KEYWORTH PROCESS ENGINEERING

PRODUCTION OF AMMONIA FROM NATURAL GAS

The group is constitute of 4 members, as a group we shared the task among ourselves:

1. BENJAMIN AZIZI ( Organizer )2. STEVE MUSIMWA ( Practical )3. FUNMILAYO SALAJA ( Analytical )4. JOSEPH AGYEI-BOATENG ( Researcher)

INTRODUCTION

Keyworth Ammonia Project is proposing to construct and operate an ammonia production facility to manufacture and supply ammonia from natural gas.

The main raw materials of the ammonia product are methane (CH4), some higher hydrocarbon molecules and also sulphur content.

Ammonia is produced by a reaction between nitrogen and hydrogen using Haber process. The nitrogen is obtain from the catalytic steam reforming of the natural gas (CH4)

MANUFACTURING PROCESSES

There are six processes that occur during the production of ammonia:

1. Natural gas desulphurisation 2. Catalyst steam reforming 3. Carbon monoxide shift 4. Carbon dioxide removal 5. Methanation6. Ammonia synthesis

Natural gas desulphurisation

The first stage of the process is the removal of sulphur compound from the natural gas the feedstock because sulfur deactivates the Catalyst used in subsequent steps. Sulfur removal requires catalytic Hydrogenation to convert sulfur compounds in the feedstock to gaseous Hydrogen Sulfide:

H2 + RSH → RH + H2S (gas)

There are two different processes that enable us from removing the hydrogen sulphide (H2S) from the natural gas feedstock, which are activated carbon and zinc oxide. The gaseous hydrogen sulphide is then absorbed and removed by passing it through beds of Zinc Oxide where it is converted to solid Zinc Sulphide:

H2S + ZnO → ZnS + H2O

NB: the Hydrogen Sulphide must be removed before the feed can be used for producing hydrogen; the sulphur content is reduced to less than 5ppm.

Reforming process

The reformation process is carried out in two stages: primary and secondary reforming

Catalyst steam reforming

Catalytic Steam Reforming of the sulfur-free feedstock is then used to form hydrogen plus Carbon Monoxide:

CH4 + H2O → CO + 3H2

Nickel has been found to be the most effective metal for reforming of hydrocarbons, and it is active component in most of catalyst formulation which are available.

Carbon monoxide Conversion

The next step then uses catalytic Shift conversation to convert the carbon monoxide to carbon dioxide and more hydrogen:

CO + H2O CO2 + H2

Concentration of CO is reduced to about 0.1 – 0.3 % by volume in two stage converter.

Carbon dioxide removal

In this step, CO2 in the final shift gas is removed. CO2 removal can be done by using 2 methods: mono-ethanol-amine (C2H4NH2OH) scrubbing and hot potassium scrubbing. Approximately 80 percent of the ammonia plants use mono-ethanol-amine (MEA) to aid in removing CO2.

Methanation

The final step of producing hydrogen, the use catalytic Methanation to remove any small residual amounts of carbon monoxide or carbon dioxide as they will act as poison ammonia synthesis:

CO + 3H2 → CH4 + H2O

CO2 + 4H2 → CH4 +2H2O

Exit gas from the Methanation process, which has a 3:1 mole ratio of hydrogen and nitrogen, is then cooled to 38°C.

Ammonia synthesis

To produce the desired end-product ammonia, the hydrogen is then catalytically reacted with nitrogen (derived from process air) to form anhydrous liquid ammonia. This step is known as the ammonia synthesis loop (also referred to as the Haber- Bosch process):

3H2 + N2 → 2NH3