naturally occurred to them to utilise the crude liquors obtained in the washing of coal gas, which in many gasworks were not treated for the manufacture of ammoniacal salts. These liquors are, however, too weak to bear the cost of transport to any great distance ; on the other hand, it would have been undesirable as well as expensive to convert them into solid ammonium salts, seeing that for use in the manufacture of soda it is free caustic ammonia that is needed. They were led therefore to devise means of con- verting them economically, at the place of production in the gas- works, into a crude product rich enough to bear the cost of carriage. With this object E. Solvay devised a form of continuous still, by which solutions containing 15 per cent, of ammonia could be obtained from ammoniacal gas liquors of 1°*5 to 3° Baume. This apparatus, shown in Fig. 20, is composed of a long horizontal wrought-iron boiler A, part of which is heated by the furnace F. This boiler is divided into a number of compartments, &, &, by the partitions c, c. Each of these contains a vessel ^, which is in communication with the following chamber by a short pipe, so that the liquid can pass from any compartment into the vessel t of the next one, whilst on the other hand the steam and gases pro- duced in any chamber can bubble up through the liquor ia the vessel t in the chamber which follows in the- opposite direction. The boiler being filled to the working level, which is regulated 64 AMMONIA AND ITS COMPOUNDS by the position of the overflow pipe S, the liquor, which has under- gone preliminary heating in the vessel H, enters the first compart- ment of the boiler by the pipe G. The vapours which arrive from the second compartment by the duct D, drive part of this liquor out of the vessel ( into the similar vessel in the next compartment. 6, 6, Compartments, e, c. Partitions. D, E, Ducts by which the vapours passed from each compart- ment through the liquor in the vesse F, Fire-place.- G, Pipe delivering ammoniacal liquor the boiler. — Solvay's Apparatus. H, Tank containing the condensation for I., Regulator for the flow of liquor, M, Float which works the regulator. t, t. Internal vessels, each communicating with the preceding compart- ment. S, Syphon for escape of exhausted liquor when the vapours from the next following compartment pass through it. The liquor thus gradually approaches the fireplace, whilst the vapours travel in the opposite direction, producing a regular extraction of the ammonia. The exhausted liquor finally flows away by the syphon S, whilst the strong ammoniacal vapours, issuing at the other end, pass through the coil in the tank H, being there cooled and condensed whilst heating the fresh ammoniacal liquor. The rate of advance of the liquor through the apparatus depends on the relative areas of the plunging ducts E and the vessels t. The annular space between these should be proportioned to the quantity of liquor and the volume of vapour which it is desired to pass through, and it is to be observed that the advance of the liquid being produced by that of the vapour, the activity of the apparatus is proportional to the heating, and ceases entirely if the fire is extinguished. The steam which is condensed in the coil in the vessel H serves to heat the crude liquor before it enters the boiler. The liquor is passed into the vessel H through a regulator L, controlled by a float M. This float rises or falls as the temperature varies, in such a way that the more the apparatus is heated, and the more steam is produced, the larger is the quantity of liquor admitted. The ammonia gas which escapes from the solution condensed by the coil is arrested by a small acid scrubber, situated above the exit pipe. Solvay's apparatus has been constructed in sizes for treating 12, 18, 24, or 48 cm. of liquor in twenty-four hours, producing ammonia solution of 12 to 17 per cent, strength. The consumption of fuel varies from 25 to 30 kilos, per cm. of liquor treated. In dealing with very weak solutions, the heat from the exhausted liquors can be utilised to warm them. An apparatus with fourteen compartments will treat either 18 cm. of liquor of 1° to l''5 B^., or 15 to 16 cm. of 2°. The residual liquors contain at most 100 to 150 grms. of ammonia per cubic metre. To obtain solutions of 16 to 17 per cent, of ammonia, it is necessary to use liquor of 3° B^. ; weaker liquors will not yield more than 12 to 14 per cent. Gas liquor in which part of the ammonia exists as fixed salts, should be treated with lime after the removal of the volatile salts. With this object the liquors are passed through a vessel containing lime, situated between compartments 7 and 8, but it is impossible to add sufficient lime to decompose the fixed salts completely without risk of overheating the exposed plates of the boiler. The plates of the first compartments are rapidly destroyed by the sulphides in the liquors ; they require to be renewed about every two years. A thorough cleansing must be given every three or four months to remove the tarry and calcareous incrustations, especially in the 5 66 AMMONIA AND ITS COMPOUNDS compartments immediately over the furnace. In the newest patterns the first five compartments are built of plate 10 mm. (f in.) thick ; the remainder are of cast-iron, which resists the action of the sulphides better. The arrangement for passing the vapours through the liquid has also been much simplified, as shown in Fig. 21. The common wall of two compartments, A and B, is pierced with two holes, through one of which, i;, the vapours pass, whilst