The Haber Process

Uses of the Product



Ammonia is a product of the Haber Process. There are many uses of ammonia some of the most common ones include:

  • Use as household cleaners e.g. cloudy Ammonia
  • In vitamins , dyes and drugs ( Sulfonamides , Antimalarial)
  • Refrigerants
  • Catalysts which are used in the process of making plastics (Bakelite, Melamine resin).

The table below provides specific industries and its uses for Ammonia.

Industry
Product use
Agriculture
Considering Ammonia is a very valuable resource of nitrogen, which is vital for proper plant growth
Ammonia is also used as a fertilizer which is essential for the satisfaction of the demands of farmers growing food crops e.g.( Ammonia Nitrate , Ammonium sulphate , urea)
Petroleum
Neutralizing the acid constituents of crude oil
Protection of equipment from corrosion
Mining
Metals such as copper, nickel and molybdenum are extracted from their ores with the use of Ammonia
Rubber
For the prevention of premature coagulation ammonia is used in the rubber industry as it stabilizes natural and synthetic latex
Pulp and paper
Ammonia is used for Pulping Wood
Used for the coating of paper, it’s used as a casein dispersant.
Leather
Ammonia is used as a curing agent and a protective agent for leathers and furs in storage
Food and Beverage
Ammonia is used as a source of nitrogen which is needed for yeast and microorganisms


Le Chatalier's Principal

LeChatelier_tcm23-29665.gif

The production of Ammonia is an exothermic process, therefore rising the temperature would lower the proportion of ammonia in the equilibrium mixture. That is, it favours a higher proportion of reactants N2 and H2.
To determine the proceeding of a reaction, the equilibrium constant for this reaction needs to be calculated. The constant k has a magnitude that provides a useful indication of the extent of a chemical reaction. A large value for K would indicate a high relative proportion of products to reactants whereas a low value for k would indicate that only a small fraction of reactants has been converted to products.

  • For the reaction: N2 (g) + 3H2 (g) = 2NH3 (g) the table below shows the variation values for the Equilibrium constant as a function for temperature.

Temperature (°C)
Keq
25
6.4x10−2
200
4.4 x 10−1
300
4.34 x 10−3
400
1.64 x 10−4
450
4.51 x 10−5
500
1.45 x 10−5
550
5.38 x 10−6
600
2.25 x 10−6

While increasing the temperature increases the reaction rate , according to Le Chatalier’s principle the forward reaction is not to be favoured if there is a rise in temperature therefore increasing temperature would decrease the yield of Ammonia. When the temperature is lowered the equilibrium position moves to the right. Since this is a exothermic reaction it produces more heat as energy is a product of the forward reaction, the reaction moving forward results in more product being formed therefore more ammonia gas would be produced. There needs to be a found balance between higher temperature (increasing rate of reaction) and lower temperature (increasing yield of Ammonia)

Increasing the pressure in this reaction would cause the equilibrium to move to the right which would result in a higher yield of ammonia considering there is more gas molecules present on the left side of equation. For every 4 moles of gases reacting, 2 moles of NH3 is produced. By increasing the pressure the system adjusts to reduce the effect of change. Here the pressure is reduced and the reaction mixture is forced into a smaller volume whereby the reaction is favoured by producing smaller number of moles of gas




Similar Processes


To compare and contrast similar processes to the Haber process we first have to evaluate the Haber process. The Haber process was invented by Fritz Haber; this was done by combing medium temperatures (500oC), very high pressures (50 atmospheres, 25,500kPa) and a catalyst. This process produced Ammonia yield of approximately 10-20%. Although the Haber process was invented by Fritz Haber it was developed into an industrial process by Carl Bosch. The reaction that is between Nitrogen gas and Hydrogen gas to produce Ammonia gas is an exothermic equilibrium reaction which releases 92.4 kJ/mol of energy at 298K (25oC).

