This report delves into the unique characteristics of dense phase carbon dioxide, the ideal type of pump for CO2 transport, crucial considerations in pump selection, and highlights leading companies providing cutting-edge solutions for efficient CO2 transportation.
Defining Dense Phase CO2
Dense phase refers to a fluid with high compressibility, displaying characteristics similar to both liquids and gases. Its viscosity is comparable to that of a gas, yet its density approaches that of a liquid. This unique combination makes it an advantageous medium for the transportation of carbon dioxide (CO2) in dense phase. In Carbon Capture and Storage (CCS), dense phase CO2 is efficiently transported from industrial sources to designated storage locations. This process is a key component in mitigating greenhouse gas emissions and combating climate change. Additionally, energy sectors around the world leverage dense phase CO2 transport for enhanced oil recovery (EOR) projects, contributing to the optimization of oil extraction processes.
These real-world applications underscore the significance of efficient and reliable dense phase CO2 transport in advancing environmental sustainability and economic efficiency. In this context, understanding the intricacies of the pumps involved becomes crucial for ensuring the success of these applications. This report will specifically focus on the pumps employed in the transport of dense phase CO2.
To begin, let's establish the conditions required to transition carbon dioxide, typically found in its gaseous state, into its dense phase state.
Carbon Dioxide Phase Diagram
The critical temperature of carbon dioxide (CO2) is 31.1 ° Celsius (304.25 Kelvin), and surpassing this temperature will transition CO2 from its dense phase to a supercritical state. The critical pressure for this transition is 7.38 MPa. Within the dense phase region, the density of CO2 rises as temperature decreases.
Certainly, various scenarios necessitate the precise specification of pumps to meet detailed operational requirements. This report will delve into the intricacies surrounding the transportation of dense phase carbon dioxide (CO2) through pipelines, addressing the unique considerations and specifications associated with this particular context.
Types Of Pumps for Transporting Dense Phase CO2
In the context of dense phase CO2 transport, reciprocating pumps and centrifugal pumps are the two main types of pumps used for the compression and movement of carbon dioxide. These pumps are expected to conform to the standards outlined by both the American Petroleum Institute (API) and the International Organization for Standardization (ISO).
Centrifugal Pumps (API 610/ISO 13709)
Principle of Operation:
Centrifugal pumps operate on the principle of forced vortex flow, which means when a certain mass of fluid is rotated by an external force, it results in an increase in pressure head. This increase in pressure head is used to move the fluid from one point to another.
Centrifugal pumps utilize a rotating impeller to transfer kinetic energy to CO2, converting it to pressure as the fluid is directed outward. Renowned for their seamless flow and uncomplicated design, these pumps are widely recognized in various applications.
Suitability:
Traditionally used for higher flow rates and lower pressures than reciprocating pumps, centrifugal pumps are the most common types of pumps employed in dense phase CO2 transport, especially when stringent pressure requirements are not essential.
They find widespread application in Carbon Capture and Storage (CCS) scenarios, involving the capture of CO2 from industrial processes and subsequent transfer to suitable storage locations. The preference for centrifugal pumps in CCS activities is attributed to their similarity to the technology employed in injecting natural gas liquids into production fields.
Types:
Single stage process pumps, single and multistage between bearings (both axially and radially split) (BB3 or BB5), double case pumps, integrally geared pumps
Advantages:
Characterized by continuous and smooth flow, a simple design, and suitability for higher flow rate applications. Centrifugal pumps are known for their high efficiency, which results in less power consumption compared to other types of pumps. This leads to significant energy savings, reducing operational costs and environmental impact. In the context of dense phase CO2 transport, using a centrifugal pump can save energy as less specific compression work is required.
Reciprocating Pumps (API 674/ISO 13710)
Principle of Operation:
Reciprocating pumps function through the back-and-forth movement of a piston or diaphragm within a cylinder. This reciprocating motion generates pressure differentials, enabling the pump to intake and compress CO2.
Suitability:
Reciprocating pumps excel in applications requiring high pressure and low flow rates. In dense phase CO2 transport, where the gas is pressurized to a dense, liquid-like state, these pumps effectively handle the compression process. Reciprocating pumps are infrequently employed for the transport of substantial quantities of carbon dioxide through extensive pipelines; however, they find utility in applications where the transportation demands involve low volumes and elevated pressure requirements.
