Reduction of coal-fired combustion emissions

• US 7,276,217 B2
• Filed: 08/16/2005
• Issued: 10/02/2007
• Est. Priority Date: 08/16/2004
• Status: Active Grant

• Current Assignee: Premier Magnesia, LLC
• Original Assignee: Premier Chemicals LLC
• Inventors: Radway, Jerrold E., Miller, Thomas M.
• Primary Examiner(s): Vanoy; Timothy C.
• Application Number:
  US11/204,765
• Publication Number:
  US 20060034743A1
• Time in Patent Office: 777 Days
• Field of Search: 423/244.1, 423/244.01, 423/244.08, 423/210, 431/2, 110/218, 110/342, 110/343
• US Class Current: 423/210
• CPC Class Codes: B01D 53/508 by treating the gases with solids
• CPC Class Codes: B01D 53/64 Heavy metals or compounds thereof, e.g. mercury
• CPC Class Codes: C10L 9/10 by using additives
• CPC Class Codes: F23J 2215/20 Sulfur; Compounds thereof
• CPC Class Codes: F23K 1/00 Preparation of lump or pulverulent fuel in readiness for delivery to combustion apparatus
• CPC Class Codes: F23K 2201/101 to a specific particle size
• CPC Class Codes: F23K 2201/505 with additives

Abstract

A process for mitigation of fouling deposits within a combustion zone, capturing of toxic metal emissions, and reduction of visible sulfur emissions attributable to sulfuric acid mist during coal combustion. SO₃ formed during coal combustion is reduced by the addition to the coal of raw, unprocessed magnesium-containing minerals such as magnesite ore or brucite ore. The minerals are pulverized to a fine particle size and combined with pulverized coal to provide a mixture of the particles. The mixture is combusted and the ore particles calcine and decrepitate to very fine magnesium oxide particles that have a significant particle surface area. The magnesium oxide particles react with the SO₃ produced during combustion of the coal and also capture toxic metals to reduce the quantity of undesirable stack discharge components.

Claims

1. A process for reducing visible sulfur emissions attributable to sulfuric acid mist during coal combustion, said process comprising the steps of:

mixing together a raw, unprocessed magnesium carbonate ore and coal to form a coal-ore mixture that results in a ratio of elemental magnesium to sulfur trioxide in flue gas of at least 1;

1;

pulverizing the coal-ore mixture prior to combustion to provide coal-ore mixture particles that do not exceed −

200 mesh; and

combusting the coal-ore mixture particles at a temperature sufficient to cause ore particles to calcine and decrepitate to magnesium oxide particles having a particle specific surface area of from about 200 m²/g to about 5 m²/g to absorb toxic metals and react with sulfur trioxides formed during combustion.

2. A process as claimed in claim 1 wherein the magnesium carbonate ore is pre-pulverized prior to mixing with the coal.

3. A process as claimed in claim 1 wherein the elemental magnesium in the ore to sulfur trioxide in the flue gas is from about 1:

1 to about 10;

1.

4. A process as claimed in claim 1 wherein the ore is intimately mixed with the coal and reacts with ash components to yield ash deposits that are friable and readily removed from furnace convective pass tubes.

5. A process as claimed in claim 1 wherein the toxic metals are selected from the group consisting of mercury, arsenic, lead, cadmium, and selenium.

6. A process as claimed in claim 1 wherein the magnesium carbonate ore is magnesite.

7. A process as claimed in claim 1 wherein the magnesium carbonate ore is brucite.