GRET LDP project
Bui Ngoc Long – Patrice Lamballe
Production trial of bamboo luong charcoal and activated carbon Assignments in need of implementation and completion GRET and LDP project participate in the provision of technical assistance to workshops, including main assignments as follows: 1) 2) 3) 4)
Carrying out first production trial. Adjusting techniques- technology of building and burning kilns Reviewing financial and technical aspects of production Making proposals on future investment in charcoal production sector
1. Preparation work a. Transferring primary production equipments to existing workshops •
It is concluded after discussion with workshop owners and based on the workshops’ needs and demand as well as their strategy, financial situation and land availability. o Three workshop owners expressed their concern and agreed to the establishment of kilns (X1, X2 and X4); X3 has no interest in coordination with X5 o X2 is not suitable for charcoal production because the workshop location lies in a narrow area, failing to provide enough space for building a kiln. o To make up for this, all workshops allow using X5 as the third trial. Therefore, charcoal production is carried out in 3 workshops: X1 (Thien Phu - Quan Hoa), X4 (Dien Chung – Ba Thuoc) và X5 (Xuan Phu – Quan Hoa)
b. Preparing construction materials o Materials collected on-site (cement, sand, bricks…): Bricks, sand are materials produced and available in the region. Cement is also available near the construction site, its price is nearly similar to that is in the plain’s market (only higher by 7-10%). o Materials purchased from Thanh Hoa: (glass wool, refractory bricks, glass liquid): these are special materials used for refractory structure of the kiln. They are not available in the region (including Thanh Hoa city) and have to be ordered from companies of refractory materials in Bac Ninh, Thai Nguyen at very high price:
•
Refractory brick: Price offered by the Factory is 1,700 VND/Kg, equivalent to 6,000 VND/unit (each brick unit weighs 3.5 Kg on average) excluding delivery fees.
•
Glass wool: 18,000 VND/kg. -
-
After studying the market, the team bought refractory bricks and glass wool from Thanh Hoa ceramic company at the price equivalent to 60% of market price (3,500 VND/brick unit, 1,000 VND/Kg glass wool) However, there is not high amount of these materials left. Therefore, on building the new kiln, material cost should be calculated according to factory’s price.
c. Collecting raw materials o After finishing the kiln, it takes at least 1-2 days to dry it before loading material for burning trial. The first burning time aims to dry the kiln and check its techniques so it is not necessary to take consideration of material and product quality. o From the second one, it is necessary to monitor burning techniques to identify product quality. Different kinds of material have different period of burning : •
For dry and thin material: burning time is short (ex. X4;1, it’s to say, the first cycle of kiln build in X4 workshop)
•
For thick and fresh material: burning time is prolonged (ex. X4;3)
o To make products with good quality: •
Materials for burning should be fresh poles,
•
Aged 3 years old or more and
•
Not spongy
Then after burning, the whole kiln will be evenly dried, with high temperature and high quality products. o Poles with thick wall and small perimeter will take time for fire distribution, requiring long time of burning and cooling which leads to maximum temperature inside the kiln and makes products with high quality and suitable for activated carbon production. d. Supporting kiln building
After studying reference documents of INBAR on techniques of building kiln and technology of burning carbon with anaerobic kiln, GRET research team assigned two officers to carry out following works: o Studying techniques of loading and burning carbon in anaerobic conditions according to the traditional method used by some villages and workers of burning carbon in Tan Thanh, Luan Thanh communes of Thuong Xuan district, Hop Tien, Hop Ly communes in Trieu Son district, and mountainous areas in Thanh Hoa province. o Carrying out burning trial of 3 rudimentary kilns in Kien Tho commune, Ngoc Lac district - Thanh Hoa for testing burning technology and learning experience. o Visiting workshops of charcoal production from bamboo luong in provinces of Hoa Binh (Mai Chau and Ky Son districts), Vinh Phuc, to select building technology and the kiln shape as well as study more about information of techniques, market and price of each product. o Referring to teachers of Hanoi university of technology and some workshops of ceramic production in Thanh Hoa on techniques and technology of building refractory kiln, and finally: -
Calculating and designing kiln model - estimating material cost - making estimates of cost and plan of building kiln for workshops. 8
7 1
6
5 4 3 2 1
1. Burning gate - 2. Place of loading firewood - 3. The front wall– 4. Smoke of luong material– 5. Way of burning temperature – 6. The kiln dome made of brick - 7. The back wall – 8. Chimney
Fig. 12: Diagram of the burning kiln made of brick
TT I
Expenses related to kiln building: Kiln X4 ( Simple kiln)
Details
16,150,000.00
3
Materials Refractory brick Glass liquid Asbestos fiber 3mm iron sheet
4
Normal brick
1,800,000.00
5
Cement
750,000.00
6
Sand
200,000.00
7
Slag, scoria
500,000.00
8
Delivery
900,000.00
1
2
7,000,000.00 500,000.00 2,000,000.00 2,500,000.00
II Labour Total
4,100,000.00 20,250,000.00
Kiln X1 (Double kiln) 28,030,000.00 12,250,000. 00 500,000.00 3,000,000. 00 4,500,000. 00 3,500,000. 00 1,500,000. 00 640,000. 00 640,000. 00 1,500,000. 00 5,370,000. 00 33,400,000.00
Kiln X5 (Big double kiln)
Total
35,650,000.00
80,155,000.00
14,000,000.00 750,000.00
33,250,000.00 1,500,000.00
4,000,000.00
9,000,000.00
6,250,000.00
13,250,000.00
4,000,000.00
9,525,000.00
2,250,000.00
4,750,000.00
400,000.00
1,440,000.00
1,000,000.00
2,040,000.00
3,000,000.00
5,400,000.00
5,250,000.00 40, 40,900,000
94,875,000.00
14,720,000.00
* Refractory brick, glass liquid and glass wool are structural material composition located deep inside aiming at ensuring maximum burning temperature of the kiln and products with highest quality (activated carbon) due to the following effects: -
Completely preventing the inside heat from releasing
-
Absorbing and storing heat inside the kiln to reach maximum temperature degree.
