Drop-tube furnace section

The experimental furnace is a vertically oriented laminar flow drop tube furnace having a 30 cm long uniformly hot test section with optical access. The fuel droplet array is introduced on the logitudinal axis concurrently with the ambient gas. The droplet stream is interrupted at several points in its trajectory by a sampling probe inserted axially from the base of the furnace. The probe quenches and transports the entire flow to a sampling train which recovers the fuel droplet residue for analysis. The above process is repeated at several furnace temperatures for each fuel. A detailed description of the system is to be found in references (3) and (4). 

Drop-tube furnace injector and preheater section. 

Experiments on the pyrolysis of cellulose were carried out in a controlled mixing history reactor (CMHR), which is a plasma-operated drop-tube furnace capable of operating at temperatures up to 2500 K. A schematic diagram of the CMHR is shown in Figure 15.1. The graphite core reactor tube is 2 inches in diameter and 60 inches long. The central test section of the reactor has two 24-inch long... 

The centerline gas velocity was approximated by doubling the bulk gas velocity. The bulk gas velocity was calculated as the volumetric gas flow rate divided by the cross sectional area of the tube inside the drop tube furnace. Stokes law was used to calculate the terminal velocity. At a temperature of 1700 C (3092°F). the calculated residence time for the coal particles was 186ms. The resulting devolatilization kinetics for petroleum coke are shown in Hgure 2.2. The devolatilization reactivity equations among various petroleum cokes will be reasonably consistent rather, the significant variability will come fi om the maximum volatile yield. 

After the waterwaH tubes deHver the saturated steam back into the top of the boHer dmm, moisture is separated out by a series ofbaffl.es, steam separators, and cormgated screens. The water removed drops down into the hot water contained in the steam dmm. The steam travels out through either a dry pipe, which leads to a superheater header, or a series of superheater tubes that connect directiy into the top of the steam dmm. The superheater tubes wind back into the top of the furnace and/or a hot flue-gas backpass section, next to the economizer, where heat from the combustion gases exiting the furnace superheats the steam traveling through the tubes. 

The pyrolysis apparatus consists of a vertical, electrically-heated Vycor tube (25 mm. I.D.) packed with 6-mm. lengths of Pyrex tubing (10 mm. O.D.) and mounted in an electric furnace about 45 cm. long (Notes 1 and 2). Attached to the top is a 100-ml. dropping funnel with a pressure-equalizing side arm that has an inlet for nitrogen (Note 3). A thermocouple well inside the tube holds a movable thermocouple and extends to the bottom of the heated section (Note 4). The bottom of the reactor is fitted to a 500-ml. side-arm flask packed in ice. The side arm leads to tw o traps in series cooled in ice and to a final trap cooled in a bath of dry ice and acetone (Note 5). 

In ideal conditions, a furnace operatmg on naphtha can run for 90 days without decoking. However, the run length is always shorter due to the inevitable fouling of the quench boiler. Progressive coke deposition in the pyrolysis tubes results in an increase in their metal skin temperature, connected with the growing ineffldency of heat transfer, and in an increase in the pressure drop caused by the redaction of the open cross section of the tube. 

Preparation (aj. 1,5-Pentanediol (Suppliers Union Carbide, Eastman) is acetylated, and the diacetate is dropped into a glass reaction tube mounted vertically in an electric furnace. The heated section of the tube is packed with glass rings 575 ... 

Sessile drop method is the most frequently used method (c.f. Section 6.2.4.1.). In the measurement at high temperatures the drop of the melt is lying on the solid base placed in a horizontal furnace tube. The contact angle is measured on photographs of the drop. 

The reactor section consists of a vertical electrically-heated furnace in which the reactor tube is placed. The furnace has separately controlled zones with appropriate temperature and heat input measurement facilities for each zone. Fluid temperature measurements are made along the length of the reactor with calibrated couples located in adiabatic zones and temperature profiles can be varied. Reactor pressures are continuously monitored and pressure drop (AP) and pressure profile across the reactor can be controlled. Since each reactor represents a specific commercial coil, multiple reactors have been designed to cover the commercial contact time range of interest. In these studies a reactor designed for operation between 0.01 and 0.10 seconds was employed. 

During tower operation, raw materials are pumped to a feed tank and mixed thoroughly. Mixing is usually accomplished with a pump-around loop or a mixer. This mixture is pumped to a feed preheater or furnace where the temperature of the fluid mixture is brought up to operating conditions. Preheaters are usually shell-and-tube heat exchangers or fired furnaces. This preheated fluid then enters the feed tray or section in the tower. Part of the mixture vaporizes as it enters the column, while the rest begins to drop into the lower sections of the tower. 

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