Spirotech | District heating powered by waste

Spirotech | District heating powered by waste

A district heating system serving 5,000 homes in St. Ann’s, Nottingham is benefiting from bespoke filters manufactured by Spirotech UK.

NCC Enviroenergy approached a number of UK manufacturers to quote on the production of five custom-made demountable dirt separators for five of the district pumping stations serving properties in the area, but only Spirotech was prepared to meet the specification requirements.

Enviroenergy, a service within Nottingham City Council’s Communities Environment & Resident Services Department, is responsible for delivering the heat and power to homes and businesses across the city and is often able to offer cost reductions and environmental advantages over other energy sources.

The network comprises of 98km of insulated pipework carrying pressurised hot water around Nottingham City Centre and St. Ann’s and meets the heating and hot water requirements for 5,000 dwellings and over 100 commercial premises. These include the Victoria shopping centre, the National Ice Arena, Nottingham Trent University, BioCity, HM Revenue and Customs, the Theatre Royal and Royal Concert Hall.

Municipal waste
Heat energy comes from the incineration of 185,000 tonnes of municipal waste at the Eastcroft Incinerator, which is used to create a supply of super heated highpressure steam, supplied directly into the Heat Station. Back-up is provided by gas boilers to ensure a reliable supply.

As a Combined Heat and Power (CHP) Plant, steam is also used to run turbines
generating around 60,000MWh of electricity per annum. Electricity is supplied to commercial customers through a private wire network with excess power feeding into the National Grid.

Within the District network are several pumping stations and two core operating systems — a primary distribution network that operates up to a maximum of 140˚C and 11 bar; and a secondary distribution system, which pumps the water around the residential area at 85-88˚C, in the region of 7-8 bar.

Purpose-built demountable units
The NCC Enviroenergy Plant & Network Projects Engineer, commented: “The primary flow filters in each substation had reached the end of their operating life and required replacing. However, most of the dirt separators of this type are only rated for 10 bar and a maximum operating temperature of 110˚C.

“Although we contacted several UK manufacturers to provide replacement filters for the primary network, only Spirotech responded developing five purpose-built demountable units, capable of operating at temperatures up to 140˚C and 11 bar.

“Spirotech produced the higher pressure and higher temperature units to comply with the PSSR (Pressure System Safety Regulations) and the PED (Pressure Equipment Directive).

“The Nottingham district heating system is based on a structure developed in Denmark and extensively used in Scandinavian countries. Such an approach is becoming more widespread in the UK and is about improving efficiency and reducing the amount of carbon created.”

Spirotech’s purpose-built demountable units are capable of operating at temperatures up to 140˚C

Heat generation
The incinerator is located on a nearby site, just outside the centre of Nottingham
and has solved the city’s rubbish problem. It has two waste processing lines and
space to extend for the installation of further lines if required.

Each unit is rated to burn 11.5 tonnes of municipal waste an hour, 24 hours a day. The moving grates are rocked automatically by hydraulic mechanisms to keep the rubbish mixed and burn evenly and stop the formation of clinkers. The ash which is formed from the process is taken offsite before the ferrous metal is removed by magnet for recycling. The ash is also recycled into aggregate.

The incineration of rubbish to generate heat energy contributes to meeting global climate challenges, otherwise the waste would end up in landfill and create methane gas.

Spirotech Area Sales Manager Dave Goodyer said: “As a manufacturer we aim to go beyond the call of duty and this was a good example of this. NCC Enviroenergy required demountable units so they could be taken apart for statutory inspections and cleaning. As we don’t produce top demountable units in our SpiroTrap DN80 and DN100 ranges, we had to modify them to accommodate the required specification.

“Today’s energy-efficient heating and cooling systems can only provide optimal
performance with dirt free water. Magnetite in particular leads to greatly reduced energy efficiency and this will, of course, ultimately lead to increased running costs.

“Our SpiroTrap range is suitable for various temperatures and pressures and separate and remove very small particles from 5um (=0.005 mm) upwards. The dirt can be drained whilst the system is in operation and only takes a few seconds — it’s not a dirty job compared to a filter solution.”

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