УГЛЕКИСЛОТНАЯ КОРРОЗИЯ НЕФТЕПРОМЫСЛОВЫХ ТРУБ В СРЕДАХ, НАСЫЩЕННЫХ H2S И Cl

Corrosion behaviour of high-chromium ferritic steels in molten carbonate in cathode environment

The effect of oxygen (O2) contamination on the inhibition of carbon dioxide (CO2) corrosion was studied using carbon steel rotating cylinder electrodes (RCE). The test conditions were 40°C, 1 bar CO2, pH 5.5, and 1 wt% sodium chloride (NaCl) solution. The uninhibited CO2 corrosion rate was 1.5 mm/y to 2 mm/y under these conditions. Three organic, film-forming corrosion inhibitor formulations were tested in the concentration range from 20 ppm to 50 ppm. With less than 1 ppb of dissolved O2 in the test brine, the inhibitors reduced the corrosion rate by two orders of magnitude, and the inhibited corrosion rates were insensitive to the RCE rotation rate (100 rpm to 5,000 rpm). In the presence of 100 ppb O2 with 20 ppm to 30 ppm inhibitor, the corrosion rates depended on the RCE rotation rate, the corrosion rate being under partial or full O2 diffusion control with some contribution of CO2 corrosion. The O2 corrosion rate was reduced by increasing the inhibitor concentration. The consequences of the reported findings with respect to O2 concentration limits in CO2 corrosion inhibitor tests are discussed.

Carbon assimilation at low carbon dioxide levels was measured on three Oryza specics (O. sativa L. cv. Toyonishiki, O. officinalis Wall, and O. meyriana Baill.), Brassica napus L. cv. Michinokunatane and Triticum aestivum L. cv. Konosu No.25. Measurements were made at two different oxygen concentrations; 140% and 21% (atmospheric pressure). An improvement in measurement device was made for ensuring an accuracy of the meter readings. That is, a recorder with a modulator was used to enlarge the differences in the carbon dioxide concentration; two- and five-fold for carbon dioxide levels above and below carbon dioxidc compensation point (gamma), respectively. It seems that HEATH and ORCHARD (1968) and HOLMGREN and JARVIS (1967) Changed the carbon dioxide concentration at large intervals, resulting in 3 to 5 measurements below gamma. Such a few measurements would obscure the statistics of the carbon dioxide exchangc rate at low carbon dioxide levels. The changes of carbon dioxide concentration in this experiment, however, were made at intervals of about 2 or 4 ppm from 0 ppm to gamma, resulting in 7 to 14 mean values below it. As the characteristics of carbon dioxide absorption at low carbon dioxide levels, GABRIELSEN (1948) proposed the 'threshold hyPothesis' in which gamma was regarded as a threshold value below which no assimilaton occurred, while HEATH and 0RCHARD (1968) postulated the existence of a 'third process', in addition to ordinary (dark) respiration and assimilation, which could be expected to have a different balance between respiration and assimilation. They denied the adoptation of the threshold hypothesis. From the prescnt experiment in which the carbon dioxide exchange rates were traced by Changing the Carbon dioxide concentrations at very small intervals, hwever, it appeared that the rate of carbon dioxide uptake at low carbon dioxide levels and atmospheric oxygen pressure tended to decrease toward 1/2 gamma carbon dioxide level, and the carbon dioxide uptake seems to cease and only the carbon dioxide release secms to occur below it. In case of measurements at 14% oxygen concentration the situation was similar to those at 2l% oxygen concentration, but a considerable decrease of the value of gamma. Thus, the process of carbon dioxide uptake at low carbon dioxide levels seems to imply the threshold hypothesis and 1/2 gamma seems to be an approximation of the threshold value. The assimilation rate is estimated as the ratio of carbon dioxide concentration differences between ambient air and assimilation center to the sum of diffusion resistances.As an estimate of carbon dioxide levels in the assimilation center in this formula, GAASTRA (1959) proposed zero, while BIERHUIZEN and SLAYTER (1964) adopted the Practise of using gamma to estimate it. From the results mentioned above, we could propose to use 1/2 gamma as its primary approximation because the photosynthetic center would be exposed to this carbon dioxide level but not absorb it.

Distribution of methane and carbon dioxide concentrations in the near-surface zone and their genetic characterization at the abandoned “Nowa Ruda” coal mine (Lower Silesian Coal Basin, SW Poland)

With the depletion of low carbon dioxide (CO2) content natural gas reserves, there is a pressing need to explore the vastly undeveloped high CO2 content natural gas reserves and reduce the release of greenhouse gas CO2 into environment. Our previous investigation on the absorption performance of CO2 at high concentration level of 50% from mixture of CO2-natural gas stream for 20wt% monoethanolamine (MEA) solution in countercurrent packed column indicated efficient removal at high pressure condition. In this present work, a combination mass transfer, chemical reaction of MEA as well as mass conservation equation was developed to model the removal behavior of the high pressure, high concentration CO2 capture along the absorption column. The model developed in this study had satisfactorily represented the mass transfer behavior for high pressure and high CO2 concentration gas removal along the absorption column.

