Start-up phase

Start-up is the transition from completion of construction to full operation and it impacts both construction and operations (Fig. 6). Many times, projects have construction scheduled to be completed simultaneously in all areas. This is neither accurate or the real world. Both construction and start-up personnel must think in terms of a phased completion because construction will not have sufficient people to complete every thing at once and start-up will not have sufficient people, or functionality, to start-up the facility all at once. The sequence of completion needs to be agreed upon early in the construction effort so that construction focuses on completion in the agreed sequence and start-up gains availability to start in a logical sequence. If the last item on the construction schedule is to set the main electrical transformer and connect the plant power, no transition to start-up is possible. There are many more subtle constraints in a construction schedule that can be prevented with proper planning. 

One of the items to be covered in start-up is manpower planning what skills will be required, who will supply them, and what are the quantities Operator manning levels tend to justify themselves, so it is not a good practice to just add more operators for start-up, but rather, to supplement with people who will not stay with the project once it accomplishes full operation. 

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The importance of the downcomer seal is to prevent vapor from the tray from bubbling into the downcomer (see Figure 8-63), whether the trays are bubble cap, valve or sieve types. If a seal weir is not included in the tray design, then operation problems to avoid flooding, weeping and unstable performance, including pressure drop, are increased, particularly during the start-up phase. 

In the dialyzed batch start-up phase and the subsequent continuous operation a substantial increase in viable cell density and monoclonal antibody (MAb) titer was observed compared to a conventional suspension culture. The raw data, profiles of the viable cell density, viability and monoclonal antibody titer during the batch start-up and the continuous operation with a dialysis flow rate of 5 L/d are shown in Figures 17.6 and 17.7. The raw data are also available in tabular form in the corresponding input file for the FORTRAN program on data smoothing for short cut methods provided with the enclosed CD. 

At time t=212 h the continuous feeding was initiated at 5 L/d corresponding to a dilution rate of 0.45 d . Soon after continuous feeding started, a sharp increase in the viability was observed as a result of physically removing dead cells that had accumulated in the bioreactor. The viable cell density also increased as a result of the initiation of direct feeding. At time t 550 h a steady state appeared to have been reached as judged by the stability of the viable cell density and viability for a period of at least 4 days. Linardos et al. (1992) used the steady state measurements to analyze the dialyzed chemostat. Our objective here is to use the techniques developed in Chapter 7 to determine the specific monoclonal antibody production rate in the period 212 to 570 h where an oscillatory behavior of the MAb titer is observed and examine whether it differs from the value computed during the start-up phase. 

The focus on the start-up phase of a hydrogen infrastructure, by taking into account uncertainties of future market development over the step-by-step optimisation (myopic approach) and the influence of single production plants (using integer variables), thus allowing economies of scale to play out. 

Phase I Early start-up phase with very low hydrogen penetration (demonstration phase). A few large-scale first-user centres are situated in European capitals (see also Roads2Hy-Com (2007)). Owing to its case-by-case selection of the technology options, this phase is not considered in the infrastructure analysis. 

Hydrogen corridors are not suitable for the start-up phase of hydrogen use in the energy sector (no small-scale solutions)... 

Sources of cheaper hydrogen for the start-up phase are already available (e.g., as a chemical by-product, mostly fossil-based) and are very often used only thermally... 

Hydrogen also occurs as a by-product of the chemical industry (for instance, chlorine-alkali electrolysis) and is already being used thermally. This represents another (cheap) option (where available), because it can be substituted by natural gas, although investments in purification might be necessary. This option is relevant for supplying hydrogen during the initial start-up phase in areas where user centres are nearby. 

It would not be possible to have such an infrastructure in place in the start-up phase of a wood acetylation industry. Such a process would rely upon there being sufficient quantities of acetylated wood available as a feedstock, and this would require many years of production. Furthermore, the costs involved in setting up such a plant would in all probability make the acetylation process uneconomic at present. Only when the industry matures would it be possible to bear the costs of building the necessary extra processing facilities. 

A comparison of PCA score plots on both acoustic and conventional process data is presented to see if acoustic chemometrics can supply new information to the process operators in the critical start-up phase of... 

June 2007-June 2008 ECHA start-up phase During this period the ECHA will be set up in Helsinki and will start its preparations for the period when the actual registrations will come in. The activities and committees of the ECB will be transferred to the ECHA and ECHA staff will be trained to take up their duties. 

