OCR Text |
Show 11 Half Cycle Time (sec) 15 30 50 ' F.G' * APH CO 19-27 35-55 55-65 Temperature Efficiency CO 0.97-0.98 0.94-0.96 0.93-0.94 Table 1. The effect of cycle time on temperature efficiency Destruction of V O C by rotary combustion system Combustion is always taken as an irreversible reaction, and since most V O C concentration in process exhaust is extremely low, the reaction can be considered to be first-order with respect to concentration. For a given inlet combustion exhaust temperature with an assumption of the combustion chamber is a rback mixed j type, steady-state conditions occur at the intersections of the energy balance line (Q„) with the S-shaped material balance (Q,) for a residence time in the combustion chamber, as shown in Fig.9 described elsewhere (12,13) . The lower steady-state region is called the oxidation region has a lower reaction rate, whereas the upper steady region is known as the combustion region has much faster reaction rate (14) . Tma, = qQ/Cp + T, (Eq2) The shift of the energy balance line varies with the preheating temperature (T,) and inlet concentration of the combustible (C;) in the process exhaust. In this presentation, CF is always very small, thus reaching the flame temperature is highly depends on Tj in addition to fire supplement fuel, based on Eq(2), whereas heating value(q) and specific heat (Cp) of the inlet are taken as constants. From the sketch of Fig.9, if the preheated gas temperature is at T=T,, T2 is called ignition temperature but unstable. When the inlet temperature is preheated up to T=TB, Q„ and Q, intersect each other tangentially at B, TB is called ignition temperature, and this phenomena is called thermal explosion as shown in Fig.9, the reaction rate increases by order of magnitude since then. On the other hand, as the inlet temperature is reduced, the Q„ line is shifted to |