Abstract
In order to realize zero discharge of desulfurization wastewater, spray drying technology of desulfurization wastewater was used in 2x330MW unit of a power plant. Its principle was to use a rotary atomizer for atomization,and a part of hot flue gas was drawn from the SCR denitrification reactor and air preheater into the drying tower, the heat was used to evaporate the desulfurization wastewater in a spray drying tower. The salt in the waste water was mixed with the dust, which was collected and removed by the electric dust remover. Then the water vapor was mixed with the flue gas and finally enters the desulfurization tower.The field test was carried out under the condition that the unit load was 100% and the amount of desulfurization wastewater treated was 5.1m3/h.The results showed that the hot smoke gas volume of drying tower was about 64896m3/h, The smoke temperature at the inlet and outlet of the drying tower were 335℃ and 205℃ respectively,the moisture content of drying products was only 0.05%. The content of HCl in the flue gas at the inlet and outlet of the drying tower were 55mg/L and 195mg/L respectively, the mass fractions of Cl removal and Cl volatilization in desulfurization wastewater were 87.7% and 12.3% respectively. The increase of Cl content in the dried products had little effect on the utilization of fly ash.
Highlights
At present, the research and application of zeroemission desulphurization wastewater technology was in its infancy
At the end of solidification technology mainly include evaporation pond, evaporation crystallization technology and flue gas evaporation drying technology[13,14,15,16,17,18], which was divided into multiple effect evaporation and crystallization technology evaporation crystallization process (MED) and steam compression (MVR/TVR) evaporation crystallization process, dry flue gas evaporation technology was the main flue gas evaporation drying technology and the bypass flue gas evaporation drying technology, which was divided into two-fluid atomization technology, mechanical rotary atomizing technology, fluidized bed drying technology and so on
Combined with figure 2, it could be judged that the amount of hot smoke was relatively large, resulting in higher smoke temperature at the outlet of the drying tower, which had a certain impact on the boiler efficiency
Summary
Limestone-gypsum wet desulfurization process was the most widely used SO2 removal technology in thermal power industry, it account for about 90% of the capacity of the units that have adopted desulfurization process. The mainstream technology route of these zero-emission desulphurization wastewater projects was "pretreatment + concentration reduction + terminal solidification" [2,3,4,5]. If the amount of desulfurization wastewater was large, pretreatment +concentration reduction could be carried out before solidification treatment. Chemical softening + filtration was generally adopted in pretreatment technology, among which chemical softening mainly includes lime-sodium carbonate softening, lime-flue gas softening, naoh-sodium carbonate softening, etc. At the end of solidification technology mainly include evaporation pond, evaporation crystallization technology and flue gas evaporation drying technology[13,14,15,16,17,18], which was divided into multiple effect evaporation and crystallization technology evaporation crystallization process (MED) and steam compression (MVR/TVR) evaporation crystallization process, dry flue gas evaporation technology was the main flue gas evaporation drying technology and the bypass flue gas evaporation drying technology, which was divided into two-fluid atomization technology, mechanical rotary atomizing technology, fluidized bed drying technology and so on
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