Cutting corrosion at WtE plants

Online Editor

Following the US government’s call for development of ‘novel corrosion-resistant materials’ to improve waste-to-energy processes, what happens next?

Based on the successful waste-to-energy (WtE) green economy seen in Scandinavia and Japan, governments are now vamping up their investment into this alternative energy source. To support this increased demand, the US Government has identified ‘novel corrosion-resistant materials’ as a key requisite in ensuring that WtE plants run as efficiently as possible.

According to the US Energy Information Administration’s 2020 Report, in 2018, 50% of the USA’s municipal solid waste (MSW) was sent to landfill. While this clearly has detrimental implications for the environment, it is also a drastic waste of potential resources.

Although in the same year the USA burned 12% of its MSW to generate energy, this figure pales in comparison to other countries such as Japan and Scandinavia (including Denmark, Norway and Sweden), which burned 74% and 53% of their MSW respectively. The UK also has room for improvement in its handling of MSW, having burned 38% in the same year.

Given the huge environmental and economic benefits the WtE process affords, and indeed has been demonstrated in other countries, governments are now poised to make significant investment into this green technology.

Coatings And Composites Are Key Assets

To support this growth, in its 2019 Waste-to-Energy Municipal Solid Wastes Report, the US Department of Energy said: ‘Several R&D opportunities exist to reduce operating costs and increase revenues in existing incinerators facilities…’. This includes the development of ‘novel corrosion-resistant materials’. The report goes on to say how the development of these types of corrosion solutions ‘…can reduce operating costs of incinerator systems by reducing the frequency of system maintenance.’

These anti-corrosion systems are required for not just ‘Improving waste-to-energy conversion in existing facilities’, but also, given the growing demand for WtE sites, for ‘developing technologies for next generation facilities’.

Considering the myriad of benefits WtE plants can offer, ‘corrosion-resistant materials’ play a fundamental role in the WtE process. As such, it is imperative that materials are sought that not only protect key WtE assets, but also significantly increase the efficiency of WtE technology for the long term.

How does a Waste-to-Energy plant work?

In the WtE incineration process, carbon rich household waste is burnt, releasing thermal energy used to heat water inside a boiler subsequently generating high-pressure steam. This then drives a steam turbine that converts the steam energy to electrical energy, which is then relayed back to the grid. Excess steam can also be piped out and used to heat local homes and businesses.

Key advantages of Waste-to-Energy generation

According to the Confederation of European Waste-to-Energy Plants (CEWEP), WtE plants in Europe can supply 18 million inhabitants with electricity and 15.2 million inhabitants with heat. This is based on 90 million tonnes of remaining household and similar waste that was treated in 2015 in Europe.

In terms of offsetting carbon emissions, the CEWEP states that depending on the fuel being replaced, (gas, oil, hard coal or lignite) between 10-49 million tonnes of fossil fuels emitting 24-49 million tonnes of CO2, would not need to be used by conventional power plants to produce this amount of energy.

Based on the success of WtE plants seen in Europe, the 2020 No Time to Waste report created by the UK think-tank, Policy Connect, outlines the following key advantages that could be achieved should the UK increase its investment into WtE.

For environmental benefits, the report details how in 2030 alone, if 80% of MSW is sent to WtE rather than to landfill, this will allow the UK to avoid four million tonnes of CO2 emissions. This figure equates to the same emissions created from over nine million barrels of oil.

For energy output, the report details how if 80% of residual waste goes to WtE by 2030, this would generate enough low carbon heat to support over half a million homes. This is the equivalent to Birmingham, or Edinburgh and Glasgow combined, or Liverpool and Manchester.

Outlining the financial savings made by investing in WtE technology, the report identifies how the UK currently spends £280M annually on shipping ‘non-recyclable’ waste overseas. This is money that could otherwise be spent on building domestic infrastructure. For example, with this amount of capital, 10 plastic recycling facilities could be built in the UK each year, which in turn would see a significant rise in green jobs available across the UK.

In a foreword to the report, 13 cross-party politicians said: ‘The need for safe and effective removal of our waste has never been more important. As the UK embarks on our Build Back Better movement, we must no longer simply bury or export the problem.’

They continued: ‘Instead, we should, as other European economies do, treat residual waste as a valuable resource to produce lower carbon heat and energy, alongside a focus on achieving our important recycling targets and investing in innovative recycling technology.’

