The full set of the ammonia injection equipment (Figure 6-30), developed by the Non-conventional Feed Institute of China Agricultural University, consists of an ammonia bottle, a high pressure hose, a flow meter, a low pressure hose (rubber hose) and an ammonia spear. Protective equipment (gas mask, rubber gloves and boots) must be used.
Figure 6-30. Ammonia application equipment
KEY: 1. Ammonia bottle; 2. Low pressure meter; 3. High pressure meter; 4. Flow meter; 5. Safety plug; 6. High pressure hose; 7. Valve; 8 Injecting spear; 9. Low pressure hose.
During treatment, the ammonia bottle should be laid horizontally, keeping vertically the line connecting the two valves: the upper for gas and the lower for liquid. One end of the high-pressure hose is connected to the lower valve and the other end to the high pressure end of the flow meter. One end of the low pressure hose is connected to the low pressure end of the flow meter and the other end to the ammonia spear.
After connecting the full set, operators should first put on their protective equipment: gas mask, rubber gloves, boots and suit. Second, the ammonia spear is inserted into the straw stack, about 0.5 m from the ground. Third, the lower valve is slowly unscrewed to inject the appropriate dose of ammonia according to the amount of straw. When finished, the valve is closed, but the spear kept in place for 4-5 minutes to allow ammonia left in the hose and spear to flow to the straw. Finally, the spear is pulled from the stack and the injection hole sealed with glue or tied with a string.
Using the flow meter, ammonia can be injected into the stack directly from an ammonia truck, avoiding ammonia transfer from tank to bottle. As a result, working efficiency is increased.
Anhydrous ammonia is the cheapest ammonia source, and, for this reason, treating straw with anhydrous ammonia has been advocated. However, aqueous ammonia is toxic, volatilizes easy and causes burns, thus pressure containers are required for transport and storage. It is necessary to build an anhydrous ammonia supply system. Considering the practical radius of service and amount to be used, a county-level ammoniation station might be needed. Functions of the station are to obtain ammonia in large quantities from chemical (usually fertilizer) factories in tank trucks, store it in large containers, distribute it in bottles and also to perform the injection into the straw at farmer level. At the same time, the station also can market other ammonia sources (e.g. urea) and ammoniation equipment.
Selection of equipment for transport and storage
Many types of transport and storage facilities for anhydrous ammonia have been manufactured in China, including ammonia tank trucks, containers and bottles, some of which are listed in Table 6-7. The 3-ton Dongfeng truck tank and the 7.2-ton Hongyan 19 truck tank have been selected as the main models to meet requirements in a flexible manner. Anhydrous ammonia containers are mainly used in ammoniation stations connected with an ammonia supply system. When selecting ammonia containers, cost and uniformity of ammonia delivery should be taken into account. Because anhydrous ammonia can be transferred directly from a tank placed on a truck body into bottles, tanks may not be required for a county-level ammoniation station if funding is adequate.
Table 6-7. Equipment sizes for ammonia transport and storage
|
Category |
Type |
Capacity |
|
Anhydrous ammonia tank trucks |
Dongfeng |
3.0 t |
|
Dongfeng-13 |
5.1 t |
|
|
Hongyan-19 |
7.2 t |
|
|
Hongyan-30 |
12.0 t |
|
|
Anhydrous ammonia containers |
6 m3 |
3 t |
|
16 m3 |
8 t |
|
|
25 m3 |
12.5 t |
|
|
50 m3 |
25 t |
|
|
Bottles |
800 litre |
400 kg |
|
400 litre |
200 kg |
|
|
40 litre |
20 kg |
When selecting ammonia bottles, the first factor to be considered is convenience for loading and unloading. Because hand tractors or small carts can easily transport a 400-litre (200 kg) ammonia bottle, they have been selected as the main type. The 40-litre (20 kg) bottles are well adapted for farmers ammoniating straw in stacks, because of their easy transport, loading and unloading. One 40-litre bottle can treat 700 kg of straw in a stack, avoiding weighing and other complex procedures, and it can be transported by bicycle. The Non-conventional Feed Institute of China Agricultural University and relevant factories have promoted the "one bottle, one stack" concept based on this small bottle, as recommended by FAO experts.
