Case Study - Birmingham Bio Power Limited

8 minute read

Ian Gaunt

Technical Asset Manager

Birmingham Bio Power Limited (BBPL) and it’s contribution to Birmingham City Council’s Clean Air Initiative

Birmingham Bio Power (BBPL) are the Owners of a 10.3 MW Biomass Renewable Energy Power Plant based on the Tyseley Energy Park in South East Birmingham. The Plant cost £57m and entered commercial operation in 2016. A rationalisation of the ownership model has seen Gravis Capital as the sole owner of BBPL since 2021.

The Power Plant uses waste wood as its feedstock, up to 72,000 tonnes pa sourced primarily from the local area. Utilising this wood in the production of electricity provides a more sustainable option than otherwise sending such wood to landfill where it would decompose and produce methane, a gas that has 25 times more greenhouse gas potential than carbon dioxide.

The Power Plant uses novel gasification technology developed in Canada and imported to the UK in 2014.

Fig 1. Schematic of the Biomass Power Plant

Wood is delivered into the wood storage hall. Here it is transported via a hydraulically operated moving floor to a system of conveyors before being fed into four gasifier units, each capable of receiving up to 2.5 tonnes per hour of wood.

Fig 2. Cross Section of Gasifier & Oxidiser

Within the gasifier, wood is heated to 750 oC under an oxygen depleted atmosphere. The heat drives off several combustible gaseous compounds from the solid wood pile producing a “Synthetic” or “Syn” gas.

The combustible Syngas is fed to a central oxidiser unit where additional air is introduced and combustion takes place. The hot flue gas is then fed to a Heat Recovery Steam Generator (HRSG) at temperatures in excess of 1050 oC. The HRSG recovers the heat from the flue gas and uses it to convert water to steam. It is this steam that is then fed to a Steam Turbine which drives the generator to produce the electrical power.

The remaining flue gas is emitted to atmosphere and is continuously monitored for pollutants in accordance with new plant standards and its environmental permit. Emission Limit Values (ELVs) are set by the Environment Agency and are influenced by legislation and local air quality considerations.

A summary of the Plant’s performance in 2021 is shown below.

Table 1. Results of emissions to air that are continuously monitored
Table 2. Results of emissions to air that are not continuously monitored

Birmingham’s Air Quality Monitoring focusses principally on Particulates and Oxides of Nitrogen. In both respects the Biomass Power Plant performs well under statutory limits.

To reduce Particulate emissions the Plant utilises 1050 cylindrical filter bags, each individually pulsed with compressed air to dislodge the ash which falls into awaiting hoppers and removed from site.

To reduce Oxides of Nitrogen, the Plant injects Urea into the hot flue gas path and relies on the following chemical reactions.

  • CO(NH2)2 + H2O --> 2 NH3 + CO2
  • 4 NO + 4 NH3 + O2 --> 4 N2+6 H2O
  • 2 NO­2 + 4 NH3 + O2 --> 3 N2 +6 H2O
  • + other reactions

Similarly acidic gases of HCl, HF, SO3 and SO2 are reduced through the injection of lime and other additives producing the following chemical reactions:

  • HCl + Ca(OH)2 ­--> CaClOH + H­2O, HCl + CaClOH --> CaCl2 + H2O
  • 2HF + Ca(OH)2 --> CaF2 +2 H2O
  • SO2 + Ca(OH)2 --> CaSO3 + H2O
  • SO3 + Ca(OH)2 + H2O --> CaSO4 + 2 H2O

In total, the Plant spends around £400,000 pa on flue gas additives to comply with the emission limits regulated by the Environment Agency.

In addition, in 2017 an independent consultant was commissioned to undertake an atmospheric dispersion modelling exercise, to characterise the expected dispersion of emissions from the Plant’s Main Stack based on actual emissions data, local topography and 5 years of meteorological data. The pollutants specifically of interest included Nitrogen Dioxide (NO2).

Modelling results were assessed against applicable Environmental Quality Standards for the protection of human health at identified sensitive receptors and the results are shown below.

Table 3 Impact of Emissions on local sensitive receptors

In summary, through the introduction of new private capital, technologies and techniques, BBPL has been able to provide its local community with employment opportunities and a source of sustainable power generation whilst also positively contributing to the local air quality improvement initiatives championed by the City Council. Whilst the cost of compliance has been significant and remains challenging, it has proven not to be a significant barrier to the overall success of the project.

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