Paper Manufacturing: Kraft (Sulfate) Pulping

Abstracted from Washington State Air Toxic Sources
and Emission Estimation Methods

Pulping is the term used for the process which separates wood fibers. Chemical pulping, dissolving the lignin in the wood to create a pulp, is the most commonly used pulping process. Chemical pulping creates higher sheet strength than mechanical pulping; however, yields 40 to 50 percent pulp, where mechanical pulping yields 95 percent pulp.

The two main types of chemical pulping are the more common sulfate pulping (most commonly known as Kraft pulping) and sulfite pulping. Kraft pulping accommodates a variety of tree species, recovers and reuses all pulping chemicals, and creates a paper with a higher sheet strength. Sulfite pulp, however, is easier to bleach, yields more bleached pulp, and is easier to refine for papermaking. The major difference between the two types of chemical pulping is the types of chemicals used to dissolve the lignin.

The Kraft process was developed in Germany in 1879 and was first applied to a Swedish mill in 1885. The resulting paper was much stronger than any paper previously made, and therefore the process was named “Kraft”, (German and Swedish for “strength”). Kraft pulping creates dark brown paper which is used for boxes, paper bags, and wrapping paper. Kraft pulp can also be used for writing paper and paperboard when bleached, and for diapers when fluffed.

The three main steps involved in Kraft pulping are:

1. Digestion: wood chips are cooked
2. Washing: black liquor is separated from the pulp
3. Chemical recovery: chemicals are recovered from the black liquor for reuse

Description of Process

• Digestion 

The first step in pulping wood is to “cook” the wood chips. A digester, heated by steam, “cooks” the wood chips in white liquor (a mix of sodium hydroxide (NaOH) and sodium sulfide (Na2S)) until done. The cooking process dissolves most of the lignin and only some of the hemicellulose , leaving mostly cellulose to hold the fibers together. The digester system may be a batch or a continuous process.

Relief gases are vented continuously from the digester, which helps remove air and other non- condensable gases and reduce the pressure at blow, when the pulp is discharged to the blow tank. After the cooking process, the pulp and black liquor (the chemical mix left after the cooking process) are discharged to a blow tank.

By-products can be recovered from the digestion process. For example, turpentine distills with water out of the blow tank and the evaporators and is separated to be used. The resin acids and fatty acids dissolved from the wood form sodium soaps which are skimmed off the black liquor from storage tanks, evaporators, and black liquor oxidation tanks, and then acidified with sulfuric acid to form tall oil.

Before the washing process, the pulp is usually sent to deknotters, screens used to remove knots (large pieces of fiber not completely broken down in the digester).

• Brownstock Washing 

Pulp from the blow tank and deknotter is washed with water in a process commonly called brownstock washing. Washing removes weak black liquor from the pulp which is sent to the chemical recovery process. This also prevents contamination during subsequent processing steps. Types of washers used include rotary vacuum washer (most common type of washer), diffusion washers, rotary pressure washers, horizontal belt washers, wash press, and dilution/extraction.

All the washer types use water (fresh or recycled) and are usually placed in series to achieve higher removal efficiency.

The rinsed pulp is screened for oversize particles and then excess water is removed. This is done in a gravity thickener (more commonly known as a decker).

• Chemical Recovery 

The reason Kraft pulping is economically successful is that the used cooking liquor can be recovered and reused in the chemical recovery process.

The first step in recovering the chemicals from the black liquor is evaporation. This removes excess water from the black liquor and maximizes the fuel value for the recovery furnace.

There are two types of evaporators generally used in the chemical recovery process: direct (DCE) and indirect (NDCE) contact evaporators. Some types of DCE include the multiple-effect evaporator (most common), flash evaporation and thermocompressor evaporation. DCE use heat from direct contact with the recovery furnace flue gases, while NDCE uses indirect contact.

Black liquor oxidation is needed after DCE, but not after NDCE. After DCE, the black liquor is normally oxidized with air to control the sulfide level and prevent the release of odorous compounds. This is done by countercurrently passing the black liquor through an air stream using a porous diffuser, sieve tray tower, packed tower or agitated air sparge. The oxidation reaction converts sodium sulfide to sodium thiosulfate.

After NDCE or black liquor oxidation, the black liquor is then forced through spray nozzles into the recovery furnace, where it is burned providing heat to generate steam. This also conserves the inorganic chemicals, which create a molten smelt on the floor of the furnace.