Evidence of methane and carbon dioxide migration to the near surface zone in the area of the abandoned coal mines in Wałbrzych District (Lower Silesian Coal Basin, SW Poland) based on periodical changes of molecular and isotopic compositions

Editor, Anaesthesiologists interpret the patient state by obtaining useful information from a monitor screen. In particular, measurements of carbon dioxide levels related to artificial respiration greatly contribute to the safety of the anaesthetized patient.1,2 We present this report because special attention should be given to the interpretation of carbon dioxide waveforms on the monitor. Carbon dioxide curves provide much information on the patient state. On the basis of this information, anaesthesiologists can identify the presence of both artificial and spontaneous respiration. However, when an irregular carbon dioxide curve at the early recovery stage of anaesthesia changes into a regular one as anaesthesia recovery progresses as in Fig. 1, care must be taken to accurately assess the patient state. When carbon dioxide concentration is low at the initial anaesthesia recovery, it is estimated that ventilation is minimal. However, while spontaneous respiration resumes after slight anaesthesia recovery, the carbon dioxide curves sometimes appear in regular patterns and the value is high as in Fig. 1. At that time, tidal volume, that is, the flow rate, is not related to carbon dioxide value. For this reason, tidal volume is either extremely low as in Fig. 1(a) or rather high as in Fig. 1(b). The discrepancy between the carbon dioxide curve and the flow rate may be explained by the fact that the carbon dioxide curve does not represent the absolute value, but the ratio of carbon dioxide to the total expiratory gas. The irregular carbon dioxide basically originates from abrupt initiation of inspiration and expiration during early recovery, which also cause abrupt change of the ratio of carbon dioxide to the total expiration gas. Although tidal volume is relatively small as in Fig. 1(a), it can be presented as such regular patterns and high value if the patient breathes regularly and the ratio of carbon dioxide to the total expiratory gas is periodically changed. Likewise, if carbon dioxide concentration does not increase despite the fact that tidal volume increases from the value in Fig. 1(a) to that in Fig. 1(b), the carbon dioxide curve will be unchanged. In Fig. 1, the carbon dioxide curve indicates that expiratory gas contains approximately 4% (=35/760) carbon dioxide, but it gives little information on tidal volume. Therefore, after anaesthesia recovery progresses to some extent, we should evaluate tidal volume by the movement of the bellows or the patient chest as well as the flow-time curve displayed on a spirometre in an anaesthesia machine instead of the carbon dioxide curve.Fig. 1

The oxygen production of a photosynthetic gas exchanger containing Chlorella pyrenoidosa (1% packed cell volume) was measured when various concentrations of carbon dioxide were present within the culture unit. The internal carbon dioxide concentrations were obtained by manipulating the entrance gas concentration and the flow rate. Carbon dioxide percentages were monitored by means of electrodes placed directly in the nutrient medium. The concentration of carbon dioxide in the nutrient medium which produced maximal photosynthesis was in the range of 1.5 to 2.5% by volume. Results were unaffected by either the level of carbon dioxide in the entrance gas or the rate of gas flow. Entrance gases containing 2% carbon dioxide flowing at 320 ml/min, 3% carbon dioxide at 135 ml/min, and 4% carbon dioxide at 55 ml/min yielded optimal carbon dioxide concentrations in the particular unit studied. By using carbon dioxide electrodes implanted directly in the gas exchanger to optimize the carbon dioxide concentration throughout the culture medium, it should be possible to design more efficient large-scale units.

Dwarf french beans (Phaseolus vulgaris var. Canadian Wonder) were grown in chambers at 25°C with the roots aerated at 20 per cent oxygen and tops variously maintained at: T1 O2 0.21; CO2 270×10−6: T2; O2 0.05, CO2, CO2 270×10−6: T3; O2 0.21; CO2 550×10−6. Experiment 1 (T1 and T2) lasted 2 weeks: Experiment 2 (T1T2 and T3) only one week. Hourly estimates of CO2 uptake were made by gas analysis and weekly estimates of fresh weight, dry matter in tops and roots, and leaf area, by sampling. Light intensity was 80 W m−2 of photosynthetically active radiation. An attempt was made to explain the results in terms of a simple light absorption model such that where dV/dt is the rate of CO2 uptake per plant, β is the photosynthetic efficiency, I0 is the incident light intensity, f is the fraction of incident light absorbed by unit leaf layer and L is the leaf area index. The analysis showed that β(T2) was at least double β(T1), whilst f(T2) was smaller than f(T1) at a given leaf area. The results also required that throughout the period of the experiment, fL(T1)=fL(T2) at any given time, i.e. the treatment with the larger leaf area (T2) has the smaller value of f, and therefore intercepts less light per unit leaf area. This could be advantageous for plant growth, but requires further experiments. The photosynthetic rates per unit leaf are about 40 per cent greater in T2 than T1. Over the relatively short period of the experiment the results are adequately described by U=btn, where U is the accumulated carbon dioxide uptake, b is related to the photosynthetic efficiency (different for the differing treatments), and n is a constant (similar for all treatments). This relationship with time is believed to be a relationship with accumulated radiation, for the light was constant throughout the experiments. Comparisons of carbon fixed (measured gas uptake) and dry matter accumulation (sampling) show great scatter with an average value of 0.43. The first week's results were generally smaller than this value and the second week's greater. Energy fixation as a fraction of photosynthetically active radiation on the ground area covered by the plants ranged from 3.5 to 10 per cent. The results from treatment T3 were similar to T2 suggesting that increasing CO2 concentration decreases the growth inhibition at 21 per cent O2.

