Sewage Sludge Recycling With A Pipe Cross-Reactor

Abstract

An improved process for enhancing the plant nutrient value of relatively low analysis organic waste material (e.g., sewage sludge) involves treating the waste material with an acid and base in a pipe-cross reactor. The process more particularly involves mixing the waste material with water to form a slurry (or initially taking the waste material as a slurry); pumping the slurry to a pipe-cross reactor for reaction with a base, acid, and water to form a melt: spraying the melt onto a recycling bed of fines in a granulator and flashing off the water contained in the melt as steam; rolling the melt onto recycled fine particles in a granulator to form granulated particles; and drying these granulated particles to form an enhanced plant nutrient value composition (e.g., a fertilizer or soil conditioner having a greater “NPK” value than the original relatively low analysis organic waste material). The invention also includes fertilizers produced according to the improved process, which fertilizers are of the same size and shape and density of commonly used fertilizers. The method advantageously utilizes the heat generated by the exothermic acid-base reaction in the pipe-cross reactor to remove the approximately 80% water from sludge, thus saving large amounts of energy normally used in conventional drying or burning methods, while, at the same time, conserving the intrinsic values of the nutrients and humates contained in the sludge. In one embodiment, the process includes a method of disposing of spent acid from a hot dip galvanizing process or a steel pickling process involving incorporating the spent acid to maintain the low pH of a venturi scrubber used in the improved process.

1 . A granular fertilizer of relatively low analysis organic waste material having an enhanced plant nutrient value composition, said fertilizer produced by the process comprising: mixing said relatively low analysis organic waste material with water to form a slurry capable of being pumped; pumping said slurry to a pipe-cross reactor for reaction with a base, acid, and water to form a melt; spraying said melt onto a recycling bed of fines in a granulator, and flashing off water contained in the melt as steam: rolling said melt onto fine particles in the granulator to form said granular fertilizer; and drying said granular fertilizer to reduce the moisture content thereof to form dried granular fertilizer comprising an enhanced plant nutrient value composition. 
     
     
         2 . The granular fertilizer of  claim 1 , wherein said granular fertilizer is substantially homogenous. 
     
     
         3 . The granular fertilizer of  claim 1 , wherein said granular fertilizer is sized and shaped for application by standard granular fertilizer application equipment. 
     
     
         4 . A granular fertilizer having a plant nutrient value composition of 12% nitrogen, 3% phosphorous, and 6% potassium, said fertilizer produced by the process comprising: mixing low analysis organic waste material with water to form a slurry capable of being pumped; pumping said slurry to a pipe-cross reactor for reaction with a base, an acid, and water to form a melt; spraying said melt onto a recycling bed of fines in a granulator and flashing off water contained in the melt as steam; rolling said melt onto fine particles in the granulator to form said granular fertilizer; drying said granular fertilizer to reduce the moisture content thereof to form dried granular fertilizer; and collecting fumes from the granulator containing steam, ammonia and particulate by maintaining a negative pressure inside the granulator by pulling the fumes through a venturi scrubber having a venturi throat with water having a pH of about 2 to about 3 as scrubber water sprayed into the venturi throat. 
     
     
         5 . The granular fertilizer of  claim 4 , wherein the pH of the scrubber water is kept at about 2 to about 3 by incorporating spent acid from a hot dip galvanizing process into the scrubber water. 
     
     
         6 . The granular fertilizer of  claim 5 , wherein said spent acid from said hot dip galvanizing process contains about three percent to about eight percent zinc. 
     
     
         7 . The granular fertilizer of  claim 6 , wherein said spent acid from said hot dip galvanizing process contains about three percent to about eight percent iron. 
     
     
         8 . The granular fertilizer of  claim 4 , wherein the pH of the scrubber water is kept at about 2 to about 3 by incorporating spent acid from a steel pickling process into the scrubber water. 
     
     
         9 . The granular fertilizer of  claim 8 , wherein said spent acid from said steel pickling process contains about three percent to about eight percent iron. 
     
     
         10 . The granular fertilizer of  claim 4 , wherein said granular fertilizer is substantially homogenous. 
     
     
         11 . The granular fertilizer of  claim 4 , further comprising an ingredient selected from the group consisting of lime, dolomite, calcite, hydrobiotite, gypsum, phosphates, potash, urea, soil clays, calcium peroxide, ammonium nitrate, vermiculite, humic acid, iron, manganese, magnesium, boron, copper, zinc, and combinations thereof. 
     
     
         12 . A granular fertilizer having a plant nutrient value composition of 12% nitrogen, 3% phosphorous, and 6% potassium, said fertilizer produced by the process comprising: mixing low analysis organic waste material with water to form a slurry capable of being pumped: pumping said slurry to a pipe-cross reactor for reaction with a base, acid, and water to form a melt; spraying said melt onto a recycling bed of fines in a granulator, and flashing off water contained in the melt as steam; rolling said melt onto fine particles in the granulator to form said granular fertilizer: and drying said granular fertilizer to reduce the moisture content thereof to form dried granular fertilizer comprising an enhanced plant nutrient value composition. 
     
     
         13 . The granular fertilizer of  claim 12 , wherein said granular fertilizer is substantially homogenous. 
     
     
         14 . The granular fertilizer of  claim 1 , further comprising an ingredient selected from the group consisting of lime, dolomite, calcite, hydrobiotite, gypsum, phosphates, potash, urea, soil clays, calcium peroxide, ammonium nitrate, vermiculite, humic acid, iron, manganese, magnesium, boron, copper, zinc, and combinations thereof.