Since the world depends greatly on oil and gas, oil refineries and other facilities that process hydrocarbons operate 24 hours a day, 7 days a week to meet the demand and maximise efficiency. In order to understand how important, the efficiency of a refinery is, it is worth mentioning that company’s share price can alter as the efficiency of the refinery changes. The design and building of refineries incorporate complex technology and there will always be the need for maintenance work, such as repairs, upgrades, and inspections. Some of this work can only be done when the equipment has been shut down and made safe for human entry. This activity is known as turnaround. Before the equipment is opened to the atmosphere it needs to be decontaminated. The decontamination process aims to remove volatile hydrocarbons, hydrogen sulphide, deposits of pyrophoric iron and other fouling materials. The use of steam, nitrogen, or air to strip out the contaminants, high pressure water jetting, and hot or cold water washing are some common mechanical decontamination techniques that have employed for many years. These mechanical cleaning techniques require large amount of water, which will be high in Total Organic Carbon (TOC) after the process. An alternative to mechanical cleaning is the chemical cleaning, a process that removes organic and inorganic fouling materials by a combination of solvency, fluid velocity and heat. Vapour phase cleaning has been used in the past successfully for the decontamination of refinery equipment. Most of the methods use a two-step cleaning procedure, where initially the organic deposits are removed, and the equipment is degassed, and the second step involves the neutralisation of pyrophoric iron sulphide deposits. Stricter environmental policies, the requirement of reduction in cost, energy consumption and plant down-time have created the need for a more efficient decontamination procedure. The purpose of this study is to develop a new single step vapour phase decontamination process to reduce carbon dioxide emissions during refinery turnarounds. The formulation of the new chemical will be optimised using Response Surface Methodology. Some of the functions that the chemical should posses are being able to remove hydrocarbons present in the equipment and a form an emulsion with them, neutralise pyrophoric iron sulphide deposits and remove any hydrocarbon vapours and hydrogen sulphide present. Following the lab work the new decontamination process will be tested at the specially designed pilot unit that will replicate refinery conditions as far as possible. The new formulation optimised by this study has the commercial name V-Purge and has been successfully used in refineries. A gas sampling and analysing method was developed to provide efficient monitoring of the decontamination process.
Georgios is an MRes student at the Department of Chemical Engineering.