TECHNOLOGICAL FIELD

Exemplary embodiments described herein pertain generally to desalination of seawater, wastewater, or other liquid including dissolved solids by using an additive including iso-butane to decrease a pressure needed for hydrate formation.

BACKGROUND

This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.

The current state of the art of desalination includes physical and chemical processes, such as adsorption, filtration, reverse osmosis, coagulation, flocculation, and chemical oxidation, or combinations of these for water purification [Seol-SustChemEng-2013].

Distillation and reverse osmosis (RO) are the current commercial technologies for water purification/desalination. Distillation is an expensive process due to high energy intensity. RO is membrane based and less expensive than distillation, but it suffers from fouling issues and it can only work with water feed with <5% Total Dissolved Solids (TDS). TDS is a measure of the combined content of all inorganic and organic substances contained in a liquid in molecular, ionized, or micro-granual (colloidal sol) suspended form.

A third approach based on hydrates has also been explored in the past. In the formation of a hydrate, a new stable structure is formed (under appropriate conditions) from two previously separated compounds, although no chemical bonds are changed. Water containing a salt can be brought in contact with a hydrate forming gas (e.g., CH4, CO2) at high pressure (P) and low temperature (T), which results in the formation of hydrates. Upon separation of the hydrate from the remaining liquid, the hydrates can be melted at lower P and/or higher T to extract relatively cleaner water. The fundamental driver for using hydrates for desalination is that during the process of hydrate formation, salt is rejected from the hydrate structure. Hydrates can also work with higher concentrations of TDS (˜30%). However, due to the high P requirement, this approach has been considered uneconomical. Over the last few years, there has been a renewed interest in this process, because additives (e.g., CycloPentane, CycloHexane, SF6, Propane, Hydrochlorofluorocarbon HCFC) can be introduced to decrease the P required for hydrate formation.

SUMMARY

A method for desalinating a liquid, including: contacting, within a hydrate former reactor, a feed gas stream including iso-butane in an amount ranging from above zero mol % to about 3 mol % and liquid seawater or liquid wastewater including a dissolved salt, wherein a temperature and pressure within the hydrate former reactor is controlled so that the feed gas stream and the liquid seawater or liquid wastewater form a hydrate slurry; separating hydrate particles from the hydrate slurry; and decomposing the hydrate particles into its constituents of water and gas or gas mixture containing iso-butane, wherein the water has a concentration of the dissolved salt that is less than that of the liquid seawater or liquid wastewater.

In the method, the hydrate former reactor can be a multi-stage reactor.

In the method, the hydrate former reactor can be a single-stage reactor.

In the method, the hydrate former reactor can be a counter current flow reactor.

In the method, the hydrate former reactor can be a co-current flow reactor.

The method can further include recycling the iso-butane recovered from the decomposing step in the contacting step.

In the method, the feed gas stream can include CO2, CH4, or a combination thereof.

In the method, the hydrate former reactor can include one or more of a tower, pipe, tube, or tank.

A system for desalinating a liquid, including: a hydrate former reactor that contacts a feed gas stream including iso-butane in an amount ranging from above zero mol % to about 3 mol % and liquid seawater or liquid wastewater including a dissolved salt, wherein a temperature and pressure within the hydrate former reactor is controlled so that the feed gas stream and the liquid seawater or liquid wastewater form a hydrate slurry; and a hydrate decomposition unit that separates hydrate particles from the hydrate slurry and decomposes the hydrate particles into its constituents of water and gas or gas mixture containing iso-butane, wherein the water has a concentration of the dissolved salt that is less than that of the liquid seawater or liquid wastewater.

In the system, the hydrate former reactor can be a multi-stage reactor.

In the system, the hydrate former reactor can be a single-stage reactor.

In the system, the hydrate former reactor can be a counter current flow reactor.

In the system, the hydrate former reactor can be a co-current flow reactor.

In the system, the iso-butane recovered by the hydrate decomposition unit can be recycled and combined with the feed gas stream.

In the system, the feed gas stream can include CO2, CH4, or a combination thereof.

In the system, the hydrate former reactor can include one or more of a tower, pipe, tube, or tank.

