Koji KOBAYASHI*
Kazushige KUROSAWA*
Motoshi ARIHARA*
Wenjie YANG**
Zhibao ZHANG**
Binglai ZHAO**
*
Ebara Environmental Plant Co., Ltd.
**
Ebara Qingdao Co., Ltd.
Fig. 1 Nanchang Waste-to-Energy Plant
Nanchang City, the capital of Jiangxi Province, China, is the center of politics, economy and culture as well as strategic point of Jiangxi traffic. Poyang Lake, the largest freshwater lake in China, located in the northeast of the city. The city has an area of 7 402 km2 with a population of approximately 5.2 million. Nanchang has a monsoon-influenced humid subtropical climate with the annual average temperature of 16.8 °C. It is rainy season from April to June and approximately 80% of the annual precipitation falls during this period.
Nanchang is well known as a historical and cultural city built about 2200 years ago during the Han dynasty, and it is the largest industrial city in Jiangxi Province now.
Figure 2 shows the location of Nanchang in China.
Fig. 2 Location of Nanchang, Jiangxi, in China
Table 1 shows the lower calorific values and composition of the waste in Nanchang.
| Item |
Low-calorific
value waste
|
Design waste |
High-calorific
value waste
|
| Lower calorific value | 4180 kJ/kg | 6270 kJ/kg | 8360 kJ/kg |
| Moisture content | 58.81% | 52.01% | 45.21% |
| Combustible content | 26.41% | 33.56% | 40.71% |
| Ash content | 14.78% | 14.43% | 14.08% |
| (1) Incinerator | |
|
Type:
|
EBARA HPCC (High-Pressure Combustion Control) grate-type incinerator
|
| Capacity: | 1200 t/d (600 t/24 h×2 units) |
| (2) Boiler | |
| Type: |
Natural-circulation water tube boiler with superheaters
|
| Capacity: | 53.2 t/h (Max. 58.5 t/h)×2 units |
| Steam condition: |
400 °C×4.0 MPaG (at the exit of the superheater)
|
| (3) Steam turbine generator | |
| Type: | Steam turbine (condensing type)＋generator |
| Rated power: | 12 MW×2 units |
| (4) Flue-gas treatment facility | |
| Flue-gas treatment system: | |
|
Semi-dry type system (slaked-lime slurry spraying) ＋dry type system (slaked-lime injection)＋activated carbon injection＋bag filter
|
|
| (5) Stack | |
| Type: |
External wall - Reinforced concrete structure Internal cylinder - Steel
|
| Height: | 80 m |
| (6) Emission values [flue gas from stack] | |
|
Inside [ ] are the values converted to the standard oxygen concentration used in Japan*1.
|
|
| Dust: |
Less than 80 mg/m3 (NTP) (O2 11% equiv.)
[Less than 72 mg/m3 (NTP) (O2 12% equiv.)] |
| Sulfuroxide: |
Less than 260 mg/m3 (NTP) (O2 11% equiv.)
[Less than 81.9 ppm (O2 12% equiv.)] |
| Nitrogen oxide: |
Less than 400 mg/m3 (NTP) (O2 11% equiv.)
[Less than 175.4 ppm (O2 12% equiv.)] |
| Hydrogenchloride: |
Less than 75 mg/m3 (NTP) (O2 11% equiv.)
[Less than 41.4 ppm (O2 12% equiv.)] |
| Carbonmonoxide: |
Less than 150 mg/m3 (NTP) (O2 11% equiv.)
[Less than 108 ppm (O2 12% equiv.)] |
| Dioxins: |
Less than 0.1 ng-TEQ/m3 (O2 11% equiv.)
[Less than 0.09 ng-TEQ/m3 (O2 12% equiv.)] |
Fig. 3 Flow sheet of plant
In China, different from Japan, construction of Waste to Energy Plants is often is undertaken by the SPC itself which secures the project. Consequently, we are responsible for the basic design (including a part of detailed design) of the incineration system, delivering main equipment (grates, hydraulic drive unit, burners, ACC system, and waste hopper level sensor), and dispatching supervisors.
The following is guaranteed items and values:
| (1) Annual total operation hours | ：8 000 hours or longer |
| (2) Operating load (incineration amount) range | ：60 to 110% |
| (Within 2 hours/day for 110% load) | |
| (3) Furnace outlet temperature | ：850 °C or higher, for 2 seconds or longer |
| (4) Ash ignition loss | ： 3% or less |
| (5) Boiler efficiency | ：80% or higher |
| (6) Grate replacement ratio | ：Less than 1% for 8 000 hours in operation
Less than 2% for 16 000 hours in operation
Less than 2.5% for 24 000 hours in operation
Less than 3% for 32 000 hours in operation
|
Fig. 4 Grate installation
Fig. 5 Waste feeder installation
Fig. 6 Structure of the 4-row grate incinerator
Fig. 7 Situation of combustion
Fig. 8 Bottom ash discharger installation
| Position |
Combustion grateⅠ
|
Combustion grateⅡ
|
| WEIHAI without bearing cooling | 162 | 152 |
| NANCHANG with bearing cooling | 111 | 109.5 |
| Temperature difference | 51 | 42.5 |
Fig. 9 Trend of NOx with flue gas recirculation
Fig. 10 Trend of furnace outlet temperature and steam generation
| Test item | Unit | Guaranteed performance | No.1 furnace | No.2 furnace | Conclusion |
| Volume of waste treatment | t/d | 600.0 | 665 | 605 | Qualified |
| Boiler total efficiency | % | ≧80.00 | 80.25 | 82.6 | Qualified |
| Steam flow | t/h | 53.2 | 54 | 54.13 | Qualified |
| Steam temperature | ℃ | 400 （＋10，−5） |
400 | 398.9 | Qualified |
| Steam pressure | MPa | 4.00 （＋0.2，−0.3） |
3.92 | 3.95 | Qualified |
| Ash ignition loss | % | ≦3.00 | 1.72 | 1.14 | Qualified |
| Retention time of flue gas of 850 °C or higher | s | ≧2.0 | 4.8 | 5.3 | Qualified |
| Lower calorific value of waste | kJ/kg | 6270.0 | 6132 | 6605 | −※ |
※ Excluded from the qualification judgment because the performance of this test item is not guaranteed.
Fig. 11 The waste incineration load for one month
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