Sulphur specifications

SULPHUR

DESCRIPTION:          Bright yellow granular material, free from dart.

SPECIFICATIONS:

Sr. No.	Parameters	Requirements
1.	Elemental sulphur (%by mass )	99.50
2.	Moisture content,max (%by mass )	0.15
3.	Ash, max (%by mass )	0.20

Phosphoric acid specifications

 PHOSPHORIC ACID

DESCRIPTION: It is a clear, colourless, odour less viscous liquid

SPECIFICATIONS:

Sr.No	Parameters	Requirements
1.	Purity (as H3PO4)Percent by mass, min	85
2.	P2O5 content percent by mass, min	61
3.	Iron (ppm), max.	300
4.	Fluoride mg/kg. max	10
5.	Total heavy metals (as pb) mg/kg.max	10
6.	Lead, mg/kg. max	05
7.	Arsenic (as As) mg/kg max.	03

Vapour velocities in evaporator bodies

AS PER HUGOT VAPOUR VELOCITIES RECOMMENDED
	Triple in m/sec		Quadruple in m/sec		Quintuple in m/sec
	Min	Max	Min	Max	Min	Max
Exhaust steam to 1st effect	25	30	25	30	25	30
Vapour from 1st effect	30	35	30	35	30	35
Vapour from 2nd effect	40	45	35	40	30	35
Vapour from 3rd effect	50	60	40	45	35	40
Vapour from 4th effect			50	60	40	45
Vapour from 5th effect					50	60

properties of steam

Properties of Steam

In evaporator calculations, the properties of saturated steam are involved at every step. We shall find in Table 41.1 (Hugot page no. 1034):

(1) The boiling point " t " of water corresponding to each pressure

(2) The sensible heat "q "contained in water which has attained that temperature

(3) The latent heat or heat of vaporisation r of water, for this temperature, i.e. the quantity of heat units which must be supplied to the water to change it into and temperature given.vapour at the pressure

For the temperatures which are met with in evaporation work, these two quantities of heat, q and r, may be obtained with sufficient precision by the formulae of Regnault

q = t

r = 607 - 0.7t

λ = q + r = 607 + 0.3t

q = sensible heat supplied to unit weight of water to raise it from freezing point to toC expressed in Kcal/kg

r = latent heat of vaporisation of water at toC i.e. the quantity of heat to change unit weight of water into steam at the same temperature, in kcal/kg

λ = total heat to be supplied to unit weight of water, starting at 0°C (32°F), to change it to steam at t°, expressed in kcal/kg

Role of phosphoric acid in sugar process

Role of phosphoric acid 

Phosphoric acid occurs in the cane in two principal forms:

(a) Soluble phosphates of the juice

(b) In combination as protein in the cell material.

The latter compounds being insoluble, only the soluble phosphates take part in the defecation.

They react with the lime and form a precipitate which constitutes an important part of the floc produced in the juice by the lime.

It has been shown that the greater the amount of phosphoric acid in the juice, the easier

is the clarification. The mean phosphate content of normal juice is approximately 250mg P2O5 per litre.

Unfortunately, certain varieties of cane give a juice poor in phosphoric and which

is difficult to treat.

These juices are improved by adding to them artificially, before defecation, the quantity

of phosphoric acid by which they are deficient.

Action of phosphoric acid on the juice

The phosphoric acid added to the juice precipitates part of the colloids and colouring matter

which it contains.

The precipitate formed with lime is mainly tricalcium phosphate. This unfortunately is a

gelatinous precipitate and difficult to filter.

Advantages

The use of phosphoric acid improves the clarification of refractory juices.

It often permits of eliminating the sulphitation. In other words, it is possible, to a certain

extent, to replace sulphurous by phosphoric acid.

Considered from this angle, phosphoric-acid clarification is much less expensive than

sulphitation, does not require special equipment, avoids corrosion of plates and pipes, and reduces scaling at heaters and multiple effects.

However, phosphoric acid should rather be regarded, not as a replacement, but as an adjunct to the clarification, which should be considered when exceptional difficulties are encountered in subsidation or filtration.