Losses


The secondary reactions are series with respect to the chloromethane but parallel with respect to chlorine. A very large excess of methane (mole ratio of methane to chlorine on the order of 10 1) is used to suppress selectivity losses. The excess of methane has two effects. First, because it is only involved in the primary reaction, it encourages the primary reaction. Second, by diluting the product, chloromethane, it discourages the secondary reactions, which prefer a high concentration of chloromethane.  [c.40]

When separating azeotropic mixtures, if possible, changes in the azeotropic composition with pressure should be exploited rather than using an extraneous mass-separating agent. When using an extraneous mass-separating agent, there are inevitably losses from the process. Even if these losses are not significant in terms of the cost of the material, they create environmental problems somewhere later in the design. As discussed in detail in Chap. 10, the best way to solve effluent problems is to deal with them at the source. The best way to solve the effluent problems caused by loss of the extraneous mass-separating agent is to eliminate it from the design. However, clearly in many instances practical difficulties and excessive cost might force its use. Occasionally, a component that already exists in the process can be used as the entrainer or solvent, thus avoiding the introduction of extraneous materials for azeotropic and extractive distillation.  [c.83]

Also, instead of using two separators, a purge can be used (see Fig. 4.2c). Using a purge saves the cost of a separator but incurs raw materials losses and possibly waste treatment and disposal costs.  [c.96]

The fourth option, shown in Fig. 4.4[c.100]

Also, although there are no selectivity data for the reaction, the selectivity losses would be expected to increase with increasing conversion. Complete conversion would tend to produce unacceptable selectivity losses. Finally, the reactor volume required to give a complete conversion would be extremely large.  [c.104]

An arrangement is to be chosen to inhibit the side reaction, i.e., give low selectivity losses. The side reaction is suppressed by starving the reactor of either monochlorodecane or chlorine. Since the reactor is designed to produce monochlorodecane, the former option is not practical. However, it is practical to use an excess of decane.  [c.104]

In this case, the stoichiometric factor is 1. This is a measure of the MCD obtained from the DEC consumed. To assess the selectivity losses, the MCD  [c.104]

Rather than send the vapor to one of the separation units described above, a purge can be used. This removes the need for a separator but incurs raw material losses. Not only can these material losses be expensive, but they also can create environmental problems. However, another option is to use a combination of a purge with a separator.  [c.109]

Losses in the reactor due to byproduct formation or unconverted feed material if recycling is not possible.  [c.122]

Losses from the separation and recycle system.  [c.122]

In this case, because there are no raw materials losses in the separation and recycle system, the only yield loss is in the reactor, and the process yield equals the reactor selectivity.  [c.125]

In addition, one other feature of the prefractionator arrangement is important in reducing mixing effects. Losses occur in distillation operations due to mismatches between the composition of the column feed and the composition on the feed tray. Because the prefractionator distributes component B top and bottom, this allows greater freedom to match the feed composition with one of the trays in the column to reduce mixing losses at the feed tray.  [c.151]

The elimination of mixing losses in a prefractionator arrangement means that it is inherently more efficient than an arrangement using simple columns.  [c.151]

Both the side-rectifier and side-stripper arrangements have been shown to reduce the energy consumption compared with simple two-column arrangements. This results from reduced mixing losses in the first (main) column. As with the first column of the simple sequence, a peak in composition occurs with the middle product. Now, however, advantage of the peak is taken by transferring material to the side-rectifier or side-stripper.  [c.152]

As with the case of byproduct losses, another cost needs to be added to the tradeoffs when there is a purge. This is a raw materials efficiency cost due to purge losses. If the PRODUCT formation is constant, this cost can be defined to be  [c.246]

Cost of purge losses = cost of FEED lost to purge — value of purge  [c.246]

Cost of purge losses = cost of FEED lost to purge + cost of disposal of purge  [c.246]

Again, as with the byproduct case, those raw materials costs which are in principle avoidable (i.e., the purge losses) are distinguished from those which are inevitable (i.e., the stoichiometric requirements for FEED entering the process which converts to the desired PRODUCT). Consider the tradeoffs for the reaction in Eq. (8.1), but now with IMPURITY entering with the FEED.  [c.246]

