Ammonia synthesis flowsheet

We first considered applications of this approach within process engineering. Steady-state flowsheeting or simulation tools are the workhorse for most process design studies the application of simultaneous optimization strategies has allowed optimization of these designs to be performed within an order of magnitude of the effort required for the simulation problem. An application of this strategy to an ammonia synthesis process was presented. Currently, flowsheet optimization is widely available commercially and has also been installed on the FLOWTRAN simulator for academic use. 

Fig. 7.7. Flowsheet for the production of hydrogen from methane for ammonia synthesis and fuel cell applications indicating the potential for rationalization using an adsorptive reactor.

FIGURE I 1.4 Simplified flowsheet of the gas recycle and product recovery systems for ammonia synthesis, from the gas mixture leaving the converter. 

Consider the two-stage ammonia synthesis loop shown in Figure 2.31. In the flowsheet, a cold stoichiometric feed of N2 and H2 is introduced between the... 

Pig. 7.3 Flowsheet of high-pressure test for performance evaluation of ammonia synthesis catalyst... 

Since the first commercial application of the Haber process for ammonia production in 1913, a wide variety of synthesis loop designs have been developed. A history of the early developments is given in Chapter 1, and has also been reviewed elsewhere. However, by the 1950s and early 1960s, a broad consensus about the optimum design conditions for an ammonia synthesis loop had been reached. A typical design from this period will be described. This will be used to demonstrate how the elements of the synthesis loop are applied to produce a practical design, and will also serve as a base case for the discussion of modern developments. A flowsheet for this type of synthesis loop is shown in Fig. 7.4. 

The simplified flowsheet of the coupled synthesis gas and ammonia plant is shown in Fig. 1. The streams are numbered from 1 to UU and are listed in Table I and Table II Table I refers to the reactant and product streams especially. The units of the process may be identified by Table III. 

Figure 1. Synthesis gas and ammonia plant (simplified flowsheet)...

In all of these alternatives, the design team selects acceptable temperature levels and flow rates of the recirculating fluids. These are usually limited by the rates of reaction, and especially the need to avoid thermal runaway or catalyst deterioration, as well as the materials (rf construction and the temperature levels of the available cold process streams and utilities, such as cooling water. It is common to assign temperatures on the basis of these factors earily in process synthesis. However, as optimization strategies are perfected, temperature levels are varied within bounds. See Chapters 10 and 18 for discussions of the use of optimization in process synthesis and optimization of process flowsheets, as well as Example 6.3 to see how constrained optimization is applied to design an ammonia cold-shot converter. 

---