Rate production

= Atomic weight or molar mass g/mol) t = Time (s) z = Valence 

Conventional electrowinning cells utilize planar Pb-hd e anodes at cmrent densities in the range of 200 A/rri i 500 A/m [2,14]. On the other hand, advanced electrowinning cells use hydrogen gas diffusion (HGD) anodes at 2 kA/rri i 8 kA/m [15-18]. Normally, the current density and energy efficiency (e ) are less than 100% due to drawbacks mainly caused by ohmic potential drop and oxygen evolution reaction. The energy efficiency can be defined by 

According to CSim s law, the distribution of the solution resistance can be deduced from eq. (7.14) as 

Another important parameter for assessing the performance of an electrowinning cell is the production rate, which is defined by 

In order to analyze an electrowinning cells from economical point of view, the power and the energy consumption needed to operate the cell are, respectively 

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Operation is more flexible for variable production rates or manufacture of a variety of similar products in the same equipment. 

There can be an element of maintenance costs that is fixed and an element which is variable. Fixed maintenance costs cover routine maintenance such as regular maintenance on safety valves which must be carried out irrespective of the rate of production. There also can be an element of maintenance costs which is variable. This arises from the fact that certain items of equipment can need more maintenance as the production rate increases. Also, royalties which cover the cost of purchasing another company s process technology may have different bases. Royalties may be a variable cost, since they can sometimes be paid in proportion to the rate of production. Alternatively, the royalty might be a single-sum payment at the beginning of the project. In this case, the single-sum payment will become part of the project s capital investment. As such, it will be included in the annual capital repayment, and this becomes part of the fixed cost. 

Initially new wells may still be brought on stream but the older wells start to decline. A constant production rate is maintained. This period is typically 2 to 5 years for an oil field, but longer for a gas field. 

This is why an offtake limit on the plateau production rate is often imposed, to limit the amount of by-passed oil, and increase the macroscopic sweep efficiency. 

The plateau production rates for cases A and B differ significantly from that in case C, which has a lower but longer plateau. The advantage of profile C is that it requires smaller facilities and probably less wells to produce the same UR. This advantage in reduced costs must be considered using economic criteria against the delayed production of oil (which is bad for the cashflow). One additional advantage of profile C is that the... 

In gas wells, the inflow equation which determines the production rate of gas (Q) can be expressed as... 

To reduce this tendency the well should be produced at low rate, and the perforations should be as far away from the OWC as possible. Once the unwanted fluid breaks through to a well, the well may be recompleted by changing the position of the perforations during a workover, or the production rate may be reduced. 

The PIF estimate is only a qualitative check on the potential benefit of a horizontal well. There is actually a diminishing return of production rate on the length of well drilled, due to increasing friction pressure drops with increasing well length, shown schematically in Figure 9.6. 

Figure 9.6 Production rate vs horizontal well length...

Routine production tests are performed, approximately once per month on each producing well, by diverting the production through the test separator on surface to measure the liquid flowrate, water cut, and gas production rate. The wellhead pressure (also called the flowing tubing head pressure, FTHP) is recorded at the time of the production test, and a plot of production rate against FTHP is made. The FTHP is also recorded continuously and used to estimate the well s production rate on a daily basis by reference to the FTHP vs production rate plot for the well. 

An example of an application of CAO is its use in optimising the distribution of gas in a gas lift system (Fig. 11.3). Each well will have a particular optimum gas-liquid ratio (GLR), which would maximise the oil production from that well. A CAO system may be used to determine the optimum distribution of a fixed amount of compressed gas between the gas lifted wells, with the objective of maximising the overall oil production from the field. Measurement of the production rate of each well and its producing GOR (using the test separator) provides a CAO system with the information to calculate the optimum gas lift gas required by each well, and then distributes the available gas lift gas (a limited resource) between the producing wells. 

Fixed opex is proportional to the capital cost of the items to be operated and is therefore based on a percentage of the cumulative capex. Variable opex is proportional to the throughput and is therefore related to the production rate (oil or gross liquids). Hence,... 

Production levels will be influenced by external factors such as agreed production targets, market demand, the level of market demand for a particular product, agreements with contractors, and legislation. These factors are managed by planning of production rates and management of the production operation. 

Introduction and Commercial Application The production decline period for a field is usually defined as starting once the field production rate falls from its plateau rate. Individual well rates may however drop long before field output falls. This section introduces some of the options that may be available, initially to arrest production decline, and subsequently to manage decline in the most cost effective manner. 

To detemiine k E) from equation (A3.12.9) it is assumed that transition states with positivefomi products. Notmg that / f = p dqf/dt, where p is the reduced mass of the separating fragments, all transition states that lie within and + dq with positive will cross the transition state toward products in the time interval dt = pj dqf p. Inserting this expression into equation (A3.12.9), one finds that the reactant-to-product rate (i.e. flux) through the transition state for momenPim p is... 

Ca.ta.lysts, Catalyst performance is the most important factor in the economics of an oxidation process. It is measured by activity (conversion of reactant), selectivity (conversion of reactant to desked product), rate of production (production of desked product per unit of reactor volume per unit of time), and catalyst life (effective time on-stream before significant loss of activity or selectivity). 

Because RPSA is appHed to gain maximum product rate from minimum adsorbent, single beds are the norm. In such cycles where the steps take only a few seconds, flows to and from the bed are discontinuous. Therefore, surge vessels are usuaHy used on feed and product streams to provide unintermpted flow. Some RPSA cycles incorporate delay steps unique to these processes. During these steps, the adsorbent bed is completely isolated and any pressure gradient is aHowed to dissipate (68). The UOP Polybed PSA system uses five to ten beds to maximize the recovery of the less selectively adsorbed component and to extend the process to larger capacities (69). 

Prices of spandex fibers are highly dependent on thread size selling price generally increases as fiber tex decreases. Factors that contribute to the relatively high cost of spandex fibers include (/) the relatively high cost of raw materials, (2) the small size of the spandex market compared to that of hard fibers which limits scale and thus efficiency of production units, and (J) the technical problems associated with stretch fibers that limit productivity rates and conversion efficiencies. 

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