Reactor conversion rate

Description Ammonia and carbon dioxide react at 155 bar to synthesize urea and carbamate. The reactor conversion rate is very high under the N/C ratio of 3.7 with a temperature of 182-185°C. Unconverted materials in synthesis solution are efficiently separated by C02 stripping. The milder operating condition and using two-phase stainless steel prevent corrosion problems. Gas from the stripper is condensed in vertical submerged carbamate condenser. Using an HP Ejector for internal synthesis recycle, major synthesis equipment is located on the ground level. 

The first reaction is exothermic and goes almost to completion, while the second, endothermic, reaction converts less than 70% of feedstocks to urea. Consequently, the once-through process of urea synthesis had to be combined with production of other nitrogen compounds. Modern syntheses use a more expensive total recycle process in which all the unreacted CO2 and NH3 is separated from the effluent solution and returned to the reactor. Conversion rates range between 65 and 67% for each pass, and the overall reaction yield is on the order of 99%. Three commercial processes—Dutch Stamicarbon, Italian Snamprogetti, and Japanese Toyo—dominate today s world market for large (up to 2,000 t/day) urea plants using the total recycle process. ... 

Increasing the pressure of irreversible vapor-phase reactions increases the rate of reaction and hence decreases reactor volume both by decreasing the residence time required for a given reactor conversion and increasing the vapor density. In general, pressure has little effect on the rate of liquid-phase reactions. 

An initial guess for the reactor conversion is very difficult to make. A high conversion increases the concentration of monoethanolamine and increases the rates of the secondary reactions. As we shall see later, a low conversion has the effect of decreasing the reactor capital cost but increasing the capital cost of many other items of equipment in the flowsheet. Thus an initial value of 50 percent conversion is probably as good as a guess as can be made at this stage. 

Figure 4.9 shows a plot of Eq. (4.12). As the purge fraction a is increased, the flow rate of purge increases, but the concentration of methane in the purge and recycle decreases. This variation (along with reactor conversion) is an important degree of freedom in the optimization of reaction and separation systems, as we shall see later. 

Table 12.4. Conversion rates for near full scale reactor measured on 1.8 1 test engine. Conversion rates in % of raw material...

Figure 10. Monomer conversion rates as a function of emulsion Reynolds number for straight and helical tubular reactors...

The utihty stream gets started at operating temperature and flow rate. In the following experiments, the utihty stream is heated so as to initiate the reaction. The main and secondary process tines are fed with water at room temperature and with the same flow rate as one of the experiments. Once steady state is reached, operating parameters are recorded. Process tines are then fed with the reactants, hydrogen peroxide and sodium thiosulfate. At steady state, operating parameters are recorded, and a sample of a known mass of reactor products is introduced in the Dewar vessel. Temperature in the Dewar vessel is recorded until equilibrium is reached, that is, until the reaction ends. This calorimetric method is aimed at calculating the conversion rate at the product outlet and thus the conversion rate in the reactor. The latter is also determined by thermal balances between process inlet and outlet of the reactor. Finally, the reactor is rinsed with water. This procedure is repeated for each experiment... 

Two methods have been used to calculate the conversion rate in the reactor. They are based on thermal balances first between inlet and outlet of process and utility streams in the reactor and then between sampling and thermal equilibrium in the Dewar vessel. The former leads to the conversion rate obtained in the reactor, x and the latter gives the conversion rate downstream from the reactor outlet, 1 - X-... 

This approach consists in measuring the adiabatic temperature increase of a sample taken at the outlet of the reactor. Samphng is made in an adiabatic vessel (Dewar vessel) and temperature is recorded until the reaction ends, that is, until an equilibrium temperature is reached. The conversion rate is thus written as... 

The CFB catalytic cracking reactor plays an important role in the petroleum industry because of its better gas-solids contact and narrow residence time distribution, but its non-uniform radial flow structure and the extensive backmixing of gas and solids lead to a lower conversion rate and poorer selectivity to desired intermediate products [14]. 

GP 1] [R 10] Conversion rates over platinum catalyst were determined in a chip-based reactor [56]. In the temperature range from 180 to 310 °C rates from 0 to... 

OS 33] ]R 16h] [P 25] For the nitration of a single-ring aromatic in a capillary-flow micro reactor, experiments were performed at two temperature levels, 60 and 120 °C [94]. Owing to the assumed increase in conversion rate with higher temperature, attempts were made to compensate for this by decreasing the capillary length at otherwise constant dimensions. For the 60 °C experiment, a very low... 

GL 23] [R 12] [P 16] Conversions near 70% were determined for a mini trickle-bed reactor (flow rate 20 mg min ) [36]. The corresponding reaction rate was 10 times larger than in typical batch operation on a laboratory-scale, which is restricted to milder conditions. 

Sodium hydroxide was introduced into a reactor containing 90 kg of ethylene oxide. The reactor detonated eight hours later. A study was carried out to try to understand what caused the accident. It showed that in similar conditions the temperature of the medium reaches 100°C when 13% of oxide is polymerised, then 160°C at 28% of conversion. At this stage, it takes sixteen seconds for the medium to reach a conversion rate of 100% and a temperature that reaches 700°C. 

The reactor conversion is 20% and selectivity 80%. Find the heat removal rate from a plant producing 100 tons per day of ethylene oxide (see Table 6.16). Excess oxygen of 10%... 

In the design of an industrial scale reactor for a new process, or an old one that employs a new catalyst, it is common practice to carry out both bench and pilot plant studies before finalizing the design of the commercial scale reactor. The bench scale studies yield the best information about the intrinsic chemical kinetics and the associated rate expression. However, when taken alone, they force the chemical engineer to rely on standard empirical correlations and prediction methods in order to determine the possible influence of heat and mass transfer processes on the rates that will be observed in industrial scale equipment. The pilot scale studies can provide a test of the applicability of the correlations and an indication of potential limitations that physical processes may place on conversion rates. These pilot plant studies can provide extremely useful information on the temperature distribution in the reactor and on contacting patterns when... 

This equation is plotted in Fig. 11, showing that for relatively dense support particles, biofilm growth can reduce the settling velocity if the biofilm density is less than that of the biofilm-free particle. As such bioparticles gain biomass, they will rise to the top of the bed and may even elutriate from the reactor (Sreekrishnan et al., 1991 Myska and Svec, 1994), reducing achievable conversion rates. This situation could be resolved by using lower density particles, such as expanded polystyrene or... 

Figure 8.7 demonstrates that the H2-activated catalysts that were calcined using nitric oxide resulted in higher initial CO conversion rates on a per gram of catalyst basis in a CSTR reactor at 220°C and 280 psig, and using a Fl2/CO ratio of 2.5. 

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