Slurry dewatering and conversion of biosolids to a renewable fuel

• US 20060096163A1
• Filed: 11/07/2005
• Published: 05/11/2006
• Est. Priority Date: 11/10/2004
• Status: Active Grant

• Current Assignee: EnerTech Environmental, Inc.
• Original Assignee: EnerTech Environmental, Inc.
• Inventors: Dickinson, Norman L., Dooley, Brian, Bolin, Kevin M., Overstreet, Edward
• Granted Patent: US 7,909,895 B2
• Time in Patent Office: Days
• US Class Current: 44/552
• CPC Class Codes: C02F 11/10 by pyrolysis
• CPC Class Codes: C02F 2103/001 Runoff or storm water
• CPC Class Codes: C10G 1/00 Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal mechanical winning of oil from oil-shales, oil-sand, or the like B03B
• CPC Class Codes: C10G 1/02 by distillation
• CPC Class Codes: C10G 2300/1003 Waste materials
• CPC Class Codes: C10G 2300/1011 Biomass
• CPC Class Codes: C10G 2300/4043 Limiting CO2 emissions
• CPC Class Codes: C10G 2300/4081 Recycling aspects
• CPC Class Codes: C10G 2300/805 Water
• CPC Class Codes: C10G 2300/807 Steam
• CPC Class Codes: C10L 5/46 on sewage, house, or town refuse C10L5/403, C10L5/406 take precedence
• CPC Class Codes: C10L 9/086 Hydrothermal carbonization
• CPC Class Codes: F23G 7/001 for sludges or waste products from water treatment installations F23G5/008 takes precedence
• CPC Class Codes: Y02E 20/16 Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel
• CPC Class Codes: Y02P 30/20 using bio-feedstock
• CPC Class Codes: Y02P 30/40 Ethylene production
• CPC Class Codes: Y02W 10/37 using solar energy
• CPC Class Codes: Y02W 30/40 Bio-organic fraction processing; Production of fertilisers from the organic fraction of waste or refuse

Abstract

In the processes for treating municipal sewage and storm water containing biosolids to discharge standards, biosolids, even after dewatering, contain typically about 80% water bound in the dead cells of the biosolids, which gives biosolids a negative heating value. It can be incinerated only at the expense of purchased fuel. Biosolids are heated to a temperature at which their cell structure is destroyed and, preferably, at which carbon dioxide is split off to lower the oxygen content of the biosolids. The resulting char is not hydrophilic, and it can be efficiently dewatered and/or dried and is a viable renewable fuel. This renewable fuel can be supplemented by also charging conventional biomass (yard and crop waste, etc.) in the same or in parallel facilities. Similarly, non-renewable hydrophilic fuels can be so processed in conjunction with the processing of biosolids to further augment the energy supply.

Claims

1. A process of converting biosolids into a fuel comprising the steps of:

providing biosolids comprising cells and cell-bound water;

applying sufficient pressure to the biosolids to maintain liquidity;

heating the pressurized biosolids to a first temperature sufficient to rupture cells and thereby free the cell-bound water to form a slurry of ruptured biosolids cells;

depressurizing the slurry of ruptured biosolids cells; and

removing at least a portion of the freed cell-bound water from the slurry to provide an at least partially dewatered ruptured biosolids product.

2. A process according to claim 1, including heating the biosolids to a second temperature sufficient to evolve carbon dioxide from the biosolids and form a char slurry comprising charred, ruptured biosolids cells.

3. A process according to claim 2, including separating the carbon dioxide from the char slurry.

4. A process according to claim 3, wherein removing at least a portion of the freed cell-bound water provides an at least partially dewatered char product, and including reacting the char product with a gas comprising oxygen to convert its fuel value into thermal energy, and further comprising at least one of the steps of using the thermal energy and incinerating the fuel.

5. A process according to claim 1, wherein the step of applying sufficient pressure comprises providing a pump.

6. A process according to claim 3, wherein booster pumps are provided downstream to reduce the required head pressure of the pump.

7. A process according to claim 3, wherein free water from the removing step is recirculated to the providing step in order to reduce the required head pressure of the pump.

8. A process according to claim 4, wherein the step of removing comprises removing water-soluble constituents from the char slurry.

9. A process according to claim 8, further comprising the step of washing the dewatered char product with clean water.

10. A process according to claim 8, further comprising the step of washing the dewatered char product with a solvent.

11. A process according to claim 1, wherein the step of removing further comprises the step of substantially removing free water from at least one of the slurry and the partially dewatered product as steam, producing a dried product.

