Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Creating

Moderate errors in the total pressure calculations occur for the systems chloroform-ethanol-n-heptane and chloroform-acetone-methanol. Here strong hydrogen bonding between chloroform and alcohol creates unusual deviations from ideality for both alcohol-chloroform systems, the activity coefficients show... [Pg.53]

Once the flowsheet structure has been defined, a simulation of the process can be carried out. A simulation is a mathematical model of the process which attempts to predict how the process would behave if it was constructed (see Fig. 1.1b). Having created a model of the process, we assume the flow rates, compositions, temperatures, and pressures of the feeds. The simulation model then predicts the flow rates, compositions, temperatures, and pressures of the products. It also allows the individual items of equipment in the process to be sized and predicts how much raw material is being used, how much energy is being consumed, etc. The performance of the design can then be evaluated. [Pg.1]

Since process design starts with the reactor, the first decisions are those which lead to the choice of reactor. These decisions are among the most important in the whole design. Good reactor performance is of paramount importance in determining the economic viability of the overall design and fundamentally important to the environmental impact of the process. In addition to the desired products, reactors produce unwanted byproducts. These unwanted byproducts create environmental problems. As we shall discuss later in Chap. 10, the best solution to environmental problems is not elaborate treatment methods but not to produce waste in the first place. [Pg.15]

Given that the objective is to manufacture a certain product, there are often a number of alternative reaction paths to that product. Reaction paths which use the cheapest raw materials and produce the smallest quantities of byproducts are to be preferred. Reaction paths which produce significant quantities of unwanted byproducts should especially be avoided, since they create significant environmental problems. [Pg.16]

Unwanted byproducts usually cannot be converted back to useful products or raw materials. The reaction to unwanted byproducts creates both raw materials costs due to the raw materials which are wasted in their formation and environmental costs for their disposal. Thus maximum selectivity is wanted for the chosen reactor conversion. The objectives at this stage can be summarized as follows ... [Pg.25]

The liquid used for the direct heat transfer should be chosen such that it can be separated easily from the reactor product and so recycled with the minimum expense. Use of extraneous materials, i.e., materials that do not already exist in the process, should be avoided because it is often difficult to separate and recycle them with high efficiency. Extraneous material not recycled becomes an effluent problem. As we shall discuss later, the best way to deal with effluent problems is not to create them in the first place. [Pg.43]

In general, heterogeneous catalysts are preferred to homogeneous catalysts because the separation and recycling of homogeneous catalysts often can be very difficult. Loss of homogeneous catalyst not only creates a direct expense through loss of material but also creates an environmental problem. [Pg.46]

The rate at which the catalyst is lost or degrades has a major influence on the design. If degradation is rapid, the catalyst needs to be regenerated or replaced on a continuous basis. In addition to the cost implications, there are also environmental implications, since the lost or degraded catalyst represents waste. While it is often possible to recover useful materials from degraded catalyst and to recycle those materials in the manufacture of new catalyst, this still inevitably creates waste, since the recovery of material can never be complete. [Pg.49]

Raw materials efficiency. In choosing the reactor, the overriding consideration is usually raw materials efficiency (bearing in mind materials of construction, safety, etc.). Raw material costs are usually the most important costs in the whole process. Also, any inefficiency in raw materials use is likely to create waste streams that become an environmental problem. The reactor creates inefficiency in the use of raw materials in the following ways ... [Pg.60]

The simplest type of centrifugal device is the cyclone separator (Fig. 3.4), which consists of a vertical cylinder with a conical bottom. The centrifugal force is generated by the fluid motion. The mixture enters in a tangential inlet near the top, and the rotating motion so created develops centrifugal force which throws the particles radially toward the wall. [Pg.71]

Pressure. High pressure gives greater solubility of solute in the liquid. However, high pressure tends to be expensive to create, since this can require a gas compressor. Thus there is an optimal pressure. [Pg.84]

Because we require a pure product, a separator is needed. The unreacted FEED is usually too valuable to be disposed of and is therefore recycled to the reactor inlet via a pump or compressor (see Fig. 4.16). In addition, disposal of unreacted FEED rather than recycling creates an environmental problem. [Pg.96]

