PACT Core Facilities

PACT consists of integrated pilot-scale facilities with significant analytical capability. The integrated approach includes advanced computational modelling, experimental testing and detailed imaging to form a validating and complementary system, which ensures a credible output and in-depth understanding of the impact of flame characteristics, critical reaction kinetics, devolatilsation and char reaction in the combustion processes.

 

This understanding creates a unique and powerful combination for the development of models for individual processes and integrated systems.

 

The core facility’s computational modelling capabilities are based at the PACT site in Sheffield, with multiple modelling stations preloaded with relevant software including CAD Drawing, Fluent, Aspen, Chemical and Kinetic to support research and consultancy work and produce commercially viable solutions for companies.

The Air Combustion Plant (ACP) is a cylindrical design, 250kWth down-fired pulverised fuel combustion system with interchangeable coal/biomass burners, fuel (coal/biomass) feeding system, a dedicated air metering skid, flue gas filter, heat exchanger, and a temperature and flow monitored water cooling system for the combustion vessel and flue ducts.

 

The plant is operated using a dedicated control system connected to an industry standard SCADA system in a central control room for system monitoring, operation and data acquisition.

 

Lower floor of the rig (from left: Oxyfuel skid, air skid, gas heater controllers, bottom of combustion vessel, fuel feeding system. control PLC)

Example Applications:

  • Conventional combustion research with state of the art analytical capability to enable flame visualisation and modelling for combustion system design, development and optimisation.
  • Fuel testing and system optimisation for different types of fuels and fuel combinations coal, co-firing and biomass combustion.
  • Post Combustion Capture research: the rig flue gas is connected to a 1tonne/day (150kW equivalent) Solvent-based Carbon Capture Plant enabling post-combustion capture research with different fuels and under different combustion conditions.
  • Air to oxy firing: the rig enables conventional air firing as well as research into O2 enriched air combustion for example for more difficult samples such as biomass; in combination with a dedicated gas mixing facility the rig can also be operated in simulated and full oxyfuel mode with Exhaust gas recirculation as a 250kW Oxyfuel Combustion Plant.

Upper floor of the rig (from left: gas heaters and steam skid, Combustion vessel with burner on top, Flue gas duct to heat exchanger, connection to central flue gas duct to stack)

The 250kW Oxyfuel Combustion Plant (OCP) utilises the 250kW Air Combustion Plant operated in an Oxyfuel mode whereby fuel is combusted in an atmosphere of CO2 and O2 rather than in air. This prevents nitrogen in the air generating flue gases with around 95% CO2 suitable (after processing) for geological storage or CO2 utilisation applications.

 

In this mode the plant is operated with a dedicated Oxyfuel Gas Mixing System (OGMS) – an automatic high precision CO2 and O2 mixing skid, which provides individually mixed CO2 – O2 gas feeds, including high CO2/O2.

 

The plant can be operated in two modes:

 

  1. Full oxyfuel mode with Exhaust Gas Recirculation (EGR) where the CO2 comes from the exhaust gas recycled into the system with a make-up injection of O2 to enable combustion
  2. Simulated oxyfuel mode with individually mixed gas feeds supplied by the OGMS.

The system can operate between the two modes at different degrees of EGR and with different O2 concentrations. The plant is also equipped with dedicated gas heaters for each of the lines and can be operated as a dry/wet EGR system whereby steam, generated by dedicated steam package boiler, is injected into individual lines after the gas heaters. There is also a dedicated NO2 injection system for simulated EGR.

 

The plant is operated using a dedicated PLC connected to an industry-standard SCADA system in a central control room for system monitoring, operation and data acquisition.

 

The Oxyfuel Gas Mixing System has a dedicated control system that is interconnected with the main rig PLC for monitoring and data acquisition.

The gas turbine system is comprised of two Turbec T100 PH microturbines: a Series 1 and a Series 3.

 

Both turbines are combined heat and power (CHP) units integrating the T100 power module with a recuperator and exhaust gas heat exchanger for thermal energy recovery to improve efficiencies.

 

The Turbec T100 CHP units are typically fuelled by natural gas, but the use of fuels such as biogas, syngas, diesel, kerosene, methanol and LPG is also possible.

 

The microturbines use a high-speed generator to produce electricity, exported to the grid via our substation, with the single-stage centrifugal compressor and the radial turbine both placed on the same shaft as the generator. An exhaust gas recuperator is connected to the microturbine to improve electrical efficiency and the hot flue gases are expelled through a water-gas heat exchanger to generate thermal energy.

 

The turbine consumes 330 kW of natural gas and generates a maximum of 100 kW of electrical power at an efficiency of 33%. Used in combination with the counter-flow heat exchanger, each unit can generate an additional 165 kW of thermal power, bringing the overall efficiency to almost 80%.

 

The flue gases from the heat exchanger is connected to the central exhaust line, which is integrated with the post-combustion, solvent-based carbon capture plant. This enables research into various aspects of post-combustion capture from gas turbine-based power generation. These systems are highly instrumented to allow for full characterisation.

 

Further developments

The concentration of CO2 in flue gases from gas turbines is typically very low, which impacts on the economical and technical viability of the carbon capture process.

PACT has deployed a range of modifications to the turbines to improve system efficiency and enhance capture performance. These include exhaust gas recycling (EGR), selective exhaust gas recirculation (S-EGR) and humidification of the gas turbine cycle.

 

GT-EGR

  • Exhaust gas recycle (EGR) is an established concept for increasing the CO2 concentration in the flue gas, as well as minimising emissions of NOx. A portion of exhaust gas is recycled back into the air inlet, replacing nitrogen in the air and creating a CO2-rich combustion atmosphere and subsequently higher CO2 in the exhaust. Increasing the level of CO2 in the flue gas is important for the economic operation of post-combustion carbon capture technologies that work on a concentration gradient (i.e. solvent-based capture). At PACT we simulate the EGR process via small additions of CO2 to the combustion air.