Note: These pumps are particularly well-suited for systems that prioritize the efficient transfer of CO2 under conditions that necessitate high pressure but do not require the handling of large volumetric flows. It's important to note that reciprocating pumps, including piston and plunger pumps, are not typically employed in large-scale industrial transport of dense phase CO2. Their application is more focused on precision and reliability in scenarios where specific pressure requirements take precedence over high-volume conveyance
Types:
Piston Pump, Plunger Pump
Advantages:
Offering precise pressure control, well-suited for low flow and high-pressure scenarios, and capable of handling a broad range of viscosities.
Considerations when choosing the type of pump
The following should be considered when choosing the type of pump for dense phase CO2 transport.
Pressure Requirements:
Centrifugal pumps are widely favored for industrial transport of dense phase CO2 due to their versatility and ability to handle a broad range of pressure specifications. They excel in scenarios requiring moderate to high pressures, typically ranging from 0.1 MPa to 20 MPa. Their adaptability makes them a common choice in various applications.
In contrast, reciprocating pumps, such as piston and plunger pumps, are specifically suited for applications demanding exceptionally high pressures. They can achieve higher pressures compared to centrifugal pumps, with an operating range commonly extending from 3.45 MPa to 68.95 MPa. Reciprocating pumps shine in situations where substantial pressure is a critical requirement, and their efficiency makes them suitable for low-volume transport applications.
It's noteworthy that while reciprocating pumps excel in high-pressure applications, they are not the typical choice for large-scale industrial transport of dense phase CO2. Centrifugal pumps, with their versatility and efficiency, often take the lead in meeting the demands of such transportation, offering reliable performance across a range of pressure specifications.
Flow Rate:
Centrifugal pumps are generally more efficient for higher flow rate applications, making them suitable for scenarios where a continuous and substantial CO2 flow is required.
Common flow rate ranges for centrifugal pumps in dense phase CO2 transport typically fall between 0.38 m³/s and 1.26 m³/s, depending on the specific application requirements.
Reciprocating pumps, on the other hand, are effective in managing lower flow rates. These pumps may
have flow rate capacity up to 0.11m³/s.
Energy Efficiency:
The choice between reciprocating and centrifugal pumps may depend on energy efficiency requirements and the specific needs of the dense phase CO2 transport system. For example, in applications where energy efficiency is paramount, centrifugal pumps might be favored due to their continuous and streamlined flow characteristics. However, reciprocating pumps can be more energy-efficient in certain high-pressure and low-flow scenarios, offering advantages in specific operational conditions.
Material Considerations:
The corrosive nature of carbon dioxide is crucial in pump selection. Dense phase CO2, especially with impurities, can be corrosive. Pump components must be made of materials resistant to corrosion to ensure system longevity and reliability. Common materials for pump construction in CO2 applications include stainless steel, duplex stainless steel, and corrosion-resistant alloys.
The choice of sealing materials is critical, especially in reciprocating pumps. Seals and gaskets should be compatible with CO2 and capable of maintaining integrity under high-pressure conditions. Common materials for seals and gaskets in dense phase CO2 transport systems include fluorocarbon elastomers (e.g., Viton) and polytetrafluoroethylene (PTFE) due to their chemical resistance and durability.
Maintenance:
In the realm of dense phase CO2 transport, ensuring the reliable operation of centrifugal and reciprocating pumps demands distinct maintenance approaches. For centrifugal pumps, routine inspections are crucial, focusing on components like impellers, seals, and motor alignments. Regular lubrication and vigilance against vibration abnormalities help maintain optimal efficiency. In contrast, reciprocating pumps require periodic checks of pistons or plungers, valve maintenance, and inspections of diaphragms or packing. The drive mechanism and pressure relief valves demand close attention, along with instrument calibration.
While centrifugal pumps necessitate meticulous attention to alignments and impeller clearances, reciprocating pumps demand a focus on precision components and valving systems. The frequency and intensity of maintenance may vary, with centrifugal pumps typically needing more routine checks due to their continuous operation, while reciprocating pumps may require more precision-oriented inspections. The choice between the two types depends on specific operational needs and the trade-off between continuous operation and precision maintenance requirements.
