Process for treating frac flowback and produced water including naturally occurring radioactive material

Patent metadata

Field	Value
Publication number	US-11834358-B2
Application number	US-201917258181-A
Country	US
Kind code	B2
Filing date	Jul 8, 2019
Priority date	Jul 10, 2018
Publication date	Dec 5, 2023
Grant date	Dec 5, 2023

Abstract

A process for treating frac flowback that contains barium, naturally occurring radioactive materials (NORM) and hardness for minimizing the amount of sludge produced that contains hazardous levels of NORM by employing a dual stage precipitation process. In the first stage a sulfate source is mixed with the frac flowback and barium sulfate and NORM is precipitated, the frac flowback is subjected to a solids-liquid separation process to produce a first effluent and a first sludge. In the second stage hardness is precipitated from the first effluent by addition of an alkali reagent, said first effluent is also subjected to solids-liquid separation producing a second effluent and a second sludge. The first sludge is recycled and mixed with the frac flowback and the sulfate source in a sufficient amount to maintain the NORM concentration in the second sludge at or below a threshold level.

First claim

What is claimed is:

1. A method of treating frac flowback containing barium, naturally occurring radioactive material (NORM) and hardness employing a dual stage precipitation process to reduce or minimize the production of sludge containing NORM, the method comprising:
A. in a first stage precipitation process:
i. mixing a sulfate source with the frac flowback in a barium sulfate-NORM reaction tank and precipitating barium sulfate and NORM;
ii. after mixing the sulfate source with the frac flowback, subjecting the frac flowback to a solids-liquid separation process to produce a first effluent and a first sludge containing the barium sulfate and NORM;

B. in a second stage precipitation process:
i. adding an alkaline reagent to the first effluent and increasing the pH of the first effluent;
ii. chemically softening the first effluent by precipitating hardness;
iii. after precipitating the hardness, subjecting the first effluent to a solids-liquid separation process and producing a second effluent and a second sludge containing the hardness;

C. recycling the first sludge containing the barium sulfate and NORM and mixing the first sludge with the frac flowback and the sulfate source; and
D. recycling a sufficient amount of the first sludge to maintain the NORM concentration in the second sludge at or below a threshold level.

2. The method of claim 1 wherein the first stage precipitation process is carried in the absence of barium being added to the frac flowback.

3. The method of claim 1 wherein the first sludge is recycled at a rate (weight of sludge recycle/weight of sludge generated) of 100:1 or greater.

4. The method of claim 1 wherein recycling a sufficient amount of the first sludge includes recycling about 5 to 20 parts of barium sulfate (dry basis) to 1 part of precipitated barium sulfate.

5. The method of claim 1 wherein in the first stage precipitation process, the sulfate source is mixed with frac flowback in the barium sulfate-NORM reaction tank; and the method includes maintaining the concentration of the first sludge in the barium sulfate-NORM reaction tank between about 10 g/L and 100 g/L so as to precipitate a majority of the NORM in the first stage precipitation process.

6. The method of claim 1 including recycling an amount of the first sludge that yields a residual sulfate concentration of less than 100 mg/L.

7. The method of claim 1 including recycling a sufficient amount of the first sludge to maintain the concentration of NORM in the second sludge below a threshold limit of 25 pCi/wet g.

8. A method of treating frac flowback containing barium, strontium, hardness and naturally occurring radioactive material (NORM) and employing a dual stage precipitation process to reduce or minimize the production of sludge containing NORM, the method comprising:
A. in a first stage precipitation process:
i. mixing a sulfate source with the frac flowback in a barium sulfate-NORM reaction tank and precipitating barium sulfate and NORM;
ii. after mixing the sulfate source with the frac flowback, subjecting the frac flowback to a solids-liquid separation process to produce a first effluent and a first sludge containing the barium sulfate and NORM;

B. in a second stage precipitation process:
i. adding an alkaline reagent to the first effluent in a reaction tank and increasing the pH of the first effluent;
ii. chemically softening the first effluent by precipitating hardness;
iii. after precipitating the hardness, subjecting the first effluent to a solids-liquid separation process and producing a second effluent and a second sludge containing the hardness;

C. recycling the first sludge containing the barium sulfate and NORM and mixing the first sludge with the frac flowback and the sulfate source;
D. recycling a sufficient amount of the first sludge to maintain the NORM concentration in the second sludge at or below a threshold level;
E. recycling the second sludge to the second stage reaction tank to assist in the chemical precipitation of hardness;
F. adding a “ballast” to the second stage precipitation process to assist in the settling of the solids; and
G. adding soda ash (sodium carbonate) or other carbonate sources to the second stage precipitation process to assist in the precipitation of calcium carbonate and/or strontium carbonate.

Assignees

• Veolia Water Solutions & Tech

Inventors

• Banerjee Kashi
• Blumenschein Charles
• Kronebusch Hillary
• Petrovich Sarah

Classifications

• C02F9/00 Primary

  Multistage treatment of water, waste water or sewage · CPC title

• C02F1/5236

  using inorganic agents · CPC title

• C02F1/62

  Heavy metal compounds · CPC title

• C02F1/66

  by neutralisation; pH adjustment (for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58) · CPC title

• C02F5/06

  using calcium compounds · CPC title