Figure 4.4 Introduction of an impurity with the feed creates further options for recycle structures. (From Smith and Linnhoff, Trans. IChemE, ChERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers.)... Figure 4.4 Introduction of an impurity with the feed creates further options for recycle structures. (From Smith and Linnhoff, Trans. IChemE, ChERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers.)...
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. [Pg.109]

Raw materials costs dominate the operating costs of most processes (see App. A). Also, if raw materials are not used efficiently, this creates waste, which then becomes an environmental problem. It is therefore important to have a measure of the efficiency of raw materials use. The process yield is defined as... [Pg.122]

The problem with relying on end-of-pipe treatment is that once waste has been created, it cannot be destroyed. The waste can be... [Pg.273]

Reactors. Waste is created in reactors through the formation of waste byproducts, etc. [Pg.274]

Eliminate extraneous materials for separation. The third option is to eliminate extraneous materials added to the process to carry out separation. The most obvious example would be addition of a solvent, either organic or aqueous. Also, acids or alkalis are sometimes used to precipitate other materials from solution. If these extraneous materials used for separation can be recycled with a high efficiency, there is not a major problem. Sometimes, however, they cannot. If this is the case, then waste is created by discharge of that material. To reduce this waste, alternative methods of separation are needed, such as use of evaporation instead of precipitation. [Pg.284]

In early designs, the reaction heat typically was removed by cooling water. Crude dichloroethane was withdrawn from the reactor as a liquid, acid-washed to remove ferric chloride, then neutralized with dilute caustic, and purified by distillation. The material used for separation of the ferric chloride can be recycled up to a point, but a purge must be done. This creates waste streams contaminated with chlorinated hydrocarbons which must be treated prior to disposal. [Pg.285]

The problem with the fiowsheet shown in Fig. 10.5 is that the ferric chloride catalyst is carried from the reactor with the product. This is separated by washing. If a reactor design can be found that prevents the ferric chloride leaving the reactor, the effluent problems created by the washing and neutralization are avoided. Because the ferric chloride is nonvolatile, one way to do this would be to allow the heat of reaction to raise the reaction mixture to the boiling point and remove the product as a vapor, leaving the ferric chloride in the reactor. Unfortunately, if the reaction mixture is allowed to boil, there are two problems ... [Pg.285]

Life-cycle analysis, in principle, allows an objective and complete view of the impact of processes and products on the environment. For a manufacturer, life-cycle analysis requires an acceptance of responsibility for the impact of manufacturing in total. This means not just the manufacturers operations and the disposal of waste created by those operations but also those of raw materials suppliers and product users. [Pg.296]

To the process designer, life-cycle analysis is useful because focusing exclusively on waste minimization at some point in the life cycle sometimes creates problems elsewhere in the cycle. The designer can often obtain useful insights by changing the boundaries of the system under consideration so that they are wider than those of the process being designed. [Pg.296]

The utility system also creates waste through products of combustion from boilers and furnaces and wastewater from water treatment, boiler blowdown, etc. Utility waste minimization is in general terms a question of ... [Pg.297]

When viewing effluent treatment methods, it is clear that the basic problem of disposing of waste material safety is, in many cases, not so much solved but moved from one place to another. The fundamental problem is that once waste has been created, it cannot be destroyed. The waste can be concentrated or diluted, its physical or chemical form can be changed, but it cannot be destroyed. [Pg.319]

Indirect heat transfer with the reactor. Although indirect heat transfer with the reactor tends to bring about the most complex reactor design options, it is often preferable to the use of a heat carrier. A heat carrier creates complications elsewhere in the flowsheet. A number of options for indirect heat transfer were discussed earlier in Chap. 2. [Pg.326]

The pinch design method developed earlier followed several rules and guidelines to allow design for minimum utility (or maximum energy recovery) in the minimum number of units. Occasionally, it appears not to be possible to create the appropriate matches because one or other of the design criteria cannot be satisfied. [Pg.372]