How To Reduce Costs And Improve Efficiency

Belzona Polymerics has been developing and honing its range of polyurethane and epoxy repair materials and corrosion-resistant protective coatings since 1952. With R&D teams based in both the UK and the USA, the departments have over a century’s worth of combined knowledge in the field of polymer technology.

In terms of supporting growing WtE infrastructure, this extensive knowledge and experience is critical. It ensures that repair and protection formulations are perfectly attuned to the needs of, what can be, aggressive and challenging operating environments.

Belzona provides the following range of ‘corrosion-resistant’ repair composites and industrial protective coatings that are specially developed for ‘reducing the frequency of system maintenance’ and improving efficiency of key WtE equipment.

For the solid handling part of the WtE process, Belzona’s 2000 series of polyurethane systems can be deployed to repair and protect ripped conveyor belts. The flexible rubber repair material, 2311 (SR Elastomer), is specially developed for emergency and permanent applications where high build, durability, elasticity, high abrasion and tear resistance are required.

Screw conveyors can also be coated using the 1800 series products to protect the screw shaft and fins from abrasion damage.

Designed for the repair and protection of equipment damaged by fine particle abrasion, Belzona 1812 (Ceramic Carbide FP) is an epoxy composite material combining extremely hard closely packed abrasion resistant ceramic aggregates in a polymeric binder.

For the thermal treatment and conversion stages, pipes damaged by erosion-corrosion can be repaired with SuperWrap II. Engineered to provide superior strength, corrosion and chemical resistance for pipe wrap and patch repairs, this repair system is an alternative solution to replacing defective metallic substrates.

For pump coatings, Belzona 1300 systems can be deployed, such as Belzona 1341 (Supermetalglide). This technology is designed to increase pump efficiency by using hydrophobic technology to repel process fluids and reduce turbulent flow. Efficiency increases of up to 7% have been recorded on new equipment and up to 20% on refurbished equipment.

For the basic process flow stage, incinerator fasteners can be lubricated using the high-temperature lubricant, Belzona 8211 (HP Anti-Seize). This is a pre-assembly material for metal components subject to high temperature. It prevents seizure, corrosion, pitting, galling and thread distortion.

For chemical containment areas such as chemical bunds and chemical tank linings, Belzona 5892 and Belzona 1391T can be specified. These systems provide excellent erosion-corrosion protection at elevated temperatures along with resistance to a wide range of process chemicals, such as the lime used in flue gas desulphurisation units.

Conveyor plates handling the hot incinerator bottom ash can be protected against elevated temperatures with Belzona 1300 series systems such as Belzona 1391T. This ceramic filled epoxy coating provides erosion and corrosion resistance to high temperature equipment operating under immersion up to 130°C.

Specially developed for pipe linings and pipe insulation repairs, Belzona 5800 series systems can be deployed. Belzona 5871, for example, can be used to protect operators from direct heat contact burns. A solvent-free system, Belzona 5871 provides a thermal insulation barrier with corrosion protection as well as thermal and sub- zero ‘cool-to-touch’ properties.

Belzona 1000 series systems are frequently used for general repairs to heat exchangers’ components such as tube sheets, flange faces, water boxes and end covers. For example, the composite repair system Belzona 1111 (Super Metal) provides outstanding protection under many varied service conditions.

To protect exterior chimneys from damage caused by weathering and acidic ash, Belzona 5100 cladding systems meet the requirements. For example, the urethane coating Belzona 5111 (Ceramic Cladding) is designed for the protection of metallic and masonry surfaces against physical, chemical and bacterial attack.

 A combination of Belzona 2211 (MP Hi-Build Elastomer) and Belzona 3111 (Flexible Membrane) can be applied to protect roof joints. These systems have been proven to leave roofs protected for longer periods of time than can otherwise be achieved through conventional welding methods.

As all of these systems can be carried out without the need for hot work, this facilitates a fast, safe and efficient repair and protection solution.

Supporting Transition To Net Zero

Given the imminent growth of WtE technology, it is essential that appropriate ‘corrosion-resistant materials’, including composite repair systems and protective coatings, are deployed. It is through their installation, that ‘existing facilities and developing technologies’ in the WtE sector can perform to their optimum potential for the long term.

In turn, this supports a reduced carbon future, in line with the 2050 net zero carbon guidelines set out in the Paris Agreement, as well as significant economic savings for governments worldwide.