The molten smelt, composed of sodium sulfide and sodium carbonate, is drained from the recovery furnace hearth through smelt spouts. In a smelt dissolving tank, the smelt is quenched with water, producing green liquor.

Sodium carbonate from the smelt is then converted to sodium hydroxide in the causticizer by adding calcium hydroxide. The calcium carbonate resulting from the reaction precipitates from the solution and is collected and sent to the lime kiln where it is converted to lime (calcium oxide). The calcium oxide is then slaked to produce calcium hydroxide for reuse in the causticizer.

Overview of Chemical Recovery Processes in Pulp & Paper Mills

Figure 1

The kraft process is the dominant pulping process in the United States, accounting for approximately 85 percent of all domestic pulp production. The soda pulping process is similar to the kraft process, except that soda pulping is a non-sulfur process. One reason why the kraft process dominates the paper industry is because of the ability of the kraft chemical recovery process to recover approximately 95 percent of the pulping chemicals and at the same time produce energy in the form of steam. Other reasons for the dominance of the kraft process include its ability to handle a wide variety of wood species and the superior strength of its pulp.

The production of kraft and soda paper products from wood can be divided into three process areas:

1. Pulping of wood chips
2. Chemical recovery
3. Product forming (includes bleaching)

Figure 2

The relationship of the chemical recovery cycle to the pulping and product forming processes is shown in Figure 1. Process flow diagrams of the chemical recovery area at kraft and soda pulp mills are shown in Figures 1 and 2, respectively.

The purpose of the chemical recovery cycle is to recover cooking liquor chemicals from spent
cooking liquor. The process involves concentrating black liquor, combusting organic compounds, reducing inorganic compounds, and reconstituting cooking liquor.

Cooking liquor, which is referred to as "white liquor, is an aqueous solution of sodium hydroxide (Na01) and sodium sulfide (Na2S) that is used in the pulping area of the mill. In the pulping process, white liquor is introduced with wood chips into digesters, where the wood chips are "cooked" under pressure. The contents of the digester are then discharged to a blow tank, where the softened chips are disintegrated into fibers or "pulp. The pulp and spent cooking liquor are subsequently separated in a series of brown stock washers: Spent cooking liquor, referred to as "weak black liquor, from the brown stock washers is routed to the chemical recovery area. Weak black liquor is a dilute solution (approximately 12 to 15 percent solids) of wood lignins, organic materials, oxidized inorganic compounds (sodium sulfate (Na2SO4), sodium carbonate (Na2003)), and white liquor (Na2S and Na0H).

In the chemical recovery cycle, weak black liquor is first directed through a series of multiple-effect evaporators (MEE's) to increase the solids content to about 50 percent. The "strong. (or "heavy") black liquor from the MEE's is then either oxidized in the BLO system if it is further concentrated in a DCE or routed directly to a concentrator (NDCE). Oxidation of the black liquor prior to evaporation in a DCE reduces emissions of TRS compounds, which are stripped from the black liquor in the DCE when it contacts hot flue gases from the recovery furnace. The solids content of the black liquor following the final evaporator/concentrator typically averages 65 to 68 percent.

Concentrated black liquor is sprayed into the recovery furnace, where organic compounds are combusted, and the Na2SO4 is reduced to Na2S. The black liquor burned in the recovery furnace has a high energy content (13,500 to 15,400 kilojoules per kilogram (kJ/kg) of dry solids (5,800 to 6,600 British thermal units per pound {Btu/lb} of dry solids)), which is recovered as steam for process requirements, such as cooking wood chips, heating and evaporating black liquor, preheating combustion air, and drying the pulp or paper products. Particulate matter (PM) (primarily Na2SO4) exiting the furnace with the hot flue gases is collected in an electrostatic precipitator (ESP) and added to the black liquor to be fired in the recovery furnace. Additional makeup Na2SO4, or "saltcake," may also be added to the black liquor prior to firing.

Molten inorganic salts, referred to as "smelt," collect in a char bed at the bottom of the furnace. Smelt is drawn off and  dissolved in weak wash water in the SDT to form a solution of carbonate salts called "green liquor," which is primarily Na2S and Na2CO3. Green liquor also contains insoluble unburned carbon and inorganic Impurities, called dregs, which are removed in a series of clarification tanks.