-
Assisting the kiln to have high refractoriness and resistance against cracks on the wall inside the kiln.
-
The rest material is the kiln frame
o During burning, there should be two project staff taking turns to be present at the workshop, to provide instruction on techniques of anaerobic burning to the building workers.
o Workshops have searched and mobilized skilled brick-layers on-site to carry out construction: Each workshop hires 1 group of workers to carry out construction; these groups have different capability, leading to delivering kilns with different quality. On the other hand, due to research activities for learning experience performed after each kiln building, the one which was built later has better quality and lower construction fees than the previous one: Kiln X4: -
After exchanging and reaching agreement with workshops, the research team and X4 made first construction plan of only a simple kiln. After finishing the kiln, they had trial burning performed for a period. X1 was only built after exchanging and drawing experience of X4 first kiln.
Kiln X1: -
X1 was built as a double kiln, with thicker composition to ensure its tightness and firmness. The cost to build this kiln is equivalent to 80% of X4 cost (for each kiln).
Kiln X5: -
After firing X1 for two periods, the research team together with workshops reviewed coal quality, discussed the kiln structure, firing technology and recognized that more studies need to be done on technology of building kiln and burning coal in Lam Dong province, before building a kiln in X5.
-
After studying more about techniques of building kiln in Lam Dong and from advices of the experts visiting the workshop, it is necessary to change its design (building the kiln in round or ellipse shape) to ensure higher temperature inside the kiln. However, this shape of kiln can lead to difficulty in techniques of building the cover, technology that requires skilled workers with much experience in doming and having enough care in their work.
2. Carrying out first production periods and checking coal quality a. Building and performing burning trials in X4 kiln : 1. From 20/1 to1/2 building simple kiln in X4 (Dien Trung commune) -
Size of the kiln: + Inside: 2.7 x 1.5 x 1.5 m + Outside: 4 x 2.8 x 2.0 m.
-
Structure: + The first layer: 24 cm fire-resistant brick + The second layer: glass wool of 5 cm thickness + The third layer: kiln residues (slag) of 15 cm in thickness. + The forth layer: normal brick for kiln wall of 21 cm in thickness. + Parabolic-shaped dome in 4 layers with domed frame made of iron.
o Expense details of building X4: No. I 1 2 3 4 5 6 7 8 II
Details Materials Refractory brick Glass liquid Asbestos fiber 3-mm iron sheet Normal brick Cement Sand Kiln residues Delivery Total Total
Unit
Amount
Unit price
Brick unit Kg kg m2 Brick unit Ton Trip Trip Trip
2000 200 200 10 4000 1 1 1 1
3,500.00 2,500.00 10,000.00 250,000.00 450.00 750,000.00 200,000.00 900,000.00
Total 16,150,000.00 7,000,000.00 500,000.00 2,000,000.00 2,500,000.00 1,800,000.00 750,000.00 200,000.00 500,000.00 900,000.00 4,100,000.00 20,250,000.00
Situation of burning trial: After finishing the kiln, the research team dried it in one day, then performed the first burning trial: o During burning trial, the research team often exchanged with many people with much experience in producing brick and ceramic to identify accuracy of the building techniques and draw experience for burning and burning technology.
o Differences of products which are burned from different kinds of materials (comparison made on periods of the kiln X4: an amount of 5,5m3 materials) Kinds of material Dry bamboo knots 30%
Kg of loaded material 1,5 tons
Fresh 1,8 tons bamboo knots Fresh and 2,5 tons small poles
Time of burning
Time of Rate of cooling products
48 hours
72 hours
30%
72 hours
98 hours
22%
86-92 hours
98 hours
20%
Note Small amount of loaded material, short time of burning, low quality products (coal temperature reach about 300oC) Products are not evenly burnt with quite low quality (about 400oC≈ To charcoal) Products are evenly burnt with good quality, temperature inside the kiln is quite high: (600oC≈ To low quality activated carbon)
The above table is based on realistic calculation in X4 and from the certificate of quality control done by Quang Ninh company of quality verification. This table shows that: -
If the material for burning is bamboo knots, bottoms obtained from by-products of chopstick and slats for flooring production, product quality will not be high because this material is not equal in terms of freshness and age of culms, leading to not enough temperature inside the kiln.
