Abstract: A method and a mixture for chemically stabilizing electric arc furnace dust (EAFD) containing thallium by entrapping the metals inherent in EAFD within a cementitiously hardened product from the mixture. The method includes using the pozzolanic characteristics of EAFD by forming a mixture of EAFD with sufficient water, ferrous sulfate, and Portland cement, then permitting the mixture to react to form a product having a decreased concentration of thallium in its leachate. The method may also include permitting the mixture to form a cementitiously hardened product. The composition of the present invention is the mixture of EAFD, water, ferrous sulfate, and Portland cement. Even immediately after forming the mixture and before hardening, the composition has acceptable leachate characteristics. The hardened product also has acceptable leachate concentrations.

Abstract: A method for producing portland cement includes adding stabilized electric arc furnace dust (EAFD) to the raw materials fed into the feed end of a rotary cement kiln to form a cement clinker. The untreated EAFD is preferably stabilized by forming a mixture of water, lime, and a cementitious reactant consisting of untreated electric arc furnace dust. Preferably, dolomitic lime is used and ferrous sulfate is added to the mixture. The stabilized EAFD, which is so soft that no grinding is necessary, may be nonetheless passed through the grinding mill along with the cement raw materials (excluding stabilized EAFD), combined with the raw materials after the raw materials are ground, or delivered directly to the rotary cement kiln in a stream separate from the cement raw materials. The stabilized EAFD serves as an inexpensive iron source in place of iron ore, mill scale, coal ash, or others.

Abstract: A buffering agent for a cementitious hazardous waste composition, containing electric arc furnace dust (EAFD) and water, includes dolomitic lime, namely either dolomitic quicklime, dolomitic monohydrated lime or dolomitic dihydrated lime. Dolomitic lime serves as a buffering agent for the hazardous waste composition by maintaining the pH of the waste composition within a target range over which solubility of several heavy metals tends to be minimized. These heavy metals include lead, zinc and cadmium, among others, and the pH range within which the heavy metals experience a minimum solubility is approximately 8.5 to 11.5, and preferably 9.4 to 10.2. In addition, dolomitic lime is substantially insoluble in water, so that the buffering agent will not leach or diffuse out of the waste composition.

Abstract: An improved pug mill mixer including at least one homogenizer shaft extending transverse to the direction of the pug mill shafts for providing a zone of high shear mixing. The pug mill mixer of the present invention is particularly well-suited to mix dry, fine powders with liquids and pasty, sticky sludges, such as flue gas desulfurization (FGD) sludge. The mixer includes a container, within which is disposed at least one pug mill shaft having a series of pug mill paddles coupled to and radially protruding from the pug mill shafts for mixing the mixture and transporting the mixture along the pug mill shafts. The homogenizer shafts extend in a direction transverse to the pug mill shafts. Homogenizer mixing elements are coupled to and radially protrude from the homogenizer shafts. The homogenizer shafts rotate at a relatively high speed for producing a zone of high shear mixing. A liquid injection nozzle injects liquid into the container near the feed port of the container.

Abstract: A method for transporting a cementitious mixture to an underground space includes subjecting the mixture to high-shear mixing to render it temporarily flowable and, while the mixture remains in its flowable state, transporting the mixture to the underground space. After a period of time following the high-shear mixing, the mixture reverts to its initial viscosity and subsequently reacts to form a cementitiously hardened product. The mixture used in the present invention includes flue gas desulfurization sludge, lime, fly ash and water.

Abstract: A process for the production of a water-insoluble, abrasion-resistant, synthetic solid article or aggregate, as well as the products produced thereby. Fly ash, lime, water and FGD sludge are mixed intimately and formed at pressures exceeding 1,000 psi, preferably 4000-8000 psi. The product is cured for at least the equivalent of 28 days at 73.degree. F., and crushed and sized to produce a commercial aggregate, for example, for concrete, asphalt, concrete masonry units, etc.

Abstract: A method and a mixture for chemically stabilizing electric arc furnace dust (EAFD) by entrapping the metals inherent in EAFD within a cementitiously hardened product from the mixture. The method includes using the pozzolanic characteristics of EAFD and forming a mixture of EAFD with sufficient water and lime, as necessary, and then allowing the mixture to react to form a cementitiously hardened product. The hardened product has acceptable leachate concentrations, permeability characteristics and unconfined compressive strength.

Abstract: An abrasion resistant synthetic aggregate made from an intimately intermixed combination of lime, fly ash and sulfate/sulfite sludge (e.g. FGD sludge), mixed to the point where the mixture is nearly optimum density and compressible or non-compressible and plastic. This mixture is placed in a landfill. After a relatively brief cure period, the landfill is ripped and the material is crushed and graded. The aggregate, which in some instances may qualify as a light weight aggregate, has a Los Angeles Abrasion Resistance of less than 60%, and may in some cases be less than 50% (medium particles passing) according to that test.

Abstract: Processes for the production of a hardenable mass having low permeability characteristics are disclosed, as well as the compositions produced thereby. The process includes providing a slurry produced from the scrubbing of sulfur oxide-containing gases with alkaline earth metal compounds, the slurry comprising an aqueous suspension of alkaline earth metal sulfites, mixing the slurry with a pozzolanically active waste material such as fly ash and an alkaline earth metal in the form of an alkaline earth metal hydroxide or a hydratable alkaline earth metal oxide in amounts so as to provide an overall composition including greater than about 3.

Abstract: Method for disposing of (or converting to a construction material) physically unstable wastes comprised of non-biologic, organic, water insoluble compounds, usually dispersed in water, by incorporation thereof in a lime-fly ash water mixture which hardens under atmospheric conditions to form an environmentally acceptable, impermeable, load-bearing material.