Economical aspects of using cogeneration in wastewater treatment plants

Cost-effectiveness of cogeneration investments depends on individual conditions in treatment plants and should be carefully analyzed. Analysis should be preceded by energy audit. However, some characteristics remain unchanged in all installations:

  •  The possibility of functioning in urban areas due to high efficiency, modular design, low gas and dust emission
  •  Constant access to ‘free’ biogas from the IFC (Isolated Fermentation Chambers) installations
  •  Heat production for treatment plant’s own needs – heating of buildings, IFC process heating, sludge drying
  •  Reduction of energy purchase from external sources
  •  In case of voltage decay in external electricity grid, the possibility to power treatment plant by using synchronized generators in cogeneration modules
  •  Lower energy losses during transmission
  •  Cost recovery shortly after investing in cogeneration
  •  It is assumed that the minimum size of cogenerator is 100kWh (about 60 000 Population equivalents in a wastewater treatment plant)

The effect of the CHP system operation on the example of a sewage treatment plant with a throughput of 26,400 m3 / day

The profitability of investment in CHP system

The example of the investment in CHP system with an electricial power of 345 kW w in wastewater treatment plant with a digester (estimation)

* Arithmetic average of the average electricity sales price in the 4th quarter of 2016.

Source: Report on the activities of the President of the Energy Regulatory Office in 2016

** Average sale price of heat generated in coal-fired generating units

Source: Information of the President of the Energy Regulatory Office No. 21/2017

The example of the investment in CHP system with an electricial power of 345 kW w in wastewater treatment plant without a digester (estimation)

* Arithmetic average of the average electricity sales price in the 4th quarter of 2016.

Source: Report on the activities of the President of the Energy Regulatory Office in 2016

** Average sale price of heat generated in coal-fired generating units

Source: Information of the President of the Energy Regulatory Office No. 21/2017

Advantages of burning biogas in cogeneration systems

  • Using biogas as a fuel limits CO2 emission
  • Burning biogas in gas engines is an environmentally friendly technology
  • EU support for investments of this kind
  • Reducing the emission of environmentally harmful substances
  • Reducing the amount of energy from external electricity grid
  • Reducing the emission of greenhouse gases by eliminating the torches (torches used only in emergency states of the system)

Technical aspects of using cogeneration in wastewater treatment plants

Cogenerative unit’s power range

Depending on used engines we offer the following power ranges in cogenerative units:

 

MAN (30-530 kW)

MWM (400-4300 kW)

Perkins (300-1000 kW)

Liebherr (140-500 kW)

Casing types

We offer several types of casing:

  • The frame – without silencing system
  • Soundproof casing, used mostly inside
  •  External soundproof container

Operating mode

  • Work paralel with the network
  • Work paralel with the network, with the possibility of reserve work
  • Synchronization of multiple cogeneration units

Cogeneration units regulation

  • By heat reception
  • By electricity needs
  • By the quantity of biogas

Additional equipment for the cogeneration installations

Stations preparing biogas:

  • Active carbon filters
  • Chemical and microbiological desulphurization
  • Biogas blowers and press knots
  • Biogas drying stations (cooling and heating)
  • Biogas torches
  • Biogas analysers

Measuring systems conforming to the demands of The Energy Regulatory Office:

  • Gross electricity meters
  • Heat meters
  • Gas meters

Biogas parameters and treatment systems

Problems caused by wrong biogas preparation

Exploitation problems:

  • System corrosions leading to malfunctions
  • Lower income
  • Premature consumption
  • Efficiency reduction

Increase in exploitation costs:

  • More frequent reviews
  • More frequent oil changes
  • Shorter periods between general renovations

Biogas desulphurisation

Microbiological:

  • H2S concentration<10 000 ppm
  • Maximum biogas flow: 3 500 m3/h

Dry with constant deposit:

  • H2S concentration<15 000 ppm
  • Maximum biogas flow: 1 5000 m3/h

Removing siloxans in active carbon filters

  • Combined with a drying station

Ecokube sp. z o.o.

ul. Wólczańska 128/134

90-527 Łódź

tel. + 48 42 630 66 00

biuro@ecokube.pl