-
However, this material is available and cheap so it could be used for producing charcoal instead of wood coal (this could be a potential product replacing wood coal when this production is being limited due to risk of deforestation and forest-fire from coal fire).
-
If fresh and small bamboo poles are used as material for burning, coal can reach high quality, with the temperature similar to that of activated carbon. This product can become activated carbon, a product with very high value and demand (for exportation) through one more step of activation. Despite the availability and not really high value of this plant, it is necessary to make quick collection and careful selection to ensure both quality and freshness. Kiln X4-1 - Time of burning: 45 hours - Time of cooling: 4 days
-
Amount of obtained products: 242 kg. (30% of the kiln is not usable, not burnt)
Table of specific expense estimate
Details Unit Loaded material Kg Time of burning + Hour cooling Labor of burning Labor Firewood for burning Kg Total expense Obtained product Kg
Amount 1,395 141 hours
Unit price 200
Total 279,000
8 350
30,000 200
240,000 70,000 587,000
240
+ State of product amount and quality: Because the kiln stopped production one week earlier, the material for burning which is mainly bamboo knot, top and root obtained from chopstick production has become dry by 30-40%. Therefore, the material for loading only weighs 1395 kg/5.5m3. It is partly due to the fact that the kiln is still wet, because newly built. Another reason is that after 43 hours of burning, due to lack of experience, the research team had the kiln covered so soon. That leaves an amount of not yet burnt material (30% the total amount of material). The obtained products weigh 240kg, equivalent to 17% of material (which, by deduction, only reached about 300oC). (After discussion to draw experience, the research team and workshop owners agreed that: Only using bamboo bottoms as material for burning and it will be burnt until green smoke and white powder are seen around the chimney). •
Alternating material:
After gaining experience from the first burning period, there are changes as follows: -
Kilns X4-2: Root + 200kg fresh pole
Details Loaded material (root + knot) Time of burning + cooling Labor of burning Firewood for burning Total expense Obtained products -
Unit Kg Hour Labor Kg
Amount Unit price 1,555 200 205 12 30,000 600 200
Kg
368
Total 311,000.00 360,000.00 120,000.00 791,000.00
Because loaded materials are fresh bamboo knots + poles which weigh more than that in X1, there is a higher amount of material compared to X1 (160 kg)
-
Due to experience gained from the previous one, the burning process is carried out more perfectly; however, the temperature fails to reach maximum degree, that leaves an amount of 10-15% material in the kiln undone and the obtained product is 368kg = 23,7%, (This amount still includes some undone material which released smoke while being burnt), the kiln only reached temperature of 350400oC.
-
Kilns X4-3: Material is fresh and small poles with thick wall
Details Loaded material (bamboo bottoms + knots) Burning + cooling time Labor for burning Amount of burnt firewood Total expense Obtained product
Unit Kg
Amount 2,606
Hour Labor Kg
283 12 750
Kg
564
Unit price 250
30,000 200
Total 651,500 0 360,000 150,000 1,161,500
-
Burning material for kiln X4.3 is small poles which are older than 3 years with thick wall, and completely fresh. Thus, the total amount of material loaded into the kiln reached 2606 Kg, twice as much as it was in kiln 1.
-
Due to fresh and old enough material and a longer time of burning, kiln 3 produces good quality. There is only 5% of those lying the bottom of the kiln which is not burnt completely.
