Master of DonNTU Yuliya Karpovich.Summary

The reduction of fur formation in heatexchange equipment is a paramount problem for technological processes of cokechemical production. At breach of heatexchange process the cooling of coke gas in primary gas coolers becomes worse, which leads to loss of chemical products and extra energy consumption for gas consumption.

Natural waters, which are used as coolling agent in heatexchange equipment, cause the formation of saline scale on surfaces of heating , consisting mainly of carbonate calcium. This is conditioned by disintegration of carbonate acerbity salts while heating of water with loss of carbonic acid and fallout of carbonate calcium in sediment. The intensity of sediment formation depends on temperature of heating and amount of bicarbonates in water.

To prevent carbonate calcium scale formation many different ways of processing the coolling water are practiced on cokechemical enterprises: underoxidation by sulphuric acid; processing by phenol waters, which contain chloride and sulphate of ammonium. At present time for prevention of fur formation in circulating systems of water-supplying the phosphorusorganic compounds are used more and more often. Efficient compound of given class is oxiethilidendiphosphon acid.

For provision of efficient crystallization control of low-soluble salts in water system by oxiethilidendiphosphon acid it is offered to make the preliminary softening of nourisning water. As reagents for water nourishment different materials are recommended: hydrochloric acid, sulfuric acid, sulphate ammonium, chloride ammonium and others. However all these ways do not provide the furless state of working the heatexchange equipment.

It is difficult to prevent the formation of carbonate scale because in conditions of production the technical water, coming to renew the cycles, is characterized by high general (8-15 mg-eg/l) and carbonate (5-7 mg-eg/l) acerbity.

Ammonium water of gascollection cycle is one of the worst unset in phenol sewerage. The high content of organic and mineral admixtures in it makes the work of biochemicalplant (BCP) more difficult. So this water, avoiding BCP, is used to quench the coke.

At interaction of water components with overheated coke bad materials in the form of vapour and products of the destruction of bounded ammonia salts and the other admixtures are thrown into the atmosphere (ammonia, clorous hydrogen, rodanides, cyanides, phenolses and others), the equipment of coke quenching is subjected to intensive corrosion.

Meantime, ammonium water due to presence of mineral and organic compounds in it can be used for stabilization processing of circulating coolling water. Ammonium water presents itself the concentrated solution of clorous ammonium (before 50 g/l), it also contains organic basis, phenolses and others. As a consequence of presence the organic substancies in ammonium water it has the ability to reduce the corrosion activity of water system.

The prevention of carbonate scale formation with the use of mixture of technical and ammonium water is explained basically by proceeding the exchange reaction between bicarbonate calcium and ammonium salts with formation of the chloride calcium. By interaction of bounded ammonium salts with bicarbonate calcium the salts of temporary acerbity are transformed into salts of constant acerbity, which do not crystallize in heatexchange equipment.

At the same time the presence of bounded salts of ammonia in circulating system promotes the dissolution of old carbonate scales.

The estimation of stability of bicarbonate water solutions and determination of technical water processing efficiency by ammonium water was conducted in laboratory conditions. The certain volume of technical water with the addition of ammonium water and without it, was evaporated under 80 С before achievement the necessary multiplicity of evaporation. After that, the system was analysed on the content of calcium ions and magnesium ions, then the amount of calcium, which fallout in sediment was calculated.

The method of the experiment was the following. 400 ml technical water was poured out into several glasses. The content of the first glass was evaporated without any processing. In other glasses the water was beforehand softened by ammonium water in amount 5, 10, 15% from volume of taken technical water.

Picture 1 - Laboratory plant for water stabilization processing research(9 pictures, repeat forever)

# of experiment	evaporation factor	Amount of ammonium water, % from volume of technical water	Fallout (+) Ca, dissolution (-) Ca, mg-eq/l
1	1,8	0	+3,0
2	1,5	5	-2,5
3	1,4	10	-4,7
4	3,7	0	+14,0
5	3,9	5	+4
6	3,8	10	-0,6
7	3,8	15	-2,1

As it is seen from the table, high acerbity of technical water (8 mg-eq/l) has caused intensive fur formation in the first and the fourth glasses (the experiment 1 and 4).

With adding the corresponding volume of ammonium water into technical (the experiments 2,3,6,7) the effect of salt-scales decrease can be observed, which falls at growing of the evaporation factor.

The laboratory researches have confirmed the possibility to use the ammonium water as inhibitor of carbonate salts sediment at observance the optimum concentrations.