ASSESSMENT AND EXPLOITATION

Harsh Gupta , Sukanta Roy , in Geothermal Energy, 2007

Field data on corrosion investigations

Tolivia et al. (1976) report on the corrosion resistance of different turbine materials in geothermal steam environment. These investigations were conducted at Cerro Prieto geothermal field in Mexico. Fig. 6.12 schematically explains the experimental set up. Steam was separated from the hot water by a separator and introduced into steam and aerated steam chambers (Figs. 6.12A,B). The separated steam was led through a cooler to obtain condensate, which was stored in a tank and from there introduced into low and high-velocity test chambers (Fig. 6.12C). The test conditions and chemical compositions are listed in Tables 6.7 and 6.8 respectively.

Fig. 6.12. Schematic representation of the corrosion test equipment. (A) Test chamber for nonaerated steam. (B) Test chamber for aerated steam. Test apparatus for immersion test in condensate.

 (modified from Tolivia et al., 1976).

Table 6.7. Corrosion test conditions in separated steam and condensate (Tolivia et al., 1976)

Velocity, (ms–1) Pressure (psi) Temperature, (°C)
Separated steam
Nonaerated <10 70–194 152–194
Aerated <10 Atmosphere 100
Condensate
High velocity 0.5 – 38–58
Low velocity 0.02

Table 6.8. Average chemical compositions of separated steam and condensate (Tolivia et al., 1976)

Chemical composition (ppm by weight)
Separated steam CO2 19,500.00
H2S 2,580.00
Cl– 13.30
SO4 6.80
Na 1.29
K 0.58
pH 8.35
Condensate pH 7.10
Cl– 42.00
Conductivity 648 µm ho

General corrosion tests were performed on plate pieces measuring 0.03 m × 0.06 m × 0.003 m. At intervals of 30 days exposure, for a total duration of up to 150 days, two test pieces of each material were removed from the test chamber and corrosion rates were measured. Stress corrosion tests were conducted on U-bend test pieces to which yield strength was applied. Visual and microscopic observations were made to check for the presence of cracks. Corrosion-fatigue tests were conducted on shank-type plane-bending specimens. Summary results of these experiments are presented in Tables 6.4–6.6.

It has been concluded from these experiments that the carbon steel used in turbine shells and piping has satisfactory corrosion resistance in non-aerated steam, and its corrosion rate increases in aerated steam and condensate. Hence adequate corrosion allowance should be made in design, and coating with epoxy resin would be required in low-temperature conditions. The deterioration of the fatigue endurance limit is more important than the general corrosion rate for the 12Cr steel used for the bucket. For making the rotor, low-alloy steels are almost as good as carbon steel in corrosion rate. Dioxized copper and aluminum are very poor in corrosion resistance in the condensate and as such cannot be used for constructing thin-walled heat exchanger tubes and the use of highly resistant material like titanium is desirable for their efficient functioning.

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Pollutants and contaminants

Ray Tricker , Samantha Tricker , in Environmental Requirements for Electromechanical and Electronic Equipment, 1999

7.4.2 General corrosion tests (IEC 68.2.42 and IEC 68.2.43 Tests Kc and Kd)

Standard No. IEC 68.2.42
Title Environmental testing procedures – Test Kc: Sulphur dioxide test for electrical contacts and connections
Summary Test Kc provides accelerated means to assess the corrosive effects of atmospheres polluted with sulphur dioxide on contacts and connections.
Equiv. Std Similar to BS 2011:PT2.1Kc(1991)
Identical to DIN IEC 68 PT2-42
Identical to NEN 10068-2-42
Standard No. IEC 68.2.43
Title Environmental testing procedures – Kd: Hydrogen sulphide test for electrical contacts and connections
Summary Test Kd is intended to provide accelerated means to assess the effects of the tarnishing of silver and silver alloys used for contacts and connections. It is particularly suitable for giving information on a comparative basis, but not as a general corrosion test, i.e. it may not predict the behaviour of contacts and connections in industrial atmospheres. The objects of the test are:
(a)

to determine the influence of atmospheres containing hydrogen sulphide on the contact properties of contacts made of silver or silver alloy, silver protected with another layer, other metals covered with silver or silver alloy;
(b)

to check wrapped or crimped connections made of the same materials as mentioned under (a) with regard to their tightness or effectiveness.
Equiv. Std Technically equivalent to AS 1099:PT2Kd
Identical to BS 2011:PT2.1Kd(1977)
Identical to DIN IEC 68 PT2-43
Identical to NEN 10068-2-43

7.4.2.1 Introduction

These general corrosion tests are particularly suitable for providing information on a comparative basis for atmospheres polluted with sulphur dioxide and/or atmospheres containing hydrogen sulphide.

