CN112760109A

CN112760109A - Method for comprehensively utilizing waste computer circuit boards through microwave pyrolysis

Info

Publication number: CN112760109A
Application number: CN202011493726.5A
Authority: CN
Inventors: 刘大方; 舒波; 夏洪应; 张利波; 李江平; 王恩志; 刘承飞; 张鑫; 张威; 曾抗庆; 余彬; 陈习堂; 杨益芬; 田强坤
Original assignee: Chuxiong Dianzhong Nonferrous Metal Co ltd; Kunming University of Science and Technology
Current assignee: Chuxiong Dianzhong Nonferrous Metal Co ltd; Kunming University of Science and Technology
Priority date: 2020-12-17
Filing date: 2020-12-17
Publication date: 2021-05-07

Abstract

The invention relates to a method for comprehensively utilizing waste computer circuit boards through microwave pyrolysis, which belongs to the technical field of recycling of waste electronic products, and the method comprises the steps of preheating the circuit boards, removing soldering tin, cutting the circuit boards into small pieces, adding carbon powder for microwave pyrolysis, and controlling the microwave pyrolysis conditions to realize comprehensive utilization of the waste computer circuit boards; the invention can effectively remove bromine in the circuit board, simultaneously avoids the generation of toxic gases such as dioxin and the like, generates pyrolysis oil and pyrolysis gas with high calorific value, and realizes the full, high calorific value and comprehensive utilization of all components of the circuit board.

Description

Method for comprehensively utilizing waste computer circuit boards through microwave pyrolysis

Technical Field

The invention belongs to the technical field of recycling of waste electronic products, and particularly relates to a method for comprehensively utilizing waste computer circuit boards through microwave pyrolysis.

Background

From the late stage of the 20 th century, scientific technology is changing day by day, global economy is rapidly developing, the development of scientific technology also enables the electric and electronic industry and the communication industry to change over the world, electronic products are updated faster and faster, the service life of the electronic products is shortened rapidly, and more waste electronic devices are caused, such as: the waste of household electronic products such as printers, computers, mobile phones, televisions, air conditioners, etc., and some discarded electronic computers, which results in a huge amount of electronic waste. There is data showing that a global annual large summary produces 4000- & 5000 ten thousand tons of electronic waste and still continues to grow at a rate of 3-5% per year.

The electronic waste is randomly discarded and cannot be properly treated, so that the ecological environment is seriously influenced, the health of human beings is harmed, and the resource recycling is hindered. The electronic waste is mainly composed of two components, namely plastic material and metal material, wherein the metal accounts for about 60% of the total weight, and the plastic organic material accounts for 20%. The electronic waste also contains basic metals such as copper, iron, aluminum and the like, and rare and precious metals such as germanium, gold, silver, platinum and the like. According to the research results, 0.45Kg of gold, 1Kg of iron, 58.5Kg of lead, 19.8Kg of antimony, 128.7Kg of copper, 36Kg of nickel and 39.6Kg of tin are contained in every 1000Kg of computer and computer accessories. Therefore, it is necessary to recover valuable components from computers and computer accessories. Some methods for burning and treating residual substances after valuable components are recovered by physically stripping the valuable components from the low-value components not only can generate a large amount of carcinogenic toxic gases and smoke dust, but also seriously violate the environmental protection treatment requirement, thereby causing great social harm. The metal content in the electronic waste is several times to dozens of times higher than that in the ore resource, and the electronic waste is an important resource. The recovery and extraction of metals from the electronic waste can not only save limited resources, but also obtain very good economic benefits.

At present, waste circuit boards are recycled by a plurality of methods, such as physical recycling method, pyrometallurgy, electrolysis method and the like, but the methods have the defects of large pollution, high energy consumption, long process flow, insufficient comprehensive utilization of resources, incomplete recycling and the like. Patents CN104028530A "method for processing waste circuit boards" and CN111644443A "method for comprehensively recovering waste circuit boards" both disclose methods for processing circuit boards, in which a circuit board is oxidized and pyrolyzed in air atmosphere to obtain copper oxide, and then copper is recovered by a wet metallurgy method. Although valuable metals are recovered by the method, the following problems exist: harmful gases such as dioxin and the like can be generated in the pyrolysis process, so that serious environmental risks are caused; harmful bromine is difficult to remove; valuable metals are oxidized, phases of the valuable metals such as copper, tin and the like are changed to form oxides, the subsequent separation method of solid-phase substances after pyrolysis is influenced, and the separation method can be reduced for a separation extraction method.