-
Besides, 564kg of products reach high quality (checking quality in Quang Ninh shows that coal obtained from his kiln reaches the temperature of 600oC). Some is up to 7800kj/kg (Material coal accepted in Japan and Korea is 6000-6500kj/kg)
b. Building kiln and carrying out trial in the workshop X1: Double kiln - Thien Phu. Construction of kiln 1 began after the first period of kiln X4 was finished (in order to redesign the suitable appearance, wall and gate). Its wall is thicker than that of X4 by 15cm; the gate for loading material is different of the burning gate: -
Size of the kiln: + Inside: 2 x (2.5 x 1.5 x 1.5 m) + Outside: 4 x 5.4 x 1.8 m
-
Structure:
+ The first layer: 24 cm fire-resistant brick + The second layer: glass wool of 5 cm thickness + The third layer: kiln residues of 15 cm in thickness. + The forth layer: normal brick for kiln wall of 21 cm thickness. + Parabolic-shaped dome in 4 layers with domed frame made of iron. Table of construction fees of anaerobic No. I 1 2 3 4 5 6 7 8 II Total
Details Materials Refractory brick Glass liquid Asbestos fiber 3-mm iron sheet Normal brick Cement Sand Kiln residues Delivery
Unit Brick unit Kg kg m2 Brick unit Ton m3 m3 Trip
burning kiln
Amount 3500 200 300 18 7000 2 8 8 1
Unit price 3,500.00 2,500.00 10,000.00 250,000.00 500.00 750,000.00 80,000.00 80,000.00 1,500,000.00
Total
(double kiln) Total 28,030,000.00 12,250,000.00 500,000.00 3,000,000.00 4,500,000.00 3,500,000.00 1,500,000.00 640,000.00 640,000.00 1,500,000.00 5,370,000.00 33,400,000.00
State of burning trial : Specific detail of first burning cycle of X1 kiln (X1-1)
Details Loaded material Time of burning + cooling Labor for burning Firewood for burning Total expenses Obtained product
Unit X1 .a Kg 1,40 5 Hour 183 Labor 14 Kg 450 Kg
Amount Unit X1.b Total price 1,61 3,015 200 0 183 182 14 30,000 900 200 450
Total
603,000 0 420,000 180,000 1,203,000
450
+ State of product amount and quality: The material used for loading is bamboo bottoms, knots obtained from chopstick production but fresher than that used in X4 (its moisture content decreases by 2025%), so kiln Thien Phu reaches the weight of 3100kg/11m3. -
In the kiln 1.a (one of both kiln), material used is thin bamboo top knots, so that the material loaded into the kiln only weighs 1450 kg.
-
In the kiln 1.b, material used is thick bottoms and knots, so that the material loaded into the kiln reaches a higher weight, by 1610kg
Due to early coverage of the kiln, there is amount of non burnt material (20-30%), coal quality is low, obtained product amount is small (only 450 kg = 15% material). •
Alternating material: Thanks to experience gained from the first burning period, there are changes in the next periods as follows: Kiln X1- cycle 2: Fresh bamboo ends Details
Amount
Unit A
B
Total
Unit price
Kg
2100
2000
4100
200
Time of burning + cooling
Hour
231
219
231
Labor for burning
Labor
14
14
14
30000
420000
Kg
620
570
1190
200
238000
Loaded material
Total 820000 0
Firewood Total expense
1478000
Obtained products
290
Kg
270
o Materials used are completely fresh bamboo ends with thick wall, so there is a great amount of loaded material; however, it takes time to complete burning (50 hours longer than cycle1). o Age quality of bamboo poles are not equal, there are still many tender, spongy poles which make products at low quality. o Despite longer burning time than kiln 1, too thick wall leads to many non burnt materials, of which the rate is rather high (25-30%) with the temperature inside the kiln of only 450oC.
Kiln X1- Cycle 3: Fresh bamboo poles type 3-4 (circumference < 27-30 cm) Details Loaded material
Amount
Unit Kg
Unit price Total
A
B
Total
1850
1800
3650
200
730,000
Time of burning + Hour cooling
207
196
207
Labor for burning
Labor
14
14
14
30000
Firewood for burning
Kg
550
480
1030
200
206,000
Total expense Obtained products
420,000 1,356,000
Kg
330
320
650
o Thanks to experience gained from the 2 previous kilns (cycles), the material of
kiln 3 was completely burnt. Only 10% of poles lying in the kiln bottom is not completely burnt (due to the too high design of the chimney gate and lack of an iron support in the kiln bottom). o Product rate of kiln 3 reaches up to 18% excluding the non burnt part. Quality
obtained is high, with the temperature inside the kiln of 550oC (by deduction). Kiln X1- cycle 4: Thick bamboo luong ends and knots which are split into laths Details
Loaded material Time of cooling
burning
Amount
Unit Kg + Hour
A
B
Total
Unit price
2000
2000
4000
200
289
284
289
Labor for burning
Labor
14
14
14
30000
Firewood for burning
Kg
650
600
1250
200
Kg
357
408
765
Total
Total expense Obtained product
o After discussion and experience exchanges, the team decided to have kiln X1 gate
lowered by 10 cm o Place the iron support in the kiln bottom so that the internal temperature can reach
the material layer lying in the bottom. o Based on experience of handicraft workers, the team waited until white smoke
was seen around chimney wall to have the kiln covered (combustion stopped). o All of the above aspects help to gain better quality of product than kiln 3 with
product rate of over 19% (excluding the non burnt part). Kiln X1-5: Bamboo luong ends and knots
Details
Unit
Loaded material Time of cooling
burning
Kg + Hour
Amount A
B
2100
2000
318
301
318 15
Labor for burning
Labor
15
15
Firewood for burning
Kg
550
500
Obtained product
Kg
400
390
Total
Unit price
Total
200
30000 200
o Product rate of kiln X1.5 reaches nearly 20% of loaded material, coal quality reaches activated carbon at low level (about over 600oC). o This is the kiln with highest quality compared to other kilns due to the experience gained from the previous ones. o After discussion, the team and workshop decided to leave one of two kilns (A) for burning trial a second time, in order to study activation capacity of the kiln: Kiln X1 – cycle 5 . A - Second burning cycle
Details
Unit
Amount
Note
Loaded material (charcoal)
Kg
400
From kiln X15.a
Time of burning + cooling
Hour
102
30+72
Labor for burning
Labor
3
Firewood for burning
Kg
200
Obtained product
Kg
350
To examine the activation capacity in the kiln (second burning cycle), the research team carried out: i. Coal gained after burning of kiln X1-5.A was left untouched in the kiln, the gate was largely open so that the water stream can be absorbed in 3 days before reburning. ii. Carrying out 30 hours of continuous burning so that charcoal can interact with water stream (H2O) and carbon dioxide (CO2) released from burning period at high temperature (kiln temperature) then covering for cooling in 3 days.