Field experiments were conducted in storage silos to evaluate carbon dioxide sensors to monitor spoilage in grain prior to spoilage detection by traditional methods such as visual inspections and temperature cables. Carbon dioxide concentrations in the storage silo were monitored up to eight months and correlated to the presence of stored-product insects, molds and mycotoxin levels in the stored grain. The data showed that safe grain storage was observed at CO 2 concentrations of 400 to 500 ppm. Higher concentrations of CO 2 clearly showed mold spoilage or insect activity inside the grain storage silo. Carbon dioxide concentrations of 500 to 1200 ppm indicated onset of mold infection where as CO 2 concentrations of 1500 to 4000 ppm and beyond clearly indicated severe mold infection or stored-product insects infestation. The percent kernel infection was in the range of 30% for CO 2 concentrations of 500 to 1000 ppm to 90% for CO 2 concentrations of 9000 ppm. Fungal concentrations were in the range of 2.0 ×102 colony forming units per gram (cfu/g) at 500 ppm CO 2 concentration to 6.5 ×107 cfu/g at 9000 ppm CO 2 concentration. Fungi of genera Aspergillus spp., Penicillium spp., and Fusarium spp. were isolated from spoiled grain. High concentration of fungi and presence of mycotoxins (aflatoxin: 2 ppb and Deoxynivalenol (DON): 1 ppm) were correlated with high CO 2 concentration in the silos. The findings from this research will be helpful in providing more timely information regarding safe storage limits, aeration requirements and costs of spoilage mitigation measures such as turning, aerating and fumigating grain. Additionally, it will provide information on preventive stored grain quality management practices that should reduce residue levels of mycotoxins, pesticides and other foreign material in our food supply. The CO 2 monitoring technology will increase the quality and quantity of stored grain, while saving the U.S. and global grain production, handling and processing industry millions of dollars annually. Keywords : Carbon dioxide, Grain storage, Stored-product insects, Mold and mycotoxin

Corrosion destruction of the metal of the field equipment and gas pipelines of the oil and gas condensate field (OGCF) was revealed, the cause of which is carbon dioxide corrosion. In order to determine the corrosiveness of the OGCF equipment media, laboratory tests were carried out with periodic moisture condensation in an atmosphere of carbon dioxide, autoclave tests in the liquid phase at elevated temperatures and partial pressure of CO2, and laboratory tests in the gas-vapor phase in the presence of CO2. Tests were carried out on steel 20, the selected solutions were tested on pipe segments of 09G2S steels (well connections and loops) and J55LT (tubing) of 2 types (old, after operation in a well, and new, not operated). Studies have shown that steels used at OGCF (steel 20, J55LT and 09G2S) are not resistant to carbon dioxide corrosion. All items of equipment made of these steels will be potentially weakly resistant to corrosion in the oil and gas condensate field. It is proposed to conduct tests of corrosion inhibitors from various manufacturers in laboratory and field conditions. Recommendations are given for the corrosion inhibitor selected according to the test results. Keywords: local corrosion; aggressiveness of the environment; metal resistance; well piping; plume; tubing; laboratory tests; autoclave tests.

Main ways to control the carbon dioxide corrosion, type of inhibitors employed, reasons for choice of the inhibitors, and various factors determining the efficiency of inhibitors of different types in carbon dioxide oil-and-gas production media are considered.

Chapter 13 - Piping and valve corrosion study

It is our hypothesis that fermentative, acetogenic, and sulfate-reducing bacteria residing in pipeline facilities can influence corrosion through the production of carbon dioxide and acetate under the prevailing anaerobic conditions. The exacerbation of carbon dioxide corrosion of carbon steel in the presence of acetic acid is a well-known phenomenon in the oil industry. Both chemical compounds can be produced and consumed by microorganisms during the anaerobic biodegradation of organic matter—including hydrocarbons. We contend that the principles governing anaerobic biodegradation activity can be extrapolated to aboveground oil production facilities and that the microbial diversity inherent in petroleum reservoirs largely reflects that in pipelines.

A mechanistic model of uniform carbon dioxide (CO2) corrosion is presented that covers the following: electrochemical reactions at the steel surface, diffusion of species between the metal surface and the bulk including diffusion through porous surface films, migration due to establishment of potential gradients, and homogenous chemical reactions including precipitation of surface films. The model can predict the corrosion rate as well as the concentration and flux profiles for all species involved. Comparisons with laboratory experiments have revealed the strengths of the model such as its ability to assist in understanding complex processes taking place during corrosion in the presence of surface films.