Puigjaner L. (ed.) Syngas from Waste

Подождите немного. Документ загружается.

Global Clean Gas Process Synthesis and Optimisation ............ 227

Mar Pérez-Fortes and Aarón D. Bojarski

Selection of Best Designs for Speciﬁc Applications ............... 253

Aarón D. Bojarski and Mar Pérez-Fortes

Examples of Industrial Applications.......................... 277

Pilar Coca, Mar Pérez-Fortes and Aarón D. Bojarski

Industrial Data Collection ................................. 299

Aarón D. Bojarski, Carlos Rodrigo Alvarez Medina, Mar Pérez-Fortes

and Pilar Coca

Index ................................................ 323

x Contents

Contributors

R. Álvarez-Rodríguez ETSI Minas, Alenza 4, 28003 Madrid, Spain

M. Bogataj Faculty of Chemistry and Chemical Engineering, University of

Maribor, Smetanova ulica 17, 2000 Maribor, Slovenia

A. D. Bojarski Universitat Politècnica de Catalunya, ETSEIB, Diagonal 647,

08028 Barcelona, Spain

C. Clemente-Jul Alenza 4, 28003 Madrid, Spain

P. Coca ELCOGAS, S. A.Ctra. Calzada de Calatrava a Puertollano, Km. 27,

Apdo. Correos 200, Puertollano—(Ciudad Real) 13500, Spain

A. Di Donato Centro Sviluppo Materiali, S.p.A., Via di Castel Romano, 100,

00128 Rome, Italy

Z. Kravanja Faculty of Chemistry and Chemical Engineering, University of

Maribor, Smetanova ulica 17, 2000 Maribor, Slovenia

J. M. Laínez Universitat Politècnica de Catalunya, ETSEIB, Diagonal 647, 08028

Barcelona, Spain

C. R. A. Medina Universitat Politècnica de Catalunya, ETSEIB, Diagonal 647,

08028 Barcelona, Spain

J. M. Nougués Universitat Politècnica de Catalunya, ETSEIB, Diagonal 647,

08028 Barcelona, Spain

M. Pérez-Fortes Universitat Politècnica de Catalunya, ETSEIB, Diagonal 647,

08028 Barcelona, Spain

C. Pevida Instituto Nacional del Carbón (CSIC), Apartado 73, 33080 Oviedo,

Spain

J. J. Pis Instituto Nacional del Carbón (CSIC), Apartado 73, 33080 Oviedo, Spain

L. Puigjaner Universitat Politècnica de Catalunya, ETSEIB, Diagonal 647, 08028

Barcelona, Spain

F. Rubiera Instituto Nacional del Carbón (CSIC), Apartado 73, 33080 Oviedo,

Spain

A. Soršak Javni zdravstveni zavod Mariborske lekarne Maribor, Minarikova ulica

6, 2000 Maribor, Slovenia

xii Contributors

Introduction

Luis Puigjaner

Abstract This chapter brieﬂy introduces the main components that play a role in

syngas production technologies. First, the thermochemical principles underlying

the syngas production process are enunciated. Second, the suitable raw materials

for gasiﬁcation, the products obtained, and their end uses are identiﬁed. Third, the

advantages, opportunities, present commercial status, and future perspectives of

gasiﬁcation are discussed. Finally, the need for enhanced technologies supported

by the development of an appropriate framework for a robust design and opti-

mization is justiﬁed. These issues are covered in detail in this book and should

prove useful for assessing current technologies, conveying novel concepts and

providing the basis for the future technological advancement of sustainable clean

syngas production at a competitive advantage.

Notation

BGC British Gas Corporation

CCS Carbon Capture and Storage

ERG Eastern Research Group

IGCC Integrated Gasiﬁcation Combined Cycle

MSW Municipal Solid Waste

1 Thermochemical Principles

Gasiﬁcation is a thermal process that converts a combustible material or residual

into gas through partial oxidation at elevated temperatures. A solid is normally

converted into a moderate heating value gas consisting of hydrogen and carbon

L. Puigjaner (&)

ETSEIB, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Spain

e-mail: Luis.puigjaner@upc.edu

L. Puigjaner (ed.), Syngas from Waste, Green Energy and Technology,

DOI: 10.1007/978-0-85729-540-8_1, Ó Springer-Verlag London Limited 2011

monoxide in varying ratios. The gasiﬁcation agent can be air, oxygen, and/or

steam.

Air gasiﬁcation produces a gas with a poor higher-heating value in the range of

4–7 MJ/Nm

(950–1,600 kcal/Nm

), which can be burned in a steam generator, an

internal combustion engine, or a steam turbine to create plants with an integrated

gasiﬁcation combined cycle (IGCC). It is not usually economical when used at a

distance from the gasiﬁer because of the higher cost of transportation. Gasiﬁcation

with oxygen produces a higher-quality gas with a higher-heating value in the range

of 10–18 MJ/Nm

(2,400–4,300 kcal/Nm

). In this case, limited transportation is a

possibility and it can even be used as a raw material for the synthesis of organic

compounds, such as methanol or gasoline.

The process of biomass or organic waste gasiﬁcation has three stages: drying

(evaporation of moisture contained in the solid), pyrolysis (thermal decomposition

in the absence of oxygen), and gasiﬁcation (partial oxidation of pyrolysis

products).

Pyrolysis occurs when a solid fuel is heated to temperatures between 300 and

500°C without an oxidizing agent. The products of pyrolysis are coal, condensable

hydrocarbons or tar, and gases. The relative proportions of different products

depend largely on the heating rate and ﬁnal temperature. In general, pyrolysis is

much faster than gasiﬁcation, so the latter stage controls the speed of the process.

Gas, liquid, and coal produced by pyrolysis react with the oxidant (usually air) and

generate permanent gases (CO, CO

, and H

) and smaller quantities of hydro-

carbons and oleﬁns. The gasiﬁcation of coal pyrolysis is the interactive combi-

nation of various gas–solid and gas–gas reactions, which oxidizes and becomes

carbon monoxide and carbon dioxide, and hydrogen is produced by the shift

reaction between the gas and water. Gas–solid reactions are slower and limit the

speed of the process. The ﬁnal composition of the gas depends on many factors,

such as the composition of feed, water content, reaction temperature (between 600

and 1,100°C), and the degree of oxidation of pyrolysis products [1, 2].

When the products of pyrolysis are not completely converted into gas, tar

contaminants appear. These contaminants, which are more likely to occur in

biomass gasiﬁcation than in coal, are difﬁcult to remove by means of thermal,

catalytic, or physical processes. Several research teams are therefore working on

ways to overcome this problem by cracking or removing the tars.

2 Raw Materials and Products

Raw materials with high carbon content (coal, petcoke, biomass, and organic

waste) are considered suitable for gasiﬁcation. The last two are especially relevant

to make the syngas production process an economically competitive alternative

source of energy. Biomass is widely considered the greatest potential fuel for

energy in the future. As an energy source, could represent 50% of total energy

demand in Europe, using biomass crop speciﬁc ﬁeld unnecessary for food, and also

2 L. Puigjaner

considering other wastes and residues from agriculture, trade, and consumers.

Biomass can be classiﬁed by origin as follows [3, 4]:

(a) Agriculture includes a wide range of ligno-cellulosic materials generated by

the food industry.

(b) Forestry includes wood from forest clearing, logging, and other wood-

processing industries.

in large quantities and often include paper, cardboard, and wood (all with a

high heating value).

(d) Municipal solid waste can be gasiﬁed after glass and metal are removed.

(e) Mix includes sewage sludge and wood from the construction and demolition of

buildings. Although it has a high carbon content, sewage sludge poses serious

difﬁculties related to high moisture content, high ash content, and the presence

of heavy metals. The wood from demolished buildings can also contain sig-

niﬁcant amounts of heavy metals.

A classic way of characterizing these types of solids is by immediate analysis

(moisture, ﬁxed carbon, volatiles, and ash) and elemental analysis (C, O, N, H, and

S) from which the material balance and scope of certain environmental effects can

be set.

The most common processes of transformation of biomass for further use of

fuel in electricity generation or cogeneration are thermal combustion, gasiﬁcation,

and pyrolysis (Fig. 1). Of the three processes described for the assessment of

biomass energy, gasiﬁcation is one that involves more advantages [5, 6]:

(i) First, the volume of gases produced in gasiﬁcation is much lower and with

lower concentrations of pollutants; thus, cleaning systems are smaller and

operate more efﬁciently.

(ii) Second, with the gasiﬁcation yields a fuel that can be used in a wide variety

of applications with conventional equipment designed for fuel gases appro-

priately tailored so that it can be transported to a distance from the site of

generation.

(iii) Third, if the goal is to produce electricity and steam, the overall thermody-

namic efﬁciency by using a synthetic gas that expands in heat engines after

combustion and uses the excess energy in the hot gases to produce steam is

much higher for gasiﬁcation than in combustion.

(iv) Finally, gasiﬁcation is much more developed than pyrolysis-level industrial

operation, and both equipment design and the operation are simpler for the

case of the gasiﬁcation.

