Steam cracking is broken down into its fundamental elements. Fired heater operation and safety is studied in detail as the means of providing the heat energy that causes the pyrolysis reaction within the coils in the presence of steam to form olefins.
We will look at a variety of furnace designs that attempt to improve selectivity through residence time reduction. We also look at the coil materials on offer to lengthen tube life. Decoking will be studied in detail to find the balance between tube life, downtime and severity.
Within the coils we study the chemistry in action, how to optimize the conversion to maximize yield, the variables at play, and the deposition of heavy hydrocarbons as coke that has the potential to derail the operation and hence the economics of steam cracking. Experimentation and statistics are unavoidable in steam cracking optimization, so we will provide a foundation of experimental design and data analysis techniques to create models of furnace conversion and decoke optimization.
Optimisation of cracking is a joint exercise between engineering support, operations and maintenance. We therefore need representatives from each team to learn about the realities of optimizing conversion whilst balancing maintenance and safety risks. Attendees need to be of similar experience to gain the most from the course. The course can be tailored to new hires or experienced engineers and operators, but the pace of the course will be dictated by the least experienced.
You Will Learn How to
Steam cracking is a highly specialized application of thermal cracking. On this course you will learn to understand and optimize:
- Cracking chemistry: Dehydrogenation
- Furnace design
- Fired heater operation
- Process control
- Burner management
- Steam plant
- Mathematical modelling and analysis
- Constraint pushing
Thermal cracking will be studied as the bedrock of the petrochemical industry. Fired heater design and process safety will be covered, before moving on to the reactions inside the coils. We’ll look at how thermal cracking is enhanced using steam to control conversion as well as temperature.
Many variables are at play in optimizing conversion including the cracking furnace design itself, so we’ll look carefully at the mechanical aspects of design, before moving on to maintenance, and particularly decoking.
To optimize conversion we’ll study experimental design, data regression and analysis to develop optimization models to be applied not only to conversion but also decoking.
Modern high-pressure steam cracking (pyrolysis) produces alkenes (olefins), which are the basis to produce polymers. We will consider the different designs of fired heater used for thermal cracking. The reaction temperature is very high, but the reaction can only be allowed to take place very briefly. In modern furnaces the residence time is reduced to milliseconds to improve yield. A higher cracking temperature (also referred to as severity) favors the production of ethene and benzene, whereas lower severity produces higher amounts of proponent, C4-hydrocarbons and liquid products. In steam cracking, the gaseous or liquid hydrocarbon feed is diluted with steam and briefly heated in a furnace without the presence of oxygen. We look at optimizing the products (conversion) based on the composition of the feed, the hydrocarbon-to-steam ratio, and on the cracking temperature and furnace residence time.
After the cracking temperature has been reached, the gas is quickly quenched to stop the reaction, we will look at different quench techniques.
The process also results in the slow deposition of coke, a form of carbon, on the reactor walls. This degrades the efficiency of the reactor, so reaction conditions are designed to minimize this. A steam cracker will run for a few months at a time between decokes, which require the furnace to be offline. Balancing severity and conversion with decoke cycles and tube life is an important optimization that will be investigated during the course.
We’ll study the mechanical aspects of each part of different furnace designs, emphasizing fired heater safety as well as tube materials. We’ll also look at the process control aspects of fired heaters and furnace operation such that we are aware of all the variables involved in optimum operation.
Having identified the variables we then need to be able to experiment within safe boundaries to optimize conversion (or yield). We ‘ll look at the design of experiments, data collection and analysis, along with statistical techniques for data regression such that we learn how to develop models of conversion and decoking optimization.
Furnace operation is only part of an overall petrochemical plant operation. Optimization can also include deliberately lowering conversion to take advantage of plant capacity and the ability to recycle unconverted ethane. Constraints external to the furnaces also influence furnace operation, such as fuel balance, so we’ll finish by considering overall constraints and how to optimize within these constraints.
Upon completion, you will receive a Worley Academy Certificate of Completion.