There are many companies that engineer and construct technology for this and one of them is the KBR (Kellogg’s brown and root)

The Kellogg’s brown and root company is a leading supplier of ammonia process technologies. This company has a lot of processes for the synthesis of ammonia with high technologies in placement. Some of these are

KBR Advanced Ammonia Process Plus (KAAPplus™) – This process is a combination of the Top – Fired Steam Methane Reformer (SMR) with a KAAP Synthesis Converter. The auto thermal reformer that is present in this system (KAAPplus™) uses air instead of oxygen- enriched air. This is needed because the downstream purifier requires excess Nitrogen. An air separation unit is not need for the system. Then all excess Nitrogen, Methane and most of the Argon are removed from the syngas. This process also doesn’t need a separate purge gas recovery unit as the small synloop purge is recycled to the purifier. Lastly Ruthenium is used by the KAAP synthesis catalyst as the active ingredient on a highly-stabilized graphitic base material. This is 10 – 20 times more active than the traditional magnetite catalyst therefore enabling a lower synthesis loop pressure.

This Process would advantage the producer in many ways, some of them are:

  • Less space is needed as it replaces the large traditional and expensive primary reformer with a smaller , simpler and much more reliable equipment configuration
  • The use of low synthesis pressure allows the use of a single- barrel syngas compressor and reduced pipe- wall thickness; this reduces the overall plant capital cost.
  • The maintenance cost for this design are lower than the competing process designs as it uses the conventional magnetite ammonia synthesis catalyst
  • Lastly It provides more competitive energy consumption

The two main disadvantages of this process are that even though the maintenance cost for this design is lower than the competing process designs, the equipment used in the ammonia plant requires he most maintenance and secondly Ruthenium metal costs have varied significantly over the past ten years and also the cost of the initial charge of KAAP catalyst Is important to consider as it could economically disadvantage the producer.


Conventional Magnetite Ammonia Synthesis Process – This process is conducted using 2 different technologies. Firstly the process is a conventional steam – Methane reforming, this is a top fired steam Methane primary reformer which is operated at high pressures combined with a secondary reforming using the stoichiometric amount of process air which helps to efficiently convert natural gas to Hydrogen and Carbondioxide . Then for the convention Ammonia synthesis loops, a horizontal ammonia synthesis converter is used. This has a 2 or 3 reactor stave where each consists of a vertical downward flow in the magnetite catalyst beds. These may be arranged as two beds in parallel but this depends on the plant capacity. Maximum conversions and heat recovery intercoolers are also provided between reactors. The advantages of this process are that it optimizes energy consumption and it’s well established. Also because of the efficiency of the horizontal ammonia synthesis, consists of a basket that can be rolled out of the horizontal converter vessels to trucks, it avoids the need for scheduling erecting a heavy and expensive crane for periodic maintenance and there is a higher loop conversion. The disadvantages to the producer of this process would be the need for a big space for keeping the machines that require a lot of space ( e.g. the horizontal ammonia synthesis converter and the primary reformer) and unlike the other 2 this process is fairly older thus the waste disposal methods and quantity of the emissions is higher.


Purifier™ Ammonia Process- the Purifier is a combination of the “Mild reforming with excess air”, “KBR purifier “and Magnetite ammonia synthesis in a horizontal converter” are proprietary technologies that yields an extremely reliable, strong, low-energy plant. The cryogenic purification technology instantaneously removes impurities (i.e. Methane, Argon) from synthesis gas; this is done by washing it with excess Nitrogen while adjusting the Hydrogen to Nitrogen ratio to 3:1. The purifier in this process is a simple design that consists of 3 pieces of equipment; these are the feed/ effluent exchanger, a column with a built-in condenser and an expander. This process consists with more specific and advanced designs such as the exchanger which is a plate fin design and made of aluminium, a cryogenic column which operates in the range of minus 170°C to minus 200°C, an Integral condenser, which is a shell-and-tube design, a expander, which is a compact, low-speed unit that is attached to a generator to recover power. The horizontal ammonia synthesis is used here as well for conventional magnetite synthesis loops and the vertical Ammonia synthesis converter can be used as well which is the Magnetite ammonia synthesis converter in a vertical configuration.

The advantages of this process to the producer are that it provides a clean , dry makeup gas to the synthesis loop and simple and precise Hydrogen to Nitrogen ratio control , It has low energy consumption which enables higher loop conversions with low inerts , fuel consumption is reduced as well though mild reforming temperatures, the purifier has proven to operate at some of the lowest energy consumption and a recent figure shows an energy consumption of 6.5 Gcal/MT(ISBL, LHV basis). Capital costs are reduced as smaller synloop equipment can be used since very clean makeup gas is provided which lowers synthesis pressure, catalyst volume and purge rate

The producer achieves flexibility and stability as the reforming section doesn’t need to be tightly controlled to produce precise Hydrogen to Nitrogen ratio and production is maintained even in the event of catalyst deactivation upstream of the purifier. Lastly this process provides the producer with reliability as low reforming temperatures translate to lower stresses, which enables a longer life of the reformer tubes and also statistics show the numerous purifier plants have run 3-4 years without maintenance shutdown .