Disclosure of Invention

In order to overcome the problems in the background art, the invention provides a method for comprehensively utilizing waste computer circuit boards through microwave pyrolysis, which can effectively remove bromine in the circuit boards, simultaneously avoid the generation of toxic gases such as dioxin and the like through process optimization control, generate pyrolysis oil and pyrolysis gas with high heat value, and realize the full, high heat value and comprehensive utilization of all components of the circuit boards.

In order to realize the purpose, the invention is realized by the following technical scheme:

the method for comprehensively utilizing the waste computer circuit boards through microwave pyrolysis comprises the following steps:

(1) heating the circuit board to 240 plus 270 ℃, preserving heat for 10min, and vibrating to lead the tin soldering to fall off and be recovered.

(2) And removing the components on the circuit board, and cutting the circuit board into small blocks.

(3) Performing microwave pyrolysis on the sheared circuit board in a nitrogen atmosphere, wherein the microwave power intensity is more than 10g/KW, the heating rate is 60-100 ℃/min, and the temperature is raised to 400-800 ℃ for heat preservation and pyrolysis;

(4) the pyrolysis gas is forcibly cooled below-3 ℃.

Further, the nitrogen flow rate is kept between 0.1 and 0.5 L.min in the pyrolysis process in the step (3)^-1。

Further, after microwave pyrolysis of the waste computer circuit board, the obtained hydrogen has the content of 60-75 percent and the heat value of 18-25MJ/Nm³The hydrogen-rich high-heating value fuel gas; obtaining the liquid fuel oil containing 80-87% of phenol, 4-isopropyl phenol and 2, 3-dihydro-2-methyl benzofuran and having the calorific value of 20-28 MJ/Kg.

Furthermore, after microwave pyrolysis of the waste computer circuit board, the bromine removal rate of the circuit board is 90-95%, and low-bromine carbon-containing copper-rich solid is obtained.

Further, the circuit board is cut to 1-2cm in the step (2)²And (5) small blocks.

The invention has the beneficial effects that:

(1) the method has the advantages of short experimental process, convenient operation, simple process, low energy consumption, low cost and the like by introducing nitrogen as protective gas; (2) directly cut the circuit boardCutting into 1-2cm²The small blocks are put into a microwave oven for pyrolysis, so that the crushing process in the conventional pyrolysis is omitted, the process flow is reduced, and the crushing cost is saved; (3) microwave pyrolysis is carried out on the microwave power intensity of 10g/1KW, 5-10% of carbon, coke and other strong absorption microwave materials are added, the heating rate is increased to 60-100 ℃/min, the temperature is rapidly increased to a preset pyrolysis temperature, the temperature generated by dioxin can be rapidly exceeded, the generation of the dioxin is reduced, 90-95% of harmful substance bromine can be removed from the materials, the concentrated absorption treatment is facilitated, and the recycling is realized; (4) the flow rate of the gas introduced during the pyrolysis process is 0.1-0.5 L.min^-1Nitrogen is used for ensuring non-oxidizing atmosphere, avoiding oxidation of metal, gas and liquid products, reducing oxidation, secondary decomposition and carbon dioxide generation of pyrolysis gas, and generating more high-calorific-value gas such as hydrogen; 0.1-0.5 L.min^-1Nitrogen purging can enable gas generated by the reaction to rapidly escape from the high-temperature pyrolysis reaction area, reduce secondary reaction and reduce generation of dioxin, and obtain phenol, 4-isopropylphenol and 2, 3-dihydro-2-methylbenzofuran liquid with concentrated products; the proper gas flow reduces the influence on the temperature in the pyrolysis process; (5) pyrolysis gas passes through a strong cooling circulation system at the temperature of-3 ℃, so that the gas can be rapidly cooled to room temperature and crosses a dioxin generation temperature interval, the generation of dioxin is reduced, and gas-liquid separation is more efficiently and thoroughly realized; (6) the method can obtain hydrogen-rich high heat value (18-25 MJ/Nm) containing 60-75% of hydrogen by microwave fast pyrolysis³) The fuel gas is used as a heat source of the hot air for detinning; 80-87% of high-calorific-value (20-28MJ/Kg) liquid fuel containing phenol, 4-isopropylphenol and 2, 3-dihydro-2-methylbenzofuran, and low-bromine, carbon-containing and copper-rich (26-30%) solid, gas and liquid can be used as high-calorific-value fuel, so that high-value utilization is realized; (7) low-bromine, carbon-containing, copper-rich (26-30%) and silicon-aluminum-calcium solid, which can be used as raw material for copper smelting, wherein the carbon provides heat source for the smelting process and reduces energy consumption; the silicon-aluminum-calcium is used as the main component of the slag phase, and the slag blending is reduced. The invention can realize the full, high-valued and comprehensive utilization of all components of the pyrolysis of the waste computer circuit board, reduce the pollution caused by random abandonment or insufficient recycling of the circuit board and realize the cyclic utilization of resources and the sustainable development of enterprises.

