Corrosion Mitigation Using Nonmetallic Piping for In-Plant Hydrocarbon Service

The underground hydrocarbon metallic lines are usually subjected to severe corrosion due to several reasons such as high water table in the area and due to intermittent bi-directional crude service or similar environmental factors. To meet the challenge, non-metallic underground crude transfer lines may be considered to carry oil from/to the bulk storage sites. Since there are not many non-metallic applications in HC services, it may become a challenge to get the necessary approvals from the various stake holders in terms of concerns for asset integrity and the costs. This report details the conversion of metallic crude pipeline application to a non-metallic one. Normally, the in-kind replacement will involve an internally coated CS line to reduce corrosion rate. However, engineering studies and assessments reveal that there are greater economic benefits when adapting to a non-metallic counterpart. For a generic case, hydraulics on a 1.7km crude transfer line with 48" diameter and the intermittent crude service revealed that 36" non-metallic version could do the job with less installation costs as minimal site activities will be required and there will be no requirements of non-destructive tests (NDT). Only a service test following the installation may be necessary to prove the operational integrity. Cost comparisons showed a 28% less project cost in using the non-metallic pipeline while meeting all other application requirements. The introduction of non-metallic line would take away the problem of the external and internal corrosion from the equation. Especially in the aging facilities where fatigue becomes an issue, the carbon steel line always requires additional maintenance activities and there was always a chance to develop an underground pin hole. Therefore, an extensive inspection program had its own costs to maintain the line. With the non-metallic pipe usage, not only the construction costs can be lowered but it could avoid major inspection and maintenance program costs. The Nonmetallic line is considered low to maintenance free, and additional long-term savings are expected. This application opens the door for the utilization of nonmetallic material in plant hydrocarbon processes. And given the size considered of this line (36 inches), this allows for further consideration to install nonmetallic piping on a wide range of applications. Also, non-metallics are especially effective for sluggish or intermittent flows and areas with high water table to avoid all sorts of erosion and corrosion issues internally due to process conditions or externally due to environmental conditions.

Origin of the Coloured Karst Fills in the Neogene Extensional System of NE Iberia (Spain)

Karst fills from the onshore Penedès Basin and offshore València Trough display red, pink, orange and ochre colours. Their Mössbauer spectra indicate that Fe3+ contained in goethite is the dominant species in reddish-pink fills, whereas Fe2+ contained in dolomite and clays is more dominant in the orange and ochre ones. The lower δ13C values and higher 87Sr/86Sr ratios of the karst fills with respect to their host carbonates can reflect the input of soil-derived CO2 and an external radiogenic source into the karst system. This geochemical composition, together with the non-carbonate fraction of the fills, consists of authigenic and transported illite, illite-smectite interlayers, as well as kaolinite, chlorite, pyrite, quartz, ilmenite, magnetite, apatite and feldspar, account for a mixed residual-detrital origin of fills. This polygenic origin agrees with that of the terra rossa sediments described worldwide. The different colours of karst fills are attributed to fluctuations in the water table, which control the Eh/pH conditions in the karst system. Thus, reddish colours reflect low water table levels and oxidising episodes, and orange and ochre ones reflect high water table levels and more reducing episodes. The greenish colours of fills could be related to fluctuations in the Fe3+/Fe2+ ratio.

Hydrological and ecological controls on dissolved carbon concentrations in groundwater and carbon export to surface waters in a temperate pine forest watershed

Export of soil carbon to superficial water through the drainage of groundwater is a significant but poorly documented component of the continental carbon budget. We monitored the concentrations of dissolved organic and inorganic carbon (DOC and DIC) in groundwaters and first order streams of a small temperate, forested and sandy watershed where hydrology occurs exclusively through drainage (no surface runoff). The studied watershed was also implemented for continuous measurements of groundwater table, precipitation, evapotranspiration, river discharge, and net ecosystem exchanges of sensible and latent heat fluxes as well as CO2. On a monthly basis, we found a good consistency between precipitation and the sum of evapotranspiration, drainage and groundwater storage. DOC and DIC temporary storage in groundwater and export to streams varied drastically during the hydrological cycle, the residence times of these two carbon forms varying from one month to several years. DOC concentrations in groundwater and streams were maximal at high water table and high stream discharge, when the water table reached the superficial organic rich layer of the soil. A large fraction of this winter DOC maximum was temporarily stored and further mineralized to DIC in the groundwater and only about 15 % was exported to streams during winter periods. In contrast, DIC, which was present in majority in the form of dissolved CO2 in groundwater and streams, was apparently diluted at high water table: DIC concentrations were maximum at low water table and low discharge in late summer and maximum pCO2 in groundwater corresponded to the late summer period of heterotrophic conditions (i.e., Reco > GPP). Groundwater DIC peaked in late summer and was followed by a rapid loss of excess CO2 from stream surface to the atmosphere. Overall, mean carbon export was 7.5 g C m−2 yr−1 (50 % as DOC and 50 % as DIC) and represented only 1.5 % of the NEE. About 65 % of the DIC exported from groundwaters returned to the atmosphere in the form of CO2 in first order streams.

Evaluating the influence of water table depth on transpiration of two vegetation communities in a lake floodplain wetland

Groundwater plays an important role in supplying water to vegetation in floodplain wetlands. Exploring the effect of water table depth (WTD) on vegetation transpiration is essential to increasing understanding of interactions among vegetation, soil water, and groundwater. In this study, a HYDRUS-1D model was used to simulate the water uptake of two typical vegetation communities, Artemisia capillaris and Phragmites australis, in a floodplain wetland (Poyang Lake wetland, China). Vegetation transpiration was compared for two distinct hydrological conditions: high water table (2012) and low water table (2013). Results showed that vegetation transpiration in the main growth stage (July–October) was significantly influenced by WTD. Under high water table conditions, transpiration of A. capillaris and P. australis communities in the main growth stage totaled 334 and 735 mm, respectively, accounting for over 90% of the potential transpiration. Under low water table conditions, they decreased to 203 and 510 mm, respectively, due to water stress, accounting for merely 55% of the potential transpiration. Scenario simulations found different linear relationships between WTD and the ratio of groundwater contribution to vegetation transpiration. An increase of 1 m in WTD in the main growth stage may reduce the ratio by approximately 25%.