Choosing the right industrial heating

Published:  08 April, 2015

Martin Cooke, technicalmManager at EOGB Energy Products Ltd, discusses the critical considerations to bear in mind when selecting a replacement industrial heating system.

Unlike other sectors which are seeing an increased usage in renewable technologies, industrial heating systems typically do not offer the same opportunities as they still require the overall power of larger burners to meet the requirement for substantial heat demands in either direct or indirect fired applications.

However, alongside the government’s focus on reducing the amount of carbon that is produced within industry in the UK, we have seen a bigger focus on plant designers making sure that their industrial heating systems are operating at full efficiency in a bid to reduce their impact on the environment.

Meeting energy efficiency standards

Energy saving is always one of the top priorities in the industrial market as cutting down on energy costs has a direct and significant impact on final product costs.

With careful consideration at the stage of selecting a heating system, a huge impact on efficiency, costs and overall environmental impact can be achieved.

When selecting a burner it is critical to consider the following:

• If it is fully modulating instead of two stage operation

• Whether it is pre-mix or blown gas

• Its turndown ratio (the amount a burner can increase and decrease its power across its range)

• The use of inverter driven fan motors

• If it has a low NOx combustion head (class 3 as per EN 676)

• If it has advanced combustion control, such as O2 and CO trim

All the above should be specified at the point of order. However, certain features such as combustion controls can often be retrofitted if required, providing the controls are compatible.

When selecting a replacement heating system, initial equipment cost is a huge factor. But, selecting what may seem the cheapest option initially, may not offer any long term savings.

People often think that implementing integrated energy saving measures will be expensive. However, by fitting technologically superior burners and controls, there is potential to pay back the initial extra investment within 1-2 years and continue to save energy and reduce CO2 emissions significantly year-on-year.

Environmental considerations

Along with attempting to ensure the plant is as efficient as possible, there is also the environmental impact of burning fuels that now is a major concern for air quality. Nitrogen Oxide levels are another extremely important factor to consider when selecting the correct heating equipment.

As per EN 676, gas burners are classified into three classes, with Class 3 being the lowest NOx levels up to 80 mg/KWh.

Burner Class NOx mg/KWh Methane NOx mg/KWh LPG

1 Up to 170 Up to 230

2 Up to 120 Up to 180

3 Up to 80 Up to 140

Burner optimisation

When a burner is matched to an industrial appliance it is extremely important to ensure that the burners working field (i.e. the range in which the burners fan can overcome the back pressure of the appliance it’s fitted to) is looked at very closely.

The information that is needed to make a perfect burner/appliance match is:

• The ‘over pressure’ of the appliance - the internal resistance of the combustion chamber that the burners fan must overcome.

• The appliance maximum heat input - the amount of heat required usually in KW to produce the required output. Losses will always happen during the combustion process therefore it is always required to put more heat in than you will get out.

• Internal heat exchanger dimensions - this is important to ensure that adequate flame space is available for the combustion chamber. Ideally the flame from the burner will burn without directly impinging on the surface of the heat exchanger.

• The burners ‘working field - the working field is the parameters in which the burner can operate within. This field is created when a burner is tested to see what resistance it can overcome within a heat exchanger, and at the same time the output it is able to fire.

Ideally a burner will be selected to allow the maximum turndown ratio. In order to obtain this, the burner that operates towards its maximum output against the appliance resistance pressure for the output of the appliance is the best suited. This is particularly important when selecting a modulating burner to ensure a broad operating range.

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