CN-118744145-B - Continuous fly ash detoxification method

CN118744145BCN 118744145 BCN118744145 BCN 118744145BCN-118744145-B

Abstract

The invention relates to the field of fly ash disposal, in particular to a continuous fly ash detoxification method, which comprises a water washing system, a membrane filtration system, a hydrothermal system, a dehydration system and an auxiliary system, and can realize the removal of soluble chlorine, the decomposition of dioxin and the stabilization of heavy metals in fly ash. Aiming at the sequencing batch operation mode adopted by the current fly ash washing, the method adopts a large proportion of water-ash ratio to wash the fly ash, utilizes air floatation to separate most of active carbon in the fly ash, utilizes a membrane filtration system to regulate and control the solid-liquid ratio of the washed fly ash, and adopts a hydrothermal system to realize detoxification of dioxin and heavy metals in the fly ash. The invention can be used for treating fly ash produced by incineration of household garbage, medical waste, dangerous waste and other wastes, can treat fly ash with different pollution degrees, and has strong adaptability.

Inventors

LIU ZIXING
SHI GUANGFU
WANG YANMING
ZOU JINLIN
MENG WEIZHONG

Assignees

上海市政工程设计研究总院（集团）有限公司

Dates

Publication Date: 20260508
Application Date: 20240624

Claims (5)

1. A continuous fly ash detoxification method is characterized by comprising a water washing system, a membrane filtering system, a hydrothermal system, a dehydration system and an auxiliary system, wherein the water washing system is connected with the membrane filtering system and is used for dissolving soluble chlorine in fly ash and separating active carbon, the membrane filtering system is used for inputting washed fly ash slurry, the discharge end of the membrane filtering system is connected with the hydrothermal system and is used for controlling the solid-to-liquid ratio of the fly ash slurry, the hydrothermal system is connected with the dehydration system and is used for dehydrating the fly ash, and the auxiliary system is a tail gas treatment system and a waste water treatment system and is respectively used for treating tail gas generated in the operation process of the water washing system and the hydrothermal system and waste water generated in the operation process of the membrane filtering system and the dehydration system; The method comprises the following steps: (1) Mixing fly ash and water in a water washing system according to a proportion, wherein ammonia gas is generated in the mixing process, and the ammonia gas is discharged into a tail gas treatment system for treatment by utilizing a tail gas collecting device collecting port at the top of the water washing system; (2) The aeration system at the bottom of the tank is utilized to realize the full stirring of the fly ash and the water, the active carbon in the fly ash is separated by floatation, floats on the liquid surface in a floating foam form, is separated from the liquid phase by utilizing a floating foam scraper, and the active carbon generated by separation is incinerated outside the device; (3) The fully-retained fly ash slurry in the water washing tank is pumped to a membrane filtration system, the solid-to-liquid ratio of the fly ash slurry at the concentrated water end is controlled by controlling the power of a water inlet pump of the membrane, and the membrane filtration system is provided with at least two sets of fly ash slurry which are alternately used to realize continuous operation and are used for a plurality of times; (4) Pumping the fly ash slurry in the No. 1 cache tank by using a pump, arranging an automatic dosing device after the pump, automatically adding a heavy metal stabilizer into a pipeline, and pumping the heavy metal stabilizer into a hydrothermal reactor by using a high-pressure plunger pump; (5) The hydrothermal reactor adopts a continuous reactor, the electric heating is utilized to control the reaction temperature, and the opening of an outlet valve and a high-pressure plunger pump are utilized to control the reaction pressure, so that the continuous operation of the hydrothermal reaction can be realized; (6) Fully hydrothermally treated fly ash slurry is sent to a No. 2 cache tank from a discharging end of the hydrothermal device, the fly ash slurry is restored to normal pressure in the No. 2 cache tank and is pumped to a dehydration system; (7) And finally dehydrating the fly ash in a dehydration system in the fly ash slurry, wherein the generated dehydrated fly ash is used for recycling.
2. The continuous fly ash detoxification method according to claim 1, wherein the water washing system comprises a water washing tank, an aeration device, a froth scraping plate and a tail gas collecting device; (1) The length of the water washing tank is 5-10 m, the width of the water washing tank is 1-2m, the inlet/outlet is positioned at the short side of the water washing tank, and fly ash, water, a collector and a foaming agent are fed from one side and discharged from the other side; (2) Controlling the water-cement ratio to be 15-30:1, wherein the feeding rate is equal to the discharging rate, and ensuring the liquid level in the water washing tank to be basically constant; (3) The addition ratio of the collecting agent and the foaming agent is 0-15% of the feeding amount of the fly ash.
3. The continuous fly ash detoxification method according to claim 1, wherein the membrane filtration system can adopt an ultrafiltration membrane and a microfiltration membrane, and the method is not less than two sets of the ultrafiltration membranes and the microfiltration membranes are used alternately; and (3) controlling the solid content of the fly ash slurry treated by the membrane filtration system to be within a range of 10-30%.
4. The continuous fly ash detoxification method according to claim 1, wherein the hydrothermal system comprises a feed pump, a # 1 buffer tank, a hydrothermal reactor, a # 2 buffer tank; (1) The adding proportion of the heavy metal stabilizer is 0-50% of the total amount of the fly ash; (2) The heavy metal stabilizer comprises sodium hydrogen phosphate, sodium sulfide, ferric chloride and the like; (3) The hydrothermal reaction temperature is controlled to be 200-400 ℃, and the residence time is controlled to be 0.5-1 h.
5. A continuous fly ash detoxification process according to claim 1, wherein the dewatering system is a vacuum belt filter.