Ammonia transfer
One of the important roles of the ammoniation station is to transfer anhydrous ammonia from the truck tank to bottles. If the liquid level in the tank is nearly equal to that in the bottle, ammonia can not flow by gravity and a compressor is needed. Ammonia compressors are available in Denmark. In China, an ammonia compressor has been obtained by redesigning the corrosion-prone parts of an air compressor.
The Non-conventional Feed Institute of China Agricultural University has successfully developed an anhydrous ammonia flow meter. The system of transferring ammonia from truck tank to bottle is shown in Figure 6-31. The ammonia transferring procedure is:
A high-pressure hose is attached between the liquid valve on the truck tank and the bottles. A gas hose is attached between the gas valve on the truck tank and bottle through the compressor.
The gas valve on the truck tank is opened and checked for any leakages (splits or cracks along the hose).
The bottle's gas valve is opened, then the truck tank's valve, and a check is made for leakage along the hoses.
The liquid valve on the bottle is then opened.
The compressor to transfer ammonia from the truck tank to the bottle is started before the liquid is released into the hose.
Figure 6-31. The transfer system from the truck tank to the ammonia bottle
KEY: 1. Ammonia truck tank; 2. Ammonia compressor; 3. Ammonia bottle.
It is better to place an ammonia pressure meter on the bottle's gas valve, and to compare its value with that on the tank. If the pressure of the tank is consistently more than that of bottle, this means the system is working fine.
Layout of ammoniation station
Determining service scale and equipment. The technology of treating straw with anhydrous ammonia is already mature. The ammonia dosage should be 3 percent of the straw dry weight. It is estimated that 1.5 tonne of ammoniated straw are enough for one head of cattle a year. Table 6-8 is based on an assumption of 1.5 tonne per head per year, and 300 working days for the ammoniation station a year. Table 6-7 indicates that a farm with 10 000 beef cattle needs 15 000 tonne of ammoniated straw, requiring 450 tonne of anhydrous ammonia annually. The quantity of ammoniated straw and ammonia for other animal species can be estimated by converting other livestock units into cattle units. The type and number of ammoniation facilities are determined by the quantity of anhydrous ammonia needed per year. The number of trips is estimated based on truck tank size and distance between the station and the fertilizer factory.
Table 6-8. Relationship between cattle member, straw amount, anhydrous ammonia and facilities required
|
Cattle |
Treated straw |
NH3 need(1) |
Trips of 3-ton tank truck |
Trips of 7.2-ton tank truck |
No. of 200 - kg bottles needed |
||
|
Per year |
Per day |
Per year |
Per day |
||||
|
10 000 |
15 000 |
450 |
150 |
0.5 |
62.5 |
0.200 |
15 |
|
20 000 |
30 000 |
900 |
300 |
1.0 |
125.0 |
0.420 |
30 |
|
30 000 |
45 000 |
1 350 |
450 |
1.5 |
187.5 |
0.625 |
45 |
|
40 000 |
60 000 |
1 800 |
600 |
2.0 |
250.0 |
0.830 |
60 |
|
50 000 |
75 000 |
2 250 |
750 |
2.5 |
312.5 |
1.040 |
75 |
|
60 000 |
90 000 |
2 700 |
900 |
3.0 |
375.0 |
1.250 |
90 |
|
70 000 |
105 000 |
3 150 |
1 050 |
3.5 |
437.5 |
1.460 |
105 |
|
80 000 |
120 000 |
3 600 |
1 200 |
4.0 |
500.0 |
1.670 |
120 |
|
90 000 |
135 000 |
4 050 |
1 350 |
4.5 |
562.5 |
1.875 |
135 |
|
100 000 |
150 000 |
4 500 |
1 500 |
5.0 |
625.0 |
2.080 |
150 |
NOTES: (1) As anhydrous ammonia.
