initial product of the decay of nitrogenous organic wastes, its presence being an indication of such wastes. Typically, the nitrate content in waters is low but can rise to appreciable levels in wastewater from agricultural activities as a result of soil fertilization. Also, nitrite derivatives are present in low concentration since these are rapidly oxidized to nitrates, while nitrite derivatives can be found in wastewaters from the microbiological reduction of nitrate or the oxidation of ammonia.
See also: Waste, Waste Disposal.
Basic Sediment and Water
The basic sediment and water (often referred to in a shortened form, such as BS&W, BSW) is the material which collects in the bottom of storage tanks and is usually composed of oil, water, and foreign matter, also called bottoms or bottom settlings. The material is also known as bottoms, bottom sediment, bottom settlings, sediment, and water.
The particulate matter is known as sediment or mud. The water content can vary greatly from fuel to fuel (conventional or alternate). The bulk of the water and sediment is usually separated as soon as possible after production to minimize the quantity that needs to be transported and/or transferred to subsequent processing units. Further, the residual content of these unwanted impurities is measured as bottom sediment and water (BS&W, ASTM D4007).
Thus, basic sediment and water are both a technical specification of certain impurities in any fuel and the method for measuring it. In many raw fuels (including fuels produced from biomass), the crude oil will contain some amount of water and suspended solid from the starting material. The particulate matter and the water content can vary greatly from feedstock to feedstock and from process to process. The bulk of the water and sediment is usually separated at the earliest possible convenience to minimize the quantity that needs to be transported further as well as any adverse effects on the process and process equipment.
Upon production of a fuel from a renewable source, the fuel typically passes through facilities that allow gas and water to separate from the crude and solids to settle out. These facilities may comprise a simple gathering tank or a series of specialized separation vessels, and may involve the addition of chemicals to the crude to aid in the separation of various contaminants from the crude oil and natural gas.
The BS&W test has been used to determine composition of the fuel from many sources and should be tested frequently to ensure it meets the prescribed quality requirements. There are two tests conducted, a bottom sediment and water test (BS&W) and a visual test. The BS&W test is done at the beginning, mid-point, and end of the fuel production train. Visual tests are conducted every fifteen minutes during the evolution. The visual criteria is simply that the fuel be clear and bright and the test is a quick and easy check of the fuel quality.
See also: Refining.
Batch-Type Processes
A batch process is usually performed over and over, and batch processes are a sub-class of sequential processes. Batch process refers to a process that involves a sequence of steps followed in a specific order. Also, batch processes generate a product but the sequential processes need not necessarily generate a product. Thus, batch processing is a technique for automating and processing multiple portions of a feedstock More generally, industrial processes can be divided into two categories of production which are (i) continuous processes and (ii) batch processes.
Continuous processes are designed to run at steady state, and to maximize the efficiency of these processes, it is necessary to keep the plant in the operating range under disturbances. The optimization task required to operate such processes is usually performed to achieve disturbance rejection, designing controllers to reach and maintain set-point effectively, and keeping the down time to a minimum. Since the operating range is generally very narrow, the system dynamics can often be approximated by linear dynamics.
Batch processes have a finite operating time, rather than a continuous operation. The control objective in batch processing is not to reach steady state, but to reach some desired objective by the end of the batch. This can involve movement through a very wide operating range, and non-linearity in the system can be strong. Batch optimization focuses on maximizing the performance objective by finding the corresponding input variable and state variable trajectories. Since batch production is usually of low volume, high value production, optimization of its operation is critical to make the process viable.
The most common type of process for acid gas removal is the batch-type process, and many involve a chemical process in which the acid gas reacts chemically with the cleaning agent, usually a metal oxide. These processes are not merely physical separation processes in which the acid gas is removed by a physical phenomenon, such as adsorption. Thus, the batch-type processes have the common requirement that the process be operated as a batch system where, at the end of the cycle, the chemical agent must be changed or regenerated in order to continue treating.
Batch processes are limited to removing small amounts of sulfur from fuels, especially when the flow rates of the gas streams and/or there are small concentrations of hydrogen sulfide. These processes include (i) the iron sponge process, (ii) the ChemSweet process, (iii) the SulphaCheck process, (iv) the SulphaTreat process, (v) the zinc oxide process, and (vi) the molecular sieve process.
Baumé Gravity
Baumé gravity is a unit of measurement of specific gravity used in the chemical industry for aqueous caustic soda and aqueous acid. Two arbitrary scales are employed, one for liquids lighter than water and the other for liquids heavier than water. This scale is also used to describe the density of acid solutions (Table B-2).
Table B-2 Explanation of the baumé gravity scale.
| For liquids heavier (More dense) than water | For liquids lighter (less dense) than water |
|---|---|
| 0° Bé is the distance the hydrometer sinks in pure water. 15° Bé is distance the hydrometer sinks in a solution that is 15% w/w sodium chloride (salt, NaCl) To convert from °Bé to specific gravity at 60 F: specific gravity = 145/(145 - °Bé) | 0o Bé is the distance the hydrometer sinks in a solution that is 10% w/w sodium chloride (salt, NaCl) 10° Bé is the distance the hydrometer sinks in o pure water. To convert from Bé to specific gravity at 60 F: specific gravity = 140/(130 + °Bé) |
Before standardization using specific gravity at the time of World War II, the Baumé scale was generally used in industrial chemistry and pharmacology for the measurement of density of liquids. Currently, the Baumé scale is still used in various industries such as sugar beet processing and in the starch industry and the density of liquid product produced from these two sources could well be presented in degrees Baumé.
Bauxite
Bauxite is an amorphous sedimentary rock that is the chief commercial ore of aluminum. It consists largely of hydrated alumina with variable proportions of iron oxides. In addition, bauxite is the main source of aluminum and gallium. The ore consists mostly of the aluminum minerals gibbsite [Al(OH)3], boehmite [γ-AlO(OH)], and diaspore [α-AlO(OH)] that are mixed with the two iron oxides: goethite [FeO(OH)] and hematite (Fe2O3) as well as the aluminum clay minerals kaolinite [Al2Si2O5(OH)] and small amounts of anatase (TiO2), and ilmenite (FeTiO3 or FeO.TiO2).
The principal aluminum hydroxide minerals found in varying proportions with bauxites are gibbsite and the polymorphs boehmite and diaspore. Bauxite ores