Summary
In the context of large-scale transport of dense phase co2, especially in carbon capture utilization and storage, centrifugal pumps are preferred over reciprocating pumps. This is due to the following reasons:
1. Operating pressure compatibility: Reciprocating pumps boast capabilities for extremely high pressures, their utilization in dense phase CO2 transport may be excessive. The nature of dense phase CO2 applications often involves moderate to high pressures, making the versatility of centrifugal pumps more aligned with the specific requirements. Opting for reciprocating pumps with significantly higher-pressure capabilities than necessary may result in unnecessary costs and operational complexities, further emphasizing the practicality and efficiency of centrifugal pumps in this context.
2. Energy Efficiency: Centrifugal pumps, with their continuous and streamlined flow characteristics, are preferred in scenarios where energy efficiency is crucial. Reciprocating pumps may be more energy-efficient in specific high-pressure, low-flow conditions, offering advantages in certain operational contexts.
3. Flow Rate Efficiency: Centrifugal pumps are generally more efficient in managing higher flow rates, aligning with the continuous and substantial CO2 flow requirements in large-scale transport. Reciprocating pumps, while effective, are better suited for lower flow rate applications.
4. Cost Effectiveness: Centrifugal pumps are preferred over reciprocating ones for dense phase CO2 transport due to their cost-effectiveness, especially concerning the volume being transported. Centrifugal pumps offer efficient operation at a relatively lower cost when dealing with large-scale industrial transport scenarios. Their ability to handle substantial flow rates and maintain reliability across a wide range of pressure specifications makes them a more economical choice for projects where cost considerations are paramount. This cost-effectiveness contributes to the overall appeal of centrifugal pumps in applications involving the transportation of significant volumes of dense phase CO2.
Considerations for Centrifugal Pumps in Large Scale Dense Phase CO2 Transport
As explained in preceding sections, Centrifugal pumps, specifically those designed in accordance with API610 or ISO3709 specifications, find extensive application in large-scale CO2 transport scenarios. This section will delve into the specific subtype of centrifugal pump deemed optimal for such contexts. The information primarily stems from the tutorial presented by Ron Adams during the 43rd Turbo Machinery and 30th Pump Symposia, focusing on Dense Phase CO2 pumping and compression.
Thermodynamics of pump selection
Before we start let us define first the concepts and formulas that are used in choosing the type of pump.
We have learned in Thermodynamics that theoretically; pump operations are isentropic (constant entropy). In order for us to define states, the pressure-enthalpy diagram will be used. Choosing the right centrifugal pump will first require you to define the suction pressure, suction temperature and the discharge output. These values should be provided beforehand.
Pressure-Enthalpy diagram for CO2
Using the diagram, we will be able to determine three important values; Specific heat, Density and Specific Gravity. Directly obtaining the first two values from the chart, we will calculate increments by dividing the desired discharge pressure by five. Subsequently, we will compile a list for each of the three parameters, starting from the suction pressure to the discharge pressure, based on the determined increments. Finally, we will compute the mean for each parameter across the specified range.
The goal of this process is to ultimately determine the number of stages that are required in order to achieve discharge pressure. This will be done through a simple empirical formula for converting pressure into head:
Where: H = Head in meters
P = Pressure in Bar
SG = Specific Gravity
Source: engineeringunits.com and engineeringtoolbox.com
With this, it is evident that the head is dependent on specific gravity. The lower the SG the greater the head. Using the specific heat, we can also approximate the temperature rise in a pump:
Where: = Temperature rise in the pump in oC
q = Volume flow through pump m3/s
Ps = brake power in kW
cp = Specific Heat of the fluid in kJ/kgoC
μ = Pump efficiency
ρ = Fluid Density in kg/m3
This formula shows that the lower values for the specific heat will result higher temperature rise and lower pump efficiency.
We can approximate the number of stages using this formula:
Keep in mind that this formula is for approximation only. According to Ron Adams, in his pumping and compression of CO2 tutorial during the 43rd turbo machinery 30th pump symposia, when the suction temperature surpasses 38°C, both specific gravity and specific heat experience a decline. This decline implies that achieving the desired discharge pressure demands a significantly higher head, leading to the need for more stages or an increase in the pump's rotational speed.
