Coke Gas Purification

The dynamic behavior of the coke gas purification process has been investigated systematically (139,140,145). For instance, local perturbations of the gas load and its composition have been analyzed. A significant dynamic parameter is represented by the liquid holdup. Figure 20 demonstrates the changes of the solvent composition after a decrease of the gas-flow rate from 67 m3/h to 36.4 m3/h and a simultaneous small increase in the liquid-flow rate. 

In this section, four examples illustrating the application of the rate-based modeling approach discussed above are presented. First three reactive absorption processes -namely absorption of NOx, coke gas purification and CO2 absorption by aqueous... 

Pilot-plant experiments have been carried out at real process conditions in the coke plant August Thyssen (Duisburg, Germany). The DN 100 pilot column (Fig. 9.11) was made from stainless steel and equipped with about 4 m of structured packing (Sulzer MELLAPAK 350Y), three liquid distributors, and a digital control system. Several steady-state experiments have been compared with the simulation results and supported the design optimization of the coke gas purification process [91]. 

Similar to the case of coke gas purification (see Section 9.5.2), this complex reactive absorption problem is solved by a purely numerical method. The liquid film is... 

Gorbunov, N. S., Glovatskii, V. G., Sukhomlin, A. I., et al. (1977). Corrosion protection of pipe systems functioning in coke gas purification media. Koks Khim. (6), 43-45 (in Russian). 

Coke and coke chemicals Treatment of (a) sulfurous by-product gas streams from coke gas purification (b) sulfurous gaseous and liquid by-products from benzene, toluene, xylene rectification units... 

Absorption is a commonly applied operation in chemical processing. It is used as a raw material or a product recovery technique in separation and purification of gaseous streams containing high concentrations of organics (e.g., in natural gas purification and coke by-product recovery operations). In absorption, the organics in the gas stream are dissolved in a liquid solvent. The contact between the absorbing liquid and the vent gas is accomplished in countercurrent spray towers, scrubbers, or packed or plate columns. 

Today s coke plant gas purification processes are mostly carried out under atmospheric pressure, employing a circulated ammonia-based absorbent. The consumption of the external solvent is reduced via the use of ammonia available in the coke gas (138). An example of innovative purification processes is the ammonia hydrogen sulfide circulation scrubbing (ASCS) (Figure 17), in which the ammonia contained in the raw gas dissolves in the NH3 absorber and then the absorbent saturated with the ammonia passes through the H2S absorber to selectively absorb the H2S and HCN components from the coke gas. The next step is the thermal regeneration of the absorbent with the steam in a two-step desorption plant, whereas a part of the deaciditied water is fed back into the H2S absorber (25). 

Figure 17 Ammonia hydrogen sulfide circulation scrubbing process for the coke oven gas purification (right) and H2S absorber (left).

Removal of harmful substances Coke oven gas purification Carbon dioxide removal by amines/ amine blends/ hot potassium carbonate solutions NOx removal Gas purification 63, 89, 91, 105-107... 

Blaugas Coal Coal briquettes, hot Coal gas, 2.3 Coal gas, compressed, 2.1, 2.3 Coal tar, crude and solvent Coal tar distillates, flammable, 3, 3.2,3.3 Coal tar naphtha Coal tar oil Coke, hot Creosote Creosote (coal tar or wood tar) Creosote salts Cresols (o-, m-, p-), 6.1, 8 Cresols (ortho- meta- para-), liquid or solid, 6.1 Dead oil Fischer Tropsch gas Fischer-Tropsch gas compressed, 2.2 Iron oxide, spent (obtained fix)m coal gas purification), 4.2 Iron sponge, spent, 4.2 Iron sponge, spent (obtained from coal gas purification), 4.2 Prilled coal tar Synthesis gas Synthesis gas, compressed Water gas Water gas, compressed... 

Richter, E. Knoblauch, K., and Juntgen, H., Mechanisms and kinetics of sulphur dioxide adsorption and NOx reduction on active coke. Gas Sep. Purif, 1(1), 35-43 (1987). 

In the blast furnace, under the influence of the coke, the iron oxide is reduced to raw iron and the material is separated into recyclable products. Zinc is vaporized in the blast furnace and reclaimed in the gas purification process in the form of zinc concentrate, which is forwarded to zinc foundries. The raw iron is run off from the blast furnace in elementary form and the slag recycled. 

Ammonia, hydrogen sulfide, and carbon dioxide are major impurities in coke oven gas (COG). In addition to these three components, COG often contains caibon disulfide, carbonyl sulfide, hydrogen cyanide, organic acids, pyridine, phenol, and other impurities, which can cause problems with conventional amine plants. The presence of large quantities of ammonia in these gases naturally led to consideration of its use for removal of HjS and CO2, and several ammonia-based coke oven gas purification processes have been developed and commercialized. 

