Lurgi coal feeding

Coal-Based Partial Oxidation Processes Two commercially establislied processes utilising coal feeds are the Lurgi process (32) and the Koppers-Tot2ek process (33) the process schemes are shown ia Figures 6 and 7, respectively. 

If these two figures are compared with the coal feeding rate for the LURGI dry-bottom gasifier in line one of Table 1.13 and with the total coal demand in the last line methanol efficiency), it can be seen that the ratio between the total coal demand and the gasifier coal demand is approximately 1.25, i.e. almost the same as the above ratio of 1.18. One may th fore conclude that the simplified look at methanol efficiency is accurate enough to assess different types of coal. 

Similar to the Lurgi FBDB process, the control of the BGL gasifier is comparatively easy Care must be taken to keep the reactor full of coal, which is enough for 0.5-1 h of operation or on a constant level in the case of short-bed operation. As coal feeding is accomplished automatically, only the gasifying agent quantity and composition remain to be controlled. 

Low Temperature Carbonization. The Lurgi Sptlgas process was developed to carbonize brown coal at relatively low temperatures to produce tars and oils (Fig. 5). A shaft furnace internally heated by process-derived fuel gas (Spblgas) is used. The product can range from a friable coke breeze to hard lump coal depending on the quality of the briquettes used in the feed. The briquettes, made in normal extmsion presses, break down into smaller sizes during carbonization. 

The feed stocks include naphtha, natural gas liquids, propane and butane. The cost of SNG gas from these plants is as high as 5 to 6 per Mcf. The investment cost is very low for this type of SNG plant and is on the order of 522 per million Btu per day of capacity at a 50% load factor. This can be compared with the investment cost of high-Btu pipeline-gas-from-coal plants which is now on the order of 12,444 per million Btu per day of capacity based on the Lurgi process and 90% load factor. There are two other SNG plants in the planning or construction stage. 

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