Analysis and Discussion on ammoniation operation c

Analysis and Discussion on the ammoniation operation conditions of condensate polishing mixed bed

with the continuous development of power technology and power industry, China's generator units continue to develop towards high parameters and large capacity, so the boiler has higher and higher requirements for feed water quality. In order to ensure the safe operation of the units, the units with subcritical and above parameters in China basically adopt the condensate polishing system to remove various impurities in the condensate and ensure that the feedwater quality meets the requirements

at present, China's condensate polishing devices basically operate in h-oh mode, which is a better process for treating condensate. Using h-oh type mixed bed to treat condensate can make the conductivity of outlet water within 0.1 μ Below s/cm, usually up to 0.06 ~ 0.08 μ S/cm。 But it also removes nh4+ through ion exchange (this nh4+ is added to reduce the corrosion of thermal equipment). Since the amount of NH4OH in condensate is often much larger than that of other impurities, the cation resin exchange capacity of h-oh mixed bed 9 in Beijing alone has more than 100 houses, more than 0% of which are consumed by nh4+, which is very unfavorable, and then NH3 needs to be supplemented in the water supply system, which is not ldquo; I've always wanted to share my life economy with my soul mate. Therefore, in order not to remove nh4+ in condensate and improve the operation economy, it is very necessary to adopt nh4-oh mode for the operation of condensate high-speed mixed bed

1 theoretical analysis of the ammoniation operation conditions of the mixed bed

the conditions required for the ammoniation operation can be estimated according to the ion exchange selectivity coefficient, and the calculation formula is as follows:

by substituting the above data into equations (1), (2), (3) and (4), it can be calculated that na+c5 is required for the effluent of the mixed bed μ g/L,Cl-C5 μ See Table 1 for the conditions to be met by the resin at g/l

from table 1, it can be seen that the purity (i.e. regeneration degree) of cation resin is very high, and the general requirement is that BASF: expand the patent cooperation of high nickel production capacity licensing by more than 99.5%, which requires that the cation in the anion (referring to the cation resin mixed in the anion resin) is less than 0.5% during the separation of resin; The regeneration degree of anion resin is only required to be more than 95%, that is, Yang Zhongyin (referring to the anion resin mixed in Yang resin) is less than 5%. Therefore, for the ammonium mixed bed, it is much more important to ensure the purity of anion resin during the separation of mixed resin

2 mole fraction of RNA in the actual exchange process

in practical application, when the regeneration degree of resin meets the requirements of Table 1 above, it is also necessary to consider the ratio of sodium cation resin and NH4 cation resin produced due to resin ion exchange reaction when the mixed bed runs to nh4+ leakage. This is estimated below, and the formula is as follows:

when the above data is substituted into formula (5), the average mass concentration of na+ in the incoming water can be calculated to be 1 ~ 5 μ G/l, when the average pH of the incoming water is 8.8 ~ 9.6, when the effluent of the mixed bed begins to leak nh4+, the mole fraction of sodium cation resin produced by ion exchange in the total cation resin is shown in Table 2

similarly, the ratio of CL anion resin and oh anion resin produced by resin ion exchange reaction can be calculated when the mixed bed runs to nh4+ leakage. In fact, under the condition that the condenser does not leak, the content of cl- in condensate is always very low (less than 1 μ G/l), and [rcl]/([roh]+[rcl]) can always meet the requirements of Table 1, which will not be detailed here

3 conditions for ammoniation operation of mixed bed

from table 1 and table 2, it can be basically concluded that when the mixed bed operates to nh4+ leakage, it will continue to be the conditions for ammoniation mixed bed operation

(1) the separation of mixed resin before regeneration should be complete. To ensure that Yin in Yang is less than 0.5%, and Yang in Yin is less than 5%, so as to prevent cross contamination

(2) before ammoniation of mixed bed, control the average pH of condensed water (water inlet) to be above 9.4. If the concentration of na+ in condensed water is lower than 2 μ G/l, the pH can be relaxed to above 9.2, which can be achieved by adding ammonia to the feed water

(3) the average na+ mass concentration of condensation level should be less than 5 μ G/l, preferably 3 μ Below g/l

(4) after the ammoniation operation of the mixed bed, the pH of condensate should be kept low. It can be seen from table 1 that it is best to keep the pH of condensate below 9.4, which has also been proved in the actual operation of relevant power plants

(5) use hydrogen ion conductivity meter and sodium ion concentration meter to jointly monitor the end point of mixed bed operation, with conductivity ≤ 0.2 μ S/cm,Na+≤5 μ g/L。 Na+ ≤ 5 in actual operation μ G/l is difficult to achieve and can be appropriately relaxed to 10 μ g/L。

(6) the quality of regenerant should be high, especially the quality of alkali. It is required that the NaCl content in alkali should be less than 50mg/L. If the chlorine radical in the alkali is high, some anion resins will be regenerated into chlorine type during regeneration, which will lead to the leakage and failure of chlorine radical after the ammoniation operation of the mixed bed

(7) after resin regeneration and before mixing, adequate rinsing should be carried out to effectively avoid the occurrence of "mixing pollution"

(8) the condenser never leaks during the operation of the mixed bed. Once the condenser leaks, the polishing mixed bed should operate in h-oh mode