The lower specific heat worsens the impact of pump inefficiency, resulting in a more substantial temperature rise. While this may not be a critical concern, it does contribute to a slight reduction in the average specific gravity. In the realm of pump applications, insights collected from numerous instances advocate for a cooling approach, specifically cooling the system to a temperature range of 27 to 32°C, whenever practical.
This cooling strategy serves multiple purposes. Firstly, it maximizes density, enhancing the overall efficiency of the pump. Additionally, it plays a role in reducing the number of stages required, optimizing the pump's design for improved performance. Furthermore, cooling helps diminish the heat of compression, contributing to better operational conditions. Lastly, the cooling process aids in preserving and enhancing the specific heat of the fluid, further promoting efficiency in the pump's operation.
He also stated that in the case of very high discharge pressures the initial approach will be the same. Utilizing isentropic fluid data at both the inlet and outlet is crucial in determining the mean density for the selection of an appropriate pump. This data helps establish the baseline conditions for fluid behavior, allowing for informed decisions in pump choice. A critical consideration involves checking for potential increases in inlet temperature due to the return of balance line fluid in the suction. This aspect is particularly important in situations involving lower flow rates or pumps with very high heads, where efficiency tends to be lower, and temperature rise due to inefficiencies is more pronounced.
Pump Rotor Construction and Bearings
Dense phase CO2 is not a good lubricant. It has a very low surface tension and the viscosity of a light hydrocarbon. Galling predominantly occurs in metal surfaces that experience sliding contact with each other, particularly in instances where there is insufficient lubrication present between the surfaces. Rotor should be designed to prevent contact during operation.
As mentioned in the previous sections, the most common type of pumps that are employed in large scale CO2 transport is the API 610 pumps. Particularly in North America, the most common multistage pump type with center bushing and throttle bushing for rotor axial balance and rotor dynamic stability is the API 610 type BB3 pumps. The adoption of a back-to-back rotor stack configuration in API 610 type BB3 pumps serves the purpose of mitigating axial thrust load. This design modification is instrumental in enabling the use of fan-cooled ring oil-lubricated sleeve radial/ball thrust bearings. The simplicity of this setup is advantageous, particularly for pipeliners who prefer avoiding a lubrication system whenever possible, provided the power level and pump design permit such a configuration.
When dealing with higher pressures, the recommendation is to employ API 610 Type BB5 radial split barrel pumps. These pumps are specifically designed to handle the challenges associated with elevated pressure conditions, ensuring reliability and optimal performance. While the inline rotor stack presents itself as a cost-effective option, a cautious approach is advised. Before implementing an inline stacked rotor, it is crucial to thoroughly examine rotor dynamics, particularly when worn clearances are involved. To address any uncertainties regarding stability with worn clearances, the practical choice is to opt for a Back-to-Back rotor stack configuration.
In instances where high-energy pumps or those with an inline rotor stack, such as in API 610 type BB5, are in use, there might be limited options regarding bearing choices. Hydrodynamic radial and thrust bearings become a necessity in such cases, demanding the implementation of a comprehensive bearing lubrication system to ensure optimal performance and longevity. It's worth noting that the incorporation of Sleeve/Pivot Shoe bearings, instrumentation, and a lubrication system can introduce additional costs ranging from $100,000 to $200,000. This financial consideration underscores the importance of careful decision-making in pump design, bearing selection, and the overall configuration, as it directly impacts both functionality and project economics. The added expenses associated with these components highlight the need for a balanced approach that takes into account performance requirements, operational conditions, and cost considerations in pump design and implementation.
Non-metallic wear parts, such as those made of Carbon or PEEK, are commonly used in these centrifugal pumps. This choice of materials enhances wear resistance and durability, contributing to the longevity and efficiency of the pump components. Notably, Ron Adams mentioned that there is a wealth of practical experience in the field of Ethane-Propane Mix and Propane pipeline applications, where multistage pumps have been successfully operational for over 30 years. Operating within a specific gravity range of 0.4 to 0.55 these pumps have demonstrated resilience and reliability over an extended period. Furthermore, the wear parts in these applications often feature non-galling metals matched with hardened 12% chrome, further ensuring durability and longevity in challenging operating conditions.
Mechanical Seals
The adoption of gas seal systems has become commonplace, particularly for supercritical CO2 applications. However, it's crucial to recognize that seals effective at temperatures below critical temperature for CO2 may face challenges at higher temperatures. Therefore, close collaboration with seal manufacturers is imperative.
