Heat optimisation

Selection of the high pressure steam conditions is an economic optimisation based on energy savings and equipment costs. Heat recovery iato the high pressure system is usually available from the process ia the secondary reformer and ammonia converter effluents, and the flue gas ia the reformer convection section. Recovery is ia the form of latent, superheat, or high pressure boiler feedwater sensible heat. Low level heat recovery is limited by the operating conditions of the deaerator. 

Most processing is thermal. Reaction systems and separation systems are typically dominated by the associated heat exchange. Optimisation of this heat exchange has tremendous leverage on the ultimate process efficiency (see HeaT-EXCHANGETECHNOLOGy). 

Corti and Manfrida [2] have also done detailed calculations of the performance of plant A2. They drew attention to the need to optimise the amines blend (including species such as di-ethanolamine and mono-ethanolamine) in the absorption process, if a removal efficiency of 80% is to be achieved and in order to reduce the heat required for regenerating the scrubbing solution. Their initial estimates of the penalty on efficiency are comparable to those of Chiesa and Consonni (about 6% compared with the basic CCGT plant) but they emphasise that recirculation of water from... 

Anxionnaz, Z., Cabassud, M., Gourdon, C., and Tochon, P. (2009) Hydrodynamic study and optimisation of the geometry of a heat exchanger/reactor. 2nd European Process Intensification Conference 2009, Venice. 

Various extraction methods for phenolic compounds in plant material have been published (Ayres and Loike, 1990 Arts and Hollman, 1998 Andreasen et ah, 2000 Fernandez et al., 2000). In this case phenolic compounds were an important part of the plant material and all the published methods were optimised to remove those analytes from the matrix. Our interest was to find the solvents to modily the taste, but not to extract the phenolic compounds of interest. In each test the technical treatment of the sample was similar. Extraction was carried out at room temperature (approximately 23 °C) for 30 minutes in a horizontal shaker with 200 rpm. Samples were weighed into extraction vials and solvent was added. The vials were closed with caps to minimise the evaporation of the extraction solvent. After 30 minutes the samples were filtered to separate the solvent from the solid. Filter papers were placed on aluminium foil and, after the solvent evaporahon, were removed. Extracted samples were dried at 100°C for 30 minutes to evaporate all the solvent traces. The solvents tested were chloroform, ethanol, diethylether, butanol, ethylacetate, heptane, n-hexane and cyclohexane and they were tested with different solvent/solid ratios. Methanol (MeOH) and acetonitrile (ACN) were not considered because of the high solubility of catechins and lignans to MeOH and ACN. The extracted phloem samples were tasted in the same way as the heated ones. Detailed results from each extraction experiment are presented in Table 14.2. 

LC-APCI-MS is a derivative of discharge-assisted thermospray, where the eluent is ionised at atmospheric pressure. In an atmospheric pressure chemical ionisation (APCI) interface, the column effluent is nebulised, e.g. by pneumatic or thermospray nebulisation, into a heated tube, which vaporises nearly all of the solvent. The solvent vapour acts as a reagent gas and enters the APCI source, where ions are generated with the help of electrons from a corona discharge source. The analytes are ionised by common gas-phase ion-molecule reactions, such as proton transfer. This is the second-most common LC-MS interface in use today (despite its recent introduction) and most manufacturers offer a combined ESI/APCI source. LC-APCI-MS interfaces are easy to operate, robust and do not require extensive optimisation of experimental parameters. They can be used with a wide variety of solvent compositions, including pure aqueous solvents, and with liquid flow-rates up to 2mLmin-1. 

For any network there will be a best value for the minimum temperature difference that will give the lowest total annual costs. The effect of changes in the specified ATIllin need to be investigated when optimising a heat recovery system. 

In this example the outlet exit gas composition has been calculated for an arbitrarily chosen steam CO ratio of 3. In practice the calculation would be repeated for different steam ratios, and inlet temperatures, to optimise the design of the converter system. Two converters in series are normally used, with gas cooling between the stages. For large units a waste-heat boiler could be incorporated between the stages. The first stage conversion is normally around 80 per cent. 

Nie X-R (1998) Optimisation Strategies for Heat Exchanger Network Design Considering Pressure Drop Aspects, PhD Thesis, UMIST, UK. 

During optimisation of a preparative procedure, heating mixtures of 4-chloroaceto-phenone and dimethylamine (4.22 1) at 234°C led to two explosions. Use of a safety screen is advised. 

The procedure of Lifson and Warshel leads to so-called consistent force fields (OFF) and operates as follows First a set of reliable experimental data, as many as possible (or feasible), is collected from a large set of molecules which belong to a family of molecules of interest. These data comprise, for instance, vibrational properties (Section 3.3.), structural quantities, thermochemical measurements, and crystal properties (heats of sublimation, lattice constants, lattice vibrations). We restrict our discussion to the first three kinds of experimental observation. All data used for the optimisation process are calculated and the differences between observed and calculated quantities evaluated. Subsequently the sum of the squares of these differences is minimised in an iterative process under variation of the potential constants. The ultimately resulting values for the potential constants are the best possible within the data set and analytical form of the chosen force field. Starting values of the potential constants for the least-squares process can be derived from the same sources as mentioned in connection with trial-and-error procedures. 

Catalysts from active carbon promoted with mixed Ni-Co- oxides are investigated [8], These catalysts are produced by heat-treatment of active carbon impregnated with solution containing Co-and Ni-acetates. The concentration of the used Co and Ni- solutions is varied in order to optimise the content of the mixed Co-Ni oxides in the catalyst. 

Owing to the fact that nearly all the heat generated by this type of electrolyser has to be dissipated via the anolyte flow, for the full industrial-scale demonstration electrolyser with an element size 2.5 m2 it was decided to use the bubble jet system [3], which was successfully tested previously with the chlor-alkali method. For FIC1 electrolysis, which from the material side is optimised to an approximate operation temperature of 60°C, an intense vertical temperature-profile flattening is essential to reduce the external flow rates and to allow rather low anode-side inlet temperatures. The intensive vertical mixing with the bubble jet proved to be suitable for this purpose. 

The model of a mercury cell described in this chapter represents an effective combination of empirical data accumulated over several years of operation and theoretical heat and mass balance equations. Modern software tools and fast desk-top computers make the task of implementing the model relatively straightforward and of low cost so that it can be exploited for plant optimisation. 

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