Method and device using pyrolysis for recycling used printed circuit board

• US 8,308,843 B2
• Filed: 05/26/2010
• Issued: 11/13/2012
• Est. Priority Date: 05/27/2009
• Status: Active Grant

• Current Assignee: Hsieh-Sen Wu
• Original Assignee: Hsieh-Sen Wu
• Inventors: Wu, Hsieh-Sen
• Primary Examiner(s): Wyszomierski, George
• Assistant Examiner(s): McGuthry Banks, Tima M
• Application Number:
  US12/788,039
• Publication Number:
  US 20100300865A1
• Time in Patent Office: 902 Days
• Field of Search: 754/02, 754/20, 754/32, 754/29, 210/750, 294031-4034
• US Class Current: 75/402
• CPC Class Codes: B29B 17/02 Separating plastics from other materials
• CPC Class Codes: B29B 17/04 Disintegrating plastics, e.g. by millingB29B9/02, B29B11/02, B29B13/10, B29B17/02 take precedence
• CPC Class Codes: B29B 2017/0496 Pyrolysing the materials
• CPC Class Codes: B29L 2031/3425 Printed circuits
• CPC Class Codes: C10B 49/14 with hot liquids, e.g. molten metals
• CPC Class Codes: C10B 53/07 of solid raw materials consisting of synthetic polymeric materials, e.g. tyres waste in general, e.g. household waste C10B53/00; recovery or working-up of waste materials of organic macromolecular compounds or compositions based thereon by dry-heat treatment for obtaining partially depolymerised materials C08J11/10; production of liquid hydrocarbon mixtures from rubber or rubber waste C10G1/10
• CPC Class Codes: C10B 7/14 with trucks, containers, or trays
• CPC Class Codes: C22B 15/0056 Scrap treating
• CPC Class Codes: C22B 7/001 Dry processes
• CPC Class Codes: H05K 2203/178 Demolishing, e.g. recycling, reverse engineering, destroying for security purposes; Using biodegradable materials
• CPC Class Codes: H05K 3/22 Secondary treatment of printed circuits H05K3/1283 takes precedence; embedding circuits in grooves by pressure H05K3/107
• CPC Class Codes: Y02P 10/20 Recycling
• CPC Class Codes: Y02P 20/143 the feedstock being recycled material, e.g. plastics
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y02W 30/62 Plastics recycling; Rubber recycling
• CPC Class Codes: Y10T 29/49751 Scrap recovering or utilizing
• CPC Class Codes: Y10T 29/49753 Metalworking to consolidate scrap
• CPC Class Codes: Y10T 29/49755 Separating one material from another
• CPC Class Codes: Y10T 29/49757 by burning or heating

Abstract

A method and a device using pyrolysis for recycling used printed circuit board in which water (moisture) is introduced in the pyrolysis process and a fully sealed low pressure environment is established to ensure that no combustion happens in the pyrolysis process to enhance the safety of the process; pyrolysis gases generated in the process are concentrated and purified to provide useful fuels or chemical materials; therefore, the present invention can reduce process cost, improve recycling efficiency and provide processing device with high safety, thereby enhancing industry usability.

Claims

1. A method using pyrolysis for recycling a used printed circuit board, comprising the following steps:

Step 1;

dipping a used printed circuit board into melted nitrate in a reactor to start a pyrolysis process and chemical reactions, wherein water is introduced in the reactor for cooling the used printed circuit board and melted nitrate to stabilize the pyrolysis process and to maintain a positive pressure with moisture generated by heating the water, thereby removing oxygen and forcibly discharging pyrolysis gas out of the reactor;

Step 2;

using a room temperature condensing/compressing and recycling system to condense the pyrolysis gas to sort out fuel and gas for recycling;

Step 3;

separating out the melted nitrate after the pyrolysis process by using water;

wherein nitrate and halide are sorted out based on their different densities and melting points;

Step 4;

separating salt and carbon residue in carbon film generated in the pyrolysis process by using water

Step 5;

separating glass fiber and metals, wherein if solder mask copper foil is not melted, then the solder mask copper foil is separated from the used printed circuit board by applying an external force or through chemical reduction.

2. The method using pyrolysis for recycling a used printed circuit board as claimed in claim 1, wherein the moisture is a small amount of water, vaporized water, or steam.

3. The method using pyrolysis for recycling a used printed circuit board as claimed in claim 1, wherein in Step 2 the pyrolysis gas is condensed by mixing water and the pyrolysis gas, mixing oil and the pyrolysis gas, or using an indirect heat exchanger.

4. The method using pyrolysis for recycling a used printed circuit board as claim in claim 1, wherein the used printed circuit board is dipped into the melted nitrate for executing the pyrolysis process after a pre-processing, in which all components on the used printed circuit board are removed;

tin is also removed from the used printed circuit board;

or tin and solder mask copper foil are both removed from the used printed circuit board.

5. The method using pyrolysis for recycling a used printed circuit board as claimed in claim 1, wherein the melted nitrate is lithium nitrate, sodium nitrate, potassium nitrate, or a combination thereof.