Production of Syngas From Biomass and

Its Purification

(University of Engineering and technology, Lahore)

Presentation Focous onUNDER THE SUPERVISION

Sir Muhammad Asif Akhtar

PRESENTERS

M. Awais Yaqoob 2011-ch-32

Rizwan Liaquat 2011-ch-72

Nanad Lal 2011-ch-146

SYNOPSIS

IntroductionFeasibility & market

assessmentLiterature Survey

Process Selection & Description

Equipment ListEnvironmental ConsiderationsP&ID Diagram

Conclusion & Recommendations

Introduction

Motivation of the Project

Reduce green house effect

Establish new and secure

energy source

Availability of the raw material

Energy Crises in Pakitan

Basic Chemistry

CnHmOk + (n-k) H20 → nCO + (n + m/2 – k)H2

Above reaction is followed by this reaction

nCO + NH2O → nCO2 + nH2

So the overall process is

CnHmOk + (2n-k) H20 → nCO2 + (2n + m/2 – k)H2

Background and Objectives

Oil & Gas reserves are decreasing

Environmental friendly

Less CO2 emission

Sustainable

Advantages of Syngas

syngas

Synthetic products & fuels

Less carbon

emissions

methanol

Produce H2 & hence NH3

Origin of Fertilizer

Fuel for spacecraft rockets

Availability of Raw Material• Present in large amount here in Pakistan• 55000 tons of solid waste is generated by

urban area. • 225000 tones in the form of crop residue, and

almost 1million ton of animal wastage.• Main contributors of this biomass are rice straw,

bagasse, cotton waste, maize stalks, and husk.• Only sugar mills produce around 30-32 million

tons of bagasse per year.

Worldwide Production• fossil fuels are the primarily source of energy

consumption all over the world. • But biomass consumption will reach about 1

million tons by 2021.• Demand of biomass would get triple by 2030.

Plant Capacity• Power plants having capacities b/w 3 MW to

7MW are the most economical.• 3-7 MW has efficiency of 20-25% for which

requirement of energy is

3.6MG/0.25 = 14.4 MJ

enough to generate 1kWh electricity. • Figures clearly shows how much data is

needed to support a 5MW plant

Literature Survey

• At high temperature and pressure with steam and oxygen produces syngas.

• This syngas has • 85% CO• Hydrogen• Small amounts of CO2 and CH4

• temperature is an important parameter for controlling the H2/CO ratio.

Cont…,

Fluidized

bed gasifier Biom

ass feeder

Steam generator

Air

compressor

Cyclone

catalyt

ic fix

ed

bed reacto

r

Different routes for Syngas Production

From Biomass derived oil

From Biomass derived char

From reforming of biomass gasification gas

From biomass

Effect of varying Temperature and Weight hourly space velocity

(WHSV) on Syngas production

Effect of Temperature

• By varying temperature and keeping the operating conditions constant,

• H2 content in the syngas increases with temperature due to endothermic reaction involved.

• Decrease the CH4 content because of the steam reforming reaction.

• The CO content first decreases, and then increases.

• the H2/CO ratio first increase and then it decreases as temperature is elevated.

• consequently it reaches a maximum value of 4.45 as the temperature is at 7500C.

Cond…

By increasing the temperature reaction

A­­­­→­D occurs simultaneously asCO + H2O → CO2 + H2 ∆H = 411 KJ/mol

CH4 + H2O → CO + 3H2 ∆H = -206 KJ/mol

C + H2O → CO + H2 ∆H = -131 KJ/mol

C + CO2 → 2CO ∆H = -172 KJ/mol

The H2/CO ratio changes between 3.11 & 4.45 as shown in table

Weight Hourly Space Velocity (WHSV)

• WHSV is the ratio of the biomass flow rate which is fed to the reactor and the mass of catalyst in the reactor.

• The content increases with an increase in residence time. • while that of CO and CH4 decrease by doing so.

• applying catalyst increases the H2 content more favorably.

• The ratio of H2/CO increase with increase in residence time

• H2/CO value at 7000C and 8000C lies b/w 2.11 and 3.32

• The H2/CO ratio is low at 8000C than at 7000C because• water gas shift reaction being exothermic• Shift reaction decreases the CO consumption and

transformation rate and hence lowers the H2/CO ratio.

Particulate matter

• Particle matters emitted from a gasifier are of the range of 1µm to 100µm.

• Inorganic compounds and gasification of biomass includes bulk of particulate matter and consist of alkali metals, silica, alkaline earth metals, iron and magnesium.

• More than 99% removal of particulate are required as direct combustion process requires particulate reduction up to 50 mg m-3

• Removing these particulates fouling, corrosion and erosion

Tars

• Mixture of condensable organic compounds. • Thermochemical species produces hundred to

thousand tar species according to operating parameters.

• Gasification of wood results in higher tar concentrations having higher amounts of stable aromatics in comparison to peat or coal.