When engaging with seal manufacturers, providing detailed information about the gas constituents is crucial. Even minor components like nitrogen and methane can significantly impact pump and seal performance. Additionally, specifying the suction temperature range, suction pressure range, rpm range, and shaft size is essential. All these parameters can influence the selection and performance of seals.
Furthermore, it is advisable to inquire about the required seal flush flow and pressure for each seal. Given that most CO2 pumps incorporate two seals primary ring and secondary ring, the combined flow must be added to the rated flow for the necessary number of stages to achieve the seal flush pressure. This holistic approach ensures proper seal performance and helps adjust the pump power requirements accordingly.
What’s Next?
Pioneering advancements in dense phase CO2 transportation involve cutting-edge pump technologies developed by industry leaders. Notably, Sulzer, a frontrunner in pump manufacturing, has been utilizing multistage pumps over the last three decades to efficiently transport compressible, dense phase ethylene and CO2 at both normal and supercritical pressures. Their innovative products, such as the CP (Centrifugal Pump) horizontal radially split multistage barrel pump and the GSG diffuser style barrel pump, have found applications in demanding environments, including high-pressure oil production and high-temperature refinery processes.
In addition to Sulzer, ITT Brands stands out for its contributions to CO2 capture, transportation, and storage. Renowned brands under the ITT umbrella, such as Goulds Pumps, have demonstrated expertise in meeting the challenges posed by dense phase CO2 applications. These innovations collectively highlight the industry's commitment to advancing pump technologies for enhanced efficiency and reliability.
Looking ahead, the future of dense phase CO2 transport points towards an increased reliance on this medium for enhanced oil recovery (EOR). The low viscosity and high diffusion coefficients of dense phase CO2 make it particularly advantageous for optimizing oil recovery processes. Furthermore, the transportation of CO2 in its dense phase is expected to rise due to its higher density, coupled with the added advantage of preventing liquid formation in the pipeline. This upward trajectory in demand is likely to drive the development of even more efficient and specialized pumps tailored to meet evolving requirements in dense phase CO2 transport.
Challenges and Solutions in Dense Phase CO2 Transport
Despite the benefits of dense phase CO2 transport, challenges exist, especially concerning impurities that can compromise pipeline integrity. For instance, the presence of water can lead to pipeline corrosion, emphasizing the need for effective impurity removal before transportation. Common methods include the use of mol sieves or glycol dehydration, complemented by coalescers and filters to safeguard dehydration units. Additionally, the aging or repurposing of pipelines may lead to the accumulation of pipe scale and corrosion, resulting in particulate contamination of the CO2. This concern necessitates the use of preventative measures, such as coalescers and filters, to protect essential equipment like control valves, metering stations, and high-pressure pumps and compressors.
Leading Companies that offer API 610 and API 674 Pumps
Sulzer
Sulzer stands as a distinguished global leader in fluid engineering and chemical processing applications, boasting a legacy of excellence dating back to 1834. Specializing in energy-efficient technologies, Sulzer provides cutting-edge solutions for pumping, agitation, mixing, separation, purification, crystallization, and polymerization across diverse fluid types.
Locations:
Neuwiesenstrasse 15, Winterthur, 8401, CH
Vasamakuja 1, Vantaa, Southern Finland 01740, FI
344 South Pine Rd, Brisbane, QLD 4500, AU
Contact Number: +41 522623000
Website: www.sulzer.com
Ruhrpumpen
Ruhrpumpen specializes in the design, manufacturing, and servicing of highly-engineered and standard pumping solutions across diverse industries, including oil & gas, power generation, industrial, water, and chemicals.
Locations:
San Pedro Garza Garcia, Nuevo Leon, MX: Torres Martel, Torre IV, Piso PH, Prolongación Los Soles 200, Col. Valle Oriente, San Pedro Garza Garcia, Nuevo Leon 66269, MX.
Witten, DE: Stockumer Straße 28, Witten, 58453, DE.
Garcia, Nuevo Leon, MX: Niquel 9204 Parque Industrial Mitras, Garcia, Nuevo Leon 66000, MX.
