CN112661431A

CN112661431A - Method for preparing baking-free brick after washing and desalting fly ash

Info

Publication number: CN112661431A
Application number: CN202011572661.3A
Authority: CN
Inventors: 龙吉生; 张毅扬; 冯淋淋; 劳云枫; 刘露; 胡发立; 白力; 瞿兆舟; 孙中涛; 毛梦梅
Original assignee: Shanghai SUS Environment Co Ltd
Current assignee: Shanghai SUS Environment Co Ltd
Priority date: 2020-12-24
Filing date: 2020-12-24
Publication date: 2021-04-16

Abstract

The invention provides a method for preparing baking-free bricks by washing and desalting fly ash, which comprises the following steps: pulping fly ash; dehydrating fly ash slurry; purifying and desalting water; mixing cement auxiliary materials; and (5) curing and forming. The heavy metals in the fly ash are stabilized by adding a chelating agent and a dioxin adsorbent into fly ash slurry, dioxin is adsorbed, a filter cake is generated after suction filtration and dehydration and is subjected to compatibility mixing with cement auxiliary materials, water is added for stirring, and finally the fly ash and the cement mixed brick is obtained by immersing the fly ash and the dioxin adsorbent into a mold for curing and forming. The medicament stabilizes heavy metal and dioxin in the fly ash, so that the fly ash is not easy to leach out; removing salt in the fly ash after suction filtration and dehydration; the suction filtration wastewater passes through a water quality purification and MVR evaporation working section, a fly ash filter cake is sent into a mixing roll, evaporation condensed water is recycled in a pulping tank, and the crystallized salt is collected for resource utilization; the addition of cement and auxiliary materials further stabilizes heavy metals, can improve the strength of the brick, reduces the environmental risk of fly ash landfill, and can make resource utilization of the product and change the harm into treasure.

Description

Method for preparing baking-free brick after washing and desalting fly ash

Technical Field

The invention relates to a process for making bricks by mixing washed domestic garbage incineration fly ash with cement auxiliary materials, which is used for removing soluble salt in fly ash and capturing dioxin while realizing the stabilization of heavy metal in the domestic garbage incineration fly ash, and is mixed with the cement auxiliary materials to manufacture cement bricks, thereby realizing the resource utilization of the fly ash and reducing the environmental risk.

Background

At present, the treatment of the fly ash generated by burning the household garbage is a great problem in the industry, the yield of the fly ash is about 1.8 ten thousand tons/day at present, the main treatment technologies comprise medicament stabilization, cement solidification, high-temperature heat treatment, cement kiln cooperative treatment and the like, and the mainstream technology of the industry adopts medicament chelation stabilization and landfill treatment. With the 6.3 proposals in the standard of the technical specification HJ1134 for controlling pollution of fly ash incineration fly ash, which aims at controlling pollution of other resource products except the synergy of a cement kiln, namely the limitation on heavy metals, chlorine salts and dioxin in fly ash products, the removal and fixation of 'three hazards' in fly ash become the important part of resource means.

Disclosure of Invention

The invention aims to solve the technical problem of providing a brick making process which has good desalting effect and can realize double stabilization of heavy metal and dioxin, thereby realizing resource utilization.

A process for preparing baking-free bricks after washing and desalting fly ash comprises the following specific operation steps:

(1) fly ash pulping: mixing fly ash and water according to a weight ratio of 1: 3-4, adding the mixture into a closed pulping tank for pulping and stirring, and adding a heavy metal chelating agent and a dioxin adsorbing agent into the pulp to stabilize the heavy metal and the dioxin;

(2) and (3) dewatering fly ash slurry: conveying and flatly paving the fly ash onto filter cloth of a belt type suction filter through a slurry pump, gradually reducing the water content from 70-90% to 20-40% in the conveying process, and conveying a filter cake into a rear-end mixing mill;

(3) water purification and desalination: soluble salt and ash content in the fly ash are contained in the pumping filtration wastewater, the fly ash is treated, evaporation condensate water is recycled to a pulping section, a fly ash filter cake is sent to a mixing roll, and resource utilization is carried out after crystal salt is collected;

(4) mixing cement auxiliary materials: adding cement and auxiliary materials into a mixing roll through a weighing device, adding 10-20% of water, and continuously stirring to fully mix and contact the materials;

(5) curing and forming: pouring the stirred mixture into a mold, placing the mold in a temporary storage room for curing for 7 days, and taking out the mold after molding.

Further, a heavy metal chelating agent and a dioxin adsorbent are added in the pulping process in the step (1), wherein the addition amount of the heavy metal chelating agent is 2-10% of the dry basis weight of the fly ash, and the addition amount of the dioxin adsorbent is 5-20% of the dry basis weight of the fly ash.

