Environmental protection kiln desulfurization and denitrification: dual alkali desulfurization

1、 Overview of Double Alkali Method:

The dual alkali flue gas desulfurization technology uses sodium hydroxide solution as the starting desulfurization agent, and the prepared sodium hydroxide solution is directly injected into the desulfurization tower to wash and remove SO2 from the flue gas to achieve the purpose of flue gas desulfurization. Then, the desulfurization product is reduced to sodium hydroxide through the desulfurization agent regeneration tank and returned to the desulfurization tower for recycling. The dual alkali method uses sodium based desulfurizers for desulfurization inside the tower. Due to the strong alkalinity of sodium based desulfurizers, the solubility of the reaction products after absorbing sulfur dioxide is high, which will not cause supersaturated crystallization and cause scaling and blockage problems. On the other hand, the desulfurization products are discharged into the regeneration tank for reduction and regeneration with calcium hydroxide, and the regenerated sodium based desulfurization agent is then sent back to the desulfurization tower for recycling. The dual alkali desulfurization process reduces investment and operating costs, making it more suitable for desulfurization transformation of small and medium-sized boilers. For more details, please call (WeChat synchronization): 15713691937.

（2） The principle of dual alkali desulfurization:

The dual alkali flue gas desulfurization process has a similar mechanism to other wet desulfurization reactions such as limestone/lime. The main reaction is that SO2 in the flue gas is first dissolved in the absorption liquid, and then dissociated into H+and HSO3-; Use Na2CO3 or NaOH solution to absorb SO2 from flue gas, generating HSO32-, SO32-, and SO42-. The reaction equation is as follows:

Desulfurization reaction:

Na2CO3 + SO2 → Na2SO3 + CO2↑                       （1）

2NaOH + SO2 → Na2SO3 + H2O                          （2）

Na2SO3+ SO2 + H2O → 2NaHSO3                        （3）

Catalytic process:

Na2SO3 + 1/2O2 → Na2SO4                               （4）

NaHSO3 + 1/2O2 → NaHSO4                              （5）

Regeneration process:

Ca(OH)2 + Na2SO3 → 2 NaOH + CaSO3                   （6）

Ca(OH)2 + 2NaHSO3 → Na2SO3 + CaSO3.1/2H2O +3/2H2O   （7）

（3） Composition of dual alkali desulfurization method:

The desulfurization process mainly includes five parts:

(1) Preparation and supplementation of absorbents;

(2) Absorbent slurry spray;

(3) Contact and mixing of fog droplets and smoke inside the tower;

(4) Reduction of sodium based alkali by regeneration pool slurry;

(5) Gypsum dehydration treatment.

（4） Advantages of dual alkali desulfurization process

1. The desulfurization efficiency is above 90%.

2. The desulfurizer uses sodium alkali and lime, and the clear liquid inside the tower is absorbed, effectively avoiding scaling inside the tower.

3. The liquid to gas ratio is small. Integrated desulfurization and dust removal.

4. Low investment, low operating costs, and high degree of domestic production.

5. Wide range of adaptation.

Zhongwei Environmental Protection Group Co., Ltd. (Zhengzhou Zhongwei Environmental Protection Equipment Co., Ltd. and Zhengzhou Deste Automation Equipment Co., Ltd.) undertakes the "general contracting" project of large-scale gas and oil fired kilns, automation control systems, desulfurization and denitrification equipment, kiln refractory material masonry, and online monitoring devices both domestically and internationally. It is a "one-stop" environmental protection kiln solution provider and implementer.

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