the other, /, brings the liquor in the opposite direction. In Fig. 21 the part marked 6 is a wrought-iron box open at the top and covering the hole v ; on the other side of the partition is a flattened box d of cast-iron, communicating by the bend E with the compartment C through the opening V. From the positions of the hole -y, and the tops of the boxes h and dy relatively to the level of the liquid in the compartments, it follows that the vapours passing from A into B traverse the boxes and throw up the liquor brought by the pipe E. The liquid flowing continuously from compartment C is thus thrown up in B, and the vapours travel in the opposite direction, as in the arrangement previously described. The construction of this new form of apparatus is simpler and less expensive than that of the older one. Solvay's apparatus may be used for the manufacture of ammonium sulphate or chloride, by passing the vapours from the boiler into the respective acids, and in this case the tank H can still be used as a heater by passing the exhausted liquors from the syphon S through the coil. EXTRACTION OF AMMONIA FROM GAS LIQUOR 67 2. Kuentz's Apparatus. — M. Henry Kuentz has invented and constructed a simple and inexpensive apparatus for the production of concentrated gas liquor, as shown in Fig. 22. The extraction apparatus consists of two wrought-iron boilers, A and B, with an effective capacity of 750 to 1000 litres each, where the lower boiler is set in a furnace. Vapours from this boiler pass through froth separators a and b, then into boiler B via a pipe ending in a shallow cone. Above boiler B there's a second froth separator i, which breaks up the froth and returns it to the boiler by sealed pipe p while vapour passes on to the condensing apparatus. A pipe with stop-cock C allows liquor from B to be run down into A, and waste-cock V draws off exhausted contents of A. Gas liquor is brought to B via pipe D; lime can be added through funnel E. The boilers are equipped with level gauges. Condensation occurs in an oval tube F cooled by water, assisted by a stream from pipe g. Uncondensable gases escape through pipe h into vessel K for observation or purification before being sent to the furnace. Concentrated ammonia solution is drawn off via tap S when H reaches fixed level as shown by gauge-glass. Each operation lasts 2-4 hours and yields solutions of 13-15% ammonia. This apparatus is inexpensive, easy to work, and widely used in gasworks. 3. GrilTveberg's Apparatus. — We have already described the apparatus devised by Griineberg for manufacturing ammonium sulphate from gas liquor. In a modified form this apparatus is equally suitable for producing concentrated ammonia liquor. The arrangement for this purpose is shown in section in Fig. 23. At the top of the distillation column, there's a long pipe E cooled by water-jacket to condense part of the vapour. Remaining vapour is condensed in coil D, forming concentrated ammonia solution which flows into tank E and then into a reservoir. Uncondensable gases go through scrubber H, then to fire grate via pipe p. Crude gas liquor from F passes through covered tank containing coil D, warms up, and goes over to column by curved pipe I, passing through the still as previously described. This apparatus extracts large volumes economically, yielding 12°-14° solutions. It avoids risks of burning out plates when heating tarry liquors with lime, making it easy to operate. A model with a boiler 15 m in diameter and 3 m high treats 10 cm of gas liquor daily.
Key Takeaways
- E. Solvay developed a continuous still to extract ammonia from weak gas liquors economically.
- Kuentz's apparatus is simple and inexpensive, suitable for producing concentrated ammonia liquor.
- GrilTveberg’s modified apparatus can also be used to produce concentrated ammonia liquor efficiently.
Practical Tips
- Utilize the heat from exhausted liquors to warm weak solutions before processing.
- Regular maintenance of equipment is crucial to prevent damage and ensure efficiency.
- Consider using lime to decompose fixed salts in gas liquors containing volatile salts.
Warnings & Risks
- Overheating can cause damage to boiler plates, especially when dealing with tarry liquors.
- Incomplete decomposition of fixed salts may lead to overheating risks.
- Regular cleaning is necessary to prevent incrustations and maintain efficiency.
Modern Application
While the specific apparatus described in this chapter are historical, the principles of efficient resource extraction and utilization remain relevant. Modern survival scenarios can benefit from understanding these techniques for recycling and repurposing industrial byproducts, such as using ammonia from gas liquors for various applications like fertilizer or cleaning agents.
Frequently Asked Questions
Q: What is the main purpose of E. Solvay's continuous still?
The main purpose of E. Solvay's continuous still was to extract ammonia economically from weak gas liquors, making it feasible to use these liquors for industrial purposes.
Q: How does Kuentz’s apparatus differ from Solvay's in terms of operation?
Kuentz’s apparatus operates by passing vapours through froth separators and then into a condensing apparatus, while Solvay's continuous still uses a series of compartments to gradually extract ammonia.
Q: What is the significance of using lime in the extraction process described for gas liquors?
Lime is used to decompose fixed salts in gas liquors containing volatile salts, ensuring that all ammonia can be extracted before the solution becomes too weak or tarry to handle effectively.