Drawings

FIG. 1 is a graph of the solid, gas and liquid yield profiles of a circuit board according to example 2 of the present invention;

FIG. 2 is a scanning electron micrograph and a power spectrum of a solid residue after microwave pyrolysis according to example 2 of the present invention;

in fig. 2, 1 and 2 are electron probe numbers.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, preferred embodiments of the present invention will be described in detail below to facilitate understanding of the skilled person.

(1) the circuit board is placed into a hot blast stove to be heated to the temperature of 240-.

(2) Manually removing components on the circuit board, and cutting the circuit board to 1-2cm²Small pieces of (a).

(3) Performing microwave pyrolysis on the sheared circuit board in a nitrogen atmosphere, wherein the microwave power intensity is more than 10g/1KW, the heating rate is 60-100 ℃/min, the temperature is raised to 400-plus-material 800 ℃, the thermal pyrolysis is performed, and the nitrogen flow rate is kept at 0.1-0.5 L.min in the pyrolysis process^-1. Through rapid heating to pyrolysis temperature, cross the temperature interval that the dioxin generated fast, reduce the dioxin production in a large number to get rid of 90-95% harmful substance bromine from the material, be convenient for concentrate recovery processing, realize recycle.

Microwave pyrolysis is carried out in a nitrogen atmosphere, oxidation reaction in the pyrolysis process is avoided, phase change of metal oxidation products is avoided, oxidation, secondary decomposition and carbon dioxide generation of pyrolysis gas are reduced, more high-calorific-value gas such as hydrogen is generated, secondary oxidation of liquid products is reduced, and the simplicity and uniformity of the products are facilitated; more solid carbon is retained in the slag, and the use of an external heating source can be reduced in the subsequent pyrometallurgical smelting of solid residues.

0.1-0.5L·min^-1The nitrogen is used for purging, so that the gas generated by the reaction can quickly escape from the high-temperature pyrolysis reaction area, and the number of the nitrogen is reducedPerforming secondary reaction, reducing the generation of dioxin, and obtaining phenol, 4-isopropylphenol and 2, 3-dihydro-2-methylbenzofuran liquid with concentrated products; too large gas flow can cause the pyrolysis temperature to reduce, increase tail gas volume, and too little heat can not play the effect of sweeping.

(4) The pyrolysis gas is forcibly cooled below-3 ℃. The gas can be rapidly cooled to the room temperature and cross the dioxin generation temperature interval, so that the generation of dioxin is reduced, and the gas-liquid separation is more efficiently and thoroughly realized.

After pyrolysis, the bromine removal rate in the circuit board is 90-95%. The obtained hydrogen content is 60-75%, and the heat value is 18-25MJ/Nm³The hydrogen-rich high-heating value fuel gas; obtaining liquid fuel oil which contains 80-87% of phenol, 4-isopropylphenol and 2, 3-dihydro-2-methylbenzofuran and has the heat value of 20-28MJ/Kg and can be used as high-heat value fuel; the obtained solid with low bromine content, high carbon content (20-25%), rich copper (26-30%) and calcium silico-aluminum can be used as a raw material for copper smelting, the calcium silico-aluminum is used as a main component of a slag phase, the amount of a target slag formed in the copper smelting process and the added calcium silico-aluminum oxide is reduced, and the resource utilization rate is improved.