7.4.2.2 Purpose of these tests

7.4.2.2.1 IEC 68.2.42 (Kc)

The purpose of this test is to assess the corrosive effects of atmospheres containing sulphur dioxide on the contact properties of precious metal, or precious metal covered contacts, excluding contacts consisting of silver and some of its alloys.

7.4.2.2.2 IEC 68.2.43 (Kd)

The purpose of this test is to:

•

provide a method for assessing the effects of atmospheres containing hydrogen sulphide on the contact properties of contacts made of silver, silver alloy, silver protected with another layer and other metals covered with silver or silver alloy;

•

check wrapped or crimped connections made of the same materials as mentioned above with particular reference to their tightness or effectiveness.

7.4.2.3 General conditions

These tests are not suitable as general corrosion tests as they may not necessarily predict the behaviour of contacts and connections in industrial atmospheres. They are particularly suitable for providing information on a comparative basis and are intended to provide an accelerated means to assess the effects of tarnishing of silver and silver alloys used for contacts and crimped connections.

7.4.2.4 Test conditions

7.4.2.4.1 IEC 68.2.42 (Kc)

Test Kc (Sulphur dioxide test for contacts and connections) provides an accelerated means to assess the corrosive effects on contacts and connections of atmospheres polluted with combustion products. It is particularly suitable for giving information of a comparative basis but it is not suitable as a general purpose corrosion test. The standard provides the reader with detailed instructions on the composition of the atmosphere within the test chamber, schematic drawings of the apparatus required to generate the test conditioning atmosphere (see Figure 7.2) and a schematic flow diagram.

Fig. 7.2. Schematic drawing of apparatus for the generation of a conditioning atmosphere

 (reproduced from the equivalent standard BS 2011:PT2.1Kc (1991) by kind permission of the BSI)

Temperature does not affect the rate or degree of corrosion occurring in the test to any marked degree. However, as temperature and relative humidity are intimately related and as the latter exerts a marked influence on the degree and nature of corrosion of the test, it is essential that the test temperature is closely controlled to enable the relative humidity to be held within the specified limits and produce the required test severity.

Relative humidity has a greater effect on the test severity than the difference in concentration of sulphur dioxide and temperature. The corrosion rate is relatively low at relative humidities below 70%. Corrosion is markedly accelerated, and the nature and properties of the corrosion products change considerably, at relative humidities above 85% (see Figure 7.2).

7.4.2.4.2 IEC 68.2.43 (Kd)

Test Kd (Hydrogen sulphide test for contacts and connections) provides details of tests aimed at assessing the effects of atmospheres containing hydrogen sulphide on the contact properties of contacts (and wrapped or crimped connections) made of silver, silver alloy, silver protected with another layer and other metals covered with silver or silver alloy. The major criteria of this test is to determine the change in contact resistance caused by exposure to the hydrogen sulphide containing atmosphere. The tests have been devised to assess the consequence of tarnishing silver and some of its alloys.

The tests have been validated by laboratory and field tests on silver, though limited tests have also been carried out on components with contacts made of some silver alloys. Gold contacts are largely unaffected by the test.

The standard provides the reader with detailed instructions on how to construct a test chamber and the composition of the atmosphere within the test chamber.

