Here it is! One of the neatest things we have done yet, our batch pre-heater/ heat exchanger. You can see in the photo an elbow comes directly off of the flue. It then attaches to a T that we made with two butterfly valves inside. With those in place we can direct heat to either the batch box, heat exchanger, or both at the same time!! Craziness! The largest diameter horizontal cylinder is the heat exchanger. It has two pipes coming in and out of it that circulate glycol. To and from a heat storage tank down in the bio-diesel area.