The disadvantages to the producer would be the space that is taken up by the machines as the bigger the machines are the more space it would take. Noise is also a factor, considering large machines are used, the producer would need to control noise pollution. And lastly gas emissions from the plant would still be released into the atmosphere even though they are in small amounts.






Environmental impact



Ammonia has both positive and negative impacts when it comes to how it effects our environment. Some of the positive impacts of ammonia to the environment are that:

  • When Ammonia is produced naturally, it is naturally decomposed too and does not add to the global greenhouse effect
  • A well-known substance in households is a solution called Sal ammonic; this is produced because Ammonia is readily soluble in water
  • Even the slightest traces of ammonia in the air can be perceived as the odour of ammonia has a high alerting effectwhich enables refrigerant leaks to be detected at once.
  • Ammonia improves biodiversity (soil life) and long – term productivity of soil. The benefits of this nitrogenous fertilizer Is obvious as it enables the crops to grow taller and are healthier therefore yielding a higher crop and thus cheaper which results in plentiful food.
  • Ammonia as a refrigerant is that it is the only refrigerant commonly used today that is environmentally safe. Ammonia very quickly “recycles “itself in the atmosphere.
  • It doesn’t react with your planets ozone layer therefore it doesn’t contribute to increased dangerous ultraviolet radiation and Ammonia is not a greenhouse gas that contributes to global warming.



The negative effects of Ammonia are categorized in three main categories which are water quality, soil and atmosphere.

Water quality covers 2 main problems that affect the water, they are:

  • Eutrophication – is the process whereby compounds rich in Nitrogen which are found in fertilizers and from sources such as sewage effluent run off in ponds or lakes, these are the primary causes of usually a pond or lake becoming over rich in organic and mineral nutrients which results in the rapid growth of algae and Cyanobacteria growing rapidly and depleting the Oxygen supply
  • Baby Blue syndrome – High application rates of inorganic nitrogen fertilizers in order to maximize crop yields when combined with fertilizers leads to a increase in run off into surface water and leaching into ground water. Since plants absorbs Ammonium ions preferably over nitrate ions the use of Ammonium Nitrate is damaging as the Nitrate ions that are not absorbed by rain or irrigation get runoff , therefore causing a spike in nitrate levels and if they are above 10ppm , it causes baby blue syndrome.

Soil has 3 common problems, which are:

  • Soil acidification – This can result when Nitrogen containing inorganic and organic fertilizers are added to the soil and may decrease in nutrient availability.
  • Toxic Organic pollutants – these are resistant to environmental degradation and because of this they have been observed to persist in the environment thus being capable of having significant impacts on the environment and human health, these are found in agricultural fertilizers e.g. (Dioxins, PCDDs)
  • Heavy metal accumulation –Steel industry wastes which are recycled into fertilizers for their high Zinc levels can contain metals like lead , Nickel but the most common toxic elements in this type of fertilizer are mercury and lead and these raise a concern as fish meal mercury content in many places e.g. Spain.

The Atmosphere suffers 2 main problems too when it comes to the environmental impact of ammonia as a product of the Haber process

  • Methane emissions from crop fields – These are increased by the application of ammonium based fertilizers and these contribute greatly to global climate change as Methane is a potent greenhouse gas.
  • Fertilizers using nitric acid or ammonium bicarbonate through which produces emissions of Nitrogen oxides, Carbon dioxide, Ammonia and Nitrous oxide gas which is the third most important greenhouse gas.

When comparing the Haber process to the Purifier™ Ammonia Process.The technology present makes the disposal of their wastes are far more efficient than the Haber process .The purifier reduces emissions of waste generated (CO₂ and NO), it also has a precise Hydrogen to Nitrogen ratio control which stabilizes the entire plant operation and because of its technological advancement over the Haber process The Purifier™ Ammonia Process far more efficient, environmentally friendly and has more than 50 years of experience and success, therefore showing the Purifier™ Ammonia Process to be less damaging and more benefiting better to the environment. The purifier also has a more increased ability to recycle or reclaim waste products.




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Haber Process; 2006, P1-1, 1p (Article)