Creaming off the cost

One of the UK’s ten largest food companies, Dairy Crest has started up two biomass boilers at its Davidstow creamery in Camelford. The £4.2-million project is part of a green energy strategy at the Cornwall plant, which also employs advanced energy monitoring technologies.

The Davidstow site has a production capacity of 55,000 tonnes of cheese, including the Cathedral City and Davidstow brands. The biomass boilers claimed, by the company, to be the largest such units in the UK outside of a power station are expected to deliver 80% of the site’s steam demand.

Designed, installed and operated by Dalkia, the biomass energy facility is fuelled by processed wood pellets and provides all medium-pressure, saturated steam to the site. The new units replace two of the existing fuel oil boilers at the site.

The rural location of the Davidstow plant was key to the feasibility of the biomass project, as there is no natural gas pipe network to the site. Heavy fuel oil was previously used to power the three on-site boilers, with an annual fuel bill of around £3 million for steam alone.

The two 7bte/hr Byworth boilers employ a Proctor chain grate stoker system. They are designed to provide 7,000kg/hr of steam, operating at 23 bar.

“The biomass energy centre will help Dairy Crest to meet its intensive energy demands crucial to the manufacture of is produce using a carbon-neutral fuel,” according to Chris Terrett, site general manager at Dairy Crest Davidstow.

“The pasteurisation and whey drying processes have a high demand for steam, and Dairy Crest has been keen to find alternatives to oil to generate environmental improvements and drive cost reductions,” the site manager added.

In a separate project, Dairy Crest decided to instrument the boilers so that fuel-to-steam efficiency could be determined and benchmarks obtained (kWh/kg) for the fuel economy of each boiler at Davidstow. The work involved the installation of energy monitoring technology, from Endress+Hauser and eSight Energy.

Data collection

The equipment included Coriolis mass flowmeters on the fuel lines to the boilers, Vortex mass flowmeters on the steam generated from each boiler, as well as electromagnetic flow and temperature transmitters on the feedwater lines to each boiler.

All measuring points were connected to a data collection panel in the boilerhouse, which was in turn connected to the site’s Ethernet local area network.

Automatic interval consumption data was collected via a networked PC and then imported directly using eSight’s energy monitoring software. This enabled Dairy Crest to generate detailed reports on boiler fuel economy on a daily, weekly and monthly viewing schedule.

According to eSight, its energy monitoring solution provides all the data necessary to investigate and build a business case for methods of reducing fuel costs.
This, for example, included the installation of a deaerator that allows the feedwater to be maintained at a higher temperature of around 107°C. This meant less fuel was required to raise steam and resulted in an improved fuel-to-steam efficiency.