Solid feed systems

During the winter of 1991, bulk mustard was drained from preheated (20°C) 1 ton containers into heavy-walled, polyethylene-lined cardboard boxes and allowed to freeze under cool conditions (<0°C). The boxes containing frozen mustard were then placed in sealed metal cargo containers and immediately transported to the incinerator site. The boxes were then off-loaded and processed via the rotary kiln solids feed system. All bulk mustard (3 tonnes) was destroyed in this manner as part of the incinerator test bum program (see below). 

Contaminated Scrap Contaminated, empty drums were shredded using a transportable metal shredder, packaged in cardboard boxes and fed into the incinerator via the solids feed system. The clean metal recovered from the ash discharge system was sold to a foundry and melted down into recyclable metal feedstock. Most of the scrap metal processing occurred during the warmer months. 

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). 

Similarly the solids feed system is generally asymmetric, feeding solids to one side of the reactor, or, for large units, to a limited number of discrete feed positions on the periphery of the reactor. 

Silva EMV, Ferreira MC, Freire JT. Mean voidage measurements and fluid dynamics analysis in a circulating fluidized bed with a spouted bed type solids feeding system. Proceedings of 2nd European Thermal-Sciences and 14th UIT National Heat Transfer Conference, Rome, 1996. 

Table 7-2 Advantages and disadvantages of solid feed systems (Ferretti, 1976) ...

The solids captured by the first cyclone are periodically removed and weighed by an automatically controlled ash removal system and can be reintroduced discontinuously into the solids feed system (figure 3). The solids captmed by the second cyclone are currently removed by a manually controlled lock hopper system. An automatically controlled ash removal system, similar to the one used for the first cyclone, will be installed in the second quarter of this year. 

A thickener has several basic components a tank to contain the slurry, feed piping and a feedwell to allow the feed stream to enter the tank, a rake mechanism to assist in moving the concentrated sohds to the withdrawal points, an underflow solids-withdrawal system, and an overflow launder. The basic design of a bridge-supported thickener mechanism is illustrated in Fig. 18-86. 

USATHAMA) completed a trial burn of explosive, contaminated soil in a rotary kiln (Noland, 1984). Soil contaminated from red and pink water lagoons was successfully burned. A transportable rotary kiln yrstem was set up. The technology by Therm-All, Inc., had been used in industry for destruction of solid wastes. The normal screw feed system was not used, due to fear of a soil explosion during the extruded plug feed process. Therefore, the soil was placed in combustible buckets and individually fed by a ram into the incinerator. The feed rate was 300 to 400 Ib/hr and the operational temperature was 1200° to 1600°F in the kiln and 1600° to 2000°F in the secondary chamber. 

Fluidized-bed process incinerators have been used mostly in the petroleum and paper industries, and for processing nuclear wastes, spent cook liquor, wood chips, and sewage sludge disposal. Wastes in any physical state can be applied to a fluidized-bed process incinerator. Au.xiliary equipment includes a fuel burner system, an air supply system, and feed systems for liquid and solid wastes. The two basic bed design modes, bubbling bed and circulating bed, are distinguished by the e.xtent to which solids are entrained from the bed into the gas stream. 

Condenser leaks permit dissolved solids, oxygen, organics, and suspended solids to enter the CR system and from there to enter the FW system. This is a very serious problem and leads to feed system fouling and deposition and the depassivation of metal surfaces, which in turn induces pitting corrosion to occur. 

STABREX is easier and simpler to use compared to any other oxidant available for industrial water treatment. The product is pumped directly from returnable transporters (PortaFeed Systems)17 with standard chemical feed equipment. Previously, the only practical ways to apply bromine were to oxidize bromide solutions on-site with chlorine in dual liquid feed systems, or with one of the solid organically-stabilized bromine products applied from sidestream erosion feeders. The former is cumbersome and complex, and the latter is prone to dusting and difficult to control. Other oxidants require complex handling and feed of toxic volatile gases, unstable liquids, multiple-component products, or reactive solids. Simplicity in use results in reduced risk to workers and to the environment. 