If there had been more cold streams than hot streams in the design above the pinch, this would not have created a problem, since hot utility can be used above the pinch. [Pg.374]

It is not only the stream number that creates the need to split streams at the pinch. Sometimes the CP inequality criteria [Eqs. (16.1) and (16.2)] CEmnot be met at the pinch without a stream split. Consider the above-pinch part of a problem in Fig. 16.13a. The number of hot streams is less than the number of cold, and hence Eq. (16.3) is satisfied. However, the CP inequality also must be satisfied, i.e., Eq. (16.1). Neither of the two cold streams has a large enough CP. The hot stream can be made smaller by splitting it into two parallel branches (Fig. 16.136). [Pg.376]

Clearly, in designs different from those in Figs. 16.13 and 16.14 when streams are split to satisfy the CP inequality, this might create a problem with the number of streams at the pinch such that Eqs. (16.3) and (16.4) are no longer satisfied. This would then require further stream splits to satisfy the stream number criterion. Figure 16.15 presents algorithms for the overall approach. ... [Pg.377]

The design method used so far, the pinch design method, creates an... [Pg.389]

An alternative approach is to create a reducible structure that deliberately includes redundant features and then subject this to optimization. Redundant features are then removed by the optimization. [Pg.394]

Figure 16.26 shows a pair of composite curves divided into enthalpy intervals with a possible superstructure shown for one of the intervals. The structure is created by splitting each hot stream... [Pg.394]


See other pages where Creating is mentioned: [Pg.9]    [Pg.13]    [Pg.13]    [Pg.67]    [Pg.71]    [Pg.83]    [Pg.103]    [Pg.257]    [Pg.275]    [Pg.283]    [Pg.291]    [Pg.294]    [Pg.295]    [Pg.337]    [Pg.385]    [Pg.387]    [Pg.395]   
See also in sourсe #XX -- [ Pg.181 ]

See also in sourсe #XX -- [ Pg.15 ]




SEARCH



Absorbance matrix creating

Action plan, creating

Airflow Created by Exhaust Performance

An Overall Process Description to Create or Improve a Management of Change System

Assembly models Creating structure

Bacteria created biofilms

Basic Functions for Creating Graphs

Bond-creating reconstructions

Bringing acids and bases together to create amides

CREATING NMR SIGNALS

Change control systems creating

Charge distribution creating

Chemical groups creating specific

Chemistry Creates its Own Subject

Conditions to Create an LFER

Correspondence graph , creating

Create

Create

Create Concepts

Create Supersaturation

Create System Element Alternatives

Create access to site and development of lay-down areas

Create an Optimization Culture with Measurable Results

Create first, criticize later

Create function

Create language

Create netlist

Create new model

Create table

Create type

Create wire load

Created Artifacts

Created entropy

Created mesoporosity

Creating Assembly Models

Creating Basis Sets from Scratch

Creating Differentiation

Creating Dislocations

Creating Electrons

Creating Excited States

Creating Feature Trees from Molecules

Creating Flexibility in the Supply Chain

Creating Formulas In Excel

Creating Fragrances for the Future

Creating INDEX

Creating Identification Numbers

Creating Inclusion for Oneself Knowing, Accepting, and Expressing Ones Whole Self at Work

Creating Infrastructure Facilities

Creating Life Using the Cancer Game

Creating Thermal Electrons

Creating User Dialogues

Creating Your Own Safety Knowledge Management System Some Suggestions

Creating a Demand Management Function

Creating a Library of Diverse Solutions

Creating a Personal Values Statement

Creating a diphone inventory

Creating a new entity

Creating a new industry - material flows

Creating a project

Creating a sustainable supply chain

Creating an Effective Safety Control Structure

Creating an Entrepreneurial Procurement Organization

Creating an Industry

Creating an Operations Safety Management Plan

Creating and Hosting Database

Creating and Robert Fritz

Creating chart

Creating closer relationships

Creating combinations

Creating custom image

Creating database

Creating five common steps

Creating formal chemical bonds

Creating inner circles

Creating multiple laser traps acousto-optical deflectors

Creating multiple regression models

Creating new

Creating the Proximal Event Chain

Creating the Steering Committee

Creating the Value Chain Model

Creating the inventory table

Creating the responsive supply chain

Creating the site quality plan

Creating workbooks

Custom function creating simple

Custom toolbutton creating

Damage created

Deformation of Networks with Stiff Aromatic Segments and Relatively Flexible Aliphatic Junctions Created from Reactive End-Caps

