阅读说明：本技术 一种微波辅助化学链气化的土壤重金属修复植物热处理方法 (Microwave-assisted chemical-looping gasification soil heavy metal restoration plant heat treatment method ) 是由 何腾飞 张波 吴石亮 于 2020-04-28 设计创作，主要内容包括：本发明公开了一种微波辅助化学链气化的土壤重金属修复植物热处理方法,具体为,将石英反应器放入微波室中,采用具有微波吸收性能及重金属吸附能力的载氧体,利用载氧体提供的晶格氧,实现修复植物的气化重整反应,获得高质量可燃合成气,同时实现部分重金属在载氧体以及残渣中的固化；使合成气流经活性炭固定床,实现对合成气中重金属的吸附脱除。本发明将微波加热应用于修复植物的化学链气化反应,并将碳化硅作为微波吸收剂,对修复植物加热均匀、升温迅速并节约能量；同时实现载氧体的解放,使其只负责供氧,不再负责传热。本发明通过对修复植物中重金属的高效捕集,获得高品质的合成气,实现土壤重金属修复植物的无害化、资源化利用。(The invention discloses a microwave-assisted chemical-looping gasification soil heavy metal restoration plant heat treatment method, which comprises the following steps of putting a quartz reactor into a microwave chamber, adopting an oxygen carrier with microwave absorption performance and heavy metal adsorption capacity, realizing gasification reforming reaction of restoration plants by using lattice oxygen provided by the oxygen carrier, obtaining high-quality combustible synthesis gas, and simultaneously realizing solidification of partial heavy metals in the oxygen carrier and residues; the synthesis gas flows through the activated carbon fixed bed to realize the adsorption and removal of heavy metals in the synthesis gas. The invention applies microwave heating to chemical chain gasification reaction of the restoration plants, and uses silicon carbide as a microwave absorbent to heat the restoration plants uniformly, heat up rapidly and save energy; meanwhile, the oxygen carrier is liberated, so that the oxygen carrier is only responsible for oxygen supply and is not responsible for heat transfer any more. According to the invention, high-quality synthesis gas is obtained by efficiently trapping heavy metals in the remediation plants, and harmless and resource utilization of the soil heavy metal remediation plants is realized.)

1. A microwave-assisted chemical-looping gasification soil heavy metal restoration plant heat treatment method is characterized by comprising the following steps:

s1, placing the quartz reactor (8) filled with the microwave absorbent fixed bed (9) into a microwave chamber (6) for microwave heating, connecting the quartz reactor (8) with a fuel and oxygen carrier inlet (5), a reaction product outlet (10) and a deionized water inlet (18) through pipelines respectively, and starting a vacuum pump (16) to keep a negative-pressure inert reaction environment in the reactor;

s2, feeding the deionized water (1) into a quartz reactor (8) by using a peristaltic pump (2), and converting the deionized water into water vapor serving as a gasifying agent in the reactor;

s3, feeding a mixture (4) consisting of the repair plants and the oxygen carrier into a quartz reactor (8) by using a feeder (3), carrying out gasification reaction with a gasifying agent to prepare combustible synthetic gas, converting the oxygen carrier into a low-valent oxide, fixing heavy metal parts in the repair plants in carbon residue and the oxygen carrier, and transferring the other parts into the synthetic gas;

s4, enabling the synthesis gas to flow through a heavy metal adsorbent fixed bed (17), and adsorbing and removing heavy metals in the synthesis gas by utilizing the contact between the synthesis gas and the heavy metal adsorbent to complete the capture of the heavy metals contained in the restoration plants to obtain combustible synthesis gas.

2. The microwave-assisted chemical looping gasification soil heavy metal restoration plant heat treatment method according to claim 1, characterized in that: in step S4, fly ash and tar, which are reaction products, are collected by a glass fiber filter (12) and a condenser (13), respectively.

3. The microwave-assisted chemical looping gasification soil heavy metal restoration plant heat treatment method according to claim 1, characterized in that: the microwave absorbent is silicon carbide particles.

4. The microwave-assisted chemical looping gasification soil heavy metal restoration plant heat treatment method according to claim 3, characterized in that: the diameter of the silicon carbide particles is 0.3-0.45 mm.

5. The microwave-assisted chemical looping gasification soil heavy metal restoration plant heat treatment method according to claim 1, characterized in that: the quartz reactor (8) in the step S1 has three interfaces, which are a deionized water inlet (18), a fuel and oxygen carrier inlet (5), and a reaction product outlet (10).

