Feb-2023

Reducing fuel usage in the midst of a new gas demand reduction plan

Processing facilities, including refineries, power plants and petrochemical complexes, are soon likely to be feeling the effects of Europe’s latest Gas Demand Reduction Plan, a new legislation that expects members of the European Union to reduce their gas usage by 15% until next spring.

Integrated Global Services

Article Summary

The ongoing Russian-Ukrainian conflict is causing widespread issues relating to fuel supply cuts, with 50% of the EU’s Member States already noticing the impact. Classified as ‘critical to society’, refineries will, therefore, be under the watchful gaze of the European Commission, which now has the power to declare a mandatory reduction in gas demand across all Member States.

Stringent legislations combined with rising fuel costs are making it increasingly important for refineries to ensure that their critical equipment is performing at its peak efficiency and productivity. A 1-2% decrease in efficiency in fired heaters can consume an additional $1m in fuel across a 12-month period, placing additional pressures on refineries to ensure that the correct solutions are in place to prevent equipment deterioration.

This article will discuss solutions to issues in the radiant and convection sections of fired heaters, which affect performance and fuel usage.

Efficient combustion is integral to reducing fuel consumption
Process fluids are heated in the radiant sections of fired heaters. These fluids are transported through steel alloy tubes, all of which are heated using radiant heat generated by burners within the refractory lined box. If this process is hindered for any reason, whether that be a build up of fouling or oxidation, the outlet temperature falls and the flow of fuel increases.

What causes process tube oxidation?
Through continued usage over a long period of time, the steel alloy tubes transporting the process fluids oxidise, which leads to a steady build-up of scale on the external surfaces. These layers of scale act as an insulator, stopping conductive heat transfer and reducing radiant section efficiency. This then requires refineries to increase the firing rate to increase the temperature, a process that demands a faster flow of fuel.

What solutions are available?
Cetek high emissivity Ceramic Coatings offer a long-lasting, protective, thin-film layer on the exterior surfaces of process tubes to help prevent oxidation and corrosion. These coatings can be applied to existing tubes during a routine shutdown or added to newer tubes in a remote facility where surface preparation and curing of the ceramic coating also takes place. The thin layer of ceramic coating provides a consistent temperature differential between the exterior surface and the steel alloy tube, leading to a significant improvement in the reliability of tube metal temperature determination.

Convection section efficiency
What is fouling?
Fouling is brought about through the accumulation of unwanted deposits on the tube or fin surfaces, such as algae, scale and insoluble salts. In an industrial setting, for example, waste products from nearby plants make up a large proportion of the debris being dragged into the fired heaters. The majority of burners are designed to operate with one part per million airborne particulates, meaning that a single burner has the potential to pass 2.5 tonnes of debris through a heater in one year – some of which is likely to deposit.

How does fouling impact fuel efficiency?
To continue operating at the desired capacity in the instance of fouling, fired heaters must burn a greater amount of fuel. This not only fails to meet the demands of Europe’s new Gas Demand Reduction Plan, but it can also cost plants millions of dollars in lost revenue. Higher fuel consumption results in higher operating temperatures and reduced heat transfer, a combination which places additional stress on the alloy tubes and causes uneven expansion.

What solutions are available to tackle fouling?
The issues caused by fouling are commonly tackled using one of two traditional methods, chemical cleaning and dry-ice blasting.

Chemical cleaning
Chemical cleaning uses caustic agents like sodium hydroxide and hydrochloric acid to remove organic fouling from alloy tubing and can be used when a piece of equipment is online. If the nature of the fouling is unknown, however, it is almost impossible to predict how it will interact when confronted with certain chemicals. It is not unusual for the tube surfaces to experience a significant change in its properties when cleaned using chemicals, with major changes occurring to the surface charge, hydrophobicity and permeability.

Dry-ice blasting
Dry-ice blasting is a popular method of choice for removing fouling in heat exchangers and boiler tubes, largely due to its versatility and ability to clean fragile elements of equipment without causing any damage. The long-term benefits are limited, however, as accessibility often reduces the ability to reach more than 40% of the tube surface area.

What are the long-term solutions?
Tube Tech, an IGS Solution, utilises robotic cleaning systems to clean more than 90% of convection section tube fouling during planned turnarounds. Tube Tech’s robotic fired heater cleaning technology has the unique ability to access deep inside and between the banks of finned tube rows, simultaneously improving the efficiency of fired heaters and eliminating the need to burn more fuel.

Conclusion
With winter approaching and Europe likely to be facing a gas shortage due to unreliable Russian deliveries, the pressure is mounting for refineries to maintain the efficiency of their mission critical equipment by carrying out all necessary maintenance.

Delaying processes like fouling removal and ceramic coating will only lead to reduced equipment efficiency and a greater demand for fuel in the long term, both of which will not be easily solved if the European Commission declares a mandatory reduction in gas demand across all Member States.