US4256703A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fly ash collection
Assignee: WR Grace and Co Conn
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Filing: 1979-12-26
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Granted: 1981-03-17
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Expires: 1999-12-26
Abstract
Abstract To a coal-fired furnace that uses electrostatic precipitation or a mechanical collector to collect fly ash, a mix of magnesia-alumina or magnesia-talc is added above the fireball (2600 DEG -3300 DEG F.). The additive increases the mean particle size of the fly ash and reduces its surface resistivity, thereby causing improved collection in the electrostatic precipitators or mechanical collector. Fine particulates containing heavy metals tend to be agglomerated; thus the invention permits recovery of substantial amounts of heavy metal contaminants that would otherwise be lost as stack emission.
Inventors
- 👤 Shyam N. S. Dixit
- 👤 Douglas I. Bain
- 👤 David A. Carter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 00:06
CPC Classifications
B; B03; B03C; B03C3/00; B03C3/01; B03C3/013; B01; B01D; B01D51/00; B01D51/02; B01D51/04; C; C10; C10L; C10L10/00; C10L10/02
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
64 words
Method of improving the collection characteristics of particles entrained in a stream of particle-laden gas formed by burning coal comprising feeding an additive to the particle-laden gas at a temperature of 2600° to 3300° F., above the fireball, and at a rate of 0.05 lbs-10 lbs. per ton of coal burned; said additive consisting essentially of a mixture of magnesia with alumina or talc.
Claim 2
Dependent Claim
64 words
Method of improving the collection characteristics of particles entrained in a stream of particle-laden gas formed by burning coal comprising feeding an additive to the particle-laden gas at a temperature of 2600° to 3300° F., above the fireball, and at a rate of 0.05 lbs-10 lbs. per ton of coal burned; said additive consisting essentially of a mixture of magnesia with alumina or talc.
Claim 3
Dependent Claim
17 words
Method according to claim 1 where the particle-laden gas is at a temperature of about 3000° F.
Claim 4
Dependent Claim
23 words
Method according to claim 1 where the additive feed is at a rate of 0.1 to 2 lbs. per ton of coal burned.
Claim 5
Dependent Claim
15 words
Method according to claim 1 where the weight ratio of MgO:alumina or talc is 1-10:1-10.
Claim 6
Dependent Claim
10 words
Method according to claim 4 where the ratio is 1:1.
Claim 7
Dependent Claim
16 words
Method according to claim 5 in which the additive is a mixture of magnesia and alumina.
Claim 8
Dependent Claim
16 words
Method according to claim 5 in which the additive is a mixture of magnesia and talc.
Claim 9
Dependent Claim
50 words
Method according to claim 1 in which the coal burned is low sulfur coal, and in which a second additive is added to the particle laden gas; said second additive being selected from the group consisting of ammonium sulfate, ammonium bisulfate, sulfamic acid, ferrous ammonium sulfate, urea, or sulfur trioxide.
Claim 10
Independent Claim
94 words
The method of recovering heavy metal values in a coal-burning utility boiler system, said system carrying particles entrained in a stream of particle laden gas, comprising feeding an additive to the particle laden gas at a temperature of 2600° to 3300° F., above the fireball, and at a rate of 0.05 pounds-10 pounds per ton of coal burned; said additive consisting essentially of a mixture of magnesia with alumina or talc; whereby the finer particulates, carrying said heavy metal values, agglomerate into larger particulates, and said larger particulates are collected before reaching the stack.
Claim 11
Independent Claim
94 words
The method of recovering heavy metal values in a coal-burning utility boiler system, said system carrying particles entrained in a stream of particle laden gas, comprising feeding an additive to the particle laden gas at a temperature of 2600° to 3300° F., above the fireball, and at a rate of 0.05 pounds-10 pounds per ton of coal burned; said additive consisting essentially of a mixture of magnesia with alumina or talc; whereby the finer particulates, carrying said heavy metal values, agglomerate into larger particulates, and said larger particulates are collected before reaching the stack.
Claim 12
Dependent Claim
17 words
Method according to claim 9 where the particle-laden gas is at a temperature of about 3000° F.
Claim 13
Dependent Claim
23 words
Method according to claim 9 where the additive feed is at a rate of 0.1 to 2 lbs. per ton of coal burned.
Claim 14
Dependent Claim
17 words
Method according to claim 9 where the weight ratio of magnesia:alumina or talc is 10:1 to 1:10.
Claim 15
Dependent Claim
10 words
Method according to claim 12 where the ratio is 1:1.
Claim 16
Dependent Claim
16 words
Method according to claim 13 in which the additive is a mixture of magnesia and alumina.
Claim 17
Dependent Claim
16 words
Method according to claim 13 in which the additive is a mixture of magnesia and talc.
Claim 18
Dependent Claim
50 words
Method according to claim 9 in which the coal burned is low sulfur coal, and in which a second additive is added to the particle laden gas; said second additive being selected from the group consisting of ammonium sulfate, ammonium bisulfate, sulfamic acid, ferrous ammonium sulfate, urea, or sulfur trioxide.
Claim 19
Dependent Claim
15 words
The method according to claim 9 in which the agglomerated particulates contain heavy metal contaminants.
Claim 20
Dependent Claim
34 words
The method according to claim 17 in which the heavy metal is at least one metal selected from the group consisting of Cu, Fe, V, Ti, Sr, As, Hg, Se, Be, Ba, or Cr.
Claim 21
Dependent Claim
27 words
The method according to claim 17 in which the metal is at least one metal selected from the group consisting of Cu, Fe, V, Ti, or Sr.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-03-16 | 1984-09-15 | 1985-03-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-16 | 1988-09-15 | 1989-03-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-16 | 1992-09-15 | 1993-03-17 | $7700.00 | Window Closed / Lapsed |