After unloading, according to visual comments of the team and workers of burning: Coal gained after re-burning is blacker, more spongy and lighter; however, it is necessary to have specialists to reexamine the accurate quality.
c. Establishment and burning trial of X5: carried out after first periods of kilns X4 and X1 and after visits to workshops and traditional kilns in Lam Dong: •
Establishment: Kiln X5: After 2-3 periods of burning carried out in kilns X1 and X4 together with experience gained from visits to kilns of coal burning of Da Lat company of urban sanitation and advices of some experts, there are changes in establishment of kiln X5 as follows: o Kiln was built in round (elliptical) shape – high dome. o Kiln volume is bigger than that of kiln X1 and X4 (11m3/1 kiln) o One of the two kilns was built with only one layer of fire-resistant brick and especially: After the research visit in Lam Dong, the research team realized that:
Each ton of material can produce 6-8% attar (essential oil) (equivalent to 60-80kg attar), an important income source in the process of coal burning.
Bamboo attar is a product with high economic value (price of exporting from China to Japan and Korea is about 1.2 USD – selling price in Vietnam is about > 10,000 VND/kg).
And market demand (in Japan, Korea) is very high (« buy all if available» – said staff of Da Lat company of managing urban facilities)
Design of the extracting system is simple, and experts from Da Lat company met, give enthusiastic instructions on extracting technology.
Therefore, the team decided to design a pilot system for bamboo attar production in kiln X5: Size of the kiln: + Inside: 2 x (3 x 2 x 2) m + Outside: 4.4 x 5.7 x 2 m -
Structure: + The first layer: 24 cm of fire-resistant brick
+ The second layer: glass wool of 10cm thickness. + The third layer: kiln residues of 15cm thickness. + The forth layer: normal brick for kiln wall of 21 cm thickness. + 4- layer dome built in parabolic shape with iron frame. + Attar (vinegar) extracting system with china (porcelain) pile of ϕ150 No.
Details
Unit
Amount
Unit price
Total
I
Materials
1
Refractory brick
Brick unit 4500
3,500.00
15,750,000.00
Glass liquid
Kg
300
3,500.00
1,050,000.00
2
Asbestos fiber
kg
400
10,000.00
4,000,000.00
3
3 mm iron sheet
m2
20
250,000.00
5,000,000.00
4
Normal brick
Brick unit 8000
500
4,000,000.00
5
Cement
Ton
3
750,000.00
2,250,000.00
6
Sand
Trip
2
200,000.00
400,000.00
7
Kiln residues
Trip
1
1,000,000.00
1,000,000.00
8
Delivery
Trip
2
1,500,000.00
3,000,000.00
II Labor
5,150,000.00
Total(I+II)
41,600,000.00
•
Specific details of burning the kiln
Kiln X5- Cycle 1 : Details Loaded material Time of cooling
burning
Unit Kg + Hour
Amount A
B
2600
3100
148
157
157 20
Labor for burning
Labor
20
20
Firewood for burning
Kg
750
900
Kg
76
100
Attar (vinegar)
Total
Unit price
Total
200
30000 200
176
o It is the first time of extracting attar without much experience; on the other hand, about 20% of loaded material as bamboo ends and knots is dry, these two elements lead to not high amount of obtained attar; however:
o Attar quality gained can meet exportation standard based on examine instruction of Da Lat company of managing urban facilities (pH level ranges from 3 to 4). o This amount of attar was sent as offer to several companies, among which a company based in Lao Cai (owned by Mr. Dan) agreed to buy at the price of 10.000 VND/kg; Mr. Dan promised to visit the workshop and apply for purchasing of all the attar extracted by us. 3. Conclusion: By April 30th, 2007, all the 3 workshops (X1, X4 and X5) had kilns built and 8 burning trial have been carried out. After burning, each place had exchange of experience performed between the research team and workshops owners, therefore: o Coal quality is always improved kiln after kiln. o Up to May 30th 2007, all workshops owners had mastered fundamental techniques of burning and monitoring methods for the highest quality. o In the last 4 kilns (cycles) in workshops X1 and X4, coal quality reaches at least 600oC (samples of X4-3 have been sent for examination) equivalent to temperature to obtain quite low quality activated carbon (>600oC). o In kiln X1-5, the second period of burning trial was carried out with success and produces high activated carbon: coal then produced is black, spongy, light (of course, it will be sent for examination of quality) o In kiln X5, attar extracting was carried out and produced 176 kg attar (vinegar) with accepted quality which was sent as offer and accepted by customer at the price of 10.000VND/kg (now pending for order from customers so that mass production (in large amount) can be carried out) 3.1 Comments on production expense and investment a. Investment efficiency o According to INBAR guidance disseminated in Internet together with requirements on product quality, the research team sees that investment in establishment of kiln and burning trial in workshops of the project is completely possible and beneficial: •
At the rate of 1/5 (5 kg material can produce 1 kg product) in coal production, even not mention attar extracting it can make profit (even selling charcoal at 2.500đ/kg),
•
However, for effective production, it is necessary to produce coal with high quality for consumption in exporting market: the lowest exporting price from Chinese enterprises to Japan and Korea market is currently 0.6 USD CIF/kg for normal bamboo coal.
