Operations of a Downdraft Gasifier on MSW for Development of a Waste to Energy Process

Andrew Lucero, John West, Kevin McCabe, Patrick Woolcock, and Santosh Gangwal

Presentation for AIChE 2013 Annual Meeting

Nov. 3-8, 2013

Agenda

• Southern Research Institute

• Micro-Thermochemical Platform Concept

• Concept System Advantages and R&D Focus Areas

• Initial Operations with MSW

• Analysis

• Future work

• Established in 1941 as an independent, not-for-profit (501-c-3) center for scientific research and development

• Headquartered in Birmingham, Alabama

• Environment & Energy Department in Durham, NC

• Revenues of Approx. $80 million in 2012

• Staff of over 500 employees

• Mission: Southern Research is an innovative research organization serving the life sciences, engineering, energy, and environmental protection industries. We pursue entrepreneurial and collaborative initiatives to develop and maintain a pipeline of intellectual property and innovative technologies that contribute to the growth of the organization and positively impact real-world problems.

Southern Research Institute

Southern Research Micro-Thermochemical Platform

• $4M committed by Southern Research for pilot development

• Green electrical power, biofuels, hot water, cooling, biochar

• Small distributed plants (1-200 tpd) – Reduced feedstock requirements and logistics

– Reduced transportation distances and associated diesel use

– Reduced capital cost and permitting requirements

– Direct marketing of products in plant vicinity

– Economic development for rural and under-developed areas

Modular Integrated System

Concept System Advantages and R&D Focus Areas

• Feedstock Preparation – Minimal sorting, no pelletization, low-cost drying

• Gasifier – Simple, inexpensive, commercially proven and scalable (1 to 50 tpd)

downdraft system

– Agreement with manufacturer for development of fully integrated systems by Southern Research

– High efficiency and extremely low tar

– Handles wide variety and sizes of very low to high density feeds

– Automated char removal system accommodates clinker formation up to 1 inch

• Syngas cleanup – Novel dry syngas cleaning system does not produce any liquid waste

• Fischer-Tropsch synthesis – Novel selective catalyst maximizes liquids (C5-C20) and produces no wax

Preliminary Economic Analysis

• Estimated Capital Cost

– 27 ton/day MSW to power: $ 5.8 Million

– 200 ton/day wood waste to fuel: $ 37.2 Million

• Preliminary analysis shows

– MSW to power plant payback period <4 years

– Waste to fuel plant moderately profitable without incentives • 25 % down payment, 15 year loan; 7 % interest rate

• Internal rate of return = 11.2 %

• Plant becomes highly profitable with any incentives

• Economic analysis to be further refined (Data!!)

Justification for Small-Scale Distributed Gasification-Based Systems

• Relatively large scale MSW and biomass gasification systems in development by several companies – Gasifiers complex (fluidized-beds, molten metal, plasma, entrained-bed) and

unsuccessfully commercialized at these scales (politics, cheap coal/land)

– Very large financial investments and associated risks

– Feedstock logistics and land area requirements

– Several other roadblocks in getting projects off the ground

• Advantages of small-scale distributed plants – Obvious environmental benefits (vs. open pit burning, burying, etc.)

– Reduced feedstock requirements and logistics

– Reduced transportation distances and associated diesel use

– Reduced capital cost and permitting requirements

– Potential for direct marketing of products in plant vicinity

– Economic uplift of rural and under-developed areas

• Economy of scale needs to be addressed

Stratified Downdraft Gasifier

• Biomass and air are fed through the top of the gasifier.

• The air to fuel ratio is maintained to ensure an oxygen deficient atmosphere in the reduction zone.

• Syngas is removed by vacuum pressure through the exit pipe.

• Smaller char particles pass through the grate and are removed from the bottom of the gasifier.

Source: Martinez J.D., et al. Syngas production in downdraft biomass gasifiers and its application using internal combustion engines. Renewable Energy 2012; 38: 1-9.

3 Ton/Day Pilot Plant Under Operation

• Gasification trials have recently commenced • Feed stocks to include wood, several agricultural wastes, animal waste, RDF, and MSW • Feed preparation method, dry syngas cleanup system and catalyst development proceeding in parallel

Simulated MSW Feedstock

Weight (tons) Weight (%)

Cardboard 3.0 11

Paper 6.4 25

PET 0.7 3

HDPE 0.4 2

Residue 4.2 16

Food Waste 5.8 22

Textiles (half of Furniture here) 3.2 12

Wood (half of Furniture here) 2.3 9

Total 26.0 100

Feedstock Preparations

• Procure materials from various recyclers

• Shred as close as possible to gasifier specifications

• Adjust moisture content as necessary

• Characterize for CHNOS and Cl

Experimental

Plans

• Vary air flow rate (air to fuel ratio)

• Vary char withdrawal rate (affects both residence time and air to fuel ratio)

• Vary feed moisture composition

Outputs

• Syngas composition and rate

• Char composition and rate

• Material and energy balances (efficiency)

Syngas Composition 9/24/2012 9/25/2012 9/26/2012 9/27/2012 9/28/2012 AVERAGE

Hydrogen 14.77 14.12 13.03 13.27 14.15 13.9

Oxygen 0.32 0.33 0.45 0.42 0.53 0.41

Nitrogen 52.43 53.51 55.54 54.34 53.37 53.8

Methane 1.93 1.91 1.62 1.75 1.80 1.8

CO 15.59 15.35 12.81 13.02 13.11 14.0

CO2 13.22 13.39 14.08 14.10 14.13 13.8

Ethylene 0.63 0.65 0.57 0.64 0.59 0.62

Ethane 0.10 0.10 0.09 0.11 0.10 0.1

Propane 0.02 0.03 0.02 0.04 0.03 0.028

Moisture 12.29 9.55 11.85 9.61 8.76 10.4

Target Syngas Composition: CO - 19±3%, H2 -18±2%, CO2 - 8±3%, CH4 -Up to 3%, N2 - 50%.

Typical Temperature Profiles During Operation

Operational Issues

• Channeling through gasifier likely resulted in non stratified operation

• Potential contributing factors – Density

– Particle size

– Moisture

• Potential solutions – Parametric tests of feed parameters

– Gasifier modifications?

Path forward

• Additional instrumentation to improve characterization of flows, temperatures, and compositions in more parts of the system

• Upgrades for heat tracing and insulation to improve cold efficiency

• Potential tests with Imbert gasifier using pelletized MSW to develop a baseline for system operations

• Continued development for gas cleanup and Fischer-Tropsch for integrated system.

Questions?