ammonia_reactor.tex

\documentclass[tikz]{standalone}
\begin{document}

\tikzstyle{unit} = [
    draw, minimum height = 2cm, minimum width = 4cm, fill=yellow!40,
    rectangle, rounded corners, text centered]

\begin{tikzpicture}[auto]
  %  \draw[help lines] (0,0) grid (10,2);
    \draw (0,0) {};
    \draw (10,2) {};
    \draw (5.5,1) node [unit] (reactor) {$N_{2}+3\, H_{2}\rightleftharpoons2\, NH_{3}$};
    \draw [->] (0,1.5)--(3.5,1.5) node [above,midway]
               {$\dot{n}_{N_2}=1000\frac{\mbox{g-mol}}{\mbox{hr}}$};
    \draw [->] (0,0.5)--(3.5,0.5) node [above,midway]
               {$\dot{n}_{H_2}=3000\frac{\mbox{g-mol}}{\mbox{hr}}$};
    \draw [->] (7.5,1.0)--(10,1) node [above,midway]
               {$\dot{n}_{N_2}$,$\dot{n}_{H_2}$,$\dot{n}_{NH_3}$};
\end{tikzpicture}

\end{document}