GT – Selective EGR

  • Although similar to EGR, more substantial improvements can be achieved with selective CO2 recycling from the flue gas by using membrane technology. Membranes are able to selectively separate out the CO2 from the exhaust gases to pass it into the air inlet stream. For the gas turbines at PACT, large injections of CO2 into the inlet air can be used to simulate the S-EGR process.

Humidified turbine cycles

  • Adding moisture to the gas turbine cycle has a number of benefits – it can lower combustion temperatures to minimise emissions of NOx and augment turbine output and efficiency, as well as be a means of increasing the CO2 concentration in the flue gas to aid carbon capture. At PACT, we can add steam to the compressor discharge; by cooling the flue gas and condensing out the moisture, the relative proportion of CO2 in the exhaust gas stream increases.

The Solvent-based Carbon Capture Plant (SCCP) enables the development, evaluation and optimisation of a variety of solvents for post-combustion capture and related technologies.

 

It is designed to remove up to 1 tonne/day of CO2 (based on MEA) from an equivalent of approximately 150kW conventional coal combustion flue gas.

 

The plant incorporates 8m absorber and a cleaned flue gas wash column, re-boiler, desorber column and a condenser on top of the column, and fresh and spent solvent tanks. The absorber and desorber columns are equipped with temperature and differential pressure sensors, solvent sampling ports, provisions for corrosion coupons and alternative materials test sites, and trace gas injection capability. The plant also has an integrated flue gas desulphurisation carbonate wash system.

It is controlled and monitored through a dedicated control system.

 

The plant is connected directly to PACT combustion facilities: the 250kW Air Combustion Plant and the 300kW Gas Turbine System, enabling post-combustion capture research from real flue gases from natural gas power plants as well as pulverised fuel combustion plants including coal, biomass and co-firing.

 

The facility is also connected to a dedicated gas mixing facility enabling carbon capture from any synthesised flue gas compositions, including industrial effluent gas mixtures.

The Gas Mixing Facility (GMF) enables the mixing of individual gas components to create synthetic flue/process gas mixtures.

 

The GMF comprises three accurate gas metering and mixing lines fed directly from large O2, CO2 and N2 storage tanks, complemented by trace gas injection ports (fed by NOx and SOx cylinders and optionally other trace gases) to simulate different flue/process gas composition.

 

The GMF is connected directly to the Solvent-based Carbon Capture Plant (SCCP). The GMF has a dedicated PLC that can be operated from the SCCP or the central control room.

 

The integration of the GMF and the SCCP together creates a powerful combination enabling research on carbon capture from a variety of power generation or industrial installations.

The GMF has the potential to simulate emissions from any power plant operating under any given conditions and with any fuels. The GMF can also simulate emissions from industrial activities such steel or cement production, enabling the development of appropriate capture technologies for these sectors.

 

The integrated system also allows long runs (with synthetic gas mixtures) which would otherwise be impractical with the Air Combustion Plant. This is important in examining the performance and ageing of new capture media, where such tests could be prohibitively expensive on larger-scale installations.

The 240kWth Biomass Grate Combustion Boiler (BGB) forms part of the integrated facilities at PACT and is interconnected to the PACT Post-Combustion Capture Plant with a flue gas slip stream supplying an equivalent of 150kWth biomass flue gas to the capture plant.

 

The boiler can combust a wide range of biomass fuels, from forestry residues to waste-grade materials (e.g. waste wood) on a moving grate. The chipped/pelleted fuels are stored in the large on-site silo and fed into the system via screw feeders. The system also has an integrated heat exchanger with a water buffer and it has a built-in ash cyclone. Through a connection to the CO2 capture plant, there is the possibility to explore carbon capture from waste.

 

The system is supported by a wide range of online analytical capabilities including metal aerosol emissions analysis by online ICP; combustion stack and FTIR gas analyser; and fast particulate analysis by a Cambustion DMS500 analyser.

 

The BGB is equipped with a moving grate providing homogeneous combustion with continual automatic removal of combustion residue. It can operate on a virgin and recycled/waste wood and biomass chip/pellets.

 

The high-temperature post combustion zone ensures optimum combustion and supports the utilisation of lower grade fuels. Heat exchanger is equipped with tabulators for continual, automatic removal and a cyclone filter for fly ash removal. The boiler is equipped with an induced draft fan and individually controlled and metered primary air, fed under the grate, and secondary and tertiary air fed in the lower and upper combustion chamber respectively.

The system is fully automated and utilises pressure, temperature and lambda sensors for optimum combustion control and high efficiency. The combustion chamber, hot gas path, filter and exhaust are fitted with multiple sampling ports and temperature sensors, which enables detailed research of the combustion processes and emissions.

 

Distributed large access ports are used for a range of analytical probes including: heat flux, suction pyrometer, deposition and corrosion probes, thermal imaging camera probe and gas sampling probes for FTIR and combustion stack analyser; combustion and emission gas analysis, online metal aerosols analysis and online particulate analysis.

Example Applications:

  • BECCS research on biomass chip and pellet, including wood waste
  • Fuel development, blending and fuel screening research
  • Emissions research from waste fuel

Supporting Facilities

  • 25kW Combustion Rig
  • 350kW Gas/Liquid Furnace
  • 250kW Rotary Filter Furnace
  • 300kW Fluidised Bed Combustor

Analytical Facilities

  • Metal emissions monitoring laboratory (ICP)
  • Particle emissions analyser
  • Online Monitoring and Analysis
  • Analytical Labs