KBR Advanced Ammonia Process (KAAP™) Commercial Applications The KBR Advanced Ammonia Process (KAAP™ Process) flow sheet combines a conventional reforming front end using KBR's proven Top-Fired Steam Methane Reformer (SMR) with KBR's proprietary KAAP™ Ammonia Synthesis Loop.
Proven Process Technology KAAP™ technology has been licensed for five commercially-successful grass roots ammonia plants operating in Trinidad, each with a nameplate capacity of 1850 MTPD, A sixth KAAP™ plant with a nameplate capacity of 2000 MTPD commissioned in Egypt the first quarter of 2009, and a seventh 1800 MTPD KAAP plant is under construction in Venezuela commissioned in 2010. The first two grass roots KAAP™ ammonia plants in Trinidad have been operating successfully since 1998.
YEAR
CLIENT
LOCATION
CAPACITY (MT/Day)
1998 1998 2002 2004 2008 2009 2010
PCS Nitrogen Point Lisas Nitrogen Ltd. Caribbean Nitrogen Co. Nitrogen 2000 EBIC MHTL Pequiven
Trinidad Trinidad Trinidad Trinidad Egypt Trinidad Venezuela
1850 1850 1850 1850 2000 1850 1800
Values and Benefits KAAP features ammonia synthesis over a proprietary promoted Ruthenium on graphite catalyst that has an intrinsic activity ten to twenty times higher than conventional magnetite catalyst. This wellproven catalyst allows efficient ammonia synthesis at only 90 bar syn bar syn loop pressure which is twothird to one half the operating pressure required for conventional ammonia synthesis. As a result of this low pressure, only a single-case synthesis gas compressor is needed and vessel and pipe wall thicknesses are reduced throughout the synthesis loop, which reduces design complexity and equipment costs.
KAAP RUTHENIUM CONVERTER 4-Bed Radial-flow Converter (GRASSROOTS) The Grasroots ammonia plants typically utilize KAAP in conjunction with KRES, the Kellogg Reforming Exchange System. Together, these processes have a multitude of benefits, several of which stem from the sole implementation of KAAP. The lower pressure synthesis loop, which leads to significant capital savings, results from the use of a single case gas compressor with thinner walled and lighter vessels, fittings, and pipings. This synthesis loop is also advantageous in that it uses energy more efficiently by recovering heat at a much higher temperature, yielding a 40% decrease in energy conversion relative to conventional designs. Since the synthesis loop is less complex than in other plants, operator attention is expected to be less as well. In addition, all of these benefits bring with them an expectation of greater reliability. The synthesis proceeds at about 90 bars in a 4-bed radial-flow converter (hot wall design) with interbed exchangers. The first bed is charged with conventional iron-based catalyst for bulk conversion and the other beds with Kellogg’s high activity ruthenium-based catalyst, allowing to attain an exit ammonia concentration in excess of 20%. The other process steps are more along the traditional lines. The overall energy claimed for this process can be as low as 27.2 GJ/t NH3 (6.5 Gcal/t NH3).
ITEMS Production capacity (T/day) Temperature rising of converter (dT/ oC) Ammonia concentration at outlet (mole%)
DESIGN 1850 262 20
ACTUAL 1918 286 21.7
2-Bed Radial-flow Converter (RETROFIT) The KAAP system was successfully started up in November of 1992. It consisted of a KAAP reactor which was installed downstream from the magnetite converter already in existence. This KAAP reactor was a two-bed radial flow converter with a unique proprietary sealing system which avoided hot spots within the catalyst bed. The KAAP catalyst was loaded in its oxidized state, just as most catalysts are, although it is only active in the reduced state. A continuous purge is required in this retrofit because the expanded plant contains more inerts than in the original synloop. After the entire KAAP retrofit was completed, PAI had an energy savings of 0.6 mmBTU/mt. This more efficient and highly flexible system has been very easy to operate and has paved the way for grassroots facilities. The two-bed, hot-wall KAAP reactor features a low pressure drop and radial flow. Because of the KAAP catalyst's high activity, thin beds are necessary to keep operating temperatures within the prescribed range. Kellogg's reactor uses a proprietary sealing system. This technology avoids the catalyst mal-distribution that can lead to formation of hot spots in the catalyst bed. The system also enables 100% of the loaded catalyst volume to be utilized for reaction. The stream enters the reactor through a side inlet and is heated in the internal exchanger tubes. An external bypass line around this exchanger provides first-bed inlet temperature control. The gas flows through the first bed, then on to the shell side of the internal exchanger and to the second bed. The effluent from the second bed of KAAP catalyst is about 19% ammonia. The effluent is cooled in a second medium-pressure steam generator. It then flows to the shell side of the feed/effluent exchanger (121-C). Shell-side effluent from this exchanger is cooled in a water exchanger (124-C), where ammonia condensation begins. A four-stage "unitized" exchanger completes the condensation process. The ammonia is cooled to -33° C. in a two-case, centrifugal compressor. The refrigerated liquid is then removed and sent to storage.
RUTHENIUM CATALYST - SIGNIFICANT FEATURES In 1979, a novel catalyst for ammonia synthesis was prepared by loading carbonyl compound of ruthenium on carbon containing graphite in laboratory. This kind of catalyst, with graphited carbon as support and Ru3(CO)12 as precursor, possessed some special features that may be summarized as follows: 1. High activity (more than 10-20 times than magnetite) and at high ammonia concentrations: Outlet ammonia of reactor may be 20% - 21.7% at 91.4 kg/cm2. 2. Low temperature initiation, low pressure performance. 3. Expected catalyst life is the same as for magnetite, and is determined by loss of carbon support. 4. Poisons are the same as for magnetite and to approximately the same degree. Catalysts recover after temporary poisons (H2O, O2, CO, CO2) are removed. 5. Like iron (magnetite) catalyst, dissociative adsorption of N2 is also the rate determining step on ruthenium catalyst. The difference is that the absorption of H 2 strongly inhibits the adsorption of N2, while the inhibition effect for NH3 production is not apparent on ruthenium catalyst. 6. The latter is an advantage of ruthenium catalyst, so that the ruthenium catalyst can be placed behind iron catalyst in synthesis ammonia process e.g. KAAP process. 7. When H2 /N2 = 3, ruthenium catalyst exhibits the higher activity than the iron catalyst at high temperatures. In addition, the situation is opposite with the increase of H2 /N2 ratio. Thus, ruthenium catalyst is suitable for use at low H2 /N2. 8. Since ruthenium catalyst is expensive, highly active and readily inhibited by H2, the process for the ammonia synthesis must be modified to fit these features.
