The Cleaning Operations

Washing/scouring and bleaching are the two operations of cleaning the fabrics. 

Scouring aims to wash out the chemical auxiliaries used in assisting the spinning, knitting or weaving. 

The bleaching process also has peculiarities depending on the type of fibre which is treated. The most common and environmentally friendly bleaching agent used for fibres is hydrogen peroxide. Cotton is also partly bleached while scouring, under the action of sodium chlorite. Some yellow wools or bast fibres may require a harsher bleaching, for which reason sodium dithionite or sodium formaldehyde sulphoxylate (for wool) and sodium chlorite (for bast fibres) are also used. 

Due to the fact that chemical fibres are produced under controlled parameters, their cleaning requires fewer chemicals and even the bleaching is, sometimes, unnecessary. 

A common bleaching agent used domestically (more particularly in Mediterranean countries and North America) is Javel water, which is sodium hypochlorite in water. 

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Lubrication of Wire Rope after Socket Attachment. After the resin has cured, relubricate the wire rope at the base of the socket to replace the lubricant that was removed during the cleaning operation. 

No matter which method of cleaning is adopted, it is desirable to apply the primer or coating immediately after the cleaning operation. 

The type of operation considered in the zero effluent methodology means that the amount of time points used for an operation has to increase. This is due to the fact that there is a processing step and a cleaning step associated with each batch of product. Normally two time points are used to describe a task in a unit. The first time point is used when the task commences in a unit and the second when the task terminates in a unit. In the type of operation considered in the zero effluent models, three time points are used. At the first time point the raw material processing task commences. The raw material processing step ends at the second time point, where the final product is removed and the cleaning operation commences. At the third time point the cleaning operation comes to an end and wastewater is produced. 

Directly after product has been produced from a task in a unit, the cleaning operation in the unit begins. Constraints (8.17) and (8.18) ensure that the time at which product is produced and the time at which a cleaning operation begins in a unit... 

The starting and ending times of a cleaning operation in a unit are related through the cleaning operation duration constraint given in constraint (8.19). This constraint is similar to the task duration constraint given earlier. 

Due to the fact that it is assumed that a washout occurs directly after product is removed, two consecutive batches of product will be separated by a washout. In terms of time points, a unit can only start processing a batch two time points after the first batch starts. This is due to the fact that three time points are used to describe the batch processing and unit cleaning operations. Furthermore, the assumption that a cleaning operation follows product removal negates the need for a separate binary variable to represent the cleaning operation in a unit. Therefore, constraint (8.20) is included to ensure that two product producing tasks do not occur in consecutive time points. 

Constraint (8.21) ensures that a unit can only start processing a batch once the unit has finished the cleaning operation. Constraints (8.22) and (8.23) ensure that if a unit starts operating or finishes operating at a later time point, the time at which this occurs corresponds to a later time in the time horizon. 

It must be noted that the outlet concentration of wastewater generated by the cleaning operation is fixed. This is due to the amount of water used for a cleaning operation being fixed and the mass load also being fixed. 

As can be seen in Fig. 8.4 mixer 1 mixes product 3 exclusively and recycles the resulting effluent directly for two of the three batches of product 3. At the end of the third batch of product 3, 500 kg of water is discarded as effluent since there are no further reuse possibilities. Mixers 2 and 3 each produce products 1 and 2. Mixer 2 produces 2 batches of product 2 and after the second batch, 400 kg of water is discarded as effluent. Mixer 2 also mixes one batch of product 1, which after the completion of the cleaning operation produces 400 kg of effluent. Mixer 3 does not produce any effluent. The reason there is effluent generation is that after the final batch of product is mixed there is no further opportunity for reuse, the effluent must then be discarded. 

The use of hydroxyacetic/formic acid in the chemical cleaning of utility boilers is common. It is used in boilers containing austenitic steels because its low chloride content prevents possible chloride stress corrosion cracking of the austenitic-type alloys. It has also found extensive use in the cleaning operations for once-through supercritical boilers. Hydroxyacetic/formic acid has chelation properties and a high iron pick-up capability thus it is used on high iron content systems. It is not effective on hardness scales. 

VOCs can be potentially recycled. Due to their chemical stability, non-flammability, and low latent heat of vaporisation, the method of choice for recovering VOCs from waste oils received during the cleaning operation is distilla-... 

If a part fails inspection because of a bad finish, it is usually reworked by stripping off the paint and returning it to the cleaning operation. 

Normally, 24 h is required to complete the cleaning operation and to prepare the coke drum for subsequent use on-stream. 

The planning group should decide how to vent the system during the cleaning operations, e.g., to the flare, through a caustic wash, or directly to the atmosphere. 

Is the cleaning operation in between batches optimized Is there a possibility of wash-solvent recycle here without affecting the overall product quality ... 

If solubility alone determined the optimal cleaning conditions, a few selections of T and P would determine the conditions for running the reactor. The transport properties of the fluid interacting with the part to be cleaned may be just as important as solubility in determining the overall success of the cleaning operation. Transport effects and scaleup issues are of crucial concern in cleaning and are discussed in detail in the chapter by M. R. Phelps et al. 

The inspector then places it on a pin-type conveyor which makes it possible for the air to circulate freely around each shell, thus as-.suring that the physical properties of each forging are the same. Each conveyor hook has two pairs of pins, one above the other, holding four forgings in all. By the lime the shell reaches the final inspection room, it is completely cooled. Here the shells are given a 100 per cent inspection before they are pas.sed on to the shot blast machine which cleans the inside cavity at the rate of two every 30. sec. After the cleaning operation they are oiled inside with a pre.s-.sure gun sprayer to protect the interior from rust while in transit to the machining contractor. 

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