Sugar Cane Milling, Components, and Quality (Other (Not Listed) Sample)

2.0 LITERATURE REVIEW
Under the chapter of literature review, it focuses on the studies that related to the project. All the theories, observations, surveys, recitations and understanding of the documentations regarding the project are needed. These are for ensuring the project can be carried out in a better and smoother condition. Other information such as materials used, mechanism involved and software used for the purpose of analysis also will be included in this chapter
2.1 Welding
2.1.1 Welding Stainless and Shielding gasses for MIG
The best gas for MIG welding stainless is 97.5% Argon +2.5% CO2. Previously an Argon/Oxygen mix was widely used, but this doesn't give as smooth a finish as the Argon/CO2 mix. For mild steel welding 80% Argon plus 20% CO2 is common, with 95% Argon plus 5% CO2 often used for thin sections, but even 5% CO2 is too oxidizing for stainless and will leave the weld looking black. There are 2 common grades of stainless: 304L (welded using 308L filler), and 316L which is welded using 316L filler. There are a number of grades that do similar jobs, 302L, 303L and 304L (they are 17/7, 18/8 and 19/9 respectively). 308L is 20/10 so can be used to weld all 3 grades.
Stainless is easy to weld but very difficult to keep flat, the coefficient of linear expansion is 1.7 times that of mild steel. There isn’t much you can do about that except to weld it quickly and by doing so minimize the heat input. 304 and 316 suffer from weld decay. When heated to welding temperatures the Chromium combines with the Carbon leaving the steel short of Chromium and therefore unable to self-repair itself. This was virtually eliminated by introducing stabilized stainless steels 347 and 321, which contain Niobium, or Titanium, which sacrifices itself to save the Chromium, however, when lower carbon versions 304L and 316L were introduced the problem of weld decay, was eliminated. These days the higher (in fact, normal) carbon versions are only used for applications where heat resistance is needed.
2.2 Milling
During the milling process, the cane billets are shredded and crushed through several milling units to rupture the cells and extract juice from the fibrous material. The milling units consist of two rollers that crush the cane and extract the juice. Simple rollers mills are commonly employed, with mills using four to six sets of milling units. Juice extracted from the pressure feeder and the first pair of rollers of the No. 1 mill is termed first expressed juice (FEJ).
The features of the proposed sugar extraction system lie between milling and diffusion, but they are closer to milling because the extraction is attained by mixing/separation, whereas diffusion should ideally occur by the mass transfer phenomenon known as displacement. The underlying sugar extraction system employs mixing/separation with better mixing efficiency than roller mills by using rollers . It is also a countercurrent extraction; however, a simple sieve is used to separate the solids without any dewatering aid. Unlike roller mills, the extracted juice did not re-absorbed, maintenance costs were a lot lower, and the capital investment of a press was 2/3 that of a roller mill of similar capacity. Because they were used to replace roller mills to obtain maximum dewatering capacity, the rollers presses saw high abrasive stresses. They required frequent maintenance, which increased plant downtime; thus, their use was discontinued. The applied pressure should be kept below 213 psi or 1470 kPa; above this, the resistance of the megasse increases rapidly increasing the power requirement exponentially and the wear and tear of the equipment. For comparison, a conventional roller mill operates in the 70 – 300 kgf/cm2 (995 – 4270 psi or 6865 – 29420 kPa) range. This exposes an inefficiency of roller mills because they must spend a lot of their energy “fighting” bagasse resistance rather than dewatering it. Starrett performed power consumption studies of the dewatering of sugarcane bagasse with rollers presses, but, as mentioned, his conditions were different than ours because he was trying to attain maximum dewatering capacity. In contrast, in our proposed process, only light pressure is applied.
To extract sugar from sugarcane, slope rollers diffuser has been designed to aid the usual surface extraction by “frequent, repeated light compressions of the cane, which permits reabsorption of juice somewhat less concentrated than that squeezed out.” This is accomplished by using a long double rollers conveyor (G.C.). The rollers rotate in opposite directions and the cane gently slides around the rollers each as it is conveyed. Each time the cane rotates, it is squeezed in the narrow space between the shafts of the intermeshing rollers . The advantage of this system is that it does not depend on cane preparation; shredded/crushed and shredded-only cane yields approximately the same extraction. These studies confirm the effectiveness of the applied gentle squeeze in sugar extraction.
2.3 Sugar Cane Plant
The sugar cane plant (Saccharum officinarum L.) is a tall thick-stemmed perennial grass grown in tropical and subtropical countries and is one of the main sucrose producing crops worldwide. The sugar cane plant is one of the most photo synthetically efficient plants, and a mature cane plant can extend ≤ 4 m in height with a diameter of ≤ 40 mm. Sugar is produced from the sugar cane plant, and it is stored within the sucrose-rich stalk, which is supported by fiber. In Kenya, sugar cane is typically harvested during the summer and spring seasons from July through to November, when the sugar cane plants contain the highest level of sucrose. The length of each season is dependent on the climate conditions.
2.3.1 Sugar cane components
A mature sugar cane plant has two distinct sections, which contain various levels of sucrose and soluble (e.g., glucose, fructose, inorganic ions, organic acids, polysaccharides, proteins and amino acids) and insoluble (e.g., soil, proteins, starch, lipids and wax) non-sucrose components. The main components of the sugar cane plant are stalk of the whole plant. The trash component is typically separated during harvesting due to the higher ratio of non-sucrose to sucrose components. Trash is typically used as a blanket over the cane fields in order to preserve moisture and to enrich soil with organic carbon, nitrogen and phosphorus, thereby assisting the growth of the sugar cane plant. The cane variety and maturity as well as the climatic conditions and location in which the cane is grown are all fa