6. The microwave-assisted chemical looping gasification soil heavy metal restoration plant heat treatment method according to claim 1, characterized in that: the reaction temperature in the step S3 is 700-900 ℃.

7. The microwave-assisted chemical looping gasification soil heavy metal restoration plant heat treatment method according to claim 1, characterized in that: in the step S3, the molar ratio O/C of the oxygen carrier to the repair plant is 0.5-2.0.

8. The microwave-assisted chemical looping gasification soil heavy metal restoration plant heat treatment method according to claim 1, characterized in that: the oxygen carrier is hematite.

9. The microwave-assisted chemical looping gasification soil heavy metal remediation phytothermal treatment method of any one of claims 1-8, characterized in that: the heavy metal adsorbent fixed bed (17) in the step S4 is a fixed bed with activated carbon arranged inside, and the mass ratio of the activated carbon to the restoration plants in the step S3 is 0.04-0.08.

Technical Field

The invention relates to a heat treatment method of heavy metal restoration plants in the field of energy and environmental protection, in particular to a heat treatment method of soil heavy metal restoration plants by microwave-assisted chemical chain gasification.

Background

Phytoremediation, as a new technology for eliminating heavy metals in contaminated soil, is rapidly developed in the field of heavy metal treatment. But with the large-area popularization and application of the plant repairing technology, the problem of post-partum treatment of the repaired plant is generated. If the treatment is improper, the heavy metals enriched in the restoration plants can be returned to the environment again, so that not only can secondary pollution be caused to the environment, but also the waste of manpower, material resources and financial resources can be caused.

Traditional methods for treating the soil heavy metal restoration plants after delivery comprise a compression landfill method, an incineration method, a composting method, a pyrolysis method and the like. The technologies develop for years, the technical route is mature, but all the technologies have some problems which cannot be ignored. For example, the compression landfill method needs low cost, but needs to occupy a large amount of land resources and causes secondary pollution to the surrounding environment; although the burning method has high decrement degree, the investment and operation cost is high, and the problem of smoke pollution exists; the composting method can change the repaired plants into valuable things, but has longer treatment period and the risk of secondary pollution; the pyrolysis treatment of the repaired plant can produce combustible syngas or bio-oil, but the quality of the product needs to be further improved.

As a new gasification technology, the chemical looping gasification changes the traditional one-step gasification process in one reactor into two-step process in two independent reactors, namely, a fuel reactor and an air reactor are carried out step by step, and a proper oxide is selected as an oxygen carrier to be alternately circulated between the two reactors. In the fuel reactor, the oxygen carrier provides lattice oxygen for fuel gasification to obtain CO and H₂Is mainly composed ofThe combustible synthesis gas of (a); and the reduced oxygen carrier enters the air reactor to be oxidized and regenerated by the air in the air reactor. Compared with the traditional gasification technology, the chemical chain gasification process effectively improves the gasification effect; in addition, the chemical chain gasification process avoids direct contact between fuel and air, avoids generation of fuel type NOx, and the oxygen carrier can catalyze tar cracking. Currently, in the biomass energy field, chemical looping gasification has attracted much attention due to its dual advantages of energy saving and gas generation.

The soil heavy metal restoration plant belongs to one type of biomass, so that the restoration plant is used as a fuel to carry out chemical chain gasification treatment, and the technical feasibility is realized. In addition, compared with the main objective of synthesizing combustible synthesis gas to realize maximum resource utilization in the conventional chemical-looping gasification of biological fuel, the restoration of the chemical-looping gasification of plants needs to realize harmless treatment in addition to effective utilization of resources. At present, the treatment of soil heavy metal restoration plants through a chemical chain has the following disadvantages:

(1) the heating mode of the fuel in traditional chemical looping gasification fuel reactor generally needs particle crushing, stirring or fluidization, and the heat is often from outside internal transfer of fuel, and heating temperature control is untimely, and the thermal efficiency is low, is unfavorable for the saving of energy, is difficult to realize that the fuel heats on the molecular level, leads to heating inequality.

(2) In the traditional chemical looping gasification method, the oxygen carrier is responsible for heat transfer and providing lattice oxygen, so that the service life of the oxygen carrier is shortened, and the efficiency of the chemical looping gasification process is reduced.

