The main objective of WP3 was to develop a conceptual design for a 20 MWth pilot plant that demonstrates the next step for the development and scale-up of the CCL technology towards industrial implementation. The process configuration and nominal operation conditions with mass & heat balances for the 20 MWth pilot plant were established based on the results of WP1 & 2 utilizing validated scale-up tools. The components of the 20 MWth pilot plant were designed and engineered, comprising the fluidized bed reactors with their auxiliaries, the coal, sorbent make-up and oxygen supply systems, the spent sorbent/ash handling system, the heat recovery to the water/steam cycle, the flue gas filtration, the CO2 purification system as well as all utility systems required. A detailed measurement plan was defined and the operation was studied including normal operation, start-up & shut-down procedures and the logistics for the supply of consumables and the disposal of residuals. Piping & instrumentation diagrams and the plant layout arrangement were elaborated depicting all major components of the pilot plant. A Health and Safety Risk Assessment and a Technical Risk Assessment were carried out for identification of potential risks and subsequently the process to obtain the required permission from the authorities for the erection and operation of the 20 MWth pilot plant was evaluated. All information acquired was used to calculate the overall investment cost, operational costs and maintenance costs for the scaled-up 20 MWth pilot plant. Unit 6 of the Emile Huchet power plant was selected as the theoretical host site for the integration of the 20 MWth pilot plant. The selected 600 MWe coal-fired power station, owned and operated by Uniper, is located in Saint-Avold in France.
A Basis of Design (BoD) was defined comprising main boundary conditions selected for the design of the 20 MWth pilot plant. Table 1 gives an overview of main boundary conditions selected for the design of the 20 MWth pilot plant.
Table 1: Boundary conditions of 20 MWth pilot plant design
|Coal for host plant & calciner||Hard coals (“El Cerrejon” & “US high sulfur”)|
|Coal particle size for calciner||d50< 90 µm|
|CO2 in flue gas to carbonator
@ 100 – 52 % EH6 capacity
|10.2 – 7.2 mol-% wet|
|CO2 capture efficiency||approx. 90 %|
|CO2 product quality||> 95 mol-% (saline aquifer quality)|
|Thermal duty total||20 MWth|
|Sorbent||Lhoist “Limestone 0.1-0.3mm Messinghausen”|
|O2 purity||99.5 mol-%|
|O2/moderation gas mix||40 – 50 mol-% O2|
|Emission limits||per Industrial Emissions Directive (IED)|
Process Configuration and Process Description
The process configuration for the 20 MWth pilot plant was defined (see simplified scheme in Figure 1) utilizing the experience from the 1 MWth pilot plant tests (WP1), the validated models and scale-up tools developed (WP2) and the expertise of the involved partners in power and chemical plant engineering in general, as well as specifically in scale-up of new CCS technologies.
A slip stream of flue gas is taken from the existing flue gas duct downstream of the wet flue gas desulfurization (Wet FGD) of Unit 6 and is routed to the carbonator via a fan and a gas preheater. In the Carbonator the flue gas is contacted with CaO in a circulating fluidized bed, and the CO2 contained in the flue gas will reacts with solid CaO to CaCO3. A first cyclone separates the solids from the treated CO2 lean flue gas stream, which is sent back via a heat recovery system and a particulate filter to the flue gas duct of the host power plant. Loaded sorbent is transferred via a loop seal with cone valve for flow control to the calciner. In the calciner CaCO3 will be calcined in a fluidized circulating bed by means of coal combustion under moderated oxy combustion conditions. A first cyclone separates the regenerated sorbent from the CO2 rich flue gas. The calcined sorbent is returned for repeated CO2 capture to the carbonator via a loop seal with cone valve for flow control and a sorbent heat recovery system, which generates steam by solid cooling. A second cyclone limits solid entrainment to the downstream filters under normal operation and during plant upsets.
The CO2 rich flue gas is routed to a CO2 purification unit via a heat recovery system, particulate filter and a Selective Catalytic Reactor (SCR) reducing the NOx emissions. Within the CO2 purification unit the CO2 is enriched to >95 mol.-% CO2 purity. A small portion of the CO2 is dried and utilized for fluidization and inertization purposes. Since there is no further use of the remaining CO2 stream foreseen in this pilot project, the CO2 product is mixed with the treated flue gas stream from the Carbonator and routed via the flue gas duct and stack of the host plant to atmosphere.