From an energy point of view, the main feature that differentiates gasiﬁcation

from combustion is that although all the energy of the gas is in the form of sensible

heat during combustion, part of the chemical energy contained in the feedstock is

transferred to the gas during gasiﬁcation. However, not all the energy is used as

Introduction 3

gas-heating value: There is a gasiﬁcation performance that depends on the type of

gasiﬁer and the oxidizing agent [7].

The main reason for requiring a certain gasiﬁcation performance is that the

above process (drying ? pyrolysis ? gasiﬁcation) is endothermic, which means

that it is necessary to provide energy. This can be done in two ways: through an

external source or through the combustion of a portion of the gasiﬁed solid. The

latter alternative, which is most often used industrially, requires careful control of

the solid–air (or oxygen) ratio. In this case, a series of endothermic and exothermic

reactions occurs within the gasiﬁer. If the process is handled properly (at constant

temperature), the heat generated by the exothermic reactions (combustion) com-

pensates for the heat absorbed by endothermic reactions. Then, the process is

referred to as ‘‘autothermal’’ [8, 9].

The gas obtained contains carbon monoxide (CO), carbon dioxide (CO

hydrogen (H

), methane (CH

), small amounts of other heavier hydrocarbons, such

as ethane (C

) and ethylene (C

), water (H

O), nitrogen (N

) (when using air

as oxidant), and several contaminants, such as small carbonaceous particles, ash,

tars, and oils. Partial oxidation can be carried out using air, oxygen, steam, or a

Fig. 1 Schematic of waste treatment and recycling of biomass/organic waste

4 L. Puigjaner

mixture of these elements. CO and H

confer heating value to the gas and they may

react with oxygen (combustion in a boiler, engine, or turbine). CO

and H

O are

undesirable but unavoidable products. Although it is often formed in small

proportions, methane is responsible for much of the energy content of gas.

The gas composition depends on the composition of the gasiﬁed solid, the

gasiﬁer operating conditions, and the design of the gasiﬁer.

3 Opportunities and Future Prospects

Compared with other technologies, gasiﬁcation has many positive attributes that

help to stimulate its market. It is the only technology that offers both ﬂexibility and

advantages in terms of feed kinds and product uses. All raw materials containing

carbon, including hazardous waste, municipal solid waste, sewage sludge, and

biomass, can gasify after pretreatment to produce clean synthesis gas that can then

be processed. Because of this ability to use low-cost raw materials, gasiﬁcation

technology is most suitable for many industrial applications, such as those used in

reﬁneries [10].

Compared with combustion systems, gasiﬁcation is more efﬁcient and causes

less environmental impact to produce low-cost electricity from solid materials and

gets even closer to the production of electricity from combined-cycle natural gas.

Greater efﬁciency is achieved when it is integrated with the use of fuel cells and

other advanced technologies. Increased efﬁciency in electricity production reduces

operating costs and produces less carbon dioxide. In addition, the gasiﬁcation

process can be adapted to incorporate advanced technologies for CO

concentra-

tion with a reduced impact on cost and thermal efﬁciency. This feature is one of

the most important factors for selecting this technology in future power plants.

Moreover, the products of gasiﬁcation are much easier to clean than those of

combustion, thereby reducing emissions of sulfur and nitrogen oxides. In general,

the volume of gas-processed fuel in an IGCC plant to be cleaned is usually a third

of that which would correspond to a conventional power plant. This reduces the

cost of equipment to prevent contamination. It is also much easier to remove

sulfur, nitrogen, and other pollutants from reducing gas leaving the gasiﬁer than

from combustion gases. This in turn affects the emissions of sulfur and nitrogen

oxides, which are lower than those that correspond to conventional combustion

processes. If necessary, gasiﬁcation plants can also be conﬁgured to achieve zero

emissions.

Unlike the combustion process, the ash and slag produced as a by-product of

gasiﬁcation are not dangerous. Therefore, ash can be deposited in landﬁlls without

any additional treatment costs, used as building materials, or further processed for

value-added products, leading to a zero-discharge plant (nonproduction of solid

waste).

The aforementioned features provide good prospects for gasiﬁcation in an

environment marked by greater competitiveness in the electricity market, by

Introduction 5

increasingly stringent regulations regarding emissions of sulfur, nitrogen oxides,

air pollutants, and other particles, and by treaties to reduce emissions of green-

house gases. To be competitive and choose the most appropriate technology in this

frame of reference, Stiegel and Maxwell [5] at the US Department of Energy point

out that technologies entering the market should have a thermal efﬁciency greater

than 60% and investment costs less than US$1,000/kWe; issue little or no sulfur

and nitrogen oxides, other air pollutants, and particulate matter; use noncarbon

sources; produce a wide range of specialty products; and capture and sequester

carbon dioxide. Of all the advanced technologies being developed, gasiﬁcation-

based technologies are the only ones that have the potential to meet these objec-

tives with production costs at or less than current market costs.

