SAFETY IN NAPHTHA CRACKER PLANT

Abstract

Naphtha cracking process is used to convert complex hydrocarbons to simple hydrocarbons like ethylene, propylene, etc. by using steam as heating medium. Pyrolysis or steam cracking is the primary process utilized to manufacture olefins from large hydrocarbon molecules. This gas-phase reaction takes place in metal alloy tubes within a fired furnace. Lower olefins (ethylene and propylene) are industrially produced by the steam cracking of hydrocarbons. The steam cracking operation involves heating the hydrocarbons in radiant coils in the presence of steam in a furnace. The heat is transferred to the coils by radiation, and the coils are made of high alloy materials capable of withstanding the high temperatures above 800 °C in the bulk fluid. To avoid undesired side reactions, which would lower the selectivity of ethylene in the process, the reactants must be cooled down as quickly as possible. This step is carried out in transfer line exchangers immediately after the radiant cracking zone. The products are cooled down and separated to yield olefins and other co-products. The present dissertation work has been conducted in Naphtha Cracker plant, at Panipat where ethylene and propylene are the main products. The various hazards that are possible to take place in the naphtha cracker plant have been identified during the study and various preventive measures have been suggested. Hazard and operability (HAZOP) study is the most widely used and preferred approach in the chemical plant to accomplish hazard assessment qualitatively and quantitatively. The HAZOP study requires the examining the process P&ID systematically, identifying every conceivable deviation from design intent in the plant using a `guideword' approach; determining all possible abnormal causes and the adverse consequences of that deviation. Deviation or changes in the process parameters (such as temperature, pressures and levels of chemicals, etc.) of naphtha cracker plant may lead to serious accident and undesirable product since the product quality is sensitive; therefore qualitative and manual HAZOP study has been carried out as a dissertation work for better performance of the process system as well as safety. The present HAZOP report shows the possible abnormal causes and consequences of hazards in the plant. A brief result discussion is also performed based on the present HAZOP study report and also preventive corrective measures and recommendation has been made to improve safety performance of the process and the production line as well.