Application Analysis of EDI in Power Generation Enterprises

Through the technical transformation project case of power plant, the operation analysis of EDI and mixed bed is compared, and the technical performance of EDI and the feasibility analysis of promotion in the power industry are analyzed. According to the current situation and existing problems of power plant chemistry, the EDI water production process was adopted to replace the mixed bed, and the ideal effect was achieved.

Analysis Summary

  1. The equipment is 3 sets of 130T circulating fluidized bed boilers, equipped with 2 sets of 25MW steam turbine generator sets. The pressure level of the main equipment is high temperature and high pressure unit, the main steam pressure is 9.8MP, and the temperature is 540℃.
  2. The chemical water treatment process is designed according to the requirements of the unit: deep well water – raw water tank – raw water pump – multi-media filter – security filter – primary reverse osmosis – decarburizer – intermediate water tank – intermediate water pump – Mixed bed.
  3. Requirements for high-pressure boiler make-up water: conductivity <0.2µS/㎝, SiO2<20ppb, hardness ≈0.
  4. Problems existing in the original water production process:
    The original process design is that the reverse osmosis effluent enters the first-stage desalination and then enters the mixed bed, which greatly increases the investment of equipment, and the reverse osmosis effluent directly enters the mixed bed to meet the water quality requirements, so this process is adopted. However, the water production cycle of the mixed bed is greatly shortened. According to the actual operation, the periodic water output is 5000-8000 tons. The resin in the mixed bed always has a process of gradual failure, so its conductivity is always a gradually changing curve. During the water production cycle, the water quality gradually changes from qualified to invalid. There are cases where the judgment is too early or too late, and the water quality fluctuates within a certain range. On the other hand, due to the use of acid-base regeneration, the equipment investment and operating costs are increased, and the discharge of acid-base liquid is inevitably increased, polluting the environment.

Comparison of using EDI instead of mixed bed

According to the problems in operation, we use EDI to replace the mixed bed, which solves the above two problems.

EDI is a continuous operation equipment, and there is no problem of operation cycle. The resistivity of the system effluent reaches 14-15MΩ/㎝ (equivalent to 0.06-0.07µS/㎝) and the water quality is stable. EDI adopts electrical regeneration and water production synchronously, and does not use acid and alkali Regeneration also reduces the cost of this part and the discharge of pollutants. The conductivity of reverse osmosis effluent is 13-15µS/㎝. According to the conventional design scheme, a two-stage reverse osmosis + EDI system should be used. The EDI system we choose breaks through the conventional design and adopts the first-level reverse osmosis + EDI. After nearly half a year of continuous operation, the effect is very good, the cost is reduced, the capital is saved, and after normal operation, there is no need to add medicine, only the concentrated water part of the system is used to maintain the conductivity of the concentration chamber, and the balance of the system can be achieved.

Taking a 50T/H system as an example, the direct operating cost of the mixed bed is 177,000 yuan per year based on the operating time of 6,000 hours. The direct operating cost of EDI is 90,000 yuan. The annual direct cost is reduced by 87,000 yuan (the direct operating cost is 21,000 yuan based on the power cost of the power plant, and the annual direct cost can be reduced by 156,000 yuan). The equipment investment of 50T/H mixed bed (including acid-base storage and transportation, and discharge equipment) and metering equipment, doubling equipment, etc.) is about 800,000 yuan, while the EDI investment of the same water production capacity is 1 million yuan, but the floor area of ​​the mixed bed is 860 square meters, while the EDI is 20 square meters, and the height of the plant requires EDI It is far lower than the mixed bed by more than 10 meters, only 3 meters. It can be seen that although the initial investment of EDI equipment is slightly higher, if the above items are calculated, the EDI investment is smaller than that of the mixed bed.

In Conclusion

The EDI technical renovation project has improved the water quality, and guaranteed or even exceeded the water quality requirements of high-pressure boilers and steam turbines. That reduces the operating cost and prolongs the service life of the equipment. It eliminates the discharge of acid and alkali pollutants and protects the environment. It is a successful technical transformation project.

The use of EDI instead of mixed bed has the following advantages

  1. Stable water quality: The resin in the mixed bed always has a gradual failure process, so its conductivity is always a gradually changing curve. During the water production cycle, the water quality gradually changes from qualified to failure. early or late phenomenon. The exchange and regeneration of EDI water production process are synchronized, and its water quality is very stable.
  2. Continuous operation without regeneration. Ion exchange and regeneration are synchronized to realize continuous production, no need to stop regeneration, and no need for acid-base storage and transportation equipment and metering equipment.
  3. saving acid and alkali, reducing operating costs. The operation of EDI only consumes electricity, and the mixed bed also needs acid and alkali, so the operation cost of EDI is lower.
  4. There is no acid or lye discharge, green and environmental protection, water-saving and energy-saving, and all concentrated water is reasonably reused, and the extreme water discharge rate is controlled within 5%, which is far less than the 10% sewage discharge of ion exchange.
  5. The installation and maintenance of the equipment is simple, no spare equipment is required, and the maintenance and replacement of any membrane block will not affect the operation of other membrane blocks.
  6. The operation is simpler than that of the mixed bed. It only needs to adjust the voltage and current of the rectifier power supply, and it is very easy to realize automatic control.
  7. The water quality is good, and the resistivity of EDI pure water can be as high as 15MΩ.㎝, which can better ensure the safe operation of high-parameter units. Effectively prolong the service life of boilers and steam turbines.
  8. The equipment occupies less area, the height of the workshop is low, the height of the mixed-bed workshop is more than 10 meters, and the height of the EDI workshop is 3 meters, and the area is about 3% of the mixed-bed, and the total investment is 2/2 of the mixed-bed. 3.
  9. The total investment is small. Although the price of EDI equipment itself is high, if the land occupation and plant investment are included, the EDI investment is less than that of the mixed bed.

Therefore, it is said that the use of EDI to replace the mixed bed to achieve a complete green, environmentally friendly and energy-saving make-up water production process will definitely be the inevitable direction of the chemical development of power plants and power plants.

Xi’an CHIWATEC Water Treatment Technology is a high-tech enterprise specialized in various water processing devices. Aside from these individual products, which cover a number of types and series, we can also help with related comprehensive engineering projects. Thanks to our hard work and dedication upon our founding, we are now one of the fastest-developing water treatment equipment manufacturers in Western China.

Further reading:

EDI in Power Generation Enterprises

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