Method and system for preparing fuel gas by utilizing organic waste with high water content

Patent metadata

Field	Value
Publication number	US-10611657-B2
Application number	US-201616320869-A
Country	US
Kind code	B2
Filing date	Jul 29, 2016
Priority date	Jul 29, 2016
Publication date	Apr 7, 2020
Grant date	Apr 7, 2020

Abstract

The present invention provides a method and system for preparing fuel gas by utilizing an organic waste with high water content. The method comprises the following steps: 1) providing an organic waste with high water content; 2) performing hydrothermal reaction by using the organic waste with high water content as a reactant to obtain a hydrothermal reaction product; 3) enabling the hydrothermal reaction product to generate steam, and separating a solid product and an oily liquid product in the hydrothermal reaction product; 4) performing gasification reaction by using the solid product, the oily liquid product and the steam as reactants to obtain a gasification reaction product; and 5) purifying the gasification reaction product to obtain clean fuel gas. The present invention further provides a system for preparing fuel gas. The method can be used for preparing clean fuel gas from the organic waste with water content of 60% or more.

First claim

The invention claimed is:

1. A method for preparing fuel gas by utilizing an organic waste with water content greater than 60% by weight, wherein the method comprises the following steps:
1) providing an organic waste with water content greater than 60% by weight;
2) performing hydrothermal reaction by using the organic waste with water content greater than 60% by weight as a reactant to obtain a first reaction product;
3) enabling the first reaction product to generate steam, and separating a solid product and an oily liquid product in the first reaction product;
4) performing gasification reaction by using the solid product, the oily liquid product and the steam as reactants to obtain a second reaction product; and
5) purifying the second reaction product to obtain clean fuel gas-;
wherein MgO is also added to the reactant of the hydrothermal reaction, and the weight of added MgO is 1-3.5% of the dry material of the organic waste with water content greater than 60% by weight.

2. The method according to claim 1 , wherein the organic waste with water content greater than 60% by weight is one or a mixture of a plurality of sewage sludge, oil sludge, industrial sludge, pharmaceutical waste, distiller's grains, kitchen waste, and sick and dead livestock.

3. The method according to claim 1 , wherein the pH value of the reactant of the hydrothermal reaction is 8.5-9.5.

4. The method according to claim 1 , wherein ferric sulfate or ferric oxide or sodium hydroxide is also added to the reactant of the hydrothermal reaction.

5. The method according to claim 4 , wherein the weight of added ferric sulfate or ferric oxide or sodium hydroxide is 0.5-3% of the dry material of the organic waste with water content greater than 60% by weight.

6. The method according to claim 1 , wherein the reaction temperature of the hydrothermal reaction is 220-260° C. and the reaction time is 30-40 min.

7. The method according to claim 1 , wherein the first reaction product generates the steam through flash evaporation and is cooled.

8. The method according to claim 1 , wherein the specific step of separating the solid product and the oily liquid product in the first reaction product comprises:
i) separating the first reaction product through liquid-solid separation to obtain a water-containing solid product and an oil-containing liquid product;
ii) drying the water-containing solid product to obtain the solid product; and
iii) directly using the oil-containing liquid product as the oily liquid product, or further removing the water in the oil-containing liquid product to obtain the oily liquid product.

9. The method according to claim 8 , wherein at least part of the steam generated in the drying process of the water-containing solid product is utilized through the gasification reaction.

10. The method according to claim 8 , wherein the drying is performed by heating, and a heat source needed for heating is provided by the second reaction product.

11. The method according to claim 8 , wherein the dried solid product and the oil-containing liquid product or the oily liquid product are conveyed to a gasification site through a mixing conveyor, and the solid product and oil-containing liquid product or the oily liquid product are mixed in the conveying process.

12. The method according to claim 1 , wherein the temperature of the gasification reaction is 700-800° C., which is maintained by burning the clean fuel gas, wherein the burning amount L gas of the clean fuel gas is calculated according to the following formula:
HHV×L gas =C p,M ∫m M dT+C p,ash ∫m ash dT+C p,v ∫m v dT+Q p +M× 2500

wherein HHV is heating value of clean fuel gas, in unit of kJ/Nm 3 ; L gas is in unit of Nm 3 /kg material; m M is content of dry material, in unit of %; m ash is content of gasification residue, in unit of %; m v is total gas output, in unit of Nm 3 /kg, wherein tar is also included if tar exists; Q p is total reaction heat and is total heat effect of gasification reaction and enthalpy value for maintaining flue gas component produced during burning at gasification temperature, in unit of kJ/kg; M is residual water content of material after drying, in unit of %, m M +M=100%; C p, M , C p, ash , C p, v are respectively specific heat of dry material, residue and produced gas, respectively in units of kJ/kg·° C., kJ/kg·° C. and kJ/Nm 3 ·° C.

13. The method according to claim 1 , wherein heat needed for the hydrothermal reaction is provided by burning the clean fuel gas generated in step 5).

14. The method according to claim 1 , wherein the heating value of the clean fuel gas obtained in step 5) is greater than 8 MJ/Nm 3 , the clean fuel gas contains CO and H 2 , and the content of both HCN and HCNO is not greater than 20 ppm.

Assignees

• Univ Tongji

Inventors

• Dai Xiaohu
• Chen Dezhen
• Hu Yuyan
• Yin Lijie
• Ma Xiaobo

Classifications

• C10B53/00

  Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form (wet carbonising of peat C10F) · CPC title

• C10J2300/0946

  Waste, e.g. MSW, tires, glass, tar sand, peat, paper, lignite, oil shale · CPC title

• C10J2300/0909

  Drying · CPC title

• C10J3/84

  with means for removing dust or tar from the gas · CPC title

• C10J2300/0923

  Sludge, e.g. from water treatment plant · CPC title