# US 4,391,207 A · Method of conditioning exhaust gases from coal firing

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- Number: US 4,391,207 A
- Document ID: US4391207A
- Status: Granted
- Kind: A
- Application number: 06/313,795
- Filed: 1981-10-22
- Granted: 1983-07-05
- Earliest claimed: 1979-07-25
- Assignees: F. L. Smidth & Co.
- Inventors: Helge H. Petersen
- Web page: https://patentgrep.com/patent/US4391207A

## CPC

- B03C 3/013: Conditioning by chemical additives, e.g. with SO3
- C10L 10/02: for reducing smoke development
- F27B 7/2025: {consisting of a single string of cyclones}
- B03C: MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS (separating isotopes B01D59/00; combinations of magnetic or electrostatic separation with separation of solids by other means B03B, B07B)
- C10L: FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
- F27B: FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS

## Abstract

The present invention relates to operation of a rotary kiln plant utilizing electrostatic precipitators. Specifically, this invention is directed to a method for conditioning exhaust gases from a burning process in a rotary kiln in which mineral materials are treated by burning a fuel. The method comprises adding a water soluble alkali-metal compound to a solid fuel, at least part of which is a solid pulverized fuel, and then firing the fuel in the kiln plant, whereby the resistivity of the exhaust gases is less than about 10.sup.10 ohm cm.

## Claims

### Claim 1

A method of conditioning exhaust gases, containing substantial amounts of dust and lesser amounts of fly ash, from burning processes in a kiln plant, with an electrostatic precipitator, for the treatment of mineral materials which produce the substantial amounts of dust during treatment comprising:
(a) taking a solid fuel;
(b) adding to said fuel at least one alkali-metal compound;
(c) grinding said solid fuel and alkali-metal compound such that at least a portion of the fuel assumes a solid pulverized condition;
(d) feeding into a rotary kiln mineral materials which, upon burning, produce substantial amounts of dust;
(e) introducing said fuel into the rotary kiln in its ground condition;
(f) firing the treated, solid ground fuel in the kiln to burn the mineral materials thereby producing a mineral product and exhaust gases containing the substantial amounts of dust and lesser amounts of fly ash which now contain alkali-metal to reduce resistance;
(g) separating the exhaust gases and the alkali-metal and dust and fly ash by precipitation in the electrostatic precipitator; and
(h) recovering the conditioned exhaust gases.

### Claim 2

A method of conditioning exhaust gases, containing substantial amounts of dust and lesser amounts of fly ash, from burning processes in a kiln plant, with an electrostatic precipitator, for the treatment of mineral materials which produce the substantial amounts of dust during treatment comprising:
(a) taking a solid fuel;
(b) grinding said solid fuel such that at least a portion of the fuel assumes a solid pulverized condition;
(c) adding to said solid ground fuel at least one alkali-metal compound;
(d) feeding into a rotary kiln mineral materials which, upon burning, produce substantial amounts of dust;
(e) introducing said fuel into the rotary kiln in its ground condition;
(f) firing the treated, solid ground fuel in the kiln to burn the mineral materials thereby producing a mineral product and exhaust gases containing the substantial amounts of dust and lesser amounts of fly ash which now contain alkali-metal to reduce resistance;
(g) separating the exhaust gases and the alkali-metal and dust and fly ash by precipitation in the electrostatic precipitator; and
(h) recovering the conditioned exhaust gases.

### Claim 3 (depends on 1, 2)

The method according to claims 1 or 2 wherein said alkali-metal compound is added by sprinkling the solid fuel with a solution of said compound.

### Claim 4 (depends on 2, 3)

The method according to claims 2 or 3 wherein said alkali-metal compound is added in amounts equivalent to a content of up to about 2 percent Na.sub.2 O calculated on the basis of dust in the exhaust gas.

### Claim 5 (depends on 1, 2)

The method according to claim 1 or 2 wherein said alkali-metal compound is solid NaCl added to the fuel in a ratio of less than about 1:200.

### Claim 6 (depends on 1, 2)

The method according to claim 1 or 2 wherein said solid fuel is coal.

### Claim 7 (depends on 1, 2)

The method according to claim 1 or 2 wherein the resistivity of the exhaust gases is less than about 10.sup.10 ohm cm.

### Claim 8 (depends on 1, 2)

The method according to claim 1 or 2 wherein said alkali-metal compound is water soluble.

### Claim 9 (depends on 8)

The method according to claim 8 wherein said alkali-metal compound is NaCl.

### Claim 10 (depends on 1, 2)

The method according to claim 1 or 2 wherein said alkali-metal compound is dissolved in sea water.