Reactor pilot unit scale

Acetic acid is a cosssodity chemical produced by Union Carbide Corporation via the liquid phase oxidation of butane. While acetic acid is the principal product, methyl ethyl ketone and ethyl acetate are valuable by-products. Large scale gas-liquid reactors are used to practice this technology. In general the plant reactor performance was inferior in both productivity and selectivity when contrasted to pilot unit scale reactors carrying out the same reaction under equivalent conditions. 

Early in the development of a new process, a productivity loss was encountered when the process was moved from the exploratory scale reactor to a larger pilot unit scale reactor. After study of many factors, the problem was resolved by installing a second impeller on the pilot reactor mixing shaft. While the action produced the desired results, it was not apparent why the one impeller system had performed below expectations. The traditional scale-up criterion of horsepower/unit voluaie for mixed vessels had been used when moving from the exploratory to pilot reactor. Historically this criteria had proved to be satisfactory. 

In cases where a large reactor operates similarly to a CSTR, fluid dynamics sometimes can be estabflshed in a smaller reactor by external recycle of product. For example, the extent of soflds back-mixing and Hquid recirculation increases with reactor diameter in a gas—Hquid—soflds reactor. Consequently, if gas and Hquid velocities are maintained constant when scaling and the same space velocities are used, then the smaller pilot unit should be of the same overall height. The net result is that the large-diameter reactor is well mixed and no temperature gradients occur even with a highly exothermic reaction. 

Economy of time and resources dictate using the smallest sized faciHty possible to assure that projected larger scale performance is within tolerable levels of risk and uncertainty. Minimum sizes of such laboratory and pilot units often are set by operabiHty factors not directly involving internal reactor features. These include feed and product transfer line diameters, inventory control in feed and product separation systems, and preheat and temperature maintenance requirements. Most of these extraneous factors favor large units. Large industrial plants can be operated with high service factors for years, whereas it is not unusual for pilot units to operate at sustained conditions for only days or even hours. 

Sasol uses both fixed-bed reactors and transported fluidized-bed reactors to convert synthesis gas to hydrocarbons. The multitubular, water-cooled fixed-bed reactors were designed by Lurgi and Ruhrchemie, whereas the newer fluidized-bed reactors scaled up from a pilot unit by Kellogg are now known as Sasol Synthol reactors. The two reactor types use different iron-based catalysts and give different product distributions. 

The predictions checked in the pilot-plant reactor were reasonable. Later, when the production unit was improved and operators learned how to control the large-scale reactor, performance prediction was also very good. The highest recognition came from production personnel, who believed more in the model than in their instruments. When production performance did not agree with model predictions, they started to check their instruments, rather than questioning the model. 

Ross (R2) measured liquid-phase holdup and residence-time distribution by a tracer-pulse technique. Experiments were carried out for cocurrent flow in model columns of 2- and 4-in. diameter with air and water as fluid media, as well as in pilot-scale and industrial-scale reactors of 2-in. and 6.5-ft diameters used for the catalytic hydrogenation of petroleum fractions. The columns were packed with commercial cylindrical catalyst pellets of -in. diameter and length. The liquid holdup was from 40 to 50% of total bed volume for nominal liquid velocities from 8 to 200 ft/hr in the model reactors, from 26 to 32% of volume for nominal liquid velocities from 6 to 10.5 ft/hr in the pilot unit, and from 20 to 27 % for nominal liquid velocities from 27.9 to 68.6 ft/hr in the industrial unit. In that work, a few sets of results of residence-time distribution experiments are reported in graphical form, as tracer-response curves. 

If kiAi is known with good accuracy, it may be possible to back out the intrinsic kinetics using the methods of Section 7.1. Knowing the intrinsic kinetics may enable a scaleup where kiAj(af — ai) is dilferent in the large and small units. However, it is better to adjust conditions in the pilot reactor so that they are identical to those expected in the larger reactor. Good pilot plants have this versatility. The new conditions may give suboptimal performance in the pilot unit but achievable performance in the full-scale reactor. 

