TREACT is the temperature for which the chemical equilibrium for the reaction in a reactor (combustor, gasifier, reformer or other reactor) is calculated. Chemical equilibrium is calculated using minimisation of Gibbs free enthalpy.
The value of TREACT can be specified independent of the calculated outlet-temperature for the combustor (or gasifier or other reactor). If no TREACT is specified, for default the outlet-temperature is taken.
The model of the combustor (or better: reactors) in Cycle-Tempo is planned to be adiabatic. But in practice heat transfer can occur during combustion, for example the firing place of a (steam-) boiler, where the firing-place is surrounded by the evaporator-pipe-walls. In the Cycle-Tempo model the evaporator is placed down-stream of the combustor. For this situation it is realistic to specify a lower temperature for TREACT. A reasonable value is the flue-gas-temperature at outlet of the evaporator is 1000 – 1100°C.

The effect of the temperature is also depending on other factors.
For high values of LAMBDA (meaning lots of excess-air), like in gas-turbine-combustors, in general full combustion is found, except for very high values of TREACT. The influence of PREACT and TREACT is not very strong.
In case of stoichiometric combustion the effect is relatively high. For high values of TREACT no full combustion is found, but H, CO and O is found in the product gas. This can even happen for values for TREACT > 500°C
In under-stoichiometric combustion, like in gasification, the composition of the product-gas is strongly dependent on PREACT and TREACT.

It is not possible to specify the outlet-composition of the gas (to fulfil the mole-balance), but by choices for PREACT and TREACT the composition can be influenced, especially for under-stoichiometric conditions.
In case some components are not fully combusted, for example in case coal or biomass is used, the combustor and gasifier offer the option to bypass a part of some of the fuel-components, provided that the component is available in the specification of the fuel-composition.

Example: in experiments for gasification of coal some carbon and methane is formed, but this is not the case in the Cycle-Tempo-calculation.
Carbon will always be specified for coal and biomass in the fuel-composition, so it is not expected to be a problem to bypass some of the carbon. To find CH4 in the product gas in this case some carbon (C) and hydrogen (H) in the fuel can be specified as methane (CH4) (for example 12 gram of C plus 4 gram of H to form 16 gram of CH4). If enough methane is specified it is possible to bypass the required CH4, so methane can be found in the product gas.