The total volume of bottles should be double that of the tank to ensure thorough discharge. That means that half of the bottles will be with farmers and the other half on station. The bottles should be recycled to accelerate turnover and improve working efficiency. In addition, small ammonia bottles holding 40 litre (20 kg) should also be available to facilitate farm work. At the station, ammonia is transferred from the truck to bottles through a hose controlled by a platform scale. Because the amount of ammonia remaining in each bottle varies, it is impossible to estimate the total amount transferred by a flow meter. At the same time, the amount in each bottle is an important consideration for safe transport, so flow meters are unsuitable for stations.
Equipment and its cost. Equipment and its cost in a typical ammoniation station serving 20 000 beef cattle are listed in Tables 6-8 and 6-9. The ammoniation of 30 000 tonne of straw requires 900 tonne of anhydrous ammonia, which can be transported by a 3-ton truck tank once daily (Table 6-7). At the same time, 30 small bottles with 200 kg and other facilities, such as a farm vehicle, a small four-wheel tractor and trailer, are also needed. Appropriate schemes can be planned for various sizes of ammoniation stations, based on the data in Table 6-9.
Table 6-9. Equipment and cost for an ammoniation station serving 20,000 cattle
|
Equipment item |
Number needed |
Cost per unit |
Total cost |
|
3-ton truck with ammonia tank |
1 |
6.95 |
6.95 |
|
200-kg anhydrous ammonia bottle |
30 |
0.20 |
6.00 |
|
Farm vehicle |
1 |
4.50 |
4.50 |
|
Weighing scale (500 kg capacity) |
1 |
0.05 |
0.05 |
|
Loading and unloading frame |
1 |
0.20 |
0.20 |
|
Small four-wheel tractor |
1 |
0.70 |
0.70 |
|
Trailer for small four-wheel tractor |
1 |
0.25 |
0.25 |
|
Hand trolley |
1 |
0.05 |
0.05 |
|
Other |
|
|
0.50 |
|
Total |
|
|
19.20 |
Personnel. For a typical ammoniation station serving 20-50 000 cattle, 5-7 persons are needed (1 manager, 2 drivers, 2-4 operators).
Construction requirements and plan layout. Each ammoniation station should be designed specifically for the service scale and land and equipment available. An ammoniation station for a 20-50 000-cattle catchment (typical county level) shows typical construction requirements and layout (see Figure 6-32). The area is 40 ¥ 40 m (1 600 m2). In order to quickly transfer ammonia from the tank truck to bottles, the difference in height between tank and bottle should be adequate. Thus, a 1-m platform (10) is suitable for loading and unloading. It has an inspection pit for checking or repairing vehicles. The platform can also be used for general loading and unloading operations. A shed beside the platform (8) holds 125 ammonia bottles (200 kg each), standing vertically. At the end of shed (8) there is a storeroom (9) with a separate wall. A tractor can be driven close to shed (8). One person can load and unload with the aid of a movable gallows frame. The office (1) is used as a check point and for sales (urea, ammonia filling equipment and plastic sheets). The other rooms are an office (2), a meeting room and manager's office, living rooms (3), toilet (4), large (5) and small (6) garages and stores for urea, ammonia filling equipment and plastic sheets (7). (11) are flower beds, and (12) are trees.
Figure 6-32. County-level ammoniation station
The living and administrative areas are located at the corner opposite to the ammonia source to minimize effects on people. Doors on opposite sides of the compound facilitate access of trucks and tractors. The whole yard is large enough for vehicles to turn around without the need to reverse.
A typical budget for the construction of a county-level ammoniation station is given in Table 6-10.