All the systems must have a means of bringing the solids and the gas stream together. Since the gas is under either vacuum or pressure, some sort of airlock is needed in order to prevent air either from being sucked into the system or from being blown into and through the feeding system. The most common solution is a rotary valve (see Fig. 8-9) driven by a motor. 

CH4 emitted from manure depends primarily on (i) the management system such as solid disposal system, liquid disposal systems, e.g., ponds, lagoons, and tanks, which can emit up to 80% of manure-based CH4 emissions, while solid manure emits little or no CH4. (ii) Environmental conditions are also important. The higher the temperature and moisture, the more CH4 produced, (iii) CH4 emissions also depend on the quantity of the manure produced, which depends on the number of animals housed, the amount of feed the consumed, and the digestibility of the feed, (iv) Manure characteristics depend on the animal type, feed quality, and rumen microbes present in the rumen and digestive tracks. Manure handled in liquid form tends to release more amount of CH4 when compared to solid or manures thrown into the pasture, which do not decompose anaerobically. High temperatures with neutral pH and high moisture content enhance CH4 production [45],... 

While using a screw conveyor to move the solid oxidant, ignition of a polypropylene tube in the feed system occurred. This could not be reproduced, even when likely contaminants were present. 

A schematic representation of this reactor model is shown in Figure 22.2. Particles of solid reactant B are in BMF, and fluid reactant A is uniform in composition, regardless of its flow pattern. The solid product, consisting of reacted and/or partially reacted particles of B, leaves in only one exit stream as indicated. That is, we assume that no solid particles leave in the exit fluid stream (no elutriation or entrainment of solid). This assumption, together with the assumption, as in the SCM, that particle size does not change with reaction, has an important implication for any particle-size distribution, represented by P(R). The implication is that P(R) must be the same for both the solid feed and the solid exit stream, since there is no accumulation in the vessel in continuous operation. Furthermore, in BMF, the exit-stream properties are the same as those in the vessel Thus, P(R) is the same throughout the system ... 

Flow Measurements Measurement of flow rates of clean gases presents no problem. Flow measurement of gas streams containing solids is almost always avoided. The flow of solids is usually controlled but not measured except solids flows added to or taken from the system. Solids flows in the system are usually adjusted on an inferential basis (temperature, pressure level, catalyst activity, gas analysis, heat balance, etc.). In many roasting operations, the color of the calcine discharge material indicates whether the solids feed rate is too high or too low. 

In addition to recycling reactants back into the reactor, there are several other tricks to keep reactants in the reactor and thus attain higher conversions and yields. Aunong these are formation of vapor-phase products from liquid or solid feeds and the use of membranes that pass products but retain reactants. We will discuss the integration of reactor-separation systems in Chapter 12. 

The capital cost included the complete powdered activated carbon system (tankage, blowers, pumps, instmments/controls, etc.), carbon feed system, sludge storage tank, filter press, O M manuals, startup and training services, no building. The O M cost covers the leachate treatment and solids dewatering. 

Due to the variable flow characteristics of powdered fillers, and the range of addition levels often demanded (for example, from 20 to 80% by weight), it is not possible to design a unified feed system for all materials [155]. Considerations include the operational design and accuracy required from the feeders, the location of filler addition (within solid or melt zones, or a combination of both) and the need to utilise a stuffer screw. A variety of feeding options are illustrated in Fig. 32. 

A fluidized bed is made up of a mass of particles buoyed up out of permanent contact with each other by a flowing fluid. Turbulent activity in such a bed promotes high rates of heat and mass transfer and uniformity of temperature and composition throughout. The basic system includes a solids feeding device, the fluidizing chamber with a perforated distributing plate for the gas, an overflow duct for removal of the dry product, a cyclone and other equipment for... 

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