Hammerschmidt equation

The Hammerschmidt equation may be used in calculating the amount of inhibitor required in the water phase to lower the hydrate temperaiinv... 

Conventional pipeline calculations in which "dry" hydrocarbon flashes are performed to determine the hydrocarbon liquid formation the liquid water condensed is estimated using one of the available natural gas water content charts (1, 15), and the Hammerschmidt equation (11) and a graphical correlation are used to... 

Perform "wet"-methanol-hydrocarbon flashes to estimate the liquid water plus methanol and hydrocarbon phases the methanol concentration is adjusted to satisfy the Hammerschmidt equation prediction for the desired hydrate formation temperature depression. 

Hammerschmidt discovers hydrates as pipeline plugs provides Hammerschmidt equation discovers thermodynamic inhibitors 1941 Katz et al. begin -values and gas gravity methods to predict hydrate mixtures... 

Pieroen (1955) and Nielsen and Bucklin (1983) presented derivations to show the theoretical validity of the Hammerschmidt equation. The latter work suggested that the equation applies only to typical natural gases, and to methanol concentrations less than 0.20 mole fraction (typically for system operation at temperatures above 250 K). It may easily be shown (Yamanlar et al., 1991) that the Hammerschmidt equation should not apply to high concentrations of an inhibitor that might vaporize. Nixdorf and Oellrich (1996) have shown that the Hammerschmidt equation under-predicts natural gas systems inhibited with TEG. 

Nielsen and Bucklin (1983) presented an improved version of the Hammerschmidt equation which is accurate over a wider range, that is, to concentrations as large as 0.8 mole fraction. They suggested that Equation 4.8 may be effectively used to design methanol injection systems operating as low as 165 K... 

Pieroen (1955) provided a theoretical foundation for the Hammerschmidt equation, showing that when the solubility of one phase in the other is neglected, a nonvaporizing inhibitor such as salt can be approximated as... 

The simplest method of estimating the inhibiting effect is from the Hammerschmidt equation ... 

As noted earlier, typically methanol is used as the inhibitor. The molar mass of methanol is 32.042 g/mol, which is required in the Hammerschmidt equation. 

To use the Hammerschmidt equation you must first estimate the hydrateconditionswithoutaninhibitorpresent.TheHammerschmidt equation predicts only the deviation from the temperature without an inhibitor present, not the hydrate forming conditions themselves. 

From figure 5.3 H2S forms a hydrate at 30°C and 8 MPa. From the Hammerschmidt equation, what weight per cent methanol is required to depress the hydrate temperature by 18°C ... 

For comparison, from figure 5.2 the depression in a 35 wt% methanol is about 12°C. This is very good agreement and should not otherwise be expected. The Hammerschmidt equation is a crude approximation. 

The following equation may be used instead of Figure 17-8. Hammerschmidt developed the equation30... 

Equation 4.7 was based on more than 100 experimental determinations of equilibrium temperature lowering in a given natural gas-water system in the inhibition concentration range of 5-25 wt% of the free water. The equation was used to correlate data for alcohols and ammonia inhibitors. Hammerschmidt (1939) provided for a modification of the molecular weight M when salts were used as inhibitors. Unfortunately, no information on the gas composition and no listing of the individual experimental data were provided. The assumption is normally made that the gases used by Hammerschmidt were methane-rich. 

Due to a cancellation of errors, the equation (without modification) is applicable for aqueous ethylene glycol concentrations to about 0.40 mole fraction (typically for system operation to 233 K). A comparison of results from Hammerschmidt s equation, as well as the prediction by the freezing point depression of water for methanol inhibition is summarized in Table 4.6. 

In general, the higher the fat content of the product the higher the taste threshold concentration (Chapters 4, 9, 13). vom Bruck and Hammerschmidt (1977) developed an equation that relates the fat content of the food product to the taste threshold concentration ... 

Hammerschmidt and Richarz (1991) determined the mass transfer coefficients using a rotating disk of 12.6cm area and an electrochemical reaction (these reactions are usually very fast hence mass transfer dominates). The mass transfer coefficients varied from 3,5 X 10 to 40 X 10 cm/s at 25 "C with increasing stirrer rpm. Then they studied the kinetics of the Grignard reaction of bromocyclopentane with magnesium and used the overall rate constant thus obtained to get the chemical reaction rate constant from Equation El5,4.2. 

The first step in the design of an injection system is determining the minimum inhibitor concentration required to prevent hydrate formation. Hammerschmidt (1934) developed an equation based on experimental data for methanol that has been widely used for both methanol and glycol, but is applicable only at low inhibitor concentrations (below about 20%... 

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