Side-stream system

A Side-stream systems - airlift [Norit X-flow) B Ultra-Flo - side-stream dead-end setup... 

Figure 16.17 Examples of side-stream systems based on airlift or deadend mode.

Similar to methanamide, ammonium formate decomposition proceeded in a wide temperature window. As ammonium formate does in fact not need to be hydrolyzed, formic acid decomposition is the limiting reaction for the quantitative conversion of the precursor solution to NH3 and CO2. However, if mixtures with urea, such as Denoxium are being used, the temperature needs to be sufficient to enable urea hydrolysis. Therefore, an in-pipe or side stream system equipped with an Au/Ti02 hydrolysis catalyst could in fact be used to provide NH3 from either AdBlue , Denoxium or Admide(R). This would enable the flexibility to ensure efficient NH3 production, and, consequently, NO reduction, even in cold climates or during long refill intervals. Guanidinium formate solution would also be an optional NH3 precursor solution for a side stream reactor if the reactor could be electrically heated at temperatures below 250 °C, but would not qualify for direct injection into the main exhaust pipe. 

In the side-stream configuration, the MLSS is pumped through the membrane module. Side-stream systems typically use tubular membranes. Fouling is controlled by a well-defined flow velocity in the range of l-4m/s, generating a turbulent crossflow. Figure 9.7 shows a schematic view of a side-stream system. 

The normal regeneration temperature in the still will not regenerate heat-stable salts or oxazolidone-2. Therefore, a reclaimer is usually included to remove these contaminants. A side stream of from 1 to 3% of the MEA circulation is drawn from the bottom of the stripping column, This stream is then heated to boil the water and MEA overhead while the heat-stable salts and oxazolidone-2 are retained in the reclaimer. The reclaimer is periodically shut in and the collected contaminants are cleaned out and removed from the system. However, any MEA bonded to them is also lost. 

When MEA is used in the presence of COS and CS2, they react to form heat-stable salts. Therefore, MEA systems usually include a reclaimer, The reclaimer is a kettle-type reboiler operating on a small side stream of lean solution. The temperature in the reclaimer is maintained such that the water and MEA boil to the overhead and are piped back to the stripper. The heat-stable salts remain in the reclaimer until the reclaimer is full. Then the reclaimer is shut-in and dumped to a waste disposal. Thus, the impurities are removed but the MEA bonded to the salts is also lost. 

For DEA systems a reclaimer is not required because the reactions with COS and CS2 are reversed in the stripper. The small amount of degradation products from COo can be removed by a carbon filter on a side stream of lean solution. 

Insoluble suspended matter either picked up from the atmosphere or formed by deposition and corrosion within the system, together with slimes will, if not removed, cause blocking and abrasion problems. The build-up of such material can be controlled by side stream filtration, in which about 2-5 per cent of the circulating water flow is filtered continuously. A sand filter is commonly used for this type of duty. 

The exposure of sensors in a by-pass stream (which can be valved off), is an alternative way of collecting monitoring data although correlation is required between the main-stream and the by-pass The use of a side-stream taken either side of a choke in the main-stream can provide a useful monitoring point. Traps where product streams can be condensed can offer alternative sampling systems. 

Finally, the use of side-stream filters is recommended. Bag filters generally are satisfactory, although for the removal of the finest iron particles, an in-series twin-bag system may be required use 5 to lOjx bags followed by 1 to 2 x. Where only one bag filter is employed, use either conventional 5 x filters or high-quality depth filters. 

The state variables are the minimal set of dependent variables that are needed in order to describe fully the state of the system. The output vector represents normally a subset of the state variables or combinations of them that are measured. For example, if we consider the dynamics of a distillation column, in order to describe the condition of the column at any point in time we need to know the prevailing temperature and concentrations at each tray (the state variables). On the other hand, typically very few variables are measured, e.g., the concentration at the top and bottom of the column, the temperature in a few trays and in some occasions the concentrations at a particular tray where a side stream is taken. In other words, for this case the observation matrix C will have zeros everywhere except in very few locations where there will be 1 s indicating which state variables are being measured. 

An external feed of any amount, of one or more components, can be fed to any stage in the system of columns. This stage may be a plate, a reboiler, or a condenser. All external feed compositions, flows, and enthalpies are independent variables that are set in the problem description. A side stream of either vapor or liquid (or both) may be withdrawn from any stage except a reboiler or condenser, and either removed as product or sent to any stage of any column. The flow of each side stream... 

Destination (stage and column) for each side stream that is not a product removed from the system of columns. 

Next, side streams are read as shown in the program, and possible linkages through streams from end stages being sent to other points are read. The liquid stream from the bottom of a column, for example, will be considered a product leaving the system of columns unless it is specified as going to some other point. Since such a stream could be a dependent variable with its amount unknown, it cannot be sent back to the same column. 

NT024 Zhang, ]., Y. Liu, ]. Shi, D. F. Larson, and R. R. Watson. Side-stream cigarette smoke induces dose-response in systemic inflammatory cytokine production and oxidative stress. Exp Biol Med (Maywood) 2002 227(9) 823-829. 

Crude oil fractionators are an example of a more elaborate system. They make several products as side streams and usually have some pumparound reflux in addition to top reflux which serve to optimize the diameter of the tower. Figure 3.13 is of such a tower operating under vacuum in order to keep the temperature below cracking conditions. The side streams, particularly those drawn off atmospheric towers, often are steam stripped in external towers hooked up to the main tower in order to remove lighter components. These strippers each have four or five trays, operate... 

Figure 3.13. Crude oil vacuum tower. Pumparound reflux is provided at three lower positions as well as at the top, with the object of optimizing the diameter of the tower. Cooling of the side streams is part of the heat recovery system of the entire crude oil distillation plant. The cooling water and the steam for stripping and to the vacuum ejector are on hand control.

The building block of the superstructure representation is the generic reactor unit, which follows the shadow reactor concept (32). This generic unit is illustrated in Figure 4. Each generic unit consists of reactor compartments in each phase of the system, and each processes the reaction. The shadow reactor compartment assumes a state from the set of homogeneous reactors. The default units in the set include CSTRs and PFRs with side streams. The interface between a given pair of... 

Nikolaides IP, Malone MF. Approximate design of multiple-feed/side-stream distillation systems. Ind Eng Chem Res 1987 26 1839. 

Consider the equipment system schemed in Fig. 3.8, where the subscript B denotes the process particles and A the tracer. Corresponding to the impinging stream equipment with feeding on both sides, the system has two feeds, which are denoted by the superscripts (1) and (2), respectively while it has only one out stream of particles. For convenience of operation, the tracer A is inputted into one feeding stream, i.e., (2) ... 

---