Jarkko Aro takes a look at bringing coal and gas power plants into the 21st century
In the UK at least, the era of widespread fossil fuel usage appears to be waning, as industries and sectors are encouraged to make a concerted effort to ‘go green’ with their processes and equipment. With a recent report by the UN stating that CO2 emissions targets are set to be missed across the world, this pressure is only likely to increase. The power generation and distribution industry, by its nature, finds itself constantly under the spotlight, but at a time where closing older, less-efficient plants, may not be a costeffective option, how can the industry put plans in place to modernise its processes and equipment?
Where coal and gas fired plants are concerned, assessing the type of fuel used for combustion is likely to be the first port of call in any upgrade process. In the UK, the power generation sector does appear to lag behind those of other European countries, preferring to build new plants, rather than invest and convert older infrastructure.
For instance, in Finland there has long been a push to change the fuel for the boilers, rather than putting plans in place to build entirely new plants. Currently, Vantaa Energy is undergoing a biomass conversion project at one of its power plants, which will see a disused boiler retrofitted with equipment allowing it to burn locallysourced fuel.
Building a new plant, instead of converting an older one, often means that there are large amounts of operational – but unneeded – infrastructure left over. This includes switchgear across the plant, as well as connections to the wider grid network. In many cases, renovating this infrastructure and bringing it in line with current industry standards for efficiency could potentially represent a significant cost saving for operators.
In terms of the building process itself, getting a new plant off the ground can understandably be an arduous process. From securing initial investment to navigating planning approvals and the unavoidable objections, building a plant from scratch is no straightforward task. This is evidenced by the fact that currently in the UK, out of every ten reasonably-sized energy projects, eight are likely to be held up or delayed.
Particularly where older plants are concerned, upgrades often focus on the feed-in stock for the boilers, which in many cases is not optimised to match the combustion requirements of the plant. For example, power plants in general rely on superheated steam to operate the turbine systems and to get to this stage, a large amount of raw material is required for the boilers. However, once systems have reached a stable operating temperature, less raw material is required to be fed into the furnaces to maintain this level. Older plants may not have systems installed which directly track the relationship between raw material input and heat output, resulting in excess fuel being used to maintain boiler temperature.
Combustion efficiency monitoring is also closely linked to the type of fuel being used. For example, one plant using a paper-based material and another using steel-based material will have different temperature ranges needed to burn on maximum level.
Understanding these temperature fluctuations and being able to adjust the feed-in stock accordingly is even more important when considering a plant upgrade process which may involve switching away from coal or gas, to a different fuel for the boilers.
A large proportion of this awareness relates to having plant-wide monitoring systems in place, which often are not found in older operations. As far as efficiencies are concerned – either in terms of the power generation process itself or smaller, individual processes – having a view of the whole plant is essential. Being able to access real-time data about what is happening where, as well as spotting areas where energy may be being wasted, is invaluable.
Alongside assessing the fuel type for combustion, equipment must form a central pillar of any power plant improvement programme, in particular the drives installed across the plant. In general, direct online starters for traditional drives draw a high current until the drive is up to speed, placing a significant energy burden on the plant. As an alternative, there has been a push within the industry to move to variable speed drives, which place much lower demands on the system, saving energy in the long run, and driving efficiency.
It is important to note that innovation in the area of drives is going forward at a rapid pace and even plants which installed variable speed drives a number of years ago may find that these systems have now become outdated and the equipment inefficient. Identifying if this is the case once again links back to understanding energy and fuel usage across the plant as a whole entity, before isolating individual parts of the process to upgrade or improve.
Power generation is evolving quickly and physical plant infrastructure is here to stay, at least for the time being. Instead of building new infrastructure from the ground up, efforts should be made to make use of what is already in place, assessing fuel type, burn processes and efficiency across the whole plant, in order to bring older operations up to 21st century standards.
I.C. Electrical Ltd.
Jarkko Aro is sales and operative director, at I.C. Electrical, part of VEO Group. I.C. Electrical Ltd is an electrical engineering contractor based centrally in the UK. It is capable of providing a complete in-house electrical engineering solution incorporating the design, build and installation of control panels, HV and LV electrical systems, communication and automation systems along with small power and lighting installations.
For further information please visit: www.icelectrical.co.uk