Decanted green liquor is transferred to the causticizing area, where the Na2CO3 is converted to NaOH by the addition of lime (calcium oxide [Ca0]). The green liquor is first transferred to a slaker tank, where Ca0 from the lime kiln reacts with water to form calcium hydroxide (Ca(OH)2). From the slake, liquor flows through a series of agitated tanks, referred to as causticizers, that allow the causticizing reaction to go to completion (i.e., Ca(OH)2 reacts with Na2CO3 to form NaOH and CaCO3).

The causticizing product is then routed to the white liquor clarifier, which removes CaCO3 precipitate, referred to as "lime mud." The lime mud, along with dregs from the green liquor clarifier, is washed in the mud washer to remove the last traces of sodium. The mud from the mud washer is then dried and calcined in a lime kiln to produce "reburned" lime, which is reintroduced to the slaker. The mud washer filtrate, known as weak wash, is used in the SDT to dissolve recovery furnace smelt. The white liquor (NaOH and Na2S) from the clarifier is recycled to the digesters in the pulping area of the mill.

At about 7 percent of kraft mills, neutral sulfite semi-chemical (NSSC) pulping is also practiced. The NSSC process involves pulping wood chips in a solution of sodium sulfite and sodium bicarbonate, followed by mechanical de-fibrating. The NSSC and kraft processes often overlap in the chemical recovery loop, when the spent NSSC liquor, referred to as "pink liquor," is mixed with kraft black liquor and burned in the recovery furnace. In such cases, the NSSC chemicals replace most or all of the makeup chemicals. For Federal regulatory purposes, if the weight percentage of pink liquor solids exceeds 7 percent of the total mixture of solids fired and the sulfidity of the resultant green liquor exceeds 28 percent, the recovery furnace is classified as a "cross-recovery furnace.'" Because the pink liquor adds additional sulfur to the black liquor, TRS emissions from cross recovery furnaces tend to be higher than from straight kraft black liquor recovery furnaces.

Industrial Refractometers in Action: Pulp & Paper Mill

This video below highlights various applications for inline refractometers in a pulp and paper mill.

The Electron Machine Corporation pioneered the use of refractometers to accurately measure black liquor dissolved solids nearly 50 years ago. Our long history with this application has resulted in numerous design features that specifically address problems associated with this harsh process measurement. Electron Machine refractometers have been accurately measuring green liquor solids in the paper industry for more than 30 years.

For more information visit http://www.electronmachine.com or call 352-669-3101.

Chemical Recovery in Black Liquor Processing for Pulp and Paper Production

Pulp and paper mill.

For economic and environmental reasons, pulp mills employ chemical recovery processes to reclaim spent cooking chemicals from the pulping process. At kraft and soda pulp mills, spent cooking liquor (referred to as weak black liquor), from the brown stock washers is routed to the chemical recovery area.

The chemical recovery process involves concentrating weak black liquor, combusting organic compounds, reducing inorganic compounds, and reconstituting the cooking liquor.

Residual weak black liquor from the pulping process is a dilute solution (approximately 12 to 15 percent solids) of wood lignin, organic materials, oxidized inorganic compounds (Na2SO4, Na2CO3), and white liquor (Na2S and NaOH). The weak black liquor is first directed through a series of multiple-effect evaporators to increase the solids content to about 50 percent to form “strong black liquor.”

Monitoring percent solids in black liquor
is an important part of chemical recovery.

The strong black liquor from the multiple-effect evaporator system is either oxidized in the black liquor oxidation system, or routed directly to a non-direct contact evaporator (also called a concentrator). Oxidation of the black liquor prior to evaporation in a direct contact evaporator reduces emissions of odorous total reduced sulfur compounds. 

The solids content of the black liquor following the final evaporator/ concentrator typically averages 65 to 68 percent. The soda chemical recovery process is similar to the kraft process, except that the soda process does not require black liquor oxidation systems, since it is a non-sulfur process that does not result in total reduced sulfur emissions.

The concentrated black liquor is then sprayed into the recovery furnace, where organic compounds are combusted, and the Na2SO4 is reduced to Na2S. The black liquor burned in the recovery furnace has a high energy content which is recovered as steam for process requirements, such as cooking wood chips, heating and evaporating black liquor, preheating combustion air, and drying the pulp or paper products. 

