A first fuel addition valve disposed in a portion of a first exhaust passage upstream from a first upstream purification device, a first urea addition valve disposed in a portion of the first exhaust passage between the first upstream purification device and a first downstream purification device, and a first valve cooling passage configured such that i) refrigerant passes the first urea addition valve and the first fuel addition valve in order, and ii) the refrigerant cools the first fuel addition valve after the refrigerant cools the first urea addition valve.