(3) The migration and conversion rules of heavy metals under the chemical chain gasification atmosphere are complex, the reaction process is variable, the mechanism of the migration and conversion of the heavy metals is complex, if the heavy metals are not removed from the synthesis gas, the heavy metals are easy to enter the environment to cause secondary pollution, and the generated synthesis gas is difficult to be effectively utilized.

Disclosure of Invention

The purpose of the invention is as follows: the invention provides a heat treatment method of a soil heavy metal restoration plant by microwave-assisted chemical looping gasification, which can effectively improve the yield and the quality of synthesis gas, and the heat treatment method has the advantages of uniform heating, convenient control and energy conservation, and solves the defects in the prior art.

The technical scheme is as follows: the invention relates to a heat treatment method of a soil heavy metal restoration plant by microwave-assisted chemical chain gasification, which comprises the following steps:

(1) putting a quartz reactor filled with a microwave absorbent fixed bed into a microwave chamber, connecting the quartz reactor with a fuel and oxygen carrier inlet, a reaction product outlet and a deionized water inlet pipeline, and starting a vacuum pump to keep a negative-pressure inert reaction environment in the reactor;

(2) the reactor is heated, deionized water is fed into the quartz reactor by a peristaltic pump, and the deionized water is converted into water vapor as a gasifying agent in the reactor.

(3) The mixture composed of the restoration plants and the oxygen carrier is semi-automatically fed into a quartz reactor through a feeder and is subjected to gasification reaction with a gasifying agent to prepare combustible synthetic gas, the oxygen carrier is converted into a low-valence oxide, the heavy metal part in the restoration plants is fixed in the residual carbon and the oxygen carrier, and the other part of the heavy metal part is migrated into the synthetic gas;

(4) the synthesis gas passes through the heavy metal adsorbent fixed bed, the contact between the synthesis gas and the heavy metal adsorbent is utilized to realize the adsorption and removal of heavy metals in the synthesis gas, the high-efficiency capture of the heavy metals contained in the restoration plants is completed, and the high-quality combustible synthesis gas is obtained.

In step S4, fly ash and tar, which are reaction products, are collected by a glass fiber filter and a condenser, respectively.

In step S1, the microwave absorbent is SiC, which has strong microwave absorption performance and particle size of 0.3-0.45 mm.

In the step S2, the quartz reactor is heated by microwave uniformly at 700-900 deg.C to obtain CO and H as combustible gases₂、CH₄And CO₂While the heavy metals migrate and solidify into the waste oxygen carrier and the syngas.

In step S3, the molar ratio O/C of the oxygen carrier to the repair plant is 0.5-2.0.

In step S3, the oxygen carrier is hematite, which has good microwave absorption performance and has the ability to adsorb and solidify heavy metals.

In the step S4, the heavy metal adsorbent fixed bed is an activated carbon fixed bed and has the performance of adsorbing and removing heavy metals, wherein the mass ratio of the activated carbon to the plant repaired in the step S3 is 0.04-0.08.

The working principle is as follows: the invention applies microwave heating to chemical chain gasification reaction for repairing plants, and takes silicon carbide as a microwave absorbent; meanwhile, the oxygen carrier is liberated, so that the oxygen carrier is only responsible for oxygen supply and is not responsible for heat transfer any more. Specifically, a quartz reactor is placed in a microwave chamber, an oxygen carrier with microwave absorption performance and heavy metal adsorption capacity is adopted, and the lattice oxygen provided by the oxygen carrier is utilized to realize gasification reforming reaction of the repairing plants, obtain high-quality combustible synthetic gas and realize the solidification of partial heavy metals in the oxygen carrier and residues; the synthesis gas flows through the activated carbon fixed bed, so that the heavy metals in the synthesis gas are adsorbed and removed, the uniform heating of the fuel, the energy conservation and the liberation of the oxygen carrier are realized, and the rapid gasification of the fuel and the improvement of the yield of the synthesis gas are facilitated; through the screening and use of the oxygen carrier, the good absorption of the oxygen carrier to microwave and the adsorption and solidification of heavy metals in the fuel are realized; the synthesis gas is contacted with the heavy metal adsorbent to further adsorb and remove heavy metals in the synthesis gas, so that ideal energy utilization rate and heavy metal removal rate are obtained, and harmless and recycling post-production treatment of heavy metal contaminated soil remediation plants is realized.

Has the advantages that: compared with the traditional treatment method of the soil heavy metal restoration plants, the method has the following advantages:

(1) the invention obtains high-quality synthesis gas by chemical chain gasification, and realizes resource utilization of soil heavy metal restoration plants.