Directory create

Disease, creating

Effective RF Fields Created by a PIP

Electrolysis A Controlled and Reproducible Way to Create Surface Nanobubbles

Electron Transport Creates an Electrochemical Potential Gradient for Protons across the Inner Membrane

Electron capture creating thermal electrons

Elimination Reactions Create Pi Bonds

Enzymes create pharmaceuticals

Enzymes creating maleimide-activated

Equalization creating space with

Events creating

Fabrics side views as created by pcGINA

Factors Creating Stratification Management of LNG Rollover

Function procedure creating simple

Functionalities creating specific chemical

General Approach to Creating Tables

Getting Started Using the Recorder to Create a Sub Procedure

Grignard reaction created

Hazards, technology-created

How Value is Created in Chemical LBOs

How chain orientation is created

How to Create an Add-In Macro

Innovation states creating, centers

Instrumentation creating

Laboratory-created artifacts

Laser manipulation to create new states

Leadership trust, creating

Listings, creating

Living organisms biominerals created

Location of General Exhaust to Create Displacement Flow

Loops creating

Maleic creating

Matlab creating figures

Mechanisms model Creating joints

Modeling the Self Assembly of Ternary Blends that Encompass Photosensitive Chemical Reactions Creating Defect-Free, Hierarchically Ordered Materials

Networks from Aromatic Linear Chains Created by Reacting Backbone Diacetylene or Pendant Acetylene Groups

Not All Acids and Bases Are Created Equal

Organizational culture: creating

Oscillatory Systems Created with Polymer Membranes

Other Reported Incidents in Which Failure to Remove Blinds Created Troubles

Oxygen creating

Patient listings, creating

Permeability hydraulically created

Photochemical excitation creating radicals

Pipefitters Can Create Troubles When Reinstalling Relief Valves

Polar covalent bonding Creating partial charges

Polarizability differences create forces

Polymerizable Species Created in DC Cathode Glow

Polymerizable Species Created in Jet Stream of Luminous Gas

Problems created

Procedure creating simple

Process failures creating, 55 described

Projects creating

Protein Engineering to Create New Properties

REPORT procedure creating listings

REPORT procedure creating tables

Reactions That Create a Chirality Center

Reactions That Create a Stereogenic Center

Regions creating

Regression creating models

Repaired Reboiler Passes the Hydrotest and Later Creates a Fire

Responsibilities creating positions

Resume package creating

SAS Tools for Creating Clinical Trial Graphs

Safe learning environments creating

Scheme for creating stable dispersions from

Sell-Created Position

Some Worksheet Functions Used Within VBA Create an Array

Some of the Many Unpublished Errors Created with Hoses

Spectrum creating

Standard Operating Procedures creating

Static creating drops

Steering committee creating

Step 2 Creating the Safety Observation Process

Subcircuit creating

Supersaturated state, creating

Support in Creating and Maintaining Accurate Process Models

Surface area, creating adsorption

Surface area, creating adsorption isotherms

Synthetic Strategies for Creating Molecular Diversity

Systems creating

Tables, creating

The Misuse of Hoses Can Quickly Create Problems

The Words Engineer and Create

Tracks creating

Training Plan creating

USING THE HANDWRITING ANALYSIS TO CREATE INSTANT ATTRACTION

Umbrella Brand Degussa Creating Essentials

Used Known Relative Atomic Masses to Create the Periodic Table

Using AutoFill to Create a Series

Using Create Names

Using PROC REPORT to Create Clinical Trial Tables

Using PROC TABULATE to Create Clinical Trial Tables

Vacuum creating

Value creating strategy

Virtual instrument creating

Viruses creating

Visuals creating

Werners Notion—Creating the Field Synthesis and

XML files creating

© 2024 chempedia.info