7.4.2.5 Other standards

IEC 144 Degrees of protection of enclosures for low voltage switchgear and controlgear
IEC 529 Classification of degrees of protection provided by enclosures

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Geothermal Energy

S.N. Karlsdóttir , in Comprehensive Renewable Energy, 2012

7.08.3.11 Erosion Corrosion

Erosion corrosion is an accelerated form of corrosion of a metal caused by relative movement between corrosive media and metal surfaces. The corrosive medium can be one of the following: fluids, for example, water or solutions containing suspension; organics; or gases or steam such as geothermal liquid. The metal surface becomes damaged by mechanical or hydraulic wear or abrasion caused by the flow of the medium. In erosion corrosion, the metal surface is not covered by corrosion products, but characterized in appearance by grooves, waves, gullies, rounded holes, or valleys, and it usually exhibits directional pattern. In many cases, failures due to erosion corrosion occur in a relatively short time and they are sometimes unexpected because previous evaluation corrosion tests were run under static conditions, or because the erosion effects were not considered. Most metals and their alloys are susceptible to erosion corrosion damage. Metals that depend on passivity by forming a protective surface film are also susceptible to erosion corrosion as, if the surface film is damaged, the bulk metal or alloy is attacked at a rapid rate. Increased velocity usually results in increased erosion corrosion [11]. Erosion corrosion can occur in equipment used in a geothermal environment that is exposed to moving fluid including piping systems, particularly elbows and tees, pumps, valves, impellers, blowers, heat exchanger tubing, condensers, nozzles, and turbine blades. Erosion corrosion can also be caused by impingement; this can occur in the steam turbine blades in geothermal turbines particularly in the exhaust or wet-steam ends of the turbine [15]. Moreover, another form of erosion corrosion is cavitation damage; it is caused by the formation and collapse of vapor bubbles in a liquid near a metal surface [11]. It occurs in equipment where high-velocity liquid flow and pressure changes are encountered; these conditions can occur, for example, in geothermal wells and equipment. Cavitation can occur in geothermal wells when the water starts to boil when the pressure decreases because of vapor bubbles that form (containing dissolved gases) and collapse at the metal surface at high speed resulting in cavitation damages, that is, holes. In a high-temperature geothermal well (∼300   °C) in Iceland containing H2S, CO2, and HCl, the steel casing – grade K-55 – underwent extensive cavitation and HE that caused fracture of the steel liner.

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Simultaneous Electrochemical Recovery of Rare Earth Elements and Iron from Magnet Scrap

V. Prakash , ... Yongxiang Yang , in Rare Earths Industry, 2016

2.2 Microstructure of the Magnet and Dissolution Mechanisms

Another crucial aspect of selective dissolution is a proper understanding of the correlation between the microstructure of the alloy and the corresponding dissolution mechanisms. Neodymium iron boron magnets have a matrix ferromagnetic phase (Φ) of Nd2Fe14B tetragonal compound and are surrounded by intergranular regions containing a neodymium-rich phase (n) and a boron-rich phase (η) (Schultz et al., 1999). The complexity of the intergranular region in the microstructure of the neodymium magnets depends on additional elements such as cobalt, aluminum, and gallium. Several authors (Mao et al., 2011a; Szymura et al., 1991) have proposed that neodymium-rich phases (n) corrode preferentially because of the formation of a galvanic couple because of the negative standard reduction potential of rare earths. This is followed by the boron-rich phase dissolution, which renders the matrix loose, finally creating disruption of the matrix phase. Corrosion in the NdFeB alloy is a natural process and can even result in pulverization of the magnet. The scheme of the step-by-step dissolution process presented by Schultz et al. (1999) is given in Figure 3. Mao et al. 2011b observed the dissolution process of individual phases by synthesizing them separately and subjecting them to different corrosion tests. The neodymium-rich phase had the most negative open circuit potential, followed by the matrix phase and the boron-rich phase, indicating that the neodymium-rich phase has the highest electrochemical reactivity. Bala and Szymura (1991) studied acid dissolution of NdFeB magnets under cathodic polarization and found that at a pH near 0, when the magnet is cathodically polarized, individual elements transfer into the solution at a rate corresponding to their composition in the magnet, indicating a lack of selective dissolution at cathodic polarization. At an increased stirring rate and at cathodic potentials (−0.8 to −1.4   V vs saturated calomel electrode), the magnet surface was screened by hydrogen bubbles and iron dissolution at these potentials, in which it is supposed to be immune according to the Pourbaix diagram, was called "abnormal dissolution." Longer exposure of the magnets under cathodic polarization brought about separation of small particles (<0.01   mm) that underwent further chemical dissolution into the solution.