Example 1

A method for comprehensively utilizing waste computer circuit boards through microwave pyrolysis comprises the following specific steps:

before pyrolysis, the circuit board is put into a high-temperature hot air furnace, heated to 250 ℃, kept warm for 10min, rapped to recover soldering tin, and subjected to detinning pretreatment. Manually removing components on the circuit board, and shearing the circuit board to 1cm by using a plate shearing machine²Small pieces of (a). And opening a cooling liquid circulating pump, and setting the temperature of condensed water in the circulating cooling system to be-3 ℃. And (3) putting the circuit board small blocks into a microwave oven, after the airtightness is checked, firstly introducing 10min nitrogen to exhaust air in a pipeline, then heating to 400 ℃ at the heating rate of 25 ℃/min under the microwave intensity of 10g/1KW for pyrolysis for 1h, and controlling the nitrogen flow rate to be 0.1L/min in the pyrolysis process.

The solid, liquid and gas yields obtained after pyrolysis were 77.9%, 13.7%, 8.4%, respectively. The recovery rates of copper and tin in the solid product after microwave pyrolysis are obtained by analysis (here, the recovery rate of tin refers to the total recovery rate of tin after detinning and pyrolysis) 99.85% and 94.17% respectively, the main components of pyrolysis gas are hydrogen and carbon dioxide, wherein the hydrogen accounts for 47.3%, the carbon dioxide accounts for 33.6%, the carbon monoxide accounts for 11.2%, and the heat value of the pyrolysis gas reaches 14.36MJ/Nm³Wherein the content of dioxin is 2.65ng TEQ/m³Out of national emission standards; the pyrolysis oil has simple components, contains 72 percent of phenol (56.61 percent), 4-isopropyl phenol and 2, 3-dihydro-2-methylbenzofuran, and has the heat value of 18.4 MJ/Kg; bromine was removed 56.5%.

Example 2 (carbon powder was added to the circuit board, other conditions were the same as in example 1)

before pyrolysis, the circuit board is put into a high-temperature hot air furnace, heated to 250 ℃, kept warm for 10min, rapped to recover soldering tin, and subjected to detinning pretreatment. Manually removing components on the circuit board, and shearing the circuit board to 1cm by using a plate shearing machine²Small pieces of (a). And opening a cooling liquid circulating pump, and setting the temperature of condensed water in the circulating cooling system to be-3 ℃. And (2) mixing a small block of the circuit board with 5% of coke powder by mass, loading the small block of the circuit board into a microwave oven, introducing 10min of nitrogen to empty air in a pipeline after checking the air tightness, heating to 400 ℃ for pyrolysis for 1h at the heating rate of 60 ℃/min under the microwave intensity of 10g/1KW, and controlling the nitrogen flow rate to be 0.1L/min in the pyrolysis process.

The solid, liquid and gas yields obtained after pyrolysis were 80.95%, 12.45% and 6.6%, respectively. The recovery rates of copper and tin in the solid product obtained after microwave pyrolysis are respectively 99.86% and 94.47% through analysis, the main components of pyrolysis gas are hydrogen and carbon monoxide, wherein the hydrogen accounts for 62%, and the heat value of the pyrolysis gas reaches 18.89MJ/Nm³Wherein the content of dioxin is only 0.125ng TEQ/m³Is superior to the national emission standard; the pyrolysis oil has simple components, contains 82 percent of phenol (62.61 percent), 4-isopropyl phenol and 2, 3-dihydro-2-methylbenzofuran and has the heat value of 22.4 MJ/Kg; bromine was removed by 90.6%. Can realize the high-efficiency and high-value utilization of each component.

And (3) carrying out electronic probe point energy spectrum component analysis on the solid residue after microwave pyrolysis to obtain an analysis result as follows:

TABLE 1 analysis results of electron probe point energy spectrum components of solid residue after microwave pyrolysis

Remark Wt^aRepresents the mass percentage of the element; at^bIndicates the atomic percentage of the element.

By adding the coke powder into the circuit board, the heating rate is obviously increased, the hydrogen concentration in the obtained gas is also increased, and the dioxin content is obviously reduced. The main reason is that the coke powder has stronger microwave absorbing capacity, the material temperature rising rate is obviously improved, and then the generation temperature interval of the dioxin is quickly avoided, and the generation of the dioxin is greatly reduced. Meanwhile, the coke powder can absorb trace oxygen in the microwave atmosphere, and secondary oxidation of the residual oxygen to the cracked gas is effectively prevented.