The process steam from the recovery furnace is often supplemented with fossil fuel-fired and/or wood-fired power boilers. Particulate matter (primarily Na2SO4) exiting the furnace with the hot flue gases is collected in an electrostatic precipitator and added to the black liquor to be fired in the recovery furnace.

Refractometer for black liquor measurement.

The process of chemical recovery must be carefully managed. Process variables such as temperature, pressure, flow and level require robust instruments to ensure safety and accuracy. The measurement of black liquor solids content has relied upon the use of industrial inline refractometers for many decades. The Electron Machine Corporation, with it's ruggedly designed MPR E-Scan,  has established itself as the leader in this process. Incorporating a ruggedly designed sensing head with a 2205 S/S prism holder, sapphire prism, LED light source, and very sturdy electronics, the Electron Machine device delivers on it's claim as the "world's most rugged process refractometer".  Since the refractometer is specifically designed for the very harsh environment of a pulp mill, it promises years of low-maintenance and very reliable operation. 

For more information about inline process refractometers for black liquor processes visit this link or contact Electron Machine at 352-669-3101. 

Refractometers for Pulp and Paper Processing

The Electron Machine MPR E-Scan has numerous applications in the paper industry. The most common applications are on black liquor and green liquor. Electron Machine Corporation pioneered the use of refractometers to accurately measure black liquor dissolved solids nearly 50 years ago.

Black Liquor is the waste product from the process of digesting pulpwood into paper pulp by removing various elements to free the cellulose fibers. Electron Machine's long history with this application has resulted in numerous design features that specifically address problems associated with this harsh process measurement.

Green liquor is the dissolved concentration of sodium sulfide, sodium carbonate, and other compounds from the recovery boiler in the paper making process.  Electron Machine Corporation has been actively refining the use of refractometers for measuring green liquor density for over 30 years. The current system uses the MPR E-Scan refractometer combined with heated high-pressure water for cleaning. The resulting combination provides an effective removal of optical coatings by reducing thermal changes, minimizing maintenance to allow for a reliable measurement source for on-line automatic control.

The MDS Monitor Divert System is a BLRBAC compliant Black Liquor solids monitoring system designed specifically for Black Liquor recovery boilers. The MDS Monitor Divert System consists of two completely independent MPR E-Scan Hybrid-Digital refractometers with a separate monitor console that supervises the proper operation of each refractometer. The monitor constantly insures that all parameters remain within operational limits and applies the proper divert or alarm actions should a fault or low solids liquor be detected. A built-in printer records all actions with a date and time stamp. The entire system is designed to be user friendly with large daylight-readable color displays and an intuitive menu-driven interface.

The MPR E-Scan also gives paper companies the ability to accurately control the washing line, by detecting changes in the total dissolved solids coming off the washers. This precise measurement allows effective control of the fresh water flow to the washers, reducing excessive water usage. Combining the measurement with data- analysis tools, a company can monitor inefficiencies in the washing line and evaluate the washing results. Allowing improvements in washing efficiency and overall reduction in water. The MPR E- Scan will reduce the overall time needed to meet target dilution. With near instant readings of black liquor concentration and temperature, the instrument removes the reliance on offline testing. 

For more information, visit http://www.electronmachine.com or call 352-669-3101.

Industrial Refractometers in Brownstock Washing

Pulp and paper mill.

In pulp and paper production, brown stock washers are used to recover cooking chemicals from pulp production and are critical for maximizing chemical recovery which impacts the financial success and environmental compliance of a pulp mill.

The purpose of brownstock washing is to remove soluble matter from the pulp while using the least amount of water. Efficient washing improves the recovery of cooking chemicals, reduces the use of chemicals during bleaching, increase pulp quality and helps reduce deposit buildup. By utilizing a refractometer to measure the black liquor solids in the feed and outlet stock lines, and the incoming and outgoing filtrate lines, a paper company can experience increased control and cost savings.

The Electron Machine MPR E-Scan gives paper companies the ability to accurately control the washing line, by detecting changes in the total dissolved solids coming off the washers. This precise measurement allows effective control of the fresh water flow to the washers, reducing excessive water usage.

Combining the measurement with data analysis tools, a company can monitor inefficiencies in the washing line and evaluate the washing results. Allowing improvements in washing efficiency and overall reduction in water. The MPR E- Scan will reduce the overall time needed to meet target dilution. With near instant readings of black liquor concentration and temperature, the instrument removes the reliance on offline testing.

