Pulp and Paper Multiple Choice Questions on “Kraft Liquor Calculations”.
1. The _________ is the sum of all of the Na salts in the liquors (as Na2O) that contribute to AA in the kraft cycle, specifically NaOH, Na2S, Na2CO3, and Na2O.
a) Base
b) Total alkali
c) Total acid
d) Buffer
Answer: b
Clarification: The total alkali’s the sum of all of the Na salts in the liquors (as Na2O) that are capable of being converted to AA in the kraft cycle, specifically NaOH, Na2S, Na2CO3, and Na2O.
2. _________ is the sum of all of the bases in the white liquor that could be titrated with strong acid.
a) Total titratable alkali
b) Active alkali
c) Total chemical
d) Total alkali
Answer: a
Clarification: T.T.A. is the sum of all of the bases in the white liquor that could be titrated with strong acid. It’s considered as NaOH, Na2S, and Na2CO3 (as Na2O), although small amounts of Na2CO3.
3. The sum of the active ingredients in the pulping process is called active alkali.
a) True
b) False
Answer: a
Clarification: White liquor’s a strongly alkaline sol. mainly of NaOH and Na2S. It’s utilized in the first stage of the Kraft process in which lignin and hemicellulose are separated from cellulose fiber for the production of pulp.
4. _________ is the sum of Na chemicals that will produce OH– during kraft pulping.
a) Active akali
b) Effective alkali
c) Causticity
d) Sulfidity
Answer: b
Clarification: NaOH is completely ionized and for every 2 sodium atoms of Na2S, there’ll be one OH– produced.
5. In the _________ sulfidity’s the ratio of Na2S to the active alkali, expressed as a %.
a) Green liquor
b) Red liquor
c) White liquor
d) Black liquor
Answer: c
Clarification: Generally, a mill runs in the vicinity of 25 to 30% sulfidity, depending largely on the wood species pulped. Sulfidity inc. the rate of de-lignification, which occurs by nucleophilic action of the hydrosulfide anion (H.S.) and appears to protect cellulose against degradation.
6. The _________ is the ratio of NaOH to active alkali, expressed as a %.
a) Active alkali
b) Liquor to wood ratio
c) Causticity
d) Sulfidity
Answer: c
Clarification: The causticity’s the ratio of NaOH to active alkali, depicted as a percentage; therefore, causticity + sulfidity = 100%. The term sulfidity’s utilizes much more than the term causticity, and both give the same information.
7. The _________ is the ratio of NaOH to NaOH and Na2CO3.
a) Sulfidity
b) Causticity
c) Causticizing efficiency
d) Reduction efficiency
Answer: c
Clarification: This is a calculation of how efficient causticizing is; it represents the percentage of the Na2CO3 from the recovery boiler that is converted back into useful NaOH cooking chemical. A value of 77-80% is typical.
8. The ratio of Na2S to the sum of Na2S and Na2SO4 in green liquor expressed as a percentage. What’s the name of the topic?
a) Sulfidity
b) Causticity
c) Causticizing efficiency
d) Reduction efficiency
Answer: d
Clarification: The reduction efficiency’s the ratio of Na2S to the sum of Na2S and Na2SO4 in green liquor expressed as a %. This’ a calc. of the reduction efficiency in the recovery boiler. This value should be high, as 95 percent, and is not routinely measured in the mill.
9. Derive the conversion factor of 0.775 utilized to express the weight of NaOH on an Na2O basis.
a) 0.775 g Na2O
b) 3.254 g Na2O
c) 15.775 g Na2O
d) 0.456 g Na2O
Answer: a
Clarification: 1st, the molar relationship b/w these 2 species is expressed.
2 NaOH andbarr; Na2O + H2O
Gravimetric factor’s determined as follows:
1g NaOH X 1 mol NaOH(40g NaOH)-1 x 1 mol Na2O(2 mol NaOH)-1 x 62g Na2O(1 mol Na2O)-1 = 0.775g Na2O.
10. Fill in the blank.
________ = {(NaOH) / (NaOH + Na2CO3)} x 100%
a) Na2CO3
b) NaOH
c) CO3
d) Na
Answer: b
Clarification: The causticizing efficiency is the ratio of NaOH to NaOH and Na2CO3. This’s a calculation of how efficient causticizing is; it represents the percentage of the Na2CO3 from the recovery boiler that’s converted back into useful NaOH cooking chemical. A value of 77 to 80% is typical.
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