Particulate filtering for larger commercial and industrial biomass boilers is an important part of any installation to reduce any particulate emissions to exceptionally low levels, in line with the Medium Combustion Plant directive.
There are several choices of technologies that reduce particulates in the exhaust gases. These include “bag” filters, ceramic filters and electrostatic filters to lower particulate emissions to less than the stringent legal emissions levels. Each technology has its pros and cons and all 3 are regularly employed on biomass boilers systems above 1MW.
Electrostatic filters work by putting a high voltage potential difference across the filter, typically 50,000 volts. Any small particulates (e.g. PM10 and PM2.5) within the exhaust gases are electrically charged. When passing through the filter they are attracted to one side of the filter, attach and can be collected. This is a highly effective method of filtering but does require very high voltage.
The filter needs cleaning and servicing, typically once per year. Before a trained technician can enter the filter to clean and service, the system needs to be shut off, earthed and isolated. Because of the high voltages involved, there is a very strict process and methodology for doing this. This can only be done by a HV SAP (High Voltage Senior Authorised Person) who must be present to physically shut down the system, earth, test, lock off and certify that the Electrostatic Filter is safe and authorised for work to be carried out in accordance with the Electricity at Work Act 1974. When the cleaning and service is complete, the same HV SAP returns to check the system, re-energise the system and hand back to the client.
The majority of companies working in the biomass heating sector commission an external HV SAP to complete the necessary process and legal obligations before work can start on high voltage equipment. BBSM Ltd‘s technical director Adrian Ham, a qualified electrical engineer and time-served controls and commissioning engineer, recently undertook the intensive HV SAP training programme. BBSM Ltd now has this capability in house to support our engineering team. This is a major step forward which gives us more flexibility and continues our journey in building more and more skills in-house, enabling BBSM to offer its clients an end-to-end service and maintenance package without the need to subcontract out some elements of the package.