•
If bamboo attar (vinegar) is added to final products, we will have more 2,000,0003,000,000 VND/5 tons of bamboo. (200-300kg attar) therefore, with the domestic selling price of 2000 VND/kg bamboo coal, we can gain total revenue on 6 tons of bamboo (including firewood) of from 4,000,000-5,000,000 VND, in which total production expense is only 2,000,000 VND (if end knots are used as material) and 3.500.000 VND (if tender bamboo plants are used as material).
b. Related impacts: •
Producing bamboo coal in Vietnam, especially in mountainous area of Thanh Hoa, can serve as an appropriate business method because it helps workshops take complete advantage of waste from chopstick, handicraft and flooring laths production (currently 40-60% is waste).
•
Additionally, there is much amount of small bamboo luong plants with low economic value which are often sold for column (pole) at 200-300 VND/kg. This kind of material is small but firm and has high life-expectancy (over 3 years), so it is very suitable for production of high quality coal. If this material is taken advantage for coal burning, it can bring about high economic value (exportation) to increase income of luong planters.
c. Possibility of implementation in a larger area: •
All of the materials used in kiln building are produced and sold in large amount nationwide, and can be easily purchased. Their price is not high (see details at the table of kiln building expense)
•
Especially, after visiting Lam Dong where there are many households producing activated carbon and charcoal from similar kilns using Japanese technology, the research team sees that: it is possible to reduce cost of kiln building, if we can take advantage of land position of the mountainous area to remove some layers but still ensure kiln and coal quality: Currently kiln X5 with the volume of 11m3, total building expense is about 25,000,000 VND (double kiln in X5 costs 41,600,000 VND)
If removing fire-resistant layer, each kiln with the volume of 10M3 only costs 10-12,000,000 VND. If digging a deep hole to build the kiln and only building a refractory layer, each kiln with the volume of 10M3 only costs 16-17,000,000 VND. •
Due to un-complicated technology of burning which can be transferred, together with the above estimated costs, it is possible to make application of coal burning technology at household level (group of households) (even including household with average income and nearly-poor households)
d. Production expense o After two first period of drying as well as testing for experience, from the third one, technology of burning has been perfected, burning kiln produces high quality coal, product rate is 22% (1 ton of fresh bamboo produces 220kg coal + 20-30kg attar). Coal burning can bring about high economic efficiency: o Kiln X4- Cycle 3 for ex. (have had quality examined) Total
Details
Unit
Amount
Unit price
Loaded material
Kg
2500
300
750,000
Labor for burning
Labor
8
30000
240,000
Firewood for burning
Kg
500
200
100,000
Kiln depreciation
Đ/cycle
1
87.000
Total expense Obtained product
1,177,000
VND
Coal Attar
87.000
Kg
2.250,000
500
2500
1,250,000
100
10.000
1.000,000
Profit (if completely sold)
1.073.000
o The above table is based on charcoal selling price in domestic market at lowest price (selling to Truong Phat activated carbon incorporated company - Bac Giang - this price has excluded delivery cost). The value can greatly increase through exportation. (0.5 US/kg – FOB Hai Phong) 3.2. Difficulties and risks (lessons of experience): -
This kiln is an anaerobic kiln with round shape, domed roof. This kiln can ensure tightness and endurance against push of pressure inside the kiln (caused by pressed
air in burning process). Therefore, skilled workers are needed for the construction, if there is any mistakes, it can lead to state of uncovered, cracked and even collapsed. -
If the chimney is too large, heat can be released quickly and conversely. These two states will lead to low quality of product (appropriate size of chimney: 7-10cm in height; 40cm in length).
