Large Volume Inorganic Chemicals - Ammonia ... - ammk-rks.net

Chapter 4Two general converter types have been in use extensively in the past:• the brick-arch support and• the cast iron beams and columns design (still very popular in North America).Newer converter types are:• central core tube converters• converters with one or more integrated heat exchangers (with the heat exchanger placed inthe core tube or “wrapped” around the outer shell of the converter vessel).In conventional converters, the shell is generally made of boiler quality steel, with internal bricklining and mostly additional aluminium spraying to protect the material from scaling. A greatadvantage of the brick lined vessel is its high heat capacity, which enables long shutdown timeswithout preheating. The disadvantage is that older brick-arches can be porous and, hence,process gas partially bypasses the intermediate absorber (see also Section 4.4.6 “Replacement ofbrick-arch converters”).Newer converter designs are made of the 304 or 321 type stainless steel to ensure long termstability. The higher cost of stainless steel is compensated by less weight, simply through athinner wall thickness. Figure 4.4 illustrates the design of brick-arch and core tube converters.Catalyst bed 1Catalyst bed 2Catalyst bed 3Catalyst bed 4Figure 4.4: Schematic of a brick-arch converter (left) and a core tube converter (right)These figures are based on [67, Daum, 2000]152 Large Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers