Process for ammonia production

Abstract

A process for the synthesis of ammonia from a make-up gas containing hydrogen and nitrogen, comprising at least two steps for the synthesis of ammonia, wherein: said reactive steps are performed in series and each of said reactive steps provides an ammonia-containing product gas; the second and any subsequent reactive step receives, as a feed stream,at least a portion of the product gas of the previous reactive step;an intermediate adsorptive step of ammonia is performed between consecutive reactive steps, so that the product gas of each step is depleted of ammonia prior to the subsequent reactive step of said series.

Description

technical field [0001] The present invention relates to a process for the production of ammonia by catalytic conversion of supplemental synthesis gas. Background technique [0002] The industrial production of ammonia involves the catalytic conversion of synthesis gas ("make-up gas") comprising hydrogen and nitrogen in a synthesis loop according to the following reaction: [0003] [0004] High equilibrium ammonia concentrations can be achieved at high pressure and low temperature. [0005] However, due to technical and economic constraints, industrial ammonia production is carried out at temperatures above 350°C (which ensures that the catalyst is active) and at pressures below 200 bar, thus resulting in lower equilibrium ammonia concentrations. [0006] An unfavorable reaction equilibrium limits the achievable ammonia concentrations under practical conditions to about 20 mole percent or less, which corresponds to a conversion per pass of less than 30 percent. [0007]...

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Problems solved by technology

In addition, corrosion phenomena (e.g. attack from nitrogen and hydrogen) are more severe at higher temperatures

Therefore, the pressure vessel would require expensive materials such as stainless steel or Inconel to withstand these conditions, and would require complex mechanical designs to protect the pressure vessel from high temperatures (such as flushing or barrel insulation)

[0021] In addition, the aforementioned mixed bed containing sorbent and catalyst must withstand both the high temperatures reached by the reaction and the temperature / pressure cycles used for sorbent regeneration, thus causing significant mechanical stress

Also, the simultaneous presence of both materials results in an increase in the size of the pressure vessel

[0022] Parallel adsorption and reaction forces the use of higher adsorption temperatures (i.e. at least 400 °C to ensure that the catalyst is active), which reduces the adsorption capacity of the adsorbent and further increases the required vessel size

[0023] Furthermore, for a continuous process, multiple vessels are required, and furthermore, as mentioned above, these vessels are large and expensive

[0024] Finally, due to the high temperature, the heat of reaction cannot be fully recovered and quenching with cold feed gas will be required

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