Process for purifying exhaust gas using modified calcium hydroxide

• US 5,618,508 A
• Filed: 02/08/1994
• Issued: 04/08/1997
• Est. Priority Date: 05/18/1987
• Status: Expired due to Term

• Current Assignee: FTU GmbH Forschung und Technische Entwicklung im Umweltschutz
• Original Assignee: FTU GmbH Forschung und Technische Entwicklung im Umweltschutz
• Inventors: Suchenwirth, Hermann, Fichtel, Roland
• Primary Examiner(s): Bos, Steven
• Assistant Examiner(s): DUNN, THOMAS G
• Application Number:
  US08/193,238
• Time in Patent Office: 1,155 Days
• Field of Search: 423/210, 423/245.1, 423/240 R
• US Class Current: 423/245.1
• CPC Class Codes: B01D 2251/404 of calcium
• CPC Class Codes: B01D 2251/604 Hydroxides
• CPC Class Codes: B01D 2253/102 Carbon
• CPC Class Codes: B01D 53/34 Chemical or biological purification of waste gases
• CPC Class Codes: B01D 53/502 characterised by a specific solution or suspension
• CPC Class Codes: B01D 53/64 Heavy metals or compounds thereof, e.g. mercury
• CPC Class Codes: B01D 53/70 Organic halogen compounds
• CPC Class Codes: B01D 53/72 Organic compounds not provided for in groups B01D53/48 - B01D53/70, e.g. hydrocarbons
• CPC Class Codes: C04B 2/06 with addition of substances, e.g. hydrophobic agents ; Slaking in the presence of other compounds

Abstract

An enhanced calcium hydroxide, a process for its manufacture and a process for its use in the removal of volatile heavy metals from a gas is disclosed.

Claims

1. A dry absorption process for purifying an exhaust gas containing impurities selected from the group consisting of volatile heavy metals, mercury, chlorinated hydrocarbons, polychlorinated dioxines and furanes, polychlorinated biphenyls, hexachlorobenzenes and pentachlorophenols, and polyaromatic hydrocarbons, comprising the steps of:

(a) manufacturing a modified calcium hydroxide by adding from 0.1 to 25 wt. % of at least one substance selected from the group consisting of activated coal and open-hearth lignite coke to calcium hydroxide;

(b) introducing said modified calcium hydroxide in dry powder form into the exhaust gas at a temperature of 20°

to 1200°

C.;

(c) mixing said modified calcium hydroxide with the exhaust gas to absorb said impurities; and

(d) removing the modified calcium hydroxide containing the absorbed impurities from said exhaust gas.

2. The process according to claim 1, characterized in that the content of activated coal in the mixture with calcium hydroxide ranges from 0.2 to 5 wt. %.

3. The process according to claim 1, characterized in that the content of activated coal in the mixture with calcium hydroxide ranges from 0.5 to 1 wt. %.

4. The process according to claim 1, characterized in that the content of activated coal in the mixture with calcium hydroxide ranges from 0.75 to 1 wt. %.

5. The process according to claim 1, characterized in that the content of open-hearth lignite coke in the mixture with calcium hydroxide ranges from 1 to 15 wt. %.

6. The process according to claim 1, characterized in that the content of open-hearth lignite coke in the mixture with calcium hydroxide ranges from 2.5 to 10 wt. %.

7. The process according to claim 1, characterized in that the content of open-hearth lignite coke in the mixture with calcium hydroxide ranges from 3 to 10 wt. %.