Direct-firing

Pre-Keformer A pre-reformer is based on the concept of shifting reforming duty away from the direct-fired reformer, thereby reducing the duty of the latter. The pre-reformer usually occurs at about 500°C inlet over an adiabatic fixed bed of special reforming catalyst, such as sulfated nickel, and uses heat recovered from the convection section of the reformer. The process may be attractive in case of plant retrofits to increase reforming capacity or in cases where the feedsock contains heavier components. 

Low capacity shaft kilns, direct-fired manually with bituminous coal, which were extant during 1900—1940, largely disappeared following World War 11 because of their high thermal and labor costs, poor lime quaUty, and offensive emission of black smoke. Another kiln that was phased out in the United... 

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). 

Type of cycle Conventional pulverized coal steam Eirst commercial MHD steam Advanced direct-fired... 

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

Condenser and eboiler AT. The losses for AT are typically far greater than those for reflux beyond the minimum. The economic optimum for temperature differential is usually under 15°C, in contrast to the values of over 50°C often used in the past. This is probably the biggest opportunity for improvement in the practice of distillation. A specific example is the replacement of direct-fired reboilers with steam (qv) heat. 

The first use of steam power as a replacement for the animal or human power that drove the cane mills occurred in Jamaica in 1768. This first attempt worked only a short time, but steam drive was used successfully a few years later in Cuba. Steam drive for the mills soon spread throughout the world. The use of steam instead of direct firing was soon appHed to the evaporating of the cane juice. 

The devolatilized coal particles are transported to a direct-fired multihearth furnace where they are activated by holding the temperature of the furnace at about 1000°C. Product quaUty is maintained by controlling coal feed rate and bed temperature. As before, dust particles in the furnace off-gas are combusted in an afterburner before discharge of the gas to the atmosphere. Finally, the granular product is screened to provide the desired particle size. A typical yield of activated carbon is about 30—35% by weight based on the raw coal. 

The lye boHer is usuaHy steam heated but may be direct-fired. Separation efficiency may be iacreased by adding a tower section with bubble-cap trays. To permit the bicarbonate content of the solution to buHd up, many plants are designed to recirculate the lye over the absorber tower with only 20—25% of the solution flowing over this tower passiag through the boHer. Several absorbers may also be used ia series to iacrease absorptioa efficieacies. 

A typical converter is made up of multiple furnaces, each of which contains 8 to 10 reactors. Each reactor is made up of 10 to 30 sintered alumina tubes lined with platinum. The furnaces are direct fired with natural gas to 1200—1300°C. A typical furnace can produce about 125 t per month of hydrogen cyanide. Catalyst life is approximately 10,000 h. 

MAX. ALLOWABLE WORKING UG-98 TEMPERATURE. DESIGN UG-19, UG-20 PRESSURE VESSELS SUBJECT TO DIRECT FIRING UW-2(d), U-I(h)... 

Pressure vessels subject to direct firing have special requirements relative to weided-joint design and postweld heat treatment. 

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

Fig. 29-15. Direct-fired afterburner. Source Los Angeles Air Pollution Control District.

Alfalfa dehydration is carried out in a direct-fired rotary dryer. The dried product is transported pneumatically to an air cooler and then to a collecting cyclone. The collected particles are ground or pelletized and then packaged for shipment. The major atmospheric emission from the process is particulate matter, which is controlled by baghouses. Odors may also be a problem, but they disperse rapidly and are no longer a problem at distances of over 1 km. 

Soda-lime glass accounts for about 90% of the U.S. production. It is produced in large, direct-fired, continuous-melting furnaces in which the... 

External Combustor (experimental). The heat exehanger used for an external-combustion gas turbine is a direct-fired air heater. The air heater s goal is to achieve high temperatures with a minimum pressure decrease. It consists of a rectangular box with a narrow convection section at the top. The outer casings of the heater consist of carbon steel lined with lightweight blanket material for insulation and heat re-radiation. 

Specification for dedicated liquefied petroleum gas appliances - Mobile and portable non-domestic forced convection direct fired air heaters. Superseded BS 4096 1967... 

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