Reducing waste from multiple reactions producing waste byproducts. In addition to the losses described above for single reactions, multiple reaction systems lead to further waste through the formation of waste byproducts in secondary reactions. Let us briefly review from Chap. 2 what can be done to minimize byproduct formation.  [c.278]

Let us now turn our attention to losses from the separation and recycle system.  [c.280]

Reduce losses from fugitive emissions and tank breathing as discussed under safety in Chap. 9.  [c.290]

Assessing only the local efiects of combined heat and power is misleading. Combined heat and power generation increases the local utility emissions because, besides the fuel burnt to supply the heating demand, additional fuel must be burnt to generate the power. It is only when the emissions are viewed on a global basis, and the emissions from central power generation included, that the true picture is obtained. Once these are included, on-site combined heat and power generation can make major reductions in global utility waste. The reason for this is that even the most modem central power stations have a poor efficiency of power generation compared with a combined heat and power generation system. Once the other inefficiencies associated with centralized power generation are taken into account, such as distribution losses, the gap between the efficiency of combined heat and power systems and centralized power generation widens.  [c.292]

Waste from cooling systems. Cooling water systems also give rise to wastewater generation. Most cooling water systems recirculate water rather than using once through arrangements. Water is lost from recirculating systems in the cooling tower mainly through evaporation but also, to a much smaller extent, through drift (wind carrying away water droplets). This loss is made up by raw water which contains solids. The evaporative losses from the cooling tower cause these solids to build up. The buildup of solids is prevented by a purge of water from the system, i.e., cooling tower blowdown. Cooling tower blowdown is the source of the largest volume of wastewater on many sites.  [c.294]

Increasing process yields through feed purification to reduce losses in the reactor and separation and recycle system.  [c.297]

Reducing losses from fugitive emissions and tank breathing.  [c.297]

Adsorption. Some organics are not removed in biological systems operating under normal conditions. Removal of residual organics can be achieved by adsorption. Both activated carbon and synthetic resins are used. As described earlier under pretreatment methods, regeneration of the activated carbon in a furnace can cause carbon losses of perhaps 5 to 10 percent.  [c.319]

Steam costs vary with the price of fuel. If steam is only generated at low pressure and not used for power generation in steam turbines, then the cost can be estimated from local fuel costs assuming a boiler efficiency of around 75 percent (but can be significantly higher) and distribution losses of perhaps another 10 percent, giving an overall efficiency of around 65 percent.  [c.408]

In Fig. A.l, high-pressure steam is generated and fed to the high-pressure mains. The medium- and low-pressure mains are fed by expansion through steam turbines to generate power. Figure A.l shows three mains with typical mains pressures, but these vary in both number and pressure from site to site. Figure A. 1 also shows the possibility of using a condensing turbine, which is used when there is a desire to generate power but the exhaust steam from a backpressure turbine is not needed. Letdown stations are used to control the mains pressures. Because the letdown from high-pressure to lower-pressure mains creates steam with a large superheat, boiler feedwater is injected directly to reduce the superheat. As discussed in Example A.3.1, although steam for process heating is preferred saturated, if it is fed through the mains saturated, this leads to excessive condensation in the mains due to heat losses, which is undesirable. Hence steam is fed to the mains with some superheat. Another feature shown in Fig. A.l is that when water (blowdown or condensate) is reduced in pressure, flash steam is recovered. Although as much condensate as practicable and economical should be returned to the deaerator, levels of condensate return tend to be on the order of 50 percent but can be significantly higher.  [c.413]

Gasoline Evaporative Losses  [c.246]

Hydrocarbon losses through evaporation are inevitable in spite of all the preventive steps that are or will be employed. Vapor recovery systems are obligatory in all fuel storage operations and service station systems ( Stage 1 ). These measures will soon extend to filling vehicle fuel tanks ( Stage 2"). Furthermore, new gasoline automobiles throughout Europe will be equipped with fuel tank vapor traps beginning the 1 January 1993. They are activated carbon canisters that trap and store the volatile hydrocarbons when the vehicle is stationary. When the vehicle is moving, the canisters are swept with air and the vapors are recovered as fuel. However this technique is not completely effective and needs to be complemented by very strict control of the fuel s vapor pressure a study conducted in the United States shows that for vehicles equipped with canisters, a reduction of 1 psi (69 mbar) in the vapor pressure causes a 46% reduction in evaporation for stationary cold vehicles and a 9% reduction for vehicles still stationary but after a period of warm operation.  [c.246]

Among the compounds susceptible to evaporation, particular attention is focused on benzene. In the two conditions indicated above, for equal benzene contents in the fuel (1.5% volume), the benzene evaporative losses are reduced by 21% and 11%, respectively, when the vapor pressure decreases by 1 psi, that is, 69 mbar.  [c.246]

There always is a relation between fuel composition and that of hydrocarbon emissions to the atmosphere, whether it concerns hydrocarbon emissions from evaporative losses from the fuel system, or from exhaust gases. This is the reason that environmental protection regulations include monitoring the composition of motor and heating fuels. We will describe here the regulations already in existence and the work currently underway in this area with its possible effects on refining.  [c.258]

Gasolines said to be reformulated are designed with all aspects of environmental protection being considered reducing evaporative losses and conventional exhaust system pollutants, extremely low emissions of toxic substances, the lowest reactivity regarding ozone formation. The general action paths are known reduction of volatility, lowering the levels of aromatics, olefins, sulfur, reducing the distillation end point, addition of oxygenates. Table 5.27 gives an example of a reformulated gasoline s characteristics suggested in 1992 by the Arco Company in the United States. Claims for the pollution improvements are also noted. This is an extreme example of that which would be expected as a result of drastic modification of motor fuel. However, in the United States, local pollution problems observed in a number of urban population centers have already launched safeguarding measures applicable to fuel compositions. These include  [c.264]

Distillation (NF M 07-002) (vol % including losses) between 10% and 47% at 70°C between 40% and 70% at 100°C a 85% at 180 °C a 9% at 210°C  [c.299]

Difference between 5% - point 90% (including losses) End point Residue >60°C <215°C s 2% vol  [c.299]

Distillation (NF M 07-002/1SO 3405) in vol % (including losses) < 65% at 250°C 2 85% at 350°C 2 95% at 370°C  [c.302]

Distiliation (NF M 07-002) (in vol % including losses)  [c.304]

The output from the turbine might be superheated or partially condensed, as is the case in Fig. 6.32. If the exhaust steam is to be used for process heating, ideally it should be close to saturated conditions. If the exhaust steam is significantly superheated, it can be desuperheated by direct injection of boiler feedwater, which vaporizes and cools the steam. However, if saturated steam is fed to a steam main, with significant potential for heat losses from the main, then it is desirable to retain some superheat rather than desuperheat the steam to saturated conditions. If saturated steam is fed to the main, then heat losses will cause excessive condensation in the main, which is not desirable. On the other hand, if the exhaust steam from the turbine is partially condensed, the condensate is separated and the steam used for heating.  [c.195]

The process requires (Qup + Qlp) to satisfy its enthalpy imbalance above the pinch. If there were no losses from the boiler, then fuel W would be converted to shaftwork W at 100 percent efficiency. However, the boiler losses Qloss reduce this to below 100 percent conversion. In practice, in addition to the boiler losses, there also can be significant losses from the steam distribution system. Figure 6.336 shows how the grand composite curve can be used to size steam turbine cycles.  [c.196]

As with the steam turbine, if there was no stack loss to the atmosphere (i.e., if Qloss was zero), then W heat would he turned into W shaftwork. The stack losses in Fig. 6.34 reduce the efficiency of conversion of heat to work. The overall efficiency of conversion of heat to power depends on the turbine exhaust profile, the pinch temperature, and the shape of the process grand composite.  [c.197]

From steam tables, the outlet temperature is 251°C, which is superheated by 67°C. Although steam for process heating is preferred at saturated conditions, it is not desirable in this case to desuperheat by boiler feedwater injection to bring to saturated conditions. If saturated steam is fed to the main, then the heat losses from the main will cause a large amount of condensation in the main, which is undesirable. Hence it is better to feed steam to the main with some superheat to avoid condensation in the main.  [c.410]

To these technological constraints are added an increasing preoccupation with limiting the evaporation losses that are an important source of atmospheric pollution (Me Arragher et al., 1990).  [c.190]


See pages that mention the term Losses : [c.124]    [c.153]    [c.247]    [c.409]    [c.409]    [c.19]    [c.300]    [c.303]    [c.305]   
Gas turbine engineering handbook (2002) -- [ c.0 ]

Power supply cookbook (2001) -- [ c.0 ]