Reduction of mercury in coal combustion gas system and method

• US 5,787,823 A
• Filed: 02/06/1996
• Issued: 08/04/1998
• Est. Priority Date: 09/23/1994
• Status: Expired due to Fees

• Current Assignee: Bruce Mullein Knowles
• Original Assignee: Bruce Mullein Knowles
• Inventors: Knowles, Bruce Mullein
• Primary Examiner(s): Ferensic, Denise L.
• Assistant Examiner(s): WILSON, PAMELA ANNE
• Application Number:
  US08/596,944
• Time in Patent Office: 910 Days
• Field of Search: 110/165 A, 110/165 R, 110/215, 110/216, 110/243, 110/244, 110/245, 110/345, 110/346, 110/344, 432/58
• US Class Current: 110/344
• CPC Class Codes: B01D 2257/602 Mercury or mercury compounds
• CPC Class Codes: B01D 53/64 Heavy metals or compounds thereof, e.g. mercury
• CPC Class Codes: B01D 53/83 with moving reactants
• CPC Class Codes: F23J 15/006 Layout of treatment plant
• CPC Class Codes: F23J 15/02 of purifiers, e.g. for removing noxious material traps for solid residues F23J3/04
• CPC Class Codes: F23J 2215/60 Heavy metals; Compounds thereof
• CPC Class Codes: F23J 2217/101 Baghouse type
• CPC Class Codes: F23J 2217/102 electrostatic
• CPC Class Codes: F23J 2217/40 by cyclones
• CPC Class Codes: F23J 2219/60 Sorption with dry devices, e.g. beds

Abstract

The present invention provides a system and method (1) for reducing the amount of air toxic elements, particularly mercury (16), in concentrations down to and including trace levels, from a flyash (2) laden combustion gas stream (4). The method includes a step of combusting a fuel (14), often coal or solid waste to form flyash, and a step to concentrate the interaction of the flyash (2) in the combustion gas stream (4) for use as a sorbent.

Claims

1. A method for removing mercury from a gas stream exiting a coal fired combustion chamber, comprising the steps of:

(a) introducing the gas stream into a recirculating cyclone;

(b) removing particulate matter from the cyclone; and

(c) reintroducing particulate matter removed from the cyclone into the gas stream, such that the particulate matter resides in the gas stream for a relatively increased period of time, at least a portion of the particulate matter bonding with mercury contained within the gas stream.

2. The method of claim 1, further comprising the steps of:

(a) interconnecting the cyclone and the gas stream by a feedback conduit; and

(b) interconnecting a blower to the feedback conduit, the blower thereby urging the particulate matter into the gas stream.

3. The method of claim 2, further comprising the steps of:

(a) removing a portion of the gas stream from the cyclone; and

(b) introducing the removed portion of the gas stream to an electrostatic precipitator.

4. The method of claim 3, further comprising the steps of:

(a) removing a portion of the particulate matter from the electrostatic precipitator; and

(b) introducing the particulate matter removed from the electrostatic precipitator to the cyclone.