Heat recovered from CO2 lean flue gas, CO2 rich flue gas and from the Sorbent Heat Recovery system is utilized to produce steam from boiler feed water (BFW) supplied from the host plant. The steam produced is used either inside the pilot plant, for coal drying or as fluidization medium, or exported to the infrastructure of the existing power plant. Coal is supplied from the host power plant coal yard. Before the coal is sent to the calciner it is dried and milled to the targeted particle size. Limestone sorbent for make-up is supplied from trucks to a hopper. From the hopper, sorbent is pneumatically transported to a feeder system and finally discharged to the calciner. Oxygen is supplied from tanks as this seems the most cost effective solution for pilot purposes. The oxygen is stored as a liquefied gas and evaporated before being fed to the process. Spent sorbent and ash separated by filters and cyclones are cooled and temporarily stored before being disposed
The nominal operation points for the 20 MWth pilot plant were defined and chosen in order to investigate crucial process parameters, as identified during pilot testing in WP1. With the CCL process model for the 20 MWth pilot plant, derived from the validated model developed in WP2, mass & heat balances for each of the selected eleven (11) operation points were created. The varied process parameters include for example carbonator temperature, calciner temperature, sorbent make-up flow, sorbent circulation flow, flue gas composition & flow to carbonator, oxygen concentration to calciner, Carbonator inventory, etc. Table 2 below shows main parameters resulting from the generated mass & heat balances for the design and engineering of the reactors and auxiliary systems.
Table 2: Main process parameters
|Flue gas flow to carbonator||10.0 – 17.5||t/h|
|Coal flow to calciner||1.0 – 1.8||t/h|
|Make-up sorbent flow||1.9 – 3.0||t/h|
|Sorbent circulation flow||22.7 – 48.9||t/h|
|Oxygen flow to calciner||2.0 – 3.8||t/h|
|Carbonator temperature||650 – 675||°C|
|Calciner temperature||900 – 950||°C|
|Carbonator inventory||1 – 1.5||t/m²|
Design and engineering of reactors and components
Based on the process definition and the developed mass & heat balances, the design of the reactor systems and auxiliary components was conducted. The core components of the 20 MWth pilot plant are the two coupled circulating fluidized bed (CFB) reactors. Different 3D CFD simulation models, developed within WP2, were used to predict and confirm reactor system performance and to optimize the geometry and operating conditions of the reactor components (see also WP2 description for more details). Based on the CFD models and operational experience, a superficial gas velocity of 5 m/s was selected for both carbonator and calciner reactors to achieve the targeted fast fluidized bed flow regime ensuring sufficient fluidization above the minimum fluidization velocity of the particles involved. This velocity resulted in a required cross-sectional area of both reactors of approximately 2.25 m² (square area of 1.5 m × 1.5 m). A height of 20 m was selected to achieve the required residence time of the particles for the carbonation reaction in the carbonator, as well as the calcination reaction and coal burnout in the calciner. Further, the height of both reactors is driven by layout requirements to provide the required height that will ensure both the gravitationally driven flow of solids through cyclones and loop seals back to the reactors and the adequate slope of piping to accommodate the angle of repose for the solids involved. Both reactors were designed to be made from refractory-lined carbon steel with a square cross-sectional area. Based on the 3D CFD model results it was concluded that the actual design is promising to reach the specified CO2 capture rate of 80 % for the Carbonator and of 90 % for the complete pilot plant. Besides the reactor systems, all auxiliary systems required to operate the pilot plant were designed, including the flue gas connections to the host power plant, the coal handling system, the sorbent make-up system, the oxygen supply system, the spent sorbent/ash handling system, the CO2 purification system, the heat recovery and filter systems as well as utility systems required. The 20 MWth pilot plant requires to be equipped with extensive measurement devices due to its pilot character to evaluate the CCL process for R&D purposes and for extending the validation of related tools to a larger scale. A detailed measurement plan with approximately 500 measurement services was elaborated focusing on process evaluation in the scaled-up pilot plant.
Normal operation, start-up and planned/emergency shut-down procedures, including control concepts, were defined based on the results from engineering and the experience from pilot testing in WP1. The work was supported by dynamic process simulation studying the dynamic behaviour of the 20 MWth pilot plant during start-up and shut-down and other major transient scenarios identified. The simulation tool was based on a validated 1 MWth dynamic process model.
Planning of logistics
Using available data on the amount and characteristics of consumables, utilities required and wastes produced, the logistics of the pilot plant were determined. Additional traffic for supply of consumables and for removal of wastes was evaluated as well as the availability of utilities from the host power plant. It was concluded that the traffic will increase by 8 to 14 vehicles per day depending on the pilot plant operation mode. Suitable tie-in points for provision of utilities from the host power plant-
Piping & Instrumentation Diagrams (P&IDs)
Based on the previous design and engineering work – like process configuration, equipment design, measurement plan and operating procedures – Piping & Instrumentation Diagrams (P&IDs) were prepared. The P&IDs form a set of drawings which depict the process scheme, type and material of process equipment, required process instrumentation, including analytical equipment and control loops, as well as required sizes and materials for major piping/ducts.