The model of Beck and Bauer (1989) predicts the ethanol productivity, and the ethanol concentrations in the bed and the condensate, assuming equilibrium conditions in an anaerobic gas-solid fluidized bed fermenter using a partial condenser (see Figure 6.6). This model does not predict the build-up of ethanol in the bed nor the increase in the rate of ethanol production at the partial condenser. Rather, it is assumed that this start-up phase is already complete, and that the ethanol concentration in the bed and the rate of ethanol production at the partial... 

The ATR is carried out in the presence of a catalyst, which controls the reaction pathways and thereby determines the relative extents of the oxidation and SR reactions. The SR reaction absorbs part of the heat generated by the oxidation reaction, limiting the maximum temperature in the reactor. The net result is a slightly exothermic process. However, in order to achieve the desired conversion and product selectivity, an appropriate catalyst is essential. The lower temperature provides many benefits such as less thermal integration, less fuel consumed during the start-up phase, wider choice of materials, which reduces the manufacturing costs, and reduced reactor size and cost due to a minor need for insulation [22]. 

Heinzel et al. [77] compared the performance of a natural gas autothermal reformer with that of a steam reformer. The ATR reactor was loaded with a Pt catalyst on a metallic substrate followed by a fixed bed of Pt catalyst. In the start-up phase, the metallic substrate was electrically heated until the catalytic combustion of a stoichiometric methane-air mixture occurred. The reactor temperature was increased by the heat of the combustion reaction and later water was added to limit the temperature rise in the catalyst, while the air flow was reduced to sub-stoichiometric settings. With respect to the steam reformer, the behavior of the ATR reactor was more flexible regarding the start-up time and the load change, thus being more suitable for small-scale stationary applications. 

In the start-up phase, the ignition of a methane-air mixture is induced by a voltaic arc between two spark plugs placed on the surface of the SiC foam (Figure 9.7b). 

The results relevant to the optimized conditions for the start-up phase, as defined for specific experiments, are reported in Figure 9.9 in terms of H2, CO and CO2... 

The reactor start-up was performed by feeding a water-free mixture of methane and air with an O2/CH4 molar ratio of 1.36 and by inducing for few seconds the voltaic arc between the spark plugs. When the mixture is ignited, the temperature on the SiC foam suddenly (1 min) reaches around 1000 °C. Furthermore, due to the heat transfer, the temperature in the catalytic zone reaches in about 2 min the light-off value with full reactants conversion. The whole start-up phase is no longer than 3 min. 

The first step is relevant to the start-up phase, which in this particular case we chose to extend for up to 1 h in order to verify the reactor stability also in these conditions, where water is not present and while there is a higher oxygen concentration in the feed gas with respect to the ATR conditions. By lowering the 02 CH4 ratio, the H2 concentration at the reactor outlet increases, approaching the value expected by thermodynamic evaluation and CH4 conversion is still complete. A further decrease in the 02 CH4 feed ratio to values lower than 1.16 corresponds to an abrupt decrease in temperature in the lower section and a simultaneous temperature increase in the catalytic reforming section. 

Minimize changes during the EPC, turnover, and start-up phases. Reduce project schedule and capital cost. 

Consolidated Edison Company of New York installed a simitar -I K MW unir in New York. City, but after a lew years, the project was closed down. The demonstration did mu see the production of power as planned because the acid electrolyte of the fuel celts became depleted due to emended program delays. An attempt to replenish the aid was unsuccessful However, must was teamed daring the engineering, licensing, construction ami start-up phases of ihe program. 

The aim of the experiments was to obtain stationary values for SO2 separation. Initially, the hold-up was sprayed with water to obtain stationary temperatures after cooling the particles and to conserve the used calcium hydroxide during the unsteady start-up phase. At the steady-state temperature the injection was suddenly switched to suspension. The SC>2-concentration at the outlet then decreased. The suspension consisted of lime hydrate (DIN 1060-CL90, DIN EN 12518) and water. The suspension injection had to be held constant until the SC>2-concentration was constant. After achieving steady state the injection was stopped, and this caused an increase in SC>2-concentration at the outlet up to the initial value. The same procedure was started after a few minutes in order to obtain a new measuring point at a higher suspension injection rate. 

Heinrich [30] reported that a rapid achievement of steady state depends on complete substitution of the hold-up particles by external seeds when the hold-up and seed particles are of the same size, and very small. Otherwise, the unsteady start-up phase is of much longer duration and the particle size distribution of the product is wider. 

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