4 Commercial Status

In the late twentieth century, gasiﬁcation was deployed widely throughout the

world. In 1999, there were 128 plants with 366 gasiﬁers in operation. Most of these

facilities were in Western Europe, the Eastern Paciﬁc, Africa, and North America.

Combined, these plants generated 42,000 MW of synthesis gas. In the 1999–2003

period, there were plans to build 33 plants with 48 additional gasiﬁers, which adds

another 18,000 MW of capacity to produce synthesis gas. Most of these plants

belong to Asian countries, which need to expand electricity production because of

economic development [11].

At present, the main raw materials used in gasiﬁcation plants are coal and

petroleum residues, which account for more than 70% of the synthesis gas pro-

duced, followed by natural gas, which accounts for about 20%. In the latter case,

natural gas is only used as a raw material for chemicals. In the coming years, growth

can be expected in the use of low-grade coal, petroleum residues, and other waste.

In the current market situation of power generation, gasiﬁcation cannot compete

with combined-cycle natural gas because of the high investment costs and low

price of natural gas. The low costs of fossil fuels or waste materials that can be

gasiﬁed, compared with the cost of natural gas, are not sufﬁcient in most scenarios

to achieve the return on capital investment in the gasiﬁcation plant. An acceptable

return is only possible when the raw material cost is very low, the local cost of

natural gas is high, high added-value products are obtained, or improved tech-

nology is integrated into existing systems [12, 13].

The Värnamo plant in Sweden is an example of a successful exploitation. In the

United States, there is a limited number of biomass gasiﬁcation projects that receive

government support, and most are in a demonstration phase. A recent study [12]

shows that 50 manufacturers from Europe, the United States, and Canada market

gasiﬁcation technologies, 75% of which are moving-bed or ﬁxed-bed designs

(Lurgi, Wellmann Galusha, Woodall Duckham, Merc, Riley Morgan, Willputte,

Wellmann, FW Stoic, BGC Lurgi, etc.) and 20% are ﬂuidized bed systems

(Winkler, CO

acceptor, Hygas, Synthane, Cogas, Eron, Batelle Union Carbide,

6 L. Puigjaner

Westinghouse, U Gas, etc.) or entrained bed systems (Koppers Totzek, Shell-

Koppers, Texaco, Ruhrgas, Combustion Engineering, Foster Wheeler, and Babcock

& Wilcox).

5 Future Development

Considerable activity is underway to develop biomass gasiﬁcation for efﬁcient and

environmentally acceptable energy conversion applications, as evidenced by the

status of efforts made in several countries to generate clean power [14]. However,

an underlying framework is required for the conceptual design of Emerging

Technologies for the Generation and Conditioning of Syngas From Waste.This

framework should be useful not only for assessing current technologies but also for

incorporating novel concepts and being open to future advancements.

Such a framework should encompass a detailed treatment of the following

technical and operational issues:

(a) New processes for the pretreatment of biomass wastes, through the modiﬁca-

tion of their properties prior to gasiﬁcation, so as to make them more attractive

for their subsequent use (see chapter Raw Materials, Selection, Preparation

and Characterization).

(b) Efﬁcient energy supply chains from biomass: design and planning of efﬁcient

multiple source—multiple product bioenergy supply chains (see chapter Raw

Materials Supply).

plants considering the enlargement of the fuel panorama (see chapter

Modelling Syngas Generation).

(d) Conditioning and gas cleaning of synthesis gas from biomass and other waste

types requiring speciﬁc treatments for commercial use, including removal

of tars, particulates, alkali, ammonia, chlorine, and sulfur (see chapter

Main Puriﬁcation Operations).

(e) Process intensiﬁcation: development of high-temperature puriﬁcation pro-

cesses that avoid or reduce the loss in performance employing ‘‘important

value’’ adsorbents (see chapter Emerging Technologies on Syngas Puriﬁcation:

Process Intensiﬁcation).

(f) Implementation of innovative CO

Capture and Storage (CCS) technologies

increasing CO

uptake and improving H

and CO

separation, as well as

promoting process intensiﬁcation and avoiding energy intensive options

(see chapter H

production and CO

separation).

(g) Process systems engineering approach to integrated conceptual design of

syngas process networks leading to the ﬂexible and versatile representation of

all possible ﬂowsheets for its production from different raw materials

using different processing units by means of a process superstructure.This

superstructure would be subsequently optimized (see chapter Modelling

Superstructure for Conceptual Design of Syngas Generation and Treatment).

Introduction 7

Puigjaner L. (ed.) Syngas from Waste - Emerging Technologies

Подождите немного. Документ загружается.