the cooling jackets 20 connected in series the inlet 24 of the topmost jacket 21 is connected to the heat exchanger outlet 5 by inlet hose 36 and the outlet 26 of the topmost jacket is connected to the inlet 24 of the next highest jacket 20 this is repeated for all the jackets 20 of the vessel 10 except that the outlet 26 of the lowermost jacket 23 is connected to the heat exchanger inlet 7 a pump 8 located on hose 36 circulates coolant through the system another embodiment of the invention is shown in fig5 an integral cooling jacket 40 in the shape of a u shaped annular channel whose open side abuts the shrink ring 18 can be used an o ring gasket 42 fits within a recess 44 in each leg 45 of the integral cooling jacket 40 to provide a leak proof seal between the cooling jacket and the adjacent shrink ring 18 the integral cooling jacket 40 is of a diameter such that it can be press fitted about the shrink ring 18 the stress liner 14 cover plate 16 and shrink rings 18 can be made from high strength steel the cooling jackets 20 and couplings 30 can be made from a corrosion resistant alloy steel the hoses 28 can be made from a corrosion resistant flexible material the o ring gaskets 42 can be made from a heat resistant flexible material as the temperature and or pressure of the atmosphere within the vessel 10 increases pressure is exerted against the stress liner 14 and cover plate 16 the forces exerted against the cover plates 16 are transmitted to the reaction frame 12 which holds the cover.