Further, the heavy metal chelating agent in the step (1) is one or a combination of more of phosphate, dimethylamine and diethylamine EDTA (ethylene diamine tetraacetic acid) connexon.

Further, a belt suction filter is adopted as a slurry dewatering facility in the step (2), the slurry is paved, compacted and suction-filtered, and the water content of the filtered solid is 20-40%.

Further, the step (3) is divided into two parts of water quality purification and evaporation desalination, and the water quality purification section comprises systems of decalcification, precipitation, sand filtration, fine filtration, PH regulation and the like; the evaporation desalting section adopts an MVR evaporation desalting process, evaporated water is recycled for pulping, and the crystallized salt is collected for resource utilization.

Furthermore, in the mixed material in the step (4), the fly ash accounts for 10-30%, the cement accounts for 20-30%, the auxiliary material accounts for 10-20%, and the process water accounts for 10-20%.

Further, a weighing module is arranged at the bottom of the mixing mill in the step (4), and cement auxiliary materials and process water are added and weighed through corresponding weighing hoppers.

The invention has the following beneficial effects:

1. the fly ash realizes the solidification of heavy metal and the adsorption of dioxin under the action of the chelating agent and the dioxin adsorption agent, and the cement auxiliary material added at the rear end fixes the heavy metal again, so that the environmental risk is reduced.

2. The fly ash is washed by water before the cement auxiliary materials are mixed, so that a large amount of salt in the fly ash is removed, and the compressive strength and the environmental risk coping capability of the fly ash product are improved.

3. The fly ash and the cement auxiliary materials are mixed and weighed, so that the proportioning is accurate and reasonable.

4. The ash washing wastewater is subjected to water treatment and evaporation salt making, the evaporation is recycled, and the secondary salt is collected for recycling treatment

The following further description is made in conjunction with the accompanying drawings and examples.

Drawings

FIG. 1 is a process flow chart of a baking-free brick prepared by washing and desalting fly ash

Detailed Description

As shown in fig. 1, a method for preparing a baking-free brick after washing and desalting fly ash, which fixes or removes heavy metals, dioxin and salt in the fly ash through pretreatment, and then mixes the fixed or removed heavy metals, dioxin and salt with cement auxiliary materials to prepare the baking-free brick, comprises the following steps:

Claims

1. A method for preparing baking-free bricks after washing and desalting fly ash is characterized in that heavy metal, dioxin and salt in the fly ash are fixed or removed through pretreatment, and then the fixed or removed heavy metal, dioxin and salt are mixed with cement auxiliary materials to prepare the baking-free bricks, and the method comprises the following steps:

(3) water purification and desalination: soluble salt and ash content in the fly ash are contained in the pumping filtration wastewater, the evaporated condensate water is recycled to the pulping section, the fly ash filter cake is sent to a mixing roll, and the resource utilization is carried out after the collection of the crystallized salt;

2. The method for preparing baking-free bricks after washing and desalting the fly ash according to claim 1, wherein a heavy metal chelating agent and a dioxin adsorbent are added in the pulping process in the step (1), the addition amount of the heavy metal chelating agent is 2-10% of the dry basis weight of the fly ash, and the addition amount of the dioxin adsorbent is 5-20% of the dry basis weight of the fly ash.

3. The method for preparing baking-free bricks after washing and desalting fly ash according to claim 1, wherein the heavy metal chelating agent in step (1) is one or a combination of phosphate, dimethylamine and diethylamine EDTA (ethylene diamine tetraacetic acid) connexomer.

4. The method for preparing baking-free bricks after washing and desalting fly ash according to claim 1, wherein a belt filter is adopted as a slurry dewatering facility in the step (2) to realize the flattening, compaction and suction filtration of the slurry, and the water content of the solid after the suction filtration is 20-40%.

5. The method for preparing baking-free bricks after washing and desalting fly ash according to claim 1, wherein the step (3) is divided into two parts of water quality purification and evaporation and desalting, and the water quality purification section comprises systems of decalcification, precipitation, sand filtration, fine filtration, pH regulation and the like; the evaporation desalting section adopts an MVR evaporation desalting process, evaporated water is recycled for pulping, and the crystallized salt is collected for resource utilization.

6. The method for preparing baking-free bricks after washing and desalting the fly ash according to claim 1, wherein in the mixed material in the step (4), the fly ash accounts for 10% -30%, the cement accounts for 20% -30%, the auxiliary material accounts for 10% -20%, and the process water accounts for 10-20%.

7. The method for preparing baking-free bricks after washing and desalting fly ash according to claim 1, wherein a weighing module is arranged at the bottom of the mixing mill in the step (4), and cement auxiliary materials and process water are added and weighed through corresponding weighing hoppers.