Chengdu GreenWater Co.,LtdHome
Library
Technical Literature
Coking wastewater treatment aeration system - ejector operation report
Coking wastewater treatment aeration system - ejector operation report
Qian'an Sinochem Coal Chemical Co., Ltd.
The coking wastewater treatment of the coking plant of Qian'an Sinochem Coal Chemical Co., Ltd. uses biochemical treatment. The biochemical treatment system is divided into two groups and operates in parallel. Each group of biochemical aeration system has two levels of aeration, which are divided into O1 aeration tank and O2 aeration tank. The current aeration system uses a blast microporous aeration method. As time goes by, the microporous aeration pipes become clogged, aged and cracked, the oxygen utilization rate decreases, and the ability to withstand impact loads is weak. As a result, the dissolved oxygen and effluent quality in the aeration tank do not meet the design goals, and the water needs to be regularly shut down and drained for maintenance.
In response to the above situation, Qian'an Sinochem Coal Chemical Co., Ltd. signed a technical agreement with Chengdu Green Water Technology Co., Ltd. and purchased a set of 3600 ejector from Chengdu Green Water Technology Co., Ltd. with 24 N40 efficiency nozzles for renovation in the first corridor of the West O1 aeration tank.
1. Analysis of water treatment effect before jet aeration modification
(1) Treatment water quantity and quality
| Date (month/day) | Total treated water volume (m³/h) | Adjustment pool effluent COD (mg/L) | O1 aeration tank effluent COD (mg/L) | O2 aeration tank effluent COD (mg/L) |
|---|---|---|---|---|
| 4/14 | 110 | 4450 | 1040 | 405.4 |
| 4/15 | 110 | 4269 | 1033 | 405.4 |
| 4/16 | 110 | 3845 | 1278 | 490 |
| 4/17 | 110 | 5580 | 1910 | 725 |
| 4/18 | 110 | 4504 | 1049 | 433.3 |
| 4/19 | 110 | 5426 | 983 | 433.3 |
| 4/20 | 110 | 4803 | 971.7 | 400 |
| 4/21 | 110 | 4665 | 1046 | 565 |
| 4/22 | 110 | 4192 | 933 | 485.8 |
| 4/23 | 110 | 4775 | 985.9 | 599.5 |
| 4/24 | 110 | 4205 | 892 | 624.5 |
| 4/25 | 110 | 4971 | 949.5 | 656.1 |
| 4/26 | 110 | 4464 | 974.5 | 594.6 |
| 5/1 | 110 | 5689 | 907.2 | 589.7 |
| 5/2 | 110 | 4346 | 941.4 | 596.2 |
| 5/3 | 110 | 4914 | 933.4 | 561.1 |
| 5/4 | 110 | 5232 | 915 | 474.7 |
| Average treated water volume, water quality | 110 | 4725.3 | 1043.7 | 531.7 |
(2) Effective volume of the pool
| unit | Single corridor size (m) | Total effective volume of single group (m³) | Remark |
|---|---|---|---|
| O1 aeration tank | 35 × 4.5 × 5.5 | 2363 | 3 corridors in each group, 6 corridors in total |
| O2 aeration tank | 35 × 4.5 × 5.5 | 788 | 1 corridor per group, 2 corridors in total |
(3) Process operating parameters
MLVSS: 3500 mg/L; dissolved oxygen concentration: 2 mg/L; design water temperature: 30 ℃.
(4) Oxygen demand calculation
| unit | Treatment water volume (m³/h) | Actual oxygen demand (kg(O₂)/h) |
|---|---|---|
| O1 aeration tank | 110 | 282 |
| O2 aeration tank | 110 | 41 |
Total actual oxygen demand: 282 + 41 = 323 kg(O₂)/h.
(5) Analysis of oxygen supply and oxygen utilization rate of existing blowers
The existing fan air volume: 50 m³/min, wind pressure 63 kPa, installed power 75 kW, a total of 4 units, four units are fully open.
Total air volume: 50 × 60 × 4 = 12000 m³/h.
Oxygen supply: 12000 × 0.21 × 1.4 = 3528 kg(O₂)/h.
The oxygen utilization rate of the aeration equipment of the existing aeration system is: 323 ÷ 3528 ≈ 9.15%.