Several pilot plants have been built to test periodic flow direction reversal. Pilot-scale reactors with bed diameters from 1.6 to 2.8 m were operated with flow reversal for several years. The units, described by Bunimovich et al. (1984,1990) and Matros and Bunimovich (1996), handled 600 to 3000 m3/h and operated with cycle periods of 15 to 20 min. Table VIII shows the performance of these plants for different feeds and potassium oxide promoted vanadia catalysts. The SVD catalyst was granular the IK-1-4 was in the form of 5 (i.d.) x 10-mm cylinders, while the SYS catalyst was... 

Scale-up of MTO has proceeded through bench-scale and 4 BPD pilot units and has been tested in a 100 BPD reactor. 

This paper describes the initial scale-up of the MTO process from a micro-fluid-bed reactor (1-10 grams of catalyst) to a large pilot unit (10-25 kilograms of catalyst). 

Based on actual methane use in the pilot-scale reactor projected methane costs for a large unit were 0.33 per 1000 gal of water treated. This cost could be reduced by modifications to the system. Calculated theoretical minimum methane costs were 0.05 per 1000 gal (D10498D). 

In the present work, the objective was to develop and implement a control algorithm for addition of hydrolysate, based on the total gas flow from a pilot development unit (PDU)-scale reactor. The control algorithm was tested in fed-batch fermentations of dilute-acid hydrolysate made with two different yeast strains. 

Using the data in Example 13-2, determine the aspect ratio for the same cooling time (0.85 hr) as the larger unit, with the working volume twice that of the pilot plant scale of a segmented batch reactor. 

The other industrial kiln reactor that is examined in this chapter is the Conrad recycling process. This process uses an auger kiln reactor to transform plastic and/or tyres in the absence of oxygen into liquid petroleum, solid carbonaceous material and noncondensable gases at high temperatures. Conrad currently has two facilities in operation. They have a 200 Ib/h pilot unit and a 2000 Ib/h commercial scale unit at Chehalis research facility (Figure 19.4 shows the process diagram) [9]. 

Thus, the ACR scale criteria has been verified under the extreme condition of directly scaling from a pilot to a full-scale reactor. This allows the smaller scale ACR demonstration unit to be designed with confidence. As required, the data from the demonstration unit will be used to further refine the scaling techniques before the commercial ACR process design is finalized. 

ABSTRACT A novel reactor configuration has been developed in our laboratory which addresses the heat transfer limitations usually encountered in vacuum pyrolysis technology. In order to scale-up this reactor to an industrial scale, a systematic study on the heat transfer, the chemical reactions and the movement of the bed of particles inside the reactor has been carried out over the last ten years. Two different configurations of moving and stirred bed pilot units have been used to scale-up a continuous feed vacuum pyrolysis reactor, in accordance with the principle of similarity. A dynamic model for the reactor scale-up was developed, which includes heat transfer, chemical kinetics and particle flow mechanisms. Based on the results of the experimental and theoretical studies, an industrial vacuum pyrolysis reactor, 14.6 m long and 2.2 m in diameter, has been constructed and operated. The operation of the pyrolysis reactor has been successful, with the reactor capacity reaching the predicted feed rate of 3000 kg/h on a biomass feedstock anhydrous basis. 

Its formation can be kept to a minimum by keeping the excess air supplied to combustion units to a minimum value for safe complete combustion [56]. Burner designs that produce a more diffuse flame front (large flame volume) achieve lower peak combustion temperatures, which helps to decrease the formation of nitric oxide. Injection of ammonia into the flue gas while it is still hot can decrease NOx concentrations down to 80-120 ppm, one-third to one-half that of uncontrolled discharges [64]. Measures for NO reduction during operation of fluid catalytic crackers have been evaluated in pilot scale reactors [65]. 

It is noted that the requirement of proper separation of scales represents the main drawback of the volume averaging method. The constitutive equations used generally depend strongly on this assumption which is hardly ever fulfilled performing simulations of laboratory, pilot and industrial scale reactor units. 

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