Hydrocarbons destruction/removal

Methane (contained in natural gas) and carbon monoxide also make good surrogates because they are relatively easy to obtain, handle, and meter. Furthermore, common CEM analyzers detecting CO and unburned hydrocarbons (UBH) can be used to measure their presence for determining destruction removal efficiency. 

Emissions from hazardous waste combustors are regulated under two statutory authorities RCRA and the CAA. The MACT standards set emission limitations for dioxins, furans, metals, particulate matter, total chlorine, hydrocarbons/carbon monoxide, and destruction and removal efficiency (DRE) for organics. Once a facility has demonstrated compliance with the MACT standards by conducting its comprehensive performance test (CPT) and submitting its notification of compliance (NOC), it is no longer subject to the RCRA emission requirements with a few exceptions. RCRA-permitted facilities, however, must continue to comply with their permitted emissions requirements until they obtain modifications to remove any duplicative emissions conditions from their RCRA... 

Limited data is available on the concentration of volatile organic compounds, semi-volatile organic compounds (SVOCs), and polycyclic aromatic hydrocarbons (PAHs) from gasification processes. The data that is available indicate that VOCs, SVOCs, and PAHs are either non-detectable in flue gas streams from IGCC process or, in some cases where they were detected, they are at extremely low levels (on the order of parts per billion and lower). The analysis of syngas also indicates greater than 99.99 percent chlorobenzene and hexachlo-robenzene destruction and removal efficiencies and part per billion or less concentration of selected PAHs and VOCs.9-14... 

The HRUBOUT process is a mobile in situ or ex situ thermal desorption process designed to remediate soils contaminated with volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs). For the ex situ process, excavated soil is treated in a soil pile or in a specially designed container. Heated compressed air is injected into the soil, evaporating soil moisture and removing volatile and semivolatUe contaminants. Heavier hydrocarbons are oxidized as the soil temperature is increased to higher levels over an extended period of time. The vapor is collected and transferred to a thermal oxidizer (incinerator) for destruction. 

The S.A.V.E. technology is self-contained and equipped with a traUer-hitch mount for transportation. Hydrocarbon vapors recovered through the system s remedial actions are directed to the engine intake where they are burned as part of the normal engine combustion process, which often eliminates the need for process waste stream controls and external power sources. Emissions from the engine are passed through a small catalytic converter to maximize the destruction of removed hydrocarbons. 

Bombardment of a hexadecanethiol SAM on Au or Ag by 800 eV He+ ions first produces local disordering followed by removal and/or scission of molecules of the SAM that remain upright.61 Loss of H2 leads to formation of olefins, and the hydrocarbon chains continue to fragment until the sub-layer of strongly chemisorbed S atoms is uncovered. The rate of destruction of the SAM on Au was double that of the rate of destruction of the SAM on Ag. 

Several methods, involving solvent extraction or destructive hydrogenation, can accomplish the removal of aromatic hydrocarbons from naphtha. By destructive hydrodegation methods, aromatic hydrocarbon rings are first ruptured and then saturated with hydrogen, which converts aromatic hydrocarbons into the odorless, straight-chain paraffinic hydrocarbons required in aliphatic solvents. 

Crude oil contains about 0.01% metals and up to 5% sulfur present in large aromatic structures. These levels are highly dependent on the origin of the crude. For example, California crude is relatively low in sulfur but higher in metals than crude from Kuwait. Any process to remove them must be economical with little destruction of the hydrocarbons and minimum consumption of H2. The catalyst is Co, Mo/A1203 with particles a few mm in diameter. Although sulfur is usually a poison for catalytic reactions it is used here in a positive function to control selectivity. It is presulfided to decrease activity towards excessive consumption of H2 that leads to unwanted saturation of aromatic molecules. 

Ultrasound-assisted emulsification in aqueous samples is the basis for the so-called liquid membrane process (LMP). This has been used mostly for the concentration and separation of metallic elements or other species such as weak acids and bases, hydrocarbons, gas mixtures and biologically important compounds such as amino acids [61-64]. LMP has aroused much interest as an alternative to conventional LLE. An LMP involves the previous preparation of the emulsion and its addition to the aqueous liquid sample. In this way, the continuous phase acts as a membrane between both the aqueous phases viz. those constituting the droplets and the sample). The separation principle is the diffusion of the target analytes from the sample to the droplets of the dispersed phase through the continuous phase. In comparison to conventional LLE, the emulsion-based method always affords easier, faster extraction and separation of the extract — which is sometimes mandatory in order to remove interferences from the organic solvents prior to detection. The formation and destruction of o/w or w/o emulsions by sonication have proved an effective method for extracting target species. 

Although the process is commonly named deodorization, it is actually a combination of three different effects on the oil (1) stripping Stripping of volatile components (free fatty acids, odorous compounds, tocopherols, sterols, and contaminants such as pesticides and light polycyclic aromatic hydrocarbons, etc.), (2) actual deodorization Removal of different off-flavors, and (3) temperature effect Thermal destruction of pigments and unwanted side reactions such as cis-trans-iso-merization, polymerization, conjugation, and so on. 

The emulsion leaving the reactor enters a settler. Residence times there often average up to 60 min to permit separation of the two liquid phases. Most of the acid phase is recycled to the reactor, being injected near the eye of the impeller. The hydrocarbon phase collects at the top of the decanter it contains unreacted isobutane, alkylate mixture, often some light n-paraffins, plus small amounts of di-isoalkyl sulfates. The sulfates must be removed to prevent corrosion problems in the distillation columns. Caustic washes are often employed to separate the sulfates they result in destruction of the sulfates. Acid washes have the advantage that most of the sulfates eventually react to reform sulfuric acid, which is reused, and to produce additional alkylate product. 

Ceria was also proposed as a component of catalysts for the removal of chlorinated hydrocarbons [54]. The process is based on the destmctive adsorption of the chlorinated hydrocarbons on metal oxides [55]. It was demonstrated that CaO and MgO were able to convert CCI4, CHCI3 and C2CI4 to COj and COClj and the corresponding metal chlorides at temperature around 400-500°C in the absence of an oxidant, such as oxygen. Ceria has shown comparable properties CCI4 destruction started at around 450°C, and was accompanied by the reduction of Ce(IV) to Ce(III) and by the formation of CeOCl as intermediate product. 

If the efficiency of destruction of the harmful substance is to be above 90%, then the residence time of the pollutants in the oxidation zone should be approximately 0.5 s and the temperature must not decrease below its limit value (500 to 650°C for the combustion of hydrocarbons and 750 C in the presence of carbon monoxide) and the destruction of malodorous substances require temperature above 800°C. Such thermal combustion can be employed in petroleum refining plants and in the petrochemical industry, for removing hydrocarbons from final gases, for removing vapours of solvents in the chemical and woodworking industry, and in steel works, etc. 

---