How to reduce the heat from diesel exchaust gas

[Rapid Pulse]

I am building a Rapid Pulse Carbonation prototype Reactor unit, I am capturing the Steam form the process and passing it though a Plate and Tube condenser to produce water, also I will capture the CO2 gas from the heating system. How would I reduce the exhaust gas heat before I pass the exhaust gases into my Sodium Hydroxide solution

 

[Nidum]

You'll have to explain what you are doing more clearly before anyone can give you a sensible answer .

 

[Rapid Pulse]

The carbonisation reactor needs to be heated to 500C at a pressure of 10 bar...the system is zero emmissions and zero waste..to heat the reactor to the 500C i need to use either 1 or 2 diesel burners ...but i want to capture the CO2 gases which are hot...these exchaust gases need to go to a sodium hydroxide tank which captures the CO2 and converts to sodium bicarbonate ...i need to cool the gases before they enter the sodium hydroxide solution...the exchaust pipe may be around 3" / 75mm dia what cooling chamber would i need ..keeping in mind that the housing for this RPC system is 6mt x 2.4mt

 

[Baluncore]

How would I reduce the exhaust gas heat before I pass the exhaust gases into my Sodium Hydroxide solution

Use a counter-current heat exchanger to cool the exhaust by preheating the induction air to the burners. Consider a coaxial tube for the exhaust and air input.
https://en.wikipedia.org/wiki/Countercurrent_exchange