A plant layout plan and 3D CAD software model of the 20 MWth pilot plant was created to design and engineer the required arrangement of the different subsystems, equipment, and interconnecting piping of the pilot plant. It provides an overview of the dimensions and general arrangement of the 20 MWth CCL pilot plant integrated into the Emile Huchet power plant. It further supported cost estimate, permitting evaluations and risk assessments done in WP3. Uniper, the power plant owner, selected an appropriate plot area for the 20 MWth pilot plant close to the tie-in points to Unit 6. With the information about the plot area as well as process and equipment design requirements, a 3D CAD software model was developed with focus on the assembly of the carbonator and calciner reactor systems (CFB reactors, cyclones, loop seals and fluidized bed heat exchanger) as well as the arrangement of the solid circulation coupling between these two systems. Figure 2 shows a 3D model view and the developed layout plan of the 20 MWth pilot plant.
A Health and Safety Risk Assessment was carried out to identify potential health & safety risks by conducting a Process Hazard analysis with Hazard Study 1 methodology (HAZID). It was identified that some hazardous potential is associated, for example, with an inadvertent release of different process media like flue gas, natural gas or lime, which could cause harm to operators through the threat of asphyxia or irritations or cause an environmental pollution. Another risk is the handling of combustible media like coal or natural gas, which could potentially cause a fire or explosion. As a result, a risk mitigation plan was developed. Further, a Technical Risk Assessment was conducted to identify the potential technical risks by a Failure Mode & Effect Analysis (FMEA) considering experience from the erection and operation of the 1 MWth plant.
Generally, being a pilot plant the risk profile for the 20 MWth pilot plant is higher than for a commercial unit as expected since certain technology validation steps have not been executed yet. However, risks can be minimized my mitigation actions and no risks associated with the pilot plant have been identified that would be considered unmanageable. The risk assessments shall be reviewed, particularized and updated in subsequent project implementation phases.
Determination of costs
All information acquired was used to estimate the overall investment costs as well as operating and maintenance costs expected for the scaled-up 20 MWth pilot plant. The Capital Cost (CAPEX) was calculated using the “Total Installed Cost” (TIC) reflecting an accuracy of -25% / +30 %, based on actual cost (1st quarter 2017) having western European cost basis. Operating cost (OPEX) was calculated based on a five-year plant operation with an annual operating time of 2.000 hours for testing purpose. The maintenance cost was included in the OPEX and is based on experienced percentage per year based on CAPEX cost.
The CAPEX cost of the pilot plant considers the following:
- Equipment & bulk material (piping, electrical, instrumentation, spare parts, etc).
- Labour and subcontracts (construction, bulk installation, civil works, structural steel, buildings, insulation, painting, etc)
- Services (engineering, project management, procurement, temporary facilities, construction management & supervision, commissioning and start-up)
- Plant Integration (connections to battery limit, permitting, etc.)
The OPEX cost of the pilot plant considers the following:
- Personnel cost for operational and testing staff
- Cost for consumables (feedstocks, chemicals, utilities, waste disposal)
- Maintenance cost
Contingencies for CAPEX (20%) and OPEX (10%) are recommended to reach a high probability of underrun the cost. Table 3 gives an overview of CAPEX and OPEX cost estimated.
The cost data shown are to be considered specific for the pilot plant where relatively high costs are associated with high degree of instrumentation, high plant flexibility, high utility costs, local sourcing and R&D personnel cost. Thus, cost data shown should not be used for prorating to commercial units. Furthermore, economy of scale and value engineering efforts may result in lower cost for commercial CCL technology like further process optimization, reduction of margins for equipment design and less instrumentation, optimization of utility cost, international sourcing, etc.
Table 3: Estimated total cost for the 20 MWth pilot plant incl. 5 years of operation
|Base cost||Total Cost including contingency (w/o risk & profit)|
|CAPEX||53.0 million €||63.6 million €|
|OPEX||13.2 million €||14.5 million €|
|Total||66.2 million €||78.1 million €|
On completion of the preliminary permitting activities, it has been concluded that there are no unsurmountable issues to obtain the permit to operate the planned 20 MWth pilot plant.
The results of the pilot plant engineering activities give confidence to interested parties for investments into a larger-scale 20 MWth unit from a technical perspective. The results of WP3 do not reveal any significant or unsurmountable obstacles with regards to design, engineering, operational, logistical, safety or permitting aspects. Thus, the WP3 team is confident that the CCL technology could be erected and operated in a 20 MWth pilot to test and evaluate the characteristics of this technology at the next bigger scale in order to gain further knowledge and experience, eliminate potential problems, achieve required learnings and to enhance the technology.
CCL technology is a promising 2nd generation carbon capture technology, but must be evaluated and tested at larger scale before commercialization. CCL technology is very interesting for incorporation into smaller industrial applications (cement, steel), waste incineration plants or biomass power stations which would normally require a scale-up of the planned pilot plant by a factor of 3 to 5 only compared to the 20 MWth pilot scale. Existing infrastructure and other process equipment may be used, thus minimizing the expenditures for the total installation. This means commercialization could be realized in a reasonable time frame based on the knowledge gained on the operation of the 20 MWth pilot plant.