(2) The microwave heating mode is adopted to provide heat for chemical chain gasification reaction of the repaired plant, so that the heating uniformity, the heating control instantaneity and the energy saving are realized.

(3) By paving the powerful microwave absorbent silicon carbide fixed bed in the reactor, the heat transfer is enhanced, and the rapid gasification of the repair plants and the improvement of the yield of the synthesis gas are promoted.

(4) In the traditional chemical chain, the oxygen carrier is in charge of oxygen supply and heat transfer, and the microwave heating mode is adopted, so that the oxygen carrier is liberated and only in charge of oxygen supply, and the oxygen carrier has good microwave absorption performance and the capacity of adsorbing and solidifying heavy metals.

(5) Besides the trapping of heavy metals by the oxygen carrier, the synthesis gas flows through the activated carbon fixed bed, and the heavy metals are further adsorbed and removed by utilizing the contact between the synthesis gas and the activated carbon fixed bed, so that the quality of the synthesis gas is improved, and the harmless utilization of the restoration plants is realized.

Drawings

FIG. 1 is a schematic diagram of a method for repairing plants by microwave-assisted chemical looping gasification treatment according to the present invention.

Detailed Description

The present invention will be described in further detail with reference to specific examples.

As shown in fig. 1, the heat treatment method of the present invention includes the steps of:

(1) after a high-efficiency microwave absorbent silicon carbide (SiC) fixed bed 9 is laid in a quartz reactor 8, the quartz reactor 8 is placed in a microwave chamber 6 for microwave heating; after the fuel and oxygen carrier inlet 5, the reaction product outlet 10 and the deionized water inlet 18 are connected, the vacuum pump 16 is started to keep the inert reaction environment of negative pressure in the reactor.

(2) And starting microwave heating, and when the temperature of the silicon carbide fixed bed measured by the thermocouple 11 reaches the test temperature of 700-900 ℃, starting the peristaltic pump 2 to pump the deionized water 1 into the quartz reactor 8 to produce water vapor as a gasifying agent.

(3) The mixture 4 of the repair plant and the oxygen carrier is semi-automatically conveyed into a quartz reactor 8 through a feeder 3, once the mixture 4 is contacted with a silicon carbide fixed bed 9, the microwave-assisted chemical chain gasification reaction is started to generate combustible synthesis gases CO and H₂、CH₄And CO₂Oxygen carrier is reduced to suboxide for repairing the implantThe heavy metal in the material is partially fixed in the carbon residue and the oxygen carrier, and the other part of the heavy metal is migrated into the synthesis gas. The main chemical equations that occur are:

biomass → syngas (CO)₂,H₂,CO,CH₄,C_mH_n,..) + tar and carbon residue

C_mH_n+H₂O→CO₂+H₂+CO

Tar + H₂O→CO₂+H₂+CO+...

CH₄+H₂O→CO+3H₂

C+H₂O→CO+H₂

C+CO₂→2CO

CH₄+3Fe₂O₃→CO+2Fe₃O₄

C+2Fe₂O₃→CO₂+FeO

Tar + Fe₂O₃→CO₂+CO+H₂+Fe₃O₄/FeO+...

C_mH_n+Fe₂O₃→CO₂+CO+H₂+H₂O+Fe₃O₄/FeO

3FeO+H₂O→H₂+Fe₃O₄

CH₄+Fe₂O₃→2H₂+CO+2FeO

CO+H₂O→CO₂+H₂

CO+3Fe₂O₃→CO₂+2Fe₃O₄

CO+Fe₂O₃→CO₂+2FeO

H₂+3Fe₂O₃→H₂O+2Fe₃O₄

H₂+Fe₂O₃→H₂O+2FeO

(4) The desired reaction temperature in the reactor was maintained by Pulse width modulation, PWM, to keep the microwave oven on and off alternately every 15 seconds.

(5) A glass fiber filter 12 and a condenser 13 are used for respectively collecting fly ash and tar which are reaction products; combustible synthesis gas generated by the reaction passes through the activated carbon fixed bed 17 and contacts with activated carbon at the temperature of 45 ℃, and heavy metals in the synthesis gas are adsorbed and removed to obtain high-quality synthesis gas.

The following examples are provided to illustrate the heat treatment method of the plant for restoring heavy metals in soil by microwave-assisted chemical looping gasification of the present invention: