Background

Carbon Dioxide is an inevitable product of fossil and bio-fuel combustion and a by-product of many industrial processes. Throughout the early industrial age and most of the previous century, the general practice was to dispose exhaust gases from combustion equipment and processes generating Carbon Dioxide by venting to the atmosphere. It was only about thirty years ago that the linkage of Carbon Dioxide emissions with global warming was formally recognized under the UN Framework Convention on Climate Change (IPCC). In the contemporary world, global warming due to Greenhouse Gas emissions has been identified as a major existential threat. There is global consensus on achieving Net Zero Carbon Emissions (NZE) by the year 2050. In practice, the strategy to achieve the NZE Carbon reduction goal almost exclusively targets Carbon Dioxide emissions. The most impactful and technologically mature solution for Carbon Dioxide mitigation, at this time, is Carbon Capture, Utilization and Sequestration (CCUS).

It is worth noting that the acronym CCUS encompasses two distinctly different concepts, namely CCU (Carbon Capture and Utilization) and CCS (Carbon Capture and Sequestration). While the sources of Carbon Dioxide and Capture methodologies are similar, CCU views Carbon Dioxide as a resource to be  productively utilized in industrial processes and products. CCS on the other hand, envisages permanent disposal of captured Carbon Dioxide in deep  underground formations.

There are only two well established and globally significant examples of industrial CCU processes. These are:

  • Urea Production by reacting Carbon Dioxide with Ammonia

Commercial Urea production commenced more than a century ago. Urea is the most important Nitrogenous fertilizer in the world, and its global production has been constantly increasing to keep pace with growing populations.

  • Enhanced Oil Recovery (EOR)

The use of Carbon Dioxide injected into depleted Oil reservoirs for enhancing recoveries, has been known since the 1960s. It works on the principle that Carbon Dioxide, when injected into Oil reservoirs, under the right conditions, is miscible with certain Crude Oils, forming low viscosity, low surface tension fluids, The Carbon Dioxide also displaces residual oil trapped in small rock pores. The low viscosity, displaced Oil is then flushed out by injected Water.

Though achieving CCU goals was not an initial objective in the development of Urea and EOR  sectors, it is now acknowledged that they have played an appreciable role in mitigating Carbon Dioxide emissions. However, meeting the 2050 NZE goals needs much more Carbon disposal capacity than what these sectors can offer. This is because Urea capacity additions are market-driven and decided by supply-demand economics. Similarly, EOR is implemented only as a tertiary recovery mechanism in suitable reservoirs, limiting its potential as a Carbon sink.

In contrast to CCU, the CCS sector is driven by regulatory requirements, investors and societal stakeholders. Given a favorable regulatory and ESG framework, CCS projects can be rapidly deployed around the world, to mitigate Carbon Dioxide emissions from the biggest industrial sources. Technical and economic assessments suggest that over the coming century, CCS alone may contribute up to 20% of Carbon Dioxide emission reductions. This is equivalent to reductions expected from efficiency improvements and large-scale deployment of renewable energy resources [1].  Figure 1 illustrates the major industrial sectors where CCS can make a significant impact. Thus, the CCUS concept, combining the existing capabilities of CCU with the emerging potential of CCS, is very significant for achieving global sustainability goals.

Figure 1

Challenges in CCUS Compression

Compressors represent the “heart” of all CCUS processes since their job is to continuously “pump” Carbon Dioxide from low pressure emission sources to high pressure destinations. Both CCU and CCS involve dealing with Carbon Dioxide at supercritical conditions.

High pressure compression of Carbon Dioxide poses many technical challenges, specifically in the CCUS context. These challenges are common to CCU and CCS compressors. The only difference is that, in the case of CCS, volumetric flows are typically much larger than for CCU applications, which makes power consumption a major issue.

The main challenges relating to design of process systems, compressors, control systems, operation and maintenance are elaborated in the following paragraphs. The focus is on centrifugal compressors, which are used in the majority of CCUS installations worldwide. Please note that the challenges listed below continue to be areas of significant research and development in academia and the compressor industry.

Process Design Challenges

Compression of Carbon Dioxide to Supercritical Pressure

The critical point of Carbon Dioxide is 31.1 0C (87.9 0F) and 73.8 Bara (1070.4) psia. The  pressures and temperatures for all CCUS application are all beyond the critical point. In Urea applications, Carbon Dioxide pressures range from 150 bara to 200 bara while both EOR and CCS typically operate in the 100 bara to 150 bara range.

At supercritical conditions, Carbon Dioxide is no longer a gas but a dense phase fluid with properties somewhere between gas and liquid phases. Process design, for compressors and associated sub-systems like intercoolers and control valves, requires accurate knowledge of fluid properties within the design envelope of the system. For gas compression systems operating in sub-critical conditions, there are many established Equations of State and correlations that accurately compute the required properties. This unfortunately is not the case for supercritical Carbon Dioxide. There is currently no method that can accurately predict dense phase Carbon Dioxide properties. Additional components in the gas such as Water, Nitrogen, Methane and Hydrogen Sulphide if present, increase the likelihood of errors. For example, Figure 2 illustrates the uncertainty in predicting gas density for super-critical Carbon Dioxide by various standard Equations of State and correlations [2]. Gas density is a key property for compressor system design.

Figure 2

The uncertainty about properties also introduces a risk of liquid Carbon Dioxide formation during compression. Figure 3 illustrates this risk, at the higher pressure ranges near the critical point [3].

Figure 3

High pressure intercooler operating conditions near the critical point must be precisely selected so that suction conditions at each stage are sufficiently away from the Carbon Dioxide dewpoint curve. The presence of impurities including Water, Nitrogen, Methane, Hydrogen Sulphide, increases the risk due to inaccuracies in phase envelope prediction.

CCUS applications involve large, expensive compressors with power requirements of several MW. Uncertainty on properties introduces a risk of fatal design errors. Reputed compressor vendors with decades of experience this field have done extensive research to mitigate these risks. Aligning theory with practice and experience is key to mitigating these risks.

Moisture-Holding Characteristics of Supercritical Carbon Dioxide

Carbon Capture systems mostly use aqueous Amine based solvents, which results in Water saturated Carbon Dioxide. Water, being polar, has more affinity for a polar molecule like Carbon Dioxide than for example, non-polar Methane. Hence relatively more Water tends to stay in the Carbon Dioxide Gas phase. Especially beyond the critical point, the Water holding capacity of Carbon Dioxide steeply increases.

Figure 4 shows the Water saturation capacity of pure Carbon Dioxide at two temperatures [4]. It can be observed that Water saturation  steeply increases beyond the critical pressure (1070.4 psia). In fact, this characteristic of Carbon Dioxide is used to knock-out free Water in the subcritical compression region, saving on dehydration unit expenses. The shape of the curve ensures that Carbon Dioxide remains undersaturated with moisture in the supercritical region, under normal CCUS operating conditions.

Figure 4

In the case of  CCS projects with long pipelines, at low ambient temperatures that cause fluid cooling below the dew point, high Water content is a serious problem. It can cause corrosion of Carbon Steel, Carbon Dioxide hydrates, as well as slugging.

From the perspective of centrifugal compressor design, high Water content has been known to create hydrate problems due to Joule-Thomson cooling and condensation across the recycle valve, especially during start-up. Methanol injection usually resolves this problem.

The key point is that the risk of moisture condensation must be carefully considered during compressor system design, for all operating and upset scenarios. Mitigative measures may include dehydration units, Methanol injection, heat tracing and insulation, corrosion resistant metallurgy and operating procedures.

Corrosivity of Wet Carbon Dioxide

Carbon Dioxide and condensed Water form extremely corrosive Carbonic Acid, which reacts with Iron to form Ferrous Carbonate (FeCO3), liberating Hydrogen. The overall reaction can be represented as:

Fe + CO2 + H2O ———–> FeCO3 + H2

At temperatures above 60 0C, if Water is not strongly acidic, protective FeCO3 scale may form. However, in CCS, the high partial pressure of Carbon Dioxide, temperatures below 60 0C and low pH of the Water phase (< 4) do not allow protective scale formation and corrosion rates of  Carbon Steel are very high [5].

The compressor and sub-systems in contact with process fluid are therefore constructed from corrosion resistant materials, typically Stainless Steel 316L. However, this may not be economical for long pipelines and Carbon Steel pipelines  have been used after dehydration of Carbon Dioxide or otherwise  eliminating  the risk of Water condensation.

Carbon Dioxide Hydrate Formation

In the presence of free Water, under suitable pressure and temperature conditions, Carbon Dioxide will form stable Hydrates. This can happen at any location in the flow system, including downhole. Increase in flow resistance is typically the first sign of Hydrate formation and prompt Methanol injection may prevent a shutdown. This is one of the scenarios which  the control system designer must consider. The presence of impurities will affect the hydrate formation conditions. Figure 5 shows the Hydrate phase equilibrium curve for pure Carbon Dioxide and also the effect of impurities in enlarging the hydrate zone [6].

Figure 5

Integrated Control Systems For CCUS

Unlike Urea manufacturing, which is typically part of a single fully integrated and centrally controlled Ammonia-Urea facility, EOR and CCS applications are quite diverse. Control and safeguarding systems for each EOR and CCS project must be based on comprehensive analysis of various operating scenarios, including start-up, shutdown and upsets.

As discussed earlier, blockage due to hydrates is an example of a process deviation which may cascade into compressor trip on high discharge pressure or cause a centrifugal compressor to surge. Similarly, loss of inflow from the upstream Carbon Dioxide source needs consideration of suitable turndown capabilities.

In the case of EOR, impurities such as Hydrogen Sulphide and Methane increase the hazard level and criticality of control systems. Start-up scenarios may involve utilizing a start-up gas such as fuel gas or Nitrogen, which the compressor must be able to handle. Subsequent venting of non-condensables in the circuit is also part of the start-up procedure that the control system must handle.

Large compressors cannot be allowed to trip frequently. Published case-studies of EOR and CCS projects are available, which provide a wealth of information on control system aspects.

Machinery design Challenges

Rotor Dynamic Stability

Due to the high gas density and discharge pressure and large size of  a  centrifugal compressor, its rotor vibrations tend to increase, particularly sub-synchronous vibrations [7]. Generally, impeller natural frequency decreases when fluid density increases. Hence at supercritical conditions, the risk of impeller resonance increases. This limits the maximum head developed in any impeller, which leads to specifying 6 to 10 pressure stages for CCUS applications. In the case of integrally geared compressors, the rotor dynamic analysis is more complicated due to multiple shafts and impeller speeds. Though it adds to the cost, it is advisable to conduct rotor dynamic stability test as part of the complete string test before shipping the unit.

Sealing Systems

Issues related to seal integrity can be traced to seal design as well as material degradation during service. Though a lot of attention is normally given to compressor shaft sealing, in the case of wet supercritical Carbon Dioxide, there are significant material degradation concerns. From this perspective, the following sealing components need thorough evaluation:

  • Compressor shaft seals
  • Compressor casing head cover seals
  • Anti-surge valve stem seals
  • Pressure safety valve seals

Maintenance Challenges

Moisture and Liquid Related Problems

Due to the Water holding capacity of Carbon Dioxide, the following issues have been observed [8]:

  • Erosion of compressor blades and inlet guid vane due to droplet impact.
  • Scaling due to salt deposits on the blades, from entrained Water.
  • Corrosion of compressor components, again due to free Water.

All these can be addressed by ensuring that inlet and interstage scrubbers and intercoolers are generously designed with adequate factor of safety. Unfortunately, in practice, vendors try to make the scrubbers as well as the intercoolers smaller, to reduce footprints and costs. The buyer must therefore be aware of the risks that potential entrainment of liquids from scrubbers poses to the compressors.

Proper Layout To Ensure Maintainability.

Layout of equipment and piping should ensure ease of maintenance, including replacement of impellers and other critical components. It is desirable to select the compressor model early in the project engineering cycle, so that sufficient vendor supplied details are available to do the layouts. Standardized skid designs must be evaluated from the perspective of maintainability.

Compressor Selection for  CCUS

Overall Approach

The main considerations for CCUS Compressor selection are:

  • Capability to deliver the required flow rates, and pressures. The entire operating range over the lifetime of the project, including start-up scenarios, needs consideration. In cases of changes in molecular weight, the impact on operating envelope must be evaluated.
  • Power consumption/Energy consumption is the main component of OPEX and should be minimized, as it impacts project financial viability.
  • Compressor capacity control and turndown range using various capacity control provisions including recycle valves, clearance pockets, inlet guide vanes, variable speed drives is an important factor in compressor selection. The assembly must maintain rotodynamic stability and vibration free operation for each stage, while delivering the required flows and pressure across the range of gas densities.
  • Seamless, stable operation of the combined compressor-driver assembly over the compressor operating range is necessary. Driver selection may be decided by project specific considerations such as availability of utilities.
  • Minimizing the footprint is important especially for offshore applications, as this reduces the overall weight of the structure. Even onshore, cost of associated civil and structural works decreases if the footprint is smaller.
  • Maintenance and reliability aspects such as failure of seals, bearings, corrosion and scaling damage are all aspects that must be avoided by proper vendor selection and following proper design standards.
  • Proven Track record in similar service is important. This is true especially for CCS, which is a relatively recent area, with only a handful of commercial reference projects.

Specific Compressor Type Options For CCUS

The choice of compressor type is dictated by the required flowrates and pressures. On this basis as illustrated in Figure 6, the choice for CCUS applications, namely Urea, EOR and CCS narrows down to  the following three types:

  • Reciprocating
  • Centrifugal (Single shaft, barrel type)
  • Centrifugal (Integrally geared)

Please note that Figure 6 is a general recommendation, and  each project must be evaluated on a case by case basis. For example, the operating range for which integrally geared compressors are recommended  can also be delivered by single shaft centrifugal compressors. In making the final selection, many other factors come into play as mentioned earlier, such as turndown, power consumption, variable speed capability, driver compatibility, reliability, maintainability, CAPEX, footprint.

Reciprocating compressors have been around for much longer than centrifugal compressors, primarily because of the experience gained with nineteenth and early twentieth century reciprocating engines. Urea plants in the early twentieth century were built using reciprocating compressors for Carbon Dioxide compression. However. the advent of world -scale Urea plants made reciprocating compressors unviable due their flow rate limitations and reliability issues.

A similar pattern is observed in the EOR sector, where the pioneering projects were small in scale. The risk of failure in EOR is high, hence scale-up is done only after pilot projects have proved successful. Eventually, with experience and better design tools, the EOR sector has been implementing projects with larger Carbon Dioxide flowrates for which centrifugal compressors are more suitable.

Figure 6

Due to their predominance in CCUS applications, the focus of this section is on the two centrifugal compressors, namely single shaft and integrally geared types.

Centrifugal Compressors

Due to the high molecular weight and densities at supercritical conditions, CCUS application require centrifugal compressors with a large number of compression stages,  typically ranging from 6 to 10. A compression stage refers to the area of compression between two consecutive nozzles, namely the suction and discharge nozzle of that stage.

Single Shaft Multistage Compressor

This type of compressor can have a horizontally split or vertically split casing. Due to the high pressures involved, vertically split compressors, also called barrel type, are the recommended option. They are called barrel type, since the casing looks like a heavy cylindrical barrel with flanged ends. Several process stages can be included in the same casing. Figure 7 illustrates a barrel type of compressor.

Figure 7

Integrally Geared Centrifugal Compressors

The other option for CCUS applications is the integrally geared compressor. These are multi-shaft machines. Several pinion shafts with one or two impellers each are arranged around a central bull gear. For each pinion shaft, an optimum shaft speed and impeller size can be designed. Each impeller can be fitted with adjustable inlet guide vanes in front. Inter-stage cooling of the gas stream can be done after each impeller discharge. The combination of these features allows for high volume flows, outstanding energy efficiency even under part load, all in a compact design. Figure 8 is a representative picture of an integrally geared compressor [9].

Figure 8

Drivers and Auxiliary Systems

Apart from the compressor, the following equipment and sub-systems are equally important in the design of any compression system:

  • Driver
  • Shaft-Sealing system
  • Control system
  • Lubrication system
  • Intercoolers
  • Scrubbers

Drives for Compressors

Compressor Drivers  can be steam turbines, motors or gas turbines. Driver selection is influenced by several factors as elaborated in the following paragraphs.

Steam Turbine

Steam turbines utilize high pressure superheated steam to rotate the turbine which drives the compressor. In the process of doing work on the turbine, superheated steam expands to a lower pressure. In extraction type steam turbines, the steam is  extracted at an appropriate utility steam header pressure, to be used elsewhere as process steam, for  example in Amine reboilers within the Carbon Capture Unit. Alternatively in condensing turbine mode, the expanding steam is allowed to reach the lowest possible pressure and then  condensed under vacuum for removal by a condensate pump. This allows maximum extraction of mechanical power. The main advantages of steam turbines are as follows:

  • Steam turbines can readily be speed matched to the compressor.
  • They are known to be reliable and simple machines when compared  to gas turbines for mechanical drive applications.
  • Where steam infrastructure is available as in Urea plants, steam turbines avoid the need to invest in high voltage electrical infrastructure needed for electric motors.

Electric Motors

Electric motors are an environmentally cleaner source of power than steam or gas driven compressors. Since the global energy trend is to move towards electrification using renewable power, there may be sound reasons to use electric motors for the compressors in a CCUS Plant to reduce the Carbon footprint. However, the following points should be noted:

  • There must be a source of reliable high voltage power in the neighbourhood of the project which can supply the electrical power needs of the CCUS project. The on-site investment in electrical infrastructure will also be significant. Obviously for CCUS projects implemented at power plants, this should be easy, though the CCUS compressors constitute a high parasitic load on the generated power diminishing the power export capability.
  • In the case of CCS installations at chemical process plants, please note that CCS compressors are typically in the 5 to 20 MW range. Since power costs are a major part of most process plants this adds significantly to the overall operating costs.
  • Reliability is an important factor, since high voltage motors are allowed only a linted number of trips, to avoid damage to the motor. A high voltage motor trip or restart  can destabilize the grid and initiate  a major shutdown. Hence the electrical system must be designed to handle these scenarios.
  • Matching of load-torque characteristics of the electric motor over the entire operating range of the compressor is not always possible in CCS and EOR applications, due to inherent  uncertainties in the process.
  • Electric motors, whether speed controlled or not, are either asynchronous or synchronous in design. Speed variations introduce additional complications in matching the motor and compressor. It may not be possible to rely on variable speed alone and  supplementary capacity control measures must be in provided for the compressors.

Gas turbines

In oilfield  applications such as EOR, since fuel gas is generally available at site, gas turbines may be the preferred driver for compressors. Gas Turbines currently burn fossil fuels, which result in additional Carbon Dioxide emissions that must be captured and injected with the main CCS process stream. This increases the size of equipment and cost of the project.

Gas turbines are also associated with relatively high CAPEX and OPEX. Further they are usually in standard frame sizes which may not exactly match the CCUS process and compressor requirements. Despite these disadvantages the gas turbine is widely used in offshore Oil and Gas installations, because of its relatively better  power-to-weight ratio and availability of fuel gas. It is quite popular for use in remote locations where steam and electrical infrastructure  is not available.

Overall, electric drives or steam turbines if feasible are preferred for CCUS applications due to their lower Carbon footprint and costs.

Sealing systems

Provision of suitable shaft seals has always been a challenge in high pressure Carbon Dioxide compressors. Oil seals tend to fail due to the effect of dissolved Carbon Dioxide at high pressure. Tandem Dry gas seals represent the state of art for this application. However due the gas density and high pressures with multiple stages, there are many special feature in the dry gas seal design. Hence only vendors with the requisite experience in this application should  be considered.

Control System

Surge protection and capacity control are two important aspect of all centrifugal compressor control systems. EOR and CCUS applications can throw-up unexpected operational scenarios which required to be handled by the compressor system.

Surge refers to the situation in a centrifugal compressor, caused by flow reduction to a point where its operation becomes unstable. In the surge region, flow separates from the compressor blading, and the impeller cannot develop the required pressure. Consequently, high pressure gas flows back from the discharge till the situation reverses. This rapid and repeated flow reversal is termed surge and will destroy the compressor. The surge line is always shown on every centrifugal compressor characteristic curve. The compressor anti-surge control system senses the approach to surge and causes a quick acting recycle valve to open, ensuring that flow through the compressor does not fall below the surge line.

