Methane cleaning

Secunda discharges no process water effluents. AU. water streams produced are cleaned and reused in the plant. The methane and light hydrocarbons in the product are reformed with steam to generate synthesis gas for recycle (14). Even at this large scale, the cost of producing fuels and chemicals by the Fischer-Tropsch process is dominated by the cost of synthesis gas production. Sasol has estimated that gas production accounts for 58% of total production costs (39). 

Methanation of the clean desulfurized main gas (less than 1 ppm total sulfur) is accompHshed in the presence of a nickel catalyst at temperatures from 260—400°C and pressure range of 2—2.8 MPa (300—400 psi). Equations and reaction enthalpies are given in Table 4. 

The potential of natural gas, which typically has 85—95% methane, has been recognized as a plentiful and clean alternative feedstock to cmde oil (see Gas,natural). Estimates (1 3) place worldwide natural gas reserves at ca 1 x (3.5 x 10 ft ) corresponding to the energy equivalent of ca... 

In general, the proven technology to upgrade methane is via steam reforming to produce synthesis gas, CO + Such a gas mixture is clean and when converted to Hquids produces fuels substantially free of heteroatoms such as sulfur and nitrogen. Two commercial units utilizing the synthesis gas from natural gas technology in combination with novel downstream conversion processes have been commercialized. 

The carbon black (soot) produced in the partial combustion and electrical discharge processes is of rather small particle si2e and contains substantial amounts of higher (mostly aromatic) hydrocarbons which may render it hydrophobic, sticky, and difficult to remove by filtration. Electrostatic units, combined with water scmbbers, moving coke beds, and bag filters, are used for the removal of soot. The recovery is illustrated by the BASF separation and purification system (23). The bulk of the carbon in the reactor effluent is removed by a water scmbber (quencher). Residual carbon clean-up is by electrostatic filtering in the case of methane feedstock, and by coke particles if the feed is naphtha. Carbon in the quench water is concentrated by flotation, then burned. 

Methane is mainly used as a clean fuel gas. Approximately one million BTU are obtained by burning 1,000 ft of dry natural gas (methane). It is also an important source for carbon black. 

Although interesting from a mechanistic point of view, alkane halogenation is a poor synthetic method for preparing alkyl halides because mixtures of products invariably result. For example, chlorination of methane does not stop cleanly at the monochlorinated stage but continues to give a mixture of dichloro, trichloro, and even tetrachloro products. 

Lee, A. L., Methanation for Coal Gasification, Clean Fuel for Coal Symp. 

Sfi f-Test 6.13B Methanol is a clean-burning liquid fuel proposed as a replacement for gasoline. Suppose it could be produced by the controlled reaction of the oxygen in air with methane. Find the standard reaction enthalpy for the formation of I mol CHjOH(l) from methane and oxygen, given the following information ... 

A definition based upon the NMHC concentration might require nonmethane hydrocarbons to contribute insignificantly to atmospheric reactivity. Such a region might still contain very low concentrations of nonmethane hydrocarbons, so long as their sum total reactivity does not significantly contribute to that of methane and carbon monoxide. This is to say, in clean air... 

At levels of nonmethane hydrocarbons where their reaction rates with HO are a significant fraction of the reaction rate of HO with CO and methane, it may happen that the clean-air HO concentration remains unchanged. This would result if the increase in HO removal by NMHC s is compensated by increasing HO sources such as aldehyde or ketone photolysis and reactions such as R21. These considerations are examined below. 

We have previously examined the mutual dependence of [HO ] upon [NO,jj and [NMHC] as calculated by a combined clean/polluted air chemical mechanism (76), and extend those calculations here to the more modem CAL mechanism of Lurmann et al. (182). To do this we have combined the NO,/NMHC chemical reactions of the CAL mechanism with the methane chemistry of Logan et al. (58). The results of these calculations are shown as contour maps or isopleths for [O3], [HO ], and [HO2 ] in Figure 7. Figure 7a, for ozone, is similar to isopleths used to determine reductions in NMHC and/or... 

The steam reforming of natural gas process is the most economic near-term process among the conventional processes. On the other hand, the steam reforming natural gas process consists of reacting methane with steam to produce CO and H2. The CO is further reacted or shifted with steam to form additional hydrogen and CO2. The CO2 is then removed from the gas mixture to produce a clean stream of hydrogen. Normally the CO2 is vented into the atmosphere. For decarbonization, the CO2 must be sequestered[l,2]. The alternative method for hydrogen production with sequestration of carbon is the thermal decomposition of methane. 

Figure 1 Mass spectrometer (MS) intensities versus surface temp ature in a rqnesentadve temperature programmed desorpticm (TPD) profile of methyl on a clean Ni(lOO) surface. Total exposure was 1 L. Adsorption temperature was 105 K and heating rate was 3 K/s. Methane is produced near 225 K.

In summary, from a clean-up point of view, the main hard point for NOvTrap concerns a process of richness >1, which minimizes methane emissions. 

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