Table 6-10. Budget for construction of a county-level ammoniation station
|
Building |
Size |
Unit price |
No. |
Total cost |
|
Office and dormitory |
3.0 × 6.0 |
3 000 |
7 |
21 000 |
|
Truck garage |
3.5 × 11.0 |
5 000 |
1 |
5 000 |
|
Car garage |
4.5 × 6.5 |
3 500 |
1 |
3 500 |
|
Shed for urea storage |
9.0 × 6.5 |
6 000 |
1 |
6 000 |
|
Platform for loading and unloading |
15.0 × 4.0 × 1.0 |
3 000 |
1 |
3 000 |
|
Shed for ammonia bottles |
3.0 × 11.0 |
5 000 |
1 |
5 000 |
|
Toilet |
4.5 × 6.0 |
1 000 |
1 |
1 000 |
|
Road, water and electricity facilities |
|
|
|
10 000 |
|
Total |
|
|
|
54 500 |
Economic assessment. The cost estimation is done taking into account the following factors:
Depreciation of equipment and buildings over 10 years
Wages at ¥ 250 per person per month
Transport costs of ¥ 0.03/ton/km
5% profit on turnover
Aqueous ammonia cost of ¥ 1.4/kg
The economics of a county-level ammoniation station serving 20 000 cattle are presented in Table 6-11. The price of aqueous ammonia reached ¥ 0.1434/kg after transport, storage and distribution by the ammoniation station. Except for personnel wages and transport fees, other costs were ¥ 87 050 per year. Investment in equipment and building construction was ¥ 24 500. It is estimated that 3 years are needed to recover the investment. The cost of buying the land and electricity also should be taken into account. In addition, possible additional income from sales of urea, ammonium bicarbonate and ammonia equipment is not considered.
Table 6-11. Economics of a county-level ammoniation station for 20,000 cattle
|
Cost |
Yearly depreciation |
Wages |
Transport cost |
Profit |
Total |
|
|
Equipment |
Buildings |
|||||
|
Total |
45 250 |
4 850 |
21 000 |
67 500 |
157 000 |
|
|
Per kg of aqueous ammonia |
0.1213 |
0.0054 |
0.0167 |
0.0300 |
0.0700 |
0.1434 |
NOTE: (1) Aqueous ammonia sold annually is 900 tonne. (2) All values are in ¥
County-level ammoniation station in parallel to the ammonia supply system in a fertilizer factory. Such a station can be built on an empty area inside or close to the fertilizer factory. A tank, with a volume 5 times that of expected daily use, can be connected to the ammonia source in the factory. The capacity for ammonia delivery can be increased with a larger tank, but the cost also increases. For a station serving 20 000 cattle, a 12.5 tonne tank is preferred. It costs about ¥ 52 000. Having a station associated with the fertilizer factory saves not only on transport but also on wages and building cost. The economic assessment can be done on a similar basis to that above.
Township-level ammoniation station. Such an ammoniation station would be responsible for supplying ammonia for straw ammoniation. It can be part of the agricultural machinery service system or can be contracted to a professional farmer. Most of the equipment required, listed in Table 6-12, can be shared with the agricultural machinery station.
Table 6-12. Equipment for a township-level ammoniation station
|
Equipment item |
No. needed |
Unit cost (¥) |
Total cost (¥) |
|
Small four-wheel tractor |
1 |
7 000 |
7 000 |
|
Trailer for tractor |
1 |
2 500 |
2 500 |
|
200 kg ammonia bottle |
2 |
2 000 |
4 000 |
|
Ammonia filling and protective equipment |
1 |
750 |
750 |
|
Weighing scale (500 kg capacity) |
1 |
500 |
500 |
|
Total |
|
|
14 750 |
The village-level ammoniation station requires 3 persons (¥ 200/month each). The running cost for a small four-wheel tractor is ¥ 30/day. Anhydrous ammonia sales are 400 kg a day, or 120 tonne a year. The depreciation of equipment is calculated over 10 years. Cost of anhydrous ammonia handling is ¥ 0.147/kg.
Assuming that the cost for transport and storage of anhydrous ammonia is ¥ 0.227/kg for county and township-level ammoniation stations, and that 1 kg of anhydrous ammonia can treat 33.3 kg of straw, then the cost of treated straw is ¥ 8.3/ton. This estimation is based on general 1998 prices. When planning an ammoniation station, the economic assessment should be based on local costs.