Capacity Control is important in EOR and CCS application due to the possibility of variations in flow of Carbon Dioxide from upstream sources and also unpredictable changes in flow resistance in the injection system.

The following capacity control methods are all typically incorporated into the control system design.

  • Inlet Guide Vane.
  • Variable speed drive.
  • Recycle valve.

There will also be synchronization with the injection wellhead choke valve, or the injection flowline pressure.

Lubrication system

Lubrication is a fundamental requirement for all compressors unless they use an alternative form of bearings such as the magnetic bearings. The forced feed lubricating system required for large compressors are quite complex, with many components. Apart from lubrication, in some cases, seal oil and control oil are also supplied from this system. Standard system requirements are available in API Standard 614, “Lubrication, Shaft-Sealing, and Control Oil Systems for Special-Purpose Applications” .

A basic lube-oil system comprises a reservoir, pump, cooler, filter, control valves, relief valves, pressure and temperature switches, gauges, and piping. Heaters should be considered for the lube-oil reservoir as applicable. The oil is pumped from the reservoir, cooled, filtered, pressure controlled, and directed to the bearings by way of a supply header. A drain header collects the oil leaving the bearings, which flows back into the reservoir. If control oil is required for  any control valve positioning, like the steam turbine governor valve, additional control valves are used to establish the two levels of pressure needed, since the control oil is normally at a significantly higher pressure than that needed by the bearings.

In the older compressors that used oil film or mechanical contact seals, another pressure level is needed for the seals that is sufficiently higher than the process gas pressure  These compressors need to be depressurized at shutdown.

Since the pump is critical to the lubrication system, it must be suitably sized to supply all the consumption points at various pressure levels. The pump driver must be sized to be able to start with cold oil. It must have enough power to operate under all conditions, including the highest seal pressures expected. In some cases ,booster pumps may be needed.

Intercoolers

Intercoolers for Carbon Dioxide compression systems used in CCUS can be air-cooled exchangers or  conventional water-cooled Shell and Tube exchangers. Regardless of the type, considering the large flows and compression requirements, heat duties are typically several million kilojoules per hour. This leads to massive heat exchangers that are difficult to fabricate and transport. From this perspective, some vendors have developed compact heat exchangers specifically for CCUS service. However, the performance, mechanical integrity and maintainability of  these should  be thoroughly evaluated.

From a design perspective, uncertainty in predicting fluid properties at supercritical conditions, especially density and viscosity, makes heat transfer and pressure drop calculations complex. The usual correlations do not give accurate results. Regarding two-phase flow in the intercoolers, while moisture condensation will happen and must be accounted for in the heat duty, liquid Carbon dioxide formation should be avoided.

Scenarios such as  Carbon dioxide hydrate blocking any flow paths must be considered and the design must allow for maintenance intervention, including opening up the equipment. This may be a problem with compact heat exchangers

Scrubbers

Scrubbers, also called knock-out drums, are required at the first stage inlet and after every intercooler. It is not necessary to provide a scrubber after the final supercritical compression  stage, as entrained Water is not likely. It depends on the extent of after-cooling and whether fluid cools below the Water dew point before entering the injection pipeline.

The design of scrubbers is based on the density difference between the liquid and gas. In this case the liquid to be knocked out in the scrubber is Water. When Carbon Dioxide becomes a dense phase fluid, the density difference between Water and gas phases decreases. This increases the size of the scrubber. Further, the density value of the gas is not precisely known, hence a higher factor of safety must be applied. Some vendors are no longer offering conventional scrubbers between stages. Instead, they are offering impingement type entrainment separators which are integrated with the intercooler. This brings down the overall size of the compression skid. Information regarding these integrated cooling and liquid knock-out system is currently not in the public domain. As in the case of compact heat exchangers, a detailed evaluation is recommended before taking a decision.

