LOW AND HIGH CALORIFIC VALUE WASTE (PCI)
The plant described below is the result of some recent work that Off. Mecc. CIROLDI S.p.A. has carried out in Italy, United Kingdom, Malta, Russia and middle est.
The plant basically consists of an incinerating line suitable for thermal destruction of industrial waste (but also household or industrial sludge), from 300 up to 3000 Kg/hr (depending on the waste l.c.v.) on a 24 hours a day operation basis and including the following main sections:
– wheeled bin tipper and waste loading system,
– primary combustion chamber,
– transition chamber with automatic ash unloading device
– post-combustion chamber
– heat exchanger unit and dissipater for gas cooling prior to filtration
– flue gas treatment system based on a bag filter, complete with reagents dosing system
– emission parameter monitoring and recording system,
as better specified and detailed below.
The main advantages of this solution, in comparison with a discontinuous system having the same daily capacity, are the followings :
• lower fuel consumption
automatic ash unloading
• less stress in the refractory
• lower sizes
The plant is designed and manufactured in compliance with the European directive 76/2000/CE (WID) prescriptions.
2. Running the plant – Exploitation
The plant is designed for continual operation 24 hours a day – 7 days a week for an annual period of 300 days; 65 days being planned for stops and/or routine and extraordinary maintenance.
The work will be organised in three 8 hour shifts and each shift squad will consist of at least:
• 2 blue collar workers preferably qualified iron and steel technicians
• 1 expert electro-technical or electronics
• 1 expert qualified to run vapour boilers
preferably a heat technology expert.
The operating squad must be able to communicate with someone responsible for running the plant at all times, who will in any case be asked to guarantee his availability.
3. Legal references for emissions
The plant will be designed in compliance with the legislation laid down in point 1.
– the size of the pre-combustion chamber is designed for a temperature of no lower than 1.100°C, with a residence time of no less than 2 seconds and with a free oxygen concentration of no less than 6%.
– probes are foreseen for measuring and recording the temperature in the combustion and pre- combustion chambers.
– a probe is foreseen for continually measuring and recording the oxygen concentration coming out of the post-combustion chamber.
– probes are foreseen for recording the HCl, CO, COT, NOx, SOx and articulate levels
– the mean daily limit values and times of concentration of the main pollutants of the emissions to be observed (European WID n. 76/2000/CE) are the following:
Description of the incinerating line
The waste is loaded into the loading box of the incinerator by means of suitable capacity wheeled bins to be automatically lifted and dumped into the loading box.
Once the loading system is enabled, the top hatch of the loading box will open and the waste is loaded into the charge box and the charge box top door then closes.
Afterwards, the refractory lined guillotine door, which isolates the loading box from the rotary kiln, opens and the hydraulic ram then charges the waste into the kiln.
Later on the ram returns and the guillotine door closes.
Further loading cycles will follow, accordingly with a scheduled loading sequence
The action of both the charge box hatch, the insulating door and the ram feeder is interlocked with the combustion conditions in the incinerator. In fact, the rotary combustion chamber is supplied by an automatic loading system, controlled according to the temperature of the chamber itself.
If there is an abnormal increase in temperature exceeding the value set for the combustion chamber or if there are other emergency conditions determined by the plant control system, the microprocessor disables charging and it can only start up again when the parameters which caused the disabling return to the normal operational values.
The waste is progressively incinerated in an inclined rotary kiln with a sufficient air supply to give off combustible gases to the static secondary chamber where final oxidation takes place.
The rotation of the kiln turns the waste to improve contact with the combustion air and reduce the size of the waste constituents by abrasion.
The rotation of the inclined kiln also causes a gradual forward feed of the combustion waste from the loading area to the ash discharge area.
The equipment can be operated during 16 up to 24 hours per day without the need for intermediate stops thanks to an automatic de-ashing system.
Combustion air for the kiln is fed via a primary air fan and a burner is provided for both start-up purposes and to support combustion.