Direct firing system

The flow of the combustion gases in direct-fired systems may be concurrent (i.e., the gases flow in the same direction as the feedstock) or countercurrent (i.e., the gases flow opposite to the movement of the feedstock). The benefits of a concurrent system are higher treatment temperatures, longer residence times, and treatment of fines. Countercurrent systems offer more efficient heat transfer, and lower volumes and temperatures of off-gas. ° In large part due to the beneficial aspects of the off-gas and consequent simplified APC system, countercurrent systems are used more commonly in rotary kilns. 

Yagi, H. and Hideaki, K. (1995) High-temperature humidity sensor using a limiting-current-type plane multi-oxygen sensor for direct firing system. Sens. Actuators B, B25 (1—3), 701—4. 

Direct firing systems All systems in which the pulverized coal is fed directly to the rotary kiln downstream of the coal pulverizer (mill) without any intermediate storage. 

The relative advantages of an indirect firing system against a direct firing system focus on the consistency of PF feeding to the burner, the effect of primary air quantity on the process and emissions, and the effect of water vapor. For safety, the indirect firing system needs more safety measures to be implemented to reduce the risk of fire or explosion to an acceptable level by installation of the explosion doors and inertization system with carbon dioxide or nitrogen. 

Biopower is the use of biomass to generate electricity. Biopower could also be called biomass power. There are several different ways to generate electricity using biopower. The most common method is a direct-fired system biomass (such as plant stalks) is burned to heat water and create steam, which then drives a turbine (see Chapter 9). The turbine turns a generator that produces electricity. In efficient systems, the steam could also be used to heat buildings after it passed through the turbine. 

Pulverized fuel can be delivered and fired in kilns either directly (direct system) or indirectly (indirect system). The simplest and most commonly used system for pulverized fuel firing is the direct-fired system (Figure 6.7). 

Fig.45 Direct firing system (F. L. Smidth Tirax Mill)...

On the other hand, roller mills have already long established themselves as very suitable for coal grinding, i. e., for the production of pulverized fuel (see Section 5.5.2). The widespread return to pulverized coal and lignite in cement manufacture is having a stimulating effect on the development and optimization of these mills which, for this type of work, are usually of relatively small size and operated with direct firing systems. 

In principle, a distinction can be drawn between the direct firing system and the indirect system. In the former, the pulverized coal is fed direct from the grinding mill (with reference to fuel grinding it is often called a "pulverizer") to the burner, the coal being carried in a stream of air which passes through the mill and is supplied as primary air to the kiln. On the other hand, in the indirect system the pulverized coal, separated from its carrying medium, is temporarily accommodated in an intermediate storage bin, from which it is fed independently to the burner. 

Fig.49 Semi-direct firing system (Loesche GmbH)...

Two principal systems—the bin system and the direct-firing system— have been used for processing, distributing, and burning pulverized coal. The direct-firing system is almost exclusively the one being installed today. 

Direct-Firing System. The pulverizing equipment developed for the direct-firing system permits continuous utilization of raw coal directly from the bunkers. This is accomplished by feeding coal of a maximum top size directly into the pulverizer, where it is dried as well as pulverized, and then dehvering it to the burners in a single continuous operation. Components of the direct-firing system are illustrated in Fig.6.20. 

In the direct-firing system the operating range of a pnlverizer is usually not more than 3 to 1 (without change in the number of burners in service) because the air velocities in lines and other parts of the system must be maintained above the minimum levels to keep the coals in suspension. Most boiler units are provided with more than one pulverizer, each feeding multiple burners. Load variations beyond 3 to 1 are accommodated by shutting down (or starting up) a pulverizer and the burners it supphes. 

Burning Equipment for Pulverized Coal, The burner is the principal component of equipment for firing pulverized coal. Coal must be pulverized to the point where particles are small enough to assure proper combustion (Table 6.15). In the direct-firing system the coal is dried... 

Chemical Regeneration. In most MHD system designs the gas exiting the toppiag cycle exhausts either iato a radiant boiler and is used to raise steam, or it exhausts iato a direct-fired air heater and is used to preheat the primary combustion air. An alternative use of the exhaust gas is for chemical regeneration, ia which the exhaust gases are used to process the fuel from its as-received form iato a more beaeftcial oae. Chemical regeaeratioa has beea proposed for use with aatural gas and oil as well as with coal (14) (see Gas, natural Petroleum). 

Pig. 5. Schematics of (a) direct-firing hot-fan system for pulverized coal and (b) low NO burner for coal firing. 

FIG. 12-104 Open spray-drying system with direct-fired heater. (NIRO, Inc. )... 

Ontos. Designated as the M-50, this US Marine Corps system is a full-track self-propelled direct-fire and antitank weapon. It is aimed with six 106mm recoilless rifles, one. 30cal machine gun, and four. SOcal spotting rifles. It has a top speed of 40mph and a crew of three Ref J. Quick, Dictionary of Weapons and Military Terms , McGraw-Hill, NY (1973), 334... 

Perform, as directed, maintenance and repair on nuclear weapons, radar, and inertial fuzes, Permissive Action link Devices, ADM Firing Systems, and Adaptation Kits... 

Boilers may be direct fired or indirect fired. Energy supply designs account for various combustion methods using fossil fuels, municipal waste, process residues, waste heat, and by-products. Special boiler combustion systems to reduce pollution or improve efficiency include fluidized-bed and combined cycle. 

ESD system components that are located in areas that would be considered direct fire exposures, i.e. within or above fire hazardous risk areas should be provided fire protection measures to ensure integrity during ESD operation and the duration of the major efforts to control the emergency. 

Telephone numbers of the National Response Center, the fire department, the police department, and the ambulance department, or if there is a direct alarm system, instmctions on how to use it and... 

Various glycol regeneration methods were considered, such as direct-fired glycol reboilers, o direct-fired indirect hot oil system, electricol heating ond waste heat recovery. A direct-fired in-direct hot oil system was finally selectd because it provided a safe, well proven regeneration system which could be accommodated within the platform space limitations. 

The selected system comprises three direct-fired hot oil heaters, surge vessels ond circulation pumps. The hot oil is circulated in a closed loop through the tube bundles in the glycol reboilers. The system allows accurate control of the glycol tempercture ond by designing the fired heaters os a redundant utility system cvailoble to the three process troins the reliability of the system is thereby improved. 

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