• Tar has complex nature and it creates difficulties in analyzing, collecting

Sulphur• They mostly occur as hydrogen sulfide.• Sulphur contaminants in concentration may range from 0.1

Ml L-1 to 30 Ml L-1.• Biomass has less Sulphur amount than coal.• Biomass contains only 0.1 g/kg to 0.5 g/kg Sulphur

compared to 50 g/kg as obtained from coal.• If syngas is supposed to burned, Sulphur is oxidized to

Sulphur dioxide which is a regulated pollutant.• To avoid these effects, often removal in parts per billion is

dioxide which is a regulated pollutant.• More than 30 technologies have been formed to remove

Sulphur compounds including CO2. Recent hot gas removal research is focused which uses dry sorbents.

Nitrogen Compounds• Usually occur as ammonia and hydrogen cyanide.• Pyrolysis stage and combustion usually release

nitrogen from protein or heterocyclic aromatic compounds.

• Ammonia is pure form of nitrogen and it can be formed directly from biomass and from HCN using secondary gas phase reactions.

Process Selection

And

Description

Fermentation Pyrolysis

Gasification

Process Selection

Why We Selected Gasification Process

• Gasification process is the most favorable because

» High conversion of biomass» Its utilization for useful products» 90% of biomass is converted to the desired products

or energy

Process Description

• The biomass is firstly pulverized to fine particles and is necessarily dried.

• It is dried at high temperature of 300° C in a non-oxidant environment and for an effective residence time resulting in 90 wt. % removal of the moisture and a first vapor phase gas stream is produced.

• Then it is sent to Gasifier.• Gasifier works at high pressure (3.45 MPa) and

temperature of 800 to 900° C.• This gasifier requires superheated steam for the required

heat effect. • Flow of oxygen and steam required for this process is

0.3 and 0.4 kg/kg of dry biomass

Cond…

• The reaction produces syngas which contains some contaminants like chlorides, sulfides and alkalis.

• The ash formed is recovered from the bottom of the gasifier.

• Hot gasses with product gases and char are transferred to the cyclone where char is separated from bottom

Cond…

• In gasifier cross sectional area

at the lower part is smaller• It results in a high gas velocity

zone at the bottom.• Despite the unequal particle size

distribution large particles are kept

inside the gasifier until the reaction

achieves the pseudo steady state is

achieved.

Purification

of

Syngas

Purification

Cool gas cleanup

technology

Warm gas cleanup

technology

Hot gas cleanup

technology

Hot gas cleanup technology• Cleanup method depends on the end use of the syngas.• Cool gas cleanup technology is less favored due to energy

inefficiencies• Hot gas cleanup technology is preferred

because they avoid the reheating and the cooling of the gas streams.

• It has temperature of T > 3000C• It focuses on the removal of tar and particulate matter with the

aim of minimizing the maintenance of the equipment.

Sulphur Removal

• Sulphur removal focuses on the removal SO2 & H2O.

• Mostly HGC technologies use adsorption where gaseous species combine chemically or physically with the solid materials.

• Doping is another technique in which ZnO and other sorbents with CuO to ensure low Sulphur concentrations

Nitrogen Removal

• It is done by decomposition of ammonia rather than removing ammonia from gas streams.

• Oxidation of gas streams which contains ammonia leads to the destruction of NH3 into H2 & N2 and NO.

4NH3 + 6NO → 5N2 + 6H2O 5H2 + 2NO → 2NH3 + 2H2O

Alkali Removal

• At elevated temp, two process are commonly used to reduce alkali concentrations

» Removal via condensations with other contaminants» Hot adsorption onto the solid adsorbents

• Sorbents include the natural minerals i.e. silicon, kaolinite or clays.

• Some sorbents like SiO2 and Al2O3 based minerals are able to remove both chlorine and alkali from gas at temp approaching 8000C

Chlorine Removal

• Chlorine is mostly found in biomass.• A substantial portion of the chlorine

evolves as HCl.• In Hot Gas Cleanup a sorbent is employed

that remove HCl only and sometimes also the alkali metals.

• HCl removed is more efficient b/w 500-5500C.

Summary

Summary of hot gas particulate clean up technology

Equipment List

• Pulverizer• Gasifier• Cyclone• Dryer• Compressor• Heat exchanger• Scrubber• catalytic Reformer• Tar reformer

• Fluidized bed reactor• Steam generator• Feed tank• Adsorber• Pump

Environmental Considerations

• Biomass fuels "recycle" atmospheric carbon• Sources of biomass resources for producing

electricity are diverse including agricultural waste, manure, forest products and waste, and urban waste.

• There are global warming emissions associated with growing and harvesting biomass feedstock.

• Burning biomass to produce electricity can impact air quality.

The Piping and Instrumentation Diagram

Conclusion & Recommendations

• Gasified biomass is a versatile supplement to a primarily fossil-based energy infrastructure

• It provides an alternative renewable source of chemicals and fuels for a growing populace.

• Syngas must therefore be relatively purified of the contaminants.

• Methods for Syngas production may provide gains in thermal efficiency, process simplicity and the potential for cost reduction using generable sorbents.

• All processess overcoming activity losses and increasing sorbent lifetime remains challenging.