Anaerobic Digester GTL Integration for Heat Recovery
Solution Overview
Problem
Anaerobic digesters lack a reliable source of heat input, limiting the efficiency of the bioconversion process and producing low-value electricity as the primary product, rather than more valuable products.
Innovation Solution
An anaerobic digester system that includes a steam reformer to convert methane and water into syngas, followed by a gas-to-liquid process to produce methanol, dimethyl ether, and other hydrocarbons, with excess heat from the GTL process being reused to accelerate biomass digestion and reduce capital and operating costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a typical digester is used to produce electricity, then electricity can be generated from digester gas, but the product value remains low without tax or government incentives
Solution Approach 1:
The patent transforms the digester gas product through a series of chemical process parameter changes: first converting methane to syngas (changing composition), then converting syngas to liquid hydrocarbons (changing phase and composition). This sequence of parameter changes converts low-value gas into high-value liquid fuels, directly resolving the contradiction between product quantity/value and product versatility.
Solution Approach 2:
The patent introduces syngas as an intermediary substance between the digester gas and final liquid fuel products. The syngas conversion process acts as a mediator that enables the transformation from methane-rich gas to diverse liquid hydrocarbon products, thereby increasing both product value and versatility without requiring direct modification of the digester itself.
2Productivity
If heat input is provided to maximize the rate of conversion, then the bioconversion efficiency increases, but the system lacks a ready source of heat input
Solution Approach 1:
The patent implements a feedback loop where liquid fuel products are combusted to generate heat, and this heat is fed back to the digester to maintain optimal conversion temperatures. This closed-loop feedback system ensures continuous high-rate conversion by automatically providing the necessary thermal energy from the system's own output, resolving the heat source availability problem.
Solution Approach 2:
The system is designed to be self-sufficient by using a portion of its own liquid fuel products as the heat source for the digester. This self-service approach eliminates the need for external heat inputs, allowing the system to maintain high conversion rates using only its own outputs, thereby resolving the contradiction between productivity and energy input requirements.
3Quantity of substance
If the GTL process is used to produce valuable liquid products, then product value increases, but the system requires additional heat management infrastructure
Solution Approach 1:
The patent merges the heat generation function with the liquid fuel combustion step. Instead of separating heat generation and product utilization, the system combines them by using the liquid fuel products themselves as the heat source. This merging eliminates the need for separate heat management infrastructure, as the combustion chamber serves dual purposes: producing heat for the digester and utilizing the liquid fuel products.
Solution Approach 2:
The liquid fuel combustion system is designed to serve multiple functions simultaneously: it generates heat for the digester, utilizes the liquid fuel products, and maintains system temperature. This multi-functionality reduces the need for dedicated heat management equipment, resolving the contradiction between product value and device complexity by making the same infrastructure serve multiple purposes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach increases the thermal and carbon efficiency of the bioconversion process, producing more valuable products than electricity and reducing the need for additional heat sources, thereby enhancing the overall economic viability of the system.
Implementation Method 1
a syngas process to convert the gas mixture to a product mixture comprising carbon monoxide and hydrogen... the syngas process is a steam reformer, which can convert methane and water into a mixture of carbon monoxide and hydrogen
Implementation Method 2
a gas-to-liquid reactor or series of reactors that converts the carbon monoxide and hydrogen to a product such as methanol, dimethyl ether (DME), formalin, formaldehyde, low molecular weight hydrocarbons
Implementation Method 3
All or part of the excess heat from the GTL process is transferred to the anaerobic digester, and as a result, the rate at which the biomass is digested will be faster than if the heat is not transferred to the digester
Implementation Method 4
an anaerobic digester, which produces a mixture of methane and carbon dioxide gases... Anaerobic digestion refers to converting organic materials (generally wastes) into useful byproducts by processes, such as fermentation, involving living organisms
Data Source
AI summary
A combined anaerobic digester system and gas-to-liquid system is disclosed. The anaerobic digester requires heat, and produces methane. The gas-to-liquid system produces heat, and converts methane to higher-value products, including methanol and formaldehyde. As such, the combination of the two systems results in significant savings in terms of capital and operating expenses. A process for producing bio-formaldehyde and bio-formalin from biogas is also disclosed.