Hot-box process

With Hot-Box dehydration, one inch thick test samples are dehydrated completely in 50 seconds by contact with hot, >230 C, metal plattens In this process the sand is heated by conduction so the rate of dehydration varies with the thickness of the sand body The Hot-Box process is inefficient since there are significant energy losses by radiation from the hot metal patterns however, Hot-Box equipment is readily available in the casting industry ( ) ... 

This process is very similar to the hot-box process and uses the same production techniques. Only the type of resin differs, allowing curing at a lower temperature. However, this kind of resin is significantly more expensive than those in use in the hot-box process. Therefore the warm-box process, in spite of some real advantages, is not generally find widespread use. 

Warm-box emissions Compared to the hot-box process, the emissions are significantly lower. The emissions do not contain phenol or ammonia, and also formaldehyde emissions are diminished by a factor of 4. As Ae pattern temperature is also lower compared to the one used for the hot-box process, the woiking conditions are also improved. The environmental impact is considered to be relatively low... 

Shell emissions Compared to the hot-box process, cured sand consumption is very low. However, the pre-coated sand contains 2 to 3 times more resin, but as the pattern temperatures are approximately the same, the resulting impact on working conditions is... 

Table 3.42 Mass balance data for brass foundry core using a hot-box process [177, Silva Ribeiro, 2002]...

In the industrial tests the mixtures of spent foundry sands (supplied directly from the foundry) containing sands with furan resin, sands from the cold-box and hot-box processes as well as sands with bentonite and coal dust were applied. 

Furan hot-box resins are used in both ferrous and nonferrous foundries (66,67). In this process, resin and catalyst are intimately mixed with dry sand and then blown into heated metal boxes containing a cavity the shape of the desired core. In seconds, the surface of the sand mass hardens and, as soon as the core has cured sufficiently to be rigid and handleable the box is opened and the core removed. Automotive cores with exceUent dimensional accuracy and high strengths are made via this forty-year-old process. 

Different foundry casting techniques are used. Included are plastic-based binders mixed with sand. Various types of molds and cores are produced that include no-bake or cold-box, hot-box, shell, and oven-cured. Usual binders are phenolic, furan, and thermoset polyester. There is the foundry shell casting, also called dry-mix casting. It is a type of process used in the foundry industry, in which a mixture of sand and plastic (phenolic, thermoset polyester, etc.) is placed on to a preheated metal pattern (producing half a mold) causing the plastic to flow and build a thin shell over the pattern. Liquid plastic pre-coated sand is also used. After a short cure time at high temperature, the mold is stripped from its pattern and combined with a similar half produced by the same technique. Finished mold is then ready to receive the molten metal. Blowing a liquid plastic/sand mix in a core-box also produces shell molds. 

The residence times in Box 6.3 are based on riverwater being the only input of ions to the oceans. This is a simplification as there are also inputs from the atmosphere and from hydrothermal (hot water) processes at mid-ocean ridges (Fig. 6.7). For major ions, rivers are the main input, so the simplification in Box 6.3 is valid. For trace metals, however, atmospheric and mid-ocean ridge inputs are important and cannot be ignored in budget calculations (Section 6.5). 

Direct metering of liquids/solids, followed by immediate vaporization in a vessel, also can be used. For metering of liquids (either neat, or as solutions of solids), flowmeters and various dispensing pumps are available (Figs. l-2a,b and 1-3, Tables 1-1 and 1-2). The final vaporization takes place in, for instance, a hot box - a vessel containing objects held at high temperature. This process should be differentiated from aerosol CVD (see Sect. 1.3.1.5). For some compositions, direct solid feed systems have been proven as a delivery mode (Fig. 1-4, Table 1-3). 

Table 2.10 gives the relative share of the various core-making processes in German automobile foundries in 1991. This shows that the amine cold-box and hot-box systems dominate the market. Over 90 % of the automobile foundries use the amine cold-box system. The other processes (croning, C02-silicate) are mainly used for supplementary use, i.e. making cores with specific requirements (size, thickness,...). 

The battery development process included a large number of cell tests. For instance, in order to characterize the cells, the usable power was measured over SOC and temperature. Furthermore, early in the process, cell abuse tests were performed to qualiiy their usage in a vehicle production program. Such abuse tests included overcharge, overdischarge, short-circuit, nail-penetration, hot-box and crush procedures. 

Five basic fabrication processes are used by the foundry industry. These are the no-bake, cold-box, hot-box or warm-box, oven bake, and shell processes. 

Texturing. The final step in olefin fiber production is texturing the method depends primarily on the appHcation. For carpet and upholstery, the fiber is usually bulked, a procedure in which fiber is deformed by hot air or steam jet turbulence in a no22le and deposited on a moving screen to cool. The fiber takes on a three-dimensional crimp that aids in developing bulk and coverage in the final fabric. Stuffer box crimping, a process in which heated tow is overfed into a restricted oudet box, imparts a two-dimensional sawtooth crimp commonly found in olefin staple used in carded nonwovens and upholstery yams. 

Small loads are commonly processed in a box furnace. The product is placed on the furnace hearth through a door. Box furnaces may be single-ended or double-ended. A single-ended box furnace is usually used in an air atmosphere appHcation where the product can be removed hot from the furnace for cooling. A double-ended box furnace is usually used in a controlled atmosphere appHcation. In this case a water cooler is attached to one end. The product can be placed on the hearth (in the heat chamber) through the front door, then after the product reaches temperature, it is manually transferred into the water cooler for cooling before it is manually removed out the exit door on the other end of the water cooler. 

There is some debate about what controls the magnesium concentration in seawater. The main input is rivers. The main removal is by hydrothermal processes (the concentration of Mg in hot vent solutions is essentially zero). First, calculate the residence time of water in the ocean due to (1) river input and (2) hydro-thermal circulation. Second, calculate the residence time of magnesium in seawater with respect to these two processes. Third, draw a sketch to show this box model calculation schematically. You can assume that uncertainties in river input and hydrothermal circulation are 5% and 10%, respectively. What does this tell you about controls on the magnesium concentration Do these calculations support the input/removal balance proposed above Do any questions come to mind Volume of ocean = 1.4 x 10 L River input = 3.2 x lO L/yr Hydrothermal circulation = 1.0 x 10 L/yr Mg concentration in river water = 1.7 X 10 M Mg concentration in seawater = 0.053 M. 

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