Treatment of Wastewater from the Kemerovo Coke-Chemical Plant for Oil Removal by Flotation Using Cationic Surfactants
Abstract Generated abstract
This study addresses the need for preliminary oil removal from wastewater at the Kemerovo Coke-Chemical Plant before biological phenol treatment, especially in view of planned dry coke quenching and discharge requirements. Laboratory flotation experiments were conducted on wastewater containing about 1.25 g/l oil, using the cationic surfactant aminonitroparaffin at plant-relevant pH and temperature. Because flotation alone was ineffective, aminonitroparaffin was tested as an intensifying reagent, and a dosage of 200 mg/l reduced residual oil to 0.08 g/l, within the stated limit for subsequent biological treatment. Analysis of separated and residual oils indicated that flotation preferentially removed the neutral oil fraction, and the authors recommend plant-scale testing of the method.
Full Text
Bulletin of the Tomsk Polytechnic Institute
named after S. M. Kirov, awarded the Order of the October Revolution
and the Order of the Red Banner of Labor
Vol. 234 1974
PURIFICATION OF WASTEWATER FROM THE KEMEROVO COKE AND CHEMICAL PLANT FROM OILS BY FLOTATION USING CATIONIC SURFACTANTS
S. A. BABENKO, L. F. PROSEKOVA, O. I. POPOVA
(Presented by the scientific seminar of the Department of Processes, Machines
and Apparatuses of Chemical Production)
Wastewaters from the Kemerovo Coke and Chemical Plant contain phenols and their derivatives, ammonia, and a considerable quantity of other suspended and dissolved organic and mineral substances. At present this water is used for quenching coke. According to the plant reconstruction plan, dry quenching of coke is envisaged; therefore, deep purification of the wastewater before its discharge into a water body becomes necessary. A reduction in the phenol content in the wastewater is achieved by applying biological treatment, which is effective only after preliminary removal of oils from the wastewater (the limiting oil content is 100 mg/l). At present the oil content in the wastewater after passage through settling tanks and a purification scrubber remains high and reaches 1.25 g/l. Therefore, before biological treatment, a considerable amount of oil must be removed from the wastewater.
An analysis of existing methods for treating wastewater from oils and other nonpolar substances showed the advantage of the flotation method owing to the continuity of the process, high productivity, and ease of introduction into production.
A distinctive feature of the wastewater from the Kemerovo Coke and Chemical Plant is apparently the colloidal solubility of the oil (dilution by a factor of 1925 did not reveal an emulsion); therefore, as our studies showed, flotation treatment of the wastewater did not give the desired results. To intensify the process of purifying wastewater from oils by flotation, the cationic surfactant ANP (aminonitroparaffin), used as a petroleum demulsifier, was employed.
ANP is obtained by nitrating sintin or light paraffin hydrocarbons and subsequently hydrogenating the nitro product. The approximate composition of the reagent ANT-14 corresponds to the formula C₁₄H₂₉NH₂HCl. The content of secondary amines does not exceed 4.5%. ANP is a water-soluble brown liquid consisting of hydrochlorides of primary amines and 10–20% water. The ANP used in the studies had the following characteristics: amine number 13.1 and primary amine content 96.64%. For the experiments, a 3% solution of the reagent was prepared. The procedure for the flotation-treatment experiments consisted in loading the water under study into a laboratory-type “Mekhanobr” flotation machine with a chamber volume of 500 cm³. After addition of the calculated amount of reagent, the water was mixed for 3 min, after which air was supplied and the froth was removed for 2 min. The chamber product was analyzed for oil content. The influence of the amount of reagent on the completeness of purification was studied.
water from oils. The experiments were carried out at pH = 9 and a water temperature of 60–70°C (these parameters correspond to the plant conditions).
Table 1 presents the results of treating wastewater to remove oils by the flotation method using ANP. It can be seen that a reagent consumption of 200 mg/l of water ensures a reduction of oil to acceptable limits. A twofold increase in ANP consumption practically did not improve the process of cleaning the water from oils.
Table 1
Effect of ANP consumption on the degree of purification of wastewater from oil
(initial oil content—1.25 g/l)
| ANP consumption, mg/l | Oil remaining in water, g/l | % purification |
|---|---|---|
| 45 | 0.78 | 38 |
| 60 | 0.45 | 64 |
| 90 | 0.21 | 83 |
| 120 | 0.17 | 87 |
| 150 | 0.12 | 91 |
| 200 | 0.08 | 93 |
| 400 | 0.07 | 92 |
The oils passing into the froth had the following composition: bases—3.58%, carboxylic acids—1.35%, phenols—5.63%, neutral oils—57.3%; while those remaining in the water after flotation were: bases—3.2%, carboxylic acids—15.2%, phenols—32%, neutral oils—28.6%. Comparison of these data indicates that mainly the neutral fraction of the oils passes into the froth.
Thus, cation-active substances of the ANP type can be used to purify wastewater from the Kemerovo Coke and Chemical Plant from oils by the flotation method. For treatment of the water studied, the ANP consumption was 200 mg/l; the oil content in the purified water in this case was 0.08 g/l.
It is proposed that this method of wastewater treatment be tested at the Kemerovo Coke and Chemical Plant.