This term refers to any of the elements of the halogen family, i.e., fluorine, bromine, chlorine, iodine, astatine (Lapedes 1976).
This is a chemical process or reaction in which a halogen element is introduced into a substance, generally by use of the element itself (Lapedes 1976).
Hazardous Solid Waste (see Waste generation).
In metal casting, the hearth is the portion of a reverberatory furnace on which the molten metal or bath rests.
High Pressure Heat Exchange System (HiPHES).
DOE's Office of Industrial Technologies is co-sponsoring the development of an advanced ceramic high-pressure, heat-exchange system to produce methanol via the process, "steam/methane reforming." The HiPHES will offer industry significant energy savings with associated reduced CO2 emissions; a compact, modular unit that can be used in remote locations; and excess electricity production that can be sold as a by-product. Conventional reformers use metal heat-exchange tubes that operate at temperatures of 1600o F, limiting the yield of gas. With ceramic tubes, the reaction temperatures will reach 1900o F, increase the yield beyond 85 percent, and require a lower input of natural gas. In addition to methanol production, the new technology has the potential to be applied where high-temperature heat exchangers are needed in the chemical-processing industries (DOE 1992a).
Hydraulic Cement (see Cement, Portland cement).
Hydrogen fluoride (HF) is a solvent and an intermediate in chemical syntheses such as the alkylation of isoparafins.
Hydrogen (H2) is a highly flammable gas that is a feedstock for and by-product of many industrial processes. It can also be used as a fuel, although it is actually an energy "carrier" since it costs energy to produce hydrogen. It is estimated that 3.8 billion standard cubic feet daily (SCFD) of hydrogen is used by industry (Fong and Simonsen 1993). U.S. petroleum and chemical industries produce very large volumes of hydrogen-containing waste streams, which are estimated at 800x106 SCFD. Hydrogen gas recovery is not typically an economical alternative, and the hydrogen from these waste streams is either released to the atmosphere as dilute gas or burned as fuel to produce steam. Industrial hydrogen-containing waste streams contain about 10 percent to 40 percent hydrogen at pressures of 0 to 150 psi (DOE 1997d). The volume of the hydrogen waste gas stream in the year 2010 is estimated to be 1.1x109 SCFD. In 1996, 271 bcf of hydrogen was produced in this country (American Chemical Society 1997b).
Hydrogen sulfide (H2S) is a very toxic waste gas produced during petroleum refining and natural gas production. Together, these two industries generate approximately 30x109 lb/yr of H2S. In the petroleum-refining process, H2S is produced as an intermediate product in the de-sulfurization of sour crude oil. In a closed reaction with a byproduct, the H2S is decomposed into sulfur and water. H2S is found with some natural gas deposits and must be removed from the natural gas before it can be used. H2S cannot be emitted into the atmosphere in large concentrations because it is a regulated gas under the Clean Air Act. The current waste-treatment technology (Claus gas-phase partial oxidation followed by a tail-gas clean-up processthe SCOT process, for example) recovers 99.0 percent to 99.5 percent of the sulfur in hydrogen sulfide, with the remaining 0.5 percent to 1.0 percent being emitted into the atmosphere as sulfur dioxide. The hydrogen that was produced in the first step of the overall hydrocarbon cleaning process is converted into water and purged from the process. This technology consumes about 730x106 Btus/yr per plant for a 158 long ton/day sulfur recovery unit or about 90x1012 Btus/yr for the S. refining industry. The H2S target of opportunity is about 3x1010 lb/yr. The potential energy that can be recovered by the utilization of H2S is 30x1012 Btus/yr (Energetics 1986).