4 GTH Seminar Geothermal Power Plants

7/24/2019 4 GTH Seminar Geothermal Power Plants

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Seminar on Geothermal Exploitation Santiago de Chile20/06/2011 1

Geothermal Power Plants

Single flash systems Binary systems


Contents

Power Plants

Steam Power plants

Binary Power plants

Equipment

Well head

Gathering piping system

Steam separators and moisture separators

Turbine generators

Condensers

NCG gas removal systems

Cooling Towers


Single flash power cycle


Simplified single-flash backpressure schematic

2

53

4

1

Separator


Simplified single-flash condensing schematic

2

5

3

4

1

5

6

CWSeparator


TS - Diagram for steam


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Single flash process- Working cycle


One of the Design Objective

To produce as much energy as possible

from each kg geothermal fluid we extractfrom the geothermal reservoir

Example:

Let us assume that we know the reservoirenthalpy

We know the condensing temperature,

We need to estimate the separationtemperature and pressure that gives usmaximum energy


Backpressure, an alternative


Example


Silica Solubility


Silica Solubility


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Binary Power Plants


Basics for binary Power Plants

Uses similar principle as conventional

fossil or nuclear plants.

Instead of water/steam the working fluidis Propane, i or n-Butane, i or n Pentane,Ammonia or refrigerants with boiling pointmuch lower than water at same pressure.

Paratunka 1967, 670 kW

First indirect plant in Larerello 1912, 250kW with water/water cycle


Simple schematic and pressure-enthalpy diagram


Various Cycles


Hybrid, flash and Binary


Single flash + Binary


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Geothermal Steam Turbines


Single flow, top exhaust, impulse turbine


Types of steam turbines

Imulse turbine

The turbine change the direction of flowof a high velocity steam jet. The resultingimpulse spins the turbine and leaves thesteam with diminished kinetic energy.There is no pressure change of the steamin the turbine moving blades. All thepressure drop takes place in thestationary blades.

Reaction turbine

These turbines develop torque by reactingto the steam pressure or mass. The

pressure of the steam changes as itpasses through the turbine rotor blades.The turbine must be fully immersed in thefluid flow (such as with wind turbines).The casing contains and directs thesteam, maintains the suction imparted bythe draft tube.


Double flow, top exhaust reaction turbine


Single flow, multy pressure, top exhaust turbine


The Condenser


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Direct condenser


Shell and Tube Condenser


The Gas extraction systems


Non+condensable gases

In geothermal steam there will always be sometraces of non condensable gases.

The amount is usually in the range of 0-3% ofthe separated steam flow.

In some cases up to 20%

Since the gas in non-condensable this gas mustbe sucked out of the condensers, otherwise it willsimply build up there, blocking the heat exchangebetween the cooling water and the steam

There are several methods to remove the gases


Methods of removing NCG

Steam ejectors, SE

Two stages with intercondenser and sometimesand aftercondenser

Liquid ring vacuum pumps, LRVP

Hybrid systems

One stages Steam ejector + LRVP

Two stages Steam ejector + LRVP

Compressors


Steam Ejector

The pressure energy in the operating steam is converted intokinetic energy in the nozzle and this high velocity of the steamentrains the gas being pumped. The resulting mixture at theresulting velocity enters the diffuser where this veloc ityenergy is converted to pressure energy so that the pressure ofthe mixture at the ejector discharge is substantially higherthan the pressure in the suction chamber but lower than thepressure of the motive steam.


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Steam Ejector Velocity and Pressure


Liquid Ring Vacuum Pump

The compression is performed by a rotating ring of liquid,usually water, as the impeller rotates in eccentric positionrelative to the pump casing, the sealing liquid flows againstthe casing by the centrifugal force and the sealing liquidcirculating flow is made, as the impel ler is in an eccentricposition a decreasing cavity is produced inside the pump. Thiscavity becomes smaller since the inside face of sealing liquidcirculating flow gradually approaches the discharge port andcompressesthe gas in the inside


Compressor


Two stage Steam Ejector


Hybrid, Steam ejector + LRVP


Two stage ejector system


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Air leakage and dissolved air in cooling water

Estimated air leakage into the low pressure part

Flanges

Seals

Due to sub-atmospheric pressure in condensers

Dissolved air in cooling water

Must be taken into account if the condenser is cooleddirectly


Cooling


Cooling

Rivers, lakes or seawater

Cooling with air

Cooling tower

Traditionally used for a flash cycle

Air Cooler

Often used for binary cycle


Cooling tower


Cooling tower Schematic

Schematic drawing of a wet cooling tower


Unit 6 - Cooling Tower and CW-Pumps


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Example Reykjanes Power Plant


Reykjanes Power Plant


Reykjanes 50 MW Single flash - 3 units


Reykjanes - Steam separator station


Reykjanes - Brine exhaust silencers


Reykjanes - 50 MW steam turbine

Double flowDouble exhaust

Cross over Duct

CW In/out

Condenser

Generator

Control valve

Steam strainer

Main stop valve

Steam traps

and drain pipes


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Reykjanes - Sea water cooling


Example Svartsengi Power Plant


Why construct a power plant so close to the pool?


Svartsengi - Overview

High Pressure

dry steam area,Steam Cap

Re-injectionpipeline

CosmeticsProduction

BlueLagoon Power Plant

MedicalClinic

Water dominatedarea


Svartsengi - Formation of the steam cap

Geothermal well

Steam cap


Svartsengi - Steam cap area and collecting pipes


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Svartsengi Resource Park - Schematic


Svartsengi Power Plant (2009)


Svartsengi, Unit 5 - Turbine / Generator


Svartsengi, Unit 5 - Condenser


Svartsengi, Unit 5 - Water heaters


Svartsengi, Unit 5 - Gas Removal system


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Svartsengi, Unit 5 - Cooling Tower


Svartsengi, Unit 6. T/G - Moisture removal vessels


Svartsengi, Unit 6- Piping

Cross Over Duct

MP Outlet

LP Inlet

MP Inlet

HP control valve

HP main stop valve

HP steam strainer

Oil Unit

HP=High pressure, 16 baraMP=Medium press. 6,5-6,7 bara

LP=Low pressure, 1,2 bara





Cross Over DuctNCG Extraction

Condenser domeVAC tank connectionDrain from ejector syst.

CW Outlet

CW from aux systemsCW Inlet


Unit 6 - Cooling Tower and CW-Pumps


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Unit 6, Cooling Tower - Winter conditions


Example - Binary Power Plant


Binary Power Plant - Azores


Sao Miguel Azores - Pico Vermelho Plant


Pico Vermehlo - 10 MW PFD


10 MW binary Power Plant - Plan View


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Typical well pad

Well head, steam separator, brine tank, rock muffler andgathering pipelines


Well head and safety equipment

Safety valve with a rupture diskassembly on upstream side

Well head, master valve and branch valve


Separator and brine tank

Brine tank and brine pups

Vertical steam separator


Typical well pad

Well head, steam separator, brine tank, rock muffler andgathering pipelines


Brine pumps


Condensers, vaporizer and preheaters


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Turbine (s) and generator


Reinjection pumps

4 GTH Seminar Geothermal Power Plants

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