Example 3 (otherwise same as example 2, control of different pyrolysis temperatures)

The other conditions were controlled exactly as in example 2, and the pyrolysis temperature alone was controlled to obtain the following pyrolysis oil compositions at different pyrolysis temperatures.

TABLE 2 influence of pyrolysis temperature on TXDN liquid product composition

As can be seen from the figures and tables, the pyrolysis temperature is increased, the solid residue production is reduced, the liquid yield is increased and then reduced, and the maximum value is 15.15% at 600 ℃; the gas yield is gradually increased. In the range of 500-600 ℃, epoxy resin and other high molecular chains contained in the material are heated and broken to be changed into long chain compounds, so that liquid products are increased; as the temperature continues to increase, the liquid products undergo a secondary decomposition reaction before volatiles escape from the reactor, the long chain compounds undergo further cracking reactions to become short chain gaseous compounds, the gaseous products increase and the corresponding liquid products decrease. It is shown that after the temperature is increased, the reaction degree becomes severe, and the thermal decomposition product is increased, the nitrogen flow rate needs to be increased to reduce the secondary cracking reaction. Meanwhile, the temperature is increased, which is beneficial to removing the bromine with removing rate.

Example 4

before pyrolysis, the circuit board is put into a high-temperature hot air furnace, heated to 260 ℃, insulated for 10min, rapped to recover soldering tin, and subjected to detinning pretreatment. Manually removing components on the circuit board, and shearing the circuit board to 1.5cm by using a plate shearing machine²Small pieces of (a). And opening a cooling liquid circulating pump, and setting the temperature of condensed water in the circulating cooling system to be-4 ℃. And (3) putting the circuit board small blocks into a microwave oven, after the airtightness is checked, introducing 10min nitrogen to exhaust air in a pipeline, heating to 600 ℃ for pyrolysis for 1h at the heating rate of 46 ℃/min under the microwave intensity of 10g/5KW, and controlling the nitrogen flow rate to be 0.3L/min in the pyrolysis process.

The solid, liquid and gas yields obtained after pyrolysis were 78.58%, 14.95%, 6.47%, respectively. The recovery rates of copper and tin in the solid product obtained after microwave pyrolysis are respectively 99.87% and 94.02% through analysis, the main components of pyrolysis gas are hydrogen and carbon monoxide, wherein the hydrogen accounts for 55.3%, and the heat value of the pyrolysis gas reaches 16.13MJ/Nm³Wherein the content of dioxin is only 1.525ng TEQ/m³(ii) a The pyrolysis oil has relatively simple components, contains 77.4 percent of phenol (58.1 percent), 4-isopropyl phenol and 2, 3-dihydro-2-methylbenzofuran, and has a heat value of 19.8 MJ/Kg; bromine was removed by 76.5%.

Example 5 (carbon powder was added to the circuit board, other conditions were the same as in example 4)

before pyrolysis, the circuit board is put into a high-temperature hot air furnace, heated to 260 ℃, insulated for 10min, rapped to recover soldering tin, and subjected to detinning pretreatment. Manually removing components on the circuit board, and shearing the circuit board to 1.5cm by using a plate shearing machine²Small pieces of (a). And opening a cooling liquid circulating pump, and setting the temperature of condensed water in the circulating cooling system to be-4 ℃. And (3) mixing the small circuit board blocks with coke powder accounting for 8% of the mass percentage, loading the mixture into a microwave oven, introducing 10min of nitrogen to exhaust air in a pipeline after checking airtightness, heating to 600 ℃ at a heating rate of 90 ℃/min under the microwave intensity of 10g/5KW for pyrolysis for 1h, and controlling the nitrogen flow rate to be 0.3L/min in the pyrolysis process.

