Method for numerical simulation of reactive transport during co2+o2 in-situ leaching of uranium at sandstone-type uranium deposit

Patent metadata

Field	Value
Publication number	US-2022290274-A1
Application number	US-202117531300-A
Country	US
Kind code	A1
Filing date	Nov 19, 2021
Priority date	Mar 10, 2021
Publication date	Sep 15, 2022
Grant date	—

Abstract

The present disclosure provides a method for numerical simulation of reactive transport during CO 2 +O 2 in-situ leaching of uranium at a sandstone-type uranium deposit. Unlike the traditional method for numerical simulation of solute transport during in-situ leaching of uranium with consideration of only convection and diffusion, the method permits establishment of a multi-field coupled reactive solute transport model to simulate the dynamic leaching process of a sandstone-type uranium deposit in Northern China. The method provided in the present disclosure includes: creating a thermodynamic database suitable for CO 2 +O 2 leaching of a sandstone-type uranium deposit in Northern China, and with consideration of the dynamic reaction process of uranium dissolution under combined action of oxygen O 2 (aq) and bicarbonate HCO 3 − , performing numerical simulation of reactive transport during CO 2 +O 2 in-situ leaching of uranium using a TOUGHREACT simulation technology framework.

First claim

What is claimed is:

1 . A method for numerical simulation of reactive transport during CO 2 +O 2 in-situ leaching of uranium at a sandstone-type uranium deposit, said method comprising the following steps:
(1) collecting basic data of a mining area of the sandstone-type uranium deposit, said basic data including relative plane positions of injection and production wells in the mining area, a distance between injection and production wells of the mining area, injection and production rates, groundwater level monitoring data, and hydro-chemical analysis data of leaching solution and leachate; (2) constructing a hydrodynamic model of CO 2 +O 2 in-situ leaching of uranium based on the basic data collected in step (1) in combination with hydrogeological conditions of the mining area including the type, lithology and thickness of an ore-bearing aquifer, the depth of a groundwater level, the depth and thickness of an ore body, the condition of groundwater recharge based on the fundamental principle of conservation of mass and energy, and Darcy's law; (3) determining initial conditions, boundary conditions, hydraulic parameters, and a source-sink term of the hydrodynamic model, and performing spatial mesh dissection and temporal discretization; (4) solving the hydrodynamic model to obtain a distribution of temporal and spatial flow velocity vectors and a pressure distribution within a simulated domain; (5) establishing a reactive solute transport model of CO 2 +O 2 in-situ leaching of uranium based on the results of the hydrodynamic model in step (4) according to processes of component solute transport and chemical reactions in a system of in-situ leaching of uranium; (6) determining a network of geochemical reactions and processes of equilibrium reactions and dynamic reactions of the reactive solute transport model; (7) determining initial concentrations of simulated components in the reactive solute transport model, the composition of minerals involved in simulation, minerals produced by reactions and volume fractions thereof, and parameters for calculation of reaction dynamic rates of the minerals involved in simulation; and (8) solving the reactive solute transport model to obtain trends of variation in leaching concentration of dissolved uranium U (VI), pH and mineral content in the system of in-situ leaching of uranium, thereby completing the numerical simulation of reactive transport during CO 2 +O 2 in-situ leaching of uranium.

2 . The method for numerical simulation of reactive transport during CO 2 +O 2 in-situ leaching of uranium at a sandstone-type uranium deposit according to claim 1 , wherein the hydrodynamic model may be resolved by using a TOUGHREACT-V3/EOS9 module of a multi-component and multi-process reactive solute transport simulation program TOUGHREACT in step (4).

3 . The method for numerical simulation of reactive transport during CO 2 +O 2 in-situ leaching of uranium at a sandstone-type uranium deposit according to claim 1 , wherein the reactive solute transport model of CO 2 +O 2 in-situ leaching of uranium in step (5) is described by using the following mass conservation equation for chemical components:

∂

(

ϕ
⁢

c
i

)

∂
t

=

-

∇

(

ρ
⁢

c
i

⁢
v

)

+

∇

(

D
e

⁢

∇

c
i

)

+
Q
+

ϕ
⁢
R

(
1
)

where the term on the left of the equation denotes a rate of mass change of chemical component i in a reaction system, and the term on the right denotes the contributions of convection and diffusion of the chemical component, a source-sink term, and dissolution and precipitation of mineral components to the mass change of the chemical component; c i is a concentration of the chemical component i involved in simulation in the reactive solute transport model, D e is an effective diffusion coefficient, Q is the source-sink term in the reaction system, R is a chemical reaction rate, ϕ is a porosity, ρ is a fluid density, v is a hydrodynamic velocity, and ∇ is a gradient operator.

4 . The method for numerical simulation of reactive transport during CO 2 +O 2 in-situ leaching of uranium at a sandstone-type uranium deposit according to claim 1 , wherein the determining a network of chemical reactions and processes of equilibrium reactions and dynamic reactions of the reactive solute transport model in step (6) comprises:
(a) determining chemical reactions during CO 2 +O 2 in-situ leaching of uranium:
CO 2 (aq)+H 2 O=H + +HCO 3 −   (2)

2UO 2 (s)+O 2 =2UO 3 (S)   (3)

UO 3 (s)+2HCO 3 − =UO 2 (CO 3 ) 2 2− +H 2   (4)

UO 3 (s)+CO 3 2− +2HCO 3 − =UO 2 (CO 3 ) 3 4− +H 2 O   (5)

(b) creating a thermodynamic database of equilibrium reactions: adding the produced species of the dissolved uranium U (VI) and other components involved in simulation in the system of CO 2 +O 2 in-situ leaching of uranium and corresponding equilibrium constant data to create a thermodynamic database of the CO 2 +O 2 in-situ leaching of uranium for calculation of component forms of desired species and for use in numerical simulation of reactive solute transport; and (c) establishing a rate equation for dynamic reactions: determining a rate equation for reactions involved in dissolution and precipitation of minerals based on the transition state theory (TST) of chemical reactions.

5 . The method for numerical simulation of reactive transport during CO 2 +O 2 in-situ leaching of uranium at a sandstone-type uranium deposit according to claim 4 , wherein

Assignees

• Nanjing University Of Technology
• Univ Hohai

Inventors

• Wu Jianfeng
• Wu Jichun
• Qiu Wenjie
• Yang Yun
• Liu zhengbang
• Weng Haicheng
• Li Hongxing
• Liu Shuangmin

Classifications

• C22B60/0221

  by leaching · CPC title

• C22B60/0265

  extraction by solid resins · CPC title

• G01V9/007

  by detecting gases or particles representative of underground layers at or near the surface (analysing earth materials G01N33/24; analysing gases per se G01N) · CPC title

• G01V99/00 Primary

  Subject matter not provided for in other groups of this subclass · CPC title

• C22B60/0226 Primary

  using acidic solutions or liquors · CPC title