CN112536156A - Method for treating heavy metal in fly ash - Google Patents

Abstract

The invention provides a method for treating heavy metals in fly ash, which comprises the following steps: step 1, preparing ore pulp after washing the garbage fly ash, placing the ore pulp in a flotation tank body of a single-tank flotation machine, opening a stirring component, and rotating at a rotating speed: stirring at 1550r/min for 30min to uniformly disperse the ore pulp; step 2, adding inhibitor and dispersant agent combination: (Na2PO3)6(45g/L) + Na2SiO3(45g/L) is continuously stirred for 5min, so that the dispersant and the inhibitor are uniformly mixed with the fly ash pulp, the modified waste surfactant (1 vol.%) is added for activation, and the stirring is continuously carried out for 5 min; step 3, adding a collecting agent dodecylamine (1 wt.%), continuing stirring for 5min, and then closing the stirring assembly; step 4, opening the inflation assembly to inflate, opening the scraper assembly after a large amount of foam is generated in the flotation tank, and scraping the upper-layer flotation foam; and 5, closing the instrument after continuous flotation for 30 min.

Description

Method for treating heavy metal in fly ash

Technical Field

The invention relates to the technical field of mineral processing industry, in particular to a method for treating heavy metal in fly ash.

Background

In the prior art, the common garbage incineration fly ash harmless treatment technology is generally in the following ways: 1. the addition of cement, or other stabilizers, to stabilize the solidified heavy metals has the disadvantage of adding new chemicals, making the fly ash bulky and not conducive to landfill. 2. Heating and melting at high temperature, solidifying the heavy metal in a molten glass-state crystal lattice, and decomposing dioxin due to pyrolysis; the disadvantages of this method are high treatment costs and high energy consumption. 3. The fly ash harmless treatment technology based on heavy metal separation comprises technologies of water washing, acid washing, alkali washing, metal chelating agent collecting and the like. But the method cannot treat harmful substances such as dioxin and needs further treatment; in addition, the secondary water pollution problem after water washing needs additional treatment.

Disclosure of Invention

In view of the above problems, the present invention aims to provide a method for treating heavy metals in fly ash based on flotation technology. The technical scheme is as follows.

A method for treating heavy metals in fly ash comprises the following steps:

step 1, preparing ore pulp after washing the garbage fly ash, placing the ore pulp in a flotation tank body of a single-tank flotation machine, opening a stirring component, and rotating at a rotating speed: stirring at 1550r/min for 30min to uniformly disperse the ore pulp;

step 2, adding an inhibitor and dispersant agent combination, continuing stirring for 5min to uniformly mix the dispersant with the fly ash ore pulp, adding a modified waste surfactant (1 vol.%) for activation, and continuing stirring for 5min, wherein the component ratio of the inhibitor (Na2PO3)6 to the dispersant Na2SiO3 is 1: 1-1: 1.5, and the mixed concentration is 15 g/L-45 g/L; (ii) a

Step 3, adding a collecting agent dodecylamine (1 wt.%), continuing stirring for 5min, and then closing the stirring assembly;

step 4, opening the inflation assembly to inflate, opening the scraper assembly after a large amount of foam is generated in the flotation tank, and scraping the upper-layer flotation foam;

and 5, closing the instrument after continuous flotation for 30 min.

The invention has the beneficial effects that: the method can safely treat the fly ash of the dangerous waste, can recover heavy metal substances in the fly ash, can remove dioxin substances in the recovery process, solves the problem of waste pollution of the surfactant, and achieves multiple purposes. Has considerable economic utilization value and environmental protection significance.

Drawings

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The waste fly ash (after washing) of the invention, the dispersant: (Na2PO3)6(45g/L, aq), inhibitor: na2SiO3(45g/L, aq), activator: modified treated waste surfactant (1 vol.%), collector: dodecylamine (1 wt.%). The flotation machine comprises: single-tank flotation machines (Wuhan exploration machinery plant, XFD-1 type). The flotation machine mainly comprises a stirring component for stirring, an aeration component for aerating to generate gas flotation, and a scraper component for collecting a layer rich in target mineral foam.

