Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/02—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in air or gases by adding vapour phase inhibitors

Definitions

• the present invention relates to a method for protection of process equipment with significant vapour pressure.
• part or parts If the constituent parts (hereafter part or parts) are kept in contact with flowing gas there will normally be a net transport of the evaporating component from the process equipment part to the gas and thereby a continuous mass loss of the part. In certain cases this continuous mass loss may limit the lifetime of the part. Such degradation caused by evaporative mass loss is an important mechanism of what is normally referred to as high temperature corrosion.
• Examples of process applications where high temperature corrosion may limit the lifetime of the parts include gas and steam turbines, engines, boilers, burners, incinerators, coal gasifiers, fuel cells, membrane reactors, aerospace applications, exhaust systems, high temperature filtration, hot gas clean up, and various industrial high temperature processes (chemical, petrochemical, etc).
• a chemical component already present in the gas e.g. steam
• A(g) A(s).
• Such condensation may lead to a growing layer on the walls of said parts or formation of particles that may be carried with the gas.
• clogging of narrow gas passageways, e.g. gas channels and orifices may occur.
• the evaporation from one part may not only degrade and limit the lifetime of this part, but also degrade and limit the lifetime of a second process equipment part where condensation occurs.
• This is illustrated in Figure 1 , where evaporation from process equipment part PE1 degrades both PE1 and a second process equipment part PE2 where condensation takes place.
• the main objective of the present invention was to arrive at a method for the protection of process equipment that otherwise would degrade due to evaporation of one of the chemical components from which the equipment is constructed.
• Another objective was to arrive at a method for the protection of process equipment that otherwise would degrade due to condensation of gas components evaporated from other process equipment parts.
• the amount of evaporating component added should either be equal to or higher than the amount corresponding to the equilibrium pressure above the process equipment part from which evaporation would otherwise occur. Said added component will evaporate into the gas stream prior to entering said equipment or equipment part. Thus, no evaporation will occur from the part. Furthermore, the amount of evaporating component added should be lower than the amount corresponding to the equilibrium pressure above the pure condensed phase of the component or above any reaction product that may potentially form between the evaporating component and the process equipment part. Ideally the amount of added evaporating component should be carefully controlled and be equal to the amount corresponding to the equilibrium pressure above the process equipment part from which evaporation would otherwise occur.
• Figure 2 The principle of adding to the gas stream a controlled amount of gas component A(g) that would otherwise evaporate from the process equipment part PE1 is illustrated in Figure 2.
• the gas component is added from a source of A, hereafter referred to as Source, upstream of PE1. Evaporation of A(g) in PE1 and thereby degradation of PE1 is thus avoided because there is no chemical potential gradient or driving force for the evaporation.
• Figure 2 also illustrates the collection of A(g) in a device, hereafter referred to as Collector, downstream of PE1 but upstream of a second process equipment part PE2.
• Collector The collection of A(g) in the Collector prevents condensation and deposition in PE2, thereby eliminating a potential cause for degradation of PE2.
• the Source may be in the form of a solid structure containing the condensed phase of the evaporating component or a compound of which the evaporating component is a constituent.
• the Source should then contain enough of the evaporating chemical component, A, to prevent A from being fully consumed during the target lifetime of the process equipment, or the source should be replaceable.
• Said solid structure may be in the form of a channel structure, porous structure, fibre containing structure, powder containing structure or particle containing structure having a high internal surface area from which the evaporating component may be evaporated.
• the Source may be a spray nozzle or similar equipment injecting a water solution or another fluid containing the evaporating component into the gas stream.
• the Source may also be a suitable feeder (e.g. cell feeder, screw feeder), feeding dust or powder particles containing or consisting of the evaporating component into the gas stream.
• A(g) + D(s) AD(s).
• This embodiment of the Collector is more efficient in collecting the evaporating component than the embodiment of the Collector where simple condensation takes place. This is due to the lower equilibrium pressure of A(g) above AD(s) than above A(s).
• Said solid structures may be in the form of a channel structure, porous structure, fibre containing structure, powder containing structure, or particle containing structure, having a high internal surface area where the evaporated component is collected.
• the Collector should be sufficiently open structured to prevent significant increase in the pressure drop due to clogging during the target lifetime of the process equipment, or the Collector should be replaceable.
• Figure 1 shows the principle of evaporation of gas component A(g) from one process equipment part (PE1 ) and condensation of A(s) in another process equipment part (PE2) downstream of PE1 , thereby degrading and limiting the lifetime of both PE1 and PE2.
