Recycling treatment process for thermal power plant desulfurization wastewater

Abstract

The invention discloses a recycling treatment process for thermal power plant desulfurization wastewater. The process includes: 1) subjecting desulfurization wastewater to triple box treatment, and then letting the treated wastewater enter a pre-sedimentation tank; 2) adding NaOH and letting it overflow into a 1# reaction tank to undergo reaction; 3) letting the effluent water of the 1# reaction tank enter a concentration tank, transporting the feed liquid in the concentration tank into a TMF system for filtering, returning the formed Mg(OH)2 to the concentration tank, and discharging Mg(OH)2 into a 2# reaction tank; 4) letting the TMF system produced water enter a seed crystal tank, outputting the waste liquid to a hydrocyclone, and making the clear liquid obtained by the hydrocyclone enter a nanofiltration system; 5) returning the concentrated liquid obtained by the nanofiltration system to the seed crystal tank, making the dialysate enter a reverse osmosis system, and conducting electric treatment on the obtained concentrated liquid; and 6) subjecting the MgCl2 feed liquid formed in the 2# reaction tank to evaporative crystallization to form MgCl2 crystals, and then conducting re-drying to obtain anhydrous MgCl2, and carrying out electrolytic treatment on the anhydrous MgCl2 to obtain elemental Mg and Cl2. The "chemical reaction+TMF system+seed crystal tank+hydrocyclone+nanofiltration system+reverse osmosis system+bipolar membrane" process involved in the invention can reuse 90% or more of water, and can utilize Mg, CaSO4 and NaCl in wastewater.

Description

technical field [0001] The invention relates to the field of desulfurization wastewater treatment in thermal power plants, in particular to a process for resourceful treatment of desulfurization wastewater in thermal power plants. Background technique [0002] At present, among various desulfurization methods in thermal power plants, boiler flue gas wet desulfurization accounts for an increasing proportion due to its high desulfurization efficiency, but the disadvantage of this process is that waste water is generated, and the pH value of waste water is 5-6 At the same time, it contains a large amount of suspended matter (gypsum particles, SO2, hydroxides of Al and iron), fluorides and heavy metal elements such as As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, Sn, Zn, etc. Domestic power plants mostly adopt wet limestone-gypsum treatment process for desulfurization. The flue gas contains a small amount of F-, Cl- and various impurities brought from the raw coal. After entering the des...

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Problems solved by technology

The above four desulfurization wastewater treatment process routes have their own advantages and disadvantages, but they all have the following problems: 1) The cost of softening and dosing of pretreatment chemicals is high. According to calculations, the cost of softening chemicals per ton of water is about 20-30 yuan / m3; 2) It is difficult to guarantee the purity of the crystallized salt after evaporation. When the purity is low, it can only be treated as solid waste (hazardous waste), which increases the cost of water treatment per ton; 3) The cost of evaporation and crystallization is high, and the steam consumption and power consumption are high. higher

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