The MPR E-Scan is constructed of various alloys to ensure a long service life in a harsh chemical environment. With our customer pipeline adapters, the instruments can be implemented into any process. Due to the unique measurement principle, the instrument's readings are unaffected by bubbles, particles, fibers, color, flow, pressure or vibration. By utilizing the instrument to control and monitor the brownstock washing, paper companies can guarantee that proper dilution was met and maintained.

Electron Machine MPR E-Scan

KEY BENEFITS

• Increased washing efficiency
• Continuous accurate control of dilution factor
• Consistent pulp quality Increased evaporator efficiency
• Reduced wash loss and decrease wash water
• Error and Warning light indications Reduced time for correct wash concentration
• Continuous temperature readings 

Learn more about industrial refractometers and their application in the pulp and paper process by visiting the Electron Machine website at http://electronmachine.com or by calling 352-669-3101.

A BLRBAC Compliant Monitoring System Designed Specifically for Black Liquor Recovery Boilers

MDS Monitor Divert System

The Electron Machine Corporation manufactures a BLRBAC compliant Black Liquor solids monitoring system designed specifically for Black Liquor Recovery Boilers.

The Black Liquor Recovery Boiler Advisory Committee is a group that exists for the purpose of generating safety procedures and guidelines that govern the operation of Black Liquor Recovery Boilers.  The BLRBAC was formed in 1961 by several groups of concerned professionals that had become alarmed by the number of Black Liquor Recovery Boiler explosions. 

The MDS Monitor Divert System consists of two completely independent MPR E-Scan Hybrid-Digital refractometers with a separate monitor console that supervises the proper operation of each refractometer. The monitor constantly insures that all parameters remain within operational limits and applies the proper divert or alarm actions should a fault or low solids liquor be detected. A built-in printer records all actions with a date and time stamp. The entire system is designed to be user friendly with large daylight-readable color displays and an intuitive menu-driven interface.

Isolation Valves are also required to meet the BLRBAC guidelines and allow the refractometer sensing heads to be isolated from an active pipeline should maintenance be needed. The system closely monitors the position of these isolation valves to verify that the refractometers are in service.

All functions of the MDS Monitor Divert System are automatic. For example, should a refractometer fault occur the unit is electronically removed from service and an alarm is activated. Simultaneously the output signal is driven low to warn the operator to disregard this reading. The monitor system then isolates, displays the fault and provides a hard copy record on the built-in printer. Liquor diversion is now controlled by the refractometer in service.

• Intelligent purge function- ensures the proper cleaning and extends prism life 
• Divert trending - provides an actual time left before a diversion when liquor solids are declining 
• Password protection- to protect critical software areas

The MDS Monitor Divert System is pre-wired and mounted on a panel for easy installation. All customer connections are made to a single terminal strip. Standard output is a 4-20mA for liquor concentration with relay contacts for liquor divert, alarms, and system error indicators. A remote divert input is also available. The system can be provided in an optional stainless steel enclosure with either a vortex-cooler or fan ventilation depending on the specified mounting location.

For more information on the BLRBAC visit here.

For more information on the MDS Monitor Divert System visit here.

RSP Remote Status Panel for Process Refractometer

Electron Machine RSP Remote Status Panel for Process Refractometer from Electron Machine Corporation

Industrial Inline Refractometer for Green Liquor Density in Pulp & Paper Plant

Electron Machine Corporation has been actively refining the use of refractometers for measuring green liquor density for over 30 years. Their incremental efforts in this application has led to the current combination using the MPR E-Scan with their high pressure cleaner (HPC) adapter supplied with heated demineralized water. The removable nozzle provides for easy maintenance. This system ensures an accurate measurement in these difficult scaling conditions.

Industrial Inline Refractometer for Green Liquor Density in Pulp & Paper Plant from Electron Machine Corporation

The World's Most Rugged Inline Process Refractometers

Electron Machine manufactures the world's most rugged industrial, in-line refractometers used in pulp & paper processing, chemical production, and food and beverage processing.

The company is renowned for manufacturing industrial inline refractometers that hold up to the rigorous environments and the steady demands in these applications. These refractometers are built to withstand the most harsh conditions while delivering reliable and consistent readings and providing safe, reliable, and accurate process measurement and control.