• Figure 2 shows the principle of adding to the gas stream a controlled amount of a gas component A(g) that would otherwise evaporate from the process equipment part PE1 , and the collection of A(g) before the gas enters process equipment part PE2.
• the gas component is added from a Source situated upstream of PE1 and collected in a Collector situated downstream of PE1 and upstream of PE2.
• the Source prevents evaporation from and degradation of PE1
• the Collector prevents condensation in and degradation of PE2.
• Figure 3 shows an experimental set up where a sample tube is kept in a furnace where hot steam is heated and is flowing through the inside of the sample tube and then quenched to liquid water.
• Figure 4 shows a SEM micrograph of a lanthanum and nickel based oxide compound tube surface after exposure to hot flowing steam for three weeks. The surface is substantially degraded.
• Figure ⁇ shows a SEM micrograph of a lanthanum and nickel based oxide compound tube surface after exposure to hot flowing steam for three weeks, where the steam has first passed a Source containing nickel. The surface shows no sign of degradation.
• Figure 6 shows a SEM micrograph of the internal surfaces of a Collector comprising a highly porous device of an aluminium containing compound after exposure to nickel containing hot flowing steam for three weeks. The micrograph reveals that crystallites have grown on the Collector internal surfaces.
• a sample tube comprising a lanthanum and nickel based oxide compound was kept in a furnace where steam at 10 bar pressure was flowing through the inside of the sample tube for three weeks as illustrated in Figure 3.
• the inlet temperature of the sample tube was 1050 0 C and the temperature gradually decreased through the sample tube such that the outlet sample tube temperature was 900 0 C.
• the steam was quenched and thus converted to liquid water.
• a sample of the condensed water was collected daily and analysed by ICP-MS (Ion Coupled Plasma - Mass Spectrometer) to quantify the content of nickel, lanthanum and other chemical components.
• ICP-MS Ion Coupled Plasma - Mass Spectrometer
• the analyses of the condensed water samples showed a nickel content of 0.7 micromole per litre of water and a lanthanum content of 0.2 micromole per litre of water.
• the nickel is assumed to have evaporated from the sample tube as Ni(OH) 2 (g) and the lanthanum is assumed to have spalled off from the sample tube as a secondary effect of the evaporation of nickel.
• This hypothesis is supported by the SEM micrograph of the inlet section of the sample tube shown in Figure 4. Degradation of the inner surface is clearly visible and the flake-like particles were shown by EDS (Electron Dispersive Spectroscopy) to be rich in lanthanum, with a negligible content of nickel.
• a similar SEM micrograph of the sample tube outlet section shows an unaltered surface with a chemical composition identical to that of the pristine sample tube. This experiment demonstrates the degradation of the sample tube through evaporation of one of the chemical constituents of the tube.
• Example 2 The experiment described in Example 1 was repeated, but an additional tube, a Source tube, comprising a nickel containing compound was placed in the furnace upstream of the sample tube.
• the inlet temperature of the Source tube was 800 0 C and the temperature gradually increased through the Source tube such that the outlet Source tube temperature was 1050 0 C.
• the analyses of the condensed water samples showed a nickel content of around 1.0 micromole per litre of water.
• the nickel is assumed to have evaporated from the Source tube as Ni(OH) 2 (g).
• SEM micrographs of all sections (inlet, middle and outlet) of the inner surface of the sample tube after three weeks of hot steam exposure show unaltered surfaces with chemical composition identical to that of the pristine tube.
• the SEM micrograph of the inlet section of the sample tube is shown in Figure 5. This experiment demonstrates the protection of the sample tube from evaporation by the introduction of a Source tube upstream of the sample tube.
• Example 2 The experiment described in Example 2 was repeated, but an additional device, Collector, comprising a highly porous solid structure of an aluminium containing compound was placed in the furnace downstream of the sample tube.
• the inlet temperature of the Collector was 900 0 C and the temperature gradually decreased through the Collector such that the outlet Collector temperature was 800 0 C.
• the analyses of the condensed water samples showed a nickel content of 0.07 micromole per litre of water.
• the reduced content of nickel relative to the experiment described in Example 2 is assumed to be caused by the collection of nickel in the Collector.
• SEM micrographs of all sections (inlet, middle and outlet) of the inner surface of the sample tube after three weeks of hot steam exposure show unaltered surfaces with chemical composition identical to that of the pristine tube.
• Example 2 The experiment described in Example 1 was repeated, but a nickel containing water solution was continuously sprayed into the hot steam through a cooled nozzle upstream of the sample tube. SEM micrographs of all sections (inlet, middle and outlet) of the inner surface of the sample tube after three weeks of hot steam exposure show unaltered surfaces with chemical composition identical to that of the pristine tube. This experiment demonstrates the protection of the sample tube from evaporation by the introduction of a Source in the form of a liquid injected into the gas stream upstream of the sample tube.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
• Gas Separation By Absorption (AREA)

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Citations (4)

• 2006
  • 2006-07-12 NO NO20063247A patent/NO20063247L/no not_active Application Discontinuation
• 2007
  • 2007-06-27 WO PCT/NO2007/000236 patent/WO2008007967A1/en not_active Ceased

Patent Citations (4)

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