Advanced steam-cracking and cryogenic recovery process to produce polymer-grade ethylene and propylene, butadiene-rich mixed C4s, aromatic-rich pyrolysis gasoline, hydrogen and fuel streams. Cracking feedstocks range from ethane through vacuum gasoils.
The proprietary Selective Cracking Optimum REcovery (SCORE) olefins process combines the technologies, know-how and expertise of a major engineer designer, Kellogg Brown & Root (KBR) and one of the world’s largest ethylene producers, ExxonMobil Chemical Co. KBR is the only licensor with a long-term, worldwide licensing agreement with such an ethylene producer. Through the efforts of both companies, the result is an innovative and differentiated technology backed by extensive ethylene operating experience to further improve operability and reliability, and reduce production costs.
The SCORE pyrolysis furnace features a single straight radiant-tube design with feed entering the bottom and cracked gas leaving the top of the furnace. This results in the lowest practical reaction time (~0.1 seconds) in the industry and low operating pressures. At these conditions, olefins yields are the highest that can be commercially attained.
For today’s large-scale ethylene plants, this yield advantage translates to over $30 million per year additional gross revenues. Additional features such as hybrid cracking, online decoking and ultra low-NOx burners all combine to make the SCORE furnace safe, flexible, cost-effective and environmentally friendly. An optimized KBR design can eliminate an incremental furnace, thereby saving up to $30 million in capital costs.
The recovery section is based on a front-end acetylene reactor design pioneered by KBR. This feature, combined with integration of fractionators with the major compressors leads to a design with a lower equipment count and capital cost. Such integration also leads to a plant that is easy to operate with lower maintenance, yet highly competitive with regard to energy due to low-pressure operation. Because of these features and the higher olefins selectivity from cracking operations leading to lower overall plant throughput, recovery section capital cost is reduced significantly by tens of millions of dollars.
The pyrolysis furnace (1) cracks the feed hydrocarbon in the presence of dilution steam into large amounts of ethylene, propylene and byproducts. The furnace effluent is cooled by generating steam (2) and quenched further (3–5) to remove heavy gasoline (7), fuel oil and dilution steam. The cooled process gas is compressed (6), caustic-washed (8) and dried (9). The first fractionator is typically a deethanizer for lightgas feeds or a depropanizer for heavier feeds. Both schemes were pioneered by KBR and share common attributes leading to low cost and energy. The example which follows is for a depropanizer-first scheme. The depropanizer (10) is heat pumped by the last stage of the cracked-gas compressor (6). The acetylene in the depropanizer overhead is hydrogenated in an acetylene reactor (11), and the C3 and lighter stream is sent to the demethanizer system (12–14) to separate methane and lighter fraction from the mixed C2/C3 stream. The demethanizer (13) bottoms C2/C3 stream is sent to the deethanizer (15), which is integrated with the heat-pumped C2 splitter (16) and C2 refrigeration compressor (17) in a patented design to save both energy and capital. The C2 splitter is operated at low pressure to produce ethylene product and ethane recycle. The deethanizer bottoms (mixed C3 stream) flows to the C3 splitter (18) where propylene is recovered and propane recycled. The depropanizer bottoms product (C4+ stream) flows to the debutanizer (19) for recovery of the mixed C4 product and aromatic-rich pyrolysis gasoline.
Yields: Ethylene yields to 84% for ethane, 38% for naphtha and 32% for gasoils may be achieved depending upon feedstock character.
Energy: Overall specific energy per ton of ethylene range from 3,000 kcal/kg to 6,000 kcal/kg, depending on feed type and battery limit conditions.
Licensor: Kellogg Brown & Root LLC