Sinopec Yangzi Petrochemical Co Ltd, China
China as a whole is a hotbed of construction projects related to the basic chemicals and petrochemicals industry. The Chinese are trying to develop their domestic capacity to manufacture raw materials for the burgeoning economy so that they do not have to rely on raw materials from foreign sources. They have developed supplies of oil and gas via agreements with several countries and are now putting together the infrastructure to make use of it.
One of the latest projects is a synthesis gas plant being constructed for the Sinopec Yangzi Petrochemical Company (YPC) in the Nanjing region of China.
In August 2007 Technip in Paris was awarded the basic design and engineering contract by YPC for the new syn gas plant. The contract will be undertaken by the company's operations and engineering centre in Zoetermeer in the Netherlands.
The new plant will have production capacities of 25,000m³/h of carbon monoxide (CO), 16,000m³/h of oxo gas and 59,000m³/h of hydrogen.
Oxo gas is a mixture of hydrogen and carbon monoxide which, when reacted with a suitable olefin, produces a range of oxo-alcohols that are used in the fabrication of polymers and detergents.
The new plant will use Technip's proprietary reformer technology and also Air Products proprietary cryogenic CO purification technology. Air Products will supply cold box equipment that produces separate streams of carbon monoxide and hydrogen from the syn gas stream produced. The detailed engineering, procurement and construction will be carried out by the customer YPC with suitable support and project management services from Technip.
The plant construction started in late 2007 and it is scheduled to be completed and on-stream in the first half of 2009.
Technip has worked with YPC before on a syn gas project. The first one came on-stream in 2005 in the Integrated Chemical Complex Nanjing. This was a 50/50 joint venture between BASF and YPC.
SEPARATION OF CO AND HYDROGEN
While syn gas is a valuable commodity for the synthesis of a wide range of chemicals (ammonia, methanol or synthetic gasoline) there is also a need for the separation into its component gases to a higher purity to achieve hydrogen and carbon monoxide (production of acetic acid, formic acid, polyurethane, polycarbonates and methylacrylates) at 99.8% purity.
The new plant will use Air Products cryogenic separation technology. This will involve partial condensation and also liquid methane scrubbing to achieve the pure gases.
Firstly the gas stream needs to be free of water and carbon dioxide, as these components could freeze and condense out in the process unit. The process gas mixture is purified by passing through a molecular sieve absorber.
Depending on the constituents of the feed gas a purification process is chosen. Gas from partial oxidation will have a high CO level and can use the condensation process.
However, gas streams from steam reforming have low CO and high methane and in these cases a methanol wash is used.
The condensation process includes an adsorber station, a coldbox with a plate fin heat exchanger to precool the feed gas against product streams, the hydrogen separator and a stripping column. The carbon monoxide compressor used would be a dry piston or integrally geared centrifugal compressor.