The ammonia process utilizes water for the generation of steam and natural gas as a feedstock and as a fuel. As a result of the process, carbon dioxide is produced as a by-product and process condensate is generated as a wastewater stream. The ammonia plant was originally equipped with a wastewater holding pond, an injection well, and an irrigation field for collecting and disposing the process condensate, run off, and other wastewater streams. The injection well was designed to dispose of 90-95% of the wastewater streams and the balance by evaporation at the irrigation field. Cominco American Incorporated procured the engineering services of the M.W. Kellogg Company to provide a design for the ammonia plant and lower fuel and make-up water consumption. In early October, 1989, a major construction phase was initiated and completed by early December, 1989.
The original primary reformer catalyst tubes were removed and new tubes constructed of an improved metallurgy were installed. The improved metallurgy has a higher strength and as a result thinner wall-thickness catalyst tubes were utilized. This has resulted in reduced fuel consumption per ton of ammonia produced. The original convection section and heating coil modules were removed and a new convection section with new heating coil modules were installed to reduce heat losses and increase heat transfer. The results have been lower NOX emissions, and a lower fuel consumption. The original four catalyst bed radial ammonia converter reactor was modified "in-situ" to an axial-radial three catalyst bed reactor with an inner cooler. The existing internals were removed and the new internals were installed, leaving the outer shell intact. This design has resulted in lower pressure drop and improved conversion of hydrogen and nitrogen through the catalyst beds. In conjunction with the reactor modification, a new and more efficient synthesis compressor and steam turbine were installed to lower steam consumption per horsepower delivered. As a result, the fuel consumption has been reduced. A water saturator coil was installed as part of the new convection section. As part of the saturator coil, a saturator knock-out tank and two related pumps were nstalled. This has resulted in recovering wastewater for conversion to steam and reduced make-up water and fuel consumption.
The efficiency of the plant has been improved with a lowering of the consumption of natural gas as fuel by 22%. Fresh make-up water has been reduced and 95% of the process condensate that was discarded as waste is now recovered. The emission rates of NOx have been reduced by 35%. This is a summary of our project and as noted, significant improvements and reductions in the areas of energy consumption, disposal costs, waste minimization, and environmental pollution have been realized.
Details of Reductions
Additional Information :
One of the largest savings realized from this project has been in reduced energy (natural gas) consumption. Over the period since the project was completed (1990 thru 1993), energy savings have averaged 1,000,000+ MMBtu/year. This is equivalent to approximately 1,000,000,000 cubic feet of natural gas per year. This translates into over $1,700,000/year savings. Another significant savings has been in reduced water consumption within the process due to the recovery of water previously disposed of as waste. Our water is purchased from the City of Borger, and savings of over 110,000,000 gallons per year have been realized due to decreased consumption over the 1990 thru 1993 period. This is equivalent to over $65,000 per year savings. Other significant savings include reduced disposal costs of wastewater into our injection wells. Plant reliability has been improved dramatically and production totals for each year since the project was completed have been well above any other years in the history of the plant. Other benefits include reduced NOX and CO2 emissions from our reformer due to decreased firing of fuel gas.