Water injection systems selection

Postcombustion processes are designed to capture NO, after it has been produced. In a selective catalytic reduction (SCR) system, ammonia is mixed with flue gas in the presence of a catalyst to transform the NO, into molecular nitrogen and water. In a selective noncatalytic reduction (SNCR) system, a reducing agent, such as ammonia or urea, is injected into the furnace above the combustion zone where it reacts with the NO, to form nitrogen gas and water vapor. Existing postcombustion processes are costly and each has drawbacks. SCR relies on expensive catalysts and experiences problems with ammonia adsorption on the fly ash. SNCR systems have not been proven for boilers larger than 300 MW. 

Several classical ion-selective electrodes (some of which are commercially available) have been incorporated into continuous systems via suitable flow-cells. In fact, Lima et al. [112] used a tubular homogeneous crystal-membrane (AgjS or AgCl) sensor for the determination of sulphide and chloride in natural and waste waters. However, the search for new active materials providing higher selectivity and/or lower detection limits continues. Thus, Smyth et al [113] tested the suitability of a potentiometric sensor based on calix[4]arene compounds for use in flow injection systems. They found two neutral carriers, viz. methyl-j3-rerr-butylcalix[4]aryl acetate and... 

Figure 4.14 — (A) Flow injection system for the preconcentration and determination of copper P peristaltic pumps A 0.5 M HNOj B sample q = 2.5 mL/min) C water (jq = 0.5 mL/min) E 1 M NaNOj/O.l M NaAcO, pH 5.4 q = 0.5 mL/min F 1 M NaAcO/2 x 10 M Cu pH 5.0 (9 = 1.0 mL/min) 3-5 valves ISE copper ion-selective electrode W waste I and II 2 and 3 mL of chelating ion exchanger for purification III 100 fil of chelating ion exchanger for metal ion preconcentration. (B) Scheme of the flow system for the determination of halides A 4 M HAcO/1 M NaCl/0.57 ppm F B 1 M NaOH/0.5 M NaCl C, mixing coil (1 m x 0.5 mm ID PTFE tube) Cj stainless-steel tube (5 cm x 0.5 mm ID) ISE ion-selective electrode R recorder. (Reproduced from [128] and [129] with permission of Elsevier Science Publishers and the Royal Society of Chemistry, respectively).

Data-dependent acqnisition (DDA) is a mode of operation, where the MS experiment performed in a particular scan is based on the data acqnired in a previons scan. In a simple form, a DDA experiment switches the instrument from full-scan MS acquisition to full-scan product-ion MS-MS when the total-ion intensity or a selected-ion intensity exceeds a preset threshold. This avoids the need to perform two consecutive injections for the identification of unknowns in a mixture first to obtain the m/z values for the intact protonated molecules of the unknowns, and second to acquire the product-ion MS-MS spectra of these unknowns in a time-scheduled procedure, switching between various preselected precursor ions as a function of the chromatographic retention time. The DDA was promoted by Thermo Finnigan upon the introduction of the API-ion trap combinations [44-46]. Similar procedures are available for other commercial ion-trap systems, as well as for triple-quadrupoles, e.g.. Information Dependent Acquisition (IDA) from Applied Biosystems MDS Sciex, Data-directed Analysis (DDA) from Waters, and Smart Select from Bruker. 

In conclusion, for determination of inorganic compounds in water, reliable sampling processes are necessary, followed by spectrometric techniques that assure low detection limits as well as good selectivity and reliability of analytical information. The rapidity and reliability of the spectrometric methods proposed for inorganic compound assay in water caused them to be used in a flow injection system with good results. Through utilization of these methods in flow injection systems, an increase in reliability of the analytical information was achieved. 

Flow injection is a method using on-line discrimination chemical reactions. Direct selective preconcentration is performed on microcolumns, the analytes being concentrated up to three to four orders of magnitude and injected into the detector. Usually as separation techniques ion-exchange, liquid-liquid extraction, gas diffusion are used. Flow injection systems are connected either to ETA AS or ICP-AES detection systems. These methods have been used for determinations of redox species such as Crflll)/ Cr(IV), Fe(II)/Fe(III), As(III)/As(V), Se(IV)/Se(VI) in soil extracts and water samples. 

In pipe systems on the platform, the most severe corrosion attacks have been found between the wellhead and the first-stage separator, where water is precipitated, and where pressure, temperature as well as flow velocity are highest [8.29]. To a great extent, the attacks are localized in and at welds, in pipe joints, bends, and at places with reduced pipe diameter. (In many cases the attacks at welds could have been avoided by proper selection of welding consumables.) When the water content exceeds a critical level, the attacks become more severe. This is probably the reason for increased corrosion when the producing wells get older (the content of water increases with time due to water injection). 

In the bulk phase-separation approach, an organic solution of a polymer dissolved in a water-miscible solvent is injected into the tissue defect. After injection, the solvent diffuses away from the injection site, resulting in precipitation of the water-insoluble polymer. Selection of an appropriate solvent, which must be non-cytotoxic and not harmful to host tissue, is a key factor for success of the bulk phase-separation system. Two solvents that meet these criteria are N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO). In recent years, improved strategies for removal of the solvent and release of growth factors have been active areas of investigation. However, the requirement of a solvent to induce phase separation of the polymer limits the scale at which this approach can be applied in vivo. Even for relatively biocompatible solvents such as NMP and DMSO, injection of large volumes is anticipated to adversely affect host tissue, as well as the ability to eliminate the solvent from the body. 

The injection system was selected by comparison of a rotary valve injector with a fixed 10 jjI injection loop and a Waters U6K septumless injection system. The U6K injection system makes the exclusion of oxygen easier than the rotary valve injector. Care must be taken that the vent of the injector loop is at the same level as the point of injection because of syphonic penetration of oxygen into the sample loop. 

In recent years, GC-ion-trap detection (ITD) systems that can perform tandem MS (MS-MS) on a routine basis have become commercially available [86]. Because ITD provides good sensitivity as well as increased selectivity in the MS-MS mode, an on line SPE-GC ITD system was optimized for the trace-level determination of polar and apolar pesticides [53]. The Autoloop interface (see section 3.2.3) was operated at an injection temperature of 90X, which permitted the determination of thermolabile pesticides such as carbofuran and carbaryl. With sample volumes of 10 to 30 ml and a copolymer SPE cartridge, linear calibration curves were obtained for several pesticides over the range of 0.1 to 500 ng/L. Fully satisfactory tandem mass spectra were obtained at levels as low as 0.1 ng/L level in tap and river water. The system was used to analyze water from European and Asian rivers, and the determination of microcontaminants at 8 to 16 ng/L levels did not cause any problems (Fig. 11). Relevant analytical data are presented in Table 7. One conclusion may be that, for this target-compound type of analysis, a sample volume of 1 ml or less will be sufficient to comply with governmental directives. 

Although small quantities of sour water may be disposed of by injection into deep wells or by adding to the plant waste water disposal system, these are not viable options for most plants. Normally the sour water is either processed in a sour water stripper (SWS), which produces a vapor phase containing both ammonia and acid gases, or it is selectively stripped in a two-colunon system such as the Chevron WWT process, which produces separate ammonia and hydrogen sulflde-rich gas streams. 

Brine levels have considerable significance in the selection of inhibitors. If a field is on water injection, breakthrough to some wells will affect water composition and corrosive properties. In such cases analytical data may be required from a number of wells in the system. Production from different zones may also give rise to different corrosion characteristics and inhibitor distribution ratios between oil and water phases. 

---