Charcoal kiln CK "Continuous"
The charcoal kiln is designed for continuous charcoal production from hardwood and softwood.
- production capacity of this kiln is 3400, 6000, 12000 tons/year of charcoal;
- the yield of charcoal in case of using hardwood species – not less than 170 kg/m3.
The charcoal-burning plant includes:
1. Vertical kiln of shaft type
2. Vertical twin wood dryer
3. Recovery-boiler and furnace for the pyrolysis products burning
4. *other equipment in accordance with agreed specifications.
Technical and Economic Parameters
|No||Name of parameter||Value|
|1.||Efficiency by ready-made-product, t/hour||0,435 / 0,7 / 1,4|
|2.||Consumption of wood for 1 t of charcoal, m3||6,3|
|3.||Process water consumption for 1 t of ready-made product, thousand m3||0,06|
The following solutions are used in the unit:
- Production process is provided by its own heat due to the complete combustion of the wood pyrolysis products in the large furnace. The resulting flue gases have an enthalpy. This enthalpy is sufficient to effect preliminary wood drying, to provide pyrolysis process and charcoal tempering process and also to produce saturated steam and hot water for household and technical needs.
- The same solution provides the recycling of liquid phase which is formed during the wood pyrolysis. The liquid phase recycling eliminates a significant environmental problem of getting acid residues in the soil and wastewater.
- Increased charcoal yield is achieved by automatic control of wood pyrolysis temperature and by strict control of oxygen content in the coolant and cooling gases.
- Disposal of excess heat and vapor production are provided by the installation of heat-recovery boiler.
The raw material for charcoal production is hardwood in the form of logs and chocks not exceeding 300 mm long and with conventional diameter of 30-120 mm. There are not available rot nobranching or hollow spaces of the timber.
It is possible to process wood of worse quality although the main yield decreases and yield of small fraction increases.
Depending on the fixed technological mode, it is possible to produce charcoal corresponding to all existing standards EN 1860, DIN 51749-H, AFNOR and others – gastronomic charcoal possessing the next chemical composition:
- Content of solid carbon Cfix78-88%
- Content of volatile substances 12-16%
- Content of moisture < 6%
- Content of ash < 4%
20-60 mm and more than 60 mm fraction are considered to be marketable product. In accordance with GOST standard metallurgical charcoal consists ofthe next chemical composition:
- Content of solid carbon Cfix88-92%
- Content of volatile substances < 3%
- Content of moisture < 3%
- Content of ash < 4%
Fractions of 20 – 60 mm above 60 mm are considered as marketable product.
The wood in a form of pack of chockswith a length not exceeding 300 mm is supplied into the intermediate hopper 9 from which it is loaded by skip hoist into the flow twin dryer of wood 21 and 22 through the receiving and distributing hopper and hermetic loading chamber.
The wood dryer operates on the principle of direct-flow due to supply of heat carrier and wood into the top part. Upper temperature limit of the heat carrier is set at 230 oC level by means of mixing it with necessary amount of recycled gas (or air).
Dry wood is unloaded from the lower part of the dryer by the feeder through hermetic unloading chamber into the retort loading skip which supplies wood into the loading chamber of the retort equipped with dual hermetic gate. From the loading chamber wood gets into the vertical continuous retort 1.
The wood moves continuously down towards the rising heat carrier, due to which the process of wood pyrolysis and charring is carried out with charcoal production.
Тechnological production scheme of CK “Continuous”
The heat carrier is supplied in the middle part of retort by high-temperature gas blower with 500-600 oC depending on type of produced charcoal and it is diverted with other pyrolysis products from the upper part of the retort under approximate temperature 150 oC. The produced charcoal continuously moves down, passes zone of heat carrier enter and gets into the cooling zone located in the lower part of retort and produced by means of blowing of cold steam gases with 30-40 oC temperature into the lower part of the retort. Cooling gas is carried off the middle part of the retort (lower than zone of heat carrier input) with a temperature about 350 oC.
With a help of unloading chamber equipped with dual hermetic gate cooled charcoal is unloaded from the retort and it is loaded in to the middle hoppers for charcoal by the conveyor.
Sifting of small charcoal pieces is carried out before loading into the hoppers.
Used heat carrier in addition to gaseous products of wood pyrolysis (fire gasses, resins, organic acids and steam) are taken out the upper part of the retort into the furnace of steam-gases 3. Air is pumped by the fan into the furnace in addition to steam gases. Amount of supplied air is controlled automatically by the valve depending on the content of oxygen in the combustion products.
To provide complete burning of combustible products contained in the steam-gases there is enlarged volume of the furnace – 50 m3. Maximal temperature in the furnace reaches 1300 oC. The produced products of combustion are divided into three flows. The first flow is directed into the waste-heat boiler 4 for process steam production andinitial cooling of combustible products till 200-250 oC. The second flow is directed into the mixing chamber 6 to prepare the heat carrier for the retort and the third one is directed into the mixing chamber 5 for preparation of the heat carrier into the wood dryer.
The used gases going out the waste-heat boiler are drawn out by the fan and divided into two flows supplied into the mixing chamber of the dryer and retort to receive necessary temperature of the heat carrier. Relation between the flows is regulated by the valves.
Heat carrier in the retort and cooling gas form closed circuits and used heat carrier is directed from the wood dryer into the atmosphere through the chimney.
To start the retort there is a gas burner in the fire chamber to obtain heat carrier during start-up period lasting for 24 hours. In case of natural gas absence it is possible to use liquid fuel burners.