-
If the kiln is covered too soon, there will not be enough heat that leads to low quality of product. If the kiln is covered too late, coal will be spoilt, leading to waste of material and fuel.
-
Due to a characteristic of bamboo coal of good absorbability, after a long time, this product will absorb humidity in the air that leads to low quality. Therefore, it needs storing in a dry and close environment so that it can not absorb humidity in the air.
3.3 Experience and considerations in terms of technology and techniques: a. In terms of construction: •
The kiln used for coal burning is anaerobic kiln which can resist heat and burn coal under method of heat distribution. Therefore, it requires that the following aspects should be ensured: -
Totally close: in order to prevent air circulation as well as heat from releasing in the process of burning and cooling.
-
Heat resistant (refractory): in the process of burning and cooling, temperature inside the kiln can reach over 1000oC, so kiln structure should have high capacity of heat-resistance, otherwise phenomenon of crack and damage can occur.
-
Quickly heat absorbent: because temperature and quality of coal will completely depend on kiln temperature, the inside wall the kiln must have the capacity of not only absorbing heat but also quickly absorbing heat so that kiln temperature can reach highest degree in the process of burning and cooling.
-
Resistant against internal pressure: during burning and cooling, because the kiln is completely close and the inside temperature quickly increases, the air in the kiln is quickly elastic that creates a very strong push from inside. Therefore, to ensure that the kiln is not cracked, broken or even exploded, the kiln wall structure must be really thick and firm (metal support structure
bearing high pressure should be placed in kiln wall and top at the end of building process). b. In terms of burning technology: The process of coal burning consists 7 steps in all:
Loading
Drying
120~150℃
Unloading - Cleaning – Packing
Pre-heat distribution
150~280℃~ 450℃
Cooling
Activation
280~450℃
Refining coal at high temperature
60℃ Over 450℃
Selecting material for loading: For products with high quality, materials selected should be fresh poles or fresh end knots of plants aged more than 3 years and not spongy. Drying: there is white smoke in this process (like colour of water). Pre-heat distribution: in this process, smoke is yellow, then changes into black and returns to yellow (this is also time of attar extracting). Activation: the smoke will change from light white into blue white. At the end of this process, white powder will dry water around the chimney opening that leads to the state that white powder is seen around chimney opening as smoke ash. This is the time for covering (cover the chimney opening first, kiln gate later)
Coal refining: while the kiln is being covered, coal is still in the process of heat distribution and heat release => kiln temperature continues to rise, if the kiln is completely close, at the end of this process, it can reach 1000oC. Cooling: after 3 days of refining, the kiln can be left gradually cool, or to make it quickly cool, they use cool water to continuously spill its top. Unloading: when the temperature decreases below 60°C, coal can be unloaded, then we clean soot on coal then process and pack as required by customers.
4. Proposals Although bamboo luong value chain has been developing and tends to completely alternate wood coal sector in many countries in the world, especially in Japan, Korea, Taiwan, China and European developed countries, it’s still a new sector in Vietnam, not only for customers but also for producers. Therefore, there still exists great challenges in techniques of kiln building and technology of coal burning for those who want to participate in this sector. Currently there are 2 workshops producing bamboo coal in small scale (one in Hoa Binh, another in Vinh Phuc), with different techniques of building burning kiln. There are some bases and individuals who are studying with the expectance to participate in this new and potential sector. They are also studying techniques of building and technology of burning from many different sources. With experiences gained from trial process, the research team makes some proposals as follows: 4.1 Proposals in terms of construction: •
There are 2 kinds of kiln that can be used for burning bamboo coal Normal kiln - producing low quality coal - this kind of kiln can be built by local farmers or inhabitants because the construction techniques aren’t complicated and it can be used for burning any type of material. -
This is an anaerobic kiln without refractory material: used for burning mixed materials of which age and quality can not be identified (end knots, byproducts, wastes from chopstick and toothpick production) - these kinds of material hardly produce products with high quality and high selling price.
-
For this kiln, in the process of burning, the temperature inside can not exceed 500-600oC so normal brick mixed with soil can be used to build the wall inside the kiln, while brick, sand and normal cement can be used to build the surrounding wall.
-
With the above structure, 01 kiln with the volume of 10m3 only costs 12.000.000 VND for construction expenses.
Refractory kiln - producing high quality coal - activated carbon - this kind of kiln should only be built by enterprises or concentrated workshops due to many advanced techniques: -
This kind of kiln has the capacity of high heat accumulation and resistance so refractory brick, glass wool and glass liquid are necessary materials for construction.
-
Each refractory kiln with the volume of 10m3 costs a bit higher than 30.000.000 VND for construction expenses. •
•
Both of the above kilns can be built by two ways: -
Form 1: Kiln wall has rectangular shape with dome - an advantage of this kind of kiln is its firm structure, easily built but limited in the capacity of heat accumulation.
-
Form 2: Kiln wall has round or elliptical shape with dome - this kind of kiln has an advantage of higher heat accumulation but skilled workers are required for construction.
