“Propylene is a basic building block for the chemical industry and is used to produce a variety of products including plastics and solvents. The major source of propylene is steam cracker or fluid catalytic cracking unit (FCCU), normally as a second product. Constant growing propylene need with limited propylene supply from traditional resource has created an imbalance of supply and demand for propylene. Nowadays a shift to lighter steam cracker feedstocks with relatively lower propylene yields in certain areas has further enlarged this imbalance, thus on-purpose production methods such as propane dehydrogenation is increasing significantly.
What is propane dehydrogenation?
The propane dehydrogenation process, known as PDH, is used to produce high yield polymer-grade propylene through converting propane into propylene in the presence of a catalyst under high temperature, to meet the growing propylene market, independent of a steam cracker or FCC unit. It provides a dedicated, reliable source of propylene to give more control over propylene feedstock costs. Thus PDH technology has very bright future in areas rich in propane or short in propylene.
What are these areas?
Currently, the demand for propylene in Asia is growing very fast, mainly due to the rapid increasing demand of its downstream product polypropylene. China’s propylene consumption accounts for more than 15% of worldwide demand and is growing at around 5% to 6% per year. PDH technology has been constantly improved, lowering the investment and operation cost with the result that the use of PDH technology is constantly growing in China.
The feedstock represents a large portion of the total PDH production cost. PDH economics are largely dependent on the price differential between propane and propylene. Thus PDH technology has been used extensively in the Middle-East where there is an abundance of propane from oil gas operations.
These years natural gas offerings in the USA are significantly increasing due to the rising exploitation of shale gas, propane prices are decreasing accordingly. Chemical companies have already begun to establish PDH plants in the USA to take advantage of the low price raw material which comes from shale gas. Same situation might happen in other areas rich in shale gas such as China, Argentina, Canada, etc.
Numerous propane dehydrogenation plants are currently under construction around the world to relieve propylene shortfalls. And these new coming plants tend to be on a large scale, such as one plant producing 600,000 tons or even more annually.
Is there any similarity between PDH and other petrochemical process? What about the valves in PDH process then? Has it ever occurred that critical valve failure causes unscheduled process shutdowns? Any case with leakage and sticking reduces the accuracy of throughput control, affecting heater performance and process efficiency? How to avoid these events in the first place? We’ll discuss these and more in the coming postings.”
Propane dehydrogenation: Part 2 – continuous catalytic reforming
Propane dehydrogenation: Part 3 – reactor and product recovery