Electron Machine inline refractometers are used in numerous applications in the paper industry such as black liquor, and green liquor sensing; in the food industry to detect sugar levels and properties of jams juices, beverages, and dairy product; and in the chemical industry to measure the strength of a chemical when diluted with water or another chemical.

For more information, visit http://www.electronmachine.com.

Inline Refractometers Tough Enough for Paper Plant Black and Green Liquor Lines

Refractometer and HPC Adapter
with High Pressure Purge System

It's said the only thing a pulp and paper plant doesn't reuse is the "shade the building casts". The processes used in the production of pulp and paper are very efficient when you consider the reuse of energy and by-products. The efficiency comes at a cost though - through very hostile atmospheres and demanding operating conditions for process equipment.

For example, the "kraft process" (also known as the sulfate process) is the method to convert wood chips into pulp and then to cellulose fibers. This is done by mixing the wood chips with sodium hydroxide and sodium sulphate, soaking, cooking and processing.

Here's a very basic explanation of the kraft process. Wood chips are soaked and processed in sodium hydroxide and sodium sulphate mixture known as "white liquor". After the wood chips are impregnated with white liquor, they are then cooked in digesters to break the wood down into cellulose. The solid pulp is then separated and the remaining fluid is referred to as "black liquor". Black liquor is further processed to remove solids and chemicals which are to be re-used in the pulping process. One of the final by-products is "green liquor" which contains sodium carbonate and sodium sulfide and is then reacted with lime to regenerate more white liquor.

All of these steps expose instruments, process equipment, piping, and valves to very tough environments. Electron Machine Corporation, a manufacturer of extremely rugged inline process refractometers, has been actively refining the use of refractometers for measuring green and black liquor density for over 30 years.

The scaling associated with these applications results in an optical coating on the refractometer sensing head. If this scaling can be controlled to allow an acceptable duration of on-line measurement, and then effectively removed when coating occurs, the accuracy of the refractometer can be fully utilized with minimal maintenance. The primary issue then becomes the maintenance required to keep the cleaning system operating effectively.

Electron Machine's efforts led to a system using their "almost indestructible" MPR E-Scan Refractometer combined with heated high-pressure water for cleaning. The resulting combination provides an effective removal of optical coatings by reducing thermal changes and minimizing maintenance to allow for a reliable measurement source for on-line automatic control.

If you're interested in refractometry in pulp and paper processing, look no further than Electron Machine. They have the history, the experience, and the toughest inline refractometer on the planet.

For more information, visit http://www.electronmachine.com or call (352) 669-3101.

Inline Refractometers for Measuring Black Liquor Evaporation

Measuirng black liquor solids concentration.

Introduction:

Refractometers have long proven to be the instrument of choice for black liquor solids concentration. Electron Machine Corporation of Umatilla, Florida pioneered this technology to accurately measure black liquor dissolved solids 5 decades ago. Their MPR E-Scan inline refractometer provides digital accuracy with rugged components required for years of reliable use when installed in harsh industrial environments. This combination allows for easy integration into a mill-wide monitor / control system providing operators the information needed for efficient and easy-to-service control.

Application:

An important and overlooked area for refractometers is the pulp washing operation. By monitoring the concentration output the washers can be balanced to meet the needs of the evaporation process and a mill is able to regulate the mixing liquor. This control allows a consistent concentration supply to the evaporators and boiler. This installation is simple and greatly reduces hand sampling.

MPR E-Scan

Evaporation:

By installing the Electron Machine Corporation MPR E-Scan with Isolation Valve Adapters before and after each evaporator effect, the concentration and temperature output can be utilized to monitor efficiency, detect problems and operate economically. This monitoring allows control operators to adjust steam usage for optimal solids evaporation. Operators can determine if a quick flush cleaning can be performed to improve efficiency, prolonging the time between invasive, labor intensive cleanings. It also allows the detection of any problems before the liquor reaches the boiler, plus provides a consistent solids percentage for firing.

Conclusion:

With the addition of the Electron Machine Corporation MPR E-Scan to a mills process control system, a company can see increased profitability through the optimized control of steam usage, reduced labor cost from the reduction of offline hand sampling and the ability to prolong the time between labor intensive offline cleanings. This greater control provides more consistent firing solids allowing boilers to operator more efficiently.

Key Benefits:

• Consistent black liquor solids
• Minimize steam consumption
• Economical operation
• Optimize man hours
• Reduce costly evaporator cleanings