Figure 3. Schematic illustration of dissolution process of NdFeB magnets by corrosion (Schultz et al., 1999).

Similarly, under galvanostatic conditions, El-Moniem et al. (2002) found that the current density calculated from the mass loss was higher than the applied Faradaic current density, which indicated mechanical degradation or pulverization of the magnets. Suepitz et al. (2010) investigated the corrosion and passivity behavior of neodymium and experimentally observed that abnormal hydrogen evolution is observed under anodic polarization that is similar to the negative difference effect phenomenon (Song et al., 1997) observed in magnesium, but the mechanism of hydrogen formation under anodic polarization has not been fully explored.

The composition of different components in the alloy also has a crucial role in its dissolution process. Corrosion studies of magnets with a higher weight percentage of iron in phthalate buffer showed a reduced current density, indicating the formation of a passive layer of iron oxide (Fe2O3) preventing corrosion (Rada et al., 2005). Aluminum, gallium, and copper have reduced corrosion as they reduce the strength of galvanic coupling among magnetic phases (El-Moneim, 2004), and cobalt has been observed to improve corrosion resistance as it prevents magnetic pulverization (Bala et al., 1993). Dysprosium and niobium have been found to form stable intermetallic phases that retard corrosion (Yu et al., 2004), but also a high amount of dysprosium (16%) has been deemed disadvantageous (Bala et al., 1993) because it tends to accelerate atmospheric corrosion. On the whole, it is important to know the composition of the scrap to accelerate the dissolution process by various means and by altering the environment.

Based on this discussion on selective dissolution, it can be observed that co-dissolution of non-REEs is indeed possible because the alloy gets mechanically degraded during active dissolution; hence, the overall process should be composed of removing iron from the leachate so that the leachate is concentrated with REEs. Conducive conditions for such a process are discussed below.

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BATTERIES | Lifetime Prediction

D.U. Sauer , H. Wenzl , in Encyclopedia of Electrochemical Power Sources, 2009

Comparison of the Different Approaches

The information requirement for the three concepts discussed above and the methods to verify them differ greatly. Verification of lifetime prediction models is difficult and time consuming because models can only be verified for a battery or fuel cell that is well characterized when it is new and for which the complete data sets of voltage, current, and temperature are available from installation to decommissioning including a capacity or performance test and possibly other tests at the time of decommissioning. Furthermore, real verification would require nonaccelerated operation of the battery or fuel cell and this takes years. There are hardly any such data sets available. If lifetime prediction models need to be parameterized, then the validity of the model cannot be checked by using the same data set that has been used for the parameterization. Additional data sets are required for verification.

The physicochemical model requires knowledge of the interaction between electrochemical and physical measurements (state variables: resistance and voltages as a function of SoC, temperature, and microstructure of the active material) and aging processes that are usually not accessible to nondestructive measurements. Only the loss of performance as a result of the combination of aging processes that have taken place can be measured when testing the complete cell. But the detailed modeling approach allows separating the aging effects and this is unique within the different approaches presented in this chapter. The calibration of the models for the different aging effects can be done most efficiently if parts of the cell are subjected to aging tests, e.g., grids or bipolar plates only to corrosion tests. Once this has been accomplished for all components and aging processes and the model describes correctly the changes of performance during the lifetime of a battery or fuel cell and thus correctly predicts the lifetime of the battery, the model has achieved a considerable step toward verification. A single lifetime test in the laboratory, which confirms the lifetime prediction model will be sufficient. The model can then be considered to predict lifetime sufficiently well even if changes of operating strategies and materials lead to a different combination of aging effects. When analyzing measured data, the current, voltage, and temperature values have to be created by the model first. Good agreement between measurements and model will immediately qualify the model and provide credibility to the lifetime prediction.

