Method of preparing ammonia

Details Method of preparing ammonia Method of preparing ammonia

1990-12-28

1992-12-08

Lander, Ferris

Chemistry of inorganic compounds

Nitrogen or compound thereof

Ammonia or ammonium hydroxide

423653, 429 16, C01C 104, H01M 814

Patent

active

051697173

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to an improved method of preparing ammonia by integrating a Molten Carbonate Fuel Cell (MCFC) or an Integral Reforming Molten Carbonate Cell (IRMCFC) in a conventional process plant for the production of ammonia.
In industrial productions of ammonia, nitrogen from the air is reacted with hydrogen from a hydrogen source, e.g. a hydrocarbon or gasified coal. The ammonia synthesis process requires a significant amount of mechanical energy for make-up gas and recirculation compressors, process air compressor and refrigeration compressor.
Process plants for making ammonia are well known. They consist in principle of two main parts, i.e. a front end for preparing a suitable synthesis gas and a synthesis loop.
The front end comprises one or more reformer units where water vapour and preferably also air are added and transformation of hydrocarbons into a gas rich in hydrogen is brought about; a shift unit to convert carbon monoxide, which is a by-product from the reforming unit, into hydrogen and carbon dioxide; a unit to remove carbon dioxide; and a methanizing unit which will convert the last traces of carbon oxides into methane. Carbon dioxide is removed from the makeup gas and is often vented to the atmosphere if the plant is not designed for converting the product ammonia into urea.
It has now been found possible to improve the overall energy balance in the ammonia process by integrating certain fuel cells, especially of the Molten Carbonate type, in a conventional ammonia process plant, offering a possibility for using a purge gas containing hydrogen as well as an off-gas of carbon dioxide in a very efficient way.


BACKGROUND AND PRIOR ART

Fuel cells and more specifically Molten Carbonate Fuel Cells are well known in the art (J. R. Selman, T. D. Claar, "Proceedings of the Symposium on Molten CArbonate Fuel Cell Technology" Proceedings Volume 84-13, The Electrochemical Society, Inc.). In a fuel cell, chemical energy is converted directly into electrical energy. A fuel cell comprises electrodes: a cathode and an anode. The electrodes act as catalytic reaction sites where the fuel and oxidants are electrochemically transformed into electricity, water or carbon dioxide and heat. The electricity being produced as D.C. is conveniently transformed into A.C. before utilization, e.g. to fulfil the need (or some of the need) of a process plant.
The use of hydrogen-containing purge gas from a synthesis process is further disclosed in French patent specification No. 2,374,752 (Pinto). By the process there disclosed purge gas from, e.g., ammonia synthesis and containing only hydrogen, nitrogen, noble gases and methane is oxidized in a fuel cell to generate electricity. Residual gas from the fuel cell is recycled as fuel or process feed.
At the anode, fuel is oxidized electrochemically to give up electrons which are conducted through an external circuit to the cathode where the elecrons combine with the oxidant. The loop is closed by ions which are conducted through an electrolyte from one electrode to the other.
Molten Carbonate Fuel Cells are known in two principally different forms, i.e. simple Molten Carbonate Fuel Cells (MCFC) and Internal Reforming Molten Carbonate Fuel Cells (IRMCFC). The main characteristics of these two forms of Molten Carbonate Fuel Cell are given in Table 1:


TABLE 1 __________________________________________________________________________ MCFC IRMCFC __________________________________________________________________________ Electrolyte K.sub.2 CO.sub.3 --Li.sub.2 CO.sub.3 K.sub.2 CO.sub.3 --Li.sub.2 CO.sub.3 Electrolyte support LiAlO.sub.2 LiAlO.sub.2 Electrodes (catalysts) Ni, NiO Ni, NiO Anode fuel H.sub.2, CO Natural gas, H.sub.2, CO Cathode oxidant Air + CO.sub.2 Air + CO.sub.2 Temp., .degree.C. 600-700 600-700 Pressure <120 psia [<8.437 kg/cm.sup.2 abs.] <120 psia [<8.437 kg/cm.sup.2 abs.] Cell voltage, V <0.85 <0.85 Impurity tolerance No H.sub.2 S No H.sub.2 S Anodic reaction

REFERENCES:
patent: 3488226 (1970-01-01), Baker et al.
patent: 4309359 (1982-01-01), Pinto
patent: 4522894 (1985-06-01), Hwang et al.
patent: 4810485 (1989-03-01), Marianowski et al.
J. H. Altseimer et al., "Applications of Fuel Cells to the Petroleum Refining Industry", 1986 Fuel Cell Seminar, pp. 354-357.
J. R. Selman et al., "Structure and Performance of the Fuel electrode in the Molten Carbonate Fuel Cell", in Proceedings of the Symposium on Molten Carbonate Fuel Cell Technology, vol. 84-13.

Affiliated with

Also associated with

Rating

Method of preparing ammonia does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of preparing ammonia, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of preparing ammonia will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-960192