Low sulphur fuels on tap

Malcolm Latarche
Malcolm Latarche

18 September 2017


With the 2020 date for the global sulphur cap now firmly etched in shipowners’ minds and rapidly approaching, the choices for complying may seem limited but a new option may soon become available if appropriate partnerships can be set up in time. Once the 2020 date arrives, ships everywhere outside of SECAs are obliged to use fuel with a sulphur content no higher than 0.5% by mass. Undoubtedly there will be some cheating and some flag states may give waivers to vessels on their registers when operating in domestic waters or even on the open sea if supplies of compliant fuel cannot be found. Even if supplies are available those flag states may choose not to penalise operators for contraventions but that is not a situation that can be relied upon. Port states – at least a good many of them – are not likely to offer any concessions except in extreme circumstances. The IMO believes that sufficient supplies of compliant fuel will be available even if others with their ear closer to the ground do not. Price of available fuel was not a factor in the IMO’s deliberations even if it must be for operators. Assuming that refiners do not produce sufficient quantities of compliant HFO, the choice for the vast majority of owners is stark; use distillate fuels or install a scrubber. The argument that refiners will even have trouble producing sufficient quantities of distillate – it would require as much as a five-fold increase over current quantities - is one that has fallen on deaf ears. An option that very owners have yet considered is the possibility of removing the sulphur from fuel before it enters the engine rather than after it has been burned. Although there is as yet no commercial offering available for doing this, there are a number of organisations that are developing systems that can. Refiners have already invested large sums in de-sulphurisation equipment to meet demand for low sulphur road fuels. They have had to do this because the regulations in most countries that restrict sulphur levels prohibit sales of anything that is non-compliant. When allowing exhaust gas cleaning systems and other treatment methods for ships to comply with its rules, the IMO has allowed the continued use of fuels with any sulphur content. Some see that as an error but it was at the request of the shipping industry which wanted the option of staying with cheap fuels and using technology to solve the problem. The technology and equipment used for de-sulphurisation in refineries is not practical for shipboard use for a variety of reasons. In refineries, the technique most commonly used is known as hydrodesulphurisation (HDS). The process makes use of hydrogen which in the presence of a catalyst combines with the sulphur to form hydrogen sulphide which is a toxic gas. This takes place in trickle-bed reactors which are commonly operated at temperatures in the range 300–450°C, and at high pressures approaching 140bar. Quite clearly with a dangerous gas involved and high temperatures and pressures, HDS is not suitable for small scale operations on ships. Another process which could be much more suitable is Oxidative De-sulphurisation (ODS). The process can be carried out at between ambient temperature and 80°C and pressures of 3.5bar or lower and although hazardous chemicals are involved they are in liquid form and easier to manage. The process also uses a catalyst which can either be solid or liquids. The latter being easier for scaling to increase flow and production. Instead of hydrogen the ODS system uses an oxidant such as hydrogen peroxide (H2O2) which reacts with the sulphur oxides to form sulphuric acid (HsSO4) which can then be removed from the fuel using a solvent. To read the full article order a copy of the latest journal.