The inlet scrubber before the first stage can be extremely large in size and may need multiple inlet and outlet nozzles. This is because the arrival pressure of Carbon Dioxide from Amine based Carbon Capture units is only slightly above atmospheric. Hence the allowable pressure drop in the nozzles and through the scrubber is very low. For this reason, the CCUS compressor skid should be placed as close as possible to the Amine unit regenerator, to minimize the piping length.  In a brownfield installation, finding adequate space in the layout becomes problematic. In new plant designs adequate provision can be made in the layout for future retrofit of CCUS.

Another issue that crops up is disposal of condensed Water drained from the interstage scrubbers. It usually necessary to provide a drain vessel and pump for this purpose. This Water is slightly acidic due to dissolved Carbon Dioxide. Many installations pump this back to the Amine unit regenerator to strip out the Carbon Dioxide. As long as the regenerator has the required capacity to handle this additional flow, this is a good strategy. Alternatively, the condensed Water can added to the cooling tower make-up Water

Utility fluids and Related Systems

The compressor system needs to be supplied with adequate utilities. It is advisable to plan for utility systems at the outset, since given the scale of typical CCUS projects, the utility requitements are huge. It is also important not to overlook the utility requirement of various components of the utility systems such as air compressors, boiler systems, cooling towers, Water treatment and others.

The following is a check-list of potential utility requirements for a typical CCUS compression system project :

  • Electric power
  • Cooling water
  • Instrument air
  • Plant air
  • Nitrogen
  • Boiler
  • Boiler feedwater
  • Steam/condensate
  • Fuel gas
  • Chemical dosing systems
  • Process water
  • Fire-Water

Chemicals and Lubricants

  • Water treatment chemicals
  • Biocide (e.g., Glutaraldehyde or Amine)
  • Corrosion inhibitor
  • Methanol
  • TEG (for Carbon Dioxide dehydration unit if provided)
  • Boiler chemicals

Liquid and Gas Effluent Systems

  • Process drains
  • Stormwater drains
  • Sanitary wastewater
  • Vent /Flare system

References

  1. IPCC Special Report on Carbon Dioxide Capture and Storage, 2005. https://www.ipcc.ch/report/carbon-dioxide-capture-and-storage/
  2. Research and Development Needs for Advanced Compression of Large Volumes of Carbon Dioxide, J. Jeffrey Moore et al., Workshop on Future Large CO2 Compression Systems, March 30-31, 2009, Southwest Research Institute, Texas, USA.
  3. Carbon Dioxide AIGA 068/10 Globally Harmonised Document, 7th Edition – 2009 https://www.asiaiga.org/uploaded_docs/AIGA 068_10 Carbon Dioxide_reformated Jan 12.pdf
  1. The Water Content Of Acid Gas And Sour Gas From 100° To 220°F And Pressures To 10,000 Psia, John J Carrol, presented at 81st Annual GPA Convention, March 11-13, 2002,Dallas,Texas,USA; PDF (gasliquids.com)
  2. Key issues related to modelling of internal corrosion of oil and gas pipelines – A review Srdjan Nesic, Corrosion Science 49 (2007) 4308–4338. Key issues related to modelling of internal corrosion of oil and gas pipelines – A review – ScienceDirect.
  3. Prediction of CO2 hydrate formation in supercritical CO2 long-distance pipeline network by simulation, Bing Chen , Qichao Fang, Qiong Zhao , IOP Conf. Series: Earth and Environmental Science 804 (2021) 022001; Prediction of CO2 hydrate formation in supercritical CO2 long-distance pipeline network by simulation – IOPscience
  4. The Past, Present and Future of CO2 Compression; By Mark Kuzdzal, Director, Business Development, Dresser-Rand and Pete Baldwin, President, Ramgen Power Systems LLC; Carbon Capture Journal, Nov.04, 2012. Carbon Capture Journal
  5. CO2 compressor corrosion and scaling problems; Shi Chen ,UreaKnowHow.com, Technical paper, September 2014. 2014 09 Chen Ningxia CO2 compressor corrosion and scaling problems (ureaknowhow.com)
  6. Selecting A Centrifugal Compressor, by James.M.Sorokes, CEP, June 2013, www.aiche.org; Selecting a Centrifugal Compressor | AIChE
  7. Types and classification of centrifugal compressor, online posting by thepipingtalk, 12/2020. Types and classification of centrifugal compressor – The piping talk .
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