Rio de Janeiro, BR: Rodovia Washington Luiz, 13.721, Chácaras Rio-Petropolis, Duque de Caxias, Rio de Janeiro 25230-005, BR.
Contact Number: +44 (0) 1273 956-410 (UK), +49 2302 66103 (Germany)
Website: www.ruhrpumpen.com
Flowserve
Flowserve stands as one of the world's largest manufacturers of pumps, valves, and seals, boasting a global workforce of over 16,000 employees spread across 50 countries. The company's strength lies in its rich heritage, built on more than 50 world-renowned brands, earning equity and customer loyalty over the past 230 years. This foundation has propelled Flowserve to a leadership position worldwide.
Locations:
Irving, Texas, US: 5215 N. O'Connor Blvd., Suite 2300, Irving, Texas 75039, US.
Arnage, Loire Region, FR: 13 Rue Maurice Trintignant, Arnage, Loire Region 72230, FR.
Ecatepec de Morelos, MEX: Avenida Via Jose Maria Morelos 437, Ecatepec de Morelos, MEX 55540, MX
Contact Number: (972) 443-6500
Website: www.flowserve.com
ITT Goulds Pumps
ITT Goulds Pumps stands as a leading global manufacturer of pumps, catering to diverse industrial markets such as oil & gas, mining, chemical, power generation, pulp & paper, and general industry.
Location(s):
Seneca Falls, New York, US: 240 Fall Street, Seneca Falls, New York 13148, US.
Contact Number: +1 315 568 28111
Email: press@itt.com
Website: www.gouldspumps.com
Trillium Flow Technologies
Founded in 2019, the company is committed to providing mission-critical valves, pumps, and aftermarket services across diverse sectors, including oil and gas, power generation, water and wastewater, and general industry.
Location(s):
Hongqiao Wantong Center Room 307, Block C, Building 1, No.333 Suhong Road, Minhang District, Shanghai 201106, China
945 Bunker Hill Road, Suite 250, Houston, Texas 77024, USA
Phone Number: +86 21 648878981 (China), +1 832 200 62201 (US)
Email: info@trilliumflow.com
Website: www.trilliumflow.com
References:
Campbell, J. M. (2012). Transportation of CO2 in dense phase. Retrieved from https://www.jmcampbell.com/tip-of-the-month/2012/01/transportation-of-co2-in-dense-phase/
ResearchGate. (n.d.). Phase diagram for pure CO2. Retrieved from https://www.researchgate.net/figure/Phase-diagram-for-pure-CO2-In-the-supercritical-region-CO2-no-longer-exists-in-distinct_fig1_335637324
IOP Science. (n.d.). Design overview of high pressure dense phase CO2 pipeline transport in flow mode. Retrieved from https://iopscience.iop.org/article/10.1088/1755-1315/310/3/032033/pdf
Made-in-China.com. (n.d.). API 610 Bb5 High-Pressure Barrel Pumps Power Plants, Refineries, Petrochemical Plants. Retrieved from https://www.made-in-china.com/
Linquip. (n.d.). Working principle of a centrifugal pump. Retrieved from https://www.linquip.com/blog/working-principle-of-a-centrifugal-pump/
Pump Industry Magazine. (n.d.). Carbon capture and storage: the re-emergence of a critical technology. Retrieved from https://www.pumpindustry.com.au/
Goulds Pumps. (2021). CO2_2021.pdf. Retrieved from https://www.gouldspumps.com/
Rotech Pumps. (n.d.). Centrifugal Pumps: Advantages vs. Disadvantages. Retrieved from https://www.rotechpumps.com/
TWI Global. (n.d.). Selection of materials for high pressure CO2 transport. Retrieved from https://www.twi-global.com/
John Crane. (n.d.). Sealing Supercritical CO2 Applications. Retrieved from https://www.johncrane.com/
IIETA. (n.d.). Influence of Dense Phase CO2 Pipeline Transportation Parameters. Retrieved from https://www.iieta.org/
H&TECH. (n.d.). Retrieved from https://www.iieta.org/
TAMU. (n.d.). Case Study P6: CO2 Pipeline Pump - Pressure Pulsations, Vibrations, Seal Failures - Solution with the Help of Remote Monitoring. Retrieved from https://www.tamu.edu/
Long Video: https://www.youtube.com/watch?v=XlGSWrqwm18&t=2s
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