A method and apparatus for protecting a furnace floor of a black liquor recovery boiler, where the furnace floor is covered by a protective layer, the protective layer being formed of a salt mixture including at least two different salts.

An assembly for cleaning a smelt spout includes a cleaning head, a drive rod connected with the cleaning head, and a pneumatic or other drive connected to selectively extend or retract the drive rod. The drive rod may be connected with the cleaning head by a pivotal connection. The cleaning head may be bifurcated. The cleaning head may include a leading edge configured to engage and clean a spout opening from which smelt from a chemical reduction furnace flows to the spout. The assembly may further include a pivot point and, as the drive selectively extends the drive rod, torque about the pivot point produced by the cleaning head and an extending portion of the drive rod rotates the cleaning head downward to engage a smelt spout.

The specification relates to a method and a system for adjusting pH of green liquor dregs. The method comprises contacting a slurry containing green liquor dregs (100, 200, 300, 400, 500) with flue gas (101, 201, 301, 401, 501). The system comprises a recovery boiler (105) configured to burn black liquor to produce smelt, a smelt dissolving tank (107) configured to dissolve the smelt to produce green liquor comprising green liquor dregs, and a green liquor clarifier/filter (103) and/or a dregs filter (104) configured to separate a slurry containing green liquor dregs (100, 200, 300, 400, 500) from the green liquor. The system further comprises a vessel (102, 202, 302, 402) configured to receive a slurry containing green liquor dregs (100, 200, 300, 400, 500) and a gas inlet (210, 310, 410, 510) configured to convey flue gas (101, 201, 301, 401, 501) to be contacted with the slurry containing green liquor dregs (100, 200, 300, 400, 500).

The specification relates to a method and a system for adjusting pH of green liquor dregs. The method comprises contacting a slurry containing green liquor dregs (100, 200, 300, 400, 500) with flue gas (101, 201, 301, 401, 501). The system comprises a recovery boiler (105) configured to burn black liquor to produce smelt, a smelt dissolving tank (107) configured to dissolve the smelt to produce green liquor comprising green liquor dregs, and a green liquor clarifier/filter (103) and/or a dregs filter (104) configured to separate a slurry containing green liquor dregs (100, 200, 300, 400, 500) from the green liquor. The system further comprises a vessel (102, 202, 302, 402) configured to receive a slurry containing green liquor dregs (100, 200, 300, 400, 500) and a gas inlet (210, 310, 410, 510) configured to convey flue gas (101, 201, 301, 401, 501) to be contacted with the slurry containing green liquor dregs (100, 200, 300, 400, 500).

Various techniques are described for enhanced combustion of hot water extraction (HWE) derived liquor. For example, the HWE derived liquor can be pre-treated prior to introduction into a combustion chamber. The pre-treatment can include subjecting HWE derived liquor to filtration to remove suspended solids, evaporation to produce a first stage concentrated HWE liquor; additional concentration to produce a second stage concentrated HWE liquor; additional filtration to remove additional suspended solids; and pre-heating to produce a preheated HWE liquor. The preheated HWE liquor can be atomized and combined with pre-heated combustion air supplied into a combustion chamber to effect combustion of the HWE derived liquor.

Various techniques are described for enhanced combustion of hot water extraction (HWE) derived liquor. For example, the HWE derived liquor can be pre-treated prior to introduction into a combustion chamber. The pre-treatment can include subjecting HWE derived liquor to filtration to remove suspended solids, evaporation to produce a first stage concentrated HWE liquor; additional concentration to produce a second stage concentrated HWE liquor; additional filtration to remove additional suspended solids; and pre-heating to produce a preheated HWE liquor. The preheated HWE liquor can be atomized and combined with pre-heated combustion air supplied into a combustion chamber to effect combustion of the HWE derived liquor.

A chemical recovery boilers is described in which the primary air system is reconfigured to provide aggressive charbed control and improved combustion in the lower furnace. The fewest number of primary air ports are used on two opposing walls to generate powerful air jets that penetrate across the boiler providing physical and thermal stability to the charbed while increasing the heat release and combustion stability in the lower furnace, increasing reduction efficiency, and lowering carryover and emissions. Various embodiments are described including operating strategies and multi-level black liquor injection.

A chemical recovery boilers is described in which the primary air system is reconfigured to provide aggressive charbed control and improved combustion in the lower furnace. The fewest number of primary air ports are used on two opposing walls to generate powerful air jets that penetrate across the boiler providing physical and thermal stability to the charbed while increasing the heat release and combustion stability in the lower furnace, increasing reduction efficiency, and lowering carryover and emissions. Various embodiments are described including operating strategies and multi-level black liquor injection.

The invention is directed to compositions and processes concerning efficient downstream processing of products derived from organic acids pretreatment of plant materials.

In a method for the continuous precipitation of lignin from black liquor black liquor is provided so as to flow as a pressurized flow in a reactor with a dwell time of less than 300 s. An acidifying agent selected from the group of carbon dioxide, acid and their combinations is led to the flow at one or more feeding sites to lower the pH of black liquor. The pH is allowed to decrease by the effect of the acidifying agent in the pressurized flow to the precipitation point of lignin, the pressure of the pressurized flow is abruptly released, and lignin particles are separated from black liquor.