Unless specifically defined in the Texas Clean Air Act (TCAA) or in the rules of the commission, the terms used by the commission have the meanings commonly used in the field of air pollution control. In addition to the terms that are defined by the TCAA, the following terms, when used in this division (relating to Cement Kilns), have the following meanings, unless the context clearly indicates otherwise. Additional definitions for terms used in this division are found in §§3.2, 101.1, and 117.10 of this title (relating to Definitions).
  (1) Clinker--The product of a portland cement kiln from which finished cement is manufactured by milling and grinding.
  (2) Indirect-firing system--A system that reduces the amount of primary air used in a cement kiln by:
    (A) separating the powdered fuel from the air stream that carries the fuel from the drying/milling equipment;
    (B) storing the fuel briefly; and
    (C) using an independent, significantly smaller stream of hot primary air to blow the fuel to the burner.
  (3) Long dry kiln--A kiln that employs no preheating of the dry feed. The inlet feed to the kiln is dry.
  (4) Long wet kiln--A kiln that employs no preheating of the dry feed. The inlet feed to the kiln is a slurry.
  (5) Low-NOX burner--Either of the following:
    (A) for long wet kilns, combustion equipment designed to reduce flame turbulence, delay fuel/air mixing, and establish fuel-rich zones for initial combustion; or
    (B) a type of cement kiln burner that results in decreasing nitrogen oxides emissions and that has an indirect-firing system and a series of channels or orifices that:
      (i) allow for the adjustment of the volume, velocity, pressure, and direction of the air carrying the fuel (known as primary air) and the combustion air (known as secondary air) into the kiln; and
      (ii) impart high momentum and turbulence to the fuel stream to facilitate mixing of the fuel and secondary air.
  (6) Low-NOX precalciner--A process in which a portion of the fuel is injected near the raw material feed end of a preheater or precalciner kiln, resulting in a reducing atmosphere in the preheater or precalciner.
  (7) Mid-kiln firing--Secondary combustion in long dry or long wet kilns by injecting solid fuel at (or to) an intermediate point in the kiln using a specially-designed feed injection mechanism for the purpose of decreasing nitrogen oxides emissions through:
    (A) burning part of the fuel at a lower temperature; and
    (B) reducing conditions at the solid fuel injection point that may destroy some of the nitrogen oxides formed upstream in the kiln burning zone.
  (8) Portland cement--A hydraulic cement produced by pulverizing clinker consisting essentially of hydraulic calcium silicates, usually containing one or more of the forms of calcium sulfate as an interground addition.
  (9) Portland cement kiln--A system, including any solid, gaseous, or liquid fuel combustion equipment, used to calcine and fuse raw materials, including limestone and clay, to produce portland cement clinker.
  (10) Precalciner kiln--A kiln where the feed to the kiln system is preheated in cyclone chambers and utilizes a second burner to calcine material in a separate vessel attached to the preheater before the final fusion in a kiln that forms clinker.
  (11) Preheater kiln--A kiln where the feed to the kiln system is preheated in cyclone chambers before the final fusion in a kiln that forms clinker.
  (12) Secondary combustion--A system that employs a second combustion point in addition to the primary flame. This definition includes mid-kiln firing in long dry and long wet kilns, and also additional combustion at the raw material feed end of the kiln in preheater-precalciner kilns.

Source Note: The provisions of this §117.3101 adopted to be effective June 14, 2007, 32 TexReg 3206