The transfer to other types of batteries or fuel cells of similar technology is quite easy and requires mainly adequate knowledge of design parameters and results from specific aging tests of cell components. The mathematical algorithms remain the same, but the description of the specific electrochemical reactions and knowledge concerning the dependence of aging effects on the state variables must be obtained newly.

The situation is different for the weighted Ah model: the weighting factors cannot be derived from first principles and need to be obtained differently. Expert expertise or parameters fitting are two options to predict the lifetime correctly. Support from physicochemical models or a first principle approach is possible and helpful. When analyzing measured data, the current, voltage, and temperature values have to be created by the model first. Good agreement between measurement and model will not in itself qualify the model and provide credibility to the lifetime prediction because the electrical performance model is typically a black box model. High credibility of the model is achieved only if good agreement of the electrical performance between reality and model is achieved throughout the whole lifetime.

The use of this approach requires the availability of measurements to fit the parameters or to verify that the combination of expert estimates does in fact lead to the lifetime, which has been measured. Subsequently, another set of measurements is required, sufficiently different not to be a repeat of the parameterization process but sufficiently close to remain within the model constraints. An extension beyond 'similar' data sets offers increasingly less credibility, as does the transfer of the model to other battery types.

The event-oriented concept is the approach used today for lifetime prediction but is extended to variations in the operating conditions that are at present not accounted for properly. It requires an application-oriented definition and classification of events and information concerning the number of these events until the end of lifetime is reached. For some events, measurements are available, e.g., number of cycles at a certain temperature and DoD or days at float charging. In principle, of course, it is possible to determine all the required data in the laboratory correctly without any doubts concerning their validity, but this process takes very long and is exceedingly expensive. However, interpolation by expert opinion can be used as long as measurements for a few types of events exist. This approach therefore is simple and depends on the assumption that the loss of lifetime caused by an event does not depend on the previous event or on the age of the battery. Verification of the model is therefore simply a question of analyzing one single set of measurements, which extends over the lifetime of the battery. A detailed characterization of the battery at the beginning is not necessary but the end of lifetime criteria need to be chosen suitably.

In contrast to the other models, measured data can be taken as they are and need not be recalculated before applying the lifetime prediction models.

A transfer of results to other batteries or fuel cells is straightforward as the model is independent of technology or design but requires the adjustment of the input matrices accordingly.

Table 2 sums up advantages and disadvantages of the different models.

Table 2. Comparison of the different model approaches with regard to parameter identification, model complexity, and transfer to other applications, designs, and technologies (electrochemical systems)

Parameter identification Preciseness and quality of information Model complexity and calculation speed Transfer of model to other applications and battery designs Transfer of model to other electrochemical systems
Physicochemical aging model Through laboratory experiments and literature study High, can give very detailed information High/slow Only battery design parameters needed Same structure, but new models required
Weighted Ah aging model Expert expertise and data from lifetime tests (field or laboratory) Medium, allows optimization of operating conditions Medium/medium Deviating aging effects must be identified and included Same structure, but new weighting factors needed
Event-oriented aging model Expert expertise Low, does not allow extrapolations to applications with other types of events Low/high New expert expertise needed if other stress events occur Same structure, new expert expertise needed

All approaches allow an optimization of the operating strategy of an application. However, only the weighted Ah throughput model and the event-oriented model are applicable for an online optimization of the operating strategy. The physicoelectrochemical model typically is too complex for online applications. However, if sufficient computing power and data storage is available it could become an online tool as well.

If the online models show an increase of the various weighting factors or the battery is classified to be in an event, which uses up a significant portion of the lifetime, then a cost–benefit analysis can be made concerning changes in the operating strategy. In renewable energy systems, for instance, the cost of providing a full charge can be easily compared to the cost of operating the battery in a mode that reduces lifetime significantly. For fuel cells, e.g., the flow rates of gases or the moisture inside the cell and therefore the water content of the membrane could be adjusted to avoid critical situations.