To ensure closeness as well as heat accumulation, both of the above kilns must be built with really thick wall (as thick as possible).
•
Kiln wall is divided into 3 layers - each layer is 20-25cm thick: -
The first layer: made from fire-resistant material or dense brick.
-
The second layer: made from kiln residues mixed with soil.
-
The third layer: made from brick - cement - sand as a surrounding wall.
-
It is necessary to carry out building trial of 2 kilns of normal kind (without refractory material) for examining and testing the possibility of developing this kind of kiln in the community.
-
It necessary to supplement a system of attar extracting for all kilns to take complete advantage of products.
-
Carrying out building trial of a kiln producing high quality activated coal (self-activating through a steaming system or carbon dioxide in the close refining process)
4.2 Proposals in terms of burning techniques •
Material should be as fresh as possible (high humidity content).
•
In the process of burning, workers have to continuously monitor smoke state to accurately identify coal state in the kiln.
•
Kiln should be covered only when, or right after, white powder is seen around the chimney. Carrying out production trial of high quality activated coal (self-activating through a second burning or a steaming system or carbon dioxide in the close refining process)
Annex Kiln X4- cycle 2:bamboo ends +200kg fresh pole Details Loaded material
Unit Amount Kg
1555
Time of burning + cooling Labor for burning
Hour Labor
205 12
Firewood for burning
Kg
600
Pack Deduction
Piece KG
25
Unit price 2 00 30,0 00 2 00 1,5 00
Attar (4% total material)
VND VND kg kg
311,000.00 360,000.00 120,000.00 36,800.00
368 60
Total expense Obtained product Coal
Total
368 62
2,0 00 10,0 00
Net profit
22,080 849,880.00 1,161,500.00 736,000.00 622,000.00 311,620.00
Kiln X4- cycle 3: fresh small bamboo poles with thick wall Loaded material
Kg
2606
2 50
651,500.00
Time of burning + cooling Labor for burning Firewood for burning
Hour Labor
283 12
Kg
750
Pack
Piece
38
Deduction
KG
Total expense Obtained product Coal
VND VND kg 564
Attar (4% total material)
kg
0.00 30,0 00 2 00 1,5 00
360,000.00 150,000.00 56,400.00
564 60
104
Net profit
2,0 00 10,0 00
33,840 1,161,500 2,170,400 1,128,000 1,042,400 1,008,900.00
Kiln X1- cycle 3: Fresh bamboo poles type 3-4 Details
Loaded material Time of burning + cooling Labor for burning Firewood for burning Pack Deduction Total expense Obtained product Coal Attar (4% total material) Net profit
Unit
Amount Unit A B Tota price l Kg 1 1 3650 200 850 800 Hour 207 196 207 Labor 14 14 14 30000 Kg 550 480 1030 200 Piece 43 1500 KG 650 100 VND VND kg 330 320 650 2,0 00 kg 74 72 146 10,0 00 VND
Total
730,000 0 420,000 206,000 65,000 65,000 1,486,000 2,760,000 1,300,000 1,460,000 1,274,000
Kiln X1- cycle 4: Laths of thick bamboo luong knots Loaded material
Kg
2
2 4000
200
800
000 000 289 284 289
Time of burning + cooling
Hour
Labor for burning
Labor
Firewood for burning
Kg
Pack
Piece
Deduction
KG
Total expense
VND
Obtained product Coal
VND kg 357 408 765
Attar (4% total material)
kg
Net profit
VND
14
14
,000
14 30000
650 600 1250
200
51
1500
765
100
80
80 160
2,0 00 10,0 00
42 0,000 25 0,000 7 6,500 7 6,500 1,62 3,000 3,130,000 1,53 0,000 1,60 0,000 1,507,000
Kiln X1- cycle 5: Bamboo luong ends and knots Loaded material
Kg
2 2 4100 100 000 318 301 318
Time of burning + cooling
Hour
Labor for burning
Labor
Firewood for burning
Kg
Pack
Piece
Deduction
KG
Total expense
VND
Obtained product Coal
VND kg 400 390 790
Attar (4% total material)
kg
15
15
200
15 30000
550 500 1050
200
53
1500
790
100
84
80 164
2,0 00 10,0
82 0,000 45 0,000 21 0,000 7 9,000 7 9,000 1,63 8,000 3,220,000 1,58 0,000 1,64
00 Net profit
VND
•
0,000 1,582,000
Rate of attar extracting estimated on material of end knots (20% of them is dry) is 4%.
•
Rate of attar extracting estimated on material of complete fresh poles is 7%.
•
Domestic selling price of charcoal is 2000 VND/kg (excluding delivery cost).
•
Selling price of attar to exporting companies is 10.000 VND/kg.
According to the above detailed tables: if charcoal produced is only for sale in domestic market, it is necessary to extract attar for economic benefits (it can be much higher through exportation)