(6) Analysis of existing power consumption and nameplate power efficiency
When the total water treatment volume is 110 m³/h, 4 fans are turned on.
| category | Installed power (kW) | quantity | Total installed power (kW) | Actual nameplate power efficiency (kg(O₂)/kWh) |
|---|---|---|---|---|
| Blower | 75 | 4 | 300 | 323 ÷ 300 = 1.08 |
2. Analysis of the water treatment effect after only the first corridor of the West O1 Pool was changed to jet aeration
(1) Treatment water quantity and quality
| Date (month/day) | Total treated water volume (m³/h) | Adjustment pool effluent COD (mg/L) | O1 aeration tank effluent COD (mg/L) | O2 aeration tank effluent COD (mg/L) |
|---|---|---|---|---|
| 5/5 | 110 | 5232 | 838.9 | 554.9 |
| 5/6 | 110 | 5014 | 816.4 | 499 |
| 5/7 | 110 | 3244 | 725.5 | 332.2 |
| 5/8 | 110 | 3277 | 679.9 | 304 |
| 5/9 | 110 | 3367 | 727.5 | 325.5 |
| 5/10 | 110 | 4517 | 617.9 | 399.2 |
| Average treated water volume, water quality | 110 | 4108.5 | 734.4 | 402.5 |
(2) Oxygen demand calculation
| unit | Treatment water volume (m³/h) | Actual oxygen demand (kg(O₂)/h) |
|---|---|---|
| O1 aeration tank | 110 | 265 |
| O2 aeration tank | 110 | 29 |
Total actual oxygen demand: 265 + 29 = 294 kg(O₂)/h.
(3) Analysis of oxygenation amount and oxygen utilization rate of ejector
The ejector adopts the air blowing and pressurizing operation mode. Under the design conditions of the existing blower wind pressure of 63 kPa, the air suction volume of the ejector is 815 m³/h. According to on-site operation tests, there are currently three fans in operation, three in operation and one in standby.
Total blast volume: 50 × 60 × 3 = 9000 m³/h; of which the ejector uses 815 m³/h and the existing aeration equipment uses 9000 − 815 = 8185 m³/h.
Based on the oxygen utilization rate of the existing blast aeration equipment of 9.15%, the actual oxygenation amount is 8185 × 0.21 × 1.4 × 9.15% = 220.2 kg(O₂)/h.
Actual oxygenation amount of jet aeration: 294 − 220.2 = 73.8 kg(O₂)/h.
Oxygen utilization rate of jet aeration equipment: 73.8 ÷ (815 × 0.21 × 1.4) ≈ 30.8%.
(4) Analysis of dissolved oxygen before and after the renovation of the first corridor
| serial number | Measure dissolved oxygen position | value before renovation | Technical requirements | actual operating value |
|---|---|---|---|---|
| 1 | 1/4 of the water inlet end of the first corridor of West O1 | 0.15～0.5 | 1～1.5 | 1.3～2 |
| 2 | 1/2 of the 1st corridor of West O1 | 0.2～0.7 | — | 1.8～5 |
| 3 | 1/2 of the outlet end of the first corridor of West O1 | 0.5～1.5 | — | 1.3～4.5 |
(5) Analysis of power consumption of the entire aeration system and nameplate power efficiency
After only the first corridor of the West O1 pool was changed to jet aeration, when the total treated water volume was 110 m³/h, 3 fans were turned on.
| category | Installed power (kW) | quantity | Total installed power (kW) | Actual nameplate power efficiency (kg(O₂)/kWh) |
|---|---|---|---|---|
| Blower | 75 | 3 | 75 × 3 − 20.4 = 204.6 | 220.2 ÷ 204.6 = 1.08 |
| ejector (fan) | 815 ÷ 3000 × 75 = 20.4 | 1 | 50.4 (total of fans and water pumps) | 73.8 ÷ 50.4 = 1.46 |
| ejector (water pump) | 30 | 1 | — | — |
Total installed power of the system: 225 + 30 = 255 kW.
3. Conclusion
From the monitoring data processing and analysis results before and after the transformation of the jet, as well as the analysis of energy consumption and actual nameplate power efficiency, it can be seen that jet aeration has the following advantages:
- The power efficiency of the entire aeration system is increased, energy consumption is reduced, and the total installed power is reduced from 300 kW to 255 kW.
- The oxygen utilization rate of jet aeration equipment is 30.8%, and the oxygen utilization rate of existing blast aeration equipment is 9.15%. The former is 3.4 times that of the latter.
- The dissolved oxygen in the aeration tank was increased from 0.15 to 1.5 mg/L before the transformation to 1.3 to 5 mg/L.
- The comprehensive actual nameplate power efficiency of jet aeration is 1.46 kg(O₂)/kWh, which is 0.38 kg(O₂)/kWh higher than the 1.08 kg(O₂)/kWh of the existing blast aeration system, which is 1.35 times the power efficiency of the existing blast aeration equipment. Using the jet aeration method, the total installed power can be reduced by 15%, from 300 kW to 255 kW.
