US 4,357,801 A · Removal of carbon dioxide in geothermal power systems

Abstract

A process for removing carbon dioxide in geothermal power generating processes employing a geothermal fluid such as geothermal brine containing carbon dioxide, to improve the efficiency of geothermal power generation, comprises introducing an aqueous alkaline solution, preferably an aqueous calcium hydroxide solution, into a vapor stream obtained from the brine during power generation, to remove carbon dioxide from the stream. In the case, for example, of power generation by direct contact heat exchange between geothermal brine and a working fluid such as isobutane, where the working fluid is expanded to generate power, aqueous calcium hydroxide can be introduced into a direct contact condenser into contact with the working fluid therein to remove CO.sub.2 present in the working fluid, thereby aiding in reducing loss of working fluid from the system and aiding in reducing pump power. The aqueous alkaline, e.g., calcium hydroxide, solution alternatively can be contacted with the geothermal fluid prior to flashing or prior to direct contact heat exchange with a working fluid, to remove CO.sub.2 from uncondensible gas contained in the fluid.

Claims14

Dependent claims

A process for removing carbon dioxide from a vapor stream containing carbon dioxide and a working fluid, said vapor stream being generated from a geothermal fluid in a geothermal energy recovery process, said process for removing carbon dioxide comprising:

(a) introducing said vapor stream containing carbon dioxide into a condenser zone;
(b) introducing an aqueous alkaline solution into said condenser zone into contact with said vapor stream, to react with said carbon dioxide to form a carbonate and remove said carbon dioxide from said vapor stream;
(c) condensing said working fluid;
and, (d) passing said condensed working fluid having a reduced content of carbon dioxide into heat exchange relation with said geothermal fluid.

1 more element

In a process for recovering energy from a geothermal fluid comprising geothermal brine and an uncondensible gas including CO.sub.2, the process including;

introducing said geothermal fluid into a heat exchange column through an inlet section in direct heat exchange relation with an immiscible working fluid in liquid form, expanding the resulting heated working fluid to produce work, condensing the expanded working fluid in a condenser, returning the condensed working fluid to said heat exchange column;
and withdrawing cooled geothermal fluid containing working fluid and uncondensible gas including CO.sub.2 from said heat exchange column and flashing said cooled geothermal fluid to flash off a mixture of working fluid vapor and uncondensible gas including CO.sub.2 ;
the improvement for removal of CO.sub.2 from said uncondensible gas which comprises:
(a) introducing said mixture into a second condenser, to condense said working fluid,
(b) introducing an aqueous alkaline earth metal hydroxide solution into said second condenser into contact with said working fluid and said uncondensible gas including CO.sub.2, to react with at least some of the CO.sub.2 to form an alkaline earth metal carbonate and remove said CO.sub.2 from said working fluid,
(c) returning said condensed working fluid from (a) to said heat exchange column, and
(d) venting the uncondensible gas from said second condenser.

4 more elements

A system for recovery of energy from a geothermal fluid including geothermal brine including in combination,

(a) a heat exchange column for direct contact heat exchange between said hot geothermal fluid and an immiscible hydrocarbon working fluid, (b) expander means for expanding the resulting heating working fluid to produce work,
(c) a first condenser means for condensing expanded working fluid, (d) an accumulator for separating working fluid and condensed water vapor,
(e) means for withdrawing working fluid from said accumulator,
(f) pumping means for pumping said withdrawn working fluid up to the pressure of said heat exchange column,
(g) means for introducing said pumped working fluid into said heat exchange column,
(h) means for withdrawing geothermal fluid containing working fluid and uncondensible gas including carbon dioxide from said heat exchange column,
(i)means for settling said withdrawn geothermal fluid to separate working fluid therefrom,
(j) means for returning said working fluid to said heat exchange column,
(k) a second work expander,
(l) means for feeding said geothermal fluid from said settling means to said second expander,
(m) flash drum means,
(n) means for introducing said expanded geothermal fluid from said second expander to said flash drum means,
(o) a contact condenser,
(p) means for introducing the flashed mixture of working fluid and uncondensible gas including CO.sub.2 into said contact condenser, to condense said working fluid therein,
(q) means for introducing a calcium hydroxide solution into said contact condenser and into contact with said working fluid and uncondensible gas including CO.sub.2, to thereby react with said CO.sub.2 to form calcium carbonate and removing said CO.sub.2 from said working fluid, and
(r) means for passing said working fluid from said contact condenser to said accumulator.

13 more elements

Dependencies are inferred from the claim text.

Removal of carbon dioxide in geothermal power systems

Life of this patent

Removal of carbon dioxide in geothermal power systems

Life of this patent

Abstract

Claims14