooled by a water-spray-system, which regulates steam temperature, and conveys it to the turbine.
The feedwater tank consists of a tank and a manhole to degasify the boiler feedwater.
The water supply in the boiler is granted by the pumps of the feed-water tank feeding water through the economizer entry.
Condensed water (approx. 50°C) ﬂows from the air cooler into the feedwater tank and is heated up to 104°C by injecting steam (ex-traction turbine). The blowdown water is replaced via the pumps.
Fly ash falls down on ﬁlter bags hanging in the dust ﬁlter. Compressed air is periodically blown onto the ﬁlter bags (impulse-jet-system) making ﬂy ash fall down into the hopper of the dust ﬁlter before being ejected by a spiral-like screw.
Process guidance system starts off the cleaning process by means of compressed air once the pre-selectable differential pressure is exceeded.
The cleaning process triggered off automatically by the “ﬁlter cleaning” device. The hopper is also provided with “air-shocks”. Blowing in compressed air prevents the formation of dust bridges.
Cleaning of exhaust gases
After the boiler the ﬂue gases are introduced into the upper part
of the reactor which is a vertical vessel. The additives sodium bicarbonate and activated carbon can be added to the ﬂue gases through nozzles inside the reactor before the conditioned ﬂue gases exit at the bottom of the reactor, reaching the ensuing bag ﬁlter. There is a control ﬂap on the upper part of the reactor. In case of overheating, according to the measurement taken in waste gas ﬂue after the reactor, this ﬂap opens in order to lower ﬂue gas temperature thus protecting the bag ﬁlter (ﬁltration plant).
Rotary kiln plant
The rotary kiln incineration plant can basically be divided into the following parts:
- waste feeding
- incineration in rotary kiln and afterburner chamber
- waste heat reuse
- cleaning of ﬂue gases
- emission measurement
The given waste menu usually consists of not reusable household and industrial waste. After delivery the waste is weighed and registered before being conveyed into the corresponding bunker.
When doing so the waste is fed into the bunker via delivery chutes. If necessary the waste is cut in a shredding machine.
With the hydraulic grab of the waste crane the waste is mixed, homogenized and transported towards the feeding chute. The storage capacity of the waste bunker is of approx. 5 days if fully operated.
Exhaust air from the bunker is withdrawn by suction via the primary air ventilator and is led into the rotary kiln as combustion air. Shredded waste is being continually transported into the combustion chamber by means of an O2-regulated screw conveyor.
By means of the feeding spiral-like screw conveyor waste is fed into the brick-lined rotary kiln for incineration. Every rotary kiln module has a capacity of 25,000 t/a. Operational capacity per unit is of 3.5 t/h with an incineration temperature of 950°C.
In the projected operational model the arising exhaust gases stream in the opposite direction of the kiln into the afterburner chamber. Rotating speed and the feeding are regulated by a temperature and oxygen tube.
Through various nozzles primary air is being injected causing increased turbulence and guaranteeing good oxidation. At the end of the kiln a burner has been installed which is ignited only at the be ginning (or in case of decreasing waste with low heating capacity). The slag resulting from incineration falls into a water bath at the end of the kiln. With a chain conveyor the sintered material is transported into a container (33m³). Every rotary kiln has a length of some 15 metres and it is erected on an 18-metre-long building module (container).
If required and depending on menu and incineration temperature glazed slag can be produced as incineration product. To do so the rotary kiln is run “in parallel ﬂow”.
Hot ﬂue gases ﬂ ow from the rotary kiln into the afterburner chamber where they are held for about 2 seconds at a temperature of 950°. Fly ash is collected in a spiral-like screw conveyor at the bottom. Secondary air is being injected by an O2-controlled fan.
Heat exchanger and boiler
At the exit of the afterburner chamber there is a ﬂue gas heat exchanger which has two main tasks: on the one hand it cools the hot ﬂue gases down to about 700°, on the other hand it heats the cleaned ﬂ ue gases up for NOx catalytic preparation. Flue gases are cooled down from 700° to 300° in a steam generator, the resulting heat being reused for warm water, steam or electricity. The waste water resulting from the exhaust gas cleaning process is collected in the water spray reactor from which it is directly injected into the hot ﬂue gas (300°C). Consequently, water evaporates while the solid particles (salts) are separated in the bag ﬁlter.
The burner, placed on the front of the rotary kiln, is a multi fuel burner (gas, liquid) disposing of its own draught. An interconnection system adds proportional quantity of air and gas. Every burner disposes of the checking equipment and shut-off arrangements required by law.
Fuel pressure and combustion air pressure
Burner draughts are set off by activating the automatic “burner air” system or automatically when the kiln temperature exceeds 300°C in order to avoid the overheating of the air feeding unit. Burners are operated automatically.
The temperature in the burning chamber can be regulated according to burner set values indicated by the control system.
Ash removal from the boiler
Our cleaning procedures foresee the installation of low frequency vibrators for the superheater and economizer of the kiln. Low frequency vibrators are periodically activated in accordance with an operation – break times control system, cleaning the boiler from boiler ash. Beneath the ends of the boiler’s hoppers there is a drag link conveyor taking the boiler ash away.
The ECO part is additionally provided with an ultrasound cleaner.
The steam turbine consists of a high-pressure and a low-pressure part. Between them there is the extraction steam valve aimed at various users. Depending on quantity, pressure, and temperature the main steam moves the turbine wheel(s) and by means of a coupling the resulting mechanic power is transmitted to the generator.
The generator produces electricity which is supplied into the net via a transformer. Exhaust steam of 0.15 bar reaches the air condenser where it is cooled down and led into the feed water container as condensate.
Rotary kiln plant with afterburner chamber
Feed regulation of the additive (Sodium bicarbonate)
The feed regulation of the additive takes place in a unit consisting of conveyor blower, rotor mill, and screw conveyor. The management system regulates the feeding quantity according to the revs-controlled screw feeder.
The sodium bicarbonate silo is provided with a vibration device. The management system starts both the operation – break time control system and the bottom ash ﬁlter placed on the sodium bicarbonate silo. This ﬁlter is needed for the system bleeding during the supply.
Activated carbon is conveyed out of a big bag through a screw feeder and it is blown into the reactor via a rotary feeder and a blower. The automatic device “activated carbon” starts the management of the parts involved in the feeding regulation process.