Description

Continuous fly ash detoxification method Technical Field The invention relates to the field of fly ash disposal, which comprises fly ash washing, detoxification and resource utilization, in particular to a continuous fly ash detoxification method. Background The incineration fly ash mainly generates a flue gas treatment system after being incinerated with household garbage, hazardous waste and medical waste. Soluble chlorine, dioxin and heavy metals in fly ash are main problems to be solved in fly ash disposal and recycling. Because of different detoxification modes of pollution factors in the fly ash, the single disposal technology cannot realize the detoxification of the fly ash, and the coupling and series connection of the processes are needed. In the prior art, multistage countercurrent washing is a main flow process for removing soluble chlorine, and is operated in sequence, each stage of washing needs to be matched with a solid-liquid separation device, so that the energy consumption is higher, and the finishing operation efficiency is lower. Hydrothermal has a certain curing effect on heavy metals and a certain decomposition effect on dioxin, but the efficiency is low. However, the hydrothermal reaction requires that the water content of the feed is 10-40%, and the continuous operation of fly ash washing and detoxification can be realized by combining the water washing treatment with the hydrothermal treatment, so that the number of equipment in the fly ash washing process is reduced, the fly ash detoxification process is simplified, and the disposal energy consumption and cost are reduced. In addition, research shows that dioxin in the fly ash is mainly enriched in active carbon in the fly ash, and the detoxification requirement of the dioxin in the fly ash is difficult to meet by adopting hydrothermal treatment. Aiming at the characteristics, a flotation process can be added in the fly ash washing process, so that the flotation separation of the activated carbon is promoted, and the detoxification efficiency of the process to dioxin can be further improved. Based on the above considerations, the invention provides a continuous fly ash detoxification method, which realizes continuous operation of fly ash detoxification treatment through coupling action among processes. Disclosure of Invention The invention aims to provide a continuous fly ash detoxification method, which changes the sequencing batch feeding and discharging mode of the existing fly ash washing. The technical scheme comprises a water washing system, a membrane filtration system, a hydrothermal system, a dehydration system and an auxiliary system. The fly ash washing system adopts a large proportion of water to ash ratio to wash the fly ash, utilizes the solubility of chlorine in the fly ash to realize the rapid dechlorination of the fly ash, adopts an aeration mode to remove fine particle active carbon in the fly ash in the washing stage, and primarily removes dioxin in the fly ash. The solid content of the washed fly ash slurry is regulated and controlled by a membrane filtration system. The fly ash slurry with proper solid content is fed into a hydrothermal system, and under high temperature and high pressure, the deep decomposition of dioxin and the solidification of heavy metals are realized, and the content of residual soluble chlorine in dechlorinated fly ash is further reduced. In order to achieve the above purpose, the present invention provides the following technical solutions: A continuous fly ash detoxification method comprises a water washing system, a membrane filtration system, a hydrothermal system, a dehydration system and an auxiliary system, wherein the water washing system is connected with the membrane filtration system and is used for dissolving soluble chlorine in fly ash and separating active carbon, the membrane filtration system inputs fly ash slurry after water washing, a concentrated water end (a discharge end) is connected with the hydrothermal system and is used for controlling the solid-to-liquid ratio of the fly ash slurry, the hydrothermal system is connected with the dehydration system and is used for dehydrating the fly ash, and the auxiliary system is a tail gas treatment system and a waste water treatment system and is respectively used for treating tail gas generated in the operation process of the water washing system and the hydrothermal system and waste water generated in the operation process of the membrane filtration system and the dehydration system; Further, the method comprises the following steps: (1) Mixing fly ash and water in a water washing system according to a proportion, wherein ammonia gas is generated in the mixing process, and the ammonia gas is discharged into a tail gas treatment system for treatment by utilizing a tail gas collecting device collecting port at the top of the water washing system; (2) The aeration system at the bottom of the tank is utilized to realize the fu