12. A process according to claim 11, wherein the dried product is a dried char product, and comprising mixing the dried char product with a fuel oil to form a coal-oil mixture.

13. A process according to claim 11, wherein the slurry is a char slurry of charred ruptured biosolids cells, and comprising mixing the char slurry with a fuel oil to form a coal-oil mixture.

14. A process according to claim 11, wherein the dried product is a char product, and comprising converting the dried char product to a carbon-based product.

15. A process according to claim 1, wherein the slurry is a char slurry of charred ruptured biosolids cells, and comprising converting the char slurry to a carbon-based product.

16. A process according to claim 1, wherein the slurry is a char slurry and the at least partially dewatered ruptured biosolids product is a char product.

17. A process according to claim 16, further comprising transporting the char product to a chemical plant and converting the char product to at least one of a synthesis gas, oil, oxygenated compounds, carbon fibers, fertilizer additive, and combinations thereof.

18. A process according to claim 1, wherein the removing step further comprises recycling at least a portion of the aqueous phase to the providing step.

19. A process according to claim 16, further comprising pretreating water removed from the char slurry.

20. A process according to claim 19, wherein pretreating the aqueous phase renders a methane gas.

21. A process according to claim 19, including recycling at least a portion of pretreated water to the providing step.

22. A process according to claim 19, wherein pretreating the water comprises pretreating with at least one of membranes, vibrating membranes, ammonia removal, anaerobic digestion, and reverse osmosis.

23. A process according to claim 22, further comprising adding a chelating agent to the water removed from the charred slurry.

24. A process according to claim 19, further comprising the step of adding a chelating agent to the char product.

25. A process according to claim 1, further comprising adding at least one of water, heat, steam, and a combination thereof to the biosolids prior to the step of applying.

26. A process according to claim 1, comprising at least one of grinding and shearing the biosolids prior to the step of applying.

27. A process according to claim 1, comprising screening the biosolids prior to the step of applying.

28. A process according to claim 1, further comprising at least one of cooling the slurry before depressurization and cooling the slurry after depressurization.

29. A process according to claim 1, wherein the depressurizing step occurs in at least two increments.

30. A process according to claim 28, wherein the step of cooling occurs prior to the depressurizing step.

31. A process according to claim 3, wherein, when foam interferes with the step of separating, char slurry from a lower part of a separator is pumped and sprayed toward the foam from at least one spray nozzle located above a liquid level in the separator.

32. A process according to claim 2, further comprising discharging the carbon dioxide through a flame of at least one of an oxidizer and a process heater.

33. A process according to claim 3, wherein the step of separating the carbon dioxide further comprises at least one of the steps of:

sequestering carbon dioxide into at least one of earth and a large body of water;

purifying and using carbon dioxide for at least one of carbonizing beverages, pressurizing fire extinguishers, spray can propellant, refrigerant, and inert blanketing gas;

using the carbon dioxide as a mixable flooding agent for tertiary oil recovery; and

combinations thereof.

34. A process according to claim 1, wherein the step of heating further comprises providing a hot heat transfer fluid and heating the pressurized biosolids with the hot heat transfer fluid.

35. A process according to claim 34, wherein the step of heating the pressurized biosolids with the heat transfer fluid comprises further heating the pressurized biosolids by condensing vapor of vaporized heat transfer fluid.

36. A process according to claim 1, further comprising exchanging heat in the slurry with the pressurized biosolids.

37. A process according to claim 36, wherein the step of exchanging occurs prior to the step of applying.

38. A process according to claim 4, further comprising using the thermal energy for process heat.

39. A process according to claim 38, further comprising the step of using the process heat to dry the dewatered char product.

40. A process according to claim 4, wherein ash produced is utilized in at least one of a cement kiln, building materials, compost, or fertilizer product.

41. A process according to claim 1, wherein heating comprises using steam as a heating medium.

42. A process according to claim 2, wherein sulfur contained in the carbon dioxide gas is generated in the separating step, and including removing the sulfur with pollution control equipment.

43. A process according to claim 16, further comprising recovering iron from the dewatered char product.

44. A process according to claim 16, further comprising the steps of:

drying the dewatered char; and

cooling dried char fuel immediately after drying.

45. A process of converting biomass into a renewable fuel comprising the steps of:

providing biomass comprising at least about 10% water;

slurrying the biomass by performing at least one of the steps of grinding and adding at least one of fresh water, recycled water, steam, and a combination thereof to form a pumpable slurry;

applying sufficient pressure to the biomass slurry to maintain liquidity and form pressurized biomass;

heating the pressurized biomass to a first temperature, wherein the first temperature is sufficient to form an aqueous char slurry, carbon dioxide, and free water;

depressurizing the biomass char slurry;

separating the carbon dioxide from the biomass char slurry; and

removing at least a portion of the free water from the biomass char slurry to provide a dewatered biomass char product containing a decreased oxygen content.

