Membrane treatment of alkaline bleaching effluent on a kraft pulp mill

32 Pages·2015·1.23 MB·English

FEDERAL UNIVERSITY OF VIÇOSA
DEPARTMENT OF FOREST ENGINEERING
LABORATORY OF PULP AND PAPER
Membrane treatment of alkaline
bleaching effluent on a kraft pulp mill
Rafael Quezada, Claudio Mudadu Silva, Leif Nilsson
Christian Hoffstedt and Niklas Berling
Outline

• Introduction
• Objectives
• Results
– Membrane treatment of alkaline bleaching
effluent
– Effects of the (EPO) membrane filtration on the
effluent treatment plant
– Membrane permeate recycling to the bleaching
plant
– Membrane retentate send to black liquor
evaporation
• Conclusions
Effluent generation
1,3 – 6,0 4 – 10 15 – 30 4 – 7
DRYNG
COOKING BLEACHING
WOODYARD
MACHINE
0,5 – 2,0
EVAPORATORS
RECOVERY
1,0 – 2,0
BOILER
Water consumption

Bleaching area: 45.000 m3/d
Total: 65.000 m3/d
CAUSTICIZING 2,0 – 4,0
Volume (m3/adt)
Membrane treatment
Module
(EPO) filtrate Membrane Retentate
Permeate
Bleaching sequence
D (EPO) D D
NaOH

D
Pre–O
2
Pulp
(EPO)

D
D

ClO
2
Acid effluent

(EPO) filtrate

Alkaline
effluent
Objectives

Evaluate the membrane treatment of (EPO) filtrates from a
kraft pulp mill

Specific objectives

a) Compare three configurations of membrane to treat alkaline (EPO)
filtrate of a kraft pulp mill using pilot plants and determine the best
operation conditions;

b) Study the effect of the (EPO) filtrate membrane treatment on the
effluent treatment plant;

c) Evaluate the feasibility of recycling of the UF permeate within the
bleaching plant;

d) Evaluate the feasibility to send the UF retentate to the black liquor
evaporation sector
Membrane treatment of
alkaline bleaching effluent
Membrane treatment – Experimental set-up
Membrane configuration
selection
(UF, UF + NF, NF)
Optimal condition
determination
Long-term operation
Membrane treatment – Pilot plants
Membrane treatment

• The nanofiltration membranes require a pre-
treatment to reduce temperature and neutralize pH;

• In order to select the best option it was considered
not only the selectivity but also the costs and
operation simplicity;

• The selected configuration was ultrafiltration;

• The best condition for higher permeate flux (over
200 L/m2h) was 3,0 m/s of cross-flow velocity and 7
bar of TMP, for a COD removal and color of 58% and
91%, respectively.