li)-21.] T.-iiC XeED FOU J^lME AN J) iiuW TO MeET IT. 'ilK'^ 



Fn comparing the two pi-odiicls il must always be borne in 

 mind that one ton of qiiick-Hme is the e(iiiivalent of a little 

 more than 1^} tons of ground limestone, and that consequently, 

 in cases where a long " draw is involved, there may be ample 

 compensation for the additional (juantity of coal consumed in 

 burning, instead of grinding the stone. This consideration 

 brings us to the question of the relative^ 1 uel costs involved in the 

 two cases. To supply the answer in any specific case it would 

 be necessary to know all the conditions, but the following 

 information will be found useful in arriving at a just 

 comparison. 



In the average small pot kiln, lime can usually be burnt with 

 an expenditure of from 7 to 10 cwt. of culm per ton of lime 

 produced. Tn small draw kilns, where the heat losses are con- 

 siderably lessened by the continuous nature of the process, a 

 fuel consumption of 5 to 7 cwt. of coal per ton of lime may be 

 anticipated, and in large draw kilns as little as 4 cwt. of coal 

 is sometimes used. On the other hand, to grind one ton of 

 chalk or limestone will require a])0ut 8-TO horse-power-honrs, 

 correspcmding to the consumption of 40-50 lb. of coal in an 

 average farm steam engine or of J gallons of paraffin if an 

 oil engine is used to drive the mill. 



Although nearly double as much ground stone must be 

 produced in order to be equivalent to the lime, it will be seen 

 that so far as fuel alone is concerned, there is great saving in 

 cost when the stone is ground instead of burnt. If the question 

 is worked out on the present prices of oil and coal the above 

 figures will show that for fuel alone, burnt lime will cost about 

 IBs. a ton, while the equivalent IJ tons of ground stone will 

 cost only about ^s. Gd. for power fuel. Running costs and 

 the first capital cost of the installation, however, will generally 

 be slightly in favour of the kiln. The comparative cost of two 

 equivalent plants, one to burn lime and the other to grind stone, 

 both on a very small scale, w^ould be in the ratio of about 1:8 — 

 in favour of the kiln. [Nfore skill in manipulation and greater 

 previous experience are needed in the case of the kiln than in 

 that of the grinding plant. 



Assuming that the choice of process has been made, we will 

 now^ consider matters connected with limestone grinding plants 

 of small size, such as many faimers could easily instal. 



Small Grinding Plants. — The object of all agricultural stone 

 grinding i)lant is to produce grouiui stone or chalk in a 

 sufficiently fine state of sub-division to enable it to react readily 