The solid, liquid and gas yields obtained after pyrolysis were 76.95%, 10.45%, 12.6%, respectively. The analysis shows that the recovery rates of copper and tin in the solid product after microwave pyrolysis are respectively 99.79% and 94.57%, the main components of pyrolysis gas are hydrogen and carbon monoxide, wherein the hydrogen accounts for 71.5%, and the heat value of the pyrolysis gas reaches 23.35MJ/Nm³Wherein the content of dioxin is only 0.025ng TEQ/m³Is superior to the national emission standard; the pyrolysis oil has simple components, contains 85 percent of phenol (49.38 percent), 4-isopropyl phenol and 2, 3-dihydro-2-methylbenzofuran, and has a heat value of 26.3 MJ/Kg; bromine was removed 93.7%. Can realize the high-efficiency and high-value utilization of each component.

Example 6 (replacement of Nitrogen by air)

before pyrolysis, the circuit board is put into a high-temperature hot air furnace, heated to 260 ℃, insulated for 10min, rapped to recover soldering tin, and subjected to detinning pretreatment. Manually removing components on the circuit board, and shearing the circuit board to 1.5cm by using a plate shearing machine²Small pieces of (a). And opening a cooling liquid circulating pump, and setting the temperature of condensed water in the circulating cooling system to be-4 ℃. And (3) putting the circuit board small blocks into a microwave oven, after the airtightness is checked, heating to 600 ℃ at the heating rate of 46 ℃/min under the microwave intensity of 10g/5KW for pyrolysis for 1h, and introducing air with the flow rate of 0.3L/min in the pyrolysis process for timely taking out the pyrolysis gas.

The solid, liquid and gas yields obtained after pyrolysis were 65.21%, 18.38%, 16.41%, respectively. The recovery rates of copper and tin in the solid product obtained after microwave pyrolysis are respectively 99.77% and 69.14%, and the main component of pyrolysis gas is twoCarbon oxide, wherein carbon dioxide accounts for 73.2 percent, hydrogen accounts for 8.6 percent, carbon monoxide accounts for 9.7 percent, and the heat value of pyrolysis gas is 4.91MJ/Nm³Wherein the content of dioxin is 13.735ng TEQ/m³(ii) a The pyrolysis oil has complex components and more types, and the calorific value is 11.7 MJ/Kg; bromine was removed 74.9%.

Remarking: in the above examples, the gas percentage refers to volume percentage.

Finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims

1. a method for comprehensive utilization of microwave pyrolysis of waste and old computer circuit boards, is characterized in that: the method for comprehensive utilization of microwave pyrolysis of waste and old computer circuit boards comprises the following steps:

(1) Heat the circuit board to 240-270°C, keep the temperature for 10 minutes, and vibrate to make the solder fall off and recover;

(2) Remove the components on the circuit board and cut the circuit board into small pieces;

(3) Microwave pyrolysis is performed on small pieces of circuit boards in nitrogen atmosphere, the microwave power intensity is greater than 10g/1KW, the heating rate is 60-100°C/min, and the temperature is raised to 400-800°C for thermal insulation pyrolysis;

(4) The pyrolysis gas is forcibly cooled below -3°C.

2 . The method for comprehensive utilization of waste computer circuit boards by microwave pyrolysis according to claim 1 , wherein the step (3) maintains a nitrogen flow rate of 0.1-0.5L·min ⁻¹ during the pyrolysis process. 3 .

3. A method for comprehensive utilization of waste computer circuit boards by microwave pyrolysis according to claim 1 or 2, characterized in that: in step (3), carbon with a mass ratio of 5-10% is added to the small pieces of the circuit board Powder, coke powder.

4. the method for comprehensive utilization of a kind of waste computer circuit board microwave pyrolysis according to claim 1 and 2, it is characterized in that: after microwave pyrolysis of waste computer circuit board, obtain hydrogen content and be 60-75%, calorific value is 60-75% 18-25 MJ/Nm ³ of hydrogen-rich gas with high calorific value; obtain 80-87% containing phenol, 4-isopropylphenol, 2,3-dihydro-2-methylbenzofuran, calorific value 20-28MJ /Kg of liquid fuel.

5. the method for comprehensive utilization of a kind of waste computer circuit board microwave pyrolysis according to claim 1 and 2, it is characterized in that: after the waste computer circuit board microwave pyrolysis, the bromine extraction rate in the circuit board is 90-95%, A low-bromine, carbon-containing copper-rich solid is obtained.

6 . The method for comprehensive utilization of waste computer circuit boards by microwave pyrolysis according to claim 1 , wherein in step (2), the circuit boards are cut into small pieces of 1-2 cm ² . 7 .