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Phase-change absorption for CO2 capture: Chemical solvents and processes

Elahe Olyaei , Ali Hafizi , in Advances in Carbon Capture, 2020

12.3.1 Liquid-liquid systems

The absorption of carbon dioxide with two immiscible liquid phases is one of most investigated biphasic absorption [32]. One CO2-rich phase and another CO2-lean phase, which can significantly reduce the regeneration energy in comparison with conventional processes [33]. The DMX process, self-concentration process, iCap, amine blends, and thermomorphic biphasic solvent (TBS) systems are the most important commercial biphasic processes.

12.3.1.1 DMX process

The DMX process, the most popular phase-change absorption process, was developed by French Institute of Petroleum (IFP Energies nouvelles). This process uses aqueous demixing solvents selected through the investigation of 300 different amines at various ranges of temperature [34]. These solvents are miscible with water in fresh state and form two phases after CO2 absorption. Using the DMX solvents, phase transition occurs at high temperatures, so the CO2 absorption is performed at 40°C. In addition, the composition of DMX solvents is proprietary and depends on the mixture components. DMX-1 is one of the most important DMX solvents that is the blend of a tertiary and a primary or secondary amine, which seems to have lots of benefit compared to common amine such as MEA and MDEA [35]. The results obtained from laboratory and pilot plant tests indicate that the degradation rate of DMX-1 is seven times lower than that of MDEA and three times lower than that of MEA [36, 37] . The cyclic capacity of DMX-1 was twice that of MEA but with an absorption capacity similar to MEA. Corrosion tests revealed that carbon steel and stainless steel corrosion rates are limited in DMX process. Therefore, carbon steel columns instead of expensive materials such as stainless steel can reduce the capital cost or CAPEX [37].

Fig. 12.2 represents the process flow diagram of DMX process. In this process, the solvent absorbs CO2 at high temperature near 40°C, while phase transition occurs at high loadings and two immiscible liquids are formed [38]. Similar to the other phase-change processes, two phases are separated in the decanter and only CO2-rich phase is sent to regenerator, while CO2-lean phase can be directly recycled to the absorption column. DMX-1 has been investigated as the solvent for this process and the results of simulation showed that heat duty of reboiler can be reduced to 2.1   GJ/t CO2, which is less than that of the MEA process (3.7   GJ/t CO2). Hence, this process was tested in a mini pilot plant and the results were comparable with the process simulation results [36, 37]. The economic analysis shows that the operational cost (OPEX) of DMX process was 35% lower than MEA process but the capital cost was comparable with that of MEA CO2 absorption process [36, 39]. As mentioned earlier, due to high cyclic capacity, less regeneration energy, better thermal stability of DMX-1, and lower operational cost of process, DMX process seems to be a good choice for CO2 absorption, but it still needs further investigations.

Fig. 12.2

Fig. 12.2. The PFD of DMX process [35].

12.3.1.2 TBS process

Thermomorphic biphasic solvent systems were studied by various groups to reduce the desorption temperature to less than 80°C. A series of screening experiments have been performed to choose the appropriate solvent for CO2 absorption. An aqueous blended absorbent comprising DMCA   +   MCA   +   AMP was selected as the best solvent [40]. The tertiary amine N,N-dimethylcyclohexylamine (DMCA) is the basic absorbent, due to the good loading capacity toward carbon dioxide in the absorption step and excellent regenerability. The dipropylamine (DPA) is added as an activator, because of the high CO2 absorption rate. The presence of a small amount of 2-amino-2-methyl-1-propanol (AMP) increases the temperature of the phase change absorbent [31].

In thermomorphic biphasic solvent systems, the absorption is performed normally at about 40°C, and the CO2 desorption process is performed at about 80°C, which is lower than the traditional amines such as MEA (~   120°C) [41]. Due to high phase-change temperature in these systems, the solvent is homogeneous after absorption and forms two phases during the desorption process as the temperature increases (Fig. 12.3) [40].

Fig. 12.3

Fig. 12.3. Principle concept of CO2 absorption in TBS process [40].