46. A process according to claim 45, comprising the steps of:

reacting the dewatered biomass char product with a gas comprising oxygen to thereby convert its fuel value into thermal energy; and

using the thermal energy.

47. A process according to claim 45, wherein the biomass comprises at least one of paper mill sludge, sludge from paper recycling operations, agricultural and forestry wastes, peat, food waste, hog manure, chicken litter, cow manure, other animal manures, rice hulls, bagasse, green waste, municipal solid waste, palm oil residue, refuse derived fuels, Kraft Mill black liquor, and short rotation energy crops.

48. A process according to claim 45, wherein the first temperature is between about 200°

C. and 345°

C. (400°

F. and 650°

F.).

49. A process according to claim 45, wherein the step of providing further comprises providing an agent for dissolution of at least one polluting or slag-forming element in the biomass.

50. A process according to claim 45, further comprising the step of adding an agent for dissolution of at least one polluting or slag-forming element present in the dewatered biomass char product.

51. A process according to claim 50, wherein the agent comprises an alkali.

52. A process according to claim 45, wherein a portion of the freed water is recycled to the adding step.

53. A process according to claim 45, wherein the step of removing comprises the step of substantially removing water from at least one of the biomass char slurry and dewatered product as steam.

54. A process according to claim 45, further comprising the step of cooling the aqueous char slurry to a second temperature less than the first temperature.

55. A process according to claim 54, wherein the second temperature is about 40°

C. to 90°

C. (100°

F. to 200°

F.).

56. A process according to claim 45, further comprising the step of discharging the carbon dioxide through a flame of at least one of an oxidizer or process heater.

57. A process according to claim 45, wherein process water from an adjacent wastewater treatment plant is used in the slurrying step.

58. A process according to claim 45, further comprising the step of pretreating at least a portion of the free water to form pretreated water and recycling the pretreated water to an adjacent wastewater treatment plant.

59. A process according to claim 45, further comprising the step of using a digester gas from an adjacent wastewater treatment plant as fuel for the heating step.

60. A process according to claim 45, further comprising the step of using the dewatered biomass char product as fuel in a cement kiln.

61. A process according to claim 60, further comprising the step of recycling waste heat from the cement kiln to at least one of the performing and heating steps.

62. A process according to claim 60, further comprising the step of using blowdown water from an adjacent cement kiln for the performing step.

63. A process according to claim 60, further comprising the step of using the carbon dioxide for at least one of heat recovery or odor reduction in the adjacent cement kiln.

64. A process according to claim 45, further comprising the step of using the dewatered biomass char product as fuel in a thermal power station.

65. A process according to claim 64, further comprising the step of using at least a portion of the freed water for cooling an adjacent thermal power station.

66. A process according to claim 64, further comprising the step of using heat from the adjacent thermal power station for at least one of the performing and heating steps.

67. A process according to claim 64, further comprising the step of using the carbon dioxide for at least one of heat recovery and odor reduction in the adjacent thermal power station.

68. A process according to claim 64, further comprising the step of using water from the adjacent thermal power station for the performing step.

69. A process according to claim 45, further comprising the step of using the dewatered biomass char product as fuel in a blast furnace.

70. A process according to claim 63, further comprising the step of using at least a portion of the freed water for cooling an adjacent blast furnace.

71. A process according to claim 63, further comprising the step of using heat from the adjacent blast furnace for at least one of the performing and heating steps.

72. A process according to claim 63, further comprising the step of using the evolved carbon dioxide for at least one of heat recovery and odor reduction in the adjacent blast furnace.

73. A process of converting a slurry of a combination of at least one of a biosolids and low-rank fossil fuels into a combustible fuel comprising the steps of:

providing biosolids comprising at least about 10% water;

providing low-rank fossil fuel;

mixing the biosolids and low-rank fossil fuel to form a feed slurry;

applying sufficient pressure to the feed slurry to maintain liquidity and form pressurized feed slurry;

heating the pressurized feed slurry to a sufficient temperature for cell rupture to form an aqueous char slurry comprising carbon dioxide and free water;

depressurizing the aqueous char slurry;

separating the carbon dioxide from the aqueous char slurry; and

removing at least a portion of the free water from the aqueous char slurry to provide a dewatered char product.

