Method for magnesium oxide method power plant desulfurization wastewater zero discharging treatment

A treatment method and technology for desulfurization wastewater, applied in gaseous discharge wastewater treatment, water/sewage treatment, chemical instrument and method, etc. The effect of processing cost, realizing resource utilization, and reducing usage

Pending Publication Date: 2019-08-09
BEIJING CYCLE COLUMBUS ENVIRONMENTAL SCI & TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

When the above zero-emission projects are in operation, calcium hydroxide + soda ash is used for softening, which will produce a large amount of mixed sludge of magnesium hydroxide and calcium carbonate. The current disposal method is to filter and dewater the above mixed sludge and then landfill it. , due to the high content of Mg and Ca in the wastewater, a large amount of sludge is generated and the treatment cost is high
The salt produced in the evaporation system is mainly composed of sodium chloride and sodium sulfate. The mixed salt has no market to consume and can only be treated as solid waste; the indicators of sodium chloride and sodium sulfate after salt separation are also difficult to meet the market requirements, low product value
[0003] It can be seen that the current zero-discharge process of desulfurization wastewater only solves the problem of wastewater discharge, and a large amount of solid waste generated during the treatment process not only greatly increases the operating cost of the system, but also does not make rational use of resources

Method used

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  • Method for magnesium oxide method power plant desulfurization wastewater zero discharging treatment
  • Method for magnesium oxide method power plant desulfurization wastewater zero discharging treatment
  • Method for magnesium oxide method power plant desulfurization wastewater zero discharging treatment

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0030] The water quality of desulfurization wastewater from a magnesia power plant is shown in Table 1, unit, mg / L

[0031]

[0032] The waste water first enters the primary softening unit, adding sodium hydroxide solution and a large amount of Mg in the water 2+ Formation of Mg(OH) 2 Precipitation, while removing trace amounts of other heavy metal ions in water such as Cu, As, Pb, etc., sodium hydroxide comes from the bipolar membrane electrodialysis unit in the system, in which NaOH and Mg 2+ The molar ratio is 2:1, and the residence time is 20min.

[0033] The first-stage softened mud-water mixture enters the high-density precipitation unit for precipitation, and the obtained Mg(OH) 2 The precipitation slurry is reused for flue gas desulfurization to absorb sulfur dioxide in the flue gas of the power plant. The precipitation time is 3 hours, and the high-density precipitation water Mg 2+ Reduced to below 20mg / L.

[0034] The high-density precipitation supernatant ent...

Embodiment 2

[0042] The water quality of desulfurization wastewater from a magnesia power plant is shown in Table 1, unit, mg / L

[0043]

[0044] The waste water first enters the primary softening unit, adding sodium hydroxide solution and a large amount of Mg in the water 2+ Formation of Mg(OH) 2 Precipitation, while removing trace amounts of other heavy metal ions in water such as Cu, As, Pb, etc., sodium hydroxide comes from the bipolar membrane electrodialysis unit in the system, in which NaOH and Mg 2+ The molar ratio is 2.5:1, and the residence time is 30min.

[0045] The first-stage softened mud-water mixture enters the high-density precipitation unit for precipitation, and the obtained Mg(OH) 2 The precipitation slurry is reused for flue gas desulfurization to absorb sulfur dioxide in the flue gas of the power plant. The precipitation time is 4 hours, and the high-density precipitation water Mg 2+ Reduced to below 20mg / L.

[0046] The high-density precipitation supernatant e...

Embodiment 3

[0054] The water quality of desulfurization wastewater from a magnesia power plant is shown in Table 1, unit, mg / L

[0055]

[0056] The waste water first enters the primary softening unit, adding sodium hydroxide solution and a large amount of Mg in the water 2+ Formation of Mg(OH) 2 Precipitation, while removing trace amounts of other heavy metal ions in water such as Cu, As, Pb, etc., sodium hydroxide comes from the bipolar membrane electrodialysis unit in the system, in which NaOH and Mg 2+ The molar ratio is 3:1, and the residence time is 30min.

[0057] The first-stage softened mud-water mixture enters the high-density precipitation unit for precipitation, and the obtained Mg(OH) 2 The precipitation slurry is reused for flue gas desulfurization to absorb sulfur dioxide in the flue gas of the power plant. The precipitation time is 4 hours, and the high-density precipitation water Mg 2+ Reduced to below 20mg / L.

[0058] The high-density precipitation supernatant ent...

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Abstract

The invention discloses a method for magnesium oxide method power plant desulfurization wastewater zero discharging treatment. The method comprises the steps that wastewater is subjected to primary softening to remove Mg2+ and heavy metal ions, a primarily softened mud and water mixture enters a first high density precipitation unit, an obtained supernate enters a secondary softening unit to remove Ca2+, a secondarily softened mud and water mixture enters a second high density precipitation unit for precipitation, a supernate is treated through a film system, obtained fresh water is recycled,produced concentrated water enters a chelation resin unit, calcium, magnesium and heavy metal ions are removed deep, outflow water enters a bi-polar membrane electrodialysis unit, and a sodium hydroxide solution with the concentration being 10% and a hydrochloric acid with the concentration being 8% are obtained through treatment; the method achieves recycling of magnesium hydroxide slurry, the consumption of flue gas desulfurization magnesium oxide is greatly lowered, the bi-polar membrane electrodialysis acid-alkali producing technology is adopted, meanwhile, carbon dioxide in flue gas of apower plant is used for preparing sodium carbonate, recycling of salt in wastewater is achieved, and no softening medicament needs to be purchased additionally.

Description

technical field [0001] The invention belongs to the field of advanced wastewater treatment, and in particular relates to a zero-discharge treatment method for desulfurization wastewater in a magnesium oxide power plant. Background technique [0002] Desulfurization wastewater produced by magnesium oxide desulfurization in thermal power plants contains mainly Cl - , SO4 2- 、Na + , Mg 2+ , Ca 2+ , especially Mg 2+ The content is relatively high, which is a typical high-salt and high-hardness wastewater. At present, most domestic and foreign coal-fired power plant desulfurization wastewater zero discharge projects adopt the "softening + membrane concentration + evaporation crystallization" process route. When the above zero-emission projects are in operation, calcium hydroxide + soda ash is used for softening, which will produce a large amount of mixed sludge of magnesium hydroxide and calcium carbonate. The current disposal method is to filter and dewater the above mixed...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C02F9/06B01D53/96C01D7/07C01D1/04C01B7/01
CPCB01D53/96C01B7/01C01D1/04C01D7/07C02F1/441C02F1/442C02F1/444C02F1/4693C02F1/62C02F1/66C02F5/00C02F5/02C02F5/06C02F9/00C02F2001/007C02F2103/18
Inventor 李海波王靖宇盛宇星李玉平
Owner BEIJING CYCLE COLUMBUS ENVIRONMENTAL SCI & TECH
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