The organic solvents such as fresh amines extract the regenerated amines on the CO2-lean side to facilitate the regeneration of other phase [35]. In TBS process, advanced desorption procedures like nucleation, agitation, extraction, and sonication have been performed. The nucleation mechanism tends to speed up the desorption process but it is hard to achieve regeneration at 80–90°C completely, whereas the agitation and sonication-based desorption mutually have low mechanical or electrical energy consumption. The extractive regeneration have been suggested because it reduces desorption temperature to 60–70°C and recovers the lost heat in the regeneration step in order to reduce the operating costs [40]. As indicated in Fig. 12.4, extractive regeneration process includes an absorption column followed by a four-stage extraction unit for phase separation, a distillation column, and a vapor recovery unit. In extraction unit, an inert agent such as pentane could be applied [42].

Fig. 12.4

Fig. 12.4. Flow sheet of an extractive regeneration process [42].

As mentioned earlier, although TBS process have more advantages such as high loading capacity, fast absorption kinetics, and low desorption temperature (so have high stability), but this system has some drawbacks such as high volatility, high viscosity of CO2-rich phase, and sometimes foaming. These drawbacks represent the need for further investigation of TBS process.

12.3.1.3 iCap process

The innovative CO2 capture (iCap) project was developed by the Norwegian University of Science and Technology. In this process, the aqueous mixture of 5   M 2-(diethylamino) ethanol (DEEA) and 2   M 3-(methylamino) propylamine (MAPA) are used as phase-change solvent for CO2 absorption and phase transition (two liquid phases) occur with CO2 loading. Blending of these two amines in aqueous solution combines the advantages of both amines. The DEEA is a tertiary amine with high CO2 loading capacity in absorption with lower heat of absorption, while the MAPA has two amine functional groups (primary and secondary) that can enhance the capture rate [43].

The iCap process with 5   M DEEA/2   M MAPA mixture has been tested in the Gløshaugen (NTNU/SINTEF) pilot plant (Fig. 12.5) followed by the simulation of this process [44]. The difference between this process and the DMX process is that the liquid-liquid phase separation (LLPS) occurs at a very low temperature ≈   20°C.

Fig. 12.5

Fig. 12.5. The Gløshaugen (NTNU/SINTEF) pilot plant [44].

In this pilot plant, issues related to viscosity and foaming have not been reported. Absorption proceeds with a good rate and the CO2 desorption in iCap system seems to be easy due to the presence of the tertiary amines. Specific reboiler duty and reboiler temperatures were considerably lower than that of conventional 30   wt% MEA. Furthermore, it is possible to operate the system without phase separation and could be operated in lower reboiler duties.

It should be noted that this system produces higher heat of absorption on reacting with CO2. Therefore, it requires a higher cooling capacity prior to absorber column. However, the solvent was more volatile than MEA and better control system is needed to avoid solvent loss. The most important advantages of this process include high desorption pressure, high cyclic capacity, and low liquid flow in desorber with good liquid loading in the absorber column. On the other hand, the disadvantages include complexity of system, probably higher heat of reaction, and heat of dissolution.

12.3.1.4 Self-concentration process

The self-concentration process developed by 3H Company is the other liquid-liquid phase-change absorption process. In this process, the nonaqueous solvent contains an amine dissolved in alcohol that absorbs carbon dioxide at mild conditions. The absorption of CO2 results in the formation of two liquid phases: one is CO2-rich phase (lower phase) and the other CO2-lean phase (upper phase). The regeneration of CO2-rich phase separated in a decanter proceeds at 115–125°C. The regenerated phase is then mixed with CO2-lean phase and is returned to the absorber. The developer claimed that this process can reduce the energy of regeneration by about 70% in comparison to conventional MEA absorption plant [45]. In addition, it exhibits higher working capacity, lower pumping energy, and auxiliary power demands along with reduction in the size of proposed equipments. The reduction in corrosion rate due to the nonaqueous nature of proposed process is one of the most important advantages of this process [32].

