OCR Text |
Show operational experience with the modified system is presented next. The operational experience relates to the period between June 1 through September 14, 1987 and includes a brief summary of various performance tests conducted on the system as well as a highlight of the major problems encountered during this operation. A trial burn was conducted in July and August, 1987, however, data from those tests has not, at the time of this writing, been fully evaluated and will be presented in a later paper. SYSTEM MODIFICATIONS As mentioned earlier, during the 1985-86 operation, the MIS had shown that only 2,000 1b/hr of soil with relatively low moisture content and low heating value could be incinerated. Higher moisture content or higher heating value feeds further reduced the system capacity. Also, a modest on-stream factor (45-55%) was experienced during this operation. Since the economics of the MIS are directly dependent on the system capacity and its on-stream factor, a design study was undertaken to determine the capacity-limiting factors and the primary causes of the system unavailability. Capacity: It was found that the capacity limitation of the MIS resulted primarily from: Volume of the ram feed trough which determined amount of material charged. Flue gas volumetric flow rate through SCC which approached the required minimum 2 second gas residence time. The first limitation was easily eliminated by ~ncreasing t~e volume of the ram feed trough from 0.5 ft to 1.2 ft . With the ram stroke frequency ranging from 1 to 1.5 strokes pe3 minute, the feed system now has a maximum capacity of 108 ft /h3. For a soil with density of approximately 70 1b/ft and the normally used ram stroke rate at 1 stroke per minute, the feed system can push approximately 5,000 1b/hr of soil into the kiln. In order to overcome the second limitation, the conventional air burners in the kiln were replAced by an oxygen-enrichment type burner system. The Lind~ "A" Burner System (from Union Carbide) was selected as a replacement for one of the two existing air burners. The "A" burner uses 100% oxygen and, thereby partially eliminates the nitrogen portion of the combustion air required for incineration. In the MIS, the see still uses conventional air burners. Use of oxygen instead of air reduces the volume of nitrogen and flue gas in the system |