74. A batch process of converting at least one of biosolids, biomass, and low-rank fossil fuels into a renewable fuel comprising the steps of:

providing at least one of biosolids, biomass, low-rank fuels, and combinations thereof;

slurrying the materials from the providing step by performing at least one of the steps of grinding and adding at least one of fresh water, recycled water, steam, and a combination thereof to form a pumpable slurry;

pressurizing the pumpable slurry to keep it substantially in its liquid state;

heating the pressurized pumpable slurry to a sufficient temperature for cell rupture to form a char slurry with a decreased oxygen content, carbon dioxide, and free water;

depressurizing the char slurry;

separating the carbon dioxide from the char slurry; and

removing at least a portion of the water in the char slurry to provide an at least partially dewatered char product.

75. A process according to claim 74, further comprising the step of reacting the dewatered char product with a gas comprising oxygen to convert fuel value into thermal energy to form char.

76. A process according to claim 74, wherein the step of pressurizing further comprises injecting steam into the batch process to heat the biosolids.

77. A process according to claim 74, wherein the heating step is performed by at least one of burning the fuel gas from a gasifier, and steam from a boiler.

78. A process according to claim 77, wherein the fuel for the heating step is at least one of a fossil fuel, digester gas, and product char.

79. A process according to claim 74, wherein the step of removing comprises adding at least one polymer to enhance separation of the aqueous phase.

80. A process according to claim 74, further comprising the step of using the dewatered char product as a raw material for hydrogen fuel cells through partial oxidation to a fuel gas.

81. A process according to claim 74 in which, prior to depressurization, a portion of the char slurry is recycled back to the heated, pressurized biosolids.

82. A process of converting biosolids into a renewable fuel comprising the steps of:

delivering biosolids to a raw feed tank;

performing at least one of heating, grinding, and shearing to the biosolids in the raw feed tank to form a slurry;

heating the slurry;

reacting the slurry to form char, wherein the char has a substantial increase in solids carbon content and a substantial decrease in solids oxygen content;

cooling the char slurry;

depressurizing the char slurry;

liberating carbon dioxide from the char;

dewatering the char to form a dewatered char product; and

drying or pelletizing the dewatered char product, wherein the dewatered char product has about 15% to 20% of the weight of comparable raw biosolids.

83. A process of operating a cement kiln comprising the steps of:

providing wet biosolids including bound water;

heating the wet biosolids using process heat from the cement kiln until the bound water evaporates to form dry biosolids;

combusting the dry biosolids in the cement kiln to form combusted biosolids comprising at least a portion of ash; and

using the portion of ash to reduce the quantities of limestone, clay or shale added to the cement.

84. A method of converting treated sewage sludge comprising biosolids including cell-bound water into a product having a positive fuel value comprising rupturing the biosolids cells to free the water bound therein, subjecting the ruptured biosolids cells to sufficient temperature to convert the ruptured biosolids cells into char, and removing at least a portion of the water from the slurry to form a char product adapted to be combusted at an elevated temperature and providing heat energy from the char product.

85. A method according to claim 84 including suspending the ruptured biosolids cells in at least the water freed from the biosolids cells.

86. A method of economically disposing of sludge comprising biosolids including cell-bound water that gives the sludge a negative heating value, the method comprising acquiring the sewage sludge and obtaining money or an item of value for accepting the sewage sludge, maintaining the sewage sludge as a slurry comprising water and suspended biosolids, heating the slurry sufficiently to rupture the biosolids cells and thereby liberate water previously bound in the biosolids cells, converting ruptured biosolids cells into char cell parts, removing at least some of the water, including water liberated from the ruptured biosolids cells, to form a char product, and disposing of the char product in a manner that generates additional value.

87. A method according to claim 86, wherein disposing of the char product comprises combusting the char product to generate heat therewith.

88. A method according to claim 86, wherein disposing comprises furnishing the char product for use by a third person.

89. A method of disposing of sludge generated at a sewage or wastewater treatment plant in an economical and environmentally benign manner, the sludge comprising a mass of biosolids and water, the method comprising obtaining the mass of biosolids from the plant, requiring a payment for obtaining the sludge from the plant, heating the biosolids sufficiently to rupture cell walls of the biosolids and liberate cell-bound water from the biosolids, removing a sufficient amount of the water mixed with the mass of ruptured biosolids to convert the mass into a mass having a positive heat value, and using the heat value of the mass of biosolids to generate further value therewith.

90. A method according to claim 89 including carbonizing the ruptured cells of the biosolids.

91. A method according to claim 90, wherein carbonizing the ruptured biosolids cells occurs prior to the step of removing water.

92. A method according to claim 91 wherein using the heat value comprises incinerating the carbonized ruptured biosolids cells.