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Corrosion resistance of candidate cladding materials for supercritical water reactor

Xianglong Guo , ... Lefu Zhang , in Annals of Nuclear Energy, 2019

3 Test specimen and setup

The specimens for corrosion tests had a dimension of 15 × 10 × 2 mm or 30 × 20 × 2 mm and were abraded with emery paper to grit 200#, 400#, 800#, 1200#, and 2000# in order. Finally, they were polished to a 1.0 μm diamond finish and cleaned with ethyl alcohol in an ultrasonic cleaner. Exact dimension and weight of the specimens were measured before corrosion test. The schematic diagram of the general corrosion test setup is shown in Fig. 2. The dissolved oxygen (DO) in SCW was controlled by bubbling mixed gas (5% O2 and 95% Ar) and pure Ar through under a certain proportion. Ultrapure water and mixed bed ion exchanger were used to keep the conductivities of inlet below 0.1 μS/cm. The autoclave is made of nickel based alloy 625 and heated by three-phase electric heater. Two heat exchanger are used. One heat exchanger is used to heat water before entering the autoclave and cool water circulated from the autoclave. Thus, the temperature difference of testing environment and water before entering the autoclave is reduced. The other heat exchanger is used to cool outlet water before entering the water chemistry loop.

Fig. 2. Schematic diagram of the SCW corrosion testing setup.

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Durability of concrete structures in tropical atoll environment

Hongfa Yu , ... Xianshuang Jing , in Ocean Engineering, 2017

2.2.1 Rate of reinforcement corrosion

The rate of reinforcement corrosion was calculated according to the ASTM G1-1990 Standard practice for preparing, cleaning, and evaluating corrosion test specimens. De-rusting steps were as follows: pickling in 12% (mass percent) HCl solution, rinsing with water, neutralizing with saturated Ca(OH)2, and rinsing thoroughly with water. After wiping, drying, and storing for at least 4   h, the concrete was weighed by an analytical balance.

(1) L w = d ⋅ l − m d ⋅ l × 100 %

where L w is the rate of the reinforcement corrosion (%),d is the nominal diameter of the reinforcement (mm), l is the linear density of the reinforcement (g/mm), m is the quality of the reinforcement after pickling (g).

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A Safety Assessment of Saturated Branched Chain Alcohols when used as Fragrance Ingredients

D. McGinty , ... A.M. Api , in Food and Chemical Toxicology, 2010

In order to assess the acute skin irritation potential of isotridecanol-1-ol in White New Zealand rabbits a dermal irritation/corrosion test was performed according to the method described in OECD guideline 404. A 0.5  ml sample of the isotridecanol-1-ol was applied for 4   h to the intact skin of three rabbits, using a patch of 2.5   cm   ×   2.5   cm, covered with semi-occlusive dressing. After removal of the patch the application area was washed off. The skin reactions were assessed immediately after removal of the patch, approximately 1, 24, 48 and 72   h after removal and then win weekly intervals until day 14. Slight to marked erythema, slight or moderate edema and scaling were observed in almost all animals during the course of the study. Additionally the described findings above were partly extended beyond the area of exposure. Moreover severe scaling and petechiae, both extending beyond the area of exposure and thickening of the skin in the regions of the application area were noted in a single animal. The cutaneous reactions (such as slight erythema) were not reversible in all animals within study termination of day 14. The average score (24 to 72   h) for irritation was calculated to be 3.0 for erythema and 0.3 for edema (RIFM, 2003b).

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https://www.sciencedirect.com/science/article/pii/S0278691510003091

Non-animal testing strategies for assessment of the skin corrosion and skin irritation potential of ingredients and finished products

M.K. Robinson , ... J.H. Fentem , in Food and Chemical Toxicology, 2002

The second element is comprised of in vitro testing using methods that can screen for everything from corrosivity to acute and cumulative irritation potential. Some in vitro skin corrosion test methods have already met validation standards for replacement of animal (Draize) test methods ( Fentem et al., 1998; Scala et al., 1999; ECVAM, 1999, 2000). In vitro tests for acute skin irritation are in development and some have entered into inter-laboratory prevalidation trials (Botham et al., 1998; ECVAM, 1999; Fentem et al., 1999). In vitro tests for cumulative or chronic skin irritation are in an earlier method development phase, although several methods have been shown, via publication, to correlate well with clinical endpoints (see below). All of these can be considered within the in vitro testing (screening) framework of the process. These tests can also be of value in formulation testing to ensure that unanticipated chemical interactions do not occur within the final product formula.

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https://www.sciencedirect.com/science/article/pii/S0278691502000054