The first embodiment is as follows:

the treatment method comprises the following steps: washing garbage flying ash, preparing ore pulp (solid content: about 40%), placing the ore pulp into a flotation tank body of a single-tank flotation machine, opening a stirring component (rotating speed: 1550r/min), stirring for 30min to uniformly disperse the ore pulp, and adding an inhibitor and dispersant agent combination: (Na2PO3)6(45g/L) + Na2SiO3(45g/L) is continuously stirred for 5min to enable a dispersing agent and an inhibitor to be uniformly mixed with fly ash pulp, then a modified waste surfactant (1 vol.%) is added for activation, a collecting agent dodecylamine (1 wt.%) is added after continuous stirring for 5min, a stirring assembly is closed after continuous stirring for 5min, an aeration assembly is opened for aeration (gas flow: 60-100L/h), and after a large amount of foam is generated in a flotation tank, a scraper assembly is opened to scrape upper flotation foam. The instrument was turned off after 30min of continuous flotation. The flotation process is finished. And filtering the tailing slurry in the tank, separating the tailing slurry into tailings (solid) and filtrate, and detecting the heavy metal content of the residual solid and whether the heavy metal content in the flotation froth concentrate reaches the standard or not.

The main components of the surfactant are as follows: an ethoxylated alkylphenol; ethoxylated ethylene glycol; ethoxylated methanol; ethoxylated fatty amines; and B, the waste liquid mixed with the propoxylated fatty alcohol surfactant is modified by Na2CO3 to generate viscous oily liquid. It has a potential as a flotation reaction activator in theory because it mainly contains functional groups common to flotation activators such as a carboxyl group (-COOH), an amine group (-NH2), an unsaturated carbon chain (-C ═ C-), and a hydroxyl group (-OH).

Dioxin-like chemical substances belong to organic matters, so that the dioxin-like chemical substances are easy to enrich, and an activator and a collector can be known according to the principle of chemical similarity and compatibility.

Experiments and related documents show that Pb, Zn, Cu and Cd contained in fly ash in a waste incineration plant in Shenzhen region are substances with over-standard toxicity or extremely high concentration content. According to the experimental results, the method comprises the following steps: aiming at the four elements, Pb, Zn and Cu, the Pb, Zn and Cu are combined with the waste surfactant mainly through physical adsorption and are collected by the collecting agent, and the Cd element is mainly removed through being subjected to repeated selection through forming a Cd-N chemical structure through being complexed with a N-containing group in the waste surfactant. The specific possible equation is as follows:

forming [ Cd (NH3)6]2+ substances which are combined with long-chain carbon in the surfactant and then removed by the collector.

Oxygen-containing functional groups (such as-COOH) in the waste surfactant react with Cd element to form Cd-O bonds, then the Cd-O bonds are bonded by long carbon chains of the surfactant, and finally the Cd-O bonds are collected by the collector:

or forming Cd (OH)2 precipitate in the presence of OH-ions in the solvent.

Cd²⁺+2H₂O＝Cd(OH)₂+2H⁺，log K＝-20.35(298K)。

In the actual continuous production flow, the tailings can be directly buried after reaching the standard, the concentrate can be sent to a pyrometallurgical plant for smelting after reaching the standard, and because dioxin is enriched in organic matters, dioxin-like substances can also be enriched in the concentrate along with flotation foam in the flotation process, and the dioxin-like substances in the garbage fly ash can be removed in the metal recovery process by adopting a pyrometallurgical method. The residual filtrate can be recycled in the system. The method can safely treat the dangerous waste fly ash, can recover heavy metal substances in the fly ash, can remove dioxin substances in the recovery process, solves the problem of waste pollution of a certain surfactant, and achieves multiple purposes. Has considerable economic utilization value and environmental protection significance.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (1)

1. A method for treating heavy metals in fly ash is characterized by comprising the following steps:

step 1, preparing ore pulp after washing the garbage fly ash, placing the ore pulp in a flotation tank body of a single-tank flotation machine, opening a stirring component, and rotating at a rotating speed: stirring at 1550r/min for 30min to uniformly disperse the ore pulp;

step 2, adding an inhibitor and dispersant agent combination, continuing stirring for 5min to uniformly mix the dispersant, the inhibitor and the fly ash pulp, adding a modified waste surfactant (1 vol.%) for activation, and continuing stirring for 5min, wherein the component ratio of the inhibitor (Na2PO3)6 to the dispersant Na2SiO3 is 1: 1-1: 1.5, the concentration after mixing is between 15g/L and 45 g/L;

step 3, adding a collecting agent dodecylamine (1 wt.%), continuing stirring for 5min, and then closing the stirring assembly;

step 4, opening the inflation assembly to inflate, opening the scraper assembly after a large amount of foam is generated in the flotation tank, and scraping the upper-layer flotation foam;

and 5, closing the instrument after continuous flotation for 30 min.

Images