Production batch processes

Continuous processes will usually be more economical for large scale production. Batch processes are used where some flexibility is wanted in production rate or product specification. 

Single-point fuel injection system, 10 51 Single-product batch processes, 20 723 Single radial immunodiffusion (SRID) technique, 25 494... 

If properly proportioned and preheated, the reaction can be run continuously to produce molten ammonium nitrate containing very little water (1 to 5%), which can be formed into small spheres (prills) by dropping the reaction product through a shot tower or into flakes by cooling it on belts or drums. By fluidized bed treatment, it is possible to obtain a dry granular material as product batch processes have also been used. 

Communication of requirements of time and manpower to the quality control department is a critical issue that must not be overlooked. Prompt attention to analysis needs does help keep the pilot production batch process moving forward. If microbiological release of bulk product is needed before packaging, the project timeline should reflect the time period (3-5 days) generally needed for this activity. 

Interestingly, at the scale of a process all the same things are done, but typically continuously for large scale production. Batch processes, however, can be scaled up to larger volumes, and this is done in processes that yield specialty chemicals or pharmaceuticals with high added value. We will consider the continuous process run at steady state. The physical situation is as shown in Figure 5. 

Production planning Determination of local production quantities and assignment to local plants.i Fbr multi-product batch processes, the aim is to define batch sizes for different chemicals and to assign them to available plants. In case of multi-product continuous processes, the aim is to determine the production mode, i.e. the physical conditions and raw material composition specifying the product mixture. ... 

Economics. Continuous processes are usually cheaper for large volume production. Batch processes are usually cheaper for specialty polymers. 

Some of the steps in the refining process can be conducted continuously, but this is not common practice and the associated plant is only justified for large lead refineries over say 120 000 t/a of lead production. Batch processing can be highly flexible and is more easily controlled to final product specifications. Because of the high density of lead one batch is commonly around 200 tonnes and the number of batches required per day is quite limited. 

In a batch process, the main steps operate discontinuously. In contrast with a continuous process, a batch process does not deliver its product continuously but in discrete amounts. This means that... 

Example 4.5 Given that a low rate of production is required, convert the continuous process from Example 4.4 into a batch process. Preliminary sizing of the equipment indicates that the duration of the processing steps are given in Table 4.7. ... 

Figure 4.16 Final flowsheet for the production of butadiene sulfone in a batch process.

Higher alkyl acrylates and alkyl-functional esters are important in copolymer products, in conventional emulsion appHcations for coatings and adhesives, and as reactants in radiation-cured coatings and inks. In general, they are produced in direct or transesterification batch processes (17,101,102) because of their relatively low volume. 

The above batch process has undergone numerous refinements to improve yields, processing characteristics, purity, and storage stabiUty, but it remains the standard method of manufacture for these products. Recentiy a continuous process has been reported by Bayer AG (6) wherein the condensation is carried out in an extmder. The by-products are removed in a degassing zone, and the molten polymer, mixed with stabilizers, is subsequendy cracked to yield raw monomer. 

Suspension polymerization of VDE in water are batch processes in autoclaves designed to limit scale formation (91). Most systems operate from 30 to 100°C and are initiated with monomer-soluble organic free-radical initiators such as diisopropyl peroxydicarbonate (92—96), tert-huty peroxypivalate (97), or / fZ-amyl peroxypivalate (98). Usually water-soluble polymers, eg, cellulose derivatives or poly(vinyl alcohol), are used as suspending agents to reduce coalescence of polymer particles. Organic solvents that may act as a reaction accelerator or chain-transfer agent are often employed. The reactor product is a slurry of suspended polymer particles, usually spheres of 30—100 pm in diameter they are separated from the water phase thoroughly washed and dried. Size and internal stmcture of beads, ie, porosity, and dispersant residues affect how the resin performs in appHcations. 

Several manufacturiag processes can be used to produce phenohc foams (59,79) continuous production of free-rising foam for slabs and slab stock similar to that for polyurethane foam (61,80) foam-ia-place batch process (61,81) sandwich paneling (63,82,83) and sprayiag (70,84). 

The process options reflect the broad range of compositions and gas volumes that must be processed. Both batch processes and continuous processes are used. Batch processes are used when the daily production of sulfur is small and of the order of 10 kg. When the daily sulfur production is higher, of the order of 45 kg, continuous processes are usually more economical. Using batch processes, regeneration of the absorbant or adsorbant is carried out in the primary reactor. Using continuous processes, absorption of the acid gases occurs in one vessel and acid gas recovery and solvent regeneration occur in a separate reactor. 

The majority of thermal polymerizations are carried out as a batch process, which requires a heat-up and a cool down stage. Typical conditions are 250—300°C for 0.5—4 h in an oxygen-free atmosphere (typically nitrogen) at approximately 1.4 MPa (200 psi). A continuous thermal polymerization has been reported which utilizes a tubular flow reactor having three temperature zones and recycle capabiHty (62). The advantages of this process are reduced residence time, increased production, and improved molecular weight control. Molecular weight may be controlled with temperature, residence time, feed composition, and polymerizate recycle. 

The yield of hydroquinone is 85 to 90% based on aniline. The process is mainly a batch process where significant amounts of soHds must be handled (manganese dioxide as well as metal iron finely divided). However, the principal drawback of this process resides in the massive coproduction of mineral products such as manganese sulfate, ammonium sulfate, or iron oxides which are environmentally not friendly. Even though purified manganese sulfate is used in the agricultural field, few solutions have been developed to dispose of this unsuitable coproduct. Such methods include MnSO reoxidation to MnO (1), or MnSO electrochemical reduction to metal manganese (2). None of these methods has found appHcations on an industrial scale. In addition, since 1980, few innovative studies have been pubUshed on this process (3). 

Manufacture of ion-exchange resins has traditionaHy been a batch process. Significant progress was made more recentiy in the development of a continuous process for the manufacture of copolymer beads. However, as of this writing (ca 1994) is it not used by aH manufacturers. Moreover, those companies having continuous processing capabiHties do not use it for aH ion-exchange products. 

Pre-Production Handling. Salt-cured catde hides, when received at the tannery, are individually bundled to prevent excessive moisture loss. The bundles are tied with ropes that are later cut and removed the hides may be sorted for different weight or quaUty classification at this point. It is best to have hides of similar size and thickness in a given production batch to assure an even reactivity of the processing chemicals and to avoid frequent adjustments in the machinery to compensate for size and thickness variations. In the modem large tannery, the size/quaUty classification is not necessary because the hides arrive in carload quantities under specifications as to size, type, and month of slaughter. 

Soa.king. The hides are weighed and counted into production batches. For pre-fleshed and trimmed catde hides the batches are about 3—5 t when the processing is in dmms. If the tannery has hide processors the batches may be up to 10 t. Water is added to cover the hides and allow free movement of the load. The dmm is turned intermittently during the normal 8 to 16-hour soaking period. 

Pasteurization may be carried out by batch- or continuous-flow processes. In the batch process, each particle of milk must be heated to at least 63°C and held continuously at this temperature for at least 30 min. In the continuous process, milk is heated to at least 72°C for at least 15 s ia what is known as high temperature—short time (HTST) pasteurization, the primary method used for fluid milk. For milk products having a fat content above that of milk or that contain added sweeteners, 66°C is requited for the batch process and 75°C for the HTST process. For either method, foUowiag pasteurization the product should be cooled quickly to <7.2° C. Time—temperature relationships have been estabHshed for other products including ice cream mix, which is heated to 78°C for 15 s, and eggnog, which must be pasteurized at 69°C for 30 min or 80°C for 25 s. 

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