for Alkali Concentration Measurement of White and Cooking Liquor
The EMCO alkali sensor type 821 and the EMCO Analyzer type 580 calculate the concentration
of white and cooking liquor in the pulp and paper industry by measuring the conductivity of
In the digester in a pulp mill the wood chips are cooked with white liquor in order to remove
the lignin and other unwanted substances. The lignin is the product which bonds the wood
The white liqour is a chemical mixture of mainly sodium hydroxide (NaOH) and
sodium sulphide (Na2S).
NaOH and Na2S are significantly much more conductive than the rest of the components in
the white liquor. Therefore the conductivity can represent the effective Alkali (EA) and
active Alkali (AA) concentration.
The sensors are designed to be installed directly into the feed circulations as it supplies
the operator with a real time measurement and optimum conditions to fine tune the alkali
and temperature in the process.
Sluice mounting or retractable under pressure types are available, see bottom of page for
brochure on series 822.
Alternatively a complete bypass solution is available which includes additional items
such as main pipe spool piece, bypass measuring pipe, valves, restriction orifice plate
and cooler etc.
All items will be provided and manufactured by EMCO Controls.
The sensor element has a 4 electrode design for higher accuracy over the 2 electrode design.
The sensor element has an accurate temperature sensor with low response time for
fast temperature compensation.
The sensor is to be mounted in a pipe size larger than 200 mm.
The cable to connect to the Analyzer is especially selected to ensure high accuracy
and long distance between sensor and analyzer. The cable is a part of the supply
of the sensor.
Our many years in the field of instrument design guarantees a roughed design,
but still allows the possibility to solve customers´ special requirements.
The sensor is extremely resistant to wear.
The disk type design ensures no risk of scaling (product build up).
The unique sensor design eliminates risk of catching air bubbles which would influence
PRINCIPLE OF MEASUREMENT
The conductivity is equal to the conductance of the liquid times the cell constant.
The conductance is the reciprocal of the electrical resistance of the liquid measured.
The cell constant is equal to the distance between the electrodes divided by the
effective area of the electrodes.
Measuring range : 0- 2000 mS/cm
Process connection : Flange according to ANSI B 16.5, EN 1092-1 or DIN
Pressure ratings : 300 lbs or PN 40
Sizes : 1½”, 2”, DN 40, DN 50.
Pressure max. : 30 bar
Temperature max. : 180°C
Material. sensor body : AISI 316, 22 Cr Duplex
Material. electrodes : AISI 316, 22 Cr Duplex
Material, electrode support : PTFE
Insertion length : 286 mm
Temperature element : Pt1000 Class A IEC 751
Cell constant : Individually determined, marked on sensor
Accuracy : better than 3 % (2 % per decade)
Protection : IP 65
Electrical connection : connector, 9 pin
Cable lengths : 3 m, 5 m, 10 m, 20 m, 30 m.
Suitable Analyzer : model 580