Processes that use aqueous ammonia to remove H2S and CO2 are still offered for coke-oven gas purification, and many such plants are in operation in the U.S. and Europe however, it appears that the trend for new operations is toward the use of other absorbents. Other absorption processes that may be applicable for COG purification include the Takahax, Stretford, Vacuum Carbonate, Potassium Carbonate, and Sulfiban (MEA) processes. These processes can be designed to avoid serious adverse effects of trace impurities in the gas, and generally provide somewhat higher H2S removal efficiency than ammonia scrubbing. The processes are described in detail in other chapters (see index). 

Since most of the early gas purification work was related to the processing of manufactured and coke-oven gas streams, which contain ammonia as well as hydrogen sulfide, attempts were made to develop combination processes that would remove both impurities while producing marketable products such as ammonium sulfate and elemental sulfur. The first processes of this type were based on a recirculating solution of ammonium polythionate. They proved technically feasible, but quite complex, and were not commercially successful. 

Field test data showing the effects of natural gas composition and flow rate are given by Enneking (1966). The use of adsorption to recover hydrocarbons from gas streams at refineries and petrochemical plants is described by Cantrell (1982). The recovery of benzol (a benzene-rich light oil) from manufactured and coke-oven gas streams was formerly an important application of activated carbon adsorption, but is no longer considered significant. A typical benzol removal installation is described by Howell (1943) and Walker et al. (1944). Hydrocarbon recovery processes are not described in detail herein because of their similarity to solvent recovery processes and the fact that they are intended primarily for recovery, not gas purification. 

The removal of hydrocarbon vapors from gas streams by absorption in liquid oils is an important part of many industrial operations. In some cases, such as natural gasoline recovery, the absorption step is but a portion of a refining process that produces several commercial products, and the gas purification aspects of the operation are of little importance. In other cases, such as the removal of aromatics from coke-oven gas, the absorption process serves to improve the value of the product gas. Processes for the removal of light oil (primarily benzene) and naphthalene from coke-oven gas are described in this section. 

Hydrogen sulfide in manufactured gases may range from approximately 2.30 g/m (100 gr/100 ft ) in blue and carbureted water gas to sever hundred grains in coal- and coke-oven gases. Another important sulfur impurity is carbon disulfide, which may be present in amounts varying from 0.007 to 0.07 percent by volume. Smaller amounts of carbon oj sulfide, mercaptans, and thiophene may be found. However, most of the impurities are removed during the purification process and either do not exist in the finished product or are present in only trace amounts. 

In Japan, there is a project aimed at capturing the considerable volume of hydrogen gas which can be obtained as a by-product steel production. R D will focus on the purification process of fuel from coke oven gas to an acceptable level for fuel cell utilisation. METI, the Japan Research and Development Centre for Metals and Nippon Steel are working on the project with a 2003 budget allocation of 549 million. Japan also operates the 4C/.f project which aimsto develop an optimum coal gasifier for fuel cells and the establishment of gas clean-up system for purification of coal gas to the acceptable level for utilisation for MCFC and SOFC. The budget allocations for 2000-2003 total 4.6 billion. 

Thermal dehydrochlorination of 1,2-dichloroethane188-190 272 273 takes place at temperatures above 450°C and at pressures about 25-30 atm. A gas-phase free-radical chain reaction with chlorine radical as the chain-transfer agent is operative. Careful purification of 1,2-dichloroethane is required to get high-purity vinyl chloride. Numerous byproducts and coke are produced in the process. The amount of these increases with increasing conversion and temperature. Conversion levels, therefore, are kept at about 50-60%. Vinyl chloride selectivities in the range of 93-96% are usually achieved. 

COAL TAR AND DERIVATIVES. CAS 65996-93-2. Coal tar constitutes the major part of the liquid condensate obtained from the dry" distillation or carbonization of coal (mostly bituminous) to coke. The three inajor products of this distillation are (I) metallurgical coke. (2) gas which is suitable as a fuel after appropriate chemical treatment, and (3> condensable liquids which leave the coke oven along with the gas and which are constituted principally of ammonia liquor and coal tar. The condensable materials and gas impurities are separated from gas in the condensation and purification train of the coke oven plant. The purified coke oven gas is used as fuel in heal the coke ovens and steel producing furnaces. Prior to the widespread use of natural gas as a dnmeslic fuel, coke oven gas was widely used for this purpose after additional purification as residential fuel. 

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