41. AMMONIA PRODUCTION BASES.
Let's consider process of synthesis of ammonia of simple substances: hydrogen and nitrogen. Chemism of process can be presented by means of the reaction equation.
N2 + 3H2 2NH3 + Q
Reaction is reversible, exothermic, going with reduction of volume. As this exothermic reaction, fall of temperature will displace balance towards formation of ammonia, but at the same time the speed of chemical reaction significantly decreases. Therefore synthesis is carried out at temperature of 500-5500C and in the presence of the catalyst. And as the catalyst accelerates direct and reverse reaction equally, and temperature increase displaces balance towards iskhordny substances, these conditions are not favorable to industrial production. According to principles of mobile equilibrium for counteraction to influence of elevated temperature use pressure. Apply to synthesis of ammonia davlnniya 15-100 MPas. Distinguish three ways of production depending on the used pressure:
1. Low pressure (10-15 MPas);
2. Average pressure (25-30 MPas);
3. High pressure (50-100 MPas).
The most widespread is the second way.
As the catalyst use sponge iron with with additives of aluminum oxides, potassium, calcium, silicon.Negatively the speed of formation of ammonia is influenced by harmful impurity: water, hydrogen sulfide, carbon oxide (II). They poison the catalyst, reducing its activity. Therefore azotvodorodny mix is carefully purified. However and under these conditions only part of mix turns into ammonia. For full use of mother substances neproregirovavshy part of mix is sent to the reactor again.
Let's consider the processes proceeding at synthesis, purpose of devices.Scheme of ammonia production.
| № | Device | The purpose of the device, processes proceeding in it. |
| 1 | trubopro- waters |
Previously prepared mix consisting of 3 volumes of hydrogen and 1 volume of nitrogen moves. |
| 2 | turbo - compressor |
Azotvodorodny mix compresses up to the certain pressure, neokhodimy for this process. |
| 3 | synthesis column | Column of synthesis of prenaznachen for carrying out process of synthesis of ammonia. In the contact device regiments with the catalyst are located. Process of synthesis is strongly exothermic, proceeds with big allocation of heat which part is spent for heating of the arriving azotvodorodny mix. The mix which is coming out synthesis column consists of ammonia (20-30%) and neproregirovavshy nitrogen and hydrogen. |
| 4 | holodil- nickname |
It is intended for mix cooling. Easily we compress ammonia and with high pressure turns into liquid. When escaping the refrigerator the mix consisting of liquid ammonia and not reacted azotvodorodny mix is formed. |
| 5 | separator | It is intended for separation of liquid ammonia from gaseous phase. Ammonia gathers in the collection located in the bottom of separator. |
| 6 | tsirkulyatsi- this pump |
It is intended for return to not reacted mix to the contact device. Thanks to circulation it is possible to bring use of azotvodorodny mix to 95%. |
| 7 | ammiako- wire |
It is intended for transportation of liquid ammonia on warehouse. |
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