Removal of ammonia from fuel cell power plant water system

• US 4,801,356 A
• Filed: 10/15/1987
• Issued: 01/31/1989
• Est. Priority Date: 10/15/1987
• Status: Expired due to Fees

• Current Assignee: International Fuel Cells Corporation (Doosan Corporation)
• Original Assignee: International Fuel Cells Corporation (Doosan Corporation)
• Inventors: Grasso, Albert P.
• Primary Examiner(s): Lacey, David L.
• Assistant Examiner(s): MANOHARAN, VIRGINIA
• Application Number:
  US07/108,529
• Time in Patent Office: 474 Days
• Field of Search: 203/4, 203/12, 203/88, 203/73, 203/78, 203/79, 203/80, 203/DIG. 9, 203/DIG. 20, 203/40, 203/3, 203/DIG. 18, 159/2.1, 159/47.1, 159/47.2, 423/356, 423/DIG. 19, 55/36, 210/903, 202/173, 202/182, 202/202
• US Class Current: 203/11
• CPC Class Codes: B01D 3/06 Flash distillation
• CPC Class Codes: B01D 3/38 Steam distillation
• CPC Class Codes: C02F 1/20 by degassing, i.e. liberation of dissolved gases degasification of liquids in general B01D19/00; arrangement of degassing apparatus in boiler feed supply F22D
• CPC Class Codes: C02F 1/586 by removing ammoniacal nitrogen for biological methods C02F3/00
• CPC Class Codes: H01M 8/06 Combination of fuel cells with means for production of reactants or for treatment of residues regenerative fuel cells H01M8/18
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y10S 203/21 Acrylic acid or ester

Abstract

Ammonia which is present in fuel cell power plant water in free form, in ionic form, and in forms combined with carbon dioxide, is removed from the power plant water by steam stripping. Water which has been used to cool the fuel reformer effluent, and thus has become contaminated with ammonia, is fed to a first steam stripper wherein a first portion of the ammonia contaminant is removed. The partially stripped water is then fed to a second steam stripper wherein further amounts of ammonia are removed from the water with steam. The ammonia laden steam from the two strippers is combined and vented through a single vent thus conserving the amount of water lost from the system.

Claims

1. In a closed water cycle fuel cell power plant, a method for removing ammonia, gaseous ammonium compounds such as ammonium carbonates and bicarbonates, and carbon dioxide contaminants from contaminated water in the power plant, said method consisting essentially of the steps of:

(a) providing a stream of the contaminated water at superatmospheric pressure and elevated temperature having an ammonia content of less than about 500 ppm by weight;

(b) performing a first steam stripping operation on said stream of contaminated water by contacting the latter with steam to strip a first portion of the ammonia content from the water;

(c) performing a second steam stripping operation on the contaminated water after said first steam stripping operation is completed to strip a second portion of the ammonia content from the water, said two steam stripping operations being operable to remove at least about 85% of the ammonia and about 99% of the carbon dioxide from the contaminated water stream;

(d) combining contaminated steam exhausted from said second steam stripping operation with steam used in said first steam stripping operation during performance of the latter so that said first stripping operation is performed with a combined supply of steam and feeding combined contaminated steam exhausted from said first steam stripping operation into a condenser to condense water out of the combined contaminated steam; and

(e) venting contaminated steam from the condenser at controlled rates so that the vented steam has a water content which is less than the available amount of water produced by the electromechanical reaction in the full cell power plant.

2. The method of claim 1 wherein the steam for one of said steam stripping operations is provided by dropping the pressure of said stream of contaminated water so as to flash steam therefrom.

3. The method of claim 2 wherein the steam for the other of said steam stripping operations is supplied from a water coolant system in the power plant which controls the temperature of the fuel cells in the power plant.

4. In a closed water cycle fuel cell power plant, a method for removing ammonia, gaseous ammonium compounds such as ammonium carbonates and bicarbonates, and carbon dioxide contaminants from contaminated water in the power plant, said method consisting essentially of the steps of:

(a) providing a stream of contaminated water having an ammonium content of less than about 500 ppm by weight at a pressure in the range of about 140 or about 160 psia, and a temperature of about 255°

F.;

(b) lowering the pressure of the contaminated water stream to about 20 psia, and the temperature thereof to about 228°

F. to flash steam from said water stream to perform a first steam stripping operation on said water stream;

(c) providing a supply of steam at a temperature of about 375°

F. and a pressure of about 188 psia from a power section of the power plant;

(d) mixing steam from said supply thereof with said water stream after completion of said first stripping operation, to perform a second steam stripping operation on said water stream, said two steam stripping operations being operable to remove at least about 85% of the ammonia and about 99% of the carbon dioxide from the water stream;

(e) mixing contaminated steam exhaust from said second steam stripping operation with the flash steam in said first steam stripping operation during performance of said first steam stripping operation to form a supply of combined contaminated steam;

(f) feeding the combined contaminated steam to a condenser to condense water out of the combined contaminated steam; and

(g) venting contaminated steam from the condenser at a controlled rate so that the vented steam has a water content which is less than the available amount of water added to the water cycle by the electromechanical reaction in the fuel cells.

5. A system for removing ammonia, gaseous ammonium compounds such as ammonium carbonates and bicarbonates, and carbon dioxide contaminates from contaminated water in a fuel cell power plant having a closed water cycle, said system consisting essentially of:

(a) a first steam stripping vessel;

(b) means for delivering a supply of high pressure, high temperature contaminated water having a ammonia content of less than about 500 ppm by weight, to said first steam stripping vessel;

(c) first means for providing a supply of steam to said first steam stripping vessel for admixture therein with the contaminated water to remove a portion of the contaminants from the contaminated water;

(d) a second steam stripping vessel;

(e) means for delivering partially decontaminated water from said first steam stripping vessel to said second steam stripping vessel;

(f) second means for delivering steam to said second steam stripping vessel for admixture therein with the partially decontaminated water to remove a further portion of the contaminants from the water, said first and second steam stripping vessels being operable to remove a total of at least about 85% of the ammonia from the water, and about 99% of the carbon dioxide from the water;

(g) means for directing steam from said second steam stripping vessel to said first steam stripping vessel for combining contaminant-laden steam from said first and second steam stripping vessels;

(h) a condenser;

(i) means for feeding the combined contaminant-laden steam to said condenser to condense water out of said contaminant-laden steam; and

(j) valve means for venting dewatered contaminant-laden steam from said condenser, the vented steam, by reason of said valve means having a water content which is less than the amount of water produced by the fuel cells in the power plant whereby externally sourced makeup water is not needed to operate the system.

6. The system of claim 5 wherein said first means for delivering a supply of steam comprises a restricted orifice through which the high pressure, high temperature contaminated water flows into said first steam stripping vessel whereby the pressure of the water will drop to flash steam from the water.

7. The system of claim 6 wherein said second means for delivering steam comprises means for delivering steam from a coolant section of the power plant to said second steam stripping vessel.