Multipurpose vessel

Can several process steps be carried out in separate processing vessels rather than a single multipurpose vessel This reduces complexity and the number of raw materials, utilities, and auxiliary equipment connected to a specific vessel, thereby reducing the potential for hazardous interactions. 

Perhaps the most important and most readily achievable equipment design to minimize wall decomposition is the use of jacket services on the bottom section of the vessel only. Such services can be provided either by a lower jacket only or, more commonly, by a split jacket to provide for full services in multipurpose vessels. Decomposition can be especially severe on the wall above the boiling surface, where any liquid may evaporate and leave the residual compound to dry and be exposed to the maximum temperature in the jacket (baking). 

In comparison with the rhodium-catalyzed process, the biocatalytic process provides sitagliptin with a 10-13% increase in overall yield, a 53% increase in productivity, a 19% reduction in total waste, the elimination of all heavy metals, and a reduction in total manufacturing cost the enzymatic reaction is run in multipurpose vessels, avoiding the need for specialized high-pressure hydrogenation equipment [28]. 

The development section serves as an intermediary between laboratory and industrial scale and operates the pilot plant. A dkect transfer from the laboratory to industrial-scale processes is stiH practiced at some small fine chemicals manufacturers, but is not recommended because of the inherent safety, environmental, and economic risks. Both equipment and plant layout of the pilot plant mirror those of an industrial multipurpose plant, except for the size (typically 100 to 2500 L) of reaction vessels and the degree of process automation. 

A generic multipurpose fluidized bed is illustrated in Figure 2 (1). The soHds are contained in a vessel and gas is introduced into the system via a distributor, which is typically a drilled plate at the bottom of the vessel. A plenum chamber is provided below the distributor plate. The height of the soHds level above the distributor is called the bed height, and the vertical space above the bed height is called the freeboard. A splash zone may exist as a transition between the bed and freeboard. Cyclones, located either in the freeboard or external to the vessel, are used to remove soHds from the gas stream. Diplegs can return entrained soHds directly to the bed. 

Papageorgiou, L.G., Shah, N., Pantelides, C.C., 1994. Optimal scheduling of heat-integrated multipurpose plants. Ind. Eng. Chem. Res., 33 3168-3186 Peneva, K., Ivanov, B., Bancheva, N., 1992. Heat integration of batch vessels at fixed time interval. 

Pipeless plants are an alternative to the traditional recipe-driven multipurpose batch plants with fixed piping between the units. In this production concept, the batches of material are moved around between stationary processing stations in mobile vessels. The processing steps are performed at different single purpose or multipurpose stationary units but the material remains in the same vessel throughout the production process. The transportation of the mobile vessels can be realized by a transportation system that is fixed to the vessels or by automated guided vehicles (AGV) that pick up the vessels only to perform a transfer order [1]. 

On the other hand, in comparison to traditional recipe-driven multipurpose batch plants, new technical requirements arise from the use of mobile units. An important pre-requisite for a safe and automatic production are reliable docking systems that provide failure-free connections between the mobile vessels and the stationary processing stations. In the docking process of the mobile vessels the connection of pipes, of electric power and of signal processing equipment is necessary. The vessels therefore must be placed accurately. If vessels of different size are used, the connections must be flexible enough to cope with these. 

Comparison ofthe Plant Concepts To be able to compare the pipeless plant concept with the existing multipurpose batch plant, a reference plant was modelled using PPSiM. In the existing plant three conventional batch mixers work in a shifted parallel fashion. The three batch mixers were modelled by three stations and equipped with all technical functions necessary for the production of all recipes. Therefore each batch could be processed at one of the stations and the vessel transfers were limited to the transportation of empty or loaded vessels. All the other parameters of the model, e.g., charging mass flows, the durations of vessel cleanings and the recipes remained unchanged. 

In case of the standard multipurpose batch plant the downtime of the reactors for the product transfer into temporary storage vessels, the transportation of the vessels to the storage and the cleaning of the reactors before product changeover have to be included. This was modelled by an adjustment of the CIP times of the three stations to 60 min. 

At batch sizes of 100 kg the standard multipurpose plant becomes superior to the pipeless plant with respect to the processing time. The reason for this is that the CIP times of the stations and the transfer times of the vessels remain constant in both cases and therefore the portion of the duration of the productive operations becomes smaller in comparison to the processing time. The advantage of the production of several batches in parallel is therefore reduced by the increasing portion of the cleaning times of the stations. 

Containment within the vessel for the credible worst-case scenario reducing the design requirements for the emergency relief system this step is frequently too expensive and impractical in a multipurpose facility. 

Lack of Economy in Size. Fine chemicals are manufactured in discrete campaigns in multipurpose plants. The reactor trains of these plants are similar throughout the industry. Regardless of the size of the companies, their main constituents, the reaction vessels, have a median size in the 4-6m bracket. Therefore, the unit cost per m per hour does practically not vary with the size of the company. 

In the design of a hne-chemical plant the size of the equipment, especially the volume of the reaction vessels, is critical. In order to ensure that the potential customer s needs are met by the capabilities of the plant, this has to be dehned in close coordination with the marketing and sales function. Depending primarily on the differing quantities of the hne chemicals to be produced in the same multipurpose unit, the concentration of substances in the reaction mixture, and the reaction time, there is, however, an upper limit for the size of the reaction vessel and the ancillary equipment. Some factors run countercurrent to the economy of scale and point to small-size equipment ... 

The turn-key multipurpose high pressure pilot unit shown in picture 1 can be used for the continuous extraction of liquid products in a column with structured packings and for the batch extraction of solids in a extraction vessel. It is assembled using the following proven basic modules (see also figure 1) ... 

Obviously, any pressure vessel presents a rupture hazard. However, both design standards and official tests that are enforced by state agencies (or equivalent), in combination with strict inspection procedures limit this hazard to a quasi-zero level, especially on large-scale units. But, some mechanical hazards are often underestimated, especially on R D multipurpose equipments ... 

In most scale-up operations multipurpose equipment is used so one has little choice of specialized equipment. In fact, in many companies it is the equipment available for scale-up operations that defines the processing conditions. For instance, a reduction may be carried out by transfer hydrogenation if a pressuriz-able vessel is not available for hydrogenation using H2 from cylinders. 

The procedure described in the previous section is only applicable, if the reaction vessel considered is used for just one single process. In this case all necessary substance and system data can be obtained experimentally at a reasonable expense. In the fine chemicals and pharmaceutical industry, however, multipurpose plants are preferred. They are required in order to be able to respond adequately to the fast changing development activities and the continuously changing mass demands. During project engineering activities for such a plant the problem may arise that several hundred different syntheses are expected to be performed on this plant, of which may be half are known chemically due to current activities. 

The volumes of reactor and crystallization vessels vary widely, between 1000 and 10,000 L, or in rare cases, 16,000 L. Reactors with standard sizes of 4000 and 6300 L are used most commonly. Multipurpose plants also differ with regard to the degree of sophistication. Simple plants are equipped with jacketed reactors that operate at limited ranges of temperature (-10 to -f 120°C) and pressure (20 mbar to 5 bar). Also, the filters and centrifuges are discharged manually, and the dry section is not contained. Process control is manual. 

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