TUTORIAL: Set operation and Mixer

Problem: Natural gas and steam must be mixed at specific proportion before being sent to a Methane

Steam Reforming Reactor. This is an important process to produce hydrogen necessary for several

refining facilities such as the hydrotreating unit. Due to several problems due to coke formation in the

reforming reactor, you need to be careful and precise with which proportion you will feed the reactor.

To avoid coke formation, you have been told to maintain the steam-to-methane ratio at 3:1. It is

possible that you are going to adjust the natural gas flow, but by doing it you will need to regulate flow

of steam as well depending on the situation. Fortunately, you use the set operation to make any

modification in the ratio and further calculations are automatically done by using the set operation. In

this tutorial, we are going to learn how to use the set operation and the mixer unit to obtain the

reactor feed properties.

Solution:

1-) Open the ASPEN Hysys. Add Methane and Water as components in Components List. Then, add

Peng-Robinson EoS in Fluid Package.

2) Click in Simulation to open the Simulation Environment

3-) Add two material streams. Lets assume that natural gas is only composed of methane. Hence, the

first stream is going to be called methane and the second one steam. Specify the both stream as

follows.

4-)Place the set operation by clicking on Cn(A) on the Palette.

5-) Double-click on SET-1. For Target variable select Steam as object and Variable as Molar flow. For

source, select Methane. Obs: A consistency error will appear because the default multiplier in the SET

is 1, and you previously set 3 lbmol/hr when specifying the steam stream.

6-)In parameters tag, set the multiplier as 3, and the procedure will be completed. Obs: After you

closed the consistency error window, HYSYS put the simulation on hold, Click on Active to make hysys

calculate the stream flow rates. Also, double click on the Steam stream and delete the value of Molar

flow rate

7-) Select the mixer in the object palette and place it on the simulation environment

8-)Double-clicking on the MIX-100. Select as inlets Methane and Steam. In Outlet type Reactor Feed

to automatically create the Reaction Feed.

9-)Double-Click on Reactor Feed to